FORM 4
[X] 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
                                                                                  
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
                      

1. Name and Address of Reporting Person *

Aquilo Capital Management, LLC
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)
(Last)          (First)          (Middle)

ONE LETTERMAN DRIVE, SUITE D4900, BUILDING D
3. Date of Earliest Transaction (MM/DD/YYYY)

9/22/2022
(Street)

SAN FRANCISCO, CA 94129
(City)        (State)        (Zip)
4. If Amendment, Date Original Filed (MM/DD/YYYY)

 
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. Trans. Date 2A. Deemed Execution Date, if any 3. Trans. 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)9/22/2022  S  1335512 D$2.2503 3985719 (2)I See Footnotes (1)
Common Stock, $0.001 par value (1)9/22/2022  S  566284 D$2.2503 3419435 (3)I See Footnotes (1)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 3)
2. Conversion or Exercise Price of Derivative Security3. Trans. Date3A. Deemed Execution Date, if any4. Trans. Code
(Instr. 8)
5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)
6. Date Exercisable and Expiration Date7. 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 of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)11. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares

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 2,176,470 of the 3,985,719 shares deemed to be beneficially owned by Aquilo Capital Management, LLC. Aquilo Capital, LP sold 1,335,512 shares in this transaction on 09/22/2022.
(3) Aquilo Capital, LP owns only 2,176,470 of the 3,419,435 shares deemed to be beneficially owned by Aquilo Capital Management, LLC. Aquilo Capital, LP did not sell any of the 566,284 shares sold in this transaction on 09/22/2022.

Reporting Owners
Reporting Owner Name / Address
Relationships
Director10% OwnerOfficerOther
Aquilo Capital Management, LLC
ONE LETTERMAN DRIVE
SUITE D4900, BUILDING D
SAN FRANCISCO, CA 94129

X

Aquilo Capital, L.P.
ONE LETTERMAN DRIVE, SUITE D4900
BUILDING D, THE PRESIDIO
SAN FRANCISCO, CA 94129

X


Signatures
Aquilo Capital Management, LLC By: Marc Schneidman, its Managing Member, /s/ Marc Schneidman9/26/2022
**Signature of Reporting PersonDate

Aquilo Capital, L.P., By: Aquilo Capital Management, LLC, its General Partner By: Marc Schneidman, its Managing Member /s/ Marc Schneidman9/26/2022
**Signature of Reporting PersonDate


Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
*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).
Note:File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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.
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