Organization	9 Months Ended
Sep. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Note 1. Organization Description of Business TRex Bio, Inc. (the “Company”) is a clinical-stage biotechnology company focused on studying the regulation of tissue inflammation to develop breakthrough medicines. The Company has created a multi-faceted discovery platform to gain insights into regulatory T cell biology through transcriptomic analyses. The Company has translated these findings into drug discovery campaigns, including a collaboration with Eli Lilly and Company (“Lilly”). In June 2025, the Company announced that it had initiated dosing in its first clinical trial for TRB-061, a novel TNFR2 agonist initially being developed for the treatment of atopic dermatitis. Reverse Stock Split On October 2, 2026, the Company effected a 1-for-3.8649 reverse stock split of its issued and outstanding shares of common stock. Upon the effectiveness of the reverse stock split: (i) the number of shares of outstanding common stock was adjusted; (ii) the conversion ratio of the convertible preferred stock was proportionately adjusted; (iii) the number of shares of common stock underlying each outstanding stock option was adjusted; and (iv) the exercise price of each outstanding stock option was proportionately adjusted. All outstanding common stock (including shares of common stock subject to outstanding options and the common shares issuable upon conversion of the outstanding convertible preferred stock), share prices, exercise prices, and per-share amounts contained in the condensed financial statements have been retroactively adjusted to reflect this reverse stock split for all periods presented. The reverse stock split did not impact the number of outstanding shares of convertible preferred stock, the authorized number of shares of common and preferred stock, or the par value per share. Initial Public Offering In October 2026, the Company completed its initial public offering (“IPO”), issuing and selling an aggregate of 9,539,237 shares of its common stock at the IPO price of $14.00 per share, including 1,205,903 shares sold pursuant to the underwriters’ partial exercise of their option to purchase additional shares. The IPO resulted in net proceeds of approximately $119.0 million, after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company. Immediately prior to the closing of the IPO, the Company’s outstanding redeemable convertible preferred stock automatically converted into 17,742,217 shares of common stock. Following the closing of the IPO, no shares of redeemable convertible preferred stock were authorized or outstanding. In connection with the completion of the IPO, the Company’s certificate of incorporation was amended and restated to (i) authorize 225.0 million shares of common stock, par value $0.0001 per share, (ii) eliminate all references to the previously existing series of redeemable convertible preferred stock and (iii) authorize 25.0 million shares of undesignated preferred stock, par value $0.0001 per share, that may be issued from time to time by the Company’s board of directors in one or more series. The Company’s unaudited condensed financial statements as of September 30, 2026, including share and per-share amounts, do not give effect to the IPO and related actions, as the IPO closed subsequent to September 30, 2026. Liquidity and Capital Resources The accompanying unaudited condensed financial statements have been prepared on a going concern basis, which contemplates that the Company will realize its assets and satisfy its liabilities in the normal course of business. The Company is subject to risks inherent in operating a clinical-stage biotechnology business, including dependence on successful product development, the ability to attract and retain qualified personnel, rapid technological change and the evolving nature of the biotechnology industry. As of September 30, 2026, the Company had cash, cash equivalents and marketable securities of $78.2 million and an accumulated deficit of $136.8 million. The Company has incurred net losses and negative cash flows from operations since inception, except for the year ended December 31, 2023, during which it commenced the Research Collaboration and License Agreement with Lilly (as amended, the “Lilly Collaboration Agreement”), received a one-time upfront payment of $55.0 million and recognized total collaboration revenue of $41.9 million across its collaboration agreements. The Company believes its existing cash, cash equivalents and marketable securities as of September 30, 2026, together with the net proceeds received from the IPO, will be sufficient to fund its operations for at least twelve months from the date these unaudited condensed financial statements are issued. This estimate is based on assumptions that may prove incorrect, and the Company could use its available capital resources sooner than currently expected. The Company expects to continue to incur substantial losses for the foreseeable future. Unless and until it generates sufficient revenue, it will need additional capital to fund research and development and maintain operations. If capital is unavailable when needed on acceptable terms, the Company could be required to delay, reduce or discontinue one or more development programs or other operations.

Organization

9 Months Ended

Sep. 30, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Note 1. Organization

Description of Business

TRex Bio, Inc. (the “Company”) is a clinical-stage biotechnology company focused on studying the regulation of tissue inflammation to develop breakthrough medicines. The Company has created a multi-faceted discovery platform to gain insights into regulatory T cell biology through transcriptomic analyses. The Company has translated these findings into drug discovery campaigns, including a collaboration with Eli Lilly and Company (“Lilly”). In June 2025, the Company announced that it had initiated dosing in its first clinical trial for TRB-061, a novel TNFR2 agonist initially being developed for the treatment of atopic dermatitis.

Reverse Stock Split

On October 2, 2026, the Company effected a 1-for-3.8649 reverse stock split of its issued and outstanding shares of common stock. Upon the effectiveness of the reverse stock split: (i) the number of shares of outstanding common stock was adjusted; (ii) the conversion ratio of the convertible preferred stock was proportionately adjusted; (iii) the number of shares of common stock underlying each outstanding stock option was adjusted; and (iv) the exercise price of each outstanding stock option was proportionately adjusted. All outstanding common stock (including shares of common stock subject to outstanding options and the common shares issuable upon conversion of the outstanding convertible preferred stock), share prices, exercise prices, and per-share amounts contained in the condensed financial statements have been retroactively adjusted to reflect this reverse stock split for all periods presented. The reverse stock split did not impact the number of outstanding shares of convertible preferred stock, the authorized number of shares of common and preferred stock, or the par value per share.

Initial Public Offering

In October 2026, the Company completed its initial public offering (“IPO”), issuing and selling an aggregate of 9,539,237 shares of its common stock at the IPO price of $14.00 per share, including 1,205,903 shares sold pursuant to the underwriters’ partial exercise of their option to purchase additional shares. The IPO resulted in net proceeds of approximately $119.0 million, after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company. Immediately prior to the closing of the IPO, the Company’s outstanding redeemable convertible preferred stock automatically converted into 17,742,217 shares of common stock. Following the closing of the IPO, no shares of redeemable convertible preferred stock were authorized or outstanding.

In connection with the completion of the IPO, the Company’s certificate of incorporation was amended and restated to (i) authorize 225.0 million shares of common stock, par value $0.0001 per share, (ii) eliminate all references to the previously existing series of redeemable convertible preferred stock and (iii) authorize 25.0 million shares of undesignated preferred stock, par value $0.0001 per share, that may be issued from time to time by the Company’s board of directors in one or more series.

The Company’s unaudited condensed financial statements as of September 30, 2026, including share and per-share amounts, do not give effect to the IPO and related actions, as the IPO closed subsequent to September 30, 2026.

Liquidity and Capital Resources

The accompanying unaudited condensed financial statements have been prepared on a going concern basis, which contemplates that the Company will realize its assets and satisfy its liabilities in the normal course of business. The Company is subject to risks inherent in operating a clinical-stage biotechnology business, including dependence on successful product development, the ability to attract and retain qualified personnel, rapid technological change and the evolving nature of the biotechnology industry.

As of September 30, 2026, the Company had cash, cash equivalents and marketable securities of $78.2 million and an accumulated deficit of $136.8 million. The Company has incurred net losses and negative cash flows from operations since inception, except for the year ended December 31, 2023, during which it commenced the Research Collaboration and License Agreement with Lilly (as amended, the “Lilly Collaboration Agreement”), received a one-time upfront payment of $55.0 million and recognized total collaboration revenue of $41.9 million across its collaboration agreements.

The Company believes its existing cash, cash equivalents and marketable securities as of September 30, 2026, together with the net proceeds received from the IPO, will be sufficient to fund its operations for at least twelve months from the date these unaudited condensed financial statements are issued. This estimate is based on assumptions that may prove incorrect, and the Company could use its available capital resources sooner than currently expected.

The Company expects to continue to incur substantial losses for the foreseeable future. Unless and until it generates sufficient revenue, it will need additional capital to fund research and development and maintain operations. If capital is unavailable when needed on acceptable terms, the Company could be required to delay, reduce or discontinue one or more development programs or other operations.