Business Description

1. Nature of the Business On January 10, 2025, Aileron Therapeutics, Inc., or Aileron, amended its Restated Certificate of Incorporation, as amended, to effect a change of the Company’s name from “Aileron Therapeutics, Inc.” to “Rein Therapeutics, Inc.”, or Rein, or the Company. Prior to the Lung Acquisition (as defined below), the Company was a clinical stage chemoprotection oncology company. The Company’s product candidate, ALRN-6924, was a MDM2/MDMX dual inhibitor that leverages its proprietary peptide drug technology. In February 2023, the Company decided to terminate further development of ALRN-6924. On October 31, 2024, the Company entered into an exclusive option agreement with Advancium Health Network, or Advancium, for the sale of ALRN-6924. In July 2025, the option agreement was terminated. In August 2025, the Company entered into a letter agreement with Rients LLC, or Rients, for Rients to evaluate the legacy ALRN-6924 compound, or the Compound Asset. During the term of the letter agreement, Rients shall pay the Company for all fees and expenses incurred by the Company to maintain the Compound Asset. 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. Development of another product candidate, LTI-01, as well as multiple candidates in preclinical development focused on fibrosis indications were postponed for an indefinite period due to insufficient financing as disclosed below. On October 31, 2023, the Company acquired Lung Therapeutics, Inc., or Lung Therapeutics or Lung, pursuant to an Agreement and Plan of Merger, dated October 31, 2023, or the Lung Acquisition Agreement, by and among the Company, AT Merger Sub I, Inc., a Delaware corporation and its wholly owned subsidiary, or the First Merger Sub, AT Merger Sub II, LLC, a Delaware limited liability company and its wholly owned subsidiary, or the Second Merger Sub, and Lung. Its principal offices are in Austin, Texas. Following the Lung Acquisition, the Company shifted its operating disease focus to advancing a pipeline of first-in-class medicines to address significant unmet medical needs in orphan pulmonary and fibrosis indications with the potential to greatly improve patient outcomes over currently available treatments. Following expiration of the lease on March 31, 2024, Rein currently operates and expects to operate virtually for the foreseeable future. The Company is subject to risks and uncertainties common to clinical-stage companies in the biotechnology industry, including, but not limited to the risk that the Company never achieves profitability, the need for substantial additional financing, the risk of relying on third parties, risks of clinical trial failures, dependence on key personnel, protection of proprietary technology, and compliance with government regulations. The Company’s lead product candidate, LTI-03, is being developed for the treatment of Idiopathic Pulmonary Fibrosis, or IPF, and has been evaluated in a healthy volunteer Phase 1a clinical trial and in a Phase 1b clinical trial in IPF patients. A Phase 2 multi-center, randomized, double-blind, and placebo-controlled study evaluating the safety, tolerability, and efficacy of LTI-03 in patients with IPF will enroll up to 120 IPF patients with interim topline data expected in the second half of 2026. The Company’s second product candidate, LTI-01, was in development for loculated pleural effusion, or LPE. The Company has completed Phase 1b and Phase 2a clinical trials in LPE patients. In June 2024, the Company decided to temporarily delay clinical development of LTI-01 in an effort to focus its resources on clinical development of LTI-03 and until additional funds are raised. In the fourth quarter of 2024, the Company determined that the temporary delay of further clinical development of LTI-01 may not be a short-term measure. In the fourth quarter of 2025, the Company decided to pause development activities related to LTI-01 for an indefinite period. The timing and likelihood of resuming development are uncertain and contingent on the Compamy’s ability to obtain additional financing and the future success of LTI-03. In May 2025, the Company initiated screening and recruitment of patients in the RENEW Phase 2 clinical trial of LTI-03.…