Nature of the Business	6 Months Ended
Jun. 30, 2026
Accounting Policies [Abstract]
Nature of the Business	1. Nature of the Business Rein Therapeutics, Inc. (“Company”) is a Delaware corporation formed in August 2001 under the name Renegade Therapeutics, Inc. In February 2007, the Company changed its name to Aileron Therapeutics, Inc. and in January 2025 changed its name to Rein Therapeutics, Inc. The Company is a clinical stage biopharmaceutical company focused on developing novel therapies for the treatment of fibrosis indications with no approved or limited effective treatments. The Company currently has one product candidate in clinical development, LTI-03. The Company is a clinical-stage biotechnology company subject to significant risks and uncertainties, including the need for substantial additional financing, reliance on third parties, clinical trial risks, dependence on key personnel, protection of proprietary technology, and compliance with regulatory requirements. Its lead product candidate, LTI-03, is being developed for the treatment of idiopathic pulmonary fibrosis (IPF) and has completed Phase 1a and Phase 1b clinical trials; the Company is currently conducting the Phase 2 RENEW trial, a multi-center, randomized, double-blind, placebo-controlled study expected to enroll approximately 120 patients across multiple global sites, with interim data anticipated in the fourth quarter of 2026. The Company initiated patient screening in May 2025, received regulatory clearances in Europe and the United Kingdom, and dosed its first patient in March 2026. The Company’s second product candidate, LTI-01, previously in development for loculated pleural effusion, has been paused indefinitely as the Company prioritizes resources toward LTI-03, and the timing of any potential resumption remains uncertain and dependent on additional financing and the success of LTI-03. Liquidity In May 2026, the Company completed an underwritten public offering of 57,500,000 shares of its common stock at a public offering price of $1.00 per share, or the May 2026 Offering. Aggregate gross proceeds from the May 2026 Offering were $57,500, and net proceeds to the Company were approximately $53,099 after deducting underwriting discounts, commissions, and offering expenses of approximately $4,401. Management believes that, based on the Company’s current operating plan, the Company’s cash, cash equivalents and investments of $43,627 as of June 30, 2026 will be sufficient to enable the Company to fund its planned operating expense and capital expenditure requirements into the first quarter of 2028. The Company believes that the funds are sufficient to enable the Company to complete the Phase 2 RENEW clinical trial of LTI-03. The Company’s estimate as to how long it expects its existing cash, cash equivalents and investments to be able to continue to fund its operations is based on assumptions that may prove to be wrong, and the Company could use its available capital resources sooner than it currently expects. Since its inception, the Company has not generated any revenue from product sales and has never generated an operating profit. The Company has incurred significant losses on an aggregate basis. The Company’s net losses were $12,213 and $12,323 for the six months ended June 30, 2026 and 2025, respectively. As of June 30, 2026, the Company had an accumulated deficit of $413,484. These losses have resulted primarily from costs incurred in connection with research and development activities, licensing and patent investment and general and administrative costs associated with the Company’s operations. The Company expects to continue to incur operating losses for the foreseeable future. The Company expects to finance its operations primarily through utilization of its current financial resources and through the sale of additional equity or debt financings, collaborations, licensing arrangements or other sources. The Company could use its available capital resources sooner than it currently expects. The Company’s future viability is dependent on its ability to raise additional capital, enter into a financing, consummate a successful acquisition, merger, business combination, or a sale of assets or other transaction. If the Company becomes unable to continue as a going concern, it may have to liquidate its assets and the values it receives for its assets in liquidation or dissolution could be significantly lower than the values reflected in its consolidated financial statements.

Nature of the Business

6 Months Ended

Jun. 30, 2026

1. Nature of the Business

Rein Therapeutics, Inc. (“Company”) is a Delaware corporation formed in August 2001 under the name Renegade Therapeutics, Inc. In February 2007, the Company changed its name to Aileron Therapeutics, Inc. and in January 2025 changed its name to Rein Therapeutics, Inc. The Company is a clinical stage biopharmaceutical company focused on developing novel therapies for the treatment of fibrosis indications with no approved or limited effective treatments. The Company currently has one product candidate in clinical development, LTI-03.

The Company is a clinical-stage biotechnology company subject to significant risks and uncertainties, including the need for substantial additional financing, reliance on third parties, clinical trial risks, dependence on key personnel, protection of proprietary technology, and compliance with regulatory requirements. Its lead product candidate, LTI-03, is being developed for the treatment of idiopathic pulmonary fibrosis (IPF) and has completed Phase 1a and Phase 1b clinical trials; the Company is currently conducting the Phase 2 RENEW trial, a multi-center, randomized, double-blind, placebo-controlled study expected to enroll approximately 120 patients across multiple global sites, with interim data anticipated in the fourth quarter of 2026. The Company initiated patient screening in May 2025, received regulatory clearances in Europe and the United Kingdom, and dosed its first patient in March 2026. The Company’s second product candidate, LTI-01, previously in development for loculated pleural effusion, has been paused indefinitely as the Company prioritizes resources toward LTI-03, and the timing of any potential resumption remains uncertain and dependent on additional financing and the success of LTI-03.

Liquidity

In May 2026, the Company completed an underwritten public offering of 57,500,000 shares of its common stock at a public offering price of $1.00 per share, or the May 2026 Offering. Aggregate gross proceeds from the May 2026 Offering were $57,500, and net proceeds to the Company were approximately $53,099 after deducting underwriting discounts, commissions, and offering expenses of approximately $4,401.

Management believes that, based on the Company’s current operating plan, the Company’s cash, cash equivalents and investments of $43,627 as of June 30, 2026 will be sufficient to enable the Company to fund its planned operating expense and capital expenditure requirements into the first quarter of 2028. The Company believes that the funds are sufficient to enable the Company to complete the Phase 2 RENEW clinical trial of LTI-03. The Company’s estimate as to how long it expects its existing cash, cash equivalents and investments to be able to continue to fund its operations is based on assumptions that may prove to be wrong, and the Company could use its available capital resources sooner than it currently expects.

Since its inception, the Company has not generated any revenue from product sales and has never generated an operating profit. The Company has incurred significant losses on an aggregate basis. The Company’s net losses were $12,213 and $12,323 for the six months ended June 30, 2026 and 2025, respectively. As of June 30, 2026, the Company had an accumulated deficit of $413,484. These losses have resulted primarily from costs incurred in connection with research and development activities, licensing and patent investment and general and administrative costs associated with the Company’s operations. The Company expects to continue to incur operating losses for the foreseeable future. The Company expects to finance its operations primarily through utilization of its current financial resources and through the sale of additional equity or debt financings, collaborations, licensing arrangements or other sources.

The Company could use its available capital resources sooner than it currently expects. The Company’s future viability is dependent on its ability to raise additional capital, enter into a financing, consummate a successful acquisition, merger, business combination, or a sale of assets or other transaction. If the Company becomes unable to continue as a going concern, it may have to liquidate its assets and the values it receives for its assets in liquidation or dissolution could be significantly lower than the values reflected in its consolidated financial statements.