Spero Therapeutics CMO files initial ownership report

Spero Therapeutics, Inc. filed an initial insider ownership report for Debra Zack, who serves as Chief Medical Officer.

Accepted by SEC EDGAR 08/06/2026 - 06:41 PM EDT Learn about SEC filing dates

Rhea-AI Filing Summary

Spero Therapeutics, Inc. filed an initial insider ownership report for Debra Zack, who serves as Chief Medical Officer. The report shows no equity transactions, acquisitions, or dispositions, and includes no current holdings or derivative positions, so no reportable beneficial ownership in Spero Therapeutics securities is disclosed for this officer in this filing.

Key Figures

Reported buy transactions: 0 Reported sell transactions: 0 Derivative transactions reported: 0 +1 more

4 metrics

Reported buy transactions 0 BuyCount in Form 3 insider transaction summary

Reported sell transactions 0 SellCount in Form 3 insider transaction summary

Derivative transactions reported 0 derivativeTransactionCount in insider transaction summary

Holding entries reported 0 holdingEntries in insider transaction summary

Key Terms

Power of Attorney, Chief Medical Officer, reporting person

3 terms

Power of Attorney regulatory

"Remarks note Exhibit 24.1 - Power of Attorney"

A power of attorney is a legal document that allows one person to make decisions and act on behalf of another person, often in financial or legal matters. It’s like giving someone a trusted helper or agent the authority to handle important tasks if you are unable to do so yourself. This matters to investors because it can impact how their assets are managed or transferred if they become unable to oversee their affairs.

Chief Medical Officer other

"Officer title is listed as Chief Medical Officer"

A chief medical officer is a senior executive responsible for overseeing the health and medical strategies within an organization, often in the healthcare or pharmaceutical sectors. They play a key role in guiding decisions related to medical research, product safety, and healthcare policies, which can impact a company's reputation and success. For investors, understanding the chief medical officer's role helps gauge how well a company manages medical risks and advances its healthcare goals.

reporting person regulatory

"Reporting person section identifies Debra Zack"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What does Spero Therapeutics (SPRO) Debra Zack Form 3 report?

The Form 3 for Debra Zack at Spero Therapeutics (SPRO) reports her status as Chief Medical Officer and shows no reported stock holdings, transactions, or derivative positions, meaning no beneficial ownership in SPRO securities is disclosed for her in this filing.

Did Debra Zack buy or sell Spero Therapeutics (SPRO) shares in this Form 3?

No. The insider summary lists 0 buy transactions and 0 sell transactions for Debra Zack, with no individual transaction records, indicating no reported purchases or sales of Spero Therapeutics (SPRO) shares in this Form 3.

Does the Spero Therapeutics (SPRO) Form 3 show any options or derivatives for Debra Zack?

No. The filing’s derivative summary reports 0 derivative transactions and no remaining derivative positions, indicating that Debra Zack has no options or other derivative securities reported in this Form 3 for Spero Therapeutics (SPRO).

What position does Debra Zack hold at Spero Therapeutics (SPRO) in this filing?

Debra Zack is identified as an officer of Spero Therapeutics (SPRO) with the title Chief Medical Officer. She is not listed as a director or a 10% beneficial owner in this Form 3 insider report.

Is the Spero Therapeutics (SPRO) Debra Zack Form 3 tied to a Rule 10b5-1 plan?

The Form 3 does not indicate use of a Rule 10b5-1 trading plan and reports no transactions at all. It functions solely as an initial statement of insider status without documenting any trading activity in SPRO shares.

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

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SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

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:			3235-0104
Estimated average burden
hours per response:			0.5

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. Date of Event Requiring Statement (Month/Day/Year)
08/03/2026

3. Issuer Name and Ticker or Trading Symbol
Spero Therapeutics, Inc. [ SPRO ]

3a. Foreign Trading Symbol

5. If Amendment, Date of Original Filed (Month/Day/Year)

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Medical Officer

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

Remarks:

Chief Medical Officer Exhibit 24.1 - Power of Attorney

No securities are beneficially owned.

	/s/ Maegan Deare, Attorney-in-Fact for Debra Jeske Zack	08/06/2026
	** 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 5 (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 3: SEC 1473 (03-26)