Avalo Therapeutics (NASDAQ: AVTX) files to register 128,189 shares for selling stockholders

Rhea-AI Filing Summary

Avalo Therapeutics, Inc. has filed a resale registration covering up to 128,189 shares of common stock held by former AlmataBio, Inc. stockholders. These shares were issued under a Milestone Buyout Option Agreement and Amendment to the merger agreement with AlmataBio.

The registration enables the selling stockholders to sell their shares from time to time; Avalo is not selling any shares and will not receive proceeds from these resales, though it will bear registration expenses. The shares may be sold through various methods at prices based on the market price of Avalo’s Nasdaq‑listed stock (symbol AVTX; last reported price $17.88 per share on July 16, 2026).

Avalo is a clinical‑stage biotechnology company focused on IL‑1β‑targeted therapies. Its lead antibody, abdakibart (AVTX‑009), met the primary endpoint in the Phase 2 LOTUS trial in hidradenitis suppurativa, with 253 adults enrolled and statistically significant HiSCR75 responses at both doses. Based on these data, the company plans to advance abdakibart into a registrational Phase 3 program.

Filing Explained

Resale access is registered but not yet effective; Avalo receives no sale proceeds and does not issue additional shares in this filing.

On July 17, 2026, Avalo Therapeutics filed a Form S-3 to register resale of up to 128,189 already-issued common shares held by former AlmataBio stockholders. Although the cover labels the shares “offered,” the preliminary prospectus says this filing is not an offer to sell and the holders cannot sell until the registration statement is effective. The immediate structural change is resale registration access, not a new Avalo share issuance or proceeds to Avalo; the company will pay registration expenses.

The supplied S-3 definition distinguishes registration capacity from an actual sale. In this filing, the selling holders—not Avalo—choose whether, when, and how to dispose of the registered shares, and the filing does not establish that any shares have been sold.

The selling-stockholder table uses 52,902,989 outstanding common shares as of July 10, 2026 and assumes, for its after-offering column, that all registered shares are sold; it also shows the holders’ corresponding remaining positions under that assumption.

The next state-changing document is the effectiveness of this registration statement. If a selling holder later enters a material arrangement with a broker-dealer, the filing says a Rule 424(b) prospectus supplement will disclose the arrangement and transaction terms.

Key Figures

Shares registered for resale: 128,189 shares of common stock Shares outstanding: 52,902,989 shares of common stock Last reported AVTX share price: $17.88 per share +4 more

7 metrics

Shares registered for resale 128,189 shares of common stock Up to 128,189 shares offered by selling stockholders under this prospectus

Shares outstanding 52,902,989 shares of common stock Shares outstanding as of July 10, 2026

Last reported AVTX share price $17.88 per share Closing price on The Nasdaq Capital Market on July 16, 2026

SEC registration fee $327.86 Estimated SEC fee for this registration

Total offering expenses $115,327.86 Legal, accounting, printing and SEC fee for the registration

LOTUS trial enrollment 253 adults Randomized, double‑blind, placebo‑controlled Phase 2 hidradenitis suppurativa trial of abdakibart

HiSCR75 response improvement 42.2%, 42.9% vs 25.6% Absolute HiSCR75 response at Week 16 for 150mg and 300mg doses vs placebo in LOTUS

Key Terms

Milestone Buyout Amendment Agreement, Hidradenitis Suppurativa Clinical Response (HiSCR75), smaller reporting company, Regulation M, +2 more

6 terms

Milestone Buyout Amendment Agreement financial

"pursuant to the Milestone Buyout Amendment Agreement"

Hidradenitis Suppurativa Clinical Response (HiSCR75) medical

"primary efficacy endpoint was the proportion of patients achieving Hidradenitis Suppurativa Clinical Response (HiSCR75)"

smaller reporting company regulatory

"We are a “smaller reporting company” as defined under Rule 405 of the Securities Act."

A smaller reporting company is a publicly traded firm that meets regulatory size tests allowing it to provide abbreviated financial disclosures and compliance filings compared with larger companies. For investors, that means financial statements and notes may be less detailed, which can make it harder to compare performance or spot risks—think of reading a short summary instead of a full report when deciding whether to buy or hold a stock.

Regulation M regulatory

"subject to applicable provisions of the Exchange Act and the rules and regulations thereunder, including, without limitation, to the extent applicable, Regulation M"

beneficial ownership financial

"Beneficial ownership is determined in accordance with Rule 13d-3(d)"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

interleukin-1β (IL-1β) pathway medical

"developing therapeutics targeting the interleukin-1β (“IL-1β”) pathway"

Offering Details

resale/secondary

Offering

Offering Type resale/secondary

Use of Proceeds We will not receive any proceeds from the resale of common stock by the selling stockholders pursuant to this prospectus.

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Available on EDGAR 07/17/2026 - 04:02 PM Accepted by SEC EDGAR 07/17/2026 - 04:01 PM Learn about SEC filing dates

FAQ

What is Avalo Therapeutics (AVTX) registering in this resale filing?

Avalo is registering 128,189 shares of common stock for resale by selling stockholders who are former AlmataBio, Inc. stockholders. The company is not issuing new shares in this registration.

Does Avalo Therapeutics (AVTX) receive any proceeds from this offering?

No. All proceeds from sales of the 128,189 registered shares will go to the selling stockholders. Avalo will only pay the registration-related expenses, not underwriting commissions or sale proceeds.

How did the selling stockholders of AVTX obtain the 128,189 shares?

The shares were issued to certain former stockholders of AlmataBio, Inc. under a Milestone Buyout Option Agreement and Amendment to the merger agreement dated April 26, 2026, following Avalo’s acquisition structure.

What are the key Phase 2 LOTUS trial results for Avalo Therapeutics (AVTX)?

In the Phase 2 LOTUS trial with 253 adults with hidradenitis suppurativa, abdakibart met the HiSCR75 primary endpoint at both doses, showing 42.2% and 42.9% response versus 25.6% for placebo at Week 16.

How might the registered AVTX shares affect existing shareholders?

The filing allows resale of 128,189 shares relative to 52,902,989 shares outstanding as of July 10, 2026. The company notes that future sales or perceived sales could pressure its stock price.

What is Avalo Therapeutics’ (AVTX) business focus?

Avalo is a clinical stage biotechnology company focused on therapeutics targeting the interleukin‑1β (IL‑1β) pathway for immune‑mediated inflammatory diseases, led by its antibody abdakibart (AVTX‑009) and preclinical candidate AVTX‑010.

What is the latest reported market price for AVTX common stock?

Avalo reports that on July 16, 2026, the last reported sale price of its common stock on The Nasdaq Capital Market was $17.88 per share, which may guide pricing of any resale transactions.

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As filed with the Securities and Exchange Commission on July 17, 2026

Registration Statement No. 333-     ​

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

FORM S-3

REGISTRATION STATEMENT UNDER
THE SECURITIES ACT OF 1933​

AVALO THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)​

​ Delaware (State or other jurisdiction
of incorporation or organization)​ ​ ​ 45-0705648 (I.R.S. Employer
Identification Number) ​

1500 Liberty Ridge Drive, Suite 321
Wayne, Pennsylvania 19087
Telephone: (410) 522-8707

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

Christopher Sullivan
Chief Financial Officer
Avalo Therapeutics, Inc.
1500 Liberty Ridge Drive, Suite 321
Wayne, Pennsylvania 19087
Telephone: (410) 522-8707

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

Copies to:

Rachael Bushey
Jennifer Porter
Goodwin Procter LLP
3025 John F Kennedy Blvd
Philadelphia, PA 19104
Telephone: (445) 207-7800

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, 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 Securities Act.   ☐

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The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment that specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

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The information in this prospectus is not complete and may be changed. The selling stockholders may not sell these securities or accept an offer to buy these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities, and the selling stockholders are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to completion, dated July 17, 2026

PRELIMINARY PROSPECTUS

Up to 128,189 Shares of Common Stock Offered by Selling Stockholders

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This prospectus relates to the sale or other disposition from time to time of up to 128,189 shares of our common stock, $0.001 par value per share, all held by the selling stockholders named in this prospectus, including their transferees, pledgees, donees or successors. We are not selling any shares of common stock under this prospectus and will not receive any of the proceeds from the sale of such securities by the selling stockholders.

The shares of common stock were issued to the certain former stockholders of AlmataBio, Inc. (“AlmataBio”) in connection with that certain Milestone Buyout Option Agreement and Amendment to the Agreement and Plan of Merger and Reorganization, dated as of April 26, 2026, by and among us and the securityholders’ representative, solely in his capacity as the representative agent and attorney-in-fact of former stockholders of AlmataBio (the “Milestone Buyout Amendment Agreement”).

The selling stockholders may sell or otherwise dispose of the common stock covered by this prospectus in a number of different ways and at varying prices derived from the prevailing market price of our common stock at the time of any such sale. We provide more information about how the selling stockholders may sell or otherwise dispose of their securities in the section entitled “Plan of Distribution” beginning on page 13. The selling stockholders will pay all brokerage fees and commissions and similar expenses. We will pay all expenses (except brokerage fees and commissions and similar expenses) relating to the registration of the securities with the Securities and Exchange Commission. No underwriter or other person has been engaged to facilitate the sale of the securities in this offering.

Our common stock is traded on The Nasdaq Capital Market under the symbol “AVTX.” On July 16, 2026, the last reported sale price of our common stock was $17.88 per share. We recommend that you obtain current market quotations for our common stock prior to making an investment decision.

Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on page 7 of this prospectus and in the documents incorporated by reference herein, to read about factors you should consider before investing in our securities.

We are a “smaller reporting company” under the federal securities laws and, as such, we have elected to comply with certain reduced public company reporting requirements for this prospectus and for future filings. See “Prospectus Summary — Implications of Being a Smaller Reporting Company.”

Neither the Securities and Exchange Commission nor any other regulatory body has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

Prospectus dated            , 2026

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​	​	​	Page				​
ABOUT THIS PROSPECTUS	​	​	​	​	1	​	​
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS	​	​	​	​	2	​	​
PROSPECTUS SUMMARY	​	​	​	​	4	​	​
THE OFFERING	​	​	​	​	6	​	​
RISK FACTORS	​	​	​	​	7	​	​
USE OF PROCEEDS	​	​	​	​	10	​	​
SELLING STOCKHOLDERS	​	​	​	​	11	​	​
PLAN OF DISTRIBUTION	​	​	​	​	13	​	​
DESCRIPTION OF SECURITIES TO BE REGISTERED	​	​	​	​	16	​	​
LEGAL MATTERS	​	​	​	​	17	​	​
EXPERTS	​	​	​	​	17	​	​
WHERE YOU CAN FIND MORE INFORMATION	​	​	​	​	17	​	​
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE	​	​	​	​	17	​	​

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ABOUT THIS PROSPECTUS

You should rely only on the information that we have provided or incorporated by reference in this prospectus and any prospectus supplement that we may authorize to be provided to you. We have not, and the selling stockholders have not, authorized anyone to provide you with different information. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus or any prospectus supplement that we may authorize to be provided to you. If anyone provides you with different or inconsistent information, you should not rely on it. You should assume that the information in this prospectus and any prospectus supplement or incorporated herein or therein is accurate only as of the date on the cover of such document, regardless of the time of delivery of this prospectus or any prospectus supplement or any sale of a security. Our business, financial condition, results of operations and prospects may have changed since those dates.

We urge you to carefully read this prospectus and any prospectus supplement, together with the information incorporated herein or therein by reference as described under the heading “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.”

This prospectus contains 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 or are 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 below under the heading “Where You Can Find Additional Information.”

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the information incorporated by reference in this prospectus include “forward-looking statements” within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, (the “Exchange Act”), and Section 27A of the Securities Act of 1933, as amended (the “Securities Act”). For these purposes, any statements contained or incorporated by reference herein regarding our strategy, future operations, financial position, future revenues, projected costs, prospects, plans and objectives of management, other than statements of historical facts, are forward-looking statements. In some cases, forward-looking statements can be identified by the use of forward-looking words such as “believes,” “expects,” “may,” “will,” “plans,” “intends,” “estimates,” “could,” “should,” “would,” “continue,” “seeks,” “aims,” “projects,” “predicts,” “pro forma,” “anticipates,” “potential” or other similar words (including their use in the negative), or by discussions of future matters such as: the development of product candidates or products, timing and success of trial results and regulatory review, potential attributes and benefits of product candidates, the expansion of our drug portfolio, and other statements that are not historical. We cannot guarantee that we actually will achieve the plans, intentions or expectations expressed or implied in our forward-looking statements. There are a number of important factors that could cause actual results, levels of activity, performance or events to differ materially from those expressed or implied in the forward-looking statements we make.

These statements are based upon the current beliefs and expectations of our management but are subject to significant risks and uncertainties, including:

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the results of our clinical studies, including additional data from our Phase 2 LOTUS trial of abdakibart (AVTX-009) and our plans to advance abdakibart in hidradenitis suppurativa (“HS”) through Phase 3 trials;

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our success in identifying and executing a development program for our preclinical product candidates, including AVTX-010 and identifying additional product candidates from our preclinical programs and research pipeline;

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drug development costs, timing and other risks, including reliance on investigators and enrollment of patients in clinical trials;

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our ability to advance any product candidates through applicable regulatory approval processes;

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our cash position and the need to raise additional capital in the future;

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reliance on key personnel;

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regulatory risks;

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general economic and market risks and uncertainties, including those caused by military conflicts, trade barriers, or governmental budget dynamics; and

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those other risks detailed in our filings with the SEC.

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Examples of risks and uncertainties that could cause actual results to differ materially from historical performance and any forward-looking statements include, but are not limited to, the risks described under the heading “Risk Factors” on page 7 of this prospectus, in our most recent Annual Report on Form 10-K, and subsequent reports filed with the Securities and Exchange Commission (the “SEC”). Moreover, we operate in a very competitive and rapidly changing environment. New risks emerge from time to time. It is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make trends discussed in this prospectus supplement and accompanying prospectus might not occur and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements. Given these risks, uncertainties and other factors, many of which are beyond our control, we cannot assure you that the forward-looking statements in this prospectus will prove to be accurate, and you should not place undue reliance on these forward-looking 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 timeframe, or at all.

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Any forward-looking statement speaks only as of the date on which it is made. Although we may elect to update forward-looking statements in the future, we specifically disclaim any obligation to do so, except as may be required by law, even if our estimates change, and readers should not rely on our forward-looking statements as representing our views as of any date subsequent to the date the statements were made. All forward-looking statements are qualified in their entirety by this cautionary statement.

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PROSPECTUS SUMMARY

This summary highlights selected information from this prospectus and does not contain all of the information that you need to consider in making your investment decision. You should carefully read this entire prospectus and any prospectus supplement, including the risks of investing in our securities discussed under the heading “Risk Factors” contained in this prospectus and any prospectus supplement, and under similar headings in the other documents that are incorporated by reference into this prospectus or any prospectus supplement. 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 indicates otherwise, references in this prospectus to “Avalo,” “Company,” “we,” “us” and “our” refer to Avalo Therapeutics, Inc. and its subsidiaries unless the context indicates otherwise.

Company Overview

We are a clinical stage biotechnology company fully dedicated to developing therapeutics targeting the interleukin-1β (“IL-1β”) pathway for immune-mediated inflammatory diseases. Our lead product candidate, abdakibart (AVTX-009), is an anti-IL-1β monoclonal antibody (“mAb”). Positive topline data was recently reported for abdakibart in a Phase 2 clinical trial in HS. In addition to HS, we are also exploring additional opportunities to make an impact in prevalent indications that have significant remaining unmet needs. We are also advancing AVTX-010, a long-acting net generation anti-IL-1β mAb designed to extend dosing intervals and build upon the differentiated profile established by abdakibart.

Abdakibart is a high affinity, highly potent humanized IgG mAb designed to specifically inhibit IL-1β and block downstream inflammatory pathways. Abdakibart is a humanized monoclonal antibody (IgG4) that binds to IL-1β with high affinity and neutralizes its activity. IL-1β is a pro-inflammatory cytokine that plays a central role in the pathogenesis of a wide range of human diseases. It activates immune cells that generate proinflammatory cytokines, including IL-6, TNF-α, and IL-17. Dysregulated IL-1β signaling is a major driver of inflammation, contributing to the progression of autoimmune disorders. IL-1β inhibition has proven effective in multiple immune-mediated inflammatory diseases.

The LOTUS trial (NCT06603077), which enrolled 253 adults, was a randomized, double-blind, placebo-controlled parallel-group Phase 2 trial to evaluate the efficacy, safety and tolerability of abdakibart across two dose regimens and placebo in a 1:1:1 ratio over a 16-week treatment period. Subjects received either a 600mg loading dose of abdakibart followed by 300mg every four weeks or a 300mg loading dose followed by 150mg every two weeks. The trial’s primary efficacy endpoint was the proportion of patients achieving Hidradenitis Suppurativa Clinical Response (HiSCR75) at Week 16. The Phase 2 LOTUS trial successfully met its primary endpoint at both doses studied (p=0.018 150mg, p=0.015 300mg and p=0.004 combined), demonstrating a 42.2% and 42.9% absolute improvement in HiSCR75 response rates at Week 16, respectively (42.5% combined, placebo rate 25.6%). This was the highest absolute improvement in HiSCR75 and HiSCR50 in clinical trials of this size or larger at each individual dose and on a combined dose basis. Abdakibart regimens also demonstrated statistically significant benefit across the key secondary endpoints in HiSCR50, change in IHS4 and change in draining tunnel count. Numerically favorable responder rates were observed across all other key secondary endpoints. The HiSCR75 response was similar in patients with and without prior biologic exposure. Based on these data, we plan to advance abdakibart into a registrational phase 3 program.

Management’s primary evaluation of our success is the ability to progress its programs towards commercialization or opportunistically out-licensing rights to indications or geographies. We believe the ability to achieve the anticipated milestone as presented in the following chart represents our most immediate evaluation point as to the progress of our goal to move our pipeline forward.

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Corporate Information

Our principal executive offices are located at 1500 Liberty Ridge Drive, Suite 321, Wayne, Pennsylvania 19087 and our telephone number is (410) 522-8707. Our website address is www.avalotx.com. Our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to reports filed pursuant to Sections 13(a) and 15(d) of the Exchange Act, will be made available free of charge on our website as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. The contents of our website are not incorporated into this prospectus supplement and our reference to the URL for our website is intended to be an inactive textual reference only.

The trademarks, trade names and service marks appearing in this prospectus supplement are the property of their respective owners. We do not intend our use or display of other companies’ trademarks, trade names or service marks to imply a relationship with, or endorsement or sponsorship of us by, any other companies or products.

Implications of Being a Smaller Reporting Company

We are a “smaller reporting company” as defined under Rule 405 of the Securities Act. We may continue to be a smaller reporting company if either (i) the market value of our stock held by non-affiliates was less than $250 million on the last business day of our most recently completed second fiscal quarter or (ii) our annual revenue was less than $100 million during the most recently completed fiscal year and the market value of our stock held by non-affiliates was less than $700 million on the last business day of our most recently completed second fiscal quarter. For so long as we remain a smaller reporting company, we are permitted and plan to rely on exemptions from certain disclosure and other requirements that are applicable to other public companies that are not smaller reporting companies.

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THE OFFERING

Common Stock Offered by Selling Stockholders

Up to 128,189 shares of common stock.

These shares have been issued to selling stockholders, who are certain former stockholders of AlmataBio, pursuant to the Milestone Buyout Amendment Agreement.

Terms of the offering

The selling stockholders will determine when and how it will dispose of any shares of our Common Stock that are registered under this prospectus for resale. See “Plan of Distribution.”

Use of proceeds

We will not receive any proceeds from the resale of common stock by the selling stockholders pursuant to this prospectus. See “Use of Proceeds” and “Risk Factors” for additional information.

Dividend Policy

We have never paid dividends on our capital stock and do not anticipate paying any dividends for the foreseeable future.

Common stock Nasdaq Capital Market Symbol

“AVTX.”

Risk factors

Investing in our securities involves a high degree of risk. Please read the information contained under the heading “Risk Factors” on page 7 of this prospectus and in any report incorporated by reference herein.

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RISK FACTORS

Investing in our securities involves a high degree of risk. Before deciding to purchase our common stock, you should consider carefully the risks and uncertainties described below together with the other information included in this prospectus and the risk factors described in the heading “Risk Factors” in our most recent Annual Report on Form 10-K, as may be amended or supplemented by our subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K that are incorporated by reference herein. These risks and uncertainties are not the only risks and uncertainties we face. Additional risks and uncertainties not currently known to us, or that we currently view as immaterial, may also impair our business. If any of the risks or uncertainties described in our SEC filings or any additional risks and uncertainties actually occur, our business, financial condition, results of operations and cash flow could be materially and adversely affected. In that case, the trading price of our common stock could decline and you might lose all or part of your investment. Certain statements below are forward-looking statements. See the information included under the heading “Special Note Regarding Forward-Looking Statements.”

Risks Related to this Offering

Future sales of our common stock or securities convertible into or exercisable for shares of our common stock following this offering, or the perception that such future sales may occur, may cause our stock price to decline.

In this prospectus, up to 128,189 shares of common stock may be sold from time to time by the selling stockholders. The sale of a substantial number of shares of our securities in the public market, or the perception that such sales may occur, could adversely affect the price of our common stock on the Nasdaq Capital Market and could cause the market price of our common stock to decline. We cannot predict the effect, if any, that market sales of those shares of common stock or the availability of those shares of common stock for sale will have on the market price of our common stock. A substantial majority of the outstanding shares of our common stock are, and the shares of common stock sold pursuant to this prospectus, upon issuance will be, freely tradable without restriction or further registration under the Securities Act.

In addition, in the future, we may also issue shares of our common stock in connection with investments or acquisitions. The amount of shares of our common stock issued in connection with an investment or acquisition could substantially increase our shares of common stock outstanding, which could adversely affect the price of our common stock on the Nasdaq Capital Market.

We do not expect to pay dividends in the foreseeable future. As a result, you must rely on stock appreciation for any return on your investment.

We do not anticipate paying cash dividends on our common stock in the foreseeable future. Any payment of cash dividends will also depend on our financial condition, results of operations, capital requirements and other factors and will be at the discretion of our board of directors. Accordingly, you will have to rely on capital appreciation, if any, to earn a return on your investment in our common stock. Any determination to pay dividends in the future will be at the discretion of our board of directors and will depend upon results of operations, financial condition, contractual restrictions, restrictions imposed by applicable law and other factors our board of directors deems relevant. Furthermore, we may in the future become subject to additional contractual restrictions on, or prohibitions against, the payment of dividends.

The price of our common stock could be subject to rapid and substantial volatility. Such volatility, including any stock run-ups, may be unrelated to our actual or expected operating performance and financial condition or prospects, making it difficult for prospective investors to assess the rapidly changing value of our common stock. Volatility in our common stock price may subject us to securities litigation or regulatory scrutiny.

The market for our common stock may have, when compared to seasoned issuers, significant price volatility and we expect that the price of our shares of common stock may continue to be more volatile than that of a seasoned issuer for the indefinite future. As a relatively small-capitalization company with a relatively small public float, we may experience greater share price volatility, extreme price run-ups, lower trading volume, and less liquidity than large-capitalization companies. In particular, our common stock may be subject to rapid and substantial price volatility, low volumes of trades, heightened price sensitivity to

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individual transactions, and large spreads in bid and ask prices. The market price for our common stock may be influenced by many factors, including:

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results of our clinical trials, including topline or preliminary data and preclinical studies, and the results of trials of our competitors or those of other companies in our market sector;

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our ability to enroll patients in our future clinical trials;

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our ability to obtain and maintain regulatory approval of any of our current or future product candidates or additional indications thereof, including the timing, scope and conditions of such approvals or limitations to specific label indications or patient populations for its use, or changes or delays in the regulatory review process;

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regulatory or legal developments in the United States and foreign countries;

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changes in the structure of healthcare payment systems;

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the success or failure of our efforts to develop, acquire, or license any of our current or future product candidates;

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innovations, clinical trial results, product approvals and other developments regarding our competitors;

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announcements by us or our competitors of significant acquisitions, strategic partnerships, joint ventures, or capital commitments;

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•

manufacturing, supply, or distribution delays or shortages;

​

•

any changes to our relationship with any manufacturers, suppliers, collaborators or other strategic partners;

​

•

achievement of expected product sales and profitability or failure to achieve anticipated milestones;

​

•

variations in our financial results or development timelines or those of companies that are perceived to be similar to us, including variations from expectations of securities analysts or investors;

​

•

market conditions in the biopharmaceutical sector and issuance of securities analysts’ reports or recommendations;

​

•

trading volume of our common stock;

​

•

an inability to obtain additional funding on acceptable terms, or at all;

​

•

sales of our stock by us, our insiders or our stockholders, as well as the anticipation of lock-up releases or expiration of market stand-off or lock-up agreements;

​

•

general economic, industry, geopolitical and market conditions, such as military conflict or war, inflation and financial institution instability, or pandemic or epidemic disease outbreaks, many of which are beyond our control;

​

•

additions or departures of senior management, directors or key personnel;

​

•

intellectual property, product liability or other litigation against us or our inability to enforce our intellectual property;

​

•

changes in our capital structure, such as future issuances of securities and the incurrence of additional debt; and

​

•

changes in accounting standards, policies, guidelines, interpretations or principles or their application to our business.

​

The realization of any of the above risks or any of a broad range of other risks, including those described in this “Risk Factors” section, could have a dramatic and adverse impact on the market price of our common stock. Such volatility, including any stock run-ups, may be unrelated to our actual or expected operating performance and financial condition or prospects, making it difficult for prospective investors to assess the rapidly changing value of our common stock. As a result of this volatility, investors may experience losses on their investment in our securities. A decline in the market price of our common stock also

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could adversely affect our ability to issue additional common stock or other securities and our ability to obtain additional financing in the future on favorable terms.

In addition, if the trading volumes of our common stock are low, persons buying or selling in relatively small quantities may easily influence the price of our common stock over short or extended periods of time. This low volume of trades could also cause the price of our common stock to fluctuate greatly, with large percentage changes in price occurring in any trading day session. Holders of our common stock may also not be able to readily liquidate their investment or may be forced to sell at depressed prices due to low volume trading. No assurance can be given that a higher volume active market in our common stock will develop or be sustained. If a higher volume active market does not develop, holders of our common stock may be unable to readily sell the shares they hold or may not be able to sell their shares at all.

In addition, in the past, plaintiffs have often initiated securities class action litigation against a company following periods of volatility in the market price of its securities. We may, in the future, be the target of similar litigation regardless of the merits of such claims. Securities litigation could result in substantial costs and liabilities to us and could divert our management’s attention and resources.

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USE OF PROCEEDS

Up to 128,189 shares of our common stock are being offered for resale by the selling stockholders and will be sold for the accounts of the selling stockholders named in this prospectus. As a result, all proceeds from the sales of such securities offered for resale hereby will go to the selling stockholders and we will not receive any proceeds from the resale of those securities by the selling stockholders.

We will incur all costs associated with this registration statement and prospectus.

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SELLING STOCKHOLDERS

The following table sets forth certain information regarding the selling stockholders and the shares of common stock beneficially owned by them, which information is available to us as of July 10, 2026. The selling stockholders may offer the shares of common stock under this prospectus from time to time. However, for the purposes of the table below, we have assumed that, after completion of the offering, none of the securities covered by this prospectus will be held by the selling stockholders. In addition, a selling stockholder may have sold, transferred or otherwise disposed of all or a portion of that holder’s shares of common stock since the date on which the selling stockholder provided information for this table. We have not made independent inquiries about such transfers or dispositions. See the section entitled “Plan of Distribution” beginning on page 13.

Beneficial ownership is determined in accordance with Rule 13d-3(d) promulgated by the SEC under the Exchange Act. The percentage of shares beneficially owned prior to the offering is based on 52,902,989 shares of our common stock outstanding as of July 10, 2026.

Name

​

​

Number of shares of common stock beneficially owned prior to offering

​

​

Number of shares of common stock registered for sale hereby

​

​

Number of shares of common stock beneficially owned after offering

​

​

Percentage of common stock beneficially owned after offering

​

Boothbay Absolute Return Strategies, LP(1)

​

​

​

​

18,071

​

​

​

​

​

4,379

​

​

​

​

​

13,692

​

​

​

​

​

*

​

​

Boothbay Diversified Alpha Master Fund, LP(2)

​

​

​

​

6,873

​

​

​

​

​

2,301

​

​

​

​

​

4,572

​

​

​

​

​

*

​

​

Emerald Bioventures, LLC(3)

​

​

​

​

43,576

​

​

​

​

​

43,576

​

​

​

​

​

—

​

​

​

​

​

*

​

​

Emily Nixon(4)

​

​

​

​

301

​

​

​

​

​

301

​

​

​

​

​

—

​

​

​

​

​

*

​

​

Ikarian Healthcare Master Fund, LP(5)

​

​

​

​

65,239

​

​

​

​

​

28,180

​

​

​

​

​

37,059

​

​

​

​

​

*

​

​

Justin DiMartino(6)

​

​

​

​

16,035

​

​

​

​

​

15,519

​

​

​

​

​

516

​

​

​

​

​

*

​

​

Mellisa Huhn(7)

​

​

​

​

9,641

​

​

​

​

​

478

​

​

​

​

​

9,163

​

​

​

​

​

*

​

​

Naveen Daryani(8)

​

​

​

​

377

​

​

​

​

​

377

​

​

​

​

​

—

​

​

​

​

​

*

​

​

Navneet Kumar(9)

​

​

​

​

452

​

​

​

​

​

452

​

​

​

​

​

—

​

​

​

​

​

*

​

​

Patrick J. Crutcher(10)

​

​

​

​

27,239

​

​

​

​

​

27,239

​

​

​

​

​

—

​

​

​

​

​

*

​

​

Tatyana Touzova(11)

​

​

​

​

5,387

​

​

​

​

​

5,387

​

​

​

​

​

—

​

​

​

​

​

*

​

​

​

*

Represents beneficial ownership of less than one percent of the outstanding shares of our common stock.

​

(1)

Consists of 4,379 shares of common stock being offered by Boothbay Absolute Return Strategies, LP (“BBARS”) pursuant to this prospectus. Boothbay Fund Management, LLC (“Boothbay”) manages multi-manager fund vehicles, including BBARS. Boothbay, in its capacity as the investment manager of BBARS, has appointed Ikarian Capital, LLC (“Ikarian”) as a sub-advisor with shared voting and dispositive power over a portion of the securities of BBARS. Neil Shahrestani is the sole manager and a member of Ikarian and, in such capacities, may be deemed to share voting and dispositive power over such securities. The business address of BBARS is 140 East 45th Street, 16th Floor, New York, NY 10017, and the business address of Ikarian is 100 Crescent Court, Suite 1620, Dallas, TX 75201.

​

(2)

Consists of 2,301 shares of common stock being offered by Boothbay Diversified Alpha Master Fund, LP (“BBDAMF”) pursuant to this prospectus. Boothbay manages multi-manager fund vehicles, including BBDAMF. Boothbay, in its capacity as the investment manager of BBDAMF, has appointed Ikarian as a sub-advisor with shared voting and dispositive power over a portion of the securities of BBDAMF. Neil Shahrestani is the sole manager and a member of Ikarian and, in such capacities, may be deemed to share voting and dispositive power over such securities. The business address of BBDAMF is 140 East 45th Street, 16th Floor, New York, NY 10017, and the business address of Ikarian is 100 Crescent Court, Suite 1620, Dallas, TX 75201.

​

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(3)

Consists of 43,576 shares of common stock being offered by Emerald Bioventures, LLC pursuant to this prospectus. Tim Opler may be deemed to beneficially own the securities beneficially owned by Emerald Bioventures, LLC. The address of Emerald Bioventures, LLC and Mr. Opler is Madison Ave, 11D, New York, NY 10022.

​

(4)

Consists of 301 shares of common stock being offered by Emily Nixon pursuant to this prospectus. Ryan Lee Hom has shared voting and dispositive power over the securities held by Ms. Nixon. The address of Ms. Nixon and Mr. Hom is 1840 Columbia Road NW Apt 503, Washington, DC 20009

​

(5)

Consists of 28,180 shares of common stock being offered by Ikarian Healthcare Master Fund, LP (“Ikarian Fund”) pursuant to this prospectus. Ikarian, as the investment manager of Ikarian Fund, has shared voting and dispositive power over the securities held by the Fund. Neil Shahrestani is the sole manager and a member of Ikarian and, in such capacities, may be deemed to share voting and dispositive power over such securities. The business address of Ikarian is 100 Crescent Court, Suite 1620, Dallas, TX 75201.

​

(6)

Consists of 15,519 shares of common stock being offered by Justin DiMartino pursuant to this prospectus. The address of Mr. DiMartino is PO BOX 3, Southfield, MA 01259.

​

(7)

Consists of 478 shares of common stock being offered by Mellisa Huhn pursuant to this prospectus. The address of Ms. Huhn is 30 Niblick St, Point Pleasant Beach, NJ 08742.

​

(8)

Consists of 377 shares of common stock being offered by Naveen Daryani pursuant to this prospectus. The address of Mr. Daryani is 20 Providence Forge Rd, Royersford, PA 19468.

​

(9)

Consists of 452 shares of common stock being offered by Navneet Kumar pursuant to this prospectus. The address of Mr. Kumar is 581 Lowell Street, Lexington, MA 02420.

​

(10)

Consists of 27,239 shares of common stock being offered by Patrick J. Crutcher pursuant to this prospectus. The address of Mr. Crutcher is 951 Glenwood Ave SE, No. 1806, Atlanta, GA 30316.

​

(11)

Consists of 5,387 shares of common stock being offered by Tatyana Touzova pursuant to this prospectus. The address of Ms. Touzova is 212 Creststone Drive, Cary, NC 27519.

​

Registration Rights

Pursuant to the Milestone Buyout Amendment Agreement, we agreed to file a registration statement registering for resale the shares of common stock issued pursuant to the Milestone Buyout Amendment Agreement within 75 days of issuance of such common stock, and have such registration statement declared effective with 60 days after such filing. We also agreed to use its commercially reasonable efforts to keep the registration statement effective under the Securities Act until all common stock issued pursuant the Milestone Buyout Amendment Agreement have been publicly sold by the holders thereof or until all common stock issued pursuant to the Milestone Buyout Amendment Agreement may be sold without restriction pursuant to Rule 144 under the Securities Act. The registration statement of which this prospectus is a part is being filed in order to satisfy our obligations under the Milestone Buyout Amendment Agreement.

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PLAN OF DISTRIBUTION

We are registering the shares of common stock of Avalo Therapeutics, Inc., par value of $0.001 per share, or the Common Stock, which we refer to herein as “Shares,” issued to the selling stockholders to permit the sale, transfer or other disposition of the Shares, by the selling stockholders or their donees, pledgees, distributees, transferees or other successors-in-interest from time to time after the date of this prospectus. We will not receive any of the proceeds from the sale by the selling stockholders of the Shares. We will, or will procure to, bear all fees and expenses incident to our obligation to register the Shares.

The selling stockholders may sell all or a portion of the Shares beneficially owned by them and offered hereby from time to time directly or through one or more underwriters, broker-dealers or agents. If the Shares are sold through underwriters or broker-dealers, the selling stockholders will be responsible for underwriting discounts (it being understood that the selling stockholders shall not be deemed to be underwriters solely as a result of their participation in this offering) or commissions or agent’s commissions. The Shares may be sold on any national securities exchange or quotation service on which the securities may be listed or quoted at the time of sale, in the over-the-counter market or in transactions otherwise than on these exchanges or systems or in the over-the-counter market and in one or more transactions at fixed prices, at prices related to prevailing market prices, or at negotiated prices, or, in the case of sales of our common stock, at market prices prevailing at the time of sale. These prices, as well as the timing, manner and size of each sale, will be determined by the selling stockholders or by agreement between such holders and underwriters or dealers who may receive fees or commissions in connection with such sale. These sales may be effected in transactions, which may involve crosses or block transactions. The selling stockholders may use any one or more of the following methods when selling Shares:

•

ordinary brokerage transactions and transactions in which the broker-dealer solicits purchasers;

​

•

block trades in which the broker-dealer will attempt to sell the Shares as agent, but may position and resell a portion of the block as principal to facilitate the transaction;

​

•

to or through underwriters or purchases by a broker-dealer as principal and resale by the broker-dealer for its account;

​

•

an exchange distribution in accordance with the rules of the applicable exchange;

​

•

through the distribution of such securities by any selling stockholder to its equity holders;

​

•

privately negotiated transactions;

​

•

settlement of short sales entered into after the effective date the registration statement of which this prospectus is a part;

​

•

broker-dealers may agree with the selling stockholders to sell a specified number of such securities at a stipulated price per Share;

​

•

through the writing or settlement of options or other hedging transactions, whether such options are listed on an options exchange or otherwise;

​

•

a combination of any such methods of sale; and

​

•

any other method permitted pursuant to applicable law.

​

The selling stockholders also may resell all or a portion of the Shares in open market transactions in reliance upon Rule 144 under the Securities Act, as permitted by that rule, or Section 4(a)(1) under the Securities Act, if available, rather than under this prospectus, provided that they meet the criteria and conform to the requirements of those provisions.

Broker-dealers engaged by the selling stockholders may arrange for other broker-dealers to participate in sales. If the selling stockholders effect such transactions by selling Shares to or through underwriters, broker-dealers or agents, such underwriters, broker-dealers or agents may receive commissions in the form of discounts, concessions or commissions from the selling stockholders or commissions from purchasers of the Shares for whom they may act as agent or to whom they may sell as principal. Such commissions will be in amounts to be negotiated, but, except as set forth in a supplement to this prospectus, in the case of an

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agency transaction will not be in excess of a customary brokerage commission in compliance with FINRA Rule 2121; and in the case of a principal transaction a markup or markdown in compliance with FINRA IM-2121.01.

In connection with sales of the Shares or otherwise, the selling stockholders may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of the Shares in the course of hedging in positions they assume. The selling stockholders may also sell Shares short and if such short sale takes place after the date that the registration statement of which this prospectus is a part is declared effective by the SEC, the selling stockholders may deliver Shares covered by this prospectus to close out short positions and to return borrowed Shares in connection with such short sales. The selling stockholders may also loan or pledge Shares to broker-dealers that in turn may sell such Shares, to the extent permitted by applicable law. The selling stockholders may also enter into option or other transactions with broker-dealers or other financial institutions or the creation of one or more derivative securities which require the delivery to such broker-dealer or other financial institution of shares offered by this prospectus, which shares such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction). Notwithstanding the foregoing, the selling stockholders have been advised that they may not use Shares the resale of which has been registered on this registration statement to cover short sales of our Common Stock made prior to the date the registration statement, of which this prospectus forms a part, has been declared effective by the SEC.

The selling stockholders may, from time to time, pledge or grant a security interest in some or all of the Shares owned by them and, if they default in the performance of their secured obligations, the pledgees or secured parties may offer and sell the Shares from time to time pursuant to this prospectus or any amendment to this prospectus under Rule 424(b)(3) or other applicable provision of the Securities Act of 1933, amending, if necessary, the list of selling stockholders to include the pledgee, transferee or other successors in interest as selling stockholders under this prospectus. The selling stockholders also may transfer and donate the Shares in other circumstances in which case the transferees, donees, pledgees or other successors in interest will be the selling beneficial owners for purposes of this prospectus.

The selling stockholders and any broker-dealer or agents participating in the distribution of the Shares may be deemed to be “underwriters” within the meaning of Section 2(11) of the Securities Act in connection with such sales. In such event, any commissions paid, or any discounts or concessions allowed to, any such broker-dealer or agent and any profit on the resale of the shares purchased by them may be deemed to be underwriting commissions or discounts under the Securities Act. Selling Stockholders who are “underwriters” within the meaning of Section 2(11) of the Securities Act will be subject to the applicable prospectus delivery requirements of the Securities Act including Rule 172 thereunder and may be subject to certain statutory liabilities of, including but not limited to, Sections 11, 12 and 17 of the Securities Act and Rule 10b-5 under the Exchange Act.

Each selling stockholder has informed the Company that it is not a registered broker-dealer and does not have any written or oral agreement or understanding, directly or indirectly, with any person to distribute the Shares. Upon the Company being notified in writing by a selling stockholder that any material arrangement has been entered into with a broker-dealer for the sale of Common Stock through a block trade, special offering, exchange distribution or secondary distribution or a purchase by a broker or dealer, a supplement to this prospectus will be filed, if required, pursuant to Rule 424(b) under the Securities Act, disclosing (i) the name of each such selling stockholder and of the participating broker-dealer(s), (ii) the number of Shares involved, (iii) the price at which such the Shares were sold, (iv) the commissions paid or discounts or concessions allowed to such broker-dealer(s), where applicable, (v) that such broker-dealer(s) did not conduct any investigation to verify the information set out or incorporated by reference in this prospectus, and (vi) other facts material to the transaction. In no event shall any broker-dealer receive fees, commissions and markups, which, in the aggregate, would exceed eight percent (8.0%).

Under the securities laws of some U.S. states, the Shares may be sold in such states only through registered or licensed brokers or dealers. In addition, in some U.S. states the Shares may not be sold unless such shares have been registered or qualified for sale in such state or an exemption from registration or qualification is available and is complied with.

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There can be no assurance that any selling stockholder will sell any or all of the Shares registered pursuant to the shelf registration statement, of which this prospectus forms a part.

Each selling stockholder and any other person participating in such distribution will be subject to applicable provisions of the Exchange Act and the rules and regulations thereunder, including, without limitation, to the extent applicable, Regulation M of the Exchange Act, which may limit the timing of purchases and sales of any of the Shares by the selling stockholder and any other participating person. To the extent applicable, Regulation M may also restrict the ability of any person engaged in the distribution of the Shares to engage in market-making activities with respect to the Shares. All of the foregoing may affect the marketability of the Shares and the ability of any person or entity to engage in market-making activities with respect to the Shares.

We will pay all expenses of the registration of the Shares pursuant to the registration rights agreement, including, without limitation, SEC filing fees and expenses of compliance with state securities or “blue sky” laws; provided, however, that each selling stockholder will pay all underwriting discounts and selling commissions, and any related legal or other advisory fees and expenses incurred by it, if any.

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DESCRIPTION OF SECURITIES TO BE REGISTERED

The following description of our capital stock and provisions of our amended and restated certificate of incorporation, as amended (the “A&R Certificate of Incorporation”) and our fifth amended and restated bylaws (the “A&R Bylaws”) are summaries. This description also summarizes relevant provisions of the General Corporation Law of the State of Delaware, which we refer to as the DGCL. The terms of A&R Certificate of Incorporation and A&R Bylaws and the terms of the DGCL are more detailed than the general information provided below. Therefore, please carefully consider the actual provisions of the A&R Certificate of Incorporation and the A&R Bylaws, which have been filed with the SEC as exhibits to the registration statement of which this prospectus forms a part, as well as the DGCL.

Common Stock

Voting

Each holder of common stock is entitled to one vote for each share held of record on all matters submitted to a vote of the stockholders, including the election of directors, and does not have cumulative voting rights. Accordingly, the holders of a majority of the shares of common stock entitled to vote in any election of directors can elect all of the directors standing for election.

Dividends

Subject to preferences that may be applicable to any then-outstanding preferred stock, the holders of common stock are entitled to receive dividends, if any, as may be declared from time to time by the board of directors out of legally available funds.

Liquidation

In the event of our liquidation, dissolution or winding up, holders of our common stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all of our debts and other liabilities, and the satisfaction of any liquidation preference granted to the holders of any then-outstanding shares of preferred stock.

Rights and Preferences

Holders of our common stock have no preemptive, conversion or subscription rights, and there are no redemption or sinking fund provisions applicable to our common stock. The rights, preferences and privileges of the holders of common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock that we may designate in the future.

Fully Paid and Nonassessable

All of our outstanding shares of common stock are fully paid and nonassessable.

Nasdaq Capital Market Listing of Common Stock

Our common stock is listed on The Nasdaq Capital Market under the symbol “AVTX.”

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Equiniti Trust Company, LLC. The transfer agent and registrar’s address is 28 Liberty Street, Floor 53, New York, NY 10005.

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LEGAL MATTERS

The validity of the securities being offered hereby will be passed upon for us by Goodwin Procter LLP, Philadelphia, Pennsylvania.

EXPERTS

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2025, as set forth in their report, which is incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements are incorporated by reference in reliance on Ernst & Young LLP’s report, given on their authority as experts in accounting and auditing.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

We have filed a registration statement on Form S-3 with the SEC for the securities we are offering by this prospectus supplement. This prospectus supplement does not include all of the information contained in the registration statement. You should refer to the registration statement and its exhibits for additional information. We will provide to each person, including any beneficial owner, to whom a prospectus supplement is delivered, a copy of any or all of the information that has been incorporated by reference in the prospectus supplement but not delivered with the prospectus supplement.

We file annual, quarterly and current reports, proxy statements and other information with the SEC. The SEC maintains a website at www.sec.gov that contains reports, proxy and information statements and other information regarding registrants. Our SEC filings, including our registration statement and the exhibits and schedules thereto, are available on the SEC website at www.sec.gov.

We maintain a website at www.avalotx.com. Information contained in or accessible through our website does not constitute a part of this prospectus supplement.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to “incorporate by reference” information into this prospectus supplement, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The SEC file number for the documents incorporated by reference in this prospectus supplement is 001-37590. The documents incorporated by reference into this prospectus supplement contain important information that you should read about us.

The following documents are incorporated by reference into this document:

•

our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the SEC on March 23, 2026;

​

•

our Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, filed with the SEC on May 13, 2026;

​

•

our Current Reports on Form 8-K, filed with the SEC on January 12, 2026, March 27, 2026, April 28, 2026, May 5, 2026, May 7, 2026, June 8, 2026, June 12, 2026, June 16, 2026, and June 23, 2026 in each case only to the extent the information in such report is filed and not furnished;

​

•

the description of our common stock contained in Exhibit 4.5 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, filed with the SEC on March 20, 2025, including any amendments or reports filed for the purpose of updating such description.

​

We also incorporate by reference into this prospectus supplement all documents (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) that are filed by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this prospectus supplement and prior to the termination of the offering of securities under this prospectus supplement. These documents include periodic reports, such as Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, as well as proxy statements.

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Any statement in a document incorporated by reference or deemed to be incorporated by reference in this prospectus supplement shall be deemed to be modified or superseded for the purposes of this prospectus supplement to the extent that a statement contained herein or therein or in any other subsequently filed document which also is incorporated or deemed to be incorporated by reference herein or therein modifies or supersedes such statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement.

We will furnish without charge to you, on written or oral request, a copy of any or all of the documents incorporated by reference in this prospectus supplement, including exhibits to these documents. You should direct any requests for documents to Avalo Therapeutics, Inc., 1500 Liberty Ridge Drive, Suite 321, Wayne, Pennsylvania 19087; telephone: (410) 522-8707.

Any statement contained in this prospectus supplement, the accompanying prospectus or in a document incorporated or deemed to be incorporated by reference into this prospectus supplement or the accompanying prospectus will be deemed to be modified or superseded for purposes of the document to the extent that a statement contained in this prospectus supplement or the accompanying prospectus or any other subsequently filed document that is deemed to be incorporated by reference herein or therein modifies or supersedes the statement.

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​

​

Up to 128,189 Shares of Common Stock Offered by Selling Stockholders

​

PRELIMINARY PROSPECTUS

​

           , 2026

​

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PART II

INFORMATION NOT REQUIRED IN THE PROSPECTUS

Item 14.   Other Expenses of Issuance and Distribution.

The following table sets forth an itemization of the various expenses, all of which we will pay, in connection with the issuance and distribution of the securities being registered. The selling stockholder will not be responsible for any of the expenses of this offering. All of the amounts shown are estimated except the SEC registration fee.

​	SEC registration fee	​	​	​	$	327.86	​	​
​	Legal fees and expenses	​	​	​	$	75,000.00	​	​
​	Accounting fees and expenses	​	​	​	$	25,000.00	​	​
​	Printing expenses	​	​	​	$	15,000.00	​	​
​	Total	​	​	​	$	115,327.86	​	​

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 (“DGCL”) provides that a Delaware corporation may indemnify any persons who are, or are threatened to be made, parties to any threatened, pending, or completed action, suit, or proceeding, whether civil, criminal, administrative, or investigative (other than an action by or in the right of such corporation), by reason of the fact that such person was an officer, director, employee, or agent of such corporation, or is or was serving at the request of such person as an officer, director, employee, or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees), judgments, fines, and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit, or proceeding, provided that such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the corporation’s best interests and, with respect to any criminal action or proceeding, had no reasonable cause to believe that his or her conduct was illegal. A Delaware corporation may indemnify any person who is, or is threatened to be made, a party to any threatened, pending, or completed action or suit by or in the right of the corporation by reason of the fact that such person was a director, officer, employee, or agent of such corporation, or is or was serving at the request of such corporation as a director, officer, employee, or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees) actually and reasonably incurred by such person in connection with the defense or settlement of such action or suit provided such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the corporation’s best interests, except that no indemnification is permitted without judicial approval if the officer or director is adjudged to be liable to the corporation. Where an officer or director is successful on the merits or otherwise in the defense of any action referred to above, the corporation must indemnify him or her against the expenses which such officer or director has actually and reasonably incurred. Our amended and restated certificate of incorporation, as amended (the “A&R Certificate of Incorporation”) and our fifth amended and restated bylaws (the “A&R Bylaws”) provide for the indemnification of our directors and officers to the fullest extent permitted under the DGCL.

Section 102(b)(7) of the DGCL permits a corporation to provide in its certificate of incorporation that a director of the corporation shall not be personally liable to the corporation or its stockholders for monetary damages for breach of fiduciary duties as a director, except for liability for any:

•

breach of a director’s duty of loyalty to the corporation or its stockholders;

​

•

act or omission not in good faith or that involves intentional misconduct or a knowing violation of law;

​

•

unlawful payment of dividends, stock purchase or redemption of shares; or

​

•

transaction from which the director derives an improper personal benefit.

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Our A&R Certificate of Incorporation includes a provision providing for the limitation of liability to the maximum extent permitted under the DGCL. Expenses incurred by any officer or director in defending any proceeding in advance of its final disposition shall be paid by us upon delivery to us of an undertaking by or on behalf of such director or officer, to repay all amounts advanced if it should ultimately be determined that such director or officer is not entitled to be indemnified by us.

Section 174 of the DGCL provides, among other things, that a director, who willfully or negligently approves of an unlawful payment of dividends or an unlawful stock purchase or redemption, may be held liable for such actions. A director who was either absent when the unlawful actions were approved, or dissented at the time, may avoid liability by causing his or her dissent to such actions to be entered on the books containing minutes of the meetings of the board of directors at the time such action occurred or immediately after such absent director receives notice of the unlawful acts.

We maintain a directors’ and officers’ liability insurance policy. The policy insures directors and officers against unindemnified losses arising from certain wrongful acts in their capacities as directors and officers and reimburses us for those losses for which we have lawfully indemnified the directors and officers. The policy contains various exclusions.

We have entered into indemnification agreements with each of our directors and certain of our executive officers. These agreements require us to indemnify these individuals and, in certain cases, affiliates of such individuals, to the fullest extent permitted under Delaware law against liabilities that may arise by reason of their service to the Company, and to advance expenses incurred as a result of any proceeding against them as to which they could be indemnified.

Item 16.   Exhibits and Financial Statement Schedules.

(a)   Exhibits.

​	Exhibit Number	​	​	Description of Document	​
​	2.1*	​	​	Agreement and Plan of Merger and Reorganization, dated March 27, 2024, by and among Avalo Therapeutics, Inc., Project Athens Merger Sub, Inc., Second Project Athens Merger Sub, LLC and AlmataBio, Inc. (incorporated by reference to Exhibit 2.1 to the Current Report on Form 8-K filed on March 28, 2024).	​
​	3.1	​	​	Amended and Restated Certificate of Incorporation of Cerecor Inc. (incorporated by reference to Exhibit 3.1.2 to the Current Report on Form 8-K filed on May 17, 2018).	​
​	3.1.1	​	​	Certificate of Amendment to the Amended and Restated Certificate of Incorporation of Cerecor Inc. (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K filed on August 26, 2021).	​
​	3.1.2	​	​	Form of Certificate of Designation of Preferences, Rights and Limitations of Series A Convertible Preferred Stock of Cerecor Inc. (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K filed on April 28, 2017).	​
​	3.1.3	​	​	Certificate of Amendment to the Company’s Amended and Restated Certificate of Incorporation, as amended, dated July 5, 2022 and effective July 7, 2022 (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K filed on July 7, 2022).	​
​	3.1.4	​	​	Certificate of Amendment to the Company’s Amended and Restated Certificate of Incorporation, as amended, dated December 22, 2023 and effective December 28, 2023 (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K filed on December 28, 2023).	​
​	3.1.5	​	​	Form of Certificate of Designation of Preferences, Rights and Limitations of Series A Convertible Preferred Stock of Cerecor Inc. (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K filed on April 28, 2017).	​
​	3.1.6	​	​	Form of Certificate of Designation of Series B Non-Voting Convertible Preferred Stock of Cerecor Inc. (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K filed on December 27, 2018).	​

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​	Exhibit Number	​	​	Description of Document	​
​	3.1.7	​	​	Certificate of Designation for Avalo Therapeutics, Inc.’s Series C Preferred Stock filed with the Secretary of State of Delaware on March 27, 2024 (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K filed on March 28, 2024).	​
​	3.1.8	​	​	Certificate of Designation for Avalo Therapeutics, Inc.’s Series D Preferred Stock filed with the Secretary of State of Delaware on March 27, 2024 (incorporated by reference to Exhibit 3.2 to the Current Report on Form 8-K filed on March 28, 2024).	​
​	3.1.9	​	​	Certificate of Designation for Avalo Therapeutics, Inc.’s Series E Preferred Stock filed with the Secretary of State of Delaware on March 27, 2024 (incorporated by reference to Exhibit 3.3 to the Current Report on Form 8-K filed on March 28, 2024).	​
​	3.1.10	​	​	Certificate of Designation for Avalo Therapeutics, Inc.’s Series C-1 Preferred Stock filed with the Secretary of State of Delaware on June 11, 2026 (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K filed on June 12, 2026).	​
​	3.2	​	​	Fifth Amended and Restated Bylaws of Avalo Therapeutics, Inc. (incorporated by reference to Exhibit 3.2 to the Annual Report on Form 10-K filed on March 29, 2024).	​
​	4.1	​	​	Specimen Common Stock Certificate (incorporated by reference to Exhibit 4.3 to the Registration Statement on Form S-8 filed on May 20, 2016).	​
​	5.1	​	​	Opinion of Goodwin Procter LLP.	​
​	10.1#	​	​	Milestone Buyout Option Agreement and Amendment to Agreement and Plan of Merger and Reorganization, dated of April 26, 2026, by and between Avalo Therapeutics, Inc. and the signatory thereto (incorporated by reference to Exhibit 10.1 to the Current Report on Form 8-K filed on April 28, 2026).	​
​	23.1	​	​	Consent of Ernst & Young LLP, Independent Registered Public Accounting Firm.	​
​	23.2	​	​	Consent of Goodwin Procter LLP (included in Exhibit 5.1).	​
​	24.1	​	​	Power of Attorney (included on signature page to this Registration Statement on Form S-3).	​
​	107	​	​	Filing Fee Table.	​

​

*

Portions of this exhibit (indicated by asterisks) were omitted in accordance with the rules of the Securities and Exchange Commission.

​

Item 17.   Undertakings.

(a)   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 of 1933;

(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;

(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;

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provided, however, that paragraphs (a)(1)(i), (a)(1)(ii) and (a)(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 Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

(2)   That, for the purpose of determining any liability under the Securities Act of 1933, 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.

(5)   That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser, each prospectus filed pursuant to Rule 424(b) as part of a registration statement relating to an offering, other than registration statements relying on Rule 430B or other than prospectuses filed in reliance on Rule 430A, shall be deemed to be part of and included in the registration statement as of the date it is first used after effectiveness. 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 first use, 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 date of first use.

(b)   The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, 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.

(h)   Insofar as indemnification for liabilities arising under the Securities Act of 1933 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 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 Act and will be governed by the final adjudication of such issue.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, 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 Wayne, State of Pennsylvania, on the 17th day of July, 2026.

AVALO THERAPEUTICS, INC.

By:

/s/ Garry Neil, M.D.

​

​

Name:   Garry Neil, M.D.
Title:    Chief Executive Officer

POWER OF ATTORNEY

KNOW ALL BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Garry Neil, M.D. and Christopher Sullivan, and each or any one of them, as his or her true and lawful agent, proxy and attorney-in-fact, with full power of substitution and resubstitution, for him or her and in his or her name, place and stead, in any and all capacities, to (i) act on, sign and file with the Securities and Exchange Commission any and all amendments (including post-effective amendments) to this registration statement together with all schedules and exhibits thereto and any subsequent registration statement filed pursuant to Rule 462(b) under the Securities Act of 1933, as amended, together with all schedules and exhibits thereto, (ii) act on, sign and file such certificates, instruments, agreements and other documents as may be necessary or appropriate in connection therewith, (iii) act on and file any supplement to any prospectus included in this registration statement or any such amendment or any subsequent registration statement filed pursuant to Rule 462(b) under the Securities Act of 1933, as amended, and (iv) take any and all actions, which may be necessary or appropriate to be done, as fully for all intents and purposes as he or she might or could do in person, hereby approving, ratifying and confirming all that such agent, proxy and attorney-in-fact or any of his or her substitutes may lawfully do or cause to be done by virtue thereof.

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

​	Signature	​	​	Title	​	​	Date	​
​	/s/ Garry Neil, M.D. ​ Garry Neil, M.D.	​	​	President, Chief Executive Officer and Director (Principal Executive Officer)	​	​	July 17, 2026	​
​	/s/ Christopher Sullivan ​ Christopher Sullivan	​	​	Chief Financial Officer (Principal Financial and Accounting Officer)	​	​	July 17, 2026	​
​	/s/ Michael Heffernan ​ Michael Heffernan	​	​	Chairman of the Board of Directors, Director	​	​	July 17, 2026	​
​	/s/ Rita Jain, M.D. ​ Rita Jain, M.D.	​	​	Director	​	​	July 17, 2026	​
​	/s/ Ron Philip ​ Ron Philip	​	​	Director	​	​	July 17, 2026	​
​	/s/ Aaron Kantoff ​ Aaron Kantoff	​	​	Director	​	​	July 17, 2026	​

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​	Signature	​	​	Title	​	​	Date	​
​	/s/ Gilla Kaplan, Ph.D. ​ Gilla Kaplan, Ph.D.	​	​	Director	​	​	July 17, 2026	​
​	/s/ Kevin Lind ​ Kevin Lind	​	​	Director	​	​	July 17, 2026	​
​	/s/ Samantha Truex ​ Samantha Truex	​	​	Director	​	​	July 17, 2026	​

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