Spero Therapeutics (SPRO) Form 4 Change in insider ownership

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

Aquilo Capital Management, LLC

(Last) (First) (Middle)

ONE LETTERMAN DRIVE

SUITE D4900, BUILDING D

(Street)

SAN FRANCISCO CA 94129

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Spero Therapeutics, Inc. [ SPRO ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

Director	X	10% Owner
Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
09/13/2021

4. If Amendment, Date of 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

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, $0.001 par value(1)	09/13/2021		P		44,210	A	$18.5631	4,426,989(2)	I	See Footnotes(1)
Common Stock, $0.001 par value(1)	09/14/2021		P		2,156	A	$18.4937	4,429,145(3)	I	See Footnotes(1)

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 Securities Underlying Derivative Security (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: 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

1. Name and Address of Reporting Person^*

Aquilo Capital Management, LLC

(Last) (First) (Middle)

ONE LETTERMAN DRIVE

SUITE D4900, BUILDING D

(Street)

SAN FRANCISCO CA 94129

(City) (State) (Zip)

1. Name and Address of Reporting Person^*

Aquilo Capital, L.P.

(Last) (First) (Middle)

ONE LETTERMAN DRIVE, SUITE D4900

BUILDING D, THE PRESIDIO

(Street)

SAN FRANCISCO CA 94129

(City) (State) (Zip)

Explanation of Responses:

1. The reporting persons are Aquilo Capital, L.P. (the "Fund"), Aquilo Capital Management, LLC ("Aquilo") and Marc R. Schneidman. Aquilo is the general partner and investment adviser of the Fund and other funds managed by Aquilo that hold securities directly for the benefit of their investors. Aquilo may be deemed to beneficially own such securities indirectly as the investment adviser and general partner of the Fund and affiliated funds, and Mr. Schneidman may be deemed to beneficially own them indirectly as the control person of Aquilo. Each of, Aquilo, the Fund and Mr. Schneidman disclaims beneficial ownership of such securities except to the extent of his or its pecuniary interest therein.

2. Aquilo Capital, LP owns only 3,378,881 of the 4,426,989 shares deemed to be beneficially owned by Aquilo Capital Management, LLC. Aquilo Capital, LP did not purchase any of the 44,210 shares purchased in this transaction on 09/13/2021.

3. Aquilo Capital, LP owns only 3,378,881 of the 4,429,145 shares deemed to be beneficially owned by Aquilo Capital Management, LLC. Aquilo Capital, LP did not purchase any of the 2,156 shares purchased in this transaction on 09/14/2021.

	Aquilo Capital Management, LLC By: its Managing Member, /s/ Marc Schneidman	09/15/2021
	Aquilo Capital, L.P., By: Aquilo Capital Management, LLC, its General Partner By: Marc Schneidman, its Managing Member /s/ Marc Schneidman	09/15/2021
	** Signature of Reporting Person	Date
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