Sec Form 4 Filing - Vitorovic Stefan @ 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 Vitorovic Stefan 2. Issuer Name and Ticker or Trading Symbol Tectonic Therapeutic, Inc. [ TECX] 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 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 1,000,900 A 1,000,900 I By LLC ( 2 ) Common Stock 06/20/2024 A 27,774 A 27,774 I By LLC ( 4 )

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) $ 16.8 06/20/2024 A 11,760 ( 5 ) 06/19/2034 Common Stock 11,760 $ 0 11,760 D

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

Explanation of Responses:

( 1 )Received in exchange for 1,872,873 shares of common stock held by Vida Ventures II, LLC ("VIDA II") 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 )The Reporting Person, through his position as a member of the investment committee of VV Manager II, LLC ("VV Manager"), the manager of VIDA II, may be deemed to have voting and dispositive power over the shares held by VIDA II. The Reporting Person disclaims beneficial ownership of the shares held by VIDA II, except to the extent of his pecuniary interest therein and this report shall not be deemed an admission that the Reporting Person is the beneficial owner of these securities for purposes of Section 16 or for any other purpose. ( 3 )Received in exchange for 51,969 shares of common stock held by Vida Ventures II-A, LLC ("VIDA II-A") of Tectonic pursuant to the same terms and conditions as described in footnote (1) herein. ( 4 )The Reporting Person, through his position as a member of the investment committee of VV Manager, the manager of VIDA II-A, may be deemed to have voting and dispositive power over the shares held by VIDA II-A. The Reporting Person disclaims beneficial ownership of the shares held by VIDA II-A, except to the extent of his pecuniary interest therein and this report shall not be deemed an admission that the Reporting Person is the beneficial owner of these securities for purposes of Section 16 or for any other purpose. ( 5 )1/3rd of the shares subject to the option will vest on June 20, 2025, and the balance will vest in equal monthly installments thereafter over the next 24 months, subject in each case to the continuous service of the Reporting Person to the Issuer through the applicable 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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