Rein Therapeutics, Inc.

S-11 d83075ds1.htm S-1

As filed with the Securities and Exchange Commission on April 28, 2026

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

**FORMS-1 **

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

(Exact name of registrant as specified in its charter)

12407 N. Mopac Expy., Suite 250 #390

Austin, Texas 78758

**(737)802-1989 **

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Brian Windsor, Ph.D.

President and Chief Executive Officer

12407 N. Mopac Expy., Suite 250 #390

Austin, Texas 78758

**(737) 802-1989 **

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after this Registration Statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, anon-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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 7(a)(2)(B) of the Securities Act. ☐

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until this registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

30,000,000 Shares of Common Stock

We are selling 30,000,000 shares of our common stock at an assumed public offering price of $1.66 per share, the last reported sale price of our common stock as reported on The Nasdaq Capital Market on April 24, 2026. The actual public offering price per share of common stock will be determined between us and the underwriters at the time of pricing and may be at a discount to this assumed offering price. Therefore, the assumed public offering price used throughout this prospectus may not be indicative of the final offering price.

Our common stock is listed on the Nasdaq Capital Market under the symbol “RNTX.” On April 24, 2026, the last reported sale price of our common stock on the Nasdaq Capital Market was $1.66 per share.

Investing in our securities involves a high degree of risk. Before making an investment decision, you should carefully review and consider all of the information set forth in this prospectus and the documents incorporated by reference herein, including the risks and uncertainties described under “Risk Factors” beginning on page 5 of this prospectus and the risk factors incorporated by reference into this prospectus.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

We have granted the underwriters a 45-day option to purchase up to an additional 4,500,000 shares of common stock from us at the public offering price, less underwriting discounts and commissions. If the underwriters exercise this option in full, the total underwriting discounts and commissions payable will be $ and the total proceeds to us, before expenses, will be $ .

The underwriters expect to deliver the shares on or about , 2026.

Konik Capital Partners

**a division of T.R. Winston & Co **

The date of this prospectus is , 2026.