Form: 4

Statement of changes in beneficial ownership of securities

October 2, 2018

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 OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
OMB APPROVAL
OMB Number: 3235-0287
Estimated average burden hours per response... 0.5

(Print or Type Responses)
1. Name and Address of Reporting Person *
Merck & Co., Inc.
   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)
2000 GALLOPING HILL ROAD		 3. Date of Earliest Transaction (Month/Day/Year)
10/01/2018
(Street)

KENILWORTH, NJ 07033		 4. If Amendment, Date Original Filed(Month/Day/Year)
 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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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   2,056,843 A (1) 2,056,843 I See Footnote (2)
Common Stock 10/01/2018   P   666,666 A $ 15 2,723,509 I See Footnote (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number. SEC 1474 (9-02)

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 (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 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
(Month/Day/Year)		 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 E Redeemable Convertible Preferred Stock (1) 10/01/2018   C     74,794,315   (1)   (1) Common Stock 2,056,843 $ 0 0 I See Footnote (2)

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Merck & Co., Inc.
2000 GALLOPING HILL ROAD
KENILWORTH, NJ 07033		     X    
Merck Sharp & Dohme Corp.
ONE MERCK DRIVE
WHITEHOUSE STATION, NJ 08889		     X    

Signatures

 Merck & Co., Inc. /s/ Faye C. Brown, Senior Assistant Secretary   10/02/2018
**Signature of Reporting Person Date
 Merck Sharp & Dohme Corp. /s/ Faye C. Brown, Assistant Secretary   10/02/2018
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Each share of Series E redeemable convertible preferred stock (the "Series E Preferred") automatically converted into 0.0275 shares of the Issuer's common stock upon the closing of the Issuer's sale of its common stock in its firm commitment underwritten initial public offering pursuant to a registration statement on Form S-1 (File No. 333-227103) under the Securities Act of 1933, as amended. The Series E Preferred had no expiration date.
(2) These securities are owned directly by Merck Sharp & Dohme Corp., which is a direct, wholly owned subsidiary of Merck & Co., Inc. ("Merck"). Merck is an indirect beneficial owner of the reported securities.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.