Sec Form 4 Filing - Skyline Venture Partners V LP @ SUTRO BIOPHARMA INC - 2018-10-01

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 Skyline Venture Partners V LP 2. Issuer Name and Ticker or Trading Symbol SUTRO BIOPHARMA INC [ STRO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 525 UNIVERSITY AVENUE 3. Date of Earliest Transaction (MM/DD/YY) 10/01/2018 (Street) PALO ALTO, CA94301 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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 10/01/2018 C 925,578 A 925,578 I By Skyline Venture Partners V, L.P. ( 2 ) Common Stock 10/01/2018 C 520,264 A 1,445,842 I By Skyline Venture Partners V, L.P. ( 2 ) Common Stock 10/01/2018 C 514,211 A 1,960,053 I By Skyline Venture Partners V, L.P. ( 2 )

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 Series C Preferred Stock ( 1 ) 10/01/2018 C 25,015,635 ( 1 ) ( 1 ) Common Stock 925,578 $ 0 0 I By Skyline Venture Partners V, L.P. ( 2 ) Series D Preferred Stock ( 3 ) 10/01/2018 C 12,846,023 ( 3 ) ( 3 ) Common Stock 520,264 $ 0 0 I By Skyline Venture Partners V, L.P. ( 2 ) Series E Preferred Stock ( 4 ) 10/01/2018 C 18,698,578 ( 4 ) ( 4 ) Common Stock 514,211 $ 0 0 I By Skyline Venture Partners V, L.P. ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Skyline Venture Partners V LP 525 UNIVERSITY AVENUE PALO ALTO, CA94301 X Skyline Venture Management V, LLC 525 UNIVERSITY AVENUE PALO ALTO, CA94301 X KANEKO YASUNORI 525 UNIVERSITY AVENUE PALO ALTO, CA94301 X Signatures Skyline Venture Partners V, L.P. By: Skyline Venture Management V, LLC Its: General Partner /s/ Kerensa Kenny, Attorney-in-Fact 10/03/2018 Signature of Reporting Person Date Skyline Venture Management V, LLC /s/ Kerensa Kenny, Attorney-in-Fact 10/03/2018 Signature of Reporting Person Date Yasunori Kaneko /s/ Kerensa Kenny, Attorney-in-Fact 10/03/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each share of the issuer's Series C Preferred Stock automatically converted into 0.0370 share of the issuer's Common Stock on October 1, 2018 in connection with the closing of the issuer's sale of its Common Stock in its firm commitment initial public offering (the "IPO") pursuant to a registration statement on Form S-1 (File No. 333-227103) under the Securities Act of 1933, as amended (the "Registration Statement"), and had no expiration date. ( 2 )These securities are held of record by Skyline Venture Partners V, L.P. ("Skyline L.P."). Skyline Venture Management V, LLC ("Skyline Management") is the general partner of Skyline L.P. John G. Freund and Yasunori Kaneko, are the managing directors of Skyline Management, and each may be deemed to share voting and investment power over the securities held by Skyline L.P. and disclaims beneficial ownership over such securities except to the extent of their pecuniary interest therein, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of the reported securities for purposes of Section 16 or for any other purposes. Mr. Freund is a director of the Issuer and, accordingly, files separate Section 16 reports. ( 3 )Each share of the issuer's Series D Preferred Stock automatically converted into 0.0405 share of the issuer's Common Stock on October 1, 2018 in connection with the closing of the issuer's sale of its Common Stock in its IPO pursuant to the Registration Statement, and had no expiration date. ( 4 )Each share of the issuer's Series E Preferred Stock automatically converted into 0.0275 share of the issuer's Common Stock on October 1, 2018 in connection with the closing of the issuer's sale of its Common Stock in its IPO pursuant to the Registration Statement, and had no expiration date.

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