UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K/A

(Amendment No. 1)

(Mark One)

For the fiscal year ended December 31, 2025

OR

FOR THE TRANSITION PERIOD FROM ________ TO________

Commission file number: 001-38130

Rein Therapeutics, Inc.

(Exact name of Registrant as Specified in Its Charter)

Registrant’s telephone number, including area code: (737) 802-1989

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐ No ☒

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. Yes ☐ No ☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes ☒ No ☐

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

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C.7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to § 240.10D-1(b). ☐

As of June 30, 2025, the last business day of the Registrant’s most recently completed second fiscal quarter, the aggregate market value of the voting and non-voting common equity held by non-affiliates of the Registrant, based on the last reported sale price of the shares of common stock on The Nasdaq Capital Market was $32,264,569.

As of March 24, 2025, the Registrant has 28,039,032 shares of Common Stock, $0.001 par value per share, outstanding.

EXPLANATORY NOTE

This Amendment No. 1 (this “Amendment”) amends the Annual Report on Form 10-K for the year ended December 31, 2025 of Rein Therapeutics, Inc. filed with the Securities and Exchange Commission (the “SEC”) on March 26, 2026 (the “Original Form 10-K”). The purpose of this Amendment is to amend Part III, Items 10 through 14, of the Original Form 10-K to include information previously omitted from the Original Form 10-K in reliance on General Instruction G(3) to the Annual Report on Form 10-K. Accordingly, Part III of the Original Form 10-K is hereby amended and restated as set forth below and the reference on the cover page of the Original Form 10-K to the incorporation by reference of our definitive proxy statement into Part III of the Original Form 10-K is hereby deleted.

TABLE OF CONTENTS

PART III

Item 10. Directors, Executive Officers and Corporate Governance.

Board of Directors

Our board of directors (the “Board”) is divided into three classes, with members of each class holding office for staggered three-year terms. There are currently two Class I directors (Brian Windsor, Ph.D. and Alan A. Musso), whose terms expire at the 2027 annual meeting of stockholders; one Class II director (William C. Fairey), whose term expires at the 2025 annual meeting of stockholders; and two Class III directors (Reinhard J. Ambros, Ph.D. and Josef H. von Rickenbach), whose terms expire at the 2026 annual meeting of stockholders.

Set forth below are the names of and certain information for each Board member. The information presented includes each director’s principal occupation and business experience for the past five or more years and the names of other public companies for which he has served as a director during the past five years.

Class I Directors

Brian Windsor, Ph.D. has served as our President, Chief Executive Officer, and as a member of the Board since March 2024. Prior to becoming President and Chief Executive Officer, Dr. Windsor served as our President and Chief Operating Officer from October 2023 to March 2024. From July 2013 to October 2023, Dr. Windsor served as President, Chief Executive Officer and a director of Lung Therapeutics, Inc. (“Lung”) until the closing of our acquisition of Lung in October 2023 (the “Lung Acquisition”). From September 2019 to March 2022, Dr. Windsor served as a director and the Chief Science Officer of TFF Pharmaceuticals, Inc., a public biopharmaceutical company that Lung spun out into an independent company. From January 2018 to March 2022, Dr. Windsor provided consulting services to TFF Pharmaceuticals, Inc. in the areas of science and technology. From November 2009 to March 2013, Dr. Windsor served as President of Enavail, LLC, a specialty pharmaceutical manufacturing company, where he oversaw all aspects of the company’s pharmaceutical drug development. Before joining Enavail, Dr. Windsor directed portfolio company management for Emergent Technologies, Inc., an early stage technology venture creation and management company, where he served as managing director or president for ten portfolio companies. Dr. Windsor holds a B.S. and a Ph.D. in molecular biology from The University of Texas at Austin. We believe Dr. Windsor is qualified to serve on the Board due to his extensive knowledge of our company, scientific knowledge, and extensive management and financial experience in the life sciences industry.

Alan A. Musso has served as a member of the Board since October 2023. Since August 2023, Mr. Musso has served as the chief financial officer of Fulcrum Therapeutics, a public clinical-stage biopharmaceutical company focused on improving the lives of patients with genetically defined rare diseases in areas of high unmet medical need. Previously, he served as the chief financial officer of ReViral Ltd., a privately held, clinical-stage biopharmaceutical company focused on discovering, developing, and commercializing novel antiviral therapeutics that target respiratory syncytial virus (RSV), that was acquired by Pfizer Inc. in June 2022, from October 2019 until September 2022. Prior to ReViral,

from September 2018 to September 2019, Mr. Musso was the chief financial officer and treasurer at Peloton Therapeutics Inc., a company focused on the development of novel small molecule therapeutic candidates for the treatment of cancer. While at Peloton, Mr. Musso helped to prepare the company for an initial public offering until the company was acquired by Merck & Co. in July 2019. Prior to Peloton, from November 2014 to August 2018, Mr. Musso served as the chief financial officer and treasurer at Bellicum Pharmaceuticals, Inc., a public biotechnology company focused on discovering and developing novel, controllable cellular immunotherapies for various forms of cancer. Prior to Bellicum, from February 2002 to November 2014, Mr. Musso served in various positions at Targacept, Inc., a public biopharmaceutical company. Mr. Musso spent the early part of his career as a senior internal auditor for Pfizer as well as a certified public accountant for KPMG International. Mr. Musso served as a member of the board of directors of Lung from April 2022 until the closing of the Lung Acquisition in October 2023. Mr. Musso holds a B.S. in accounting from Saint Mary’s College of California, and a Master’s Degree from the Thunderbird School of Global Management. We believe Mr. Musso is qualified to serve on the Board due to his extensive management and financial experience in the life sciences industry.

Class II Director

William C. Fairey has served as a member of the Board since October 2023. Mr. Fairey served as executive vice president and chief commercial officer of MyoKardia, Inc., a clinical-stage biopharmaceutical company discovering and developing targeted therapies for the treatment of serious cardiovascular diseases, from January 2019 to November 2020 prior to its acquisition by Bristol Myers Squibb in October 2020. Prior to MyoKardia, from January 2018 to January 2019, Mr. Fairey served as executive vice president and chief operating officer of ChemoCentryx, Inc., a public biopharmaceutical company focused on discovering, developing and commercializing orally administered therapeutics to treat autoimmune diseases, inflammatory disorders and cancer. During that time, Mr. Fairey was responsible for the sales, marketing, medical affairs and market access functions, including commercialization of late stages compounds. Prior to ChemoCentryx, Mr. Fairey served in various roles at Actelion Pharmaceuticals Ltd., a pharmaceutical company, and its subsidiaries, from January 2001 to December 2017. Actelion was acquired by Johnson & Johnson in 2017. Mr. Fairey has served on the board of directors of Mirum Pharmaceuticals, Inc., a public biopharmaceutical company focused on the identification, acquisition, development and commercialization of novel therapies for debilitating rare and orphan diseases, since August 2021 and on the board of directors of Ascendis Pharma A/S, a public biopharmaceutical company organized under the laws of the Kingdom of Denmark, since August 2022. Mr. Fairey served as a member of the board of directors of Lung from August 2021 until the closing of the Lung Acquisition. Mr. Fairey holds a B.S. in biology from the University of Oregon and an M.B.A. from Saint Mary’s College of California. We believe Mr. Fairey is qualified to serve on the Board due to his significant experience in the life sciences industry and his experience on corporate boards of public companies.

Class III Directors

Reinhard J. Ambros, Ph.D. has served as a member of the Board since June 2013. From 2005 until 2017, Dr. Ambros served as global head of Novartis Venture Funds, a globally acting corporate biotechnology venture fund. Prior to that, from 1999 until 2005, he served as head of group strategic planning and as global head of business development and licensing for cardiovascular and metabolic diseases at Novartis AG, a multinational pharmaceutical company. He currently serves on the boards of several biotechnology companies in Europe and the U.S. He also served as advisor to German and Swiss Government Biotechnology Funds. Dr. Ambros received an M.S. from the University of Regensburg, Germany, and a Ph.D. in medicinal chemistry and pharmacology from the University of Regensburg, Germany. We believe Dr. Ambros is qualified to serve on the Board due to his management experience in the biotechnology sector and his service on other boards of directors.

Josef H. von Rickenbach has served as a member of the Board since June 2019. Mr. von Rickenbach has served as managing director of Stet Vision LLC, a life sciences business advisory firm, since December 2018. Mr. von Rickenbach served as a director of NextGen Acquisition Corp. II, a special purpose acquisition company, from March 2021 until its merger with Virgin Holdings, Inc. in December 2021, and as a director of NextGen Acquisition Corporation, a special purpose acquisition company, from October 2020 until its merger with Xos Inc. in August 2021. He co-founded and served as President and Chief Executive Officer of HelioVision, Inc., a biotechnology company, from April 2017 until its acquisition by Aldeyra Therapeutics, Inc. in February 2019. Previously, Mr. von Rickenbach was a founder of Parexel International Corporation, a global clinical research organization and biopharmaceutical services company, in 1982 and served as a director, chairman of the board, and Chief Executive Officer of Parexel

from 1983 until the company’s acquisition by Pamplona Capital Management, LLP in September 2017. Mr. von Rickenbach received an M.B.A. from Harvard Business School and a B.A. in business economics from the University of Lucerne in Switzerland. We believe Mr. von Rickenbach is qualified to serve on the Board due to his management experience in the biotechnology sector, his decades of experience in drug development, and his service on other boards of directors.

Executive Officers

The following table sets forth the name, age and position of each of our executive officers.

* Dr. Windsor is a member of our board of directors. See “Board of Directors—Class I Directors” for more information about Dr. Windsor.

** Mr. Cunningham is not directly compensated by the Company for his services as our Interim Chief Financial Officer.

Timothy M. Cunningham has served as our Interim Chief Financial Officer since May 2024. Since September 2020, Mr. Cunningham has served as chief financial officer consultant at Danforth Advisors, LLC, a national consulting firm providing financial, accounting and reporting services to the life science industry. Mr. Cunningham has served as Chief Financial Officer for Neuphoria Therapeutics, Inc. (formerly Bionomics Limited) since May 2023, and he previously served as Acting Chief Financial Officer for Peak Bio, Inc. from September 2022 to January 2024 and for SAB Biotherapeutics, Inc. from October 2020 to December 2021. Prior to joining Danforth, Mr. Cunningham served as Chief Financial Officer at Organogenesis from July 2016 to August 2020. Prior to joining Organogenesis, Mr. Cunningham held leadership positions with several different public and private companies over the course of his career, which began at KPMG LLP followed by PricewaterhouseCoopers LLP. Mr. Cunningham holds an MBA from Boston University, a BS in Accounting from Boston College and is a CPA in the state of Florida.

Corporate Governance Matters

The Board believes that good corporate governance is important to ensure that the Company is managed for the long-term benefit of stockholders. This section describes key corporate governance guidelines and practices that the Board has adopted. Complete copies of our Corporate Governance Guidelines, committee charters and Code of Business Conduct and Ethics available on the “Investors & Media—Governance” section of our website, which is located at www.reintx.com. Alternatively, you can request a copy of any of these documents by writing to us at Rein Therapeutics, Inc., 12407 N. Mopac Expy. Suite 250 #390, Austin, Texas 78758, Attention: Brian Windsor, Ph.D., President and Chief Executive Officer.

Corporate Governance Guidelines

The Board has adopted Corporate Governance Guidelines to assist in the exercise of its duties and responsibilities and to serve the best interests of the Company and our stockholders. These guidelines, which provide a framework for the conduct of the Board’s business, provide that:

Board Leadership Structure

Our Corporate Governance Guidelines provide that the Nominating and Corporate Governance Committee shall periodically assess the Board’s leadership structure, including whether the offices of Chief Executive Officer and Chair of the Board should be separate. Our guidelines provide the Board with flexibility to determine whether the two roles should be combined or separated based upon our needs and the Board’s assessment of its leadership from time to time. We currently separate the roles of Chief Executive Officer and the Chair of the Board. Separating the duties of the Chair of the Board from the duties of the Chief Executive Officer allows our Chief Executive Officer to focus on our day-to-day business, while allowing the Chair of the Board to lead the Board in its fundamental role of providing advice to and independent oversight of management. Specifically, the Chair of the Board presides over meetings of the Board, facilitates communications between management and the Board, and assists with other corporate governance matters.

The Board has three standing committees that currently consist of, and are chaired by, independent directors. The Board delegates substantial responsibilities to the committees, which then report their activities and actions back to the full Board. We believe that the independent committees of the Board and their chairpersons promote effective independent governance. We believe this structure represents an appropriate allocation of roles and responsibilities for the Company at this time because it strikes an effective balance between management and independent leadership participation in our Board proceedings.

The Board oversees our risk management processes directly and through its committees. Our management is responsible for risk management on a day-to-day basis. The role of the Board and its committees is to oversee the risk management activities of management. The Board fulfills this duty by discussing with management the policies and practices utilized by management in assessing and managing risks and providing input on those policies and practices. In general, the Board oversees risk management activities relating to business strategy, acquisitions, capital allocation, organizational structure and certain operational risks; the Audit Committee oversees risk management activities related to financial controls, legal and compliance risks and cybersecurity risks; the Compensation Committee oversees risk management activities relating to our compensation policies and practices; and the Nominating and Corporate Governance Committee oversees risk management activities relating to the composition of the Board and management succession planning. Each committee reports to the full Board on a regular basis, including reports with respect to the committee’s risk oversight activities as appropriate. In addition, since risk issues often overlap, committees from time to time request that the full Board discuss particular risks.

Board Determination of Independence

Applicable Nasdaq rules require a majority of a listed company’s board of directors to be comprised of independent directors within one year of listing. In addition, the Nasdaq rules require that, subject to specified exceptions, each member of a listed company’s audit, compensation and nominating and corporate governance committees be independent. Audit committee members must also satisfy the independence criteria set forth in Rule 10A-3 under the Exchange Act and compensation committee members must also satisfy the independence criteria set forth in Rule 10C-1 under the Exchange Act. Under applicable Nasdaq rules, a director will only qualify as an “independent director” if, in the opinion of the listed company’s board of directors, that person does not have a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. In order to be considered independent for purposes of Rule 10A-3, a member of an audit committee of a listed company may not, other than in his or her capacity as a member of the audit committee, the board of directors, or any other board committee, accept, directly or indirectly, any consulting, advisory, or other compensatory fee from the listed company

or any of its subsidiaries or otherwise be an affiliated person of the listed company or any of its subsidiaries. In order to be considered independent for purposes of Rule 10C-1, the board must consider, for each member of a compensation committee of a listed company, all factors specifically relevant to determining whether a director has a relationship to such company which is material to that director’s ability to be independent from management in connection with the duties of a compensation committee member, including, but not limited to: the source of compensation of the director, including any consulting, advisory or other compensatory fee paid by such company to the director; and whether the director is affiliated with the company or any of its subsidiaries or affiliates.

Based upon information requested from and provided by each director concerning his background, employment and affiliations, including family relationships, the Board believes that each director, with the exception of Dr. Windsor, is an “independent director” as defined under applicable Nasdaq rules, including, in the case of all the members of the Audit Committee, the independence criteria set forth in Rule 10A-3 under the Exchange Act, and in the case of all the members of the Compensation Committee, the independence criteria set forth in Rule 10C-1 under the Exchange Act. In making such determination, the Board considered the relationships that each such non-employee director has with the Company and all other facts and circumstances that the Board deemed relevant in determining his independence, including the beneficial ownership of our capital stock by each non-employee director. Dr. Windsor is not an independent director under these rules because Dr. Windsor is our President and Chief Executive Officer.

Board of Director Meetings and Attendance

The Board held eight meetings during the year ended December 31, 2025. During 2025, each of our incumbent directors attended at least 75% of the aggregate of the number of meetings held by the Board during the period which the person has been a director and the number of meetings held by all committees of the Board on which such director then served (during the periods that such person served). Our Corporate Governance Guidelines provide that directors are expected to attend our annual meeting of stockholders. Four of our directors then in office attended the 2025 annual meeting of stockholders.

Communicating with our Directors

The Board provides a process for stockholders to send communications to the Board. Any interested party with concerns about the Company may report such concerns to the Board, or the Chair of the Board, or otherwise the Chair of the Nominating and Corporate Governance Committee, by submitting a written communication to the attention of such director at the following address:

c/o Rein Therapeutics, Inc.

12407 N. Mopac Expy. Suite 250 #390

Austin, Texas 78758

You may submit your concern anonymously or confidentially by postal mail. You may also indicate whether you are a stockholder, customer, supplier, or other interested party.

A copy of any such written communication may also be forwarded to our legal counsel, and a copy of such communication may be retained for a reasonable period of time. The director may discuss the matter with our legal counsel, with independent advisors, with non-management directors, or with our management, or may take other action or no action as the director determines in good faith, using reasonable judgment and discretion.

Communications may be forwarded to all directors if they relate to important substantive matters and include suggestions or comments that may be important for the directors to know. In general, communications relating to corporate governance and long-term corporate strategy are more likely to be forwarded than communications relating to ordinary business affairs, personal grievances, and matters as to which we tend to receive repetitive or duplicative communications.

The Audit Committee oversees the procedures for the receipt, retention, and treatment of complaints received by us regarding accounting, internal accounting controls, or audit matters, and the confidential, anonymous submission by employees of concerns regarding questionable accounting, internal accounting controls, or auditing matters. We have also established a toll-free telephone number for the reporting of such activity, which is 866-869-5217.

Committees of the Board of Directors

We have established an Audit Committee in accordance with Section 3(a)(58)(A) of the Exchange Act, a Compensation Committee, and a Nominating and Corporate Governance Committee. Each of these committees operates under a charter that has been approved by the Board. A copy of each committee’s charter can be found under the “Investors & Media—Governance” section of our website, located at www.reintx.com.

Audit Committee

The current members of the Audit Committee are Reinhard J. Ambros, Ph.D., Alan A. Musso, and Josef H. von Rickenbach. Mr. Musso serves as Chair of the Audit Committee. In 2025, the Audit Committee met four times. The Audit Committee’s responsibilities include:

All audit and non-audit services, other than de minimis non-audit services, to be provided to us by our independent registered public accounting firm must be approved in advance by the Audit Committee.

The Board has determined that Mr. Musso is an “audit committee financial expert” as defined in applicable SEC rules and that each of the members of the Audit Committee possesses the financial sophistication required for audit committee members under Nasdaq rules. We believe that the composition of the Audit Committee meets the requirements for independence under current Nasdaq and SEC rules and regulations.

Compensation Committee

The current members of the Compensation Committee are Dr. Ambros, William C. Fairey, and Mr. Musso. Dr. Ambros serves as the Chair of the Compensation Committee. In 2025, the Compensation Committee met once. The Compensation Committee’s responsibilities include:

The Compensation Committee may delegate to one or more executive officers the power to grant options or other stock awards pursuant to our incentive plans to employees of the Company who are not executive officers or Senior Vice Presidents.

We believe that the composition of the Compensation Committee meets the requirements for independence under current Nasdaq and SEC rules and regulations.

Nominating and Corporate Governance Committee

The current members of the Nominating and Corporate Governance Committee are Mr. Fairey and Mr. von Rickenbach. Mr. Fairey serves as the Chair of the Nominating and Corporate Governance Committee. In 2025, the Nominating and Corporate Governance Committee met once. The Nominating and Corporate Governance Committee’s responsibilities include:

We believe that the composition of the Nominating and Corporate Governance Committee meets the requirements for independence under current Nasdaq rules and regulations.

Director Nomination Process

The process followed by the Nominating and Corporate Governance Committee to identify and evaluate director candidates includes requests to Board members and others for recommendations, meetings from time to time to evaluate biographical information and background material relating to potential candidates and interviews of selected candidates by members of the Nominating and Corporate Governance Committee and the Board.

Criteria

In considering whether to recommend to the Board any particular candidate for inclusion in the Board’s slate of recommended director nominees, including candidates recommended by stockholders, the Nominating and Corporate Governance Committee applies the criteria set forth in our Corporate Governance Guidelines. The Nominating and Corporate Governance Committee believes that the Board, taken as a whole, should embody a broad range of skills, experiences and backgrounds. In this regard, the Nominating and Corporate Governance Committee considers a wide range of criteria when determining and assessing director candidates, including the candidate’s integrity, business acumen, knowledge of our business and industry, the ability to act in the interests of all stockholders and lack of conflicts of interest. The Nominating and Corporate Governance Committee does not make any particular weighting of any particular criteria or characteristic in evaluating nominees and directors.

Stockholder Nominations

Stockholders may recommend individuals to the Nominating and Corporate Governance Committee for consideration as potential director candidates by submitting their names, together with appropriate biographical information and background materials and a statement as to whether the stockholder or group of stockholders making the recommendation has beneficially owned more than 5% of our common stock for at least a year as of the date such recommendation is made, to Rein Therapeutics, Inc., Attention: Nominating and Corporate Governance Committee, 12407 N. Mopac Expy. Suite 250 #390, Austin, Texas 78758. Assuming that appropriate biographical and background material has been provided in accordance with the procedures set forth in our definitive proxy statement for the 2025 annual meeting of stockholders filed with the SEC on May 12, 2025 (the “2025 Proxy Statement) under the heading “Other Matters--Stockholder Proposals for our 2026 Annual Meeting”, the Nominating and Corporate Governance Committee will evaluate stockholder-recommended candidates by following substantially the same process, and applying substantially the same criteria, as it follows for candidates submitted by others. If the Board determines to nominate a stockholder-recommended candidate and recommends his or her election, then his or her name will be included in our proxy card for the next annual meeting of stockholders. Stockholders also have the right under our by-laws to directly nominate director candidates, without any action or recommendation on the part of the Nominating and Corporate Governance Committee or the Board, by following the procedures set forth in the 2025 Proxy Statement under “Other Matters—Stockholder Proposals for our 2026 Annual Meeting.”

Insider Trading Policy

We have adopted an insider trading policy governing the purchase, sale and/or other dispositions of Company securities by our directors, officers, employees and other covered persons. We believe our Insider Trading Policy is reasonably designed to promote compliance with insider trading laws, rules and regulations, and Nasdaq listing standards. A copy of our Insider Trading Policy is filed as Exhibit 19.1 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2025.

Anti-Hedging Policy

Our Insider Trading Policy also expressly prohibits all of our employees, including our named executive officers (“NEOs”), as well as our directors, from engaging in speculative transactions in our stock, including short sales, puts/calls, hedging transactions and margin accounts or pledges.

Clawback Policy

In November 2023, we adopted a “clawback policy” compliant with Nasdaq listing standards which provides that, in the event that we are required to prepare an accounting restatement for periods ending on or after October 2, 2023, we will attempt to recover from our current or former executive officers the pre-tax amount of incentive-based compensation in excess of what would have been paid to such executive officer after giving effect to the accounting restatement during the three completed fiscal years immediately preceding the earlier of (i) the date the Board, or a committee of the Board, or the officer or officers of the Company authorized to take such action if board action is not required, concludes, or reasonably should have concluded, that the Company is required to prepare an accounting restatement, or (ii) the date a court, regulator, or other legally authorized body directs the company to prepare an accounting restatement. For purposes of the policy, incentive-based compensation means any compensation that is granted, earned or vested based wholly or in part upon the attainment of any measures determined and presented in accordance with the accounting principles used in preparing the Company’s financial statements, and any measures that are derived wholly or in part from such measures (whether or not such measures are presented within the company’s financial statements or included in a filing made with the SEC); stock price; and total stockholder return. If the incentive-based compensation is based on our stock price or total stockholder return and the amount of excess incentive-based compensation is not calculable directly from the information in an accounting restatement, the amount recovered shall be based on a reasonable estimate of the effect of the accounting restatement on the stock price or total stockholder return upon which the incentive-based compensation was received.

Compensation Committee Interlocks and Insider Participation

None of our executive officers serves, or in the past have served, as a member of the board of directors or compensation committee, or other committee serving an equivalent function, of any entity that has one or more executive officers who serve as members of the Board or the Compensation Committee. None of the members of the Compensation Committee is, or ever has been, an officer or employee of the Company.

Code of Business Conduct and Ethics

We have adopted a written Code of Business Conduct and Ethics that applies to our directors, officers and employees, including our principal executive officer and principal financial officer. A copy of our Code of Business Conduct and Ethics is available on the “Investors & Media—Governance” section of our website, which is located at www.reintx.com. The Board is responsible for overseeing the code of business conduct and ethics and must approve any waivers of the code for directors and officers. If we make any substantive amendments to, or grant any waivers from, our Code of Business Conduct and Ethics for any officer or director, we will disclose the nature of such amendment or waiver on our website or in a Current Report on Form 8-K.

Item 11. Executive Compensation.

This section discusses the material elements of our executive compensation policies for our NEOs and the most important factors relevant to an analysis of these policies. Our NEOs for the fiscal year ended December 31, 2025 were as follows:

In addition, this section provides qualitative information regarding the manner and context in which compensation is awarded to and earned by our NEOs and is intended to place in perspective the data presented in the following tables and the corresponding narrative.

Summary Compensation Table

The following table sets forth information regarding compensation awarded to, earned by or paid to our NEOs during the years indicated.

Narrative Disclosure to Summary Compensation Table

We review compensation for our executive officers annually. The material terms of the elements of our executive compensation program for 2025 are described below.

The Compensation Committee sets base salaries and bonus targets, and grants bonuses and equity incentive awards to our executive officers. In setting base salaries and bonus targets and granting equity incentive awards, the Compensation Committee considers compensation for comparable positions in the market, the historical compensation levels of our executives, individual and corporate performance as compared to our expectations and objectives, our desire to motivate our employees to achieve short- and long-term results that are in the best interests of our stockholders, and make a long-term commitment to the Company. In granting bonuses, the Compensation Committee considers corporate and individual performance.

As part of our annual compensation process, our President and Chief Executive Officer prepares performance evaluations for the other executive officers and recommends annual salary increases, annual stock option awards and cash bonuses to the Compensation Committee. The Compensation Committee conducts a performance evaluation of our President and Chief Executive Officer. The Compensation Committee consults with the Board as to the achievement of corporate objectives that drive compensation awards.

In August 2024, the Compensation Committee engaged Radford as its independent compensation consultant to provide comparative data on executive and director compensation practices in our industry and assess our executives’ and directors’ compensation relative to comparable companies for 2024.

Base Salary

We use base salaries to recognize the experience, skills, knowledge and responsibilities required of all our employees, including our NEOs. None of our NEOs is currently party to an employment agreement or other agreement or arrangement that provides for automatic or scheduled increases in base salary.

On November 12, 2024, based upon comparative data on executive compensation provided by Radford, the Board, upon recommendation by the Compensation Committee, increased Dr. Windsor’s annual base salary to $575,000, effective as of December 1, 2024.

Cash Incentives

The Compensation Committee awards annual performance-based cash bonuses to our executive officers for up to a specific percentage of salary as a vehicle to reward achievement of value-driving milestones and recognize individual performance.

Pursuant to the terms of his employment agreement, Dr. Windsor had bonus targets of 50%, 50% and 45% of his annual base salary for 2024 based on performance against goals and at the discretion of the Board.

On November 12, 2024, the Board, upon recommendation of the Compensation Committee, increased Dr. Windsor’s target performance-based cash bonus to 50% of his annual base salary for 2024.

On January 31, 2025, the Board, upon recommendation of the Compensation Committee, determined to award a cash bonus of $227,812 to Dr. Windsor for his performance in 2024. In addition, the Board, upon recommendation of the Compensation Committee, determined to award a cash bonus of $287,500 to Dr. Windsor for his performance in 2025.

Equity Incentives

Although we do not have a formal policy with respect to the grant of equity incentive awards to our executive officers, or any formal equity ownership guidelines applicable to them, we believe that equity grants provide our executives with a strong link to our long-term performance, create an ownership culture and help to align the interests of our executive officers and our stockholders. In addition, we believe that equity grants with a time-based vesting feature promote executive retention because this feature incentivizes our executive officers to remain in our employment during the vesting period, and equity grants with a performance-based feature incentivize our executive officers to focus on what we see as key business goals. Accordingly, the Compensation Committee periodically reviews the equity incentive compensation of our executive officers and from time to time may grant equity incentive awards to them in the form of stock options.

In December 2024, the Board granted an option to purchase 517,500 shares of our common stock to Dr. Windsor in 2024. This option vests as to 25% of the shares on December 2, 2025 and thereafter in equal monthly installments through December 2, 2028.

Employment Agreement

In February 2014, Lung entered into an employment agreement with Brian Windsor, Ph.D., as amended by a letter agreement in February 2023 and as further amended by a letter agreement in October 2023. Pursuant to the employment agreement, as amended, Dr. Windsor is currently entitled to an annual base salary of $575,000 and is eligible to receive an annual bonus based on a bonus target of 50% of his annual base salary based on performance against goals and at the discretion of the Board. In addition, pursuant to the employment agreement, in the event that Dr. Windsor is terminated without cause or resigns for good reason, then, subject to the execution of a release agreement, Dr. Windsor will be eligible to receive twelve months’ base salary in the form of severance payments, less statutory deductions and withholdings, payable in the form of salary continuation.

Other Agreements

In May 2024, we entered into a consulting agreement with Danforth Advisors, LLC, pursuant to which we will pay Danforth an agreed upon hourly rate for Mr. Cunningham’s services as our Interim Chief Financial Officer and will reimburse Danforth for expenses. The consulting agreement may be terminated by the Company or Danforth with cause, upon 30 days written notice, and without cause, upon 60 days written notice.

We have also entered into employee confidentiality and inventions agreements with each of our NEOs under which each NEO has agreed to (i) protect our confidential and proprietary information and (ii) assign to us related intellectual property developed during the course of his employment.

401(k) Retirement Plan

We maintain a 401(k) retirement plan that is intended to be a tax-qualified defined contribution plan under Section 401(k) of the Internal Revenue Code. In general, all of our employees are eligible to participate, beginning on the first day of the month following commencement of their employment. The 401(k) plan includes a salary deferral arrangement pursuant to which participants may elect to reduce their current compensation by up to the statutorily prescribed limit, equal to $23,000 in 2024 and $23,500 in 2025, and have the amount of the reduction contributed to the 401(k) plan. Participants over the age of 50 are entitled to an additional catch-up contribution up to the statutorily prescribed limit, equal to $7,500 in 2024 and 2025.

In March 2021, the Compensation Committee adopted a 100% match on the first 4% of eligible compensation, retroactively effective to January 1, 2021, which remained applicable in 2024 and 2025. This was a non-voluntary contribution by the Company for 2024 and 2025 and will be a non-voluntary contribution by the Company for 2026.

Outstanding Equity Awards at Fiscal Year End 2025

The following table sets forth information regarding outstanding equity awards held by our NEOs as of December 31, 2025:

Director Compensation

Our non-employee directors receive compensation under our non-employee director compensation program. Under our non-employee director compensation program, we pay our non-employee directors a cash retainer for service on the Board and for service on each committee on which the director is a member. The chair of each committee and the Chair of the Board receive higher retainers for such service. These fees are payable in arrears in four equal quarterly installments on the last day of each quarter, subject to proration for any portion of such quarter that the director is not serving on the Board, on such committee or in such position. We also make initial and annual equity grants to our non-employee directors and reimburse our non-employee directors for reasonable travel and out-of-pocket expenses incurred in connection with attending the Board and committee meetings.

Non-Employee Director Compensation Program

Under our non-employee director compensation program, the fees payable to non-employee directors for service on the Board and for service on each committee of the Board on which the director is a member are as follows:

In addition, under our non-employee director compensation program, each non-employee director who serves on the Board for at least six months receives an option to purchase 17,500 shares of common stock immediately following

each annual meeting of stockholders. Each of these options vest in full on the earlier of the first anniversary of the grant date and the date of the next annual meeting of stockholders, subject to the non-employee director’s continued service as a director. In addition, each new member of the Board receives an option to purchase 35,000 shares of common stock upon his or her initial election to the Board. Each of these options vest in four equal annual installments from his or her election, subject to his or her continued service as a director.

We do not pay any compensation to Dr. Windsor, our President and Chief Executive Officer, in connection with his service on the Board. The compensation that we paid to Dr. Windsor is discussed earlier in this “Executive Compensation” section.

The following table sets forth information regarding compensation earned by any of our directors who served in such capacity at any time during 2025. Dr. Aivado resigned from the Board on February 16, 2026.

As of December 31, 2025, any of our directors who served in such capacity at any time during 2025 held the following stock options, including stock options assumed by us in the Lung Acquisition, all of which were granted under (a) our 2017 Stock Incentive Plan, (b) our 2021 Stock Incentive Plan, and (c) Lung’s 2013 Long-Term Incentive Plan:

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.

Unless otherwise provided below, the following table sets forth information regarding beneficial ownership of our shares of common stock as of March 31, 2026, by:

Beneficial ownership is determined in accordance with the rules and regulations of the SEC and includes voting or investment power with respect to common stock. Percentage of beneficial ownership is based on 28,039,032 shares of common stock outstanding as of March 31, 2026. In addition, shares of common stock subject to options, warrants, or other rights currently exercisable or exercisable within 60 days of March 31, 2026, are deemed outstanding and beneficially owned for the purpose of computing the percentage beneficially owned by (i) the person or entity holding such options, warrants or other rights (but not any other person or entity) and (ii) the directors and executive officers as a group. Except as otherwise noted, the persons and entities in this table have sole voting and investing power with respect to all of the shares of common stock beneficially owned by them, subject to community property laws, where applicable. Except as otherwise set forth below, the address of the beneficial owner is c/o Rein Therapeutics, Inc., 12407 N. Mopac Expy. Suite 250 #390, Austin, Texas 78758.

* Represents beneficial ownership of less than 1% of our outstanding stock.

Securities Authorized for Issuance Under Equity Compensation Plans

The following table contains information about our equity compensation plans as of December 31, 2025. As of December 31, 2025, we had five equity compensation plans, each of which was approved by our stockholders: our 2006 Equity Incentive Plan, as amended (the “2006 Plan”), our 2016 Stock Incentive Plan (the “2016 Plan”), our 2017 Stock Incentive Plan (the “2017 Plan”), our 2021 Stock Incentive Plan (the “2021 Plan”), and our 2017 Employee Stock Purchase Plan (the “2017 ESPP”). The Company also assumed Lung’s 2013 Long-Term Incentive Plan (the “2013 Plan”) as a result of the Lung Acquisition.

Equity Compensation Plan Information

Item 13. Certain Relationships and Related Transactions, and Director Independence.

Since January 1, 2024, we have engaged in the following transactions in which the amount involved exceeded the lesser of $120,000 or one percent of our total assets at year-end for fiscal years 2025 and 2024, and any of our executive officers, directors, or beneficial holders of more than 5% of any class of voting securities, or any of their affiliates, had a direct or indirect material interest. We believe that all of these transactions were on terms comparable to terms that could have been obtained from unrelated third parties.

Warrant Exchanges and April 2025 Private Placement

On April 21, 2025, we entered into privately negotiated letter agreements with certain holders of warrants to purchase up to an aggregate of 2,353,500 shares of our common stock, which we issued and sold in connection with the Lung Acquisition ("2023 Warrants"), including entities affiliated with Bio Partners, a greater than 5% beneficial holder of outstanding shares of our common stock, which holders agreed, in exchange for pre-funded warrants to purchase an aggregate of 1,300,500 shares of common stock at an exercise price of $0.001 per share (the “Exchange Pre-Funded Warrants”), to surrender 2023 Warrants to purchase an aggregate of 1,300,500 shares of common stock for cancellation and make an aggregate cash payment of $1.599 per share into which the Exchange Pre-Funded Warrants are exercisable on or before April 24, 2025 (the “Warrant Exchanges”).

In addition, on April 21, 2025, an entity affiliated with Bios Partners (the “Bios Purchaser”) agreed to purchase additional pre-funded warrants to purchase 312,695 shares of common stock in a private placement (the “Placement Pre-Funded Warrants” and together with the Exchange Pre-Funded Warrants, the “Pre-Funded Warrants”) pursuant to a subscription agreement, at a price of $1.599 per share underlying the Placement Pre-Funded Warrants (the “April 2025 Private Placement”). The April 2025 Private Placement closed on April 24, 2025.

In connection with the April 2025 Private Placement, we entered into a Registration Rights Agreement (the “April 2025 Registration Rights Agreement”) with the Bios Purchaser. Pursuant to the April 2025 Registration Rights Agreement, we agreed that we will prepare and file a resale registration statement with the SEC within 90 calendar days following the date on which the Bios Purchaser has informed us that Bios Partners and its affiliates beneficially owns more than 9.99% of the outstanding shares of common stock or the voting power of the Company (the “Filing Deadline”). We agreed to use our commercially reasonable best efforts to cause this registration statement to be declared effective by the SEC within 30 calendar days of the Filing Deadline.

Under the April 2025 Registration Rights Agreement, we also agreed, among other things, to indemnify the Bios Purchaser, its officers, directors, agents, partners, members, managers, stockholders, affiliates and employees under the registration statement from certain liabilities and pay all fees and expenses (excluding any underwriting discounts and selling commissions and all legal fees and expenses of legal counsel for Bios Partners, except for reasonable and documented fees and expenses in an amount not to exceed $30,000 in connection with the review of the registration statement) incident to our obligations under the April 2025 Registration Rights Agreement.

Indemnification Agreements

Our restated certificate of incorporation, as amended, provides that we will indemnify our directors and officers to the fullest extent permitted by Delaware law. In addition, we have entered into indemnification agreements with each of our officers and directors that may be broader in scope than the specific indemnification provisions contained in the Delaware General Corporation Law. See “Executive Compensation—Limitations on Liability and Indemnification” for additional information regarding these agreements.

Policies and Procedures for Related Person Transactions

The Board has adopted a written related person transaction policy to set forth policies and procedures for the review of any transaction, arrangement, or relationship in which we are a participant, the amount involved exceeds $120,000, and one of our executive officers, directors, or 5% stockholders, or their immediate family members, each of whom we refer to as a “related person,” has a direct or indirect material interest.

If a related person proposes to enter into such a transaction, arrangement, or relationship, which we refer to as a “related person transaction,” the related person must report the proposed related person transaction to our Chief Executive Officer. The policy calls for the proposed related person transaction to be reviewed and approved by the Audit Committee. Whenever practicable, the reporting, review, and approval will occur prior to entry into the transaction. If advance review and approval is not practicable, the committee will review and, in its discretion, may ratify the related person transaction. The policy also permits the Chair of the Audit Committee to review and, if deemed appropriate, approve proposed related person transactions that arise between committee meetings, subject to ratification by the committee at its next meeting. Any related person transactions that are ongoing in nature will be reviewed annually.

A related person transaction reviewed under the policy will be considered approved or ratified if it is authorized by the Audit Committee after full disclosure of the related person’s interest in the transaction. As appropriate for the circumstances, the committee will review and consider:

The Audit Committee may approve or ratify the transaction only if the committee determines that, under all of the circumstances, the transaction is in our best interests. The Audit Committee may impose any conditions on the related person transaction that it deems appropriate.

In addition to the transactions that are excluded by the instructions to the SEC’s related-person transaction disclosure rule, the Board has determined that the following transactions do not create a material direct or indirect interest on behalf of related persons and, therefore, are not related-person transactions for purposes of this policy:

The policy provides that transactions involving compensation of executive officers shall be reviewed and approved by the Compensation Committee in the manner specified in its charter.

Limitations on Liability and Indemnification

As permitted by Delaware law, we adopted provisions in our restated certificate of incorporation, as amended, that limit or eliminate the personal liability of our directors. Our restated certificate of incorporation, as amended, limits the personal liability of directors for breach of fiduciary duty to the maximum extent permitted by the General Corporation Law of the State of Delaware (“DGCL”) and provides that no director will have personal liability to us or to our stockholders for monetary damages for breach of fiduciary duty. However, these provisions do not eliminate or limit the liability of any of our directors:

Any amendment to or repeal of these provisions will not eliminate or reduce the effect of these provisions in respect of any act, omission or claim that occurred or arose prior to such amendment or repeal. If the DGCL is amended to provide for further limitations on the personal liability of directors of corporations, then the personal liability of our directors will be further limited to the greatest extent permitted by the DGCL.

In addition, our restated certificate of incorporation, as amended, provides that we must indemnify our directors and officers and we must advance expenses, including attorneys’ fees, to our directors and officers in connection with legal proceedings, subject to very limited exceptions.

We maintain a general liability insurance policy that covers specified liabilities of our directors and officers arising out of claims based on acts or omissions in their capacities as directors or officers. In addition, we entered into indemnification agreements with each of our officers and directors. These indemnification agreements require us, among other things, to indemnify each such director or officer for some expenses, including attorneys’ fees, judgments, fines and settlement amounts, incurred by him or her in any action or proceeding arising out of his or her service as one of our directors or officers.

Some of our non-employee directors may, through their relationships with their employers, be insured or indemnified against specified liabilities incurred in their capacities as members of the Board.

Insofar as indemnification for liabilities arising under the Securities Act of 1933, as amended (the “Securities Act”), may be permitted to directors, executive officers or persons controlling us, in the opinion of the SEC, such indemnification is against public policy as expressed in the Securities Act and is therefore unenforceable.

Item 14. Principal Accounting Fees and Services.

Audit Fees and Services

CBIZ CPAs P.C. (“CBIZ”) served as our independent registered public accounting firm for the fiscal year ended December 31, 2025, and Marcum LLP (“Marcum”) served as our independent registered public accounting firm for fiscal year ended December 31, 2024. The following table summarizes the fees of CBIZ and Marcum for the fiscal years ended December 31, 2025 and 2024, respectively. All such services and fees were pre-approved by the Audit Committee in accordance with the “Pre-Approval Policies and Procedures” described below.

Pre-Approval Policies and Procedures

The Audit Committee has adopted procedures requiring the pre-approval of all non-audit services performed by our independent registered public accounting firm in order to assure that these services do not impair the auditor’s independence. These procedures generally approve the performance of specific services subject to a cost limit for all such services. This general approval is to be reviewed, and if necessary modified, at least annually. Management must obtain the specific prior approval of the Audit Committee for each engagement of the independent registered public accounting firm to perform other audit-related or other non-audit services. The Audit Committee does not delegate its responsibility to approve services performed by the independent registered public accounting firm to any member of management. The Audit Committee has delegated authority to the Chair of the Audit Committee to pre-approve any audit or non-audit service to be provided to us by our independent registered public accounting firm provided that the fees for such services do not exceed $100,000. Any approval of services by the Chair of the Audit Committee pursuant to this delegated authority must be reported to the Audit Committee at the next meeting of the committee.

The standard applied by the Audit Committee, or the Chair of the Audit Committee, in determining whether to grant approval of any type of non-audit service, or of any specific engagement to perform a non-audit service, is whether the services to be performed, the compensation to be paid therefore and other related factors are consistent with the independent registered public accounting firm’s independence under guidelines of the SEC and applicable professional standards. Relevant considerations include whether the work product is likely to be subject to, or implicated in, audit procedures during the audit of our financial statements, whether the independent registered public accounting firm would be functioning in the role of management or in an advocacy role, whether the independent registered public accounting firm’s performance of the service would enhance our ability to manage or control risk or improve audit quality, whether such performance would increase efficiency because of the independent registered public accounting firm’s familiarity with our business, personnel, culture, systems, risk profile and other factors, and whether the amount of fees involved, or the non-audit services portion of the total fees payable to the independent registered public accounting firm in the period would tend to reduce the independent registered public accounting firm’s ability to exercise independent judgment in performing the audit.

PART IV

Item 15. Exhibits and Financial Statement Schedules.

(a) Financial Statements

The response to this portion of Item 15 is incorporated by reference from the Original Filing into this Amendment.

(b) Exhibits.

* Indicates management contract or compensatory plan.
+ In accordance with Item 601(b)(10)(iv) of Regulation S-K, certain information (indicated by “[**]”) has been excluded from this exhibit because it is both not material and private or confidential. A copy of the omitted portion will be furnished to the SEC upon request.
# Certain schedules and similar attachments have been omitted pursuant to Item 601(a)(5) of Regulation S-K. The registrant undertakes to furnish supplemental copies of any of the omitted schedules upon request by the SEC.
^ SEC File No. 333-218474

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this Report to be signed on its behalf by the undersigned, thereunto duly authorized.