[Form 4] Spero Therapeutics, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Spero Therapeutics director Ankit Mahadevia sold 6,572 shares of common stock on 08/28/2025 at $1.97 per share to satisfy tax withholding for RSUs that vested from a grant dated 08/26/2021. After the sale, the reporting person beneficially owns 703,294 shares, which includes 65,817 shares held by the Mahadevia-Mehta Family Trust where he is a trustee. The Form 4 was signed by an attorney-in-fact on 09/02/2025.

Positive

• Transparent disclosure of an insider transaction via Form 4
• Transaction was a sell-to-cover tied to RSU tax withholding, indicating a non-discretionary purpose

Negative

• Beneficial ownership decreased by 6,572 shares following the sale

Insights

Corporate Governance Expert

TL;DR: Routine sell-to-cover for RSU tax withholding; disclosure supports good governance and transparency.

The filing documents a tax-driven sale of 6,572 shares tied to RSU vesting. This is a common, non-discretionary transaction that does not indicate opportunistic trading by the director. Reporting the transaction on Form 4 ensures compliance with Section 16 reporting, preserving transparency around insider holdings. The remaining beneficial ownership of 703,294 shares, including trust-held shares, remains disclosed.

Securities Analyst

TL;DR: Transaction is immaterial to market capitalization but updates insider ownership figures.

The sale involved 6,572 shares at $1.97, a small fraction of the reported 703,294 shares beneficially owned post-transaction. Because the sale was to cover tax obligations from RSU vesting granted in 2021, it is procedural rather than a signal of changed sentiment. The filing clarifies the director's direct and trust-linked holdings for investor records.

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

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Mahadevia Ankit

(Last) (First) (Middle)

C/O SPERO THERAPEUTICS, INC.

675 MASSACHUSETTS AVENUE, 14TH FLOOR

(Street)

CAMBRIDGE MA 02139

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
08/28/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	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	08/28/2025		S(1)		6,572(1)	D	$1.97	703,294(2)	D

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

Explanation of Responses:

1. The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of restricted stock unit ("RSUs") that were granted to the Reporting Person on August 26, 2021.

2. Amount includes 65,817 shares of common stock held by the Mahadevia-Mehta Family Trust, of which the Reporting Person is a trustee.

	/s/ Maegan Deare, Attorney-in-Fact for Ankit Mahadevia	09/02/2025
	** Signature of Reporting Person	Date
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 Number.

FAQ

What transaction did Ankit Mahadevia report on Form 4 for SPRO?

The director reported a sale of 6,572 shares of Spero Therapeutics common stock on 08/28/2025 at $1.97 per share.

Why were the shares sold in this Form 4 filing for SPRO?

The sale was effected to cover tax withholding obligations pursuant to a 'sell to cover' provision in RSU agreements tied to an 08/26/2021 RSU grant.

How many shares does the reporting person own after the reported transaction?

703,294 shares beneficially owned are reported following the transaction.

Does the filing disclose any indirect holdings for Ankit Mahadevia?

Yes. The filing states 65,817 shares are held by the Mahadevia-Mehta Family Trust, of which he is a trustee.

When was the Form 4 signed and by whom?

The Form 4 was signed by Maegan Deare, Attorney-in-Fact for Ankit Mahadevia on 09/02/2025.