SC 13G/A 1 tm214737d22_sc13ga.htm SC 13G/A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

(Rule 13d-102)

Under the Securities Exchange Act of 1934

(Amendment No. 3)*

Sutro Biopharma, Inc.

(Name of Issuer)

Common stock, par value $0.001 per share

(Title of Class of Securities)

869367102

(CUSIP Number)

December 31, 2020

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. 869367102

13G/A

Page 2 of 14 Pages

NAME OF REPORTING PERSON

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

Citadel Advisors LLC

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

SHARED VOTING POWER

1,269,979 shares

SOLE DISPOSITIVE POWER

SHARED DISPOSITIVE POWER

See Row 6 above

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)

2.8%¹

12.

TYPE OF REPORTING PERSON

IA; OO; HC

The percentages reported in this Schedule 13G/A are based upon 44,992,978 shares of common stock outstanding after completion of the issuer’s public offering and the underwriters’ exercise of the over-allotment option (according to the issuer’s prospectus supplement as filed with the Securities and Exchange Commission on December 9, 2020).

CUSIP No. 869367102

13G/A

Page 3 of 14 Pages

NAME OF REPORTING PERSON

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

Citadel Advisors Holdings LP

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

SHARED VOTING POWER

1,269,979 shares

SOLE DISPOSITIVE POWER

SHARED DISPOSITIVE POWER

See Row 6 above

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)

2.8%

12.

TYPE OF REPORTING PERSON

PN; HC

CUSIP No. 869367102

13G/A

Page 4 of 14 Pages

NAME OF REPORTING PERSON

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

Citadel GP LLC

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

SHARED VOTING POWER

1,269,979 shares

SOLE DISPOSITIVE POWER

SHARED DISPOSITIVE POWER

See Row 6 above.

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)

2.8%

12.

TYPE OF REPORTING PERSON

OO; HC

CUSIP No. 869367102

13G/A

Page 5 of 14 Pages

NAME OF REPORTING PERSON

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

Citadel Securities LLC

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

SHARED VOTING POWER

11,945 shares

SOLE DISPOSITIVE POWER

SHARED DISPOSITIVE POWER

See Row 6 above.

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)

Less than 0.1%

12.

TYPE OF REPORTING PERSON

BD, OO

CUSIP No. 869367102

13G/A

Page 6 of 14 Pages

NAME OF REPORTING PERSON

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

CALC IV LP

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

SHARED VOTING POWER

31,825 shares

SOLE DISPOSITIVE POWER

SHARED DISPOSITIVE POWER

See Row 6 above.

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)

0.1%

12.

TYPE OF REPORTING PERSON

PN; HC

CUSIP No. 869367102

13G/A

Page 7 of 14 Pages

NAME OF REPORTING PERSON

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

Citadel Securities GP LLC

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

SHARED VOTING POWER

31,825 shares

SOLE DISPOSITIVE POWER

SHARED DISPOSITIVE POWER

See Row 6 above.

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)

0.1%

12.

TYPE OF REPORTING PERSON

OO; HC

CUSIP No. 869367102

13G/A

Page 8 of 14 Pages

NAME OF REPORTING PERSON

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

Kenneth Griffin

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

U.S. Citizen

NUMBER OF

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

SHARED VOTING POWER

1,301,804 shares

SOLE DISPOSITIVE POWER

SHARED DISPOSITIVE POWER

See Row 6 above

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)

2.9%

12.

TYPE OF REPORTING PERSON

IN; HC

CUSIP No. 869367102

13G/A

Page 9 of 14 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/A is being jointly filed by Citadel Advisors LLC (“Citadel Advisors”), Citadel Advisors Holdings LP (“CAH”), Citadel GP LLC (“CGP”), Citadel Securities LLC (“Citadel Securities”), CALC IV LP (“CALC4”), Citadel Securities GP LLC (“CSGP”) and Mr. Kenneth Griffin (collectively with Citadel Advisors, CAH, CGP, Citadel Securities, CALC4 and CSGP, the “Reporting Persons”) with respect to shares of common stock (and options to purchase common stock) of the above-named issuer owned by Citadel Multi-Strategy Equities Master Fund Ltd., a Cayman Islands limited company (“CM”), Citadel Securities, and CRBU Holdings LLC, a Delaware limited liability company (“CRBH”).

Citadel Advisors is the portfolio manager for CM. CAH is the sole member of Citadel Advisors. CGP is the general partner of CAH. CALC4 is the non-member manager of Citadel Securities and CRBH. CSGP is the general partner of CALC4. Mr. Griffin is the President and Chief Executive Officer of CGP, and owns a controlling interest in CGP and CSGP.

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, Citadel Securities and CSGP is organized as a limited liability company under the laws of the State of Delaware. Each of CALC4 and 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, par value $0.001 per share

Item 2(e)

CUSIP Number
869367102

CUSIP No. 869367102

13G/A

Page 10 of 14 Pages

Item 3

If 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. 869367102

13G/A

Page 11 of 14 Pages

Item 4

Ownership

Citadel Advisors LLC

(a)

Citadel Advisors may be deemed to beneficially own 1,269,979 shares of common stock.

	(b)	The number of shares that Citadel Advisors may be deemed to beneficially own constitutes approximately 2.8% 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: 1,269,979

(iii)

sole power to dispose or to direct the disposition of: 0

(iv)

shared power to dispose or to direct the disposition of: 1,269,979

Citadel Advisors Holdings LP and Citadel GP LLC

(a)

Each of Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own 1,269,979 shares of common stock.

	(b)	The number of shares that each of Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own constitutes approximately 2.8% 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: 1,269,979

(iii)

sole power to dispose or to direct the disposition of: 0

(iv)

shared power to dispose or to direct the disposition of: 1,269,979

Citadel Securities LLC

(a)

Citadel Securities LLC may be deemed to beneficially own 11,945 shares of common stock.

(b)

The number of shares that Citadel Securities LLC may be deemed to beneficially own constitutes less than 0.1% of the common stock outstanding.

CUSIP No. 869367102

13G/A

Page 12 of 14 Pages

(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: 11,945

(iii)

sole power to dispose or to direct the disposition of: 0

(iv)

shared power to dispose or to direct the disposition of: 11,945

CALC IV LP and Citadel Securities GP LLC

(a)

Each of CALC IV LP and Citadel Securities GP LLC may be deemed to beneficially own 31,825 shares of common stock.

	(b)	The number of shares that each of CALC IV LP and Citadel Securities GP LLC may be deemed to beneficially own constitutes approximately 0.1% 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: 31,825

(iii)

sole power to dispose or to direct the disposition of: 0

(iv)

shared power to dispose or to direct the disposition of: 31,825

Kenneth Griffin

(a)

Mr. Griffin may be deemed to beneficially own 1,301,804 shares of common stock.

	(b)	The number of shares that Mr. Griffin may be deemed to beneficially own constitutes approximately 2.9% 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: 1,301,804

(iii)

sole power to dispose or to direct the disposition of: 0

(iv)

shared power to dispose or to direct the disposition of: 1,301,804

CUSIP No. 869367102

13G/A

Page 13 of 14 Pages

Item 5

Ownership 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 x.

Item 6

Ownership of More than Five 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

See Item 2 above

Item 8

Identification and Classification of Members of the Group

Not Applicable

Item 9

Notice of Dissolution of Group

Not Applicable

Item 10

Certification
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. 869367102

13G/A

Page 14 of 14 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 16^th day of February, 2021.

CITADEL SECURITIES LLC		CITADEL ADVISORS LLC

By:	/s/ Guy Miller	By:	/s/ Gregory Johnson
	Guy Miller, Authorized Signatory		Gregory Johnson, Authorized Signatory

CALC IV LP		CITADEL ADVISORS HOLDINGS LP

By:	/s/ Guy Miller	By:	/s/ Gregory Johnson
	Guy Miller, Authorized Signatory		Gregory Johnson, Authorized Signatory

CITADEL SECURITIES GP LLC		CITADEL GP LLC

By:	/s/ Guy Miller	By:	/s/ Gregory Johnson
	Guy Miller, Authorized Signatory		Gregory Johnson, Authorized Signatory

		KENNETH GRIFFIN

		By:	/s/ Gregory Johnson
			Gregory Johnson, attorney-in-fact^*

Gregory Johnson 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 Jaws Acquisition Corp. on February 1, 2021.

SEC Form SC 13G/A filed