Sec Form 4 Filing - REICIN ALISE @ 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 REICIN ALISE 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 X __ Officer (give title below) _____ Other (specify below) Chief Executive 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 166,580 ( 1 ) A 166,580 ( 1 ) D Common Stock 06/20/2024 A 124,530 A 124,530 I By Trust ( 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 Employee Stock Option (Right to Buy) $ 2.38 ( 5 ) 06/20/2024 A 33,923 ( 5 ) ( 6 ) 06/27/2031 Common Stock 33,923 ( 5 ) ( 5 ) ( 7 ) 33,923 D Employee Stock Option (Right to Buy) $ 5.38 ( 5 ) 06/20/2024 A 23,380 ( 5 ) ( 8 ) 11/30/2033 Common Stock 23,380 ( 5 ) ( 5 ) ( 9 ) 23,380 D Employee Stock Option (Right to Buy) $ 16.8 06/20/2024 A 289,600 ( 10 ) 06/19/2034 Common Stock 289,600 $ 0 289,600 D

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

Explanation of Responses:

( 1 )Certain of these shares are subject to vesting and a repurchase right in favor of the Issuer, as follows: (i) 2,256 shares on July 10, 2024, (ii) 2,256 shares on August 10, 2024, (iii) 2,781 shares on November 30, 2024, and (iv) 4,079 shares on December 31, 2024, subject to the Reporting Person's continued service to the Issuer on each such vesting date. ( 2 )Received in exchange for 311,703 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. ( 3 )Received in exchange for 233,019 shares of common stock of Tectonic on the same terms and conditions as set forth in footnote (2) herein. ( 4 )These shares are held by the Reicin-Boiarsky Family Trust (the "Trust"). The Reporting Person's spouse is a co-trustee of the Trust. Accordingly, the Reporting Person may be deemed to have shared voting and dispositive power over the securities held by the Trust. The Reporting Person disclaims beneficial ownership of the shares held by the Trust except to the extent of her 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 )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. ( 6 )The shares subject to the option vest as follows: (i) 4,079 shares on June 30, 2024; (ii) 4,078 shares on July 31, 2024, (iii) 4,078 shares on August 31, 2024, (iv) 4,079 shares on September 30, 2024, (v) 4,078 shares on October 31, 2024, (vi) 1,297 shares on November 30, 2024, (vii) 4,078 shares on January 31, 2025, (viii) 4,078 shares on February 28, 2025 and (iv) 4,078 shares on March 31, 2025, subject to the Reporting Person's continued service to the Issuer on each such vesting date. ( 7 )Received in exchange for a stock option to acquire 63,478 shares of Tectonic common stock pursuant to the Merger Agreement. ( 8 )The shares subject to the option vest in 42 equal monthly installments beginning on July 1, 2024, subject to the Reporting Person's continued service to the Issuer on each such vesting date. ( 9 )Received in exchange for a stock option to acquire 43,750 shares of Tectonic common stock pursuant to the Merger Agreement. ( 10 )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.

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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