Spero Therapeutics (SPRO) CEO/CFO Rajavelu sells shares in automatic RSU tax transaction

Rhea-AI Filing Summary

Spero Therapeutics officer Esther Rajavelu reported automatic sales of Spero Therapeutics common stock to cover taxes from restricted stock unit (RSU) vesting. On February 6, 2026, she sold 37,101 shares and 50,816 shares, each at $2.36 per share, in sell-to-cover transactions that were not discretionary trades. After these tax-related sales, she directly beneficially owned 1,012,091 Spero Therapeutics shares.

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).

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^*

Rajavelu Esther

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
02/06/2026

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	02/06/2026		S(1)		37,101(1)	D	$2.36	1,062,907	D
Common Stock	02/06/2026		S(1)		50,816(1)	D	$2.36	1,012,091	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. Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

Remarks:

Chief Executive Officer, Chief Financial Officer and Chief Business Officer

	/s/ Maegan Deare, Attorney-in-Fact for Esther Rajavelu	02/09/2026
	** 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.
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FAQ

What did Spero Therapeutics (SPRO) disclose in this Form 4 filing?

Spero Therapeutics reported that officer Esther Rajavelu sold shares of common stock on February 6, 2026. The sales were automatic, tax-related "sell to cover" transactions tied to RSU vesting, not discretionary open-market trades by the officer.

How many Spero Therapeutics (SPRO) shares did Esther Rajavelu sell?

On February 6, 2026, Esther Rajavelu sold 37,101 Spero Therapeutics common shares and an additional 50,816 shares. Both transactions were executed at a price of $2.36 per share to satisfy tax withholding from RSU vesting.

What was the sale price of the SPRO shares in this Form 4?

Each reported sale of Spero Therapeutics common stock by Esther Rajavelu was executed at $2.36 per share. These transactions were not discretionary trades but automatic sales to cover tax withholding obligations related to the vesting of restricted stock units.

How many SPRO shares does Esther Rajavelu own after the reported transactions?

Following the February 6, 2026 transactions, Esther Rajavelu directly beneficially owned 1,012,091 shares of Spero Therapeutics common stock. This figure reflects her holdings after the automatic sell-to-cover stock sales to meet RSU-related tax obligations.

Were the Spero Therapeutics (SPRO) share sales by Esther Rajavelu discretionary trades?

No. The filing states the sales "occurred automatically" to satisfy tax withholding obligations from RSU vesting. They were structured as "sell to cover" transactions and explicitly do not represent discretionary trades by the reporting officer.

What is Esther Rajavelu’s role at Spero Therapeutics (SPRO) in this filing?

The filing lists Esther Rajavelu as an officer of Spero Therapeutics. The remarks specify that she serves as Chief Executive Officer, Chief Financial Officer and Chief Business Officer, making her a key member of the company’s senior leadership team.