TRex Bio, Inc. (TRXB) IPO Dates & Offering Details

424B4 1 project_dino_-_424b4.htm 424B4 424B4 Table of Contents Filed pursuant to Rule 424(b)(4) Registration Statement No. 333-299018 Prospectus 8,333,334 Shares Common Stock This is TRex Bio, Inc.’s initial public offering. We are selling 8,333,334 shares of our common stock. The initial public offering price is $14.00 per share. Our common stock has been approved for listing on The Nasdaq Global Select Market (“Nasdaq”) under the symbol “TRXB.” We are an “emerging growth company” and a “smaller reporting company” as defined under the federal securities laws and, as such, have elected to comply with certain reduced reporting requirements in this prospectus and may elect to do so in future filings. Investing in our common stock involves a high degree of risk. See the section titled “ Risk Factors ” beginning on page 11 of this prospectus. Neither the 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. Per Share Total Initial public offering price $ 14.00 $ 116,666,676 Underwriting discounts and commissions (1) $ 0.98 $ 8,166,667 Proceeds, before expenses, to us $ 13.02 $ 108,500,009 (1) See the section titled “Underwriting” for additional information regarding underwriting compensation. The underwriters may also exercise their option to purchase up to an additional 1,250,000 shares from us, at the initial public offering price, less underwriting discounts and commissions, for 30 days after the date of this prospectus. The underwriters expect to deliver the shares of our common stock on or about October 13, 2026. Eli Lilly and Company (“Lilly”) has indicated an interest in purchasing at the initial public offering price shares of common stock in this offering in an amount, when combined with shares of common stock beneficially owned by Lilly prior to the initial public offering, that will not exceed 19.9% of the number of shares of common stock issued and outstanding after this offering. Because this indication of interest is not a binding agreement or commitment to purchase, Lilly may determine to purchase more, less or no shares in this offering or the underwriters may determine to sell more, less or no shares to Lilly. The underwriters will receive the same underwriting discounts and commissions on any of our shares of common stock purchased by Lilly as it will from any other shares of common stock sold to the public in this offering. The number of shares of common stock available for sale to the public will be reduced to the extent that Lilly purchases shares of common stock in the offering. J.P. Morgan Evercore ISI Cantor Stifel Wedbush PacGrow The date of this prospectus is October 8, 2026. Table of Contents