SEC Form 4 · accession 0001807743-26-000007
Spero Therapeutics, Inc. · SPRO
Statement of changes in beneficial ownership, as filed. Original on EDGAR ↗
Reporting owner
Debra Zack
Officer — Chief Medical Officer
Period of report
Aug 3, 2026
Accepted (ET)
Aug 6, 2026 · 6:49 pm EDT
Rule 10b5-1 plan
yes — trade under a plan
Issuer CIK
0001701108
Table I — non-derivative securities
| Security | Date | Code | Shares | Price | A/D | Owned after | D/I | Nature of ownership |
|---|---|---|---|---|---|---|---|---|
| Common StockF1 | Aug 3, 2026 | A | 162,311 | $0.00 | A | 162,311 | D |
Table II — derivative securities
| Security | Conv. / exercise price | Date | Code | Shares | A/D | Exercisable | Expires | Underlying | Underlying shares | Owned after | D/I |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Stock option (right to buy)F2 | $1.54 | Aug 3, 2026 | A | 324,675 | A | — | Aug 3, 2036 | Common Stock | 324,675 | 324,675 | D |
Explanation of responses
- F1Consists of restricted stock units ("RSUs") granted to Reporting Person under Issuer's 2019 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 August 3, 2027, subject to the Reporting Person's continued service through the applicable vesting date.
- F2The shares underlying this option vest as to 25% on August 3, 2027, with the remainder vesting in 36 equal monthly installments thereafter, subject to the Reporting Person's continued service through the applicable vesting date.