# EDGAR Filing Document

**Accession Number:** 0001420565
**File Stem:** 0001193125-25-183073
**Filing Date:** 2025-8
**Character Count:** 9919
**Document Hash:** 00a532b50a93c55e0933fddbbc817904
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-25-183073.hdr.sgml**: 20250819

**ACCESSION NUMBER**: 0001193125-25-183073

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 13

**CONFORMED PERIOD OF REPORT**: 20250819

**ITEM INFORMATION**: Other Events

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20250819

**DATE AS OF CHANGE**: 20250819

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Rein Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001420565
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 134196017
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-38130
- **FILM NUMBER:** 251229692

**BUSINESS ADDRESS:**
- **STREET 1:** 12407 N. MOPAC EXPY.
- **STREET 2:** SUITE 250 #390
- **CITY:** AUSTIN
- **STATE:** TX
- **ZIP:** 78758
- **BUSINESS PHONE:** 7378021989

**MAIL ADDRESS:**
- **STREET 1:** 12407 N. MOPAC EXPY.
- **STREET 2:** SUITE 250 #390
- **CITY:** AUSTIN
- **STATE:** TX
- **ZIP:** 78758

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Aileron Therapeutics, Inc.
- **DATE OF NAME CHANGE:** 20240329

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** AILERON THERAPEUTICS INC
- **DATE OF NAME CHANGE:** 20071207

?xml version='1.0' encoding='ASCII'? 8-K

### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### WASHINGTON, DC 20549

### FORM 8-K

#### CURRENT REPORT

#### Pursuant to Section 13 or 15(d)

#### of the Securities Exchange Act of 1934

#### Date of report (Date of earliest event reported): August 19, 2025

## REIN THERAPEUTICS, INC.

#### (Exact Name of Registrant as Specified in Its Charter)

---

| | | |
|:---|:---|:---|
| **Delaware** | **001-38130** | **13-4196017** |
| **(State or Other Jurisdiction<br>of Incorporation)** | **(Commission**<br> **File Number)** | **(I.R.S. Employer<br>Identification Number)** |

---

#### 12407 N. Mopac Expy., Suite 250, #390

#### Austin, Texas 78758

#### (Address of principal executive offices)
(737) 802-1989

#### (Registrant's telephone number, including area code)

#### N/A

#### (Former name or former address, if changed since last report)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligations of the registrant under any of the following provisions.

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14d-2(b)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)

#### Securities registered pursuant to Section 12(b) of the Act:

---

| | | |
|:---|:---|:---|
| **Title of each class** | **Trading<br>Symbol(s)** | **Name of each exchange<br>on which registered** |
| Common stock: Par value $.001 | RNTX | Nasdaq Capital Market |

---

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

------

#### Item 8.01 Other Events.
On August 19, 2025, Rein Therapeutics, Inc. issued a press release concerning the planned Phase 2 clinical trial of its LTI-03 product candidate in the U.K. A copy of the press release is attached as Exhibit 99.1 hereto.

#### Item 9.01 Financial Statements and Exhibits
(d) Exhibits

The following exhibits are filed with this report:

---

| | |
|:---|:---|
| Exhibit 99.1 | [The Company's press release dated August 19, 2025](d938122dex991.htm) |
| Exhibit 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) |

---

------

#### SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

---

| | | |
|:---|:---|:---|
|  | **REIN THERAPEUTICS, INC.** | **REIN THERAPEUTICS, INC.** |
| Dated: August 19, 2025 |  | */s/ Brian Windsor* |
|  |  | Brian Windsor, Ph.D., |
|  |  | President and Chief Executive Officer |

---

## Exhibit 99.1

**Exhibit 99.1** 

**Rein Therapeutics Wins U.K. Approval to Launch Phase 2 Clinical Trial of LTI-03 in Idiopathic Pulmonary Fibrosis** 

AUSTIN, Texas, Aug. 19, 2025 (GLOBE NEWSWIRE) — Rein Therapeutics ("Rein") (NASDAQ: RNTX), a biopharmaceutical company advancing a novel pipeline of first-in-class medicines to address significant unmet medical needs in orphan pulmonary and fibrosis indications, today announced that the UK Medicines and Healthcare products Regulatory Agency (MHRA) has authorized the Company to initiate its Phase 2 "*RENEW*" clinical trial of LTI-03, the Company's lead drug candidate for idiopathic pulmonary fibrosis (IPF).

IPF is a serious, progressive lung disease that affects hundreds of thousands of people worldwide. It scars the lungs, leaving patients short of breath and with limited treatment options. Median survival after diagnosis is just 3–5 years.

Rein's LTI-03 is a first-in-class therapy that is designed to directly target fibrosis while also protecting the lung's ability to regenerate healthy tissue. If successful, it could represent a major breakthrough in how pulmonary fibrosis is treated.

Brian Windsor, Chief Executive Officer of Rein Therapeutics, commented, "This MHRA approval marks an important milestone not only for Rein, but also for patients living with IPF. We are now working towards patient recruitment in the U.K., advancing LTI-03 into the next stage of development. Our approach is designed not only to slow disease progression, but also to preserve, and potentially restore, the lung cells that are critical to everyday breathing and quality of life. We believe LTI-03 has the potential to transform outcomes for patients while also creating substantial value for our shareholders."

**Next Steps** 

The *RENEW* trial is expected to enroll up to 120 patients worldwide, evaluating two dose groups of LTI-03 against a placebo. The primary objective of the trial is to assess safety and tolerability over 24 weeks of treatment. Secondary endpoints will include measures of lung function and imaging-based assessments of fibrosis progression.

Rein is actively working with clinical sites in the UK to begin patient recruitment soon, with initial data expected in 2026.

**About Rein Therapeutics** 

Rein Therapeutics is a clinical-stage biopharmaceutical company advancing a novel pipeline of first-in-class therapies to address significant unmet medical needs in orphan pulmonary and fibrosis indications. Rein's lead product candidate, LTI-03, is a novel, synthetic peptide with a dual mechanism targeting alveolar epithelial cell survival as well

------

as inhibition of profibrotic signaling. LTI-03 has received Orphan Drug Designation in the U.S. and is in clinical development. Rein's second product candidate, LTI-01, is a proenzyme that has completed Phase 1b and Phase 2a clinical trials for the treatment of loculated pleural effusions. LTI-01 has received Orphan Drug Designation in the U.S. and E.U. and Fast Track Designation in the U.S.

**Forward-Looking Statements** 

This press release may contain forward-looking statements of Rein Therapeutics, Inc. ("Rein", the "Company", "we", "our" or "us") within the meaning of the Private Securities Litigation Reform Act of 1995, including statements with respect to expectations for the Company's LTI-03 product candidate, the planned UK Phase 2 clinical trial of LTI-03 and the initial data readouts from the planned UK clinical trial. We use words such as "anticipate," "believe," "estimate," "expect," "hope," "intend," "may," "plan," "predict," "project," "target," "potential," "would," "can," "could," "should," "continue," and other words and terms of similar meaning to help identify forward-looking statements, although not all forward-looking statements contain these identifying words. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including (i) the risk that the Company may not be able to successfully undertake the planned UK Phase 2 clinical trial of LTI-03, (ii) success in early phases of pre-clinical and clinicals trials do not ensure later clinical trials will be successful; (iii) the risk that the Company may not be able to obtain additional working capital with which to initiate and complete planned UK clinical trial, (iv) the risk that the Company may not be able to announce initial data readouts from the planned UK clinical trial in 2026 or, if it is able to do so, that the data may not be favorable and (v) those other risks disclosed in the "Risk Factors" section of the Company's Annual Report on Form 10-K for the year ended December 31, 2024, which is on file with the United States Securities and Exchange Commission (the "SEC") and in subsequent filings that the Company files with the SEC. These forward-looking statements should not be relied upon as representing the Company's view as of any date after the date of this press release, and we expressly disclaim any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

**Rein Investor Relations & Media Contact:** 

Investor Relations

IR@ReinTx.com