[424B5] Rein Therapeutics, Inc. Prospectus Supplement (Debt Securities)

Rhea-AI Filing Summary

Rein Therapeutics (Nasdaq: RNTX) has entered a Pre-Paid Advance Agreement (PPA) with YA II PN, Ltd. (Yorkville) that allows the company to raise up to $6 million by issuing common stock. Yorkville prepaid the first $1 million on 30 Jul 2025; the full amount remains outstanding and accrues 8% interest (18% upon default). Yorkville may at its discretion offset the balance by demanding shares priced at the lower of (a) 115% of the prior-day VWAP or (b) 95% of the lowest VWAP during the 7 preceding trading days, subject to a $0.28 floor. The share cap is 4.99% ownership and, without shareholder approval, 19.9% of outstanding stock. Based on a $1.41 reference price, up to 4.26 million new shares could be issued, lifting total outstanding to about 27.3 million and diluting existing holders by ~18%.
Rein qualifies as a “smaller reporting company” with a public float of $29.5 million; sales under its shelf cannot exceed one-third of that float in any 12-month period. Net proceeds will fund R&D for lead fibrosis candidates LTI-03 and LTI-01, possible in-licensing, and general corporate purposes. The facility provides immediate liquidity but could pressure the share price given the discounted issuance mechanics and ongoing interest expense.

Positive

• Immediate $1 million cash received, improving near-term liquidity.
• Flexible drawdown of remaining $5 million at company’s request provides optional funding.
• No underwriter fees or covenants typical of secured debt, preserving operational flexibility.

Negative

• Potential dilution of up to ~18% at current prices, with further dilution possible if share price falls toward the $0.28 floor.
• 8% accruing interest (18% on default) adds cost compared with straight equity issuance.
• Yorkville’s right to force share issuance at a discount may create sustained selling pressure and price volatility.
• Facility size is small relative to anticipated Phase 2/Phase 3 trial costs, implying future capital needs.

Insights

Equity Research Analyst

TL;DR: Small cash infusion helps near-term liquidity but creates dilution and potential overhang.

The $6 million PPA equals roughly 20% of Rein’s current market cap and should extend runway but not eliminate its going-concern risk. Because Yorkville can force share issuance at a 5% discount to the lowest 7-day VWAP (floor $0.28), the structure is share-price sensitive and could exacerbate downward pressure if volumes are thin. On the positive side, management accessed capital quickly without traditional underwriting fees and preserved shelf capacity. With only $1 million drawn, Rein retains flexibility to tap an additional $5 million. Investors should monitor FDA feedback on the Phase 2 LTI-03 hold; progress there would likely dictate future share demand and pricing.

Biotech Industry Specialist

TL;DR: Facility buys R&D time but signals funding challenges.

An 8% interest rate plus warrant-like pricing implies limited lender appetite for unsecured biotech risk. The raise is modest relative to Phase 2 trial costs, so further capital will be needed. Nonetheless, immediate funds permit continuation of non-clinical work needed to lift the FDA hold on LTI-03, preserving asset value. The 19.9% NASDAQ cap and 4.99% ownership limit slightly mitigate dilution, but a sub-$0.28 floor highlights downside risk. Overall impact is neutral: liquidity gained versus shareholder dilution and execution risk.

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Filed pursuant to Rule 424(b)(5)
Registration No. 333-287342

PROSPECTUS SUPPLEMENT

(To Prospectus Dated May 22, 2025)

$6,000,000

Common Stock

We are offering up to $6,000,000 of shares of our common stock, par value $0.001 per share, by this prospectus supplement and the accompanying prospectus, directly to YA II PN, Ltd., a Cayman Islands exempt limited partnership (“Yorkville”), an affiliate of Yorkville Advisors Global, LP, in connection with the Pre-Paid Advance Agreement that we entered into with Yorkville on July 29, 2025 (the “Pre-Paid Advance Agreement”). In accordance with the terms of the Pre-Paid Advance Agreement, we may request advances of up to an aggregate of $6,000,000 (the “Commitment Amount”) from Yorkville (each such advance, a “Pre-Paid Advance”), and, at any time that there is an outstanding balance under the Pre-Paid Advances, Yorkville may provide written notice (each, a “Purchase Notice”) requiring that we issue and sell shares of our common stock to Yorkville, which shall be offset against the amount outstanding under the Pre-Paid Advances, at a price per share equal to the lower of (a) 115% of the daily volume weighted average price (the “VWAP”) of our common stock on the Nasdaq Capital Market on the last full trading day immediately prior to the date of such Pre-Paid Advance (the “Fixed Price”) and (b) 95% of the lowest daily VWAP of our common stock on the Nasdaq Capital Market during the seven consecutive trading days immediately preceding the date on which Yorkville provides the Purchase Notice to us (the “Market Price”), but in no event shall the Market Price be less than $0.28 per share (the “Floor Price”). Yorkville shall, in each Purchase Notice, select the number of shares to be issued, in its sole discretion, provided that the aggregate price for such shares may not exceed the balance outstanding under the Pre-Paid Advances or exceed other specified limits in the Pre-Paid Advance Agreement. Interest shall accrue on the outstanding balance of each Pre-Paid Advance at an annual rate of 8%, subject to an increase to 18% upon events of default described in the Pre-Paid Advance Agreement. Concurrent with the entry into the Pre-Paid Advance Agreement, we requested a Pre-Paid Advance of $1,000,000 from Yorkville under the Pre-Paid Advance Agreement, all of which remains outstanding as of the date of this prospectus supplement.

In addition to our issuance of common stock to Yorkville pursuant to the Pre-Paid Advance Agreement, this prospectus supplement also covers the resale of those shares from time to time by Yorkville to the public. Although we have been advised by Yorkville, and Yorkville represents in the Pre-Paid Advance Agreement, that Yorkville is purchasing shares for its own account, for investment purposes in which it takes investment risk (including, without limitation, the risk of loss), and without any view or intention to distribute such shares in violation of the Securities Act of 1933, as amended (the “Securities Act”), or any other applicable securities laws, the Securities and Exchange Commission (the “SEC”) may take the position that Yorkville is deemed an “underwriter” within the meaning of Section 2(a)(11) of the Securities Act and any profits on the sales of shares of our common stock by Yorkville and any discounts, commissions or concessions received by Yorkville are deemed to be underwriting discounts and commissions under the Securities Act. For additional information on the methods of sale that may be used by Yorkville, see “Plan of Distribution”.

Our common stock is listed on The Nasdaq Capital Market under the trading symbol “RNTX.” On July 28, 2025, the last sale price of our common stock as reported on The Nasdaq Capital Market was $1.41 per share.

As of July 28, 2025, the aggregate market value of our outstanding common stock held by non-affiliates was approximately $29,530,566, which we calculated based on 23,046,121 shares of outstanding common stock as of July 28, 2025, of which 20,943,664 shares were held by non-affiliates, and a price per share of $1.41 which was the closing price of our common stock on July 28, 2025. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell, pursuant to the registration statement of which this prospectus supplement forms a part, securities with a value exceeding one-third of the aggregate market value of our outstanding common stock held by non-affiliates in any 12-month period, so long as the aggregate market value of our outstanding common stock held by non-affiliates remains below $75.0 million.

We are a “smaller reporting company” as that term is defined under the federal securities laws, and, as such, have elected to rely on certain reduced public company disclosure requirements. See “Prospectus Summary – Implications of Being a Smaller Reporting Company.”

Investing in our common stock involves certain risks. See “Risk Factors” beginning on page S-8 of this prospectus supplement and in the documents incorporated by reference in this prospectus supplement and in the accompanying prospectus for a discussion of the factors you should carefully consider before deciding to invest in our common stock.

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

The date of this prospectus supplement is July 30, 2025

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		Page
ABOUT THIS PROSPECTUS SUPPLEMENT			S-1
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS			S-2
PROSPECTUS SUPPLEMENT SUMMARY			S-4
THE OFFERING			S-6
RISK FACTORS			S-8
USE OF PROCEEDS			S-10
DIVIDEND POLICY			S-11
DILUTION			S-12
PLAN OF DISTRIBUTION			S-14
MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATION FOR NON-U.S. HOLDERS			S-15
LEGAL MATTERS			S-19
EXPERTS			S-20
WHERE YOU CAN FIND MORE INFORMATION			S-21
INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE			S-22

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ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement and accompanying prospectus are part of a registration statement that we filed with the Securities and Exchange Commission, which we refer to as the “SEC,” utilizing a “shelf” registration process. Under this shelf registration process, we may from time to time sell shares of our common stock having an aggregate offering price of up to $150,000,000 (subject to compliance with General Instruction I.B.6 of Form S-3). Under this prospectus supplement and accompanying prospectus, we may from time to time sell shares of our common stock having an aggregate offering price of up to $6,000,000, at prices and on terms set forth in the Pre-Paid Advance Agreement, between us and YA II PN, Ltd. (“Yorkville”) dated as of July 29, 2025 (the “Pre-Paid Advance Agreement”).

This document is in two parts. Generally, when we refer to this prospectus supplement, we are referring to both parts of this document combined. To the extent there is a conflict between the information contained in this prospectus supplement and the information contained in the accompanying prospectus or any document incorporated by reference therein filed prior to the date of this prospectus supplement, you should rely on the information in this prospectus supplement; provided that 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 in this prospectus supplement—the statement in the document having the later date modifies or supersedes the earlier statement.

Before buying any of the common stock that we are offering, we urge you to carefully read this prospectus supplement and all of the information contained in the documents incorporated by reference herein, as well as the additional information described under the headings “Where You Can Find More Information” and “Incorporation of Certain Documents by Reference.” These documents contain important information that you should consider when making your investment decision.

You should rely only on the information contained in or incorporated by reference in this prospectus, any accompanying prospectus supplement or in any related free writing prospectus filed by us with the SEC. We have not authorized anyone to provide you with different information. This prospectus and the accompanying prospectus supplement do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the securities described in the accompanying prospectus supplement or an offer to sell or the solicitation of an offer to buy such securities in any circumstances in which such offer or solicitation is unlawful. You should assume that the information appearing in this prospectus, any prospectus supplement, the documents incorporated by reference and any related free writing prospectus is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed materially since those dates. This prospectus, any applicable prospectus supplement and the information incorporated herein or therein by reference contains market data, industry statistics and other data that have been obtained or compiled from information made available by independent third parties. We have not independently verified the accuracy and completeness of such data.

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 agreement, and should not be deemed to be a representation, warranty or covenant to you. 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.

Unless the context otherwise indicates, references in this prospectus supplement to “Rein,” “we,” “our,” “us” and “the Company” refer, collectively, to Rein Therapeutics, Inc. and our consolidated subsidiaries.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the accompanying prospectus, and the information incorporated by reference herein and therein, contain “forward-looking statements” within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act that involve substantial risks and uncertainties. All statements, other than statements of historical fact, contained in this prospectus supplement and the accompanying prospectus, or the information incorporated by reference herein or therein, including statements regarding our strategy, future operations, future financial position, future revenue, projected costs, prospects, plans and objectives of management, and expanded market growth are forward-looking statements. The words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “might,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “would,” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

These forward-looking statements include, among other things, statements about:

• our ability to address the U.S. Food and Drug Administration (“FDA”) non-clinical requests and to remove a clinical hold on our Phase 2 clinical trial of LTI-03;

• our plans to develop and commercialize LTI-03, including the potential benefits thereof;

• our ability to secure sufficient additional capital in the near term or implement other strategies needed to alleviate our current substantial doubt about our ability to continue as a going concern;

• our expectations regarding our ability to fund our operating expenses, our planned activities, and capital expenditure requirements with our cash, cash equivalents and investments;

• our Phase 2 clinical trial of LTI-03 and our ability to re-start and complete such clinical trial, subject to obtaining additional funding;

• our decision to temporarily delay further clinical development of LTI-01 until additional funds are raised;

• our unproven approach to drug research and development in the area of fibrotic diseases, with a focus on Caveolin-1, or Cav1, -related peptides, and our ability to develop marketable products;

• our future clinical trials for LTI-03 and LTI-01, whether conducted by us or by any future collaborators, including our ability to enroll patients in our clinical trials, the timing of initiation of these trials and of the anticipated results;

• the success of our remediation efforts related to the material weaknesses identified in our internal controls over financial reporting;

• the timing of and our ability to obtain and maintain marketing approvals for LTI-03 and LTI-01;

• the rate and degree of market acceptance and clinical utility of any products for which we receive marketing approval;

• our commercialization, marketing and manufacturing capabilities and strategy;

• our intellectual property position and strategy, and our ability to obtain, maintain and enforce intellectual property rights for our platform and development candidates;

• our ability to identify additional product candidates with significant commercial potential;

• our plans to enter into collaborations for the development and commercialization of LTI-03, LTI-01 and any additional product candidates;

• our reliance on third-party manufacturing and supply vendors and contract research organizations, or CROs;

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• potential benefits of any future collaboration;

• developments relating to our competitors and our industry;

• the impact of general economic conditions, including inflation and the imposition of new or revised tariffs or other trade restrictions;

• the impact of government laws and regulations; and

• the use of proceeds from this offering.

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have included important factors in the cautionary statements included, or incorporated by reference, in this prospectus supplement and the accompanying prospectus, particularly in the “Risk Factors” section, that we believe could cause actual results or events to differ materially from the forward-looking statements that we make. Our forward-looking statements do not reflect the potential impact of future acquisitions, mergers, dispositions, collaborations, joint ventures or investments that we may make or enter into.

You should read this prospectus supplement and the accompanying prospectus and the documents we reference herein and have filed or incorporated by reference to the registration statement of which this prospectus supplement is a part completely and with the understanding that our actual future results may be materially different from what we expect. The forward-looking statements contained in this prospectus supplement and the accompanying prospectus and incorporated by reference herein are made of the date hereof, and we do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by applicable law.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights selected information contained elsewhere in this prospectus supplement and the accompanying prospectus and in the documents we incorporate by reference herein and therein. This summary does not contain all of the information you should consider before making an investment decision. You should read this prospectus supplement and the accompanying prospectus carefully, especially the risks of investing in our common stock discussed under “Risk Factors” beginning on page S-8 of this prospectus supplement and our most recent Annual Report on Form 10-K and Quarterly Report on Form 10-Q, along with our consolidated financial statements and notes to those consolidated financial statements and the other information incorporated by reference in this prospectus supplement and the accompanying prospectus, before making an investment decision.

Rein Therapeutics, Inc.

Overview

We are a clinical stage biopharmaceutical company focused on developing novel therapies for the treatment of orphan pulmonary and fibrosis indications with no approved or limited effective treatments. We currently have two product candidates in clinical development, LTI-03 and LTI-01, and multiple candidates in preclinical development focused on fibrosis indications. Our lead product candidate is LTI-03, a peptide for which we conducted a Phase 1b dose-ranging, placebo-controlled safety, tolerability, and pharmacodynamic biomarker activity trial in development for the treatment of Idiopathic Pulmonary Fibrosis that has demonstrated the ability in both preclinical studies and clinical trials to protect healthy lung epithelial cells and reduce pro-fibrotic signaling. Our second product candidate is LTI-01, a proenzyme that completed a Phase 2a dose-ranging, placebo-controlled trial and a Phase 1b safety, tolerability and proof of mechanism trial in loculated pleural effusion patients, an indication that has no approved drug treatment.

Corporate Information

We were incorporated under the laws of the State of Delaware on August 6, 2001 under the name Renegade Therapeutics, Inc. We changed our name to Aileron Therapeutics, Inc. in February 2007. On October 31, 2023, we acquired Lung Therapeutics, Inc., or Lung, pursuant to an Agreement and Plan of Merger, after which time Lung became a wholly owned subsidiary of ours. On January 10, 2025, we changed our name to Rein Therapeutics, Inc., and changed our trading symbol from “ALRN” to “RNTX”, effective January 13, 2025. Our principal executive office is located at 12407 N. Mopac Expy. Suite 250 #390, Austin, TX 78758, and our telephone number is (737) 802-1989. Our website address is http://www.reintx.com. The information contained on, or that can be accessed through, our website is not a part of this prospectus supplement. We have included our website address in this prospectus supplement solely as an inactive textual reference.

Rein and other trademarks or service marks of Rein appearing in this prospectus supplement and the accompanying prospectus are the property of Rein. The other trademarks, trade names and service marks appearing in this prospectus supplement and the accompanying prospectus are the property of their respective owners. Solely for convenience, the trademarks and trade names in this prospectus supplement and the accompanying prospectus are referred to without the ^® and ^™ symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto.

Implications of Being a Smaller Reporting Company

We are a “smaller reporting company,” meaning that the market value of our stock held by non-affiliates is less than $700 million and our annual revenue was less than $100 million during our most recently completed fiscal year. We may continue to be a smaller reporting company if either

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(i) the market value of our stock held by non-affiliates is less than $250 million 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 is less than $700 million. We may rely on exemptions from certain disclosure requirements that are available to smaller reporting companies. For so long as we remain a smaller reporting company, we are permitted and intend 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 us Shares of our common stock having an aggregate offering price of up to $6,000,000 at a price per share equal to the lower of (a) 115% of the daily volume weighted average price (the “VWAP”) of our common stock on the Nasdaq Capital Market on the last full trading day immediately prior to the date of such Pre-Paid Advance (the “Fixed Price”) and (b) 95% of the lowest daily VWAP of our common stock on the Nasdaq Capital Market during the seven consecutive trading days immediately preceding the date on which Yorkville provides the Purchase Notice to us (the “Market Price”), but in no event shall the Market Price be less than $0.28 per share (the “Floor Price”). The amount and timing of sales of common stock offered hereby is at the sole discretion of Yorkville.

Common stock outstanding following the offering Up to 27,301,440 shares, assuming the sale of 4,255,319 shares of our common stock in this offering at an offering price of $1.41 per share, which was the last reported sale price of our common stock on the Nasdaq Capital Market on July 28, 2025. The actual number of shares of our common stock issued will vary depending on the sale price under this offering.

Use of proceeds We expect to use the net proceeds, if any, from this offering to fund the research and development of our product candidates, the acquisition or in-licensing of products or product candidates, business or technologies, or collaboration and for working capital, capital expenditures and other general corporate purposes. See “Use of Proceeds” on page S-10 of this prospectus supplement for more information.

The Nasdaq Capital Market symbol “RNTX”

Risk factors Investing in our common stock involves risks. See “Risk factors” beginning on page S-8 of this prospectus supplement and other information included or incorporated by reference into this prospectus supplement and the accompanying prospectus for a discussion of the factors you should carefully consider before deciding to invest in our common stock.

The number of shares of our common stock to be outstanding after the offering is based on 23,046,121 shares of common stock outstanding as of July 25, 2025, and excludes:

• 16,127 shares of our common stock issued pursuant to our At the Market Offering Agreement, dated May 15, 2025, between us and H.C. Wainwright & Co., LLC (the “ATM Agreement”);

• 12,232,000 shares of our common stock issuable upon conversion of 12,232 shares of Series X Preferred Stock outstanding as of July 25, 2025;

• 6,616,499 shares of our common stock reserved for issuance upon exercise of outstanding warrants, which consist of (i) 726,437 shares of our common stock, with an exercise price of $5.66, which expire on May 20, 2029, which were issued in October 2023, (ii) 255,000 shares of our common stock, with an exercise price of $4.89 per share, which expire on May 2, 2027, which were issued in November 2023, (iii) 3,383,367 shares of our common stock, with an exercise price of $4.68 per share, which

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expire on May 3, 2027, which were issued in May 2024; (iv) 1,939,000 of our common stock, with an exercise price of $0.001 per share, which were issued in April 2025; and (v) 312,695 shares of our common stock, with an exercise price of $0.001 per share, which were issued in April 2025;

• 3,065,029 shares of our common stock issuable upon the exercise of stock options outstanding as of July 25, 2025, at a weighted average exercise price of $5.30 per share;

• 2,389,566 additional shares of our common stock available for future issuance as of July 25, 2025 under our 2021 Stock Incentive Plan, as amended, or the 2021 Plan; and

• 7,500 shares of our common stock available for future issuance as of July 25, 2025 under our 2017 Employee Stock Purchase Plan, or the 2017 ESPP.

Unless otherwise indicated, all information in this prospectus supplement assumes:

• no conversion of outstanding Series X Preferred Stock; and

• no exercise of the warrants or options or described above.

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RISK FACTORS

Investing in our common stock involves a high degree of risk. You should carefully consider the risks and uncertainties described below together with all of the other information contained in this prospectus supplement and the accompanying prospectus and the risk factors in our most recent Annual Report on Form 10-K, Quarterly Report on Form 10-Q and in our other filings with the SEC that we make from time to time, which are incorporated by reference in this prospectus supplement and the accompanying prospectus, together with other information in this prospectus supplement and the accompanying prospectus, the information and documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and in any prospectus supplement or free writing prospectus that we authorize for use in connection with this offering. If any of the following risks actually occur, our business, prospects, operating results and financial condition could suffer materially. In such event, the trading price of our common stock could decline and you might lose all or part of your investment.

Additional Risks Related to this Offering

Substantial blocks of our common stock may be sold into the market as a result of the Pre-Paid Advance Agreement.

The price of our common stock could decline and be volatile if there are substantial sales of shares of our common stock, if there is a large number of shares of our common stock available for sale, or if there is the perception that these sales could occur.

In accordance with the terms of the Pre-Paid Advance Agreement we entered with Yorkville, we may request Pre-Paid Advances of up to an aggregate of $6,000,000 from Yorkville (each such payment, a “Pre-Paid Advance”), and, at any time that there is an outstanding balance under such Pre-Paid Advances, Yorkville may provide written notice requiring that we issue and sell shares of our common stock to Yorkville, which shall be offset against the amounts outstanding under the Pre-Paid Advances. Any issuances of shares of our common stock pursuant to the Pre-Paid Advance Agreement to offset outstanding Pre-Paid Advances will dilute the percentage ownership of stockholders and may dilute the per share projected earnings (if any) or book value of our common stock. Sales of a substantial number of shares of our common stock in the public market or other issuances of shares of our common stock, or the perception that these sales or issuances could occur, could cause the market price of our common stock to decline and may make it more difficult for you to sell your shares at a time and price that you deem appropriate.

You may experience immediate and substantial dilution in the net tangible book value per share of our common stock you purchase.

The offering price per share of our common stock in this offering may exceed the net tangible book value per share of our common stock outstanding prior to this offering. Assuming that an aggregate of 4,255,319 shares of our common stock are sold pursuant to this prospectus supplement at a price of $1.41 per share, which was the last reported sale price of our common stock on the Nasdaq Capital Market on July 28, 2025, for aggregate gross proceeds of $6,000,000.00, after deducting estimated aggregate offering expenses payable by us, you would experience immediate dilution of $0.97 per share, representing the difference between our as adjusted net tangible book value per share after giving effect to this offering and the assumed offering price.

Once we receive a Pre-Paid Advance, we do not have the right to control the timing and amount of the issuance of our shares of common stock to Yorkville under the Pre-Paid Advance Agreement and, accordingly, it is not possible to predict the actual number of shares we will issue pursuant to the Pre-Paid Advance Agreement at any one time or in total.

Once we receive a Pre-Paid Advance, including the initial Pre-Paid Advance, we do not have the right to control the timing and amount of any issuance of our shares of common stock to Yorkville under the Pre-Paid Advance

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Agreement. Sales of our common stock, if any, to Yorkville under the Pre-Paid Advance Agreement will depend upon market conditions and other factors, and the discretion of Yorkville.

We may ultimately sell to Yorkville all, some or none of the shares of our common stock that may be available for us to sell to Yorkville pursuant to the Pre-Paid Advance Agreement.

Because any additional Pre-Paid Advances after the initial Pre-Paid Advance are at the discretion of Yorkville and the purchase price per share to be paid by Yorkville for the shares of common stock to be issued to Yorkville under the Pre-Paid Advance Agreement, if any, will fluctuate based on the market prices of our common stock, it is not possible for us to predict, as of the date of this prospectus supplement and prior to any such sales, the number of shares of common stock that we will issue to Yorkville under the Pre-Paid Advance Agreement, the purchase price per share that Yorkville will pay for shares purchased from us under the Pre-Paid Advance Agreement, or the aggregate gross proceeds that we will receive from Yorkville under the Pre-Paid Advance Agreement, if any.

In addition, unless we satisfy certain exceptions set forth in the Pre-Paid Advance Agreement relating to the prices at which we have sold shares to Yorkville pursuant to the Pre-Paid Advance Agreement, or we obtain stockholder approval, we will not be able to issue shares of our common stock in excess of 19.9% of the outstanding shares of our common stock as of July 28, 2025 under the Pre-Paid Advance Agreement (or any other transaction that is integrated with the Pre-Paid Advance Agreement) in accordance with applicable Nasdaq rules. Depending on the market prices of our common stock in the future, this could be a significant limitation on the amount of funds we are able to raise pursuant to the Pre-Paid Advance Agreement. Other limitations in the Pre-Paid Advance Agreement, including an ownership limitation that limits Yorkville to holding, at any time, no more than 4.99% of the then outstanding voting power of our outstanding common stock, and our ability to meet the conditions necessary to request a Pre-Paid Advance, could also prevent us from being able to request Pre-Paid Advances up to the Commitment Amount.

We have broad discretion over the use of our cash, cash equivalents and investments, including the net proceeds from the Pre-Paid Advance Agreement, and may not use them effectively.

Our management has broad discretion in the use of our available cash, cash equivalents and investments, including the net proceeds, if any, from this offering, and could spend the proceeds in ways that do not improve our results of operations or enhance the value of our common stock. The failure by our management to apply these funds effectively could result in financial losses that could have a material adverse effect on our business, cause the price of our common stock to decline and delay the development of our product candidates. We may invest our available cash, cash equivalents and investments, including the net proceeds from this offering, pending their use in a manner that does not produce income or that loses value.

We do not anticipate paying any cash dividends on our capital stock in the foreseeable future. Accordingly, stockholders must rely on capital appreciation, if any, for any return on their investment.

We have never declared or paid cash dividends on our capital stock. We currently intend to retain all of our future earnings, if any, to finance the growth and development of our business. As a result, capital appreciation, if any, of our common stock will be your sole source of gain for the foreseeable future.

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USE OF PROCEEDS

We may request advances of up to $6,000,000 under the Pre-Paid Advance Agreement before deducting the estimated offering expenses payable by us and the discount to Yorkville set forth in the Pre-Paid Advance Agreement, which provides that advances will be purchased by Yorkville at 95% of the face amount of the Pre-Paid Advance. We will initially receive, on the date hereof, $1,000,000 in net proceeds, before expenses and discounts. At Yorkville’s sole discretion, we may request from Yorkville an additional $5,000,000 in net proceeds, before expenses, during the term of the Pre-Paid Advance Agreement.

We expect to use the net proceeds that we receive under the Pre-Paid Advance Agreement to fund the research and development of our product candidates, the acquisition or in-licensing of products or product candidates, business or technologies, or collaboration and for working capital, capital expenditures and other general corporate purposes.

This expected use of the net proceeds from this offering represents our intentions based upon our current plans and business conditions. The amounts and timing of our actual use of the net proceeds may vary significantly depending on numerous factors, including our ability to address the FDA non-clinical requests and to remove a clinical hold on our Phase 2 clinical trial of LTI-03, the progress of our research and development efforts, the status of and results from clinical trials, any collaborations that we may enter into with third parties for our programs, and any unforeseen cash needs. Accordingly, our management will have broad discretion in the timing and application of these proceeds and will retain broad discretion over the allocation of the net proceeds from this offering. We have no current agreements, commitments or understandings for any material acquisitions or licenses of any products, businesses or technologies.

Pending our use of the net proceeds from this offering, we intend to invest the net proceeds in a variety of capital preservation investments, including short-term, investment-grade, interest-bearing instruments and U.S. government securities.

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DIVIDEND POLICY

We have never declared nor paid cash dividends on our common stock. We currently intend to retain all of our future earnings, if any, to finance the growth and development of our business. We do not intend to pay cash dividends in respect of our common stock in the foreseeable future. Any future determination to pay cash dividends will be made at the discretion of our board of directors and will depend on restrictions and other factors our board of directors may deem relevant. Investors should not purchase our common stock with the expectation of receiving cash dividends.

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DILUTION

If you invest in our common stock in this offering, your ownership interest will be diluted immediately to the extent of the difference between the price per share you pay for your shares and the pro forma as adjusted net tangible book value per share of our common stock after giving effect to this offering.

Our historical net tangible book value as of March 31, 2025 was approximately $1,349,335, or $0.06 per share. Our historical tangible book value is the amount of our total tangible assets less total liabilities. Historical net tangible book value per share represents our historical net tangible book value divided by the 22,005,317 shares of our common stock outstanding as of March 31, 2025.

Our pro forma net tangible book value as of March 31, 2025 was approximately $6,629,216, or $0.29 per share of our common stock. Pro forma net tangible book value is the amount of our total tangible assets less our total liabilities, after giving effect to (i) the exercise for cash of warrants originally issued by us in November 2023 for the purchase of an aggregate of 159,500 shares of our common stock at an exercise price of $1.60 per share in April 2025; (ii) the exercise for cash of warrants originally issued in May 2024 for the purchase of an aggregate of 890,138 shares of our common stock at an exercise price of $1.60 per share in May 2025; (iii) the surrender and cancellation of warrants to purchase 1,939,000 shares of our common stock originally issued in November 2023 and an aggregate cash payment of $1.599 per share in exchange for pre-funded warrants to purchase 1,939,000 shares of our common stock at an exercise price of $0.001 per share in April 2025; and (iv) the issuance and sale of pre-funded warrants to purchase 312,695 shares of our common stock for an aggregate purchase price of $500,000 in April 2025. Pro forma net tangible book value per share represents pro forma net tangible book value divided by the total number of shares outstanding as of March 31, 2025, after giving effect to the pro forma adjustments described above.

After giving effect to the issuance and sale of our common stock pursuant to this prospectus supplement and the accompanying prospectus in the aggregate amount of $6,000,000 at an assumed offering price of $1.41 per share, the last reported sale price of our common stock on The Nasdaq Capital Market on July 28, 2025, and after deducting discounts to Yorkville and estimated aggregate offering expenses payable by us, our pro forma as adjusted net tangible book value as of March 31, 2025 would have been approximately $12,129,216, or $0.44 per share. This represents an immediate increase in pro forma net tangible book value of $0.15 per share to existing stockholders and dilution of $0.97 per share of pro forma as adjusted net tangible book value to new investors based on the assumed average sale price of $1.41 per share. The following table illustrates this dilution to the investors purchasing shares of common stock in this offering:

Assumed public offering price per share							$  1.41
Historical net tangible book value per share as of March 31, 2025			$  0.06
Increase in historical net tangible book value per share attributable to the pro forma adjustments described above			$  0.23
Pro forma net tangible book value per share as of March 31, 2025			$  0.29
Increase in pro forma net tangible book value per share attributable to new investors			$  0.15
Pro forma as adjusted net tangible book value per share after this offering							$  0.44
Dilution per share to new investors							$  0.97

The foregoing table and discussion exclude:

• 16,127 shares of our common stock issued pursuant to the ATM Agreement;

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• 12,232,000 shares of our common stock issuable upon conversion of 12,232 shares of Series X Preferred Stock outstanding as of March 31, 2025;

• 6,616,499 shares of our common stock reserved for issuance upon exercise of outstanding warrants, which consist of (i) 726,437 shares of our common stock, with an exercise price of $5.66, which expire on May 20, 2029, which were issued in October 2023, (ii) 255,000 shares of our common stock, with an exercise price of $4.89 per share, which expire on May 2, 2027, which were issued in November 2023, (iii) 3,383,367 shares of our common stock, with an exercise price of $4.68 per share, which expire on May 3, 2027, which were issued in May 2024; (iv) 1,939,000 of our common stock, with an exercise price of $0.001 per share, which were issued in April 2025; and (v) 312,695 shares of our common stock, with an exercise price of $0.001 per share, which were issued in April 2025;

• 3,080,582 shares of our common stock issuable upon the exercise of stock options outstanding as of March 31, 2025, at a weighted average exercise price of $5.28 per share;

• 2,389,566 additional shares of our common stock available for future issuance as of March 31, 2025 under the 2021 Plan, as well as any automatic increase in the number of shares of common stock reserved under the 2021 Plan; and

• 7,500 shares of our common stock available for future issuance as of March 31, 2025 under the 2017 ESPP, as well as any automatic increase in the number of shares of common stock reserved for issuance under the 2017 ESPP.

To the extent that we issue additional shares of common stock in the future, whether upon the exercise of outstanding warrants or options or otherwise, there will be further dilution to investors participating in this offering. In addition, we may choose to raise additional capital due to market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans. To the extent that additional capital is raised through the sale of equity or convertible debt securities, the issuance of these securities may result in further dilution to our stockholders.

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PLAN OF DISTRIBUTION

On July 29, 2025, we entered into the Pre-Paid Advance Agreement with Yorkville. The Pre-Paid Advance Agreement provides that, upon the terms and subject to the conditions set forth therein, we may request Pre-Paid Advances of up to an aggregate of $6,000,000 from Yorkville, which will be purchased by Yorkville at 95% of the face amount of the Pre-Paid Advance. At any time that there is an outstanding balance under the Pre-Paid Advances, Yorkville may provide written notice requiring that we issue shares of our common stock to Yorkville, which shall be offset against and reduce the amounts outstanding under the Pre-Paid Advances, at a price per share equal to the lower of (i) 115% of the VWAP of our common stock on the last full trading day immediately preceding the closing of such Pre-Paid Advance or (ii) 95% of the lowest daily VWAP of our common stock during the seven consecutive trading days immediately preceding the date on which Yorkville provides the Purchase Notice to us, subject to a floor price of $0.28 per share. Yorkville shall, in each Purchase Notice, select the number of shares to be issued, in its sole discretion, provided that the aggregate price for such shares may not exceed the balance outstanding under the Pre-Paid Advances or exceed other specified limits in the Pre-Paid Advance Agreement. Concurrent with the entry into the Pre-Paid Advance Agreement, we requested a Pre-Paid Advance of $1,000,000 from Yorkville under the Pre-Paid Advance Agreement and received $950,000 of cash proceeds after application of the discount to Yorkville, all of which remains outstanding as of the date of this prospectus supplement. Amounts offset by the issuance of PPA Shares shall be applied first toward accrued and unpaid interest, if any, and then toward outstanding principal under the Pre-Paid Advances.

In addition to our issuance of Common Stock to Yorkville pursuant to the Pre-Paid Advance Agreement, this prospectus supplement also covers the resale of those shares from time to time by Yorkville to the public. Though we have been advised by Yorkville, and Yorkville represents in the Pre-Paid Advance Agreement, that it is purchasing the shares for its own account, for investment purposes in which it takes investment risk (including, without limitation, the risk of loss), and without any view or intention to distribute such shares in violation of the Securities Act or any other applicable securities laws, the SEC may take the position that Yorkville may be deemed an “underwriter” within the meaning of Section 2(a)(11) of the Securities Act. We have agreed in the Pre-Paid Advance Agreement to provide customary indemnification to Yorkville. It is possible that our shares may be sold by Yorkville in one or more of the following manners:

• ordinary brokerage transactions and transactions in which the broker solicits purchasers;

• a block trade in which the broker or dealer so engaged 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 a broker-dealer as principal and resale by the broker-dealer for its account; or

• a combination of any such methods of sale.

We have advised Yorkville that it is required to comply with Regulation M promulgated under the Exchange Act. With certain exceptions, Regulation M precludes Yorkville, any affiliated purchasers, and any broker-dealer or other person who participates in the distribution from bidding for or purchasing, or attempting to induce any person to bid for or purchase, any security that is the subject of the distribution until the entire distribution is complete. Regulation M also prohibits any bids or purchases made in order to stabilize the price of a security in connection with the distribution of that security.

These restrictions may affect the marketability of the shares of our common stock by Yorkville and any unaffiliated broker-dealer.

We have paid the expenses incident to the registration under the Securities Act of the offer and sale of the shares of our common stock covered by this prospectus supplement and the accompanying prospectus. We also paid a $25,000 structuring and due diligence fee to an affiliate of Yorkville in connection with entry into the PPA.

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MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS FOR NON-U.S. HOLDERS

The following is a discussion of material U.S. federal income tax considerations relating to ownership and disposition of our common stock by a non-U.S. holder. For purposes of this discussion, the term “non-U.S. holder” means a beneficial owner (other than a partnership or other pass-through entity) of our common stock that is not, for U.S. federal income tax purposes:

• an individual who is a citizen or resident of the United States;

• a corporation, or other entity treated as a corporation for U.S. federal income tax purposes, created or organized in or under the laws of the United States, any state thereof or the District of Columbia;

• an estate the income of which is subject to U.S. federal income taxation regardless of its source; or

• a trust, if a U.S. court is able to exercise primary supervision over the administration of the trust and one or more U.S. persons have authority to control all substantial decisions of the trust or if the trust has a valid election in effect to be treated as a U.S. person under applicable U.S. Treasury Regulations.

This discussion is based on current provisions of the Internal Revenue Code of 1986, as amended (the “Code”), existing and proposed U.S. Treasury Regulations promulgated thereunder, current administrative rulings, and judicial decisions, as in effect as of the date of this prospectus supplement and all of which are subject to change or to differing interpretation, possibly with retroactive effect. Any change or differing interpretation could alter the tax consequences to non-U.S. holders described in this prospectus. In addition, there can be no assurance that the Internal Revenue Service (“IRS”) will not challenge one or more of the tax consequences described in this prospectus supplement.

This discussion addresses only non-U.S. holders that hold shares of our common stock as a capital asset (generally, property held for investment). This discussion does not address all aspects of U.S. federal income taxation that may be relevant to a particular non-U.S. holder in light of that non-U.S. holder’s individual circumstances nor does it address the alternative minimum tax, the Medicare tax on net investment income, U.S. federal estate or gift taxes, or any aspects of U.S. state, local, or non-U.S. taxes. This discussion also does not consider any specific facts or circumstances that may apply to a non-U.S. holder and does not address the special tax rules applicable to particular non-U.S. holders, such as:

• insurance companies;

• tax-exempt organizations;

• financial institutions;

• brokers or dealers in securities;

• pension plans;

• controlled foreign corporations;

• passive foreign investment companies;

• owners that hold our common stock as part of a straddle, hedge, conversion transaction, synthetic security, or other integrated investment; and

• certain U.S. expatriates.

In addition, this discussion does not address the tax treatment of partnerships or persons who hold their common stock through partnerships or other entities that are pass-through entities for U.S. federal income tax purposes. A partner in a partnership or other pass-through entity that will hold our common stock should consult his, her, or its own tax advisor regarding the tax consequences of the purchase, ownership, and disposition of our common stock through a partnership or other pass-through entity, as applicable.

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Prospective investors should consult their own tax advisors regarding the U.S. federal, state, local, and non-U.S. income and other tax considerations of acquiring, holding, and disposing of our common stock.

Dividends

If we pay distributions on our common stock, those distributions generally will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. If a distribution exceeds our current and accumulated earnings and profits, the excess will be treated as a tax-free return of the non-U.S. holder’s investment, up to such holder’s tax basis in the common stock. Any remaining excess will be treated as capital gain, subject to the tax treatment described below under the heading “—Gain on Disposition of Common Stock.”

Dividends paid to a non-U.S. holder generally will be subject to withholding of U.S. federal income tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder’s country of residence. A non-U.S. holder of our common stock who claims the benefit of an applicable income tax treaty between the United States and such holder’s country of residence generally will be required to provide a properly executed IRS Form W-8BEN or W-8BEN-E (or successor form) and satisfy applicable certification and other requirements. A non-U.S. holder that is eligible for a reduced rate of U.S. withholding tax under an income tax treaty may obtain a refund or credit of any excess amounts withheld by timely filing an appropriate claim with the IRS. Non-U.S. holders are urged to consult their own tax advisors regarding their entitlement to benefits under a relevant income tax treaty.

Dividends that are treated as effectively connected with a trade or business conducted by a non-U.S. holder within the United States and, if an applicable income tax treaty so provides, that are attributable to a permanent establishment or a fixed base maintained by the non-U.S. holder within the United States are generally exempt from the 30% withholding tax if the non-U.S. holder satisfies applicable certification and disclosure requirements. However, such U.S. effectively connected income is taxed on a net income basis at the same U.S. federal income tax rates applicable to United States persons (as defined in the Code). Any U.S. effectively connected income received by a non-U.S. holder that is a corporation may also, under certain circumstances, be subject to an additional “branch profits tax” at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder’s country of residence.

Gain on Disposition of Common Stock

A non-U.S. holder generally will not be subject to U.S. federal income tax on gain recognized on a disposition of our common stock unless:

• the gain is effectively connected with the non-U.S. holder’s conduct of a trade or business in the United States and, if an applicable income tax treaty so provides, the gain is attributable to a permanent establishment or fixed base maintained by the non-U.S. holder in the United States; in these cases, the non-U.S. holder will be taxed on a net income basis at the same U.S. federal income tax rates applicable to United States persons (as defined in the Code), and if the non-U.S. holder is a foreign corporation, an additional branch profits tax at a 30% rate, or such lower rate as may be specified by an applicable income tax treaty, may also apply;

• the non-U.S. holder is a nonresident alien present in the United States for 183 days or more in the taxable year of the disposition and certain other requirements are met, in which case the non-U.S. holder will be subject to a 30% tax (or such lower rate as may be specified by an applicable income tax treaty) on the net gain derived from the disposition, which may be offset by U.S.-source capital losses of the non-U.S. holder, if any; or

• we are, or have been at any time during the five-year period preceding such disposition (or the non-U.S. holder’s holding period, if shorter), a “U.S. real property holding corporation,” unless our common stock is regularly traded on an established securities market and the non-U.S. holder held no

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more than 5% of our outstanding common stock, directly or indirectly, during the shorter of the five year period ending on the date of the disposition or the period that the non-U.S. holder held our common stock. If we are determined to be a U.S. real property holding corporation and the foregoing exception does not apply, then the non-U.S. holder generally will be taxed on its net gain derived from the disposition at the U.S. federal income tax rates applicable to United States persons (as defined in the Code). Generally, a corporation is a “U.S. real property holding corporation” if the fair market value of its “U.S. real property interests” equals or exceeds 50% of the sum of the fair market value of its worldwide real property interests plus its other assets used or held for use in a trade or business. Although there can be no assurance, we believe that we are not currently, and we do not anticipate becoming, a “U.S. real property holding corporation” for U.S. federal income tax purposes. No assurance can be provided that our common stock will be regularly traded on an established securities market for purposes of the rule described above.

Information Reporting and Backup Withholding

We must report annually to the IRS and to each non-U.S. holder the gross amount of the distributions on our common stock paid to such holder and the tax withheld, if any, with respect to such distributions. Non-U.S. holders may have to comply with specific certification procedures to establish that the holder is not a U.S. person (as defined in the Code) in order to avoid backup withholding at the applicable rate with respect to dividends on our common stock. Generally, a non-U.S. holder will comply with such procedures if it provides a properly executed IRS Form W-8BEN or W-8BEN-E (or other applicable Form W-8) or otherwise meets documentary evidence requirements for establishing that it is a non-U.S. holder, or otherwise establishes an exemption. Dividends paid to non-U.S. holders subject to withholding of U.S. federal income tax, as described above under the heading “—Dividends,” will generally be exempt from U.S. backup withholding.

Information reporting and backup withholding generally will apply to the proceeds of a disposition of our common stock by a non-U.S. holder effected by or through the U.S. office of any broker, U.S. or foreign, unless the holder certifies its status as a non-U.S. holder and satisfies certain other requirements, or otherwise establishes an exemption. Generally, information reporting and backup withholding will not apply to a payment of disposition proceeds to a non-U.S. holder where the transaction is effected outside the United States through a non-U.S. office of a broker. However, for information reporting purposes, dispositions effected through a non-U.S. office of a broker with substantial U.S. ownership or operations generally will be treated in a manner similar to dispositions effected through a U.S. office of a broker. Non-U.S. holders should consult their own tax advisors regarding the application of the information reporting and backup withholding rules to them.

Copies of information returns may be made available to the tax authorities of the country in which the non-U.S. holder resides or is incorporated under the provisions of a specific treaty or agreement.

Backup withholding is not an additional tax. Rather, any amounts withheld under the backup withholding rules from a payment to a non-U.S. holder can be refunded or credited against the non-U.S. holder’s U.S. federal income tax liability, if any, provided that an appropriate claim is timely filed with the IRS.

FATCA

Provisions of the Code commonly referred to as the Foreign Account Tax Compliance Act, or FATCA, generally impose a 30% withholding tax on dividends on, and gross proceeds from the sale or other disposition of, our common stock if paid to a foreign entity unless (i) if the foreign entity is a “foreign financial institution,” the foreign entity undertakes certain due diligence, reporting, withholding, and certification obligations, (ii) if the foreign entity is not a “foreign financial institution,” the foreign entity identifies certain of its U.S. investors, or (iii) the foreign entity is otherwise excepted under FATCA.

Withholding under FATCA generally applies to payments of dividends on our common stock. While withholding under FATCA may apply to payments of gross proceeds from a sale or other disposition of our common stock,

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under proposed U.S. Treasury Regulations, withholding on payments of gross proceeds is not required. Although such regulations are not final, applicable withholding agents may rely on the proposed regulations until final regulations are issued.

If withholding under FATCA is required on any payment related to our common stock, investors not otherwise subject to withholding (or that otherwise would be entitled to a reduced rate of withholding) on such payment may be required to seek a refund or credit from the IRS. An intergovernmental agreement between the United States and an applicable foreign country may modify the requirements described in this section. Non-U.S. holders should consult their own tax advisors regarding the possible implications of FATCA on their investment in our common stock and the entities through which they hold our common stock.

The preceding discussion of material U.S. federal income tax considerations is for prospective investors’ information only. It is not tax advice. Prospective investors should consult their own tax advisors regarding the particular U.S. federal, state, local, and non-U.S. tax consequences of purchasing, holding, and disposing of our common stock, including the consequences of any proposed changes in applicable laws.

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LEGAL MATTERS

The validity of the shares of common stock offered hereby will be passed upon for us by Wilmer Cutler Pickering Hale and Dorr LLP, Boston, Massachusetts.

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EXPERTS

The financial statements of Rein Therapeutics, Inc. as of December 31, 2024 and for the year ended December 31, 2024 have been audited by Marcum LLP, an independent registered public accounting firm, as set forth in their report (which contains an explanatory paragraph relating to substantial doubt about the ability of Rein Therapeutics, Inc. to continue as a going concern as described in Note 1 to the financial statements), and are incorporated by reference in this prospectus supplement and the accompanying prospectus and in the registration statement of which this prospectus supplement and the accompanying prospectus are a part have been so incorporated in reliance on such report given upon such firm as experts in auditing and accounting.

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WHERE YOU CAN FIND MORE INFORMATION

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 periodic and current reports, proxy and information statements, and other information regarding registrants that are filed electronically with the SEC. These documents are also available, free of charge, through the Investors & Media section of our website, which is located at www.investors.reinrx.com. Information contained on our website is not incorporated by reference into this prospectus supplement, and you should not consider information on our website to be part of this prospectus supplement.

This prospectus supplement and the accompanying prospectus are part of a registration statement that we filed with the SEC with respect to the common stock offered under this prospectus supplement. This prospectus supplement, filed as part of the registration statement, does not contain all the information set forth in the registration statement and its exhibits and schedules, portions of which have been omitted as permitted by the rules and regulations of the SEC. For further information about us and the securities we are offering, we refer you to the registration statement and to its exhibits and schedules. Statements in this prospectus supplement and the accompanying prospectus concerning any document we filed as an exhibit to the registration statement or that we otherwise filed with the SEC are not intended to be comprehensive and are qualified by reference to these filings and the exhibits attached thereto. You should review the complete documents, as applicable, to evaluate these statements. You can obtain a copy of the registration statement from the SEC’s website or our website.

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INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC allows us to incorporate by reference much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus supplement and the accompanying prospectus is considered to be part of this prospectus supplement. Because we are incorporating by reference future filings with the SEC, this prospectus supplement is continually updated and those future filings may modify or supersede some of the information included or incorporated in this prospectus supplement and the accompanying prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus supplement and the accompanying prospectus or in any document previously incorporated by reference have been modified or superseded. This prospectus supplement incorporates by reference the documents listed below (File No. 001-38130) and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (in each case, other than those documents or the portions of those documents not deemed to be filed) between the date of the initial registration statement and the effectiveness of the registration statement and following the effectiveness of the registration statement until the offering of the securities under the registration statement is terminated or completed:

• Our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, filed with the SEC on April  7, 2025, as amended by our Annual Report on Form 10-K/A for the fiscal year ended December 31, 2024, filed with the SEC on April 30, 2025 ;

• Our Current Report on Form 10-Q for the fiscal quarter ended March 31, 2025, filed with the SEC on May 15, 2025;

• Our Current Reports on Form 8-K filed with the SEC on January 10, 2025, April  17, 2025, April  22, 2025, June  12, 2025, June  24, 2025, July 11, 2025 and July 30, 2025; and

• The description of our common stock contained in our Registration Statement on Form 8-A filed on June  23, 2017, as the description therein has been updated and superseded by the description of our capital stock contained in Exhibit 4.2 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, as filed with the SEC on April 15, 2024, and including any amendments or reports filed for the purpose of updating such description.

You may request a copy of these documents, which will be provided to you at no cost, by writing or telephoning us using the following contact information:

Rein Therapeutics, Inc.

12407 N. Mopac Expy., Suite 250 #390

Austin, TX 78758

(737) 802-1989

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PROSPECTUS

$150,000,000

Rein Therapeutics, Inc.

DEBT SECURITIES

COMMON STOCK

PREFERRED STOCK

WARRANTS

UNITS

We may offer and sell securities from time to time in one or more offerings of up to $150,000,000 in aggregate offering price. This prospectus describes the general terms of these securities and the general manner in which these securities will be offered. We will provide the specific terms of these securities in supplements to this prospectus. The prospectus supplements will also describe the specific manner in which these securities will be offered and may also supplement, update or amend information contained in this document. You should read this prospectus and any applicable prospectus supplement before you invest.

We may offer these securities in amounts, at prices and on terms determined at the time of offering. The securities may be sold directly to you, through agents, or through underwriters and dealers. If agents, underwriters or dealers are used to sell the securities, we will name them and describe their compensation in a prospectus supplement.

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

As of May 15, 2025, the aggregate market value of our outstanding common stock held by non-affiliates was approximately $47,321,018, which we calculated based on 22,153,736 shares of outstanding common stock as of May 14, 2025, of which 20,051,279 shares were held by non-affiliates, and a price per share of $2.36 which was the closing price of our common stock on May 15, 2025. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell, pursuant to the registration statement of which this prospectus forms a part, securities with a value exceeding one-third of the aggregate market value of our outstanding common stock held by non-affiliates in any 12-month period, so long as the aggregate market value of our outstanding common stock held by non-affiliates remains below $75.0 million.

During the 12 calendar months prior to and including the date of this prospectus, we have not offered or sold any securities pursuant to General Instruction I.B.6 of Form S-3.

Investing in these securities involves certain risks. See the information included under “Risk Factors” on page 2 of this prospectus and in any accompanying prospectus supplement, and under similar headings in the documents incorporated by reference in this prospectus or any prospectus supplement, for a discussion of the factors you should carefully consider before deciding to purchase these securities.

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

The date of this prospectus is May 22, 2025.

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TABLE OF CONTENTS

		Page
ABOUT THIS PROSPECTUS			1
RISK FACTORS			2
WHERE YOU CAN FIND MORE INFORMATION			3
INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE			4
CAUTIONARY NOTE REGARDING FORWARD-LOOKING INFORMATION			5
REIN THERAPEUTICS, INC.			6
USE OF PROCEEDS			7
DESCRIPTION OF DEBT SECURITIES			8
DESCRIPTION OF CAPITAL STOCK			18
DESCRIPTION OF WARRANTS			25
DESCRIPTION OF UNITS			26
FORMS OF SECURITIES			27
PLAN OF DISTRIBUTION			29
LEGAL MATTERS			31
EXPERTS			31

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, which we refer to as the “SEC,” utilizing a “shelf” registration process. Under this shelf registration process, we may from time to time sell any combination of the securities described in this prospectus in one or more offerings for an aggregate initial offering price of up to $150,000,000.

This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide one or more prospectus supplements that will contain specific information about the terms of the offering. The prospectus supplement may also add, update or change information contained in this prospectus. You should read both this prospectus and the accompanying prospectus supplement together with the additional information described under the heading “Where You Can Find More Information.”

You should rely only on the information contained in or incorporated by reference in this prospectus, any accompanying prospectus supplement or in any related free writing prospectus filed by us with the SEC. We have not authorized anyone to provide you with different information. This prospectus and any accompanying prospectus supplement do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the securities described in this prospectus or such accompanying prospectus supplement or an offer to sell or the solicitation of an offer to buy such securities in any circumstances in which such offer or solicitation is unlawful. You should assume that the information appearing in this prospectus, any prospectus supplement, the documents incorporated by reference and any related free writing prospectus is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed materially since those dates.

Unless the context otherwise indicates, references in this prospectus to the “Company,” “we,” “our” and “us” refer, collectively, to Rein Therapeutics, Inc., a Delaware corporation.

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RISK FACTORS

Investing in our securities involves a high degree of risk. You should carefully consider the risks and uncertainties described in this prospectus and any accompanying prospectus supplement, including the risk factors set forth in our most recent Annual Report on Form 10-K, our most recent Quarterly Report on Form 10-Q and other filings we make with the SEC from time to time, which are incorporated by reference herein, before making an investment decision pursuant to this prospectus and any accompanying prospectus supplement relating to a specific offering.

Our business, financial condition and results of operations could be materially and adversely affected by any or all of these risks or by additional risks and uncertainties not presently known to us or that we currently deem immaterial that may adversely affect us in the future.

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WHERE YOU CAN FIND MORE INFORMATION

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. Copies of certain information filed by us with the SEC are also available on our website at https://www.reintx.com/. Our website is not a part of this prospectus and is not incorporated by reference in this prospectus.

This prospectus is part of a registration statement we filed with the SEC. This prospectus omits some information contained in the registration statement in accordance with SEC rules and regulations. You should review the information and exhibits in the registration statement for further information about us and our consolidated subsidiaries and the securities we are offering. Statements in this prospectus concerning any document we filed as an exhibit to the registration statement or that we otherwise filed with the SEC are not intended to be comprehensive and are qualified by reference to these filings and the exhibits attached thereto. You should review the complete document to evaluate these statements.

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INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC allows us to incorporate by reference much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus is considered to be part of this prospectus. Because we are incorporating by reference future filings with the SEC, this prospectus is continually updated and those future filings may modify or supersede some of the information included or incorporated in this prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus or in any document previously incorporated by reference have been modified or superseded. This prospectus incorporates by reference the documents listed below (File No. 001-38130) and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act (in each case, other than those documents or the portions of those documents not deemed to be filed) between the date of the initial registration statement and the effectiveness of the registration statement and following the effectiveness of the registration statement until the offering of the securities under the registration statement is terminated or completed.

• Our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, filed with the SEC on April  7, 2025, as amended by our Annual Report on Form 10-K/A for the fiscal year ended December 31, 2024, filed with the SEC on April 30, 2025;

• Our Quarterly Report on Form 10-Q for the fiscal quarter ended March 31, 2025, filed with the SEC on May 15, 2025;

• Our Current Reports on Form 8-K filed with the SEC on January  10, 2025, April  17, 2025 and April 22, 2025; and

• The description of our common stock contained in our Registration Statement on Form 8-A filed on June  23, 2017, as the description therein has been updated and superseded by the description of our capital stock contained in Exhibit 4.2 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, as filed with the SEC on April 15, 2024, and including any amendments or reports filed for the purpose of updating such description.

You may request a copy of these filings at no cost, by writing or telephoning us using the following contact information:

Rein Therapeutics, Inc.

12407 N. Mopac Expy. Suite 250 #390

Austin, TX 78758

(737) 802-1989

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING INFORMATION

This prospectus and the information incorporated by reference in this prospectus contain certain “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Exchange Act, that involve substantial risks and uncertainties. All statements, other than statements of historical facts, contained or incorporated by reference in this prospectus, including statements regarding our strategy, future operations, future financial position, future revenue, projected costs, prospects, plans and objectives of management and expected market growth are forward-looking statements. The words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “would” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have included important factors in the cautionary statements in this prospectus, particularly in the “Risk Factors” section, that could cause actual results or events to differ materially from the forward-looking statements that we make. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, collaborations, joint ventures or investments that we may make or enter into.

You should read this prospectus and the documents that we reference herein and have filed or incorporated by reference hereto completely and with the understanding that our actual future results may be materially different from what we expect. The forward-looking statements contained in this prospectus and incorporated by reference herein are made as of the date hereof, and we do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

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REIN THERAPEUTICS, INC.

Rein is a clinical stage biopharmaceutical company focused on developing novel therapies for the treatment of orphan pulmonary and fibrosis indications with no approved or limited effective treatments. We currently have two product candidates in clinical development, LTI-03 and LTI-01, and multiple candidates in preclinical development focused on fibrosis indications. Our lead product candidate is LTI-03, a peptide for which we conducted a Phase 1b dose-ranging, placebo-controlled safety, tolerability, and pharmacodynamic biomarker activity trial in development for the treatment of Idiopathic Pulmonary Fibrosis that has demonstrated the ability in both preclinical studies and clinical trials to protect healthy lung epithelial cells and reduce pro-fibrotic signaling. Our second product candidate is LTI-01, a proenzyme that completed a Phase 2a dose-ranging, placebo-controlled trial and a Phase 1b safety, tolerability and proof of mechanism trial in loculated pleural effusion patients, an indication that has no approved drug treatment.

We were incorporated under the laws of the State of Delaware on August 6, 2001 under the name Renegade Therapeutics, Inc. We changed our name to Aileron Therapeutics, Inc. in February 2007. On October 31, 2023, we acquired Lung Therapeutics, Inc., or Lung, pursuant to an Agreement and Plan of Merger, after which time Lung became a wholly owned subsidiary of ours. On January 10, 2025, we changed our name to Rein Therapeutics, Inc., and changed our trading symbol from “ALRN” to “RNTX”, effective January 13, 2025. Our principal executive offices are located at 12407 N. Mopac Expy, Suite 250 #390, Austin, TX 78758, and our telephone number is (737) 802-1989.

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USE OF PROCEEDS

We intend to use the net proceeds from the sale of any securities offered under this prospectus for general corporate purposes unless otherwise indicated in the applicable prospectus supplement. General corporate purposes may include working capital and capital expenditures, research and development expenses, including clinical trial costs, general and administrative expenses, potential acquisition of, or investment in, companies, technologies, products or assets that complement our business, and repayment and refinancing of debt. We may temporarily invest the net proceeds in investment-grade, interest-bearing securities until they are used for their stated purpose. We have not determined the amount of net proceeds to be used specifically for such purposes. As a result, management will retain broad discretion over the allocation of the net proceeds of any offering.

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DESCRIPTION OF DEBT SECURITIES

The following description summarizes the general terms and provisions of the debt securities that Rein may offer and sell from time to time. We will describe in a prospectus supplement the specific terms of the debt securities offered through that prospectus supplement, as well as any general terms and provisions described in this section that will not apply to those debt securities. As used in this “Description of Debt Securities,” the term “debt securities” means the senior and subordinated debt securities that we issue and the trustee authenticates and delivers under the applicable indenture. When we refer to “the Company,” “we,” “our,” and “us” in this section, we mean Rein Therapeutics, Inc., excluding, unless the context otherwise requires or as otherwise expressly stated, its subsidiaries.

We may issue senior debt securities from time to time, in one or more series under a senior indenture to be entered into between us and a senior trustee to be named in a prospectus supplement, which we refer to as the senior trustee. We may issue subordinated debt securities from time to time, in one or more series under a subordinated indenture to be entered into between us and a subordinated trustee to be named in a prospectus supplement, which we refer to as the subordinated trustee. The forms of senior indenture and subordinated indenture are filed as exhibits to the registration statement of which this prospectus forms a part. The senior indenture and the subordinated indenture are referred to individually as an indenture and together as the indentures and the senior trustee and the subordinated trustee are referred to individually as a trustee and together as the trustees. This section summarizes some of the provisions of the indentures and is qualified in its entirety by the specific text of the indentures, including definitions of terms used in the indentures. Wherever we refer to particular sections of, or defined terms in, the indentures, those sections or defined terms are incorporated by reference in this prospectus or the applicable prospectus supplement. You should review the indentures that are filed as exhibits to the registration statement of which this prospectus forms a part for additional information.

Neither indenture will limit the amount of debt securities that we may issue. The applicable indenture will provide that debt securities may be issued up to an aggregate principal amount authorized from time to time by us and may be payable in any currency or currency unit designated by us or in amounts determined by reference to an index.

General

The senior debt securities will constitute our unsecured and unsubordinated general obligations and will rank equally in right of payment with our other unsecured and unsubordinated obligations. The subordinated debt securities will constitute our unsecured and subordinated general obligations and will be junior in right of payment to our senior indebtedness (including senior debt securities), as described under the heading “—Certain Terms of the Subordinated Debt Securities—Subordination.” The debt securities will be structurally subordinated to all existing and future indebtedness and other liabilities of our subsidiaries unless such subsidiaries expressly guarantee such debt securities.

The debt securities will be our unsecured obligations. Any secured debt or other secured obligations will be effectively senior to the debt securities to the extent of the value of the assets securing such debt or other obligations.

The applicable prospectus supplement and/or free writing prospectus will include any additional or different terms of the debt securities of any series being offered, including the following terms:

• the title and type of the debt securities;

• whether the debt securities will be senior or subordinated debt securities, and, with respect to any subordinated debt securities the terms on which they are subordinated;

• the initial aggregate principal amount of the debt securities;

• the price or prices at which we will sell the debt securities;

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• the maturity date or dates of the debt securities and the right, if any, to extend such date or dates;

• the rate or rates, if any, at which the debt securities will bear interest, or the method of determining such rate or rates;

• the date or dates from which such interest will accrue, the interest payment dates on which such interest will be payable or the method of determination of such dates;

• the right, if any, to extend the interest payment periods and the duration of that extension;

• the manner of paying principal and interest and the place or places where principal and interest will be payable;

• the denominations of the debt securities if other than $2,000 or multiples of $1,000;

• provisions for a sinking fund, purchase fund or other analogous fund, if any;

• any redemption dates, prices, obligations and restrictions on the debt securities;

• the currency, currencies or currency units in which the debt securities will be denominated and the currency, currencies or currency units in which principal and interest, if any, on the debt securities may be payable;

• any conversion or exchange features of the debt securities;

• whether the debt securities will be subject to the defeasance provisions in the indenture;

• whether the debt securities will be issued in definitive or global form or in definitive form only upon satisfaction of certain conditions;

• whether the debt securities will be guaranteed as to payment or performance;

• whether the debt securities will be secured by any collateral and, if so, a general description of the collateral and the terms and provisions of such collateral, security, pledge or other related agreements;

• any special tax implications of the debt securities;

• any events of defaults or covenants in addition to or in lieu of those set forth in the indenture; and

• any other material terms of the debt securities.

When we refer to “principal” in this section with reference to the debt securities, we are also referring to “premium, if any.”

We may from time to time, without notice to or the consent of the holders of any series of debt securities, create and issue further debt securities of any such series ranking equally with the debt securities of such series in all respects (or in all respects other than (1) the payment of interest accruing prior to the issue date of such further debt securities or (2) the first payment of interest following the issue date of such further debt securities). Such further debt securities may be consolidated and form a single series with the debt securities of such series and have the same terms as to status, redemption or otherwise as the debt securities of such series.

You may present debt securities for exchange and you may present debt securities for transfer in the manner, at the places and subject to the restrictions set forth in the debt securities and the applicable prospectus supplement.

We will provide you those services without charge, although you may have to pay any tax or other governmental charge payable in connection with any exchange or transfer, as set forth in the indenture.

Debt securities may bear interest at a fixed rate or a floating rate. Debt securities bearing no interest or interest at a rate that at the time of issuance is below the prevailing market rate (original issue discount securities) may be sold at a discount below their stated principal amount. U.S. federal income tax considerations applicable

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to any such discounted debt securities or to certain debt securities issued at par which are treated as having been issued at a discount for U.S. federal income tax purposes will be described in the applicable prospectus supplement.

We may issue debt securities with the principal amount payable on any principal payment date, or the amount of interest payable on any interest payment date, to be determined by reference to one or more currency exchange rates, securities or baskets of securities, commodity prices or indices. You may receive a payment of principal on any principal payment date, or a payment of interest on any interest payment date, that is greater than or less than the amount of principal or interest otherwise payable on such dates, depending on the value on such dates of the applicable currency, security or basket of securities, commodity or index. Information as to the methods for determining the amount of principal or interest payable on any date, the currencies, securities or baskets of securities, commodities or indices to which the amount payable on such date is linked and certain related tax considerations will be set forth in the applicable prospectus supplement.

Certain Terms of the Senior Debt Securities

Covenants

Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the senior debt securities will not contain any financial or restrictive covenants, including covenants restricting either us or any of our subsidiaries from incurring, issuing, assuming or guaranteeing any indebtedness secured by a lien on any of our or our subsidiaries’ property or capital stock, or restricting either us or any of our subsidiaries from entering into sale and leaseback transactions.

Consolidation, Merger and Sale of Assets

Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, we may not consolidate with or merge into any other person, in a transaction in which we are not the surviving corporation, or convey, transfer or lease our properties and assets substantially as an entirety to any person, in either case, unless:

• the successor entity, if any, is a U.S. corporation, limited liability company, partnership or trust;

• the successor entity assumes our obligations on the senior debt securities and under the senior indenture;

• immediately after giving effect to the transaction, no default or event of default shall have occurred and be continuing; and

• we have delivered to the senior trustee an officer’s certificate and an opinion of counsel, each stating that the consolidation, merger, conveyance, transfer or lease and, if a supplemental indenture is required in connection with such transaction, such supplemental indenture, comply with the senior indenture and all conditions precedent provided for in the senior indenture relating to such transaction have been complied with.

The restrictions described in the bullets above do not apply (1) to our consolidation with or merging into one of our affiliates, if our board of directors determines in good faith that the purpose of the consolidation or merger is principally to change our state of incorporation or our form of organization to another form or (2) if we merge with or into a single direct or indirect wholly-owned subsidiary of ours.

The surviving business entity will succeed to, and be substituted for, us under the senior indenture and the senior debt securities and, except in the case of a lease, we shall be released from all obligations under the senior indenture and the senior debt securities.

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No Protection in the Event of a Change in Control

Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the senior debt securities will not contain any provisions that may afford holders of the senior debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control).

Events of Default

Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the following are events of default under the senior indenture with respect to senior debt securities of each series:

• failure to pay interest on any senior debt securities of such series when due and payable, if that default continues for a period of 30 days (or such other period as may be specified for such series);

• failure to pay principal on the senior debt securities of such series when due and payable whether at maturity, upon redemption, by declaration or otherwise (and, if specified for such series, the continuance of such failure for a specified period);

• default in the performance of or breach of any of our covenants or agreements in the senior indenture applicable to senior debt securities of such series, other than a covenant breach which is specifically dealt with elsewhere in the senior indenture, and that default or breach continues for a period of 90 days after we receive written notice from the trustee or from the holders of 25% or more in aggregate principal amount of the senior debt securities of such series;

• certain events of bankruptcy or insolvency, whether or not voluntary; and

• any other event of default provided for in such series of senior debt securities as may be specified in the applicable prospectus supplement.

Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the default by us under any other debt, including any other series of our debt securities, is not a default under the senior indenture.

If an event of default other than an event of default specified in the fourth bullet point above occurs with respect to a series of senior debt securities and is continuing under the senior indenture, then, and in each such case, either the trustee or the holders of not less than 25% in aggregate principal amount of such series then outstanding under the senior indenture (each such series voting as a separate class) by written notice to us and to the trustee, if such notice is given by the holders, may, and the trustee at the request of such holders shall, declare the principal amount of and accrued interest on such series of senior debt securities to be immediately due and payable, and upon this declaration, the same shall become immediately due and payable.

If an event of default specified in the fourth bullet point above occurs and is continuing, the entire principal amount of and accrued interest on each series of senior debt securities then outstanding shall automatically become immediately due and payable.

Unless otherwise specified in the prospectus supplement relating to a series of senior debt securities originally issued at a discount, the amount due upon acceleration shall include only the original issue price of the senior debt securities, the amount of original issue discount accrued to the date of acceleration and accrued interest, if any.

Upon certain conditions, declarations of acceleration may be rescinded and annulled and past defaults may be waived by the holders of a majority in aggregate principal amount of all the senior debt securities of such

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series affected by the default, each series voting as a separate class. Furthermore, subject to various provisions in the senior indenture, the holders of a majority in aggregate principal amount of a series of senior debt securities, by notice to the trustee, may waive a continuing default or event of default with respect to such senior debt securities and its consequences, except a default in the payment of principal of or interest on such senior debt securities (other than any such default in payment resulting solely from an acceleration of the senior debt securities) or in respect of a covenant or provision of the senior indenture which cannot be modified or amended without the consent of the holders of each such senior debt security. Upon any such waiver, such default shall cease to exist, and any event of default with respect to such senior debt securities shall be deemed to have been cured, for every purpose of the senior indenture; but no such waiver shall extend to any subsequent or other default or event of default or impair any right consequent thereto.

The holders of a majority in aggregate principal amount of a series of senior debt securities may 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 such senior debt securities. However, the trustee may refuse to follow any direction that conflicts with law or the senior indenture, that may involve the trustee in personal liability or that the trustee determines in good faith may be unduly prejudicial to the rights of holders of such series of senior debt securities not joining in the giving of such direction and may take any other action it deems proper that is not inconsistent with any such direction received from holders of such series of senior debt securities. A holder may not pursue any remedy with respect to the senior indenture or any series of senior debt securities unless:

• the holder gives the trustee written notice of a continuing event of default;

• the holders of at least 25% in aggregate principal amount of such series of senior debt securities make a written request to the trustee to pursue the remedy in respect of such event of default;

• the requesting holder or holders offer the trustee indemnity satisfactory to the trustee against any costs, liability or expense;

• the trustee does not comply with the request within 60 days after receipt of the request and the offer of indemnity; and

• during such 60-day period, the holders of a majority in aggregate principal amount of such series of senior debt securities do not give the trustee a direction that is inconsistent with the request.

These limitations, however, do not apply to the right of any holder of a senior debt security of any affected series to receive payment of the principal of and interest on such senior debt security in accordance with the terms of such debt security, or to bring suit for the enforcement of any such payment in accordance with the terms of such debt security, on or after the due date for the senior debt securities, which right shall not be impaired or affected without the consent of the holder.

The senior indenture requires certain of our officers to certify, on or before a fixed date in each year in which any senior debt security is outstanding, as to their knowledge of our compliance with all covenants, agreements and conditions under the senior indenture.

Satisfaction and Discharge

We can satisfy and discharge our obligations to holders of any series of debt securities if:

• we have paid, or caused to be paid, the principal of and interest on all senior debt securities of such series (with certain limited exceptions) when due and payable; or

• we deliver to the senior trustee for cancellation all senior debt securities of such series theretofore authenticated under the senior indenture (with certain limited exceptions); or

• all senior debt securities of such series have become due and payable or will become due and payable within one year (or are to be called for redemption within one year under arrangements satisfactory to

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the senior trustee) and we deposit in trust an amount of cash or a combination of cash and U.S. government or U.S. government agency obligations (or in the case of senior debt securities denominated in a foreign currency, foreign government securities or foreign government agency securities) sufficient to make interest, principal and any other payments on the debt securities of that series on their various due dates;

and if, in any such case, we also pay or cause to be paid all other sums payable under the senior indenture, as and when the same shall be due and payable and we deliver to the senior trustee an officer’s certificate and an opinion of counsel, each stating that these conditions have been satisfied.

Under current U.S. federal income tax law, the deposit and our legal release from the debt securities would be treated as though we took back your debt securities and gave you your share of the cash and debt securities or bonds deposited in trust. In that event, you could recognize gain or loss on the debt securities you give back to us. Purchasers of the debt securities should consult their own advisers with respect to the tax consequences to them of such deposit and discharge, including the applicability and effect of tax laws other than the U.S. federal income tax law.

Defeasance

Unless the applicable prospectus supplement provides otherwise, the following discussion of legal defeasance and covenant defeasance will apply to any series of debt securities issued under the indentures.

Legal Defeasance

We can legally release ourselves from any payment or other obligations on the debt securities of any series (called “legal defeasance”) if certain conditions are met, including the following:

• We deposit in trust for your benefit and the benefit of all other direct holders of the debt securities of the same series cash or a combination of cash and U.S. government or U.S. government agency obligations (or, in the case of senior debt securities denominated in a foreign currency, foreign government or foreign government agency obligations) that will generate enough cash to make interest, principal and any other payments on the debt securities of that series on their various due dates.

• There is a change in current U.S. federal income tax law or an IRS ruling that lets us make the above deposit without causing you to be taxed on the debt securities any differently than if we did not make the deposit and instead repaid the debt securities ourselves when due. Under current U.S. federal income tax law, the deposit and our legal release from the debt securities would be treated as though we took back your debt securities and gave you your share of the cash and debt securities or bonds deposited in trust. In that event, you could recognize gain or loss on the debt securities you give back to us.

• We deliver to the trustee a legal opinion of our counsel confirming the tax law change or ruling described above.

If we accomplish legal defeasance, as described above, you would have to rely solely on the trust deposit for repayment of the debt securities. You could not look to us for repayment in the event of any shortfall.

Covenant Defeasance

Without any change in current U.S. federal tax law, we can make the same type of deposit described above and be released from some of the covenants in the debt securities (called “covenant defeasance”). In that event, you would lose the protection of those covenants but would gain the protection of having money and securities

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set aside in trust to repay the debt securities. In order to achieve covenant defeasance, we must do the following (among other things):

• deposit in trust for your benefit and the benefit of all other direct holders of the debt securities of the same series cash or a combination of cash and U.S. government or U.S. government agency obligations (or, in the case of senior debt securities denominated in a foreign currency, foreign government or foreign government agency obligations) that will generate enough cash to make interest, principal and any other payments on the debt securities of that series on their various due dates.

• deliver to the trustee a legal opinion of our counsel confirming that under current U.S. federal income tax law we may make the above deposit without causing you to be taxed on the debt securities any differently than if we did not make the deposit and instead repaid the debt securities ourselves when due.

If we accomplish covenant defeasance, you could still look to us for repayment of the debt securities if there were a shortfall in the trust deposit. In fact, if one of the events of default occurred (such as our bankruptcy) and the debt securities become immediately due and payable, there may be such a shortfall. Depending on the events causing the default, you may not be able to obtain payment of the shortfall.

Modification and Waiver

We and the trustee may amend or supplement the senior indenture or the senior debt securities of any series without the consent of any holder:

• to convey, transfer, assign, mortgage or pledge any assets as security for the senior debt securities of one or more series;

• to evidence the succession of a corporation, limited liability company, partnership or trust to us, and the assumption by such successor of our covenants, agreements and obligations under the senior indenture or to otherwise comply with the covenant relating to mergers, consolidations and sales of assets;

• to comply with the requirements of the SEC in order to effect or maintain the qualification of the senior indenture under the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act;

• to add to our covenants such new covenants, restrictions, conditions or provisions for the protection of the holders, and to make the occurrence, or the occurrence and continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default;

• to cure any ambiguity, defect or inconsistency in the senior indenture or in any supplemental indenture or to conform the senior indenture or the senior debt securities to the description of senior debt securities of such series set forth in this prospectus or any applicable prospectus supplement;

• to provide for or add guarantors with respect to the senior debt securities of any series;

• to establish the form or forms or terms of the senior debt securities as permitted by the senior indenture;

• to evidence and provide for the acceptance of appointment under the senior indenture by a successor trustee, or to make such changes as shall be necessary to provide for or facilitate the administration of the trusts in the senior indenture by more than one trustee;

• to add to, change or eliminate any of the provisions of the senior indenture in respect of one or more series of senior debt securities, provided that any such addition, change or elimination shall (a) neither (1) apply to any senior debt security of any series created prior to the execution of such supplemental indenture and entitled to the benefit of such provision nor (2) modify the rights of the holder of any such senior debt security with respect to such provision or (b) become effective only when there is no senior debt security described in clause (a)(1) outstanding;

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• to make any change to the senior debt securities of any series so long as no senior debt securities of such series are outstanding; or

• to make any change that does not adversely affect the rights of any holder in any material respect.

Other amendments and modifications of the senior indenture or the senior debt securities issued may be made, and our compliance with any provision of the senior indenture with respect to any series of senior debt securities may be waived, with the consent of the holders of a majority of the aggregate principal amount of the outstanding senior debt securities of each series affected by the amendment or modification (voting as separate series); provided, however, that each affected holder must consent to any modification, amendment or waiver that:

• extends the final maturity of any senior debt securities of such series;

• reduces the principal amount of any senior debt securities of such series;

• reduces the rate, or extends the time for payment of, interest on any senior debt securities of such series;

• reduces the amount payable upon the redemption of any senior debt securities of such series;

• changes the currency of payment of principal of or interest on any senior debt securities of such series;

• reduces the principal amount of original issue discount securities payable upon acceleration of maturity or the amount provable in bankruptcy;

• waives a continuing default in the payment of principal of or interest on the senior debt securities (other than any such default in payment resulting solely from an acceleration of the senior debt securities);

• changes the provisions relating to the waiver of past defaults or impairs the right of holders to receive payment or to institute suit for the enforcement of any payment or conversion of any senior debt securities of such series on or after the due date therefor;

• modifies any of the provisions of these restrictions on amendments and modifications, except to increase any required percentage or to provide that certain other provisions cannot be modified or waived without the consent of the holder of each senior debt security of such series affected by the modification;

• adversely affects the right to convert or exchange senior debt securities into common stock, other securities or property in accordance with the terms of the senior debt securities; or

• reduces the above-stated percentage of outstanding senior debt securities of such series whose holders must consent to a supplemental indenture or modifies or amends or waives certain provisions of or defaults under the senior indenture.

It shall not be necessary for the holders to approve the particular form of any proposed amendment, supplement or waiver, but it shall be sufficient if the holders’ consent approves the substance thereof. After an amendment, supplement or waiver of the senior indenture in accordance with the provisions described in this section becomes effective, the trustee must give to the holders affected thereby certain notice briefly describing the amendment, supplement or waiver. Any failure by the trustee to give such notice, or any defect therein, shall not, however, in any way impair or affect the validity of any such amendment, supplemental indenture or waiver.

Notice of Redemption

Notice of any redemption of senior debt securities will be mailed at least 10 days but not more than 60 days before the redemption date to each holder of senior debt securities of a series to be redeemed. Any notice may, at our discretion, be subject to the satisfaction or waiver of one or more conditions precedent. In that case, such

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notice shall state the nature of such condition precedent. If we elect to redeem a portion but not all of such senior debt securities, the trustee will select the senior debt securities to be redeemed in a manner that complies with applicable legal and stock exchange requirements, if any. Interest on such debt securities or portions of senior debt securities will cease to accrue on and after the date fixed for redemption, unless we default in the payment of such redemption price and accrued interest with respect to any such senior debt security or portion thereof.

If any date of redemption of any senior debt security is not a business day, then payment of principal and interest may be made on the next succeeding business day with the same force and effect as if made on the nominal date of redemption and no interest will accrue for the period after such nominal date.

Conversion Rights

We will describe the terms upon which senior debt securities may be convertible into our common stock or other securities in a prospectus supplement. These terms will include the type of securities the senior debt securities are convertible into, the conversion price or manner of calculation thereof, the conversion period, provisions as to whether conversion will be at our option or the option of the holders, the events requiring an adjustment of the conversion price and provisions affecting conversion in the event of the redemption of the senior debt securities and any restrictions on conversion. They may also include provisions adjusting the number of shares of our common stock or other securities issuable upon conversion.

No Personal Liability of Incorporators, Stockholders, Officers, or Directors

The senior indenture provides that no recourse shall be had under any obligation, covenant or agreement of ours in the senior indenture or any supplemental indenture, or in any of the senior debt securities or because of the creation of any indebtedness represented thereby, against any of our incorporators, stockholders, officers or directors, past, present or future, or of any predecessor or successor entity thereof under any law, statute or constitutional provision or by the enforcement of any assessment or by any legal or equitable proceeding or otherwise. Each holder, by accepting the senior debt securities, waives and releases all such liability.

Concerning the Trustee

The senior indenture provides that, except during the continuance of an event of default, the trustee will not be liable except for the performance of such duties as are specifically set forth in the senior indenture. If an event of default has occurred and is continuing, the trustee will exercise such rights and powers vested in it under the senior indenture and will use the same degree of care and skill in its exercise as a prudent person would exercise under the circumstances in the conduct of such person’s own affairs.

The senior indenture and the provisions of the Trust Indenture Act incorporated by reference therein contain limitations on the rights of the trustee thereunder, should it become a creditor of ours or any of our subsidiaries, to obtain payment of claims in certain cases or to realize on certain property received by it in respect of any such claims, as security or otherwise. The trustee is permitted to engage in other transactions, provided that if it acquires any conflicting interest (as defined in the Trust Indenture Act), it must eliminate such conflict or resign.

We may have normal banking relationships with the senior trustee in the ordinary course of business.

Unclaimed Funds

All funds deposited with the trustee or any paying agent for the payment of principal, premium, interest or additional amounts in respect of the senior debt securities that remain unclaimed for two years after the date upon which such amounts became due and payable will be repaid to us. Thereafter, any right of any holder of senior debt securities to such funds shall be enforceable only against us, and the trustee and paying agents will have no liability therefor.

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Governing Law

The senior indenture and the senior debt securities will be governed by, and construed in accordance with, the internal laws of the State of New York.

Certain Terms of the Subordinated Debt Securities

Other than the terms of the subordinated indenture and subordinated debt securities relating to subordination or otherwise as described in the prospectus supplement relating to a particular series of subordinated debt securities, the terms of the subordinated indenture and subordinated debt securities are identical in all material respects to the terms of the senior indenture and senior debt securities.

Additional or different subordination terms may be specified in the prospectus supplement applicable to a particular series.

Subordination

The indebtedness evidenced by the subordinated debt securities is subordinate to the prior payment in full of all of our senior indebtedness, as defined in the subordinated indenture. During the continuance beyond any applicable grace period of any default in the payment of principal, premium, interest or any other payment due on any of our senior indebtedness, we may not make any payment of principal of or interest on the subordinated debt securities (except for certain sinking fund payments). In addition, upon any payment or distribution of our assets upon any dissolution, winding-up, liquidation or reorganization, the payment of the principal of and interest on the subordinated debt securities will be subordinated to the extent provided in the subordinated indenture in right of payment to the prior payment in full of all our senior indebtedness. Because of this subordination, if we dissolve or otherwise liquidate, holders of our subordinated debt securities may receive less, ratably, than holders of our senior indebtedness. The subordination provisions do not prevent the occurrence of an event of default under the subordinated indenture.

The term “senior indebtedness” of a person means with respect to such person the principal of, premium, if any, interest on, and any other payment due pursuant to any of the following, whether outstanding on the date of the subordinated indenture or incurred by that person in the future:

• all of the indebtedness of that person for money borrowed;

• all of the indebtedness of that person evidenced by notes, debentures, bonds or other securities sold by that person for money;

• all of the lease obligations that are capitalized on the books of that person in accordance with generally accepted accounting principles;

• all indebtedness of others of the kinds described in the first two bullet points above and all lease obligations of others of the kind described in the third bullet point above that the person, in any manner, assumes or guarantees or that the person in effect guarantees through an agreement to purchase, whether that agreement is contingent or otherwise; and

• all renewals, extensions or refundings of indebtedness of the kinds described in the first, second or fourth bullet point above and all renewals or extensions of leases of the kinds described in the third or fourth bullet point above;

unless, in the case of any particular indebtedness, renewal, extension or refunding, the instrument creating or evidencing it or the assumption or guarantee relating to it expressly provides that such indebtedness, renewal, extension or refunding is not superior in right of payment to the subordinated debt securities. Our senior debt securities constitute senior indebtedness for purposes of the subordinated indenture.

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DESCRIPTION OF CAPITAL STOCK

The following description of our capital stock is intended as a summary only and therefore is not complete. This description is based upon, and is qualified by reference to, our restated certificate of incorporation, as amended, or certificate of incorporation, and our amended and restated by-laws, or by-laws, each as amended from time to time, and by applicable provisions of Delaware corporate law. You should read our certificate of incorporation and by-laws, which are filed as exhibits to the registration statement of which this prospectus forms a part, for the provisions that are important to you.

Our authorized capital stock consists of 100,000,000 shares of common stock, par value $0.001 per share, and 5,000,000 shares of preferred stock, par value $0.001 per share, of which 24,847 shares have been designated as Series X Non-Voting Convertible Preferred Stock, par value $0.001 per share, or the Series X Preferred Stock. The following description of our capital stock and provisions of our certificate of incorporation and by-laws are summaries and are qualified by reference to our certificate of incorporation and by-laws. Copies of these documents are filed with the SEC as exhibits to our registration statement of which this prospectus forms a part. As of May 14, 2025, 22,153,736 shares of common stock were outstanding and 12,232 shares of Series X Preferred Stock were outstanding.

Common Stock

Voting Rights. Holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of stockholders and do not have cumulative voting rights. An election of directors by our stockholders will be determined by a plurality of the votes cast by the stockholders entitled to vote on the election. Any matter other than the election of directors to be voted upon by the stockholders will be decided by the affirmative vote of our stockholders having a majority in voting power of the votes cast by the stockholders present or represented and voting on such matter, except when a different vote is required by law, our certificate of incorporation or our by-laws.

Dividends. Holders of our common stock are entitled to receive proportionately any dividends as may be declared and paid on our common stock from funds lawfully available therefore as and when determined by our board of directors, subject to any preferential dividend rights of outstanding preferred stock.

Liquidation and Dissolution. In the event of our liquidation or dissolution, the holders of our common stock are entitled to receive proportionately all assets available for distribution to stockholders after the payment of all debts and other liabilities and subject to the prior rights of any outstanding preferred stock.

Other Rights. Holders of our common stock have no preemptive, subscription, redemption or conversion rights. The rights, preferences and privileges of holders of our 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 and issue in the future. Outstanding shares of our common stock are non-assessable. Holders of our common stock are not, and will not be, subject to any liability as stockholders.

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

Transfer Agent and Registrar. The transfer agent and registrar for our common stock is Computershare Trust Company, N.A.

Preferred Stock

Under the terms of our certificate of incorporation, our board of directors is authorized to issue shares of preferred stock in one or more series without stockholder approval. Our board of directors has the discretion to determine the rights, preferences, privileges and restrictions, including voting rights, dividend rights, conversion

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rights, redemption privileges and liquidation preferences, of each series of preferred stock. The issuance of preferred stock could impede the completion of a merger, tender offer, or other takeover attempt.

Our board of directors will make any determination to issue preferred shares based upon its judgment as to the best interests of our stockholders. Our directors, in so acting, could issue preferred stock having terms that could discourage an acquisition attempt through which an acquirer may be able to change the composition of our board of directors, including a tender offer or other transaction that some, or a majority, of our stockholders might believe to be in their best interests or in which stockholders might receive a premium for their stock over the then-current market price of the stock.

The preferred stock has the terms described below unless otherwise provided in the prospectus supplement relating to a particular series of preferred stock. You should read the prospectus supplement relating to the particular series of preferred stock being offered for specific terms, including:

• the designation and stated value per share of the preferred stock and the number of shares offered;

• the amount of liquidation preference per share;

• the price at which the preferred stock will be issued;

• the dividend rate, or method of calculation of dividends, the dates on which dividends will be payable, whether dividends will be cumulative or noncumulative and, if cumulative, the dates from which dividends will commence to accumulate;

• any redemption or sinking fund provisions;

• if other than the currency of the United States, the currency or currencies including composite currencies in which the preferred stock is denominated and/or in which payments will or may be payable;

• any conversion provisions; and

• any other rights, preferences, privileges, limitations and restrictions on the preferred stock.

The preferred stock will, when issued, be fully paid and non-assessable. Unless otherwise specified in the prospectus supplement, each series of preferred stock will rank equally as to dividends and liquidation rights in all respects with each other series of preferred stock. The rights of holders of shares of each series of preferred stock will be subordinate to those of our general creditors.

Rank. Unless otherwise specified in the prospectus supplement, the preferred stock will, with respect to dividend rights and rights upon our liquidation, dissolution or winding up of our affairs, rank:

• senior to our common stock and to all equity securities ranking junior to such preferred stock with respect to dividend rights or rights upon our liquidation, dissolution or winding up of our affairs;

• on a parity with all equity securities issued by us, the terms of which specifically provide that such equity securities rank on a parity with the preferred stock with respect to dividend rights or rights upon our liquidation, dissolution or winding up of our affairs; and

• junior to all equity securities issued by us, the terms of which specifically provide that such equity securities rank senior to the preferred stock with respect to dividend rights or rights upon our liquidation, dissolution or winding up of our affairs.

The term “equity securities” does not include convertible debt securities.

Dividends. Holders of the preferred stock of each series will be entitled to receive, when, as and if declared by our board of directors, cash dividends at such rates and on such dates described in the prospectus supplement.

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Different series of preferred stock may be entitled to dividends at different rates or based on different methods of calculation. The dividend rate may be fixed or variable or both. Dividends will be payable to the holders of record as they appear on our stock books on record dates fixed by our board of directors, as specified in the applicable prospectus supplement.

Dividends on any series of preferred stock may be cumulative or noncumulative, as described in the applicable prospectus supplement. If our board of directors does not declare a dividend payable on a dividend payment date on any series of noncumulative preferred stock, then the holders of that noncumulative preferred stock will have no right to receive a dividend for that dividend payment date, and we will have no obligation to pay the dividend accrued for that period, whether or not dividends on that series are declared payable on any future dividend payment dates. Dividends on any series of cumulative preferred stock will accrue from the date we initially issue shares of such series or such other date specified in the applicable prospectus supplement.

No dividends may be declared or paid or funds set apart for the payment of any dividends on any parity securities unless full dividends have been paid or set apart for payment on the preferred stock. If full dividends are not paid, the preferred stock will share dividends pro rata with the parity securities.

No dividends may be declared or paid or funds set apart for the payment of dividends on any securities junior to the preferred stock unless full dividends for all dividend periods terminating on or prior to the date of the declaration or payment will have been paid or declared and a sum sufficient for the payment set apart for payment on the preferred stock.

Liquidation Preference. Upon any voluntary or involuntary liquidation, dissolution or winding up of our affairs, then, before we make any distribution or payment to the holders of any common stock or any other class or series of our capital stock ranking junior to the preferred stock in the distribution of assets upon any liquidation, dissolution or winding up of our affairs, the holders of each series of preferred stock shall be entitled to receive out of assets legally available for distribution to stockholders, liquidating distributions in the amount of the liquidation preference per share set forth in the prospectus supplement, plus any accrued and unpaid dividends thereon. Such dividends will not include any accumulation in respect of unpaid noncumulative dividends for prior dividend periods. Unless otherwise specified in the prospectus supplement, after payment of the full amount of their liquidating distributions, the holders of preferred stock will have no right or claim to any of our remaining assets. Upon any such voluntary or involuntary liquidation, dissolution or winding up, if our available assets are insufficient to pay the amount of the liquidating distributions on all outstanding preferred stock and the corresponding amounts payable on all other classes or series of our capital stock ranking on parity with the preferred stock and all other such classes or series of shares of capital stock ranking on parity with the preferred stock in the distribution of assets, then the holders of the preferred stock and all other such classes or series of capital stock ranking on parity with the preferred stock will share ratably in any such distribution of assets in proportion to the full liquidating distributions to which they would otherwise be entitled.

Upon any such liquidation, dissolution or winding up and if we have made liquidating distributions in full to all holders of preferred stock, we will distribute our remaining assets among the holders of any other classes or series of capital stock ranking junior to the preferred stock according to their respective rights and preferences and, in each case, according to their respective number of shares. For such purposes, our consolidation or merger with or into any other corporation, trust or entity, or the sale, lease or conveyance of all or substantially all of our property or assets will not be deemed to constitute a liquidation, dissolution or winding up of our affairs.

Redemption. If so provided in the applicable prospectus supplement, the preferred stock will be subject to mandatory redemption or redemption at our option, as a whole or in part, in each case upon the terms, at the times and at the redemption prices set forth in such prospectus supplement.

The prospectus supplement relating to a series of preferred stock that is subject to mandatory redemption will specify the number of shares of preferred stock that shall be redeemed by us in each year commencing after

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a date to be specified, at a redemption price per share to be specified, together with an amount equal to all accrued and unpaid dividends thereon to the date of redemption. Unless the shares have a cumulative dividend, such accrued dividends will not include any accumulation in respect of unpaid dividends for prior dividend periods. We may pay the redemption price in cash or other property, as specified in the applicable prospectus supplement. If the redemption price for preferred stock of any series is payable only from the net proceeds of the issuance of shares of our capital stock, the terms of such preferred stock may provide that, if no such shares of our capital stock shall have been issued or to the extent the net proceeds from any issuance are insufficient to pay in full the aggregate redemption price then due, such preferred stock shall automatically and mandatorily be converted into the applicable shares of our capital stock pursuant to conversion provisions specified in the applicable prospectus supplement. Notwithstanding the foregoing, we will not redeem any preferred stock of a series unless:

• if that series of preferred stock has a cumulative dividend, we have declared and paid or contemporaneously declare and pay or set aside funds to pay full cumulative dividends on the preferred stock for all past dividend periods and the then current dividend period; or

• if such series of preferred stock does not have a cumulative dividend, we have declared and paid or contemporaneously declare and pay or set aside funds to pay full dividends for the then current dividend period.

In addition, we will not acquire any preferred stock of a series unless:

• if that series of preferred stock has a cumulative dividend, we have declared and paid or contemporaneously declare and pay or set aside funds to pay full cumulative dividends on all outstanding shares of such series of preferred stock for all past dividend periods and the then current dividend period; or

• if that series of preferred stock does not have a cumulative dividend, we have declared and paid or contemporaneously declare and pay or set aside funds to pay full dividends on the preferred stock of such series for the then current dividend period.

However, at any time we may purchase or acquire preferred stock of that series (1) pursuant to a purchase or exchange offer made on the same terms to holders of all outstanding preferred stock of such series or (2) by conversion into or exchange for shares of our capital stock ranking junior to the preferred stock of such series as to dividends and upon liquidation.

If fewer than all of the outstanding shares of preferred stock of any series are to be redeemed, we will determine the number of shares that may be redeemed pro rata from the holders of record of such shares in proportion to the number of such shares held or for which redemption is requested by such holder or by any other equitable manner that we determine. Such determination will reflect adjustments to avoid redemption of fractional shares.

Unless otherwise specified in the prospectus supplement, we will mail notice of redemption at least 10 days but not more than 60 days before the redemption date to each holder of record of preferred stock to be redeemed at the address shown on our stock transfer books. Each notice shall state:

• the redemption date;

• the number of shares and series of preferred stock to be redeemed;

• the redemption price;

• the place or places where certificates for such preferred stock are to be surrendered for payment of the redemption price;

• that dividends on the shares to be redeemed will cease to accrue on such redemption date;

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• the date on which the holder’s conversion rights, if any, as to such shares shall terminate; and

• the specific number of shares to be redeemed from each such holder if fewer than all the shares of any series are to be redeemed.

If notice of redemption has been given and we have set aside the funds necessary for such redemption in trust for the benefit of the holders of any shares called for redemption, then from and after the redemption date, dividends will cease to accrue on such shares, and all rights of the holders of such shares will terminate, except the right to receive the redemption price.

Voting Rights. Holders of preferred stock will not have any voting rights, except as required by law or as indicated in the applicable prospectus supplement.

Unless otherwise provided for under the terms of any series of preferred stock, no consent or vote of the holders of shares of preferred stock or any series thereof shall be required for any amendment to our certificate of incorporation that would increase the number of authorized shares of preferred stock or the number of authorized shares of any series thereof or decrease the number of authorized shares of preferred stock or the number of authorized shares of any series thereof (but not below the number of authorized shares of preferred stock or such series, as the case may be, then outstanding).

Conversion Rights. The terms and conditions, if any, upon which any series of preferred stock is convertible into shares of our common stock will be set forth in the applicable prospectus supplement relating thereto. Such terms will include the number of shares of common stock into which the shares of preferred stock are convertible, the conversion price, rate or manner of calculation thereof, the conversion period, provisions as to whether conversion will be at our option or at the option of the holders of the preferred stock, the events requiring an adjustment of the conversion price and provisions affecting conversion in the event of the redemption.

Transfer Agent and Registrar. The transfer agent and registrar for the preferred stock will be set forth in the applicable prospectus supplement.

Series X Non-Voting Convertible Preferred Stock

Pursuant to our Certificate of Designation of Preferences, Rights and Limitations of the Series X Preferred Stock, or the Certificate of Designation, we designated 24,847 shares of our authorized and unissued preferred stock as Series X Preferred Stock, and established the rights, preferences and privileges of the Series X Preferred Stock, which are summarized below.

Conversion. Each share of Series X Preferred Stock outstanding is convertible at any time at the option of the holder into 1,000 shares of common stock, subject to certain beneficial ownership limitations, including that a holder of Series X Preferred Stock is prohibited from converting shares of Series X Preferred Stock into shares of common stock if, as a result of such conversion, such holder (together with its affiliates and any other persons acting as a group together with the holder or any of its affiliates) would beneficially own more than a specified percentage (to be initially set at 19.99% and thereafter adjusted by the holder to a number not to exceed 19.99%) of the total number of shares of common stock issued and outstanding immediately after giving effect to such conversion.

Voting Rights. Except as otherwise required by law, the Series X Preferred Stock does not have voting rights. However, as long as any shares of Series X Preferred Stock are outstanding, we will not, without the affirmative vote of the holders of a majority of the then outstanding shares of the Series X Preferred Stock, (i) alter or change adversely the powers, preferences or rights given to the Series X Preferred Stock or alter or amend the Certificate of Designation, amend or repeal any provision of, or add any provision to, our certificate of

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incorporation or by-laws, or file any articles of amendment, certificate of designations, preferences, limitations and relative rights of any series of preferred stock, if such action would adversely alter or change the preferences, rights, privileges or powers of, or restrictions provided for the benefit of the Series X Preferred Stock, (ii) issue further shares of Series X Preferred Stock or increase or decrease (other than by conversion) the number of authorized shares of Series X Preferred Stock, or (iii) enter into any agreement with respect to any of the foregoing.

Dividends. Holders of Series X Preferred Stock are entitled to receive dividends on shares of Series X Preferred Stock equal, on an as-converted-to-common-stock basis, and in the same form as dividends actually paid on shares of the common stock.

Liquidation and Dissolution. The Series X Preferred Stock ranks on parity with common stock upon any such liquidation, dissolution or winding-up.

Provisions of Our Certificate of Incorporation and By-laws and Delaware Law That May Have Anti-Takeover Effects

Certain provisions of our certificate of incorporation and by-laws may have the effect of making it more difficult for a third party to acquire, or of discouraging a third party from attempting to acquire, control of us. Such provisions could limit the price that certain investors might be willing to pay in the future for shares of our common stock and may limit the ability of stockholders to remove current management or directors or approve transactions that stockholders may deem to be in their best interest and, therefore, could adversely affect the price of our common stock.

Staggered Board; Removal of Directors. Our certificate of incorporation and by-laws divide our board of directors into three classes with staggered three-year terms. In addition, a director may be removed only for cause and only by the affirmative vote of the holders of at least 75% of the votes that all of our stockholders would be entitled to cast in an annual election of directors. Any vacancy on our board of directors, including a vacancy resulting from an enlargement of our board of directors, may be filled only by vote of a majority of our directors then in office. The classification of our board of directors and the limitations on the removal of directors and filling of vacancies could make it more difficult for a third party to acquire, or discourage a third party from seeking to acquire, control of our company.

Stockholder Action by Written Consent; Special Meetings. Our certificate of incorporation provides that any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting of such holders and may not be effected by any consent in writing by such holders. Our certificate of incorporation and by-laws also provide that, except as otherwise required by law, special meetings of our stockholders can only be called by our chairman of the board of directors, our chief executive officer or our board of directors.

Exclusive Forum Selection. Our 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 the Court of Chancery does not have jurisdiction, the federal district court for the District of Delaware) shall be the sole and exclusive forum for (1) any derivative action or proceeding brought on our behalf, (2) any action asserting a claim of breach of a fiduciary duty owed by any of our directors, officers or employees to our company or stockholders, (3) any action asserting a claim against us arising pursuant to any provision of the DGCL or our certificate of incorporation or by-laws, or (4) any action asserting a claim against us governed by the internal affairs doctrine. These choice of forum provisions will not apply to claims arising under the Securities Act, the Exchange Act or any other claim for which federal courts have exclusive jurisdiction. Although our certificate of incorporation contains the choice of forum provision described above, it is possible that a court could rule that such a provision is inapplicable for a particular claim or action or that such provision is unenforceable.

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Advance Notice Requirements for Stockholder Proposals. Our by-laws establish an advance notice procedure for stockholder proposals to be brought before an annual meeting of stockholders, including proposed nominations of persons for election to our board of directors. Stockholders at an annual meeting may consider proposals or nominations specified in the notice of meeting or brought before the meeting by or at the direction of our board of directors or by a stockholder of record on the record date for the meeting who is entitled to vote at the meeting and who has delivered timely written notice in proper form to our secretary of the stockholder’s intention to bring such business before the meeting. These provisions could have the effect of delaying until the next stockholder meeting stockholder actions that are favored by the holders of a majority of our outstanding voting securities.

These provisions of Delaware law, our certificate of incorporation and our by-laws may have the effect of deterring hostile takeovers or delaying changes in our control or in our management. These provisions are intended to enhance the likelihood of continued stability in the composition of our board of directors and in the policies they implement, and to discourage certain types of transactions that may involve an actual or threatened change of our control. These provisions are designed to reduce our vulnerability to an unsolicited acquisition proposal. The provisions also are intended 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, as a consequence, they also may inhibit fluctuations in the market price of our shares that could result from actual or rumored takeover attempts.

Delaware Business Combination Statute. We are subject to Section 203 of the DGCL, or Section 203, which prohibits a Delaware corporation from engaging in business combinations with an interested stockholder. An interested stockholder is generally defined as an entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation or any entity or person affiliated with or controlling or controlled by such entity or person, or interested stockholder. Section 203 provides that an interested stockholder may not engage in business combinations with the corporation for a period of three years after the date that such stockholder became an interested stockholder, with the following exceptions:

• before such date, the board of directors of the corporation approved either the business combination or the transaction that resulted in the stockholder becoming an interested stockholder;

• upon completion of the transaction that resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction began, excluding for purposes of determining the voting stock outstanding (but not the outstanding voting stock owned by the interested stockholder) those shares owned (i) by persons who are directors and also officers and (ii) employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or

• on or after such date, the business combination is approved by the board of directors and authorized at an annual or special meeting of the stockholders, and not by written consent, by the affirmative vote of at least 66 2/3% of the outstanding voting stock that is not owned by the interested stockholder.

In general, Section 203 defines business combinations to include the following:

• any merger or consolidation involving the corporation and the interested stockholder;

• any sale, lease, transfer, pledge or other disposition of 10% or more of the assets of the corporation to or with the interested stockholder;

• subject to certain exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation to the interested stockholder;

• any transaction involving the corporation that has the effect of increasing the proportionate share of the stock or any class or series of the corporation beneficially owned by the interested stockholder; or

• the receipt by the interested stockholder of the benefit of any loss, advances, guarantees, pledges or other financial benefits by or through the corporation.

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DESCRIPTION OF WARRANTS

We may issue warrants to purchase common stock, preferred stock or debt securities. We may offer warrants separately or together with one or more additional warrants, common stock, preferred stock or debt securities, or any combination of those securities in the form of units, as described in the applicable prospectus supplement. If we issue warrants as part of a unit, the accompanying prospectus supplement will specify whether those warrants may be separated from the other securities in the unit prior to the expiration date of the warrants. The applicable prospectus supplement will also describe the following terms of any warrants:

• the specific designation and aggregate number of, and the offering price at which we will issue, the warrants;

• the currency or currency units in which the offering price, if any, and the exercise price are payable;

• the date on which the right to exercise the warrants will begin and the date on which that right will expire or, if you may not continuously exercise the warrants throughout that period, the specific date or dates on which you may exercise the warrants;

• whether the warrants are to be sold separately or with other securities as parts of units;

• whether the warrants will be issued in definitive or global form or in any combination of these forms, although, in any case, the form of a warrant included in a unit will correspond to the form of the unit and of any security included in that unit;

• any applicable material U.S. federal income tax consequences;

• the identity of the warrant agent for the warrants and of any other depositaries, execution or paying agents, transfer agents, registrars or other agents;

• the proposed listing, if any, of the warrants or any securities purchasable upon exercise of the warrants on any securities exchange;

• the designation and terms of any equity securities purchasable upon exercise of the warrants;

• the designation, aggregate principal amount, currency and terms of any debt securities that may be purchased upon exercise of the warrants;

• if applicable, the designation and terms of the preferred stock with which the warrants are issued and, the number of warrants issued with each security;

• if applicable, the date from and after which any warrants issued as part of a unit and the related common stock, preferred stock or debt securities will be separately transferable;

• the number of shares of common stock or preferred stock purchasable upon exercise of a warrant and the price at which those shares may be purchased;

• if applicable, the minimum or maximum amount of the warrants that may be exercised at any one time;

• information with respect to book-entry procedures, if any;

• the anti-dilution provisions of, and other provisions for changes to or adjustment in the exercise price of, the warrants, if any;

• any redemption or call provisions; and

• any additional terms of the warrants, including terms, procedures and limitations relating to the exchange or exercise of the warrants.

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DESCRIPTION OF UNITS

We may issue units consisting of one or more of the other securities described in this prospectus in any combination, as described in the applicable prospectus supplement. We may issue units in one or more series, which will be described in the applicable prospectus supplement. The applicable prospectus supplement will also describe the following terms of any units:

• the designation and the terms of the units and of the securities constituting the units, including whether and under what circumstances the securities comprising the units may be traded separately;

• the identity of any unit agent for the units, if applicable, and of any other depositaries, execution or paying agents, transfer agents, registrars or other agents;

• any additional terms of the governing unit agreement, if applicable;

• any additional provisions for the issuance, payment, settlement, transfer or exchange of the units or of the debt securities, common stock, preferred stock or warrants constituting the units; and

• any applicable material U.S. federal income tax consequences.

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FORMS OF SECURITIES

Each debt security, warrant and unit will be represented either by a certificate issued in definitive form to a particular investor or by one or more global securities representing the entire issuance of securities. Unless the applicable prospectus supplement provides otherwise, certificated securities in definitive form and global securities will be issued in registered form. Definitive securities name you or your nominee as the owner of the security, and in order to transfer or exchange these securities or to receive payments other than interest or other interim payments, you or your nominee must physically deliver the securities to the trustee, registrar, paying agent or other agent, as applicable. Global securities name a depositary or its nominee as the owner of the debt securities, warrants or units represented by these global securities. The depositary maintains a computerized system that will reflect each investor’s beneficial ownership of the securities through an account maintained by the investor with its broker/dealer, bank, trust company or other representative, as we explain more fully below.

Global Securities

We may issue the debt securities of a particular series, warrants and units in the form of one or more fully registered global securities that will be deposited with a depositary or its nominee identified in the applicable prospectus supplement and registered in the name of that depositary or nominee. In those cases, one or more global securities will be issued in a denomination or aggregate denominations equal to the portion of the aggregate principal or face amount of the securities to be represented by global securities. Unless and until it is exchanged in whole for securities in definitive registered form, a global security may not be transferred except as a whole by and among the depositary for the global security, the nominees of the depositary or any successors of the depositary or those nominees.

If not described below, any specific terms of the depositary arrangement with respect to any securities to be represented by a global security will be described in the prospectus supplement relating to those securities. We anticipate that the following provisions will apply to all depositary arrangements.

Ownership of beneficial interests in a global security will be limited to persons, called participants, that have accounts with the depositary or persons that may hold interests through participants. Upon the issuance of a global security, the depositary will credit, on its book-entry registration and transfer system, the participants’ accounts with the respective principal or face amounts of the securities beneficially owned by the participants. Any dealers, underwriters or agents participating in the distribution of the securities will designate the accounts to be credited. Ownership of beneficial interests in a global security will be shown on, and the transfer of ownership interests will be effected only through, records maintained by the depositary, with respect to interests of participants, and on the records of participants, with respect to interests of persons holding through participants. The laws of some states may require that some purchasers of securities take physical delivery of these securities in definitive form. These laws may impair your ability to own, transfer or pledge beneficial interests in global securities.

So long as the depositary, or its nominee, is the registered owner of a global security, that depositary or its nominee, as the case may be, will be considered the sole owner or holder of the securities represented by the global security for all purposes under the applicable indenture, warrant agreement or unit agreement. Except as described below, owners of beneficial interests in a global security will not be entitled to have the securities represented by the global security registered in their names, will not receive or be entitled to receive physical delivery of the securities in definitive form and will not be considered the owners or holders of the securities under the applicable indenture, warrant agreement or unit agreement. Accordingly, each person owning a beneficial interest in a global security must rely on the procedures of the depositary for that global security and, if that person is not a participant, on the procedures of the participant through which the person owns its interest, to exercise any rights of a holder under the applicable indenture, warrant agreement or unit agreement. We understand that under existing industry practices, if we request any action of holders or if an owner of a beneficial interest in a global security desires to give or take any action that a holder is entitled to give or take

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under the applicable indenture, warrant agreement or unit agreement, the depositary for the global security would authorize the participants holding the relevant beneficial interests to give or take that action, and the participants would authorize beneficial owners owning through them to give or take that action or would otherwise act upon the instructions of beneficial owners holding through them.

Principal, premium, if any, and interest payments on debt securities, and any payments to holders with respect to warrants or units, represented by a global security registered in the name of a depositary or its nominee will be made to the depositary or its nominee, as the case may be, as the registered owner of the global security. None of us, or any trustee, warrant agent, unit agent or any other agent of ours, or any agent of any trustee, warrant agent or unit agent will have any responsibility or liability for any aspect of the records relating to payments made on account of beneficial ownership interests in the global security or for maintaining, supervising or reviewing any records relating to those beneficial ownership interests.

We expect that the depositary for any of the securities represented by a global security, upon receipt of any payment to holders of principal, premium, interest or other distribution of underlying securities or other property on that registered global security, will immediately credit participants’ accounts in amounts proportionate to their respective beneficial interests in that global security as shown on the records of the depositary. We also expect that payments by participants to owners of beneficial interests in a global security held through participants will be governed by standing customer instructions and customary practices, as is now the case with the securities held for the accounts of customers or registered in “street name,” and will be the responsibility of those participants.

If the depositary for any of the securities represented by a global security is at any time unwilling or unable to continue as depositary or ceases to be a clearing agency registered under the Exchange Act, and a successor depositary registered as a clearing agency under the Exchange Act is not appointed by us within 90 days, we will issue securities in definitive form in exchange for the global security that had been held by the depositary. Any securities issued in definitive form in exchange for a global security will be registered in the name or names that the depositary gives to the relevant trustee, warrant agent, unit agent or other relevant agent of ours or theirs. It is expected that the depositary’s instructions will be based upon directions received by the depositary from participants with respect to ownership of beneficial interests in the global security that had been held by the depositary.

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PLAN OF DISTRIBUTION

We may sell securities:

• through underwriters;

• through dealers;

• through agents;

• directly to purchasers; or

• through a combination of any of these methods of sale.

In addition, we may issue the securities as a dividend or distribution or in a subscription rights offering to our existing security holders. This prospectus may be used in connection with any offering of our securities through any of these methods or other methods described in the applicable prospectus supplement.

We may directly solicit offers to purchase securities, or agents may be designated to solicit such offers. We will, in the prospectus supplement relating to such offering, name any agent that could be viewed as an underwriter under the Securities Act, and describe any commissions that we must pay. Any such agent will be acting on a best efforts basis for the period of its appointment or, if indicated in the applicable prospectus supplement, on a firm commitment basis.

The distribution of the securities may be effected from time to time in one or more transactions:

• at a fixed price, or prices, which may be changed from time to time;

• at market prices prevailing at the time of sale;

• at prices related to such prevailing market prices; or

• at negotiated prices.

Each prospectus supplement will describe the method of distribution of the securities and any applicable restrictions.

The prospectus supplement with respect to the securities of a particular series will describe the terms of the offering of the securities, including the following:

• the name of the agent or any underwriters;

• the public offering or purchase price and the proceeds we will receive from the sale of the securities;

• any discounts and commissions to be allowed or re-allowed or paid to the agent or underwriters;

• all other items constituting underwriting compensation;

• any discounts and commissions to be allowed or re-allowed or paid to dealers; and

• any exchanges on which the securities will be listed.

If any underwriters or agents are utilized in the sale of the securities in respect of which this prospectus is delivered, we will enter into an underwriting agreement or other agreement with them at the time of sale to them, and we will set forth in the prospectus supplement relating to such offering the names of the underwriters or agents and the terms of the related agreement with them.

If a dealer is utilized in the sale of the securities in respect of which this prospectus is delivered, we will sell such securities to the dealer, as principal. The dealer may then resell such securities to the public at varying prices to be determined by such dealer at the time of resale.

If we offer securities in a subscription rights offering to our existing security holders, we may enter into a standby underwriting agreement with dealers, acting as standby underwriters. We may pay the standby

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underwriters a commitment fee for the securities they commit to purchase on a standby basis. If we do not enter into a standby underwriting arrangement, we may retain a dealer-manager to manage a subscription rights offering for us.

Remarketing firms, agents, underwriters, dealers and other persons may be entitled under agreements which they may enter into with us to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, and may be customers of, engage in transactions with or perform services for us in the ordinary course of business.

If so indicated in the applicable prospectus supplement, we will authorize underwriters or other persons acting as our agents to solicit offers by certain institutions to purchase securities from us pursuant to delayed delivery contracts providing for payment and delivery on the date stated in the prospectus supplement. Each contract will be for an amount not less than, and the aggregate amount of securities sold pursuant to such contracts shall not be less nor more than, the respective amounts stated in the prospectus supplement. Institutions with whom the contracts, when authorized, may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and other institutions, but shall in all cases be subject to our approval. Delayed delivery contracts will not be subject to any conditions except that:

• the purchase by an institution of the securities covered under that contract shall not at the time of delivery be prohibited under the laws of the jurisdiction to which that institution is subject; and

• if the securities are also being sold to underwriters acting as principals for their own account, the underwriters shall have purchased such securities not sold for delayed delivery. The underwriters and other persons acting as our agents will not have any responsibility in respect of the validity or performance of delayed delivery contracts.

Certain agents, underwriters and dealers, and their associates and affiliates may be customers of, have borrowing relationships with, engage in other transactions with, and/or perform services, including investment banking services, for us or one or more of our respective affiliates in the ordinary course of business.

In order to facilitate the offering of the securities, any underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the securities or any other securities the prices of which may be used to determine payments on such securities. Specifically, any underwriters may overallot in connection with the offering, creating a short position for their own accounts. In addition, to cover overallotments or to stabilize the price of the securities or of any such other securities, the underwriters may bid for, and purchase, the securities or any such other securities in the open market. Finally, in any offering of the securities through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allowed to an underwriter or a dealer for distributing the securities in the offering if the syndicate repurchases previously distributed securities in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of the securities above independent market levels. Any such underwriters are not required to engage in these activities and may end any of these activities at any time.

Under Rule 15c6-1 of the Exchange Act, trades in the secondary market generally are required to settle in one business day, unless the parties to any such trade expressly agree otherwise. The applicable prospectus supplement may provide that the original issue date for your securities may be more than one scheduled business day after the trade date for your securities. Accordingly, in such a case, if you wish to trade securities on any date prior to the first business day before the original issue date for your securities, you will be required, by virtue of the fact that your securities initially are expected to settle in more than one scheduled business day after the trade date for your securities, to make alternative settlement arrangements to prevent a failed settlement.

The securities may be new issues of securities and may have no established trading market. The securities may or may not be listed on a national securities exchange. We can make no assurance as to the liquidity of or the existence of trading markets for any of the securities.

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LEGAL MATTERS

Unless the applicable prospectus supplement indicates otherwise, the validity of the securities in respect of which this prospectus is being delivered will be passed upon by Wilmer Cutler Pickering Hale and Dorr LLP.

EXPERTS

The financial statements of Rein Therapeutics, Inc. as of December 31, 2024 and 2023 and for the years ended December 31, 2024 and 2023 have been audited by Marcum LLP, an independent registered public accounting firm, as set forth in their report (which contains an explanatory paragraph relating to substantial doubt about the ability of Rein Therapeutics, Inc. to continue as a going concern as described in Note 1 to the financial statements), and are incorporated by reference in this prospectus and in the registration statement of which this prospectus is a part have been so incorporated in reliance on such report given upon such firm as experts in auditing and accounting.

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$6,000,000

Common Stock

PROSPECTUS SUPPLEMENT

July 30, 2025

FAQ

How much capital can Rein Therapeutics (RNTX) raise under the Yorkville agreement?

Up to $6 million in prepaid advances, of which $1 million has already been drawn.

What price will Yorkville pay for RNTX shares?

The lower of 115% of the prior-day VWAP or 95% of the lowest VWAP in the preceding seven trading days, but not below $0.28.

How many new shares could be issued?

At a reference price of $1.41, up to 4.26 million shares, raising total shares outstanding to roughly 27.3 million.

What will Rein use the proceeds for?

R&D for LTI-03 and LTI-01, potential in-licensing, working capital, and other corporate needs.

Does the agreement limit Yorkville’s ownership?

Yes. Yorkville cannot own more than 4.99% of voting stock at any time without approval.

Is shareholder approval required?

Only if share issuance would exceed 19.9% of outstanding stock, per Nasdaq rules.