Proxy Results, Amendments to Bylaws, Management Change/Compensation (Form 8-K)

On June 10, 2026, Sensei Biotherapeutics, Inc. (the "Company") held its 2026 annual meeting of stockholders (the "Annual Meeting"). At the Annual Meeting, the Company's stockholders approved (i) the Company's 2026 Equity Incentive Plan (the "2026 Plan") and (ii) the Company's 2026 Employee Stock Purchase Plan (the "2026 ESPP").

The 2026 Plan has an initial share reserve equal to (i) 2,671,981 shares of the Company's common stock, par value $0.0001 per share ("common stock") plus up to (ii) 311,164 shares of common stock subject to outstanding stock awards granted under the Company's 2021 Equity Incentive Plan that, after the date the 2026 Plan becomes effective, are not issued because a stock award expires or otherwise terminates without all of the shares covered by the award having been issued; are not issued because the stock award is settled in cash; are forfeited or repurchased because of the failure to vest; or are reacquired or withheld to satisfy a tax withholding obligation or the purchase or exercise price. In addition, the number of shares of common stock reserved for issuance under the 2026 Plan will automatically increase on January 1 of each calendar year, from January 1, 2027 through January 1, 2036, in an amount equal to 5% of the total number of shares of all classes of common stock outstanding plus all shares of common stock issuable upon the exercise of any pre-funded warrants (without regard to any beneficial ownership limitations) on December 31 of the preceding year, or a lesser number of shares determined by the Company's board of directors (the "Board").

The 2026 ESPP has an initial share reserve equal to 267,198 shares of common stock. In addition, the number of shares of common stock reserved for issuance under the 2026 ESPP will automatically increase on January 1 of each calendar year, beginning on January 1, 2027 through January 1, 2036, by the lesser of (i) 1% of the total number of shares of all classes of common stock outstanding plus all shares of common stock issuable upon the exercise of any pre-funded warrants (without regard to any beneficial ownership limitations), on December 31 of the preceding calendar year, and (ii) a number of shares equal to two times the initial share reserve; provided that before the date of any such increase, the Board may determine that such increase will be less than the amount set forth in clauses (i) and (ii).

The Board previously approved the 2026 Plan and 2026 ESPP on April 10, 2026, and approved the grant of an option award, in each case, subject to stockholder approval.

A summary of the principal features of the 2026 Plan and 2026 ESPP are set forth under the headings "Proposal No. 5-Approval of the 2026 Equity Incentive Plan" and "Proposal No. 6-Approval of the 2026 ESPP" contained in the Company's definitive proxy statement on Schedule 14A, filed with the Securities and Exchange Commission on April 27, 2026 (the "Proxy Statement"). The summaries are qualified in their entirety by reference to the 2026 Plan, forms of option grant notices and option agreements and forms of restricted stock unit grant notice and unit award agreement thereunder, and the 2026 ESPP, which are attached as Exhibits 10.1 and 10.2, respectively, to this Current Report on Form 8-K and incorporated herein by reference.

At the Annual Meeting, the Company's stockholders approved an amendment to the Company's Amended and Restated Certificate of Incorporation (the "Amendment") to increase the authorized number of shares of common stock from 12,500,000 to 300,000,000. The Amendment was filed with the Secretary of State of the State of Delaware on June 10, 2026 and effective as of such date.

The foregoing description is qualified in its entirety by the Amendment, which is attached as Exhibit 3.1 to this Current Report on Form 8-K and incorporated herein by reference.

At the Annual Meeting, the stockholders voted on six proposals, each of which is described in more detail in the Proxy Statement. Of the 1,341,140 shares outstanding as of the record date, 1,077,174 shares, or 80.32%, were present or represented by proxy at the Annual Meeting. Set forth below are the results of the matters submitted for a vote of stockholders at the Annual Meeting.

Proposal No. 1: Election of two nominees to serve as directors on the Board of Directors until the 2029 annual meeting of stockholders and until their respective successors are elected and qualified. The votes were cast as follows:

Broker Non-Votes: 311,652

All nominees were elected.

Proposal No. 2: Ratification of the appointment of Deloitte & Touche LLP as independent registered public accounting firm for the fiscal year ending December 31, 2026. The votes were cast as follows:

Proposal No. 2 was approved.

Proposal No. 3: Approval of the issuance of shares of the Company's common stock upon conversion of the Company's Series B Non-Voting Convertible Preferred Stock, which will (a) represent more than 20% of the shares of common stock outstanding and (b) result in the change of control of the Company pursuant to Nasdaq Listing Rules 5635(a) and 5635(b), respectively . The votes were cast as follows:

Broker Non-Votes: 311,652

Proposal No. 3 was approved.

Proposal No. 4: Approval of an amendment to the Company's Amended and Restated Certificate of Incorporation, as amended to date, to increase the number of authorized shares of our common stock from 12,500,000 to 300,000,000. The votes were cast as follows:

Broker Non-Votes: -

Proposal No. 4 was approved.

Proposal No. 5: Approval of the 2026 Plan. The votes were cast as follows:

Broker Non-Votes: 311,652

Proposal No. 5 was approved.

Proposal No. 6: Approval of the 2026 ESPP. The votes were cast as follows:

Broker Non-Votes: 311,652

Proposal No. 6 was approved.

Proposal No. 7: Approval of the adjournment or postponement of the Annual Meeting, if necessary, to continue to solicit votes for Proposals Nos. 3, 4, 5 and/or 6 or if the Nasdaq initial listing application required by Nasdaq Listing Rule 5110(a) has not yet been approved.

As there were sufficient votes to approve Proposals Nos. 3, 4, 5 and 6 at the time of the Annual Meeting, Proposal No. 7 was not presented to stockholders.