UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C.  20549
 
 
SCHEDULE 13G
(Rule 13d-102)
 
Information Statement Pursuant to Rules 13d-1 and 13d-2
Under the Securities Exchange Act of 1934
(Amendment No.      )*
 
 
Sutro Biopharma Inc.
  (Name of Issuer)
 
Common stock, par value $0.001 per share
(Title of Class of Securities)
 
 

869367102

(CUSIP Number)
 
 

September 27, 2018

Date of Event Which Requires Filing of the Statement

  

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

 

¨ Rule 13d-1(b)
x Rule 13d-1(c)
¨ Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

 

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).

 

 

CUSIP No. 86936710213GPage 2 of 10 Pages

 

 

1.

 

NAME OF REPORTING PERSON

S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

 

Citadel Advisors LLC

 

2.

 

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(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

 

6.

 

SHARED VOTING POWER

 

1,748,421 shares

 

 

7.

 

SOLE DISPOSITIVE POWER

0

 

8.

 

 

SHARED DISPOSITIVE POWER

See Row 6 above

 

9.

 

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

See Row 6 above

 

10.

 

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES

CERTAIN SHARES

¨

 

11.

 

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

 

7.7%1

 

12.

 

 

TYPE OF REPORTING PERSON

IA; OO; HC

       

 

 

__________________

1The percentages reported in this Schedule 13G are based upon 22,823,630 shares of common stock outstanding (according to the prospectus filed by the issuer with the Securities and Exchange Commission on September 27, 2018).

 

 

 

CUSIP No. 86936710213GPage 3 of 10 Pages

 

 

1.

 

NAME OF REPORTING PERSON

S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

 

Citadel Advisors Holdings LP

 

2.

 

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(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

 

6.

 

SHARED VOTING POWER

 

1,748,421 shares

 

 

7.

 

SOLE DISPOSITIVE POWER

0

 

8.

 

 

SHARED DISPOSITIVE POWER

See Row 6 above

 

9.

 

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

See Row 6 above

 

10.

 

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES

CERTAIN SHARES

¨

 

11.

 

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

 

7.7%

 

12.

 

 

TYPE OF REPORTING PERSON

PN; HC

       

 

 

CUSIP No. 86936710213GPage 4 of 10 Pages

 

 

 

 

1.

 

NAME OF REPORTING PERSON

S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

 

Citadel GP LLC

 

2.

 

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(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

 

6.

 

SHARED VOTING POWER

 

1,748,421 shares

 

 

7.

 

SOLE DISPOSITIVE POWER

0

 

8.

 

 

SHARED DISPOSITIVE POWER

See Row 6 above.

 

9.

 

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

See Row 6 above.

 

10.

 

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES

CERTAIN SHARES

¨

 

11.

 

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

 

7.7%

 

12.

 

 

TYPE OF REPORTING PERSON

OO; HC

       

 

 

CUSIP No. 86936710213GPage 5 of 10 Pages

 

 

1.

 

NAME OF REPORTING PERSON

S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

 

Kenneth Griffin

 

2.

 

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a)    ¨

(b)    ¨

 

3.

 

SEC USE ONLY

 

 

4.

 

 

CITIZENSHIP OR PLACE OF ORGANIZATION

U.S. Citizen

 

 

NUMBER OF

SHARES

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

 

 

5.

 

SOLE VOTING POWER

0

 

6.

 

SHARED VOTING POWER

 

1,748,421 shares

 

 

7.

 

SOLE DISPOSITIVE POWER

0

 

8.

 

 

SHARED DISPOSITIVE POWER

See Row 6 above

 

9.

 

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

See Row 6 above

 

10.

 

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES

CERTAIN SHARES

¨

 

11.

 

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

 

7.7%

 

12.

 

 

TYPE OF REPORTING PERSON

IN; HC

       

 

 

CUSIP No. 86936710213GPage 6 of 10 Pages

 

 

Item 1(a)Name of Issuer

  

Sutro Biopharma Inc.

  

Item 1(b)Address of Issuer’s Principal Executive Offices

 

310 Utah Avenue, Suite 150, South San Francisco, California 94080

 

Item 2(a)Name of Person Filing

 

This Schedule 13G is being jointly filed by Citadel Advisors LLC (“Citadel Advisors”), Citadel Advisors Holdings LP (“CAH”), Citadel GP LLC (“CGP”) and Mr. Kenneth Griffin (collectively with Citadel Advisors, CAH and CGP, the “Reporting Persons”) with respect to shares of common stock of the above-named issuer owned by Citadel Global Equities Master Fund Ltd., a Cayman Islands limited company (“CG”), and Citadel Multi-Strategy Equities Master Fund Ltd., a Cayman Islands limited company (“CM”).

 

Citadel Advisors is the portfolio manager for CG and CM. CAH is the sole member of Citadel Advisors. CGP is the general partner of CAH. Mr. Griffin is the President and Chief Executive Officer of CGP, and owns a controlling interest in CGP.

 

The filing of this statement shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any securities covered by the statement other than the securities actually owned by such person (if any).

 

Item 2(b)Address of Principal Business Office

 

The address of the principal business office of each of the Reporting Persons is 131 S. Dearborn Street, 32nd Floor, Chicago, Illinois 60603.

 

Item 2(c)Citizenship

  

Each of Citadel Advisors, CGP and CSGP is organized as a limited liability company under the laws of the State of Delaware. CAH is organized as a limited partnership under the laws of the State of Delaware. Mr. Griffin is a U.S. citizen.

  

Item 2(d)Title of Class of Securities

 

Common stock, $0.001 par value

 

Item 2(e)CUSIP Number

 

869367102

 

 

CUSIP No. 86936710213GPage 7 of 10 Pages

 

Item 3If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b) or (c), check whether the person filing is a:

 

(a)¨ Broker or dealer registered under Section 15 of the Exchange Act;

 

(b)¨ Bank as defined in Section 3(a)(6) of the Exchange Act;

 

(c)¨ Insurance company as defined in Section 3(a)(19) of the Exchange Act;

 

(d)¨ Investment company registered under Section 8 of the Investment Company Act;

 

(e)¨ An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);

 

(f)¨ An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F);

 

(g)¨ A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G);

 

(h)¨ A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act;

 

(i)¨ A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act;

 

(j)¨ A non-U.S. institution in accordance with Rule 13d-1(b)(1)(ii)(J);

 

(k)¨ Group, in accordance with Rule 13d-1(b)(1)(ii)(K).

 

If filing as a non-U.S. institution in accordance with Rule 13d-1(b)(1)(ii)(J), please specify the type of institution: ____________.

 

 

CUSIP No. 86936710213GPage 8 of 10 Pages

 

Item 4Ownership

 

A.Citadel Advisors LLC

 

(a)Citadel Advisors may be deemed to beneficially own 1,748,421 shares of common stock.

 

(b)The number of shares Citadel Advisors may be deemed to beneficially own constitutes approximately 7.7% of the common stock outstanding.

 

(c)Number of shares as to which such person has:

 

(i)sole power to vote or to direct the vote: 0

 

(ii)shared power to vote or to direct the vote: 1,748,421

 

(iii)sole power to dispose or to direct the disposition of: 0

 

(iv)shared power to dispose or to direct the disposition of: 1,748,421

 

B.Citadel Advisors Holdings LP and Citadel GP LLC

 

(a)Each of CAH and CGP may be deemed to beneficially own 1,748,421 shares of common stock.

 

(b)The number of shares that each of CAH and CGP may be deemed to beneficially own constitutes approximately 7.7% of the common stock outstanding.

 

(c)Number of shares as to which such person has:

 

(i)sole power to vote or to direct the vote: 0

 

(ii)shared power to vote or to direct the vote: 1,748,421

 

(iii)sole power to dispose or to direct the disposition of: 0

 

(iv)shared power to dispose or to direct the disposition of: 1,748,421

 

 

CUSIP No. 86936710213GPage 9 of 10 Pages

 

C.Kenneth Griffin

 

(a)Mr. Griffin may be deemed to beneficially own 1,748,421 shares of common stock.

 

(b)The number of shares that Mr. Griffin may be deemed to beneficially own constitutes approximately 7.7% of the common stock outstanding.

 

(c)Number of shares as to which such person has:

 

(i)sole power to vote or to direct the vote: 0

 

(ii)shared power to vote or to direct the vote: 1,748,421

 

(iii)sole power to dispose or to direct the disposition of: 0

 

(iv)shared power to dispose or to direct the disposition of: 1,748,421

 

Item 5Ownership of Five Percent or Less of a Class

 

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following ¨.

 

Item 6Ownership of More than Five Percent on Behalf of Another Person

 

Not Applicable

 

Item 7Identification and Classification of the Subsidiary which Acquired the Security Being Reported on by the Parent Holding Company

 

See Item 2 above

 

Item 8Identification and Classification of Members of the Group

 

Not Applicable

 

Item 9Notice of Dissolution of Group

 

Not Applicable

 

Item 10Certification

 

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.

 

 

CUSIP No. 86936710213GPage 10 of 10 Pages

 

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

 

Dated this 4th day of October, 2018.

 

CITADEL ADVISORS LLC   CITADEL ADVISORS HOLDINGS LP
         
By: /s/ David Glockner   By: /s/ David Glockner
  David Glockner, Authorized Signatory     David Glockner, Authorized Signatory
         
CITADEL GP LLC   KENNETH GRIFFIN
         
By: /s/ David Glockner   By: /s/ David Glockner
  David Glockner, Authorized Signatory     David Glockner, attorney-in-fact*

 

____________________________

 

*David Glockner is signing on behalf of Kenneth Griffin as attorney-in-fact pursuant to a power of attorney previously filed with the Securities and Exchange Commission, and hereby incorporated by reference herein. The power of attorney was filed as an attachment to a filing by Citadel Advisors LLC on Schedule 13G for Roku, Inc. on January 17, 2018.

 

 

 

EXHIBIT 99.1

 

JOINT FILING AGREEMENT

 

The undersigned hereby agree that the Statement on Schedule 13G filed herewith (and any amendments thereto), relating to the common stock of Sutro Biopharma Inc., a Delaware corporation, is being filed jointly with the Securities and Exchange Commission pursuant to Rule 13d-1(c) under the Securities Exchange Act of 1934, as amended, on behalf of each of the undersigned.

 

This Agreement may be executed in counterparts and each of such counterparts taken together shall constitute one and the same instrument.

 

Dated this 4th day of October, 2018.

 

CITADEL ADVISORS LLC   CITADEL ADVISORS HOLDINGS LP
         
By: /s/ David Glockner   By: /s/ David Glockner
  David Glockner, Authorized Signatory     David Glockner, Authorized Signatory
         
CITADEL GP LLC   KENNETH GRIFFIN
         
By: /s/ David Glockner   By: /s/ David Glockner
  David Glockner, Authorized Signatory     David Glockner, attorney-in-fact*

 

 

 

 

 

 

 

 

________________

*David Glockner is signing on behalf of Kenneth Griffin as attorney-in-fact pursuant to a power of attorney previously filed with the Securities and Exchange Commission, and hereby incorporated by reference herein. The power of attorney was filed as an attachment to a filing by Citadel Advisors LLC on Schedule 13G for Roku, Inc. on January 17, 2018.