Suvretta Capital Management, Averill Master Fund and Aaron Cowen filed an amended Schedule 13G reporting shared beneficial ownership of Sutro Biopharma common stock equal to approximately 6.49 million shares for Suvretta/Cowen and 6.46 million shares for Averill, each representing 7.7% of the class. The filing shows no sole voting or dispositive power and instead reports shared voting and dispositive power for the reported shares. The filing states these securities are directly owned by advisory clients of Suvretta and that, other than Averill, no advisory client is deemed to beneficially own more than 5% of the class. The reporting persons disclaim beneficial ownership except for pecuniary interests and certify the holdings were not acquired to change or influence control of the issuer.
Positive
None.
Negative
None.
Insights
TL;DR: A coordinated disclosure shows sizable, passive stakes of 7.7% each, useful for ownership transparency but not an explicit control change.
The Schedule 13G/A reports that Suvretta, Averill and Aaron Cowen collectively disclose substantial shared holdings in Sutro Biopharma with shared voting and dispositive power and no sole authority. For market participants this confirms concentrated ownership among related reporting persons and advisory clients, which can affect float and potential voting outcomes on material matters even if the filing disclaims any intent to influence control. The statement that securities are held by advisory clients clarifies beneficial ownership channels and identifies Averill as the only advisory client exceeding 5%.
TL;DR: The filing documents significant coordinated holdings but emphasizes passive intent and disclaimers against seeking control.
The amendment highlights shared voting/dispositive power across the reporting group, which is important for assessing potential coalition voting power at shareholder meetings. The explicit disclaimer and certification that the positions were not acquired to change control reduce immediate governance alarm but do not eliminate the significance of a near-8% stake. Investors and issuers should note the presence of a joint filing agreement and exhibit references that formally document the group's relationship.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 4)
Sutro Biopharma, Inc.
(Name of Issuer)
Common Stock, $0.001 par value
(Title of Class of Securities)
869367102
(CUSIP Number)
06/30/2025
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
SCHEDULE 13G
CUSIP No.
869367102
1
Names of Reporting Persons
Suvretta Capital Management, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
6,488,324.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,488,324.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,488,324.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
7.7 %
12
Type of Reporting Person (See Instructions)
IA, OO
SCHEDULE 13G
CUSIP No.
869367102
1
Names of Reporting Persons
Averill Master Fund, Ltd.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
CAYMAN ISLANDS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
6,461,305.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,461,305.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,461,305.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
7.7 %
12
Type of Reporting Person (See Instructions)
CO
SCHEDULE 13G
CUSIP No.
869367102
1
Names of Reporting Persons
Aaron Cowen
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
6,488,324.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,488,324.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,488,324.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
7.7 %
12
Type of Reporting Person (See Instructions)
HC, IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Sutro Biopharma, Inc.
(b)
Address of issuer's principal executive offices:
111 Oyster Point Blvd, South San Francisco, California, 94080
Item 2.
(a)
Name of person filing:
Suvretta Capital Management, LLC
Averill Master Fund, Ltd.
Aaron Cowen
(b)
Address or principal business office or, if none, residence:
Suvretta Capital Management, LLC
540 Madison Avenue, 7th Floor
New York, New York 10022
United States of America
Averill Master Fund, Ltd.
c/o Maples Corporate Services Limited
P.O. Box 309
Ugland House
Grand Cayman KY1-1104
Cayman Islands
Aaron Cowen
c/o Suvretta Capital Management, LLC
540 Madison Avenue, 7th Floor
New York, New York 10022
(c)
Citizenship:
Suvretta Capital Management, LLC - Delaware
Averill Master Fund, Ltd. - Cayman Islands
Aaron Cowen - United States
(d)
Title of class of securities:
Common Stock, $0.001 par value
(e)
CUSIP No.:
869367102
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Ownership of more than 5 Percent on Behalf of Another Person.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
All of the securities reported in this Schedule 13G Amendment No. 4 are directly owned by advisory clients of Suvretta Capital Management, LLC. None of those advisory clients, other than Averill Master Fund, Ltd., may be deemed to beneficially own more than 5% of the Common Stock, $0.001 par value.
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary.
Please see Exhibit B attached hereto.
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.
SIGNATURE
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.
Suvretta Capital Management, LLC
Signature:
/s/ Andrew Nathanson
Name/Title:
Andrew Nathanson/General Counsel and Chief Compliance Officer
Date:
08/13/2025
Averill Master Fund, Ltd.
Signature:
/s/ Andrew Nathanson
Name/Title:
Andrew Nathanson/Authorized Signatory
Date:
08/13/2025
Aaron Cowen
Signature:
/s/ Aaron Cowen
Name/Title:
Aaron Cowen
Date:
08/13/2025
Comments accompanying signature: * Each Reporting Person disclaims beneficial ownership of the reported securities except to the extent of his, her or its pecuniary interest therein, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.
To the extent that "ownership of 5 percent or less of a class" was indicated in Item 5, such response only applies to the Reporting Person(s) that indicated elsewhere herein that it beneficially owns five percent (5%) or less of the class.
Exhibit Information
[Exhibit A - Joint Filing Agreement]
[Exhibit B - Control Person Identification]
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