[S-3ASR] ALUMIS INC. SEC Filing

Filing Impact

(Neutral)

Filing Sentiment

(Neutral)

Form Type

S-3ASR

Rhea-AI Filing Summary

Alumis Inc. files a shelf registration statement to permit future offerings of multiple security types. The filing registers an indeterminate number of common stock, preferred stock, debt securities and warrants under a base prospectus and a $300.0 million sales agreement with Cantor Fitzgerald & Co. dated March 18, 2026, permitting sales of voting common stock from time to time after effectiveness.

The base prospectus covers various mechanisms and convertible issuance paths; specific terms, amounts, offering prices and proceeds treatment will be disclosed in future prospectus supplements.

Insights

Registers an open-ended shelf plus a $300.0 million at-the-market sales agreement.

The filing establishes a broad Form S-3 shelf that permits the issuance or resale of common stock, preferred stock, debt and warrants, and includes a sales agreement prospectus for up to $300.0 million of voting common stock under a Controlled Equity Sales Agreement with Cantor Fitzgerald & Co. dated March 18, 2026.

The operative mechanics, including dilution, timing and proceeds recipients, will be set forth in future prospectus supplements; the shelf and sales agreement create flexibility to access equity capital markets after the registration statement becomes effective.

Sales agreement provides an at-the-market route for incremental equity placement.

The sales agreement prospectus specifically authorizes offerings of voting common stock up to an aggregate offering price of $300.0 million, to be sold from time to time after effectiveness. The base prospectus covers additional instruments and conversion features that may permit issuance of equity upon conversion or exercise.

Practical considerations include market conditions and prospectus supplements that will specify pricing mechanics, plan of distribution and whether the company or selling holders receive proceeds.

03/19/2026 - 05:02 PM

TABLE OF CONTENTS

As filed with the Securities and Exchange Commission on March 19, 2026

Registration No. 333-

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM S-3

REGISTRATION STATEMENT

UNDER
THE SECURITIES ACT OF 1933

ALUMIS INC.
(Exact name of registrant as specified in its charter)

	Delaware			82-1771129
	(State or other jurisdiction of incorporation or organization)			(I.R.S. Employer Identification Number)

Alumis Inc.
280 East Grand Avenue
South San Francisco, California 94080
(650) 231-6625

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Martin Babler
President and Chief Executive Officer
Alumis Inc.
280 East Grand Avenue
South San Francisco, CA 94080
(650) 231-6625

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Kristin VanderPas
Dave Peinsipp
Chadwick L. Mills
Cooley LLP
3 Embarcadero Center, 20th Floor
San Francisco, CA 94111
(415) 693-2000

John Schroer
Chief Financial Officer
Alumis Inc.
280 East Grand Avenue
South San Francisco, CA 94080
(650) 231-6625

Approximate date of commencement of proposed sale to the public: From time to time after the effective date of this Registration Statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box: ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, as amended, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box: ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box. ☒

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer	☐	Accelerated filer	☐
Non-accelerated filer	☒	Smaller reporting company	☒
		Emerging growth company	☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

TABLE OF CONTENTS

EXPLANATORY NOTE

This registration statement contains two prospectuses:

•

a base prospectus which covers the offering, issuance and sale of an indeterminate number of the registrant’s voting common stock, preferred stock, debt securities and/or warrants; and

•

a sales agreement prospectus covering the offering, issuance and sale by the registrant of up to a maximum aggregate offering price of $300.0 million of shares of the registrant’s voting common stock that may be offered, issued and sold from time to time under a Controlled Equity OfferingSM Sales Agreement (the “Sales Agreement”), dated March 18, 2026, with Cantor Fitzgerald & Co., as sales agent.

The base prospectus immediately follows this explanatory note. The specific terms of any securities to be offered pursuant to the base prospectus, will be specified in one or more prospectus supplements to the base prospectus. The prospectus relating to the Sales Agreement immediately follows the base prospectus.

TABLE OF CONTENTS

Prospectus

COMMON STOCK
PREFERRED STOCK
DEBT SECURITIES
WARRANTS

From time to time, we or selling securityholders may offer and sell any combination of the securities described in this prospectus in one or more offerings, either individually or in combination with other securities. We or selling securityholders may also offer common stock or preferred stock upon conversion of debt securities, common stock upon conversion of preferred stock, or common stock, preferred stock or debt securities upon the exercise of warrants.

This prospectus provides a general description of the securities we or selling securityholders may offer. Each time we or selling securityholders offer securities, we will provide the specific terms of these offerings and the securities offered in one or more supplements to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. The prospectus supplement and any related free writing prospectuses may also add, update or change information contained in this prospectus. You should carefully read this prospectus, the applicable prospectus supplement and any related free writing prospectuses, as well as any documents incorporated by reference, before buying any of the securities being offered.

We have two classes of common stock: the voting common stock we or selling securityholders may offer and sell under this prospectus and the applicable prospectus supplement and non-voting common stock. Only voting common stock will be offered and sold under this prospectus and the applicable prospectus supplement, and unless otherwise noted, all references in this prospectus to our “common stock,” “common shares” or “shares” refer to our voting common stock.

Our common stock is listed on The Nasdaq Global Select Market under the trading symbol “ALMS.” On March 18, 2026, the last reported sale price of our common stock was $25.42 per share. The applicable prospectus supplement will contain information, where applicable, as to other listings, if any, on The Nasdaq Global Select Market or other securities exchange of the securities covered by the applicable prospectus supplement.

This prospectus may not be used to consummate any sale of securities unless accompanied by a prospectus supplement.

We or selling securityholders may sell these securities directly to investors, through agents designated from time to time or to or through underwriters or dealers, or through a combination of these methods, on a continuous or delayed basis. The supplements to this prospectus will provide the specific terms of the plan of distribution. If any agents, underwriters or dealers are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such agents, underwriters or dealers and any applicable fees, commissions, discounts and options to purchase additional securities will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement. Unless the applicable prospectus supplement provides otherwise, we will not receive any proceeds from the sale of securities by selling securityholders. For additional information, please refer to the sections titled “About this Prospectus” and “Plan of Distribution” in this prospectus.

We are an “emerging growth company” and a “smaller reporting company” as defined under the U.S. federal securities laws and, as such, may elect to comply with certain reduced public company reporting requirements. See the section titled “Prospectus Summary — Implications of Being an Emerging Growth Company and a Smaller Reporting Company.”

Investing in our securities involves a high degree of risk. Before making an investment decision, you should review carefully the risks and uncertainties described in the section titled “Risk Factors” contained in the applicable prospectus supplement and in any free writing prospectuses we have authorized for use in connection with a specific offering, and under similar headings in the documents that are incorporated by reference into this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is March 19, 2026.

TABLE OF CONTENTS

	Page
ABOUT THIS PROSPECTUS		ii
PROSPECTUS SUMMARY		1
RISK FACTORS		6
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		7
USE OF PROCEEDS		9
DESCRIPTION OF CAPITAL STOCK		10
DESCRIPTION OF DEBT SECURITIES		15
DESCRIPTION OF WARRANTS		22
LEGAL OWNERSHIP OF SECURITIES		24
SELLING SECURITYHOLDERS		27
PLAN OF DISTRIBUTION		28
LEGAL MATTERS		31
EXPERTS		31
WHERE YOU CAN FIND ADDITIONAL INFORMATION		31
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		32

TABLE OF CONTENTS

ABOUT THIS PROSPECTUS

This prospectus provides you with a general description of the securities we or selling securityholders may offer. Each time we or selling securityholders offer securities under this prospectus, we will provide a prospectus supplement that will contain more specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement and any related free writing prospectuses that we may authorize to be provided to you may also add, update or change any of the information contained in this prospectus or in the documents that we have incorporated by reference into this prospectus. We urge you to read carefully this prospectus, any applicable prospectus supplement and any free writing prospectuses we have authorized for use in connection with a specific offering, together with the information incorporated herein by reference as described in the section titled “Incorporation of Certain Information by Reference,” before buying any of the securities being offered.

This prospectus may not be used to consummate a sale of securities unless it is accompanied by a prospectus supplement.

We have not authorized any other person to provide you with any information or to make any representations other than those contained in, or incorporated by reference into, this prospectus, any related prospectus supplement and any free writing prospectuses prepared by or on behalf of us or to which we have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. You should assume that the information appearing in this prospectus, any related prospectus supplement and the documents incorporated by reference into this prospectus, any related prospectus supplement and in any free writing prospectuses that we may authorize for use in connection with this offering, is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus, any related prospectus supplement, the documents incorporated by reference into this prospectus and any free writing prospectuses that we may authorize for use in connection with this offering, in their entirety before making an investment decision. You should also read and consider the information in the documents to which we have referred you in the sections of this prospectus titled “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.”

This prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. The distribution of this prospectus and any related prospectus supplement or free writing prospectuses and the offering of our securities in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus and any related prospectus supplement or free writing prospectuses must inform themselves about, and observe any restrictions relating to, the offering of our securities and the distribution of this prospectus and any related prospectus supplement outside the United States. This prospectus and any related prospectus supplement or free writing prospectuses does not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus and any related prospectus supplement by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

We obtained the industry and market data in this prospectus, including the information incorporated by reference herein, from our own research as well as from industry and general publications, surveys and studies conducted by third parties. These data involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. In addition, projections, assumptions and estimates of our future performance and the future performance of the industry in which we operate is necessarily subject to a high degree of uncertainty and risk due to a variety of factors, including those described in “Risk

TABLE OF CONTENTS

Factors” and elsewhere in this prospectus, any related prospectus supplement, the documents incorporated by reference into this prospectus and any related or free writing prospectuses. These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties and by us.

This prospectus and any related prospectus supplement, including the information incorporated by reference into this prospectus and any related prospectus supplement, include trademarks, service marks and trade names owned by us or others. All trademarks, service marks and trade names included or incorporated by reference in this prospectus, any related prospectus supplement or any related free writing prospectuses are the property of their respective owners.

This prospectus and the information incorporated herein by reference contain summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or will be incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described in the sections titled “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.”

iii

TABLE OF CONTENTS

PROSPECTUS SUMMARY

This summary highlights selected information contained elsewhere in this prospectus or incorporated by reference in this prospectus, and does not contain all of the information that you need to consider in making your investment decision. You should carefully read the entire prospectus, the applicable prospectus supplement and any related free writing prospectus, including the risks of investing in our securities discussed under the heading “Risk Factors” contained in the applicable prospectus supplement and any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference into this prospectus. You should also carefully read the information incorporated by reference into this prospectus, including our financial statements, and the exhibits to the registration statement of which this prospectus is a part.

Unless the context requires otherwise, references in this prospectus to “Alumis,” the “Company,” “we,” “us” and “our” refer to Alumis Inc. and its wholly owned subsidiary.

The Company

Our mission is to significantly improve the lives of patients by replacing broad immunosuppression with targeted therapies. Our name, Alumis, captures our mission to enlighten immunology, and is inspired by the words “allumer” — French for illuminate — and “immunis” — Latin for the immune system.

We are a clinical stage biopharmaceutical company with an initial focus on developing our two Tyrosine Kinase 2 (“TYK2”) inhibitors: envudeucitinib (“envu”), formerly known as ESK-001, a second-generation inhibitor that we are developing to maximize target inhibition and optimize tolerability, and A-005, a central nervous system (“CNS”) penetrant allosteric TYK2 inhibitor. Envu is currently being evaluated in an ongoing Phase 2 open-label extension trial, as well as a Phase 3 long-term extension trial in patients with moderate-to-severe plaque psoriasis (“PsO”), and we plan to submit a New Drug Application (“NDA”) for envu in PsO to the FDA in the second half of 2026. Envu completed enrollment in the pivotal Phase 3 ONWARD1 and ONWARD2 clinical trials in patients with PsO, and we reported positive topline results in the first quarter of 2026. In addition, envu is currently being evaluated in a Phase 2 clinical trial in patients with systemic lupus erythematosus (“SLE”), for which we expect to report topline results in the third quarter of 2026. We are currently evaluating additional immune-mediated disease indications for envu, beyond PsO and SLE, and for A-005 in CNS and peripheral diseases. In April 2024, we initiated our Phase 1 program of A-005 in healthy volunteers and reported initial results in December 2024. In addition, in connection with the ACELYRIN Merger (as defined below), we acquired lonigutamab, a subcutaneously delivered, monoclonal antibody targeting IGF-1R for the potential treatment of Thyroid Eye Disease. We are continuing to evaluate the development program for lonigutamab and its potential differentiation in a capital efficient manner.

We utilize our proprietary precision data analytics platform, biological insights and team of experienced research and development experts to deepen our understanding of disease pathologies, accelerate research and development and increase the probability of clinical success. Our collective insights informed our selection of TYK2 as the target for our two lead programs. Beyond TYK2, our proprietary precision data analytics platform and drug discovery expertise have led to the identification of additional preclinical programs that exemplify our precision approach.

We recognize that patients living with immune-mediated diseases need alternatives to currently available therapies. Despite recent advances and innovations in the treatment of immune-mediated diseases, many patients continue to suffer, cycling through currently approved therapies while looking for a solution that alleviates the debilitating impact of their disease without life-limiting side effects.

Addressing the needs of these patients is why we exist. We are pioneering a precision approach that leverages insights derived from powerful data analytics to select the right target, right molecule, right indication, right patient, right endpoint and right combination to dramatically improve patient outcomes. We believe that combining our insights with an integrated approach to drug development will produce the next generation of treatments to address immune dysfunction.

Corporate Information

Alumis was incubated by Foresite Labs, LLC (“Foresite Labs”) and incorporated on January 29, 2021 as a Delaware corporation under the name FL2021-001, Inc. FL2021-001, Inc.’s name was changed to Esker

TABLE OF CONTENTS

Therapeutics, Inc. in March 2021 and to Alumis Inc. in January 2022. Our principal executive offices are located at 280 East Grand Avenue, South San Francisco, California 94080, and our telephone number is (650) 231-6625. Our website address is www.alumis.com. Information contained in, or accessible through, our website is not a part of this prospectus, and the inclusion of our website address in this prospectus is only an inactive textual reference.

Implications of Being an Emerging Growth Company and a Smaller Reporting Company

We are an “emerging growth company,” as defined in Section 2(a) of the Securities Act, as modified by the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), and we may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies, including:

•

being permitted to present only two years of audited financial statements, in addition to any required unaudited interim financial statements, with correspondingly reduced “Management’s Discussion and Analysis of Financial Condition and Results of Operations” disclosure in this prospectus;

•

relief from the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act of 2002, as amended;

•

relief from compliance with the requirements of the Public Company Accounting Oversight Board regarding the communication of critical audit matters in the auditor’s report on the financial statements;

•

less extensive disclosure obligations regarding executive compensation in our registration statements, periodic reports and proxy statements;

•

exemptions from the requirements to hold a nonbinding advisory vote on executive compensation; and

•

exemptions from stockholder approval of any golden parachute payments not previously approved.

We may also elect to take advantage of other reduced reporting requirements in future filings. As a result, our stockholders may not have access to certain information that they may deem important and the information that we provide to our stockholders may be different than, and not comparable to, information presented by other public reporting companies. We could remain an emerging growth company until the earlier of (i) the last day of the fiscal year following the fifth anniversary of the closing of our initial public offering, (ii) the last day of the fiscal year in which we have total annual gross revenue of at least $1.235 billion, (iii) the last day of the fiscal year in which we are deemed to be a “large accelerated filer” as defined in Rule 12b-2 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), which would occur if the market value of our common stock and non-voting common stock held by non-affiliates exceeded $700.0 million as of the last business day of the second fiscal quarter of such year or (iv) the date on which we have issued more than $1.0 billion in non-convertible debt securities during the prior three-year period.

In addition, the JOBS Act provides that an emerging growth company may take advantage of the extended transition period provided in the Securities Act for complying with new or revised accounting standards. An emerging growth company may therefore delay the adoption of certain accounting standards until those standards would otherwise apply to private companies. We have elected to avail ourselves of this exemption and, as a result, will not be subject to the same implementation timing for new or revised accounting standards as are required of other public companies that are not emerging growth companies, which may make comparison of our consolidated financial information to those of other public companies more difficult.

We are also a “smaller reporting company,” as defined in the Exchange Act. We will continue to be a smaller reporting company even after we cease to be an emerging growth company, as long as (i) the market value of our common stock and non-voting common stock held by non-affiliates is less than $250.0 million measured on the last business day of our second fiscal quarter or (ii) our annual revenue is less than $100.0 million during the most recently completed fiscal year and the market value of our common stock and non-voting common stock held by non-affiliates is less than $700.0 million measured on the last business day of our second fiscal quarter. If we are a smaller reporting company at the time we cease to be an

TABLE OF CONTENTS

emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies. Specifically, as a smaller reporting company, we may choose to present only the two most recent fiscal years of audited financial statements in our Annual Report on Form 10-K and, similar to emerging growth companies, smaller reporting companies have reduced disclosure obligations regarding executive compensation.

The Securities We May Offer

We or selling securityholders may offer shares of our common stock and preferred stock, various series of debt securities and/or warrants to purchase any of such securities, either individually or in combination, from time to time under this prospectus, together with the applicable prospectus supplement and any related free writing prospectuses, at prices and on terms to be determined by market conditions at the time of any offering. We or selling securityholders may also offer common stock, preferred stock and/or debt securities upon the exercise of warrants. There is no limit on the aggregate amount of the securities that we or selling securityholders may offer pursuant to the registration statement of which this prospectus is a part. This prospectus provides you with a general description of the securities we or selling securityholders may offer. Each time we or selling securityholders offer a type or series of securities under this prospectus, we will provide a prospectus supplement that will describe the specific amounts, prices and other important terms of the securities, including, to the extent applicable:

•

designation or classification;

•

aggregate principal amount or aggregate offering price;

•

maturity date, if applicable;

•

original issue discount, if any;

•

rates and times of payment of interest or dividends, if any;

•

redemption, conversion, exercise, exchange or sinking fund terms, if any;

•

conversion or exchange prices or rates, if any, and, if applicable, any provisions for changes to or adjustments in the conversion or exchange prices or rates and in the securities or other property receivable upon conversion or exchange;

•

ranking, if applicable;

•

restrictive covenants, if any;

•

voting or other rights, if any; and

•

material or special U.S. federal income tax considerations, if any.

The applicable prospectus supplement and any related free writing prospectuses that we may authorize to be provided to you may also add, update or change any of the information contained in this prospectus or in the documents we have incorporated by reference. However, no prospectus supplement or free writing prospectuses will offer a security that is not registered and described in this prospectus at the time of the effectiveness of the registration statement of which this prospectus is a part.

THIS PROSPECTUS MAY NOT BE USED TO CONSUMMATE A SALE OF SECURITIES UNLESS IT IS ACCOMPANIED BY A PROSPECTUS SUPPLEMENT.

We or selling securityholders may sell the securities directly to investors or to or through agents, underwriters or dealers. We and our agents, underwriters or dealers, reserve the right to accept or reject all or part of any proposed purchase of securities. If we or selling securityholders do offer securities to or through agents, underwriters or dealers, we will include in the applicable prospectus supplement:

•

the names of those agents, underwriters or dealers;

•

applicable fees, discounts and commissions to be paid to them;

•

details regarding over-allotment options, if any; and

•

the estimated net proceeds to us.

TABLE OF CONTENTS

Common Stock. We or selling securityholders may sell shares of our common stock from time to time. The holders of our common stock are entitled to one vote for each share held of record on all matters submitted to a vote of stockholders. Additionally, holders of our common stock have no conversion rights. Subject to preferences that may apply to any shares of preferred stock outstanding at the time, the holders of our common stock are entitled to receive dividends out of funds legally available if our board of directors, in its discretion, determines to issue dividends and then only at the times and in the amounts that our board of directors may determine. On our liquidation, dissolution, or winding-up, the holders of common stock will be entitled to share equally, identically, and ratably in all assets remaining after the payment of any liabilities, liquidation preferences and accrued or declared but unpaid dividends, if any, with respect to any outstanding preferred stock, unless a different treatment is approved by the affirmative vote of the holders of a majority of the outstanding shares of such affected class, voting separately as a class. The holders of our shares of common stock are not entitled to preemptive rights, and are not subject to redemption or sinking fund provisions. The rights, preferences and privileges of the holders of our common stock or non-voting common stock are subject to, and may be adversely affected by, the right of the holders of shares of any series of preferred stock that we may designate in the future. In this prospectus, we have summarized certain general features of the common stock under the section titled “Description of Capital Stock — Common Stock and Non-Voting Common Stock.” We urge you, however, to read the applicable prospectus supplement (and any related free writing prospectuses that we may authorize to be provided to you) related to any common stock being offered.

Preferred Stock. We or selling securityholders may sell shares of our preferred stock from time to time, in one or more series. Our board of directors will have the authority, without further action by our stockholders, to issue up to 50,000,000 shares of preferred stock in one or more series, to establish from time to time the number of shares to be included in each such series, to fix the dividend, voting and other rights, preferences and privileges of the shares of each wholly unissued series and any qualifications, limitations or restrictions thereon, and to increase or decrease the number of shares of any such series, but not below the number of shares of such series then outstanding. Convertible preferred stock will be convertible into our common stock or exchangeable for other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

If we or selling securityholders sell any series of preferred stock under this prospectus as supplemented by a prospectus supplement, and if applicable, free writing prospectus, we will fix the designations, voting powers, preferences and rights of the preferred stock of each series we issue under this prospectus, as well as the qualifications, limitations or restrictions thereof, in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that contains the terms of the series of preferred stock we or selling securityholders are offering. In this prospectus, we have summarized certain general features of the preferred stock under the section titled “Description of Capital Stock — Preferred Stock.” We urge you, however, to read the applicable prospectus supplement (and any related free writing prospectuses that we may authorize to be provided to you) related to the series of preferred stock being offered, as well as the complete certificate of designation that contains the terms of the applicable series of preferred stock.

Debt Securities. We may sell debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. The senior debt securities will rank equally with any other unsecured and unsubordinated debt. The subordinated debt securities will be subordinate and junior in right of payment, to the extent and in the manner described in the instrument governing the debt, to all of our senior indebtedness. Convertible debt securities will be convertible into or exchangeable for our common stock or other securities. Conversion may be mandatory or at the holder’s option and would be at prescribed conversion rates.

Any debt securities issued under this prospectus will be issued under one or more documents called indentures, which are contracts between us and a national banking association or other eligible party, as trustee. In this prospectus, we have summarized certain general features of the debt securities in the section titled “Description of Debt Securities.” We urge you, however, to read the applicable prospectus supplement (and any free writing prospectuses that we may authorize to be provided to you) related to the series of debt securities being offered, as well as the complete indentures that contain the terms of the debt securities.

TABLE OF CONTENTS

We have filed the form of indenture as an exhibit to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

Warrants. We or selling securityholders may sell warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. We may issue warrants independently or in combination with common stock, preferred stock and/or debt securities, and the warrants may be attached to or separate from these securities. In this prospectus, we have summarized certain general features of the warrants in the section titled “Description of Warrants.” We urge you, however, to read the applicable prospectus supplement (and any related free writing prospectuses that we may authorize to be provided to you) related to the particular series of warrants being offered, as well as any warrant agreements and warrant certificates that contain the terms of the warrants. We have filed forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants that may be offered as exhibits to the registration statement of which this prospectus is a part. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of warrant and/or the warrant agreement and warrant certificate, as applicable, that contain the terms of the particular series of warrants we or selling securityholders are offering, and any supplemental agreements, before the issuance of such warrants.

Any warrants issued under this prospectus may be evidenced by warrant certificates. Warrants also may be issued under an applicable warrant agreement that we enter into with a warrant agent. We will indicate the name and address of the warrant agent, if applicable, in the prospectus supplement relating to the particular series of warrants being offered.

Selling Securityholders

Selling securityholders are persons or entities that, directly or indirectly, have acquired or will from time to time acquire from us, our securities. Information about selling securityholders, if any, will be set forth in a prospectus supplement. See the section titled “Selling Securityholders” on page 27 of this prospectus.

Use of Proceeds

We will retain broad discretion over the use of the net proceeds from the sale of the securities offered hereby. Except as described in any applicable prospectus supplement or in any free writing prospectuses we have authorized for use in connection with a specific offering, we currently intend to use the net proceeds from the sale of the securities offered by us hereunder, if any, primarily for general corporate purposes, including but not limited to, clinical trial expenses, research and development expenses, general and administrative expenses and capital expenditures, or for any other purpose we describe in the applicable prospectus supplement. See the section titled “Use of Proceeds” in this prospectus. Unless the applicable prospectus supplement provides otherwise, we will not receive any of the proceeds from the sale of our securities by selling securityholders.

Exchange Listing

Our common stock is listed on The Nasdaq Global Select Market (“Nasdaq”) under the symbol “ALMS.” The applicable prospectus supplement will contain information, where applicable, as to other listings, if any, on Nasdaq or other securities exchange of the securities covered by the applicable prospectus supplement.

TABLE OF CONTENTS

RISK FACTORS

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks and uncertainties described in the section titled “Risk Factors” contained in the applicable prospectus supplement and any related free writing prospectuses, and discussed under the section titled “Risk Factors” contained in our most recent Annual Report on Form 10-K and in our subsequent Quarterly Reports on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus in their entirety, together with other information in this prospectus, the documents incorporated by reference and any applicable prospectus supplement and free writing prospectuses that we may authorize for use in connection with this offering. The risks described in these documents are not the only ones we face, but those that we consider to be material. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have material adverse effects on our future results. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be seriously harmed. This could cause the trading price of our common stock to decline, resulting in a loss of all or part of your investment. Please also read carefully the section titled “Special Note Regarding Forward-Looking Statements” in this prospectus.

TABLE OF CONTENTS

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, each prospectus supplement and the information incorporated by reference in this prospectus and each prospectus supplement contain forward-looking statements within the meaning of Section 27A of the Securities Act, Section 21E of the Exchange Act, and the Private Securities Litigation Reform Act of 1995, as amended, that involve substantial risks and uncertainties.

These forward-looking statements are based on our management’s beliefs and assumptions and on information currently available to our management. All statements, other than statements of historical facts contained in this prospectus, the applicable prospectus supplement and the documents we have filed with the SEC that are incorporated by reference herein and therein, including statements regarding our future financial condition, business strategy and plans, and objectives of management for future operations, are forward-looking statements. Discussions containing these forward-looking statements may be found, among other places, in the section titled “Risk Factors” in this prospectus and any applicable prospectus supplement, as well as under the sections titled “Business,” “Risk Factors,” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” contained in the documents incorporated by reference herein and therein. In some cases, you can identify forward-looking statements by the following words: “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “ongoing,” “plan,” “potential,” “predict,” “project,” “should,” “will,” “would,” or the negative of these terms or other comparable terminology, although not all forward-looking statements contain these words.

These forward-looking statements involve risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from the information expressed or implied by these forward-looking statements. Although we believe that we have a reasonable basis for each forward-looking statement contained in this prospectus, the applicable prospectus supplement and the documents we have filed with the SEC that are incorporated by reference herein and therein, we caution you that these statements are based on a combination of facts and factors currently known by us and our projections of the future, about which we cannot be certain. Forward-looking statements in this prospectus, the applicable prospectus supplement and the documents we have filed with the SEC that are incorporated by reference herein and therein include, but are not limited to, statements about:

•

our plans to submit a New Drug Application for envu, formerly known as ESK-001, in PsO in the second half of 2026;

•

the potential for our product candidate envu to transform the treatment landscape for IL-23/IL-17 — driven diseases as well as those driven by Type I interferon;

•

the potential for envu to meaningfully elevate care for and effectively reduce the full burden of disease for patients with PsO;

•

the timing of our topline readout in our LUMUS Phase 2b trial;

•

our ability to obtain funding for our operations, including funding necessary to complete further development and any commercialization of our product candidates;

•

our expectations regarding the potential benefits of our strategy, including with respect to the integration of operations, technologies and personnel associated with our merger with ACELYRIN, Inc. (the “ACELYRIN Merger”);

•

our plans relating to the research and development of our product candidates;

•

developments related to our competitors and our industry, including the success of competing product candidates and therapies that are, or may become, available;

•

details regarding our strategic vision and planned product candidate pipeline;

•

our beliefs regarding the success, cost and timing of our product candidate development activities and current and future clinical trials and studies including study design;

•

the timing or likelihood of regulatory filings or other actions and related regulatory authority responses;

•

the ability and willingness of various third parties to engage in research and development activities involving our product candidates, and our ability to leverage those activities;

TABLE OF CONTENTS

•

our expectations regarding the potential benefits from any existing or future license or collaboration agreements, including the receipt of potential co-development, milestone and royalty payments;

•

our expectations regarding the ease of administration associated with our product candidates;

•

our expectations regarding the patient compatibility associated with our product candidates;

•

our beliefs regarding the potential markets for our product candidates and our ability to serve those markets;

•

our beliefs regarding the potential of our product candidates to demonstrate differentiation from other approved therapies or therapies in development;

•

the ability to obtain and, if approved, maintain regulatory approval of any of our product candidates, and any related restrictions, limitations and/or warnings in the label of any approved product candidate;

•

our ability to commercialize any approved products;

•

the rate and degree of market acceptance of any approved products;

•

our ability to attract and retain key personnel;

•

the accuracy of our estimates regarding our future revenue, as well as our future operating expenses, capital requirements and needs for additional financing;

•

our ability to obtain, maintain, protect and enforce intellectual property protection for our product candidates and technology and not infringe, misappropriate or otherwise violate the intellectual property of others;

•

regulatory developments in the United States and foreign countries;

•

our expectations regarding the period during which we qualify as an “emerging growth company” under the JOBS Act and a “smaller reporting company,” as defined in Rule 12b-2 of the Exchange Act;

•

our use of cash and other resources, including our expected use of proceeds from any offering under this prospectus; and

•

statements of belief and any statement of assumptions underlying any of the foregoing.

You should refer to the section titled “Risk Factors” included in this prospectus, the applicable prospectus supplement, in any free writing prospectuses we may authorize for use in connection with a specific offering, and in our most recent Annual Report on Form 10-K, and in our subsequent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus in their entirety, for a discussion of other important factors that may cause our actual results to differ materially from those expressed or implied by our forward-looking statements. As a result of these factors, we cannot assure you that the forward-looking statements in this prospectus, the applicable prospectus supplement and the documents we have filed with the SEC that are incorporated by reference herein and therein will prove to be accurate.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date the statement is made, and although we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted a thorough inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain, and investors are cautioned not to unduly rely upon these statements.

Furthermore, if our forward-looking statements prove to be inaccurate, the inaccuracy may be material. In light of the significant uncertainties in these forward-looking statements, you should not regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified time frame, or at all. We undertake no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

TABLE OF CONTENTS

USE OF PROCEEDS

Except as described in any prospectus supplement or in any related free writing prospectus that we may authorize to be provided to you in connection with a specific offering, we currently intend to use the net proceeds from the sale of securities under this prospectus primarily for general corporate purposes, including but not limited to, clinical trial expenses, research and development expenses, general and administrative expenses and capital expenditures. As of the date of this prospectus, we cannot specify with certainty all of the particular uses of the net proceeds, if any, from the sale of securities under this prospectus. Accordingly, we will retain broad discretion over the use of such proceeds. We will set forth in the applicable prospectus supplement or free writing prospectus our intended use of the net proceeds received from the sale of any securities sold pursuant to the prospectus supplement or free writing prospectus. Pending the use of the net proceeds as described above, we intend to invest the net proceeds in short-term, investment-grade, interest-bearing instruments.

Unless the applicable prospectus supplement provides otherwise, we will not receive any of the proceeds from the sale of our securities by selling securityholders.

TABLE OF CONTENTS

DESCRIPTION OF CAPITAL STOCK

The following description of our capital stock and certain provisions of our amended and restated certificate of incorporation, amended and restated bylaws and relevant provisions of Delaware General Corporation Law (“DGCL”) are summaries qualified in their entirety by our amended and restated certificate of incorporation and amended and restated bylaws, copies of which have been filed as exhibits to the registration statement of which this prospectus is part, as well as the relevant provisions of DGCL.

Our authorized capital stock consists of 492,815,092 shares of common stock, $0.0001 par value per share, 7,184,908 shares of non-voting common stock, $0.0001 par value per share, and 50,000,000 shares of preferred stock, $0.0001 par value per share.

Common Stock and Non-Voting Common Stock

Voting Rights and Conversion Rights

The holders of our common stock are entitled to one vote per share of common stock on any matter that is submitted to a vote of our stockholders, and holders of our non-voting common stock are not entitled to any votes per share of non-voting common stock, including for the election of directors. Additionally, holders of our common stock have no conversion rights, while holders of our non-voting common stock have the right to convert each share of our non-voting common stock into one share of common stock at such holder’s election, provided that as a result of such conversion, such holder, together with its affiliates and any members of a Schedule 13(d) group with such holder, would not beneficially own in excess of 4.99% of any class of our securities registered under the Exchange Act, unless otherwise as expressly provided for in our amended and restated certificate of incorporation. However, the beneficial ownership limitation may be increased to any other percentage designated by such holder of non-voting common stock upon 61 days’ notice to us or decreased at any time. Holders of our non-voting common stock are also permitted to make certain transfers of non-voting common stock to non-affiliates upon which, such transferred shares could be immediately converted into shares of our common stock. Shares of our non-voting common stock are not otherwise subject to automatic or mandatory conversion for any reason.

Our amended and restated certificate of incorporation does not provide for cumulative voting for the election of directors for our common stock. Our amended and restated certificate of incorporation establishes a classified board of directors that is divided into three classes with staggered three-year terms. Only the directors in one class will be subject to election by a plurality of the votes cast at each annual meeting of our stockholders holding shares of common stock, with the directors in the other classes continuing for the remainder of their respective three-year terms. The affirmative vote of holders of at least 662∕3% of the voting power of all of the then-outstanding shares of capital stock, voting as a single class, is required to amend certain provisions of our amended and restated certificate of incorporation, including provisions relating to amending our amended and restated bylaws, the classified structure of our board of directors, the size of our board of directors, removal of directors, director liability, vacancies on our board of directors, special meetings, stockholder notices, actions by written consent and exclusive jurisdiction.

Economic Rights

Except as otherwise expressly provided in our amended and restated certificate of incorporation or required by applicable law, and other than the voting rights and conversion rights stated above, all shares of common stock and non-voting common stock have the same rights and privileges and rank equally, share ratably, and are identical in all respects for all matters, including those described below.

Dividends. Subject to preferences that may apply to any shares of preferred stock outstanding at the time, the holders of our common stock and non-voting common stock are entitled to receive dividends out of funds legally available if our board of directors, in its discretion, determines to issue dividends and then only at the times and in the amounts that our board of directors may determine.

TABLE OF CONTENTS

Liquidation Rights. On our liquidation, dissolution, or winding-up, the holders of common stock and non-voting common stock will be entitled to share equally, identically, and ratably in all assets remaining after the payment of any liabilities, liquidation preferences and accrued or declared but unpaid dividends, if any, with respect to any outstanding preferred stock, unless a different treatment is approved by the affirmative vote of the holders of a majority of the outstanding shares of such affected class, voting separately as a class.

No Preemptive or Similar Rights

The holders of our shares of common stock and non-voting common stock are not entitled to preemptive rights, and are not subject to redemption or sinking fund provisions. The rights, preferences and privileges of the holders of our common stock or non-voting common stock are subject to, and may be adversely affected by, the right of the holders of shares of any series of preferred stock that we may designate in the future.

Fully Paid and Non-Assessable

When we issue shares of common stock under this prospectus, the shares will be fully paid and non-assessable.

Preferred Stock

Our board of directors has the authority, without further action by our stockholders, to issue up to 50,000,000 shares of preferred stock in one or more series, to establish from time to time the number of shares to be included in each such series, to fix the dividend, voting and other rights, preferences and privileges of the shares of each wholly unissued series and any qualifications, limitations or restrictions thereon, and to increase or decrease the number of shares of any such series, but not below the number of shares of such series then outstanding.

Our board of directors may authorize the issuance of preferred stock with voting or conversion rights that could adversely affect the voting power or other rights of the holders of our common stock and non-voting common stock. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions and other corporate purposes, could, among other things, have the effect of delaying, deferring or preventing a change in our control and may adversely affect the market price of our common stock and non-voting common stock and the voting and other rights of the holders of our common stock and non-voting common stock. We have no current plans to issue any shares of preferred stock.

Registration Rights

We are party to an amended and restated investors’ rights agreement that provides certain holders of shares of our common stock, including certain holders of at least 5% of our capital stock and entities affiliated with certain of our directors, are entitled to certain rights with respect to registration of such shares under the Securities Act, as set forth below. These shares are referred to as registrable securities. This amended and restated investors’ rights agreement was entered into in March 2024. The registration of shares of our common stock (including shares of common stock issuable upon conversion of non-voting common stock) pursuant to the exercise of the registration rights described below would enable the holders to trade these shares without restriction under the Securities Act when the applicable registration statement is declared effective. We will pay the registration expenses, other than underwriting discounts, selling commissions and stock transfer taxes, of the shares registered pursuant to the demand, piggyback and Form S-3 registrations described below.

Generally, in an underwritten offering, the managing underwriter, if any, has the right, subject to specified conditions and limitations, to limit the number of shares the holders may include. The demand, piggyback and Form S-3 registration rights described below will expire no later than three years after the closing of our initial public offering.

TABLE OF CONTENTS

Demand Registration Rights

The holders of the registrable securities are entitled to certain demand registration rights. The holders of 40% of these shares (or a lesser percent if the anticipated aggregate offering price, net of selling expenses, would exceed $20.0 million) may request that we register all or a portion of their shares. We are not required to effect more than one registration statement which is declared or ordered effective.

Piggyback Registration Rights

In connection with this offering, certain holders of our common stock were entitled to, and the necessary percentage of holders waived, their rights to notice of this offering and to include their shares of registrable securities in this offering. After this offering, in the event that we propose to register any of our securities under the Securities Act, either for our own account or for the account of other security holders, the holders of these shares will be entitled to certain piggyback registration rights allowing the holder to include their shares in such registration, subject to certain marketing and other limitations.

Form S-3 Registration Rights

The holders of the registrable securities are entitled to certain Form S-3 registration rights. Holders of 20% of these shares can make a request that we register their shares on Form S-3 if we are qualified to file a registration statement on Form S-3 and if the reasonably anticipated aggregate net proceeds of the shares offered would equal or exceed $3.0 million. We will not be required to effect more than two registrations on Form S-3 within any 12-month period.

Anti-Takeover Provisions

The provisions of Delaware law, our amended and restated certificate of incorporation and our amended and restated bylaws, which are summarized below, may have the effect of delaying, deferring or discouraging another person from acquiring control of our company. They are also designed, in part, to encourage persons seeking to acquire control of us to negotiate first with our board of directors. We believe that the benefits of increased protection of our potential ability to negotiate with an unfriendly or unsolicited acquirer outweigh the disadvantages of discouraging a proposal to acquire us because negotiation of these proposals could result in an improvement of their terms.

Certificate of Incorporation and Bylaws

Because our stockholders do not have cumulative voting rights, stockholders holding a majority of the voting power of our shares of common stock are able to elect all of our directors. Our amended and restated certificate of incorporation and our amended and restated bylaws provide for stockholder actions at a duly called meeting of stockholders or, before the date on which all shares of common stock convert into a single class, by written consent. A special meeting of stockholders may be called by a majority of our board of directors, the chair of our board of directors, or our chief executive officer or president. Our amended and restated bylaws include an advance notice procedure for stockholder proposals to be brought before an annual meeting of our stockholders, including proposed nominations of persons for election to our board of directors.

In accordance with our amended and restated certificate of incorporation, our board of directors is divided into three classes with staggered three-year terms.

The foregoing provisions make it more difficult for another party to obtain control of us by replacing our board of directors. Since our board of directors has the power to retain and discharge our officers, these provisions could also make it more difficult for existing stockholders or another party to effect a change in management. In addition, the authorization of undesignated preferred stock makes it possible for our board of directors to issue preferred stock with voting or other rights or preferences that could impede the success of any attempt to change our control.

These provisions are designed to reduce our vulnerability to an unsolicited acquisition proposal and to discourage certain tactics that may be used in proxy fights. However, such provisions could have the effect of discouraging others from making tender offers for our shares and may have the effect of deterring hostile

TABLE OF CONTENTS

takeovers or delaying changes in our control or management. As a consequence, these provisions may also inhibit fluctuations in the market price of our stock that could result from actual or rumored takeover attempts.

Section 203 of the Delaware General Corporation Law

We are subject to Section 203 of the DGCL, which prohibits a Delaware corporation from engaging in any business combination with any interested stockholder for a period of three years after the date that such stockholder became an interested stockholder, subject to certain exceptions.

Choice of Forum

Our amended and restated certificate of incorporation provides that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware (or, if and only if the Court of Chancery of the State of Delaware lacks subject matter jurisdiction, any state court located within the State of Delaware or, if and only if all such state courts lack subject matter jurisdiction, the federal district court for the District of Delaware) and any appellate court therefrom is the sole and exclusive forum for the following claims or causes of action under the Delaware statutory or common law: (i) any derivative claim or cause of action brought on our behalf; (ii) any claim or cause of action for a breach of fiduciary duty owed by any of our current or former directors, officers, or other employees to us or our stockholders; (iii) any claim or cause of action against us or any of our current or former directors, officers or other employees arising out of or pursuant to any provision of the DGCL, our amended and restated certificate of incorporation, or our amended and restated bylaws (as each may be amended from time to time); (iv) any claim or cause of action seeking to interpret, apply, enforce or determine the validity of our amended and restated certificate of incorporation or our amended and restated bylaws (as each may be amended from time to time, including any right, obligation, or remedy thereunder); (v) any claim or cause of action as to which the DGCL confers jurisdiction to the Court of Chancery of the State of Delaware; and (vi) any claim or cause of action against us or any of our current or former directors, officers, or other employees governed by the internal-affairs doctrine, in all cases to the fullest extent permitted by law and subject to the court’s having personal jurisdiction over the indispensable parties named as defendants. Our amended and restated certificate of incorporation provides that, unless we consent in writing to the selection of an alternative forum, to the fullest extent permitted by law, the federal district courts of the United States are the exclusive forum for resolving any complaint asserting a cause or causes of action arising under the Securities Act, including all causes of action asserted against a defendant to such complaint. The choice of forum provision would not apply to claims or causes of action brought to enforce a duty or liability created by the Exchange Act or any other claim for which the federal courts have exclusive jurisdiction.

For the avoidance of doubt, these provisions are intended to benefit and may be enforced by us, our officers and directors, the underwriters to any offering giving rise to such complaint, and any other professional entity whose profession gives authority to a statement made by that person or entity and who has prepared or certified any part of the documents underlying the offering. While the Delaware courts have determined that such choice of forum provisions are facially valid, a stockholder may nevertheless seek to bring a claim in a venue other than those designated in the exclusive forum provisions, and there can be no assurance that such provisions will be enforced by a court in those other jurisdictions. We note that investors cannot waive compliance with the federal securities laws and the rules and regulations thereunder.

Additionally, our amended and restated certificate of incorporation provides that any person or entity holding, owning or otherwise acquiring any interest in any of our securities shall be deemed to have notice of and consented to these provisions.

Exchange Listing

Our common stock is listed on The Nasdaq Global Select Market under the symbol “ALMS.” Our non-voting common stock is not listed on any securities exchange. The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, on Nasdaq or any securities market or other exchange of the preferred stock covered by such prospectus supplement.

TABLE OF CONTENTS

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Equiniti Trust Company, LLC. The transfer agent’s address is 28 Liberty Street, 53rd Floor, New York, NY 10005. The transfer agent for any series of preferred stock that we or selling securityholders may offer under this prospectus will be named and described in the applicable prospectus supplement for that series.

TABLE OF CONTENTS

DESCRIPTION OF DEBT SECURITIES

We may issue debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. While the terms we have summarized below will apply generally to any debt securities that we may offer under this prospectus, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. The terms of any debt securities offered under a prospectus supplement may differ from the terms described below. Unless the context requires otherwise, whenever we refer to the indenture, we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

We will issue the debt securities under the indenture that we will enter into with the trustee named in the indenture. The indenture will be qualified under the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”). We have filed the form of indenture as an exhibit to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

The following summary of material provisions of the debt securities and the indenture is subject to, and qualified in its entirety by reference to, all of the provisions of the indenture applicable to a particular series of debt securities. We urge you to read the applicable prospectus supplements and any related free writing prospectuses related to the debt securities that we may offer under this prospectus, as well as the complete indenture that contains the terms of the debt securities.

General

The indenture does not limit the amount of debt securities that we may issue. It provides that we may issue debt securities up to the principal amount that we may authorize and may be in any currency or currency unit that we may designate. Except for the limitations on consolidation, merger and sale of all or substantially all of our assets contained in the indenture, the terms of the indenture do not contain any covenants or other provisions designed to give holders of any debt securities protection against changes in our operations, financial condition or transactions involving us.

We may issue the debt securities issued under the indenture as “discount securities,” which means they may be sold at a discount below their stated principal amount. These debt securities, as well as other debt securities that are not issued at a discount, may be issued with “original issue discount,” or OID, for U.S. federal income tax purposes because of interest payment and other characteristics or terms of the debt securities. Material U.S. federal income tax considerations applicable to debt securities issued with OID will be described in more detail in any applicable prospectus supplement.

We will describe in the applicable prospectus supplement the terms of the series of debt securities being offered, including:

•

the title of the series of debt securities;

•

any limit upon the aggregate principal amount that may be issued;

•

the maturity date or dates;

•

the form of the debt securities of the series;

•

the applicability of any guarantees;

•

whether or not the debt securities will be secured or unsecured, and the terms of any secured debt;

•

whether the debt securities rank as senior debt, senior subordinated debt, subordinated debt or any combination thereof, and the terms of any subordination;

•

if the price (expressed as a percentage of the aggregate principal amount thereof) at which such debt securities will be issued is a price other than the principal amount thereof, the portion of the principal amount thereof payable upon declaration of acceleration of the maturity thereof, or if applicable, the portion of the principal amount of such debt securities that is convertible into another security or the method by which any such portion shall be determined;

TABLE OF CONTENTS

•

the interest rate or rates, which may be fixed or variable, or the method for determining the rate and the date interest will begin to accrue, the dates interest will be payable and the regular record dates for interest payment dates or the method for determining such dates;

•

our right, if any, to defer payment of interest and the maximum length of any such deferral period;

•

if applicable, the date or dates after which, or the period or periods during which, and the price or prices at which, we may, at our option, redeem the series of debt securities pursuant to any optional or provisional redemption provisions and the terms of those redemption provisions;

•

the date or dates, if any, on which, and the price or prices at which we are obligated, pursuant to any mandatory sinking fund or analogous fund provisions or otherwise, to redeem, or at the holder’s option to purchase, the series of debt securities and the currency or currency unit in which the debt securities are payable;

•

the denominations in which we will issue the series of debt securities, if other than denominations of $1,000 and any integral multiple thereof;

•

any and all terms, if applicable, relating to any auction or remarketing of the debt securities of that series and any security for our obligations with respect to such debt securities and any other terms which may be advisable in connection with the marketing of debt securities of that series;

•

whether the debt securities of the series shall be issued in whole or in part in the form of a global security or securities;

•

the terms and conditions, if any, upon which such global security or securities may be exchanged in whole or in part for other individual securities, and the depositary for such global security or securities;

•

if applicable, the provisions relating to conversion or exchange of any debt securities of the series and the terms and conditions upon which such debt securities will be so convertible or exchangeable, including the conversion or exchange price, as applicable, or how it will be calculated and may be adjusted, any mandatory or optional (at our option or the holders’ option) conversion or exchange features, the applicable conversion or exchange period and the manner of settlement for any conversion or exchange;

•

if other than the full principal amount thereof, the portion of the principal amount of debt securities of the series which shall be payable upon declaration of acceleration of the maturity thereof;

•

additions to or changes in the covenants applicable to the particular debt securities being issued, including, among others, the consolidation, merger or sale covenant;

•

additions to or changes in the events of default with respect to the securities and any change in the right of the trustee or the holders to declare the principal, premium, if any, and interest, if any, with respect to such securities to be due and payable;

•

additions to or changes in or deletions of the provisions relating to covenant defeasance and legal defeasance;

•

additions to or changes in the provisions relating to satisfaction and discharge of the indenture;

•

additions to or changes in the provisions relating to the modification of the indenture both with and without the consent of holders of debt securities issued under the indenture;

•

the currency of payment of debt securities if other than U.S. dollars and the manner of determining the equivalent amount in U.S. dollars;

•

whether interest will be payable in cash or additional debt securities at our or the holders’ option and the terms and conditions upon which the election may be made;

•

the terms and conditions, if any, upon which we will pay amounts in addition to the stated interest, premium, if any, and principal amounts of the debt securities of the series to any holder that is not a “United States person” for federal tax purposes;

TABLE OF CONTENTS

•

any restrictions on transfer, sale or assignment of the debt securities of the series; and

•

any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities, any other additions or changes in the provisions of the indenture, and any terms that may be required by us or advisable under applicable laws or regulations.

Conversion or Exchange Rights

We will set forth in the applicable prospectus supplement the terms on which a series of debt securities may be convertible into or exchangeable for our common stock or our other securities. We will include provisions as to settlement upon conversion or exchange and whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of our common stock or our other securities that the holders of the series of debt securities receive would be subject to adjustment.

Consolidation, Merger or Sale

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the indenture will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of our assets as an entirety or substantially as an entirety. However, any successor to or acquirer of such assets (other than a subsidiary of ours) must assume all of our obligations under the indenture or the debt securities, as appropriate.

Events of Default under the Indenture

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the following are events of default under the indenture with respect to any series of debt securities that we may issue:

•

if we fail to pay any installment of interest on any series of debt securities, as and when the same shall become due and payable, and such default continues for a period of 90 days; provided, however, that a valid extension of an interest payment period by us in accordance with the terms of any indenture supplemental thereto shall not constitute a default in the payment of interest for this purpose;

•

if we fail to pay the principal of, or premium, if any, on any series of debt securities as and when the same shall become due and payable whether at maturity, upon redemption, by declaration or otherwise, or in any payment required by any sinking or analogous fund established with respect to such series; provided, however, that a valid extension of the maturity of such debt securities in accordance with the terms of any indenture supplemental thereto shall not constitute a default in the payment of principal or premium, if any;

•

if we fail to observe or perform any other covenant or agreement contained in the debt securities or the indenture, other than a covenant specifically relating to another series of debt securities, and our failure continues for 90 days after we receive written notice of such failure, requiring the same to be remedied and stating that such is a notice of default thereunder, from the trustee or holders of at least 25% in aggregate principal amount of the outstanding debt securities of the applicable series; and

•

if specified events of bankruptcy, insolvency or reorganization occur.

If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may declare the unpaid principal of, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default specified in the last bullet point above occurs with respect to us, the principal amount of and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the trustee or any holder.

TABLE OF CONTENTS

The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

Subject to the terms of the indenture, if an event of default under an indenture shall occur and be continuing, the trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such holders have offered the trustee reasonable indemnity. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or power conferred on the trustee, with respect to the debt securities of that series, provided that:

•

the direction so given by the holder is not in conflict with any law or the applicable indenture; and

•

subject to its duties under the Trust Indenture Act, the trustee need not take any action that might involve it in personal liability or might be unduly prejudicial to the holders not involved in the proceeding.

A holder of the debt securities of any series will have the right to institute a proceeding under the indenture or to appoint a receiver or trustee, or to seek other remedies only if:

•

the holder has given written notice to the trustee of a continuing event of default with respect to that series;

•

the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series have made written request;

•

such holders have offered to the trustee indemnity satisfactory to it against the costs, expenses and liabilities to be incurred by the trustee in compliance with the request; and

•

the trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series other conflicting directions within 90 days after the notice, request and offer.

These limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment of the principal, premium, if any, or interest on, the debt securities.

We will periodically file statements with the trustee regarding our compliance with specified covenants in the indenture.

Modification of Indenture; Waiver

We and the trustee may change an indenture without the consent of any holders with respect to specific matters:

•

to cure any ambiguity, defect or inconsistency in the indenture or in the debt securities of any series;

•

to comply with the provisions described above under “Description of Debt Securities — Consolidation, Merger or Sale;”

•

to provide for uncertificated debt securities in addition to or in place of certificated debt securities;

•

to add to our covenants, restrictions, conditions or provisions such new covenants, restrictions, conditions or provisions for the benefit of the holders of all or any series of debt securities, to make the occurrence, or the occurrence and the continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default or to surrender any right or power conferred upon us in the indenture;

•

to add to, delete from or revise the conditions, limitations, and restrictions on the authorized amount, terms, or purposes of issue, authentication and delivery of debt securities, as set forth in the indenture;

TABLE OF CONTENTS

•

to make any change that does not adversely affect the interests of any holder of debt securities of any series in any material respect;

•

to provide for the issuance of and establish the form and terms and conditions of the debt securities of any series as provided above under “Description of Debt Securities - General” to establish the form of any certifications required to be furnished pursuant to the terms of the indenture or any series of debt securities, or to add to the rights of the holders of any series of debt securities;

•

to evidence and provide for the acceptance of appointment under any indenture by a successor trustee; or

•

to comply with any requirements of the SEC in connection with the qualification of any indenture under the Trust Indenture Act.

In addition, under the indenture, the rights of holders of a series of debt securities may be changed by us and the trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series that is affected. However, unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, we and the trustee may make the following changes only with the consent of each holder of any outstanding debt securities affected:

•

extending the fixed maturity of any debt securities of any series;

•

reducing the principal amount, reducing the rate of or extending the time of payment of interest, or reducing any premium payable upon the redemption of any series of any debt securities; or

•

reducing the percentage of debt securities, the holders of which are required to consent to any amendment, supplement, modification or waiver.

Discharge

Each indenture provides that we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for specified obligations, including obligations to:

•

provide for payment;

•

replace stolen, lost or mutilated debt securities of the series;

•

pay principal of and premium and interest on any debt securities of the series;

•

maintain paying agencies;

•

hold monies for payment in trust;

•

recover excess money held by the trustee;

•

compensate and indemnify the trustee; and

•

appoint any successor trustee.

In order to exercise our rights to be discharged, we must deposit with the trustee money or government obligations sufficient to pay all the principal of, any premium, if any, and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

We will issue the debt securities of each series only in fully registered form without coupons and, unless we provide otherwise in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indenture provides that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company (“DTC”) or another depositary named by us and identified in the applicable prospectus supplement with respect to that series. To the extent the debt securities of a series are issued in global form and as book-entry, a description of terms relating to any book-entry securities will be set forth in the applicable prospectus supplement.

TABLE OF CONTENTS

At the option of the holder, subject to the terms of the indenture and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the debt securities of any series can exchange the debt securities for other debt securities of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

Subject to the terms of the indenture and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, we will impose no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.

If we elect to redeem the debt securities of any series, we will not be required to:

•

issue, register the transfer of, or exchange any debt securities of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities that may be selected for redemption and ending at the close of business on the day of the mailing; or

•

register the transfer of or exchange any debt securities so selected for redemption, in whole or in part, except the unredeemed portion of any debt securities we are redeeming in part.

Information Concerning the Trustee

The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs. Subject to this provision, the trustee is under no obligation to exercise any of the powers given it by the indenture at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

Payment and Paying Agents

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

We will pay principal of and any premium and interest on the debt securities of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, we will make interest payments by check that we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in the applicable prospectus supplement, we will designate the corporate trust office of the trustee as our sole paying agent for payments with respect to debt securities of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the debt securities of a particular series. We will maintain a paying agent in each place of payment for the debt securities of a particular series.

All money we pay to a paying agent or the trustee for the payment of the principal of or any premium or interest on any debt securities that remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the debt security thereafter may look only to us for payment thereof.

TABLE OF CONTENTS

Governing Law

The indenture and the debt securities will be governed by and construed in accordance with the internal laws of the State of New York, except to the extent that the Trust Indenture Act is applicable.

TABLE OF CONTENTS

DESCRIPTION OF WARRANTS

The following description, together with the additional information we may include in any applicable prospectus supplements and in any related free writing prospectuses, summarizes the material terms and provisions of the warrants that we or selling securityholders may offer under this prospectus, which may consist of warrants to purchase common stock, preferred stock or debt securities and may be issued in one or more series. Warrants may be offered independently or together with common stock, preferred stock or debt securities offered by any prospectus supplement, and may be attached to or separate from those securities. While the terms we have summarized below will apply generally to any warrants that we or selling securityholders may offer under this prospectus, we will describe the particular terms of any series of warrants that we or selling securityholders may offer in more detail in the applicable prospectus supplement and any applicable free writing prospectus. The terms of any warrants offered under a prospectus supplement may differ from the terms described below. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness.

We have filed forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants that may be offered as exhibits to the registration statement of which this prospectus is a part. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of warrant agreement, if any, including a form of warrant certificate, that describes the terms of the particular series of warrants we or selling securityholders are offering. The following summaries of material provisions of the warrants and the warrant agreements are subject to, and qualified in their entirety by reference to, all the provisions of the warrant agreement and warrant certificate applicable to the particular series of warrants that we or selling securityholders may offer under this prospectus. We urge you to read the applicable prospectus supplements related to the particular series of warrants that we or selling securityholders may offer under this prospectus, as well as any related free writing prospectuses, and the complete warrant agreements and warrant certificates that contain the terms of the warrants.

General

We will describe in the applicable prospectus supplement the terms relating to a series of warrants being offered, including, to the extent applicable:

•

the title of such securities;

•

the offering price or prices and aggregate number of warrants offered;

•

the currency or currencies for which the warrants may be purchased;

•

if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;

•

if applicable, the date on and after which the warrants and the related securities will be separately transferable;

•

in the case of warrants to purchase debt securities, the principal amount of debt securities purchasable upon exercise of one warrant and the price at which, and currency in which, this principal amount of debt securities may be purchased upon such exercise;

•

in the case of warrants to purchase common stock or preferred stock, the number of shares of common stock or preferred stock, as the case may be, purchasable upon the exercise of one warrant and the price at which, and the currency in which, these shares may be purchased upon such exercise;

•

the effect of any merger, consolidation, sale or other disposition of our business on the warrant agreements and the warrants;

•

the terms of any rights to redeem or call the warrants;

•

the terms of any rights to force the exercise of the warrants;

•

any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;

TABLE OF CONTENTS

•

the dates on which the right to exercise the warrants will commence and expire;

•

the manner in which the warrant agreements and warrants may be modified;

•

a discussion of any material or special U.S. federal income tax consequences of holding or exercising the warrants;

•

the terms of the securities issuable upon exercise of the warrants; and

•

any other specific terms, preferences, rights or limitations of or restrictions on the warrants.

Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including:

•

in the case of warrants to purchase debt securities, the right to receive payments of principal of, or premium, if any, or interest on, the debt securities purchasable upon exercise or to enforce covenants in the applicable indenture; or

•

in the case of warrants to purchase common stock or preferred stock, the right to receive dividends, if any, or payments upon our liquidation, dissolution, or winding up, or to exercise voting rights, if any.

Exercise of Warrants

Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants by delivering the warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent in immediately available funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of the warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to the warrant agent in connection with the exercise of the warrant.

Upon receipt of the required payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the securities purchasable upon such exercise. If fewer than all of the warrants represented by the warrant certificate are exercised, then we will issue a new warrant certificate for the remaining amount of warrants. If we so indicate in the applicable prospectus supplement, holders of the warrants may surrender securities as all or part of the exercise price for warrants.

Governing Law

Unless we provide otherwise in the applicable prospectus supplement, the warrants and warrant agreements, and any claim, controversy or dispute arising under or related to the warrants or warrant agreements, will be governed by and construed in accordance with the laws of the State of New York.

Enforceability of Rights by Holders of Warrants

Each warrant agent, if any, will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

TABLE OF CONTENTS

LEGAL OWNERSHIP OF SECURITIES

We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee, depositary or warrant agent maintain for this purpose as the “holders” of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as “indirect holders” of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary’s book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

Only the person in whose name a security is registered is recognized as the holder of that security. Global securities will be registered in the name of the depositary or its participants. Consequently, for global securities, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

As a result, investors in a global security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary’s book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not legal holders, of the securities.

Street Name Holders

We may terminate a global security or issue securities that are not issued in global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

For securities held in street name, we or any applicable trustee or depositary will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we or any such trustee or depositary will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not legal holders, of those securities.

Legal Holders

Our obligations, as well as the obligations of any applicable trustee or third party employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with its participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, to relieve us of the consequences of a default or of our

TABLE OF CONTENTS

obligation to comply with a particular provision of an indenture, or for other purposes. In such an event, we would seek approval only from the holders, and not the indirect holders, of the securities. Whether and how the legal holders contact the indirect holders is up to the legal holders.

Special Considerations for Indirect Holders

If you hold securities through a bank, broker or other financial institution, either in book-entry form because the securities are represented by one or more global securities or in street name, you should check with your own institution to find out:

•

how it handles securities payments and notices;

•

whether it imposes fees or charges;

•

how it would handle a request for the holders’ consent, if ever required;

•

whether and how you can instruct it to send you securities registered in your own name so you can be a holder, if that is permitted in the future;

•

how it would exercise rights under the securities if there were a default or other event triggering the need for holders to act to protect their interests; and

•

if the securities are in book-entry form, how the depositary’s rules and procedures will affect these matters.

Global Securities

A global security is a security that represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

Each security issued in book-entry form will be represented by a global security that we issue to, deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, DTC will be the depositary for all securities issued in book-entry form. A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under “— Special Situations When a Global Security Will Be Terminated.” As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and legal holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a legal holder of the security, but only an indirect holder of a beneficial interest in the global security.

If the prospectus supplement for a particular security indicates that the security will be issued as a global security, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations for Global Securities

As an indirect holder, an investor’s rights relating to a global security will be governed by the account rules of the investor’s financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

If securities are issued only as global securities, an investor should be aware of the following:

•

an investor cannot cause the securities to be registered in his or her name, and cannot obtain non-global certificates for his or her interest in the securities, except in the special situations we describe below;

TABLE OF CONTENTS

•

an investor will be an indirect holder and must look to his or her own bank or broker for payments on the securities and protection of his or her legal rights relating to the securities, as we describe above;

•

an investor may not be able to sell interests in the securities to some insurance companies and to other institutions that are required by law to own their securities in non-book-entry form;

•

an investor may not be able to pledge his or her interest in the global security in circumstances where certificates representing the securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;

•

the depositary’s policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to an investor’s interest in the global security;

•

we and any applicable trustee have no responsibility for any aspect of the depositary’s actions or for its records of ownership interests in the global security, nor will we or any applicable trustee supervise the depositary in any way;

•

the depositary may, and we understand that DTC will, require that those who purchase and sell interests in the global security within its book-entry system use immediately available funds, and your broker or bank may require you to do so as well; and

•

financial institutions that participate in the depositary’s book-entry system, and through which an investor holds its interest in the global security, may also have their own policies affecting payments, notices and other matters relating to the securities.

There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When a Global Security Will Be Terminated

In a few special situations described below, a global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks or brokers to find out how to have their interests in securities transferred to their own names, so that they will be direct holders. We have described the rights of holders and street name investors above.

Unless we provide otherwise in the applicable prospectus supplement, a global security will terminate when the following special situations occur:

•

if the depositary notifies us that it is unwilling, unable or no longer qualified to continue as depositary for that global security and we do not appoint another institution to act as depositary within 90 days;

•

if we notify any applicable trustee that we wish to terminate that global security; or

•

if an event of default has occurred with regard to securities represented by that global security and has not been cured or waived.

The applicable prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the prospectus supplement. When a global security terminates, the depositary, and neither we nor any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

TABLE OF CONTENTS

SELLING SECURITYHOLDERS

Selling securityholders are persons or entities that, directly or indirectly, have acquired or will from time to time acquire from us, our securities. If the registration statement of which this prospectus forms a part is used by selling securityholders for the resale of any securities registered thereunder pursuant to a registration rights agreement between us and such selling securityholders or otherwise, information about such selling securityholders, their beneficial ownership of our securities and their relationship with us will be set forth in a prospectus supplement, in a post-effective amendment or in filings we make with the SEC under the Exchange Act that are incorporated by reference.

TABLE OF CONTENTS

PLAN OF DISTRIBUTION

We or selling securityholders may sell the securities covered hereby from time to time pursuant to underwritten public offerings, direct sales to the public, negotiated transactions, block trades or a combination of these methods. A distribution of these securities offered by this prospectus may also be effected through the issuance of derivative securities, including, without limitation, warrants. We or selling securityholders may also sell the securities to or through underwriters or dealers, through agents, directly to one or more purchasers or through a combination of any of these methods of sale. We or selling securityholders may distribute securities from time to time in one or more transactions:

•

at a fixed price or prices, which may be changed;

•

at market prices prevailing at the time of sale;

•

at prices related to such prevailing market prices; or

•

at negotiated prices.

We may also sell equity securities covered by this registration statement in an “at the market offering” as defined in Rule 415(a)(4) under the Securities Act. Such offering may be made into an existing trading market for such securities in transactions at other than a fixed price, either:

•

on or through the facilities of Nasdaq or any other securities exchange or quotation or trading service on which such securities may be listed, quoted or traded at the time of sale; and/or

•

to or through a market maker other than on Nasdaq or such other securities exchanges or quotation or trading services.

Such “at the market offerings,” if any, may be conducted by underwriters acting as principal or agent.

A prospectus supplement or supplements (and any related free writing prospectus that we may authorize to be provided to you) will describe the terms of the offering of the securities, including, to the extent applicable:

•

the terms of the offering;

•

the name or names of any underwriters, dealers or agents, if any;

•

the name or names of any managing underwriter or underwriters, if any;

•

the amounts of securities underwritten or purchased by each of them;

•

the name or names of the selling securityholders, if any;

•

the purchase price of the securities or other consideration therefor and the proceeds, if any, we will receive from the sale;

•

any over-allotment options under which underwriters may purchase additional securities from us;

•

any agency fees or underwriting discounts, concessions, commissions and other items constituting agents’ or underwriters’ compensation;

•

any delayed delivery arrangements;

•

any public offering price;

•

any discounts or concessions allowed or reallowed or paid to dealers; and

•

any securities exchange or market on which the securities may be listed.

Only underwriters named in the prospectus supplement are underwriters of the securities offered by the prospectus supplement. Dealers and agents participating in the distribution of the securities may be deemed to be underwriters, and compensation received by them on resale of the securities may be deemed to be underwriting discounts. If such dealers or agents were deemed to be underwriters, they may be subject to statutory liabilities under the Securities Act.

If underwriters are used in the sale, they will acquire the securities for their own account and may resell the securities from time to time in one or more transactions at a fixed public offering price or at varying prices

TABLE OF CONTENTS

determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. We or selling securityholders may offer the securities to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Subject to certain conditions, the underwriters will be obligated to purchase all of the securities offered by the applicable prospectus supplement, other than securities covered by any option to purchase additional securities. If a dealer is used in the sale of securities, we or an underwriter will sell the securities to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale. To the extent required, we will set forth in the prospectus supplement the name of the dealer and the terms of the transaction. Any public offering price and any discounts or concessions allowed or re-allowed or paid to dealers may change from time to time. We or selling securityholders may use underwriters with whom we have a material relationship. We will describe in the prospectus supplement that names the underwriter the nature of any such relationship.

We or selling securityholders may sell securities directly or through agents we designate from time to time. In the prospectus supplement, we will name any agent involved in the offering and sale of securities and describe any commissions and other compensation we will pay the agent. Unless the prospectus supplement states otherwise, our agent will act on a best-efforts basis for the period of its appointment.

We may authorize agents or underwriters to solicit offers by certain types of institutional investors to purchase securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. We will describe in the prospectus supplement the conditions to these contracts and the commissions we must pay for solicitation of these contracts.

We may provide agents, underwriters and dealers with indemnification against civil liabilities related to this offering, including liabilities under the Securities Act, or contribution with respect to payments that the agents, underwriters or dealers may make with respect to these liabilities. Agents, underwriters and dealers, or their affiliates, may engage in transactions with, or perform services for, us in the ordinary course of business.

Unless the applicable prospectus supplement states otherwise, all securities we offer, other than common stock, will be new issues of securities with no established trading market. Any agents or underwriters may make a market in these securities but will not be obligated to do so and may discontinue any market making at any time without notice. We cannot guarantee the liquidity of the trading markets for any securities. There is currently no market for any of the offered securities, other than our common stock which is listed on Nasdaq. We have no current plans for listing of the preferred stock, debt securities or warrants on any securities exchange or quotation system; any such listing with respect to any particular preferred stock, debt securities or warrants will be described in the applicable prospectus supplement or other offering materials, as the case may be.

Any agents and underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Rule 103 of Regulation M under the Exchange Act. Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a stabilizing or covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time. These transactions may be effected on any exchange or over-the-counter market or otherwise.

Any underwriters who are qualified market makers on Nasdaq may engage in passive market-making transactions in the securities on Nasdaq in accordance with Rule 103 of Regulation M during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker’s

TABLE OF CONTENTS

bid, however, the passive market maker’s bid must then be lowered when certain purchase limits are exceeded. Passive market making may stabilize the market price of the securities at a level above that which might otherwise prevail in the open market and, if commenced, may be discontinued at any time.

In compliance with guidelines of the Financial Industry Regulatory Authority (“FINRA”), the maximum consideration or discount to be received by any FINRA member or independent broker dealer may not exceed 8% of the aggregate amount of the securities offered pursuant to this prospectus and the applicable prospectus supplement.

TABLE OF CONTENTS

LEGAL MATTERS

Cooley LLP will pass upon the validity of the securities offered by this prospectus, and any supplement thereto, unless otherwise indicated in the applicable prospectus supplement. Additional legal matters may be passed upon for us or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement. As of the date of this prospectus, partners of Cooley LLP and GC&H Investments, LLC, an entity comprising partners and associates of Cooley LLP, beneficially own 19,780 shares of common stock.

EXPERTS

The financial statements of Alumis Inc. incorporated in this prospectus by reference to the Annual Report on Form 10-K for the year ended December 31, 2025 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The audited historical financial statements of ACELYRIN, Inc. included on Exhibit 99.1 of Alumis Inc.’s Current Report on Form 8-K/A dated June 30, 2025 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

This prospectus is part of the registration statement on Form S-3 we filed with the SEC under the Securities Act and does not contain all the information set forth in the registration statement. Whenever a reference is made in this prospectus to any of our contracts, agreements or other documents, the reference may not be complete and you should refer to the exhibits that are a part of the registration statement or the exhibits to the reports or other documents incorporated by reference into this prospectus for a copy of such contract, agreement or other document. Because we are subject to the information and reporting requirements of the Exchange Act, we file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC’s website at http://www.sec.gov. In addition, we maintain a website that contains information about us at https://www.alumis.com. The information found on, or otherwise accessible through our website is not incorporated by reference into, and does not form a part of, this prospectus or any accompanying prospectus supplement or any other document or report we file or furnish with the SEC.

TABLE OF CONTENTS

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to incorporate by reference information from other documents that we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus. Information in this prospectus supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus, while information that we file later with the SEC will automatically update and supersede the information in this prospectus. We incorporate by reference into this prospectus and the registration statement of which this prospectus is a part the information or documents listed below that we have filed with the SEC (Commission File No. 001-42143):

•

our Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on March 19, 2026;

•

our Current Report on Form 8-K filed with the SEC on January 6, 2026 (to the extent the information in such report is filed and not furnished);

•

the audited consolidated financial statements of ACELYRIN, Inc. as of December 31, 2024 and 2023 and for the years then ended, the notes related thereto and the report of PricewaterhouseCoopers LLP, independent accountants, included in Exhibit 99.1 to our Current Report on Form 8-K/A filed with the SEC on June 30, 2025;

•

the unaudited consolidated financial statements of ACELYRIN, Inc. as of March 31, 2025 and for the three months ended March 31, 2025 and 2024, and the notes related thereto, included in Exhibit 99.2 to our Current Report on Form 8-K/A filed with the SEC on June 30, 2025;

•

the unaudited pro forma condensed combined financial information included in Exhibit 99.1 to the registration statement of which this prospectus is a part; and

•

the description of our common stock contained in our registration statement on Form 8-A, filed with the SEC on June 25, 2024, as updated by Exhibit 4.3 of our Annual Report on Form 10-K for the year ended December 31, 2024, filed with the SEC on March 19, 2025, including any amendments or reports filed for the purpose of updating such description.

We also incorporate by reference any future filings (other than current reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items unless such Form 8-K expressly provides to the contrary) made with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, including those made after the date of the initial filing of the registration statement of which this prospectus is a part, until we file a post-effective amendment that indicates the termination of the offering of the securities made by this prospectus, which will become a part of this prospectus from the date that such documents are filed with the SEC. Information in such future filings updates and supplements the information provided in this prospectus. Any statements in any such future filings will automatically be deemed to modify and supersede any information in any document we previously filed with the SEC that is incorporated or deemed to be incorporated herein by reference to the extent that statements in the later-filed document modify or replace such earlier statements. We will furnish without charge to each person, including any beneficial owner, to whom a prospectus is delivered, upon written or oral request, a copy of any or all of the documents incorporated by reference into this prospectus but not delivered with the prospectus, including exhibits that are specifically incorporated by reference into such documents. You should direct any requests for documents to:

Alumis Inc.
Attn: Corporate Secretary
280 East Grand Avenue
South San Francisco, CA 94080
(650) 231-6625

TABLE OF CONTENTS

Prospectus

Up to $300,000,000

COMMON STOCK

We have entered into a Controlled Equity OfferingSM Sales Agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (“Cantor”), dated March 18, 2026, relating to the sale of shares of our common stock offered by this prospectus. In accordance with the terms of the Sales Agreement, we may offer and sell shares of our common stock, par value $0.0001 per share, having an aggregate offering price of up to $300,000,000 from time to time to or through Cantor acting as our sales agent.

We have two classes of common stock: the voting common stock we may offer and sell under this prospectus and non-voting common stock. Only voting common stock will be offered and sold under this prospectus, and unless otherwise noted, all references in this prospectus to our “common stock,” “common shares” or “shares” refer to our voting common stock.

Our common stock is listed on The Nasdaq Global Select Market under the trading symbol “ALMS.” On March 18, 2026, the last reported sale price of our common stock was $25.42 per share.

Sales of our common stock, if any, under this prospectus may be made by any method permitted by law that is deemed an “at the market” equity offerings as defined in Rule 415 promulgated under the Securities Act of 1933, as amended (the “Securities Act”). Cantor is not required to sell any specific number or dollar amount of securities. Cantor will use commercially reasonable efforts consistent with its normal trading and sales practices, on mutually agreed terms between Cantor and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.

Cantor will be entitled to compensation at a commission rate for sales of common stock sold pursuant to the Sales Agreement will be an amount up to 3.0% of the gross proceeds of any shares of common stock sold under the Sales Agreement. In connection with the sale of the common stock on our behalf, Cantor will be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation paid to Cantor will be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to Cantor with respect to certain liabilities, including liabilities under the Securities Act and the Securities Exchange Act of 1934, as amended (the “Exchange Act”). See the section titled “Plan of Distribution” beginning on page 13 of this prospectus for additional information regarding the compensation to be paid to Cantor.

Investing in our common stock involves a high degree of risk. Before making an investment decision, you should review carefully the risks and uncertainties described in the section titled “Risk Factors” beginning on page 6 of this prospectus and under similar headings in the documents that are incorporated by reference into this prospectus.

Cantor

The date of this prospectus is March 19, 2026.

TABLE OF CONTENTS

	Page
ABOUT THIS PROSPECTUS		ii
PROSPECTUS SUMMARY		1
THE OFFERING		4
RISK FACTORS		6
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		8
USE OF PROCEEDS		10
DILUTION		11
PLAN OF DISTRIBUTION		13
LEGAL MATTERS		14
EXPERTS		14
WHERE YOU CAN FIND ADDITIONAL INFORMATION		14
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		15

TABLE OF CONTENTS

ABOUT THIS PROSPECTUS

This prospectus is a part of an automatic registration statement on Form S-3 that we have filed with the Securities and Exchange Commission (the “SEC”) as a “well-known seasoned issuer,” as defined in Rule 405 under the Securities Act of 1933, as amended (the “Securities Act”), using a “shelf” registration process. Under this shelf registration statement, we may offer and sell shares of our common stock and preferred stock, various series of debt securities and/or warrants to purchase any of such securities, either individually or in combination with other securities, from time to time in one or more offerings. Under this prospectus, we may offer and sell shares of our common stock from time to time, up to a total aggregate offering amount of $300,000,000, at prices and on terms to be determined by market conditions at the time of offering. We provide information to you about this offering of shares of our common stock in two separate documents that are bound together: (1) this prospectus, which describes the specific details regarding this offering; and (2) the accompanying base prospectus, which provides general information, some of which may not apply to this offering. Generally, when we refer to this “prospectus,” we are referring to both documents combined.

This prospectus relates to the offering of our common stock having an aggregate offering price of up to $300,000,000 under the Sales Agreement. Before buying any of the common stock that we are offering, we urge you to carefully read this prospectus, together with the information incorporated by reference in this prospectus and the information in any free writing prospectus that we may authorize for use in connection with this offering when making your investment decision. You should also read and consider the information in the documents we have referred you to under the sections titled “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.” These documents contain important information that you should consider when making your investment decision.

This prospectus adds to and updates information contained in the documents incorporated by reference into this prospectus. To the extent there is a conflict between the information contained in this prospectus, on the one hand, and the information contained in any document incorporated by reference into this prospectus that was filed with the SEC, before the date of this prospectus, on the other hand, you should rely on the information in this prospectus. If any statement in one of these documents is inconsistent with a statement in another document having a later date, for example, a document incorporated by reference into this prospectus, the statement in the document having the later date modifies or supersedes the earlier statement.

We have not, and Cantor has not, authorized any other person to provide you with any information or to make any representations other than those contained in, or incorporated by reference into, this prospectus and any free writing prospectuses prepared by or on behalf of us or to which we have referred you. We and Cantor take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We are not, and Cantor is not, making an offer to sell or soliciting an offer to buy these securities in any jurisdiction where an offer, sale or solicitation is not permitted. You should assume that the information appearing in this prospectus, the documents incorporated by reference herein and in any free writing prospectuses that we may authorize for use in connection with this offering, is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates.

We are offering to sell, and seeking offers to buy, shares of our common stock only in jurisdictions where offers and sales are permitted. The distribution of this prospectus and the offering of our common stock in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of our common stock and the distribution of this prospectus outside the United States. This prospectus does not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you.

TABLE OF CONTENTS

Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

iii

TABLE OF CONTENTS

PROSPECTUS SUMMARY

This summary highlights selected information contained elsewhere in this prospectus or incorporated by reference in this prospectus, and does not contain all of the information that you need to consider in making your investment decision. You should carefully read the entire prospectus and any related free writing prospectus, including the risks of investing in our common stock discussed under the section titled “Risk Factors” in this prospectus and under similar headings in the other documents that are incorporated by reference into this prospectus. You should also carefully read the information incorporated by reference into this prospectus, including our financial statements, and the exhibits to the registration statement of which this prospectus is a part.

Unless the context requires otherwise, references in this prospectus to “Alumis,” the “Company,” “we,” “us” and “our” refer to Alumis Inc. and its wholly owned subsidiary.

The Company

Corporate Information

TABLE OF CONTENTS

Implications of Being an Emerging Growth Company and a Smaller Reporting Company

•

relief from the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act of 2002, as amended;

•

less extensive disclosure obligations regarding executive compensation in our registration statements, periodic reports and proxy statements;

•

exemptions from the requirements to hold a nonbinding advisory vote on executive compensation; and

•

exemptions from stockholder approval of any golden parachute payments not previously approved.

TABLE OF CONTENTS

day of our second fiscal quarter. If we are a smaller reporting company at the time we cease to be an emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies. Specifically, as a smaller reporting company, we may choose to present only the two most recent fiscal years of audited financial statements in our Annual Report on Form 10-K and, similar to emerging growth companies, smaller reporting companies have reduced disclosure obligations regarding executive compensation.

TABLE OF CONTENTS

THE OFFERING

Common Stock Offered by Us

Shares of our common stock having an aggregate offering price of up to $300.0 million.

Total Common Stock and Non-Voting Common Stock to be Outstanding Immediately Following This Offering

Up to 136,806,003 shares (of which 131,183,595 shares will be common stock), assuming sales of 11,801,730 shares of our common stock in this offering, which is based on an offering price of $25.42 per share, the last reported sale price of our common stock on The Nasdaq Global Select Market on March 18, 2026. The actual number of shares issued will vary depending on the sale prices in this offering.

Manner of Offering

“At the market” offering that may be made from time to time through our sales agent, Cantor. See the section titled “Plan of Distribution” beginning on page 13 of this prospectus.

Use of Proceeds

We currently intend to use the net proceeds, if any, of this offering for general corporate purposes, including but not limited to, clinical trial expenses, research and development expenses, general and administrative expenses and capital expenditures. See the section titled “Use of Proceeds” on page 10 for a more complete description of the intended use of proceeds from this offering.

Risk Factors

Investing in our common stock involves significant risk. See the section titled “Risk Factors” beginning on page 6 of this prospectus and other information included and incorporated by reference in this prospectus for a discussion of factors that you should carefully consider before deciding to invest in our common stock.

Nasdaq Global Select Market Symbol

“ALMS.”

The number of shares of our common stock and non-voting common stock to be outstanding immediately after this offering set forth above is based on an aggregate of 125,004,273 shares of our common stock and non-voting common stock (of which 119,381,865 shares are common stock) outstanding as of December 31, 2025 after giving effect to the sale by us of 20,297,500 shares of our common stock in a public offering that closed in January 2026 (the “January 2026 Offering”), but excludes:

•

18,672,626 shares of common stock issuable upon the exercise of outstanding stock options under our 2021 Stock Plan (the “2021 Plan”), 2024 Equity Incentive Plan (the “2024 EIP”) and the ACELYRIN, Inc. 2020 Stock Option and Grant Plan, as amended (the “ACELYRIN 2020 Plan”), the ValenzaBio, Inc. Stock Plan (the “ValenzaBio Plan”) and the ACELYRIN, Inc. 2023 Equity Incentive Plan (the “ACELYRIN 2023 Plan” and, together with the ACELYRIN 2020 Plan and the ValenzaBio Plan, the “ACELYRIN Plans”) that were assumed in connection with our merger with ACELYRIN, Inc. (the “ACELYRIN Merger”), with a weighted-average exercise price of $8.56 per share as of December 31, 2025;

•

4,459,928 shares of common stock issuable upon the exercise of outstanding stock options under our 2021 Plan, 2024 EIP and ACELYRIN Plans, with a weighted-average exercise price of $26.22 per share that were granted subsequent to December 31, 2025;

•

1,680,472 shares of common stock issuable upon the exercise of outstanding stock options under our 2024 Performance Option Plan (the “2024 POP”), with a weighted-average exercise price of $10.19 per share as of December 31, 2025;

•

2,527,377 shares of common stock issuable upon the vesting and settlement of restricted stock units outstanding as of December 31, 2025;

TABLE OF CONTENTS

•

877,331 shares of common stock issuable upon the vesting and settlement of restricted stock units that were granted subsequent to December 31, 2025;

•

597,112 shares of our common stock reserved for future issuance under our 2024 EIP as of December 31, 2025, and any future increases in the number of shares of our common stock reserved for issuance under our 2024 EIP;

•

805,334 shares of our common stock reserved for issuance under our 2024 Employee Stock Purchase Plan (the “2024 ESPP”), as of December 31, 2025, and any future increases in the number of shares of our common stock reserved for issuance under our 2024 ESPP;

•

200,208 shares of our common stock reserved for future issuance under our 2024 POP as of December 31, 2025; and

•

6,585,521 shares of our common stock reserved for future issuance under the ACELYRIN 2023 Plan as of December 31, 2025.

Unless otherwise indicated, all information in this prospectus assumes no exercise of the outstanding stock options summarized above, and no vesting or settlement of the outstanding restricted stock units summarized above.

TABLE OF CONTENTS

RISK FACTORS

Investing in our common stock involves a high degree of risk. Before deciding whether to invest in our common stock, you should consider carefully the risks and uncertainties described below and discussed under the section titled “Risk Factors” contained in our most recent Annual Report on Form 10-K and in our subsequent Quarterly Reports on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus in their entirety, together with other information in this prospectus, the documents incorporated by reference and any free writing prospectuses that we may authorize for use in connection with this offering. The risks described in these documents are not the only ones we face, but those that we consider to be material. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have material adverse effects on our future results. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be seriously harmed. This could cause the trading price of our common stock to decline, resulting in a loss of all or part of your investment. Please also read carefully the section titled “Special Note Regarding Forward-Looking Statements” in this prospectus.

Additional Risks Related to this Offering

Our management team will have broad discretion to use the net proceeds from this offering, and its investment of these proceeds may not yield a favorable return.

Our management team will have broad discretion in the application of the net proceeds from this offering and could spend or invest the proceeds in ways with which our stockholders disagree. Accordingly, investors will need to rely on our management team’s judgment with respect to the use of these proceeds. We intend to use the proceeds from this offering in the manner described in the section titled “Use of Proceeds.” The failure by management to apply these funds effectively could negatively affect our ability to operate and grow our business. We cannot specify with certainty all of the particular uses for the net proceeds to be received upon the completion of this offering. In addition, the amount, allocation and timing of our actual expenditures will depend upon numerous factors, including any milestone payments received or paid in connection with any future strategic partnerships and royalties on sales of any future approved product. Accordingly, we will have broad discretion in using these proceeds. Until the net proceeds are used, they may be placed in investments that do not produce significant income or that may lose value.

If you purchase shares of common stock in this offering, you may experience immediate and substantial dilution of your investment.

The price of our common stock in this offering may be higher than the net tangible book value per share of our common stock. Therefore, if you purchase shares of our common stock in this offering, you may pay a price per share that substantially exceeds our net tangible book value per share. Assuming that an aggregate of 11,801,730 shares of our common stock are sold at a price of $25.42 per share, the last reported sale price of our common stock on The Nasdaq Global Select Market on March 18, 2026, for aggregate gross proceeds of approximately $300.0 million, and after deducting commissions and estimated aggregate offering expenses payable by us, you would experience immediate dilution of $19.10 per share, representing the difference between (i) our pro forma as adjusted net tangible book value per share as of December 31, 2025 after giving effect to the January 2026 Offering and this offering and (ii) the assumed offering price. To the extent outstanding stock options are exercised or outstanding restricted stock units vest and settle, there will be further dilution to new investors. In addition, to the extent we need to raise additional capital in the future and issue additional shares of common stock or securities convertible or exchangeable for our common stock, our then-existing stockholders may experience dilution, and the new securities may have rights senior to those of our common stock offered in this offering. See the section titled “Dilution” for a more detailed illustration of the dilution you would incur if you participate in this offering.

We do not intend to pay dividends on our common stock so any returns will be limited to the value of our stock.

We have never declared or paid any cash dividend on our capital stock. We currently anticipate that we will retain future earnings for the development, operation and expansion of our business and do not

TABLE OF CONTENTS

anticipate declaring or paying any cash dividends for the foreseeable future. Any return to stockholders will therefore be limited to the appreciation of their stock.

Future sales of our common stock in the public market, or the perception that such sales could occur, could cause our stock price to fall.

The sale of a substantial number of shares of our common stock or other equity-related securities in the public markets, or the perception that such sales could occur, could depress the market price of our common stock and impair our ability to raise capital through the sale of additional equity securities. We may sell large quantities of our common stock at any time pursuant to this prospectus or in one or more separate offerings. We cannot predict the effect that future sales of common stock or other equity-related securities would have on the market price of our common stock.

The actual number of shares we will issue in this offering and the gross proceeds resulting from those sales, at any one time or in total, is uncertain.

Subject to certain limitations in the Sales Agreement and compliance with applicable law, we have the discretion to deliver a placement notice to Cantor at any time throughout the term of the Sales Agreement. The number of shares that are sold by Cantor after delivering a placement notice will fluctuate based on the market price of our common stock during the sales period and limits we set with Cantor in any instruction to sell shares, and the demand for our common stock during the sales period. Because the price per share of each share sold will fluctuate based on the market price of our common stock during the sales period, it is not possible at this stage to predict the number of shares or the gross proceeds to be raised in connection with those sales, if any, that will be ultimately issued.

The common stock offered hereby will be sold in “at the market offerings,” and investors who buy shares at different times will likely pay different prices.

Investors who purchase shares in this offering at different times will likely pay different prices, and so may experience different outcomes in their investment results. We will have discretion, subject to market demand, to vary the timing, prices and numbers of shares sold, and there is no minimum or maximum sales price. Investors may experience a decline in the value of their shares as a result of share sales made at prices lower than the prices they paid.

TABLE OF CONTENTS

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the information incorporated by reference in this prospectus contain forward-looking statements within the meaning of Section 27A of the Securities Act, Section 21E of the Exchange Act, and the Private Securities Litigation Reform Act of 1995, as amended, that involve substantial risks and uncertainties.

These forward-looking statements are based on our management’s beliefs and assumptions and on information currently available to our management. All statements, other than statements of historical facts contained in this prospectus and the documents we have filed with the SEC that are incorporated by reference herein, including statements regarding our future financial condition, business strategy and plans, and objectives of management for future operations, are forward-looking statements. Discussions containing these forward-looking statements may be found, among other places, in the section titled “Risk Factors” in this prospectus, as well as under the sections titled “Business,” “Risk Factors,” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” contained in the documents incorporated by reference herein. In some cases, you can identify forward-looking statements by the following words: “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “ongoing,” “plan,” “potential,” “predict,” “project,” “should,” “will,” “would,” or the negative of these terms or other comparable terminology, although not all forward-looking statements contain these words.

These forward-looking statements involve risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from the information expressed or implied by these forward-looking statements. Although we believe that we have a reasonable basis for each forward-looking statement contained in this prospectus and the documents we have filed with the SEC that are incorporated by reference herein, we caution you that these statements are based on a combination of facts and factors currently known by us and our projections of the future, about which we cannot be certain. Forward-looking statements in this prospectus and the documents we have filed with the SEC that are incorporated by reference herein include, but are not limited to, statements about:

•

our plans to submit a New Drug Application for envu, formerly known as ESK-001, in PsO in the second half of 2026;

•

the potential for our product candidate envu to transform the treatment landscape for IL-23/IL-17 — driven diseases as well as those driven by Type I interferon;

•

the potential for envu to meaningfully elevate care for and effectively reduce the full burden of disease for patients with PsO;

•

the timing of our topline readout in our LUMUS Phase 2b trial;

•

our ability to obtain funding for our operations, including funding necessary to complete further development and any commercialization of our product candidates;

•

our expectations regarding the potential benefits of our strategy, including with respect to the integration of operations, technologies and personnel associated with the ACELYRIN Merger;

•

our plans relating to the research and development of our product candidates;

•

developments related to our competitors and our industry, including the success of competing product candidates and therapies that are, or may become, available;

•

details regarding our strategic vision and planned product candidate pipeline;

•

our beliefs regarding the success, cost and timing of our product candidate development activities and current and future clinical trials and studies including study design;

•

the timing or likelihood of regulatory filings or other actions and related regulatory authority responses;

•

the ability and willingness of various third parties to engage in research and development activities involving our product candidates, and our ability to leverage those activities;

•

our expectations regarding the potential benefits from any existing or future license or collaboration agreements, including the receipt of potential co-development, milestone and royalty payments;

TABLE OF CONTENTS

•

our expectations regarding the ease of administration associated with our product candidates;

•

our expectations regarding the patient compatibility associated with our product candidates;

•

our beliefs regarding the potential markets for our product candidates and our ability to serve those markets;

•

our beliefs regarding the potential of our product candidates to demonstrate differentiation from other approved therapies or therapies in development;

•

our ability to commercialize any approved products;

•

the rate and degree of market acceptance of any approved products;

•

our ability to attract and retain key personnel;

•

the accuracy of our estimates regarding our future revenue, as well as our future operating expenses, capital requirements and needs for additional financing;

•

regulatory developments in the United States and foreign countries;

•

our use of cash and other resources, including our expected use of proceeds from any offering under this prospectus; and

•

statements of belief and any statement of assumptions underlying any of the foregoing.

You should refer to the section titled “Risk Factors” included in this prospectus, in any free writing prospectuses we may authorize for use in connection with a specific offering, and in our most recent Annual Report on Form 10-K, and in our subsequent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus in their entirety, for a discussion of other important factors that may cause our actual results to differ materially from those expressed or implied by our forward-looking statements. As a result of these factors, we cannot assure you that the forward-looking statements in this prospectus and the documents we have filed with the SEC that are incorporated by reference herein will prove to be accurate.

TABLE OF CONTENTS

USE OF PROCEEDS

We may issue and sell shares of our common stock having aggregate sales proceeds of up to $300,000,000 from time to time. The amount of the net proceeds from this offering will depend upon the number of shares of our common stock sold and the market price at which they are sold. Because there is no minimum offering amount, the actual total public offering amount, commissions and proceeds to us, if any, are not determinable at this time. There can be no assurance that we will sell any shares under or fully utilize the Sales Agreement with Cantor as a source of financing.

We currently intend to use the net proceeds from this offering, if any, primarily for general corporate purposes, including but not limited to, clinical trial expenses, research and development expenses, general and administrative expenses and capital expenditures. The amounts and timing of our use of the net proceeds from this offering will depend on a number of factors, such as the timing and progress of our clinical trials, preclinical studies and research and development efforts, the timing and progress of any partnering and commercialization efforts, technological advances and the competitive environment for our products. As of the date of this prospectus, we cannot specify with certainty all of the particular uses of the net proceeds, if any, from the sale of securities under this prospectus. Accordingly, we will retain broad discretion over the use of such proceeds.

Pending the use of the net proceeds as described above, we intend to invest the net proceeds in short-term, investment-grade, interest-bearing instruments.

TABLE OF CONTENTS

DILUTION

As of December 31, 2025, we had a historical net tangible book value of $249.9 million, or $2.39 per share of common stock and non-voting common stock, based on an aggregate of 104,706,773 shares of common stock and non-voting common stock outstanding as of such date. Our historical net tangible book value per share represents total assets less intangible assets and total liabilities, divided by the number of shares of common stock and non-voting common stock outstanding.

After giving pro forma effect to the sale by us of 20,297,500 shares of our common stock in the January 2026 Offering, for net proceeds of approximately $323.8 million, after deducting underwriting discounts and commissions and offering expenses payable by us, we would have had a pro forma net tangible book value of $574.1 million, or $4.59 per share of common stock and non-voting common stock.

After giving further effect to the sale by us of 11,801,730 shares of common stock in this offering based on an assumed public offering price of $25.42 per share, which is the last reported sale price of our common stock on The Nasdaq Global Select Market on March 18, 2026, after deducting offering commissions and estimated offering expenses payable by us, our pro forma as adjusted net tangible book value as of December 31, 2025 would have been approximately $864.6 million, or approximately $6.32 per share. This amount represents an immediate increase in our pro forma net tangible book value of approximately $1.73 per share to our existing stockholders and an immediate dilution in our pro forma net tangible book value of approximately $19.10 per share to investors purchasing common stock in this offering. We determine dilution by subtracting our pro forma as adjusted net tangible book value per share after this offering from the amount of cash paid by an investor for a share of common stock in this offering. The following table illustrates this dilution on a per share basis:

Assumed public offering price per share			$	25.42
Historical net tangible book value per share as of December 31, 2025	$	2.39
Increase in net tangible book value per share after giving effect to the January 2026 Offering		2.20
Pro forma net tangible book value per share as of December 31, 2025	$	4.59
Increase in pro forma net tangible book value per share attributable to investors purchasing shares in this offering		1.73
Pro forma as adjusted net tangible book value per share after giving effect to this offering				6.32
Dilution in net tangible book value per share to investors purchasing shares in this offering			$	19.10

The table above assumes for illustrative purposes that an aggregate of 11,801,730 shares of our common stock are sold during the term of the Sales Agreement at a price of $25.42 per share, the last reported sale price of our common stock on The Nasdaq Global Select Market on March 18, 2026, for aggregate gross proceeds of $300.0 million. The shares subject to the Sales Agreement with Cantor are being sold from time to time at various prices. An increase of $1.00 per share in the price at which the shares are sold from the assumed offering price of $25.42 per share shown in the table above, assuming all of our common stock in the aggregate amount of $300.0 million during the term of the Sales Agreement with Cantor is sold at that price, would increase our adjusted net tangible book value per share after the offering to $6.34 per share and would increase the dilution in net tangible book value per share to new investors in this offering to $20.08 per share, after deducting commissions and estimated aggregate offering expenses payable by us. A decrease of $1.00 per share in the price at which the shares are sold from the assumed offering price of $25.42 per share shown in the table above, assuming all of our common stock in the aggregate amount of $300.0 million during the term of the Sales Agreement with Cantor is sold at that price, would decrease our adjusted net tangible book value per share after the offering to $6.30 per share and would decrease the dilution in net tangible book value per share to new investors in this offering to $18.12 per share, after deducting commissions and estimated aggregate offering expenses payable by us. This information is supplied for illustrative purposes only.

The above table and calculations are based on an aggregate of 125,004,273 shares of common stock and non-voting common stock (of which 119,381,865 shares are common stock) outstanding as of

TABLE OF CONTENTS

December 31, 2025 after giving effect to the sale by us of 20,297,500 shares of our common stock in the January 2026 Offering, but excludes:

•

18,672,626 shares of common stock issuable upon the exercise of outstanding stock options under our 2021 Plan, 2024 EIP and the ACELYRIN Plans, with a weighted-average exercise price of $8.56 per share as of December 31, 2025;

•

4,459,928 shares of common stock issuable upon the exercise of outstanding stock options under our 2021 Plan, 2024 EIP and the ACELYRIN Plans, with a weighted-average exercise price of $26.22 per share that were granted subsequent to December 31, 2025;

•

1,680,472 shares of common stock issuable upon the exercise of outstanding stock options under our 2024 POP, with a weighted-average exercise price of $10.19 per share as of December 31, 2025;

•

2,527,377 shares of common stock issuable upon the vesting and settlement of restricted stock units outstanding as of December 31, 2025;

•

877,331 shares of common stock issuable upon the vesting and settlement of restricted stock units that were granted subsequent to December 31, 2025;

•

805,334 shares of our common stock reserved for issuance under our 2024 ESPP, as of December 31, 2025, and any future increases in the number of shares of our common stock reserved for issuance under our 2024 ESPP;

•

200,208 shares of our common stock reserved for future issuance under our 2024 POP as of December 31, 2025; and

•

6,585,521 shares of our common stock reserved for future issuance under the ACELYRIN 2023 Plan as of December 31, 2025.

To the extent that options or warrants are exercised, new options or restricted stock units are issued under our equity incentive plans, or we issue additional shares of common stock in the future, there will be further dilution to investors participating in this offering.

TABLE OF CONTENTS

PLAN OF DISTRIBUTION

We have entered into a Sales Agreement with Cantor. Pursuant to this prospectus, we may offer and sell shares of our common stock having an aggregate gross sales price of up to $300,000,000 from time to time through Cantor acting as sales agent. A copy of the Sales Agreement has been filed as an exhibit to our annual report on Form 10-K for the year ended December 31, 2025 and is incorporated by reference into this prospectus.

Upon delivery of a placement notice and subject to the terms and conditions of the Sales Agreement, Cantor may sell shares of our common stock by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act. We may instruct Cantor not to sell common stock if the sales cannot be effected at or above the price designated by us from time to time. We or Cantor may suspend the offering of common stock upon notice and subject to other conditions.

We will pay Cantor commissions, in cash, for its service in acting as agent in the sale of our common stock. Cantor will be entitled to compensation at a commission rate of up to 3.0% of the sales price per share sold under the Sales Agreement. Because there is no minimum offering amount required as a condition to close this offering, the actual total public offering amount, commissions and proceeds to us, if any, are not determinable at this time. We have also agreed to reimburse Cantor for certain specified expenses, including the fees and disbursements of their legal counsel in an amount not to exceed $100,000 and certain ongoing expenses. We estimate that the total expenses for the offering, excluding compensation and reimbursements payable to Cantor under the terms of the Sales Agreement, will be approximately $550,000.

Settlement for sales of shares of our common stock will occur on the first trading day following the date on which any sales are made, or on some other date that is agreed upon by us and Cantor in connection with a particular transaction, in return for payment of the net proceeds to us. Sales of our common stock as contemplated in this prospectus will be settled through the facilities of The Depository Trust Company or by such other means as we and Cantor may agree upon. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

Cantor will use its commercially reasonable efforts, consistent with its sales and trading practices, to solicit offers to purchase the common stock under the terms and subject to the conditions set forth in the Sales Agreement. In connection with the sale of the common stock on our behalf, Cantor will be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of Cantor will be deemed to be underwriting commissions or discounts. We have agreed to provide indemnification and contribution to Cantor against certain civil liabilities, including liabilities under the Securities Act.

The offering of shares of our common stock pursuant to the Sales Agreement will terminate upon the termination of the Sales Agreement as permitted therein. We and Cantor may each terminate the Sales Agreement at any time upon ten days’ prior notice.

Cantor and its affiliates may in the future provide various investment banking, commercial banking and other financial services for us and our affiliates, for which services they may in the future receive customary fees. To the extent required by Regulation M, Cantor will not engage in any market making activities involving our common stock while the offering is ongoing under this prospectus.

This prospectus may be made available in electronic format on a website maintained by Cantor, and Cantor may distribute this prospectus electronically.

TABLE OF CONTENTS

LEGAL MATTERS

Cooley LLP, San Francisco, California, is serving as our counsel in this offering. Certain legal matters will be passed upon for Cantor by Latham & Watkins LLP, San Diego, California, in connection with the offering.

EXPERTS

WHERE YOU CAN FIND ADDITIONAL INFORMATION

This prospectus is part of the registration statement on Form S-3 we filed with the SEC under the Securities Act and does not contain all the information set forth in the registration statement. Whenever a reference is made in this prospectus to any of our contracts, agreements or other documents, the reference may not be complete and you should refer to the exhibits that are a part of the registration statement or the exhibits to the reports or other documents incorporated by reference into this prospectus for a copy of such contract, agreement or other document. Because we are subject to the information and reporting requirements of the Exchange Act, we file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC’s website at http://www.sec.gov. In addition, we maintain a website that contains information about us at https://www.alumis.com. The information found on, or otherwise accessible through our website is not incorporated by reference into, and does not form a part of, this prospectus or any other document or report we file or furnish with the SEC.

TABLE OF CONTENTS

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

•

our Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on March 19, 2026;

•

our Current Report on Form 8-K filed with the SEC on January 6, 2026 (to the extent the information in such report is filed and not furnished);

•

the unaudited pro forma condensed combined financial information included in Exhibit 99.1 to the registration statement of which this prospectus is a part; and

•

Alumis Inc.
Attn: Corporate Secretary
280 East Grand Avenue
South San Francisco, CA 94080
(650) 231-6625

TABLE OF CONTENTS

Up to $300,000,000

Common Stock

PROSPECTUS

Cantor

March 19, 2026

TABLE OF CONTENTS

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution

The following table sets forth an estimate of the fees and expenses, other than the underwriting discounts and commissions, payable by the registrant in connection with the issuance and distribution of the securities being registered.

	Amount
Securities and Exchange Commission registration fee		$	(1)
Financial Industry Regulatory Authority, Inc. filing fee			(2)
Stock exchange listing fees			(2)
Printing Expenses			(2)
Legal fees and expenses			(2)
Accounting fees and expenses			(2)
Blue Sky, qualification and expenses			(2)
Transfer agent fees and expenses			(2)
Trustee and depositary fees and expenses			(2)
Warrant agent fees and expenses			(2)
Miscellaneous			(2)
Total		$	(2)

(1)

Deferred pursuant to Rule 456(b) and Rule 457(r) of the Securities Act of 1933, as amended (the “Securities Act”), other than with respect to the SEC registration fees applicable to the offering of up to $300,000,000 of common stock pursuant to the sales agreement prospectus. Pursuant to Rule 457(p) under the Securities Act, the registrant’s previously paid filing fees in the amount of $8,412, based on the $54,942,500 of unsold securities under the registrant’s registration statement on Form S-3 (File No. 333-288510) that was terminated automatically upon filing of this registration statement on Form S-3, are being applied to offset the registration fees that are payable in connection with the registration of securities issuable pursuant to the sales agreement prospectus filed with this registration statement.

(2)

These fees and expenses are calculated based on the securities offered and the number of issuances and accordingly cannot be estimated at this time.

Item 15. Indemnification of Directors and Officers

We are incorporated under the laws of the State of Delaware. Section 145 of the Delaware General Corporation Law authorizes a court to award, or a corporation’s board of directors to grant, indemnity to directors and officers in terms sufficiently broad to permit such indemnification under certain circumstances for liabilities, including reimbursement for expenses incurred, arising under the Securities Act. Our amended and restated certificate of incorporation contains provisions limiting the liability of directors, and our amended and restated bylaws provides that we will indemnify each of our directors and officers to the fullest extent permitted under Delaware law. Our amended and restated certificate of incorporation and amended and restated bylaws also provide the Board with discretion to indemnify our employees and other agents when determined appropriate by the board of directors.

In addition, we have entered into an indemnification agreement with each of our directors and executive officers, which will require us to indemnify them. These agreements provide, among other things, that we will indemnify our executive officer or director, under the circumstances and to the extent provided for in the indemnification agreement, for expenses, damages, judgments, fines and settlements he or she may be required to pay in actions or proceedings which he or she is or may be made a party by reason of his or her position as a director, officer or other agent of us, and otherwise to the fullest extent permitted under Delaware law and our amended and restated bylaws. At present, there is no pending litigation or proceeding

II-1

TABLE OF CONTENTS

involving a director or executive officer of Alumis Inc. regarding which indemnification is sought, nor is the registrant aware of any threatened litigation that may result in claims for indemnification.

We maintain insurance policies that indemnify our directors and officers against various liabilities arising under the Securities Act and the Securities Exchange Act of 1934, as amended, that might be incurred by any director or officer in his capacity as such.

The underwriting agreement that we may enter into (Exhibit 1.1) may provide for indemnification by any underwriters of the Company, its directors, its officers who sign the registration statement and our controlling persons for some liabilities, including liabilities arising under the Securities Act.

Item 16. Exhibits

EXHIBIT INDEX

	Exhibit Number			Description
	1.1*			Form of Underwriting Agreement
	1.2			Controlled Equity OfferingSM Sales Agreement, dated March 18, 2026, by and between the Registrant and Cantor Fitzgerald & Co. (incorporated by reference to Exhibit 10.24 to the Registrant’s Annual Report on Form 10-K, filed with the SEC on March 19, 2026)
	2.1			Agreement and Plan of Merger, by and among the Registrant, ACELYRIN, Inc. and Arrow Merger Sub, Inc., dated as of February 6, 2025 (incorporated by reference to Exhibit 2.1 to the Registrant’s Current Report on Form 8-K, filed with the SEC on February 6, 2025)
	2.2			Amendment to the Agreement and Plan of Merger, by and among the Registrant, ACELYRIN, Inc. and Arrow Merger Sub, Inc., dated as of April 20, 2025 (incorporated by reference to Exhibit 2.1 to the Registrant’s Current Report on Form 8-K, filed with the SEC on April 21, 2025)
	3.1			Amended and Restated Certificate of Incorporation of the Registrant (incorporated by reference to Exhibit 3.1 to the Registrant’s Current Report on Form 8-K, filed with the SEC on July 1, 2024)
	3.2			Amended and Restated Bylaws of the Registrant (incorporated by reference to Exhibit 3.2 to the Registrant’s Current Report on Form 8-K, filed with the SEC on July 1, 2024)
	4.1			Amended and Restated Investors’ Rights Agreement, by and among the Registrant and certain of its stockholders, dated March 4, 2024 (incorporated by reference to Exhibit 4.2 to the Registrant’s Registration Statement on Form S-1 (File No. 333-280068), filed with the SEC on June 7, 2024)
	4.2			Form of Common Stock Certificate (incorporated by reference to Exhibit 4.1 to the Registrant’s Registration Statement on Form S-1/A (File No. 333-280068), filed with the SEC on June 24, 2024)
	4.3*			Specimen Preferred Stock Certificate and Form of Certificate of Designation of Preferred Stock
	4.4+			Form of Debt Indenture
	4.5*			Form of Debt Securities
	4.6+			Form of Common Stock Warrant Agreement and Warrant Certificate
	4.7+			Form of Preferred Stock Warrant Agreement and Warrant Certificate
	4.8+			Form of Debt Securities Warrant Agreement and Warrant Certificate
	5.1+			Opinion of Cooley LLP
	23.1+			Consent of PricewaterhouseCoopers LLP, independent registered public accounting firm of Alumis Inc.
	23.2+			Consent of PricewaterhouseCoopers LLP, independent registered public accounting firm of ACELYRIN, Inc.
	23.3+			Consent of Cooley LLP (included in Exhibit 5.1)
	24.1+			Power of Attorney (incorporated by reference to the signature page hereto)

II-2

TABLE OF CONTENTS

	Exhibit Number			Description
	25.1**			Statement of Eligibility on Form T-1 under the Trust Indenture Act of 1939, of the Trustee under the Debt Indenture (to be filed separately under the electronic form type 305B2, if applicable)
	99.1+			Unaudited pro forma condensed combined financial information.
	107+			Filing Fee Table

Filed herewith.

To be filed by amendment or as an exhibit to a Current Report on Form 8-K and incorporated herein by reference, if applicable.

To be filed in accordance with the requirements of Section 305(b)(2) of the Trust Indenture Act of 1939 and Rule 5b-3 thereunder.

†

Certain schedules and exhibits to this exhibit have been omitted pursuant to Item 601(a)(5) of Regulation S-K. A copy of any omitted schedule and/or exhibit will be furnished to the SEC upon request.

Item 17. Undertakings

The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) to include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii) to reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii) to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

provided, however, that the undertakings set forth in paragraphs (1)(i), (1)(ii) and (1)(iii) above do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the registrant pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in this registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of this registration statement.

(2) That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4) That, for the purpose of determining liability under the Securities Act to any purchaser:

(i) Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

II-3

TABLE OF CONTENTS

(ii) Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii), or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5) That, for the purpose of determining liability of the registrant under the Securities Act to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(6) That, for purposes of determining any liability under the Securities Act, each filing of the registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(7) To file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act in accordance with the rules and regulations prescribed by the Commission under Section 305(b)(2) of the Trust Indenture Act.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

II-4

TABLE OF CONTENTS

SIGNATURES

Pursuant to the requirements of the Securities Act, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of South San Francisco, State of California, on this 19th day of March, 2026.

				ALUMIS INC.
				By:			/s/ Martin Babler Martin Babler Chief Executive Officer

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Martin Babler and John Schroer, and each of them, as true and lawful attorneys-in-fact and agents, each with the full powers of substitution and resubstitution, for them and in their name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this registration statement, and generally to do all such things in their names and behalf in their capacities as officers and directors to enable Alumis Inc. to comply with the provisions of the Securities Act, and all requirements of the SEC, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as he might or could do in person, ratifying and confirming all that said attorneys-in-fact and agents, or any of them, or their or his substitutes or substitute, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act, the registration statement has been signed by the following persons in the capacities and on the dates indicated.

Signatures	Title	Date
/s/ Martin Babler Martin Babler	President, Chief Executive Officer and Director (Principal Executive Officer)	March 19, 2026
/s/ John Schroer John Schroer	Chief Financial Officer (Principal Financial Officer and Principal Accounting Officer)	March 19, 2026
/s/ Srinivas Akkaraju, M.D., Ph.D. Srinivas Akkaraju, M.D., Ph.D.	Director	March 19, 2026
/s/ Alan B. Colowick, M.D., M.P.H. Alan B. Colowick, M.D., M.P.H.	Director	March 19, 2026
/s/ Patrick Machado, J.D. Patrick Machado, J.D.	Director	March 19, 2026
/s/ Sapna Srivastava, Ph.D. Sapna Srivastava, Ph.D.	Director	March 19, 2026
/s/ James B. Tananbaum, M.D. James B. Tananbaum, M.D.	Director	March 19, 2026

II-5

TABLE OF CONTENTS

Signatures	Title	Date
/s/ Lynn Tetrault, J.D. Lynn Tetrault, J.D.	Director	March 19, 2026
/s/ Zhengbin Yao, Ph.D. Zhengbin Yao, Ph.D.	Director	March 19, 2026

II-6

Source: View Original Filing on SEC EDGAR

[S-3ASR] ALUMIS INC. SEC Filing

Rhea-AI Filing Summary

Positive

Negative

Insights

NASDAQ:ALMS

ALMS Rankings

ALMS Latest News

ALMS Latest SEC Filings

ALMS Stock Data

Trending News

[S-3ASR] ALUMIS INC. SEC Filing

Rhea-AI Filing Summary

Positive

Negative

Insights

Capital Markets Attorney neutral

Equity Capital Markets Specialist neutral

NASDAQ:ALMS

ALMS Rankings

ALMS Latest News

ALMS Latest SEC Filings

ALMS Stock Data