Sec Form 4 Filing - Gaiero David G @ Cyteir Therapeutics, Inc. - 2021-12-20

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 Gaiero David G 2. Issuer Name and Ticker or Trading Symbol Cyteir Therapeutics, Inc. [ CYT] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Financial Officer (Last) (First) (Middle) C/O CYTEIR THERAPEUTICS, INC., 128 SPRING ST, BUILDING A, SUITE 510 3. Date of Earliest Transaction (MM/DD/YY) 12/20/2021 (Street) LEXINGTON, MA02421 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 12/20/2021 M 4,100 A $ 1.68 ( 1 ) 4,100 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) $ 1.68 ( 1 ) 12/20/2021 M 4,100 ( 2 ) 12/10/2030 Common Stock 4,100 $ 0 73,639 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Gaiero David G C/O CYTEIR THERAPEUTICS, INC. 128 SPRING ST, BUILDING A, SUITE 510 LEXINGTON, MA02421 Chief Financial Officer Signatures /s/ Adam M. Veness, as attorney-in-fact for David Gaiero 02/07/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Due to rounding in connection with the Issuer's reverse stock split during its initial public offering, the exercise price for this option was immaterially incorrect as reported on the Reporting Person's Form 3 filing on June 17, 2021, and has been corrected in this Form 4. ( 2 )The option vested as to 25% of the underlying shares of common stock on December 7, 2021, the first anniversary of the vesting commencement date, and vests 1/48th of the underlying shares thereafter on each subsequent monthly anniversary of the vesting commencement date until the option is fully vested, subject to the Reporting Person's continued employment with the Issuer through the applicable vesting date.

Remarks: Exhibit List: Exhibit 24 - Power of Attorney

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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