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

Item 1.01 Entry into a Definitive Material Agreement.

On February 24 and 27, 2026, Rein Therapeutics, Inc. (the "Company") entered into separate securities purchase agreements (each a "Purchase Agreement") with three institutional investors pursuant to which the Company issued and sold to the investors, in a private placement, unsecured promissory notes in the aggregate original principal amount of $2,875,000 (each a "Note"). Pursuant to the Purchase Agreements, the Company issued and sold the Notes to the investors for the aggregate purchase price of $2,300,000, inclusive of an original issue discount of 20%.

The Notes have a stated maturity date of the earlier of (i) the date of the closing of the next issuance and sale of securities of the Company, in a single transaction or series of related transactions, to investors resulting in gross proceeds to the Company of at least $10,000,000 (exclusive of the Note proceeds) or (ii) June 30, 2026. The Company's obligations under the Notes are unsecured. There is no interest payable under the Notes other than the 20% original issue discount. The Purchase Agreements contain representations, warranties, covenants and other terms customary for agreements of such nature.

Item 2.03 Creation of a Direct Financial Obligation or an Obligation under an Off-BalanceSheet Arrangement of a Registrant.

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

Item 3.02 Unregistered Sales of Equity Securities.

The information set forth under Item 1.01 of this Current Report on Form 8-Kis incorporated herein by reference. The Notes sold pursuant to the Purchase Agreements were offered and sold pursuant to exemptions from the registration requirements of the Securities Act of 1933, as amended, afforded by Section 4(a)(2) thereof and Rule 506 of Regulation D promulgated thereunder, for the sale of securities not involving a public offering.