Caribou Biosciences, Inc. 10-Q

Item 5. Other Information Rule 10b5-1 Trading Arrangements On February 25, 2026 , Tim Kelly , M.B.A., our chief technology officer , entered into a “Rule 10b5-1 trading arrangement” (as that term is defined in Regulation S-K, Item 408) that is intended to qualify as an “eligible sell-to-cover transaction” (as described in Rule 10b5-1(c)(1)(ii)(D)(3) under the Securities Exchange Act of 1934, as amended (“Exchange Act”)) and is intended to satisfy the affirmative defense in Rule 10b5-1(c) under the Exchange Act. This sell-to-cover arrangement applies to restricted stock units or performance-based stock units (collectively, “RSUs”), whether vesting is based on the passage of time and/or the achievement of performance goals, that were previously granted or that could in the future be granted by us from time to time (this type of arrangement, with the attributes described in this paragraph, is referred to as an “RSU Sell-to-Cover Instruction”). An RSU Sell-to-Cover Instruction provides for the automatic sale of shares of common stock that would otherwise be issuable on each settlement date of a covered RSU in an amount necessary to satisfy the applicable tax withholding obligations, with the proceeds of the sale delivered to us in satisfaction of the applicable tax withholding obligations. The number of shares of common stock that will be sold under an RSU Sell-to-Cover Instruction is not currently determinable as the number will vary based on the extent to which vesting conditions are satisfied, the market price of our common stock at the time of settlement, and the potential future grant of RSUs subject to a RSU Sell-to-Cover Instruction. An RSU Sell-to-Cover Instruction will remain in place indefinitely unless revoked in writing (including as to any particular sell-to-cover sale, as to which the officer may elect to pay the applicable withholding taxes in cash) in accordance with its terms. Except as described above, no other Section 16 officer or director adopted or terminated any Rule 10b5-1 trading arrangement or non-Rule 10b5-1 trading arrangement (as that term is defined in Regulation S-K, Item 408) during the quarter ended March 31, 2026. 27 Table of Contents Item 6. Exhibits. Exhibit Number Description 3.1 Amended and Restated Certificate of Incorporation of Caribou Biosciences, Inc. (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K (File No. 001-40631) filed by the Registrant with the SEC on July 28, 2021) 3.2 Amended and Restated Bylaws of Caribou Biosciences, Inc. (incorporated by reference to Exhibit 3.2 to the Current Report on Form 8-K (File No. 001-40631) filed by the Registrant with the SEC on July 28, 2021) 4.1 Description of Common Stock (incorporated by reference to Exhibit 4.1 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021 (File No. 001-40631), filed with the SEC on March 21, 2022) 31.1* Certification of Principal Executive Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Exchange Act, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. 31.2* Certification of Principal Financial Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Exchange Act, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. 32.1** Certification of Principal Executive Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. 32.2** Certification of Principal Financial Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. 101.INS* Inline XBRL Instance Document – the instance document does not appear in the Interactive Data File because XBRL tags are embedded within the Inline XBRL document. 101.SCH* Inline XBRL Taxonomy Extension Schema Document 101.CAL* Inline XBRL Taxonomy Extension Calculation Linkbase Document 101.DEF* Inline XBRL Taxonomy Extension Definition Linkbase Document 101.LAB* Inline XBRL Taxonomy Extension Label Linkbase Document 101.PRE* Inline XBRL Taxonomy Extension Presentation Linkbase Document 104* Cover Page Interactive Data File (embedded within the Inline XBRL document) ______________________________________________ * Filed herewith. ** Furnished herewith. 28 Table of Contents SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized. Caribou Biosciences, Inc. Date: May 7, 2026 By: /s/ Rachel E. Haurwitz Rachel E. Haurwitz, Ph.D. President and Chief Executive Officer (Principal Executive Officer) Date: May 7, 2026 By: /s/ Sriram Ryali Sriram Ryali, M.B.A. Chief Financial Officer (Principal Financial Officer and Principal Accounting Officer) 29