Sec Form 3 Filing - McCauley Thomas @ Omega Therapeutics, Inc. - 2021-07-29

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 McCauley Thomas 2. Issuer Name and Ticker or Trading Symbol Omega Therapeutics, Inc. [ OMGA] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Scientific Officer (Last) (First) (Middle) C/O OMEGA THERAPEUTICS, INC., 20 ACORN PARK DRIVE 3. Date of Earliest Transaction (MM/DD/YY) 07/29/2021 (Street) CAMBRIDGE, MA02140 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 21,176 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) $ 0.6 ( 1 ) 09/16/2029 Common Stock 273,720 D Stock Option (Right to Buy) $ 5.67 ( 2 ) 03/28/2031 Common Stock 186,617 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other McCauley Thomas C/O OMEGA THERAPEUTICS, INC. 20 ACORN PARK DRIVE CAMBRIDGE, MA02140 Chief Scientific Officer Signatures /s/ Barbara Chan as Attorney-in-fact for Thomas McCauley, Ph.D. 07/29/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The options vest and become exercisable with respect to 25% of the underlying shares on July 29, 2020 and in equal quarterly installments thereafter such that the option will become fully vested and exercisable on July 29, 2023, subject to the Reporting Person's continued service to the Issuer through each vesting date. ( 2 )The options vest and become exercisable with respect to 25% of the underlying shares on March 26, 2022 and in equal quarterly installments thereafter such that the option will become fully vested and exercisable on March 26, 2025, subject to the Reporting Person's continued service to the Issuer through each vesting date.

Remarks: 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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