Sec Form 4 Filing - RINGO WILLIAM R @ Sensei Biotherapeutics, Inc. - 2022-03-08

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person RINGO WILLIAM R 2. Issuer Name and Ticker or Trading Symbol Sensei Biotherapeutics, Inc. [ SNSE] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O SENSEI BIOTHERAPEUTICS, INC., 1405 RESEARCH BLVD., SUITE 125 3. Date of Earliest Transaction (MM/DD/YY) 03/08/2022 (Street) ROCKVILLE, MD20850 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 03/08/2022 A 8,933( 1 ) A $ 0 8,933 D Common Stock 03/08/2022 A 10,000( 2 ) A $ 0 18,933( 3 ) D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Option (Right to Buy) $ 3.08 03/08/2022 A 29,100 ( 4 ) 03/07/2032 Common Stock 29,100 $ 0 29,100 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other RINGO WILLIAM R C/O SENSEI BIOTHERAPEUTICS, INC. 1405 RESEARCH BLVD., SUITE 125 ROCKVILLE, MD20850 X Signatures /s/ Mark Ballantyne, Attorney-in-Fact 03/09/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These shares represent restricted stock units (the "RSUs"). Each RSU represents a contingent right to receive one share of the common stock of the Issuer. The shares underlying the RSUs vest in three equal annual installments on each of March 8, 2023, March 8, 2024, and March 8, 2025, subject to the Reporting Person's continuous service with the Issuer as of each such vesting date. ( 2 )These shares represent RSUs. Each RSU represents a contingent right to receive one share of the common stock of the Issuer. The shares underlying the RSUs vest in full on the first anniversary of the date of grant, on March 8, 2023, subject to the Reporting Person's continuous service with the Issuer as of each such vesting date. ( 3 )Includes 8,933 shares acquired by the Reporting Person as of March 8, 2022 as an RSU award. ( 4 )The shares subject to the option vest monthly over thirty-six (36) months from the vesting commencement date, March 8, 2022, subject to the Reporting Person's continuous service with the Issuer as of each such vesting date.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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