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

Reporting relationship: Chief Operating Officer
Issuer ticker: SPRO
Reported as of: 02 Feb 2026
Net transaction value: -$101,175
SEC form: 4
Accepted by SEC: 05 Feb 2026, 06:30:03 UTC
Prior SEC filing: 03 Sep 2025
Next SEC filing: 09 Feb 2026
Source filing: View source filing
Reporting owner signature: /s/ Maegan Deare, Attorney-in-Fact for Timothy Keutzer

Key filing fact

Timothy Keutzer filed Form 4 for Spero Therapeutics, Inc. (SPRO) on 05 Feb 2026.

Key facts

This page summarizes Timothy Keutzer's Form 4 filing for Spero Therapeutics, Inc. (SPRO).
5 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 05 Feb 2026, 06:30.

Change

Previous filing in this sequence was filed on 03 Sep 2025.
Current net transaction value: -$101,175.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001798155 Primary reporting owner

Keutzer Timothy

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

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

SPRO transaction

Common Stock

Award

Transaction value: $0
Shares: +68,000
Change %: +9.2%
Price: $0.000000
Shares after: 807,744
Date: 02 Feb 2026
Ownership: Direct
Footnotes: F1

SPRO transaction

Common Stock

Sale

Transaction value: $41,560
Shares: -18,891
Change %: -2.3%
Price: $2.20
Shares after: 788,853
Date: 02 Feb 2026
Ownership: Direct
Footnotes: F2

SPRO transaction

Common Stock

Sale

Transaction value: $51,839
Shares: -24,224
Change %: -3.1%
Price: $2.14
Shares after: 764,629
Date: 03 Feb 2026
Ownership: Direct
Footnotes: F2

SPRO transaction

Common Stock

Sale

Transaction value: $7,775
Shares: -3,471
Change %: -0.45%
Price: $2.24
Shares after: 761,158
Date: 04 Feb 2026
Ownership: Direct
Footnotes: F2

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

SPRO transaction Derivative

Stock Option (Right to Buy)

Award

Transaction value: $0
Shares: +137,000
Change %
Price: $0.000000
Shares after: 137,000
Date: 02 Feb 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 137,000
Exercise price: $2.23
Footnotes: F3

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 3 footnotes

Footnote 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.

Footnote 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.

Footnote 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.