Director Thomas Frank E was granted 10,000 shares, increasing direct ownership by 13% to 85,000 units (SEC Form 4)
$SPRO
Biotechnology: Pharmaceutical Preparations
Health Care
| 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 |
| |||||||||||||||
| 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*
(Street)
(Country) | 2. Issuer Name and Ticker or Trading Symbol
Spero Therapeutics, Inc. [ SPRO ] | 5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
| |||||||||||||||||||||||||
| 2a. Foreign Trading Symbol
| |||||||||||||||||||||||||||
| 3. Date of Earliest Transaction
(Month/Day/Year) 06/23/2026 | 6. Individual or Joint/Group Filing (Check Applicable Line)
| ||||||||||||||||||||||||||
| 4. If Amendment, Date of Original Filed
(Month/Day/Year) |
| 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 | 06/23/2026 | A | 10,000(1) | A | $0.00 | 85,000 | 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 | ||||||||
| Stock Option (right to buy) | $2.15 | 06/23/2026 | A | 20,000 | (2) | 06/23/2036 | Common Stock | 20,000 | $0.00 | 20,000 | D | ||||
| Explanation of Responses: |
| 1. Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service through the applicable vesting date. |
| 2. The shares underlying this option will vest and become exercisable in full on June 23, 2027 subject to the Reporting Person's continued service as a director through the vesting date. |
| /s/ Maegan Deare, Attorney-in-Fact for Frank E. Thomas | 06/25/2026 | |
| ** 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. | ||
| 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. | ||
| * Form 4: SEC 1474 (03-26) | ||