Form of Exchange Letter

Inducement Offer to Exchange 2023 Warrant to Purchase Common Stock

The Company has the requisite corporate power and authority and power to enter into this letter agreement and to consummate the Warrant Exchange and the other transactions contemplated hereby.

Assuming the accuracy of your representations and warranties set forth below, no registration under the Securities Act is required for the issuance of the Pre-Funded Warrants by the Company to you as contemplated by this letter agreement or the issuance of shares of Common Stock upon exercise of the Pre-Funded Warrants.

Assuming the accuracy of your representations and warranties set forth below, neither the Company, nor any person acting on its behalf has, directly or indirectly, made any offers or sales of securities or solicited any offers to buy any security, under circumstances that would cause the transactions contemplated by this letter agreement to be integrated with prior offerings by the Company for purposes of the Securities Act and require the registration of any such security under the Securities Act.

Neither the Company nor any person acting on behalf of the Company has offered the securities by any form of general solicitation or advertising. The Company has offered the securities only to you and certain other “accredited investors” within the meaning of Rule 501 under the Securities Act.

You have the requisite power and authority to enter into this letter agreement and consummate the Warrant Exchange and the other transactions contemplated hereby.

You are the record and beneficial owner of, and have valid and marketable title to, the 2023 Warrant being exchanged by you pursuant to this letter agreement, free and clear of any lien, pledge, restriction or other encumbrance (other than restrictions arising pursuant to applicable securities laws), and have the absolute and unrestricted right, power and capacity to surrender and exchange the 2023 Warrant being exchanged by you pursuant to this letter agreement, free and clear of any lien, pledge, restriction or other encumbrance. You are not a party to or bound by, and the 2023 Warrant being exchanged by you pursuant to this letter agreement is not subject to, any agreement, understanding or other arrangement (i) granting any options, warrant or right of first refusal with respect to such warrant to any person, (ii) restricting its right to surrender and exchange such 2023 Warrant as contemplated by this letter agreement, or (iii) restricting any other of its rights with respect to such 2023 Warrant.

You understand that the Pre-Funded Warrants are, and the shares of Common Stock issuable upon exercise thereof, are “restricted securities” and have not been registered under the Securities Act or any applicable state securities law. You are acquiring the Pre-Funded Warrants and any shares of Common Stock issuable upon exercise thereof (collectively, the “2025 Securities”) as principal for your own account and not with a view to or for distributing or reselling such securities or any part thereof in violation of the Securities Act or any applicable state securities law, have no present intention of distributing any of the 2025 Securities in violation of the Securities Act or any applicable state securities law and have no direct or indirect arrangement or understandings with any other persons to distribute or regarding the distribution of the 2025 Securities in violation of the Securities Act or any applicable state securities law (this representation and warranty not limiting your right to sell the securities in compliance with applicable federal and state securities laws). You are acquiring the 2025 Securities in the ordinary course of your business.

You are acquiring the 2025 Securities for own account, not as nominee or agent, for the purpose of investment and not with a view to the resale or distribution of any part thereof in violation of the Securities Act, and you have no present intention of selling, granting any participation in, or otherwise distributing the same in violation of the Securities Act.

At the time you were offered the securities, you were, and as of the date hereof it is, and on each date on which you exercise the Pre-Funded Warrants, you will be an “accredited investor” as defined in Rule 501(a) the Securities Act.

You, either alone or together with your representatives, have such knowledge, sophistication and experience in business and financial matters so as to be capable of evaluating the merits and risks of the prospective investment in the securities, and have so evaluated the merits and risks of such investment. You are able to bear the economic risk of an investment in the securities and, at the present time, are able to afford a complete loss of such investment.

You have had an opportunity to receive, review and understand all information related to the Company requested by it and to ask questions of and receive answers from the Company regarding the Company, its business and the terms and conditions of the offering of the Securities, and have conducted and completed your own independent due diligence.

You are not, to your knowledge, purchasing the securities as a result of any general solicitation or general advertisement.

The undersigned is the Holder of Warrant No. __ (the “Warrant”) issued by Rein Therapeutics, Inc., a Delaware corporation (the “Company”). Capitalized terms used herein and not otherwise defined herein have the respective meanings set forth in the Warrant.

The undersigned hereby exercises its right to purchase Warrant Shares pursuant to the Warrant.

The Holder intends that payment of the Exercise Price shall be made as (check one):

Cash Exercise

“Cashless Exercise” under Section 10 of the Warrant

If the Holder has elected a Cash Exercise, the Holder shall pay the sum of $____ in immediately available funds to the Company in accordance with the terms of the Warrant.

Pursuant to this Exercise Notice, the Company shall deliver to the Holder Warrant Shares determined in accordance with the terms of the Warrant.

By its delivery of this Exercise Notice, the undersigned represents and warrants to the Company that in giving effect to the exercise evidenced hereby the Holder will not beneficially own in excess of the number of shares of Common Stock (as determined in accordance with Section 13(d) of the Securities Exchange Act of 1934, as amended) permitted to be owned under Section 11(a) of the Warrant to which this notice relates.