Amendment: SEC Form SC 13D/A filed by Tectonic Therapeutic Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

Tectonic Therapeutic, Inc.

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

878972108

(CUSIP Number)

Atlas Venture

Attention: Ommer Chohan, Chief Financial Officer

300 Technology Square, 8th Floor

Cambridge, MA 02139 USA

(857) 201-2700

(Name, Address and Telephone Number of Person Authorized to

Receive Notices and Communications)

October 24.2024

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. x

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

INTRODUCTION

This Amendment No. 1 to Schedule 13D (“Amendment No. 1”) is being filed as an amendment to the statement on Schedule 13D relating to common stock, par value $0.0001 per share (the “Common Stock”) of Tectonic Therapeutic, Inc. (formerly, AVROBIO, Inc.), a Delaware corporation (the “Issuer” or “Tectonic”), as filed with the Securities and Exchange Commission (the “SEC”) on July 30, 2019 (the “Initial Schedule 13D”). All capitalized terms not otherwise defined herein shall have the meanings ascribed to the terms in the Initial Schedule 13D. This Amendment No. 1 is being filed to report the sale of shares by Atlas X, as described herein, and gives effect to the 12-for-1 reverse stock of the Issuer’s common stock effected and completion of the reverse merger of the Issuer with Tectonic Therapeutic, Inc. (the “Reverse Merger”), each of which became effective on June 20, 2024.

The Initial Schedule 13D is hereby amended and supplemented as follows and, except as expressly amended below, the Prior Schedule 13D remains in full force and effect.

As of the date of this filing, the Reporting Persons’ are no longer the beneficial owner of more than five percent of Issuer’s securities and are no longer required to report the Reporting Persons’ holdings on a Schedule 13D.

ITEM 1. SECURITY AND ISSUER

The class of equity securities to which this Schedule 13D relates is common stock, par value $0.0001 per share (the “Common Stock”) of Tectonic Therapeutic, Inc. (formerly, AVROBIO, Inc.), a Delaware corporation (the “Issuer” or “Tectonic”). The principal executive offices of the Issuer are located at 490 Arsenal Way, Suite 210, Watertown, Massachusetts 02472.

ITEM 2. IDENTITY AND BACKGROUND

Item 2(b) of the Initial Schedule 13D is hereby amended and restated as follows:

ITEM 4. PURPOSE OF TRANSACTION

Item 4 of the Initial Schedule 13D is hereby amended and supplemented as follows:

Effective upon the completion of the Reverse Merger, Bruce Booth, D.Phil., resigned as a director of the Issuer.

ITEM 5. INTEREST IN SECURITIES OF THE ISSUER

Item 5 of the Initial Schedule 13D is hereby amended and restated as follows:

As of the date hereof, AVA X LP is the record owner of 1,709 shares of Common Stock. AVA X LLC is the general partner of AVA X LP. Each of AVA X LP and AVA X LLC has shared voting and dispositive power over the shares held by AVA X LP. As such, each of AVA X LP and AVA X LLC may be deemed to beneficially own the shares held by AVA X LP.

As of the date hereof, AVOF is the record owner of 67,567 shares of Common Stock. AVAO LP is the general partner of AVOF and AVAO LLC is the general partner of AVAO LP. Each of AVOF, AVAO LP and AVAO LLC has shared voting and dispositive power over the shares held by AVOF. As such, each of AVOF, AVAO LP and AVAO LLC may be deemed to beneficially own the shares held by AVOF.

Each of the Fund X Reporting Persons and Opportunity Fund Reporting Persons may be deemed to beneficially own 0.1% and 0.5%, respectively, of the Issuer’s outstanding Common Stock, which percentages are calculated based upon 14,734,479 outstanding shares of Common Stock, as reported in the Issuer's prospectus supplement filed with the Securities and Exchange Commission on August 14, 2024.

Collectively, the Reporting Persons beneficially own an aggregate of 78,447 shares of Common Stock, which represents 0.5% of the Issuer's outstanding Common Stock. The Fund X Reporting Persons and the Opportunity Fund Reporting Persons are under common control and as a result, the Reporting Persons may be deemed to be members of a group. However, the Reporting Persons disclaim such group membership, and this Schedule 13D shall not be deemed an admission that the Reporting Persons are members of a group for purposes of Section 13 or for any other purposes.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: October 28, 2024