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    SEC Form SCHEDULE 13G filed by Sutro Biopharma Inc.

    4/4/25 4:32:32 PM ET
    $STRO
    Biotechnology: Biological Products (No Diagnostic Substances)
    Health Care
    Get the next $STRO alert in real time by email



    SECURITIES AND EXCHANGE COMMISSION
    Washington, D.C. 20549


    SCHEDULE 13G


    UNDER THE SECURITIES EXCHANGE ACT OF 1934
    Sutro Biopharma, Inc.

    (Name of Issuer)


    Common Stock, $0.001 par value per share

    (Title of Class of Securities)


    869367102

    (CUSIP Number)


    03/28/2025

    (Date of Event Which Requires Filing of this Statement)


    Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
    Checkbox not checked   Rule 13d-1(b)
    Checkbox checked   Rule 13d-1(c)
    Checkbox not checked   Rule 13d-1(d)






    SCHEDULE 13G

    CUSIP No.
    869367102


    1Names of Reporting Persons

    RA Capital Management, L.P.
    2Check the appropriate box if a member of a Group (see instructions)

    Checkbox not checked  (a)
    Checkbox not checked  (b)
    3Sec Use Only
    4Citizenship or Place of Organization

    DELAWARE
    Number of Shares Beneficially Owned by Each Reporting Person With:
    5Sole Voting Power

    0.00
    6Shared Voting Power

    4,434,637.00
    7Sole Dispositive Power

    0.00
    8Shared Dispositive Power

    4,434,637.00
    9Aggregate Amount Beneficially Owned by Each Reporting Person

    4,434,637.00
    10Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

    Checkbox not checked
    11Percent of class represented by amount in row (9)

    5.3 %
    12Type of Reporting Person (See Instructions)

    IA, PN


    SCHEDULE 13G

    CUSIP No.
    869367102


    1Names of Reporting Persons

    Peter Kolchinsky
    2Check the appropriate box if a member of a Group (see instructions)

    Checkbox not checked  (a)
    Checkbox not checked  (b)
    3Sec Use Only
    4Citizenship or Place of Organization

    UNITED STATES
    Number of Shares Beneficially Owned by Each Reporting Person With:
    5Sole Voting Power

    0.00
    6Shared Voting Power

    4,434,637.00
    7Sole Dispositive Power

    0.00
    8Shared Dispositive Power

    4,434,637.00
    9Aggregate Amount Beneficially Owned by Each Reporting Person

    4,434,637.00
    10Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

    Checkbox not checked
    11Percent of class represented by amount in row (9)

    5.3 %
    12Type of Reporting Person (See Instructions)

    HC, IN


    SCHEDULE 13G

    CUSIP No.
    869367102


    1Names of Reporting Persons

    Rajeev Shah
    2Check the appropriate box if a member of a Group (see instructions)

    Checkbox not checked  (a)
    Checkbox not checked  (b)
    3Sec Use Only
    4Citizenship or Place of Organization

    UNITED STATES
    Number of Shares Beneficially Owned by Each Reporting Person With:
    5Sole Voting Power

    0.00
    6Shared Voting Power

    4,434,637.00
    7Sole Dispositive Power

    0.00
    8Shared Dispositive Power

    4,434,637.00
    9Aggregate Amount Beneficially Owned by Each Reporting Person

    4,434,637.00
    10Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

    Checkbox not checked
    11Percent of class represented by amount in row (9)

    5.3 %
    12Type of Reporting Person (See Instructions)

    HC, IN


    SCHEDULE 13G

    CUSIP No.
    869367102


    1Names of Reporting Persons

    RA Capital Healthcare Fund, L.P.
    2Check the appropriate box if a member of a Group (see instructions)

    Checkbox not checked  (a)
    Checkbox not checked  (b)
    3Sec Use Only
    4Citizenship or Place of Organization

    DELAWARE
    Number of Shares Beneficially Owned by Each Reporting Person With:
    5Sole Voting Power

    0.00
    6Shared Voting Power

    4,434,637.00
    7Sole Dispositive Power

    0.00
    8Shared Dispositive Power

    4,434,637.00
    9Aggregate Amount Beneficially Owned by Each Reporting Person

    4,434,637.00
    10Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

    Checkbox not checked
    11Percent of class represented by amount in row (9)

    5.3 %
    12Type of Reporting Person (See Instructions)

    PN


    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, CA, 94080.
    Item 2. 
    (a)Name of person filing:

    The names of the persons filing this report (collectively, the "Reporting Persons") are: RA Capital Management, L.P. ("RA Capital") Peter Kolchinsky Rajeev Shah RA Capital Healthcare Fund, L.P. (the "Fund") The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G.
    (b)Address or principal business office or, if none, residence:

    The address of the principal business office of each of the Reporting Persons is: c/o RA Capital Management, L.P., 200 Berkeley Street, 18th Floor, Boston MA 02116
    (c)Citizenship:

    RA Capital and the Fund are Delaware limited partnerships. Dr. Kolchinsky and Mr. Shah are United States citizens.
    (d)Title of class of securities:

    Common Stock, $0.001 par value per share
    (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)Checkbox not checked   Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
    (b)Checkbox not checked   Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
    (c)Checkbox not checked   Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
    (d)Checkbox not checked   Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
    (e)Checkbox not checked   An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
    (f)Checkbox not checked   An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
    (g)Checkbox not checked   A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
    (h)Checkbox not checked   A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
    (i)Checkbox not checked   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)Checkbox not checked   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)Checkbox not checked   Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
     
    Item 4.Ownership
    (a)Amount beneficially owned:

    Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference. The Fund directly holds 4,434,637 shares of common stock. RA Capital Healthcare Fund GP, LLC is the general partner of the Fund. The general partner of RA Capital is RA Capital Management GP, LLC, of which Dr. Kolchinsky and Mr. Shah are the controlling persons. RA Capital serves as investment adviser for the Fund and may be deemed a beneficial owner, for purposes of Section 13(d) of the Act, of any securities of the Issuer held by the Fund. The Fund has delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in the Fund's portfolio, including the shares of the Issuer's common stock reported herein. Because the Fund has divested voting and investment power over the reported securities it holds and may not revoke that delegation on less than 61 days' notice, the Fund disclaims beneficial ownership of the securities it holds for purposes of Section 13(d) of the Act. As managers of RA Capital, Dr. Kolchinsky and Mr. Shah may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of any securities of the Issuer beneficially owned by RA Capital. RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial ownership of the securities reported in this Schedule 13G other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing of this Schedule 13G shall not be deemed an admission that either RA Capital, Dr. Kolchinsky, or Mr. Shah is the beneficial owner of such securities for any other purpose.
    (b)Percent of class:

    Row 11 of each Reporting Person's cover page to this Schedule 13G sets forth the percentages of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference. The percentage set forth in Row 11 of each Reporting Person's cover page is based upon 83,775,336 shares of the Issuer's common stock outstanding as of March 6, 2025, as reported in the Issuer's Annual Report on Form 10-K filed with the Securities and Exchange Commission (the "SEC") on March 13, 2025.
    (c)Number of shares as to which the person has:
     (i) Sole power to vote or to direct the vote:

    Row 5 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.

     (ii) Shared power to vote or to direct the vote:

    Row 6 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.

     (iii) Sole power to dispose or to direct the disposition of:

    Row 7 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.

     (iv) Shared power to dispose or to direct the disposition of:

    Row 8 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.

    Item 5.Ownership of 5 Percent or Less of a Class.
     
    Item 6.Ownership of more than 5 Percent on Behalf of Another Person.
     
    Not Applicable
    Item 7.Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
     
    Not Applicable
    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.

     
    RA Capital Management, L.P.
     
    Signature:/s/ Peter Kolchinsky
    Name/Title:By Peter Kolchinsky, Authorized Signatory
    Date:04/04/2025
     
    Peter Kolchinsky
     
    Signature:/s/ Peter Kolchinsky
    Name/Title:Peter Kolchinsky
    Date:04/04/2025
     
    Rajeev Shah
     
    Signature:/s/ Rajeev Shah
    Name/Title:Rajeev Shah
    Date:04/04/2025
     
    RA Capital Healthcare Fund, L.P.
     
    Signature:/s/ Peter Kolchinsky
    Name/Title:By RA Capital Healthcare Fund GP, LLC, its General Partner, By Peter Kolchinsky, Manager
    Date:04/04/2025
    Exhibit Information

    Exhibit 99.1 Joint Filing Agreement

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