SAB Biotherapeutics, Inc.

Item 1.01 Entry into a Material Definitive Agreement. On March 17, 2026, SAB Biotherapeutics, Inc. (the “Company” or “SAB”) entered into an underwriting agreement (the “Underwriting Agreement”) with Jefferies LLC, UBS Securities LLC, Citigroup Capital Markets, Inc. and Barclays Capital Inc. (collectively, the “Representatives”) as the representatives of the several underwriters named therein (the “Underwriters”), relating to an underwritten offering (the “Offering”) of (i) 19,324,677 shares (the “Firm Shares”) of the Company’s common stock, $0.0001 par value per share (the “Common Stock”), at a price to the public of $3.85 per Firm Share, and (ii) pre-funded warrants to purchase up to 2,753,246 shares of Common Stock (the “Pre-Funded Warrants”), and such shares issuable upon the exercise of the Pre-Funded Warrants (the “Warrant Shares”), at a price to the public of $3.8499 per Pre-Funded Warrant, which represents the per share public offering price for the Firm Shares less the $0.0001 per share exercise price for each such Pre-Funded Warrant. The Company also granted the Underwriters a 30-day option to purchase up to an additional 3,311,688 shares of Common Stock (the “Optional Shares”, and together with the Firm Shares, the “Shares”) at the public offering price, less underwriting discounts and commissions. All of the Shares and Pre-Funded Warrants in the Offering are being sold by the Company. The offering is expected to close on March 19, 2026, subject to customary closing conditions. The Company estimates that the net proceeds from the Offering will be approximately $69.7 million (or $81.7 million if the Underwriters exercise their option to purchase the Optional Shares), after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company, assuming no exercise of the Pre-Funded Warrants. The Shares will be issued pursuant to a shelf registration statement on Form S-3 (File No. 333-292482), as filed with the U.S. Securities and Exchange Commission (“SEC”) on December 29, 2025, which became effective on January 7, 2026, and a prospectus supplement, dated March 17, 2026, filed with the SEC on March 19, 2026. The Underwriting Agreement contains customary representations, warranties, covenants, indemnification obligations of the Company and the Underwriters, including for liabilities under the Securities Act of 1933, as amended, and other obligations of the parties. The representations, warranties and covenants contained in the Underwriting Agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed upon by the contracting parties. The foregoing is only a brief description of the terms of the Underwriting Agreement and the Pre-Funded Warrants, does not purport to be a complete statement of the rights and obligations of the parties under the Underwriting Agreement or the Pre-Funded Warrants, as applicable, and the transactions contemplated thereby, and is qualified in its entirety by reference to the Underwriting Agreement and the form of Pre-Funded Warrant, which are filed as Exhibit 1.1 and Exhibit 4.1, respectively, to this Current Report on Form 8-K and each is incorporated herein by reference. A copy of the legal opinion of Dentons US LLP relating to the issuance and sale, as applicable, of the Shares, the Pre-Funded Warrants and the Warrant Shares is filed as Exhibit 5.1 to this Current Report on Form 8-K and is filed with reference to, and is hereby incorporated by reference into, the Registration Statement.

Item 8.01 Other Events. Press Releases in Connection with the Offering The full text of each of the press releases announcing the launch and pricing of the Offering are attached as Exhibit 99.1 and Exhibit 99.2 hereto, respectively, and are incorporated herein by reference.