Sec Form 4 Filing - Ruddy Marcella K. @ Tectonic Therapeutic, Inc. - 2024-06-20

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 Ruddy Marcella K. 2. Issuer Name and Ticker or Trading Symbol Tectonic Therapeutic, Inc. [ TECX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Medical Officer (Last) (First) (Middle) C/O TECTONIC THERAPEUTIC, INC., 490 ARSENAL WAY, SUITE 210 3. Date of Earliest Transaction (MM/DD/YY) 06/20/2024 (Street) WATERTOWN, MA02472 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 06/20/2024 A 32,065 A 32,065 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 Employee Stock Option (Right to Buy) $ 2.38 ( 2 ) 06/20/2024 A 43,946 ( 2 ) ( 3 ) 09/16/2031 Common Stock 43,946 ( 2 ) ( 2 ) ( 4 ) 43,946 D Employee Stock Option (Right to Buy) $ 5.38 ( 2 ) 06/20/2024 A 18,704 ( 2 ) ( 5 ) 11/30/2033 Common Stock 18,704 ( 2 ) ( 2 ) ( 6 ) 18,704 D Employee Stock Option (Right to Buy) $ 16.8 06/20/2024 A 81,700 ( 7 ) 06/19/2034 Common Stock 81,700 $ 0 81,700 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Ruddy Marcella K. C/O TECTONIC THERAPEUTIC, INC. 490 ARSENAL WAY, SUITE 210 WATERTOWN, MA02472 Chief Medical Officer Signatures /s/ Daniel Lochner, Attorney-in-Fact 06/24/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Received in exchange for 60,000 shares of common stock of Tectonic Therapeutic, Inc., a Delaware corporation ("Tectonic"), pursuant to an Agreement and Plan of Merger dated as of January 30, 2024 (the "Merger Agreement") by and among AVROBIO, Inc., a Delaware corporation ("AVROBIO"), Tectonic and Alpine Merger Subsidiary, Inc., a direct, wholly owned subsidiary of AVROBIO (the "Merger Sub"). Under the terms of the Merger Agreement, on June 20, 2024, Merger Sub merged with and into Tectonic (the "Merger"), with Tectonic surviving the Merger as a wholly owned subsidiary of AVROBIO. Upon the closing of the Merger, each share of Tectonic common stock was converted into the right to receive 0.534419990 shares of the Issuer's common stock, after giving effect to a reverse stock split of the Issuer's common stock of 1-for-12. Subsequent to the Merger, the name of the Issuer was changed from AVROBIO, Inc. to Tectonic Therapeutic, Inc. ( 2 )Upon the closing of the Merger, each outstanding option to purchase shares of Tectonic common stock was assumed by the Issuer and converted into an option to purchase the Issuer's common stock, on the same terms and conditions as were applicable to such Tectonic stock option prior to the Merger, as adjusted for the exchange ratio and the reverse stock split. ( 3 )23,360 of the shares subject to the option are immediately exercisable and the remainder vest in 13 equal monthly installments beginning on July 19, 2024, subject to the Reporting Person's continued service to the Issuer on each such vesting date. ( 4 )Received in exchange for a stock option to acquire 82,233 shares of Tectonic common stock pursuant to the Merger Agreement. ( 5 )The shares subject to the option vest in 48 equal monthly installments beginning on December 1, 2023, subject to the Reporting Person's continued service to the Issuer on each such vesting date ( 6 )Received in exchange for a stock option to acquire 35,000 shares of Tectonic common stock pursuant to the Merger Agreement. ( 7 )The shares subject to the option vest as to 25% of the shares on June 20, 2025 with the remainder vesting in the following 36 equal monthly installments, subject to the Reporting Person's continued service on each such vesting date

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

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