Sec Form 3 Filing - George Jean @ Cyteir Therapeutics, Inc. - 2021-06-17

FORM 3 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 George Jean 2. Issuer Name and Ticker or Trading Symbol Cyteir Therapeutics, Inc. [ CYT] 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) 128 SPRING ST, BUILDING A, SUITE 510 3. Date of Earliest Transaction (MM/DD/YY) 06/17/2021 (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

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 Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 2,200,184 I See Footnote ( 3 ) Series C Convertible Preferred Stock ( 2 ) ( 2 ) ( 2 ) Common Stock 244,081 I See Footnote ( 3 ) Stock Option (Right to Buy) $ 18 ( 4 ) 06/17/2031 Common Stock 17,250 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other George Jean 128 SPRING ST, BUILDING A, SUITE 510 LEXINGTON, MA02421 X Signatures By: /s/ Andrew Gengos, Attorney-in-Fact 06/17/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares of Series B Convertible Preferred Stock are convertible into the number of shares of the Issuer's common stock shown in column 3 and have no expiration date. The Series B Convertible Preferred Stock will automatically convert into common stock upon the closing of the Issuer's initial public offering. ( 2 )The shares of Series C Convertible Preferred Stock are convertible into the number of shares of the Issuer's common stock shown in column 3 and have no expiration date. The Series C Convertible Preferred Stock will automatically convert into common stock upon the closing of the Issuer's initial public offering. ( 3 )Shares held by Lightstone Ventures II, L.P. and Lightstone Ventures II (A), L.P. LSV Associates II, LLC is the general partner of Lightstone Ventures II, L.P. and Lightstone Ventures II (A), L.P. The Reporting Person, is a managing director of LSV Associates II, LLC. The reporting person disclaims beneficial ownership of the securities reported herein, except to the extent of her pecuniary interest therein. ( 4 )The option will vest in full on the earlier of (a) June 17, 2022 and (b) the next annual meeting of stockholders that follows June 17, 2021, in each case subject to the Reporting Person's continued service on the Issuer's board of directors 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).

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