Timothy Keutzer - 02 Feb 2026 Form 4 Insider Report for Spero Therapeutics, Inc. (SPRO)

Role: Chief Operating Officer
Signature: /s/ Maegan Deare, Attorney-in-Fact for Timothy Keutzer
Issuer symbol: SPRO
Transactions as of: 02 Feb 2026
Net transactions value: -$101,175
Form type: 4
Filing time: 05 Feb 2026, 06:30:03 UTC
Previous filing: 03 Sep 2025
Next filing: 09 Feb 2026
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Keutzer Timothy	Chief Operating Officer	C/O SPERO THERAPEUTICS, INC., 675 MASSACHUSETTS AVENUE, 14TH FLOOR, CAMBRIDGE	/s/ Maegan Deare, Attorney-in-Fact for Timothy Keutzer	04 Feb 2026	0001798155

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	SPRO	Common Stock	Award	$0	+68,000	+9.2%	$0.000000	807,744	02 Feb 2026	Direct	F1
transaction	SPRO	Common Stock	Sale	$41,560	-18,891	-2.3%	$2.20	788,853	02 Feb 2026	Direct	F2
transaction	SPRO	Common Stock	Sale	$51,839	-24,224	-3.1%	$2.14	764,629	03 Feb 2026	Direct	F2
transaction	SPRO	Common Stock	Sale	$7,775	-3,471	-0.45%	$2.24	761,158	04 Feb 2026	Direct	F2

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	SPRO	Stock Option (Right to Buy)	Award	$0	+137,000		$0.000000	137,000	02 Feb 2026	Common Stock	137,000	$2.23	Direct	F3

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Consists of restricted stock units ("RSUs") granted to Reporting Person under Issuer's 2017 Stock Incentive Plan. Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest in four equal annual installments beginning on February 2, 2027, subject to the Reporting Person's continued service through the applicable vesting date.
F2	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.
F3	The shares underlying this option vest as to 25% on February 2, 2027, with the remainder vesting in 36 equal monthly installments thereafter, subject to the Reporting Person's continued service through the applicable vesting date.