Sec Form 13G Filing - PFIZER INC @ SPERO THERAPEUTICS INC

Insider filing report for Changes in Beneficial Ownership

Schedule 13G & 13D forms are used to report a party's ownership of stock which exceeds 5% of a company's total stock issue.
Schedule 13G is a shorter version of Schedule 13D with fewer reporting requirements.

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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549


SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. )*

Spero Therapeutics, Inc.
(Name of Issuer)

Common Stock, $0.001 par value
(Title of Class of Securities)

84833T103
(CUSIP Number)


June 30, 2021
(Date of Event Which Requires Filing of this 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. 84833T103
1.	NAME OF REPORTING PERSON: PFIZER INC.
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: 2,362,348 shares of common stock, $0.001 par value per share ("Common Stock")
		6.	SHARED VOTING POWER: 0
		7.	SOLE DISPOSITIVE POWER: 2,362,348 shares of Common Stock
		8.	SHARED DISPOSITIVE POWER: 0
9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON: 2,362,348 shares of Common Stock are beneficially owned by Pfizer Inc.
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES			[ ]
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.37%(1)
12.	TYPE OF REPORTING PERSON CO

(1) Based on 29,699,147 shares of Common Stock of the Issuer outstanding, as of June 24, 2021, as reported in the Issuer’s Definitive Proxy Statement on Schedule 14A filed with the Securities and Exchange Commission on July 6, 2021, plus 2,362,348 shares of Common Stock of the Issuer issued by the Issuer and acquired by the reporting person on July 1, 2021.

ITEM 1.
(A) NAME OF ISSUER:
Spero Therapeutics, Inc.

(B) ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICE:

675 Massachusetts Avenue, 14th Floor
Cambridge, Massachusetts 02139

ITEM 2.

(A) NAME OF PERSONS FILING:

Pfizer Inc.

(B) ADDRESS OF PRINCIPAL BUSINESS OFFICE OR IF NONE, RESIDENCE:

235 E. 42nd Street, New York, NY 10017

Delaware, U.S.A.

(D) TITLE OF CLASS OF SECURITIES:

Common Stock

(E) CUSIP NUMBER:

84833T103

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: Not applicable.
(a) Broker or dealer registered under section 15 of the Act (15 U.S.C. 78os).
(b) Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).
(c) Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).
(d) Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).
(e) An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E).
(f ) An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F).
(g) A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G).
(h) A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813).
(i) 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) A non-US institution, in accordance with §4.13d-1(b)(1)(ii)(J);
(k) Group, in accordance with §230.405 240.13d-1(b)(1)(ii)(K).

If filing as a non-US institution in accordance with §240.13d-1(b)(1)(ii)(J), please specify the type of institution: Not applicable.

ITEM 4. OWNERSHIP.

See rows 5 through 11 of the cover page.

ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS

Not applicable.

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 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. 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, other than activities solely in connection with a nomination under §240.14a-11.

SIGNATURE

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

Dated: July 9, 2021


			PFIZER INC.
			By:			/s/ Susan Grant
			Name:			Susan Grant
			Title:			Assistant Secretary

Sec Form 13G Filing - PFIZER INC (PFE) filing for SPERO THERAPEUTICS INC (SPRO) - 2021-07-09