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Equity awards for Spero Therapeutics (SPRO) chief medical officer

(Neutral)
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Spero Therapeutics, Inc. reported that Chief Medical Officer Debra Zack received two equity awards on August 3, 2026. She was granted 162,311 RSUs under the 2019 Stock Incentive Plan, vesting in four equal annual installments beginning August 3, 2027, and stock options for 324,675 shares of common stock at an exercise price of $1.5400 per share, vesting 25% on August 3, 2027 with the remainder vesting in 36 equal monthly installments, all subject to continued service. The filing indicates these transactions were made pursuant to a Rule 10b5-1 trading plan.

Positive

  • None.

Negative

  • None.
Insider Zack Debra
Role Chief Medical Officer
Type Security Shares Price Value
Grant/Award Stock option (right to buy) F2 324,675 $0.00 $0.00
Grant/Award Common Stock F1 162,311 $0.00 $0.00
Holdings After Transaction: Stock option (right to buy) — 324,675 shares (Direct); Common Stock — 162,311 shares (Direct)
Footnotes (2)
  1. F1. Consists 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.
  2. F2. The 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.
RSU grant 162,311 shares Restricted stock units granted to Chief Medical Officer on 2026-08-03
Stock option grant 324,675 shares Stock options awarded to Chief Medical Officer on 2026-08-03
Option exercise price $1.5400 per share Conversion or exercise price of the stock option grant
Option initial vesting portion 25 % Portion of option vesting on August 3, 2027
RSU vesting schedule 4 annual installments RSUs vest in four equal annual installments beginning August 3, 2027
Remaining option vesting period 36 monthly installments Remaining options vest in 36 equal monthly installments after August 3, 2027
restricted stock units ("RSUs") financial
"Consists of restricted stock units ("RSUs") granted to Reporting Person under Issuer's 2019 Stock Incentive Plan."
Restricted stock units (RSUs) are a company promise to give an employee shares of stock (or cash equivalent) in the future, but only after certain conditions—usually staying with the company for a set time or hitting performance goals—are met. Investors watch RSUs because when they vest they increase the number of shares outstanding and can lead insiders to sell shares, affecting share price, company dilution and the true cost of employee pay.
2019 Stock Incentive Plan financial
"RSUs granted to Reporting Person under Issuer's 2019 Stock Incentive Plan."
Stock option (right to buy) financial
"security_title: Stock option (right to buy) with underlying Common Stock."
vesting financial
"Each RSU represents the right to receive one share of common stock upon vesting."
Vesting is the process by which you earn full ownership of something, like company stock or a retirement benefit, over time. It’s like earning the right to keep a gift piece by piece the longer you stay with a company, making sure employees stay committed before they receive all the benefits.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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FAQ

What equity awards did Spero Therapeutics (SPRO) grant to Chief Medical Officer Debra Zack?

Debra Zack received 162,311 RSUs and stock options for 324,675 shares of common stock. The options carry a $1.5400 exercise price and both awards were granted on August 3, 2026.

How do the RSUs granted by Spero Therapeutics (SPRO) to Debra Zack vest?

The 162,311 RSUs vest in four equal annual installments beginning on August 3, 2027. Each RSU represents the right to receive one share of common stock, subject to Zack’s continued service through each vesting date.

What are the vesting terms of Debra Zack’s new stock options at Spero Therapeutics (SPRO)?

The 324,675 stock options vest 25% on August 3, 2027, with the remaining 75% vesting in 36 equal monthly installments. Vesting is conditioned on Debra Zack’s continued service with the company.

What is the exercise price and expiration for Debra Zack’s Spero Therapeutics (SPRO) stock options?

The awarded stock options have an exercise price of $1.5400 per share and are exercisable for 324,675 shares of common stock. They are scheduled to expire on August 3, 2036, assuming they have vested and are not forfeited earlier.

Under which plan were Debra Zack’s equity awards from Spero Therapeutics (SPRO) granted?

Both the RSUs and the stock options were granted under Spero Therapeutics’ 2019 Stock Incentive Plan. This plan governs the terms of the awards, including vesting conditions tied to Debra Zack’s continued service.

Were Debra Zack’s Spero Therapeutics (SPRO) equity awards reported under a Rule 10b5-1 trading plan?

Yes. The filing’s Rule 10b5-1 checkbox is marked, indicating the reported equity awards were made pursuant to a Rule 10b5-1 trading plan, which pre-establishes transaction terms under SEC rules.
SEC Form 4
FORM 4UNITED 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
OMB APPROVAL
OMB Number:3235-0287
Estimated average burden
hours per response:0.5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
X
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*
Zack Debra

(Last)(First)(Middle)
C/O SPERO THERAPEUTICS, INC.
675 MASSACHUSETTS AVENUE, 14TH FLOOR

(Street)
CAMBRIDGE MASSACHUSETTS 02139

(City)(State)(Zip)

UNITED STATES

(Country)
2. Issuer Name and Ticker or Trading Symbol
Spero Therapeutics, Inc. [ SPRO ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
Director10% Owner
XOfficer (give title below)Other (specify below)
Chief Medical Officer
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
08/03/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm filed by One Reporting Person
Form filed by More than One Reporting Person
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)
CodeVAmount(A) or (D)Price
Common Stock08/03/2026A162,311(1)A$0.00162,311D
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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Stock option (right to buy)$1.5408/03/2026A324,675 (2)08/03/2036Common Stock324,675$0324,675D
Explanation of Responses:
1. Consists 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.
2. The 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.
/s/ Maegan Deare, Attorney-in-Fact for Debra Jeske Zack08/06/2026
** Signature of Reporting PersonDate
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)