Material Agreement, Financial Obligation, Private Placement (Form 8-K)

Pre-Paid AdvanceAgreement

As previously disclosed by Rein Therapeutics, Inc. (the "Company", "we", "us") in a Current Report on Form 8-Kfiled on July 30, 2025, on July 29, 2025 (the "Effective Date"), we entered into a Pre-Paid AdvanceAgreement (the "PPA") with YA II PN, Ltd., a Cayman Islands exempt limited partnership ("Yorkville"). In accordance with the terms of the PPA, we may request pre-paid advancesof up to $6.0 million from Yorkville (each, a "Pre-Paid Advance")over a 12-month period,subject to certain limitations and conditions set forth in the PPA. Each Pre-Paid Advancewill be purchased by Yorkville at 95% of the face amount of the Pre-Paid Advance.Each additional Pre-Paid Advanceshall be subject to the consent of Yorkville. Interest shall accrue on the outstanding balance of any Pre-Paid Advanceat an annual rate of 8%, subject to an increase to 18% upon events of default described in the Pre-Paid AdvanceAgreement. All Pre-PaidAdvances are due and payable on the 12-monthanniversary of their issuance.

At any time that there is an outstanding balance under any Pre-Paid Advances, Yorkville mayprovide written notice requiring us to issue and sell shares of our common stock to Yorkville, which shall be offset against and reduce the amounts outstanding under the Pre-Paid Advances.An initial Pre-Paid Advanceof $1.0 million was purchased on the Effective Date by Yorkville, for net proceeds of $0.95 million. As of the date of this report, we have issued 479,036 shares of our common stock, at an average price per share of approximately $1.06, to Yorkville, which were offset against $500,000 of the outstanding initial Pre-Paid Advance.

Second Pre-PaidAdvance

On September 8, 2025, and pursuant our request, Yorkville purchased a second Pre-Paid Advanceof $1.0 million, for which we received net proceeds of $0.95 million.

The foregoing description of the PPA and the Pre-PaidAdvances is not complete and is qualified in its entirety by reference to the PPA filed as an exhibit to this Current Report on Form 8-K.

The information set forth in Item 1.01 of this Current Report on Form 8-K underis incorporated herein by reference.

The information set forth under Item 1.01 of this Current Report on Form 8-Kis incorporated herein by reference.

On September 8, 2025, we issued and sold a Pre-PaidAdvance to Yorkville in a private placement pursuant to the exemption from the registration requirements of the Securities Act of 1933, as amended (the "Securities Act") in reliance on the exemption from registration provided by Section 4(a)(2) of the Securities Act. There was no underwriter involved in the transaction.