Spero director granted RSUs and stock options

Spero Therapeutics director Kathleen Tregoning received new equity awards.

Rhea-AI Filing Summary

Spero Therapeutics director Kathleen Tregoning received new equity awards. She was granted 10,000 restricted stock units, each convertible into one share of common stock upon vesting on June 23, 2027, subject to her continued service.

She also received stock options for 20,000 shares of common stock at an exercise price of $2.1500 per share, vesting in full on June 23, 2027 and expiring on June 23, 2036. Following these awards, she directly holds 85,000 shares of common stock.

Insider Trade Summary

Grant/Award: 30,000 shares

Grant/Award 2 txns

Insider Tregoning Kathleen

Role Director

Type	Security	Shares	Price	Value
Grant/Award	Stock Option (right to buy)	20,000	$0.00	$0.00
Grant/Award	Common Stock	10,000	$0.00	$0.00

Holdings After Transaction: Stock Option (right to buy) — 20,000 contracts (Direct); Common Stock — 85,000 shares (Direct)

Footnotes (2)

1. F1. 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. F2. 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.

Key Figures

RSU grant: 10,000 shares RSU vesting date: June 23, 2027 Stock options granted: 20,000 options +4 more

7 metrics

RSU grant 10,000 shares Restricted stock units granted on June 23, 2026

RSU vesting date June 23, 2027 RSUs vest if service continues to this date

Stock options granted 20,000 options Options on common stock granted June 23, 2026

Option exercise price $2.1500 per share Exercise price for 20,000 stock options

Option vesting date June 23, 2027 Options vest and become exercisable in full

Option expiration date June 23, 2036 Expiration of stock option term

Shares held after grant 85,000 shares Total common stock directly held after transactions

Key Terms

restricted stock units ("RSUs"), Stock Option (right to buy), vesting, exercise price, +1 more

5 terms

restricted stock units ("RSUs") financial

"Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting."

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.

Stock Option (right to buy) financial

"Stock Option (right to buy) with an exercise price of 2.1500 per share."

vesting financial

"The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service."

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.

exercise price financial

"conversion_or_exercise_price: 2.1500 for the stock option grant."

The exercise price is the fixed amount at which you can buy or sell an asset, like a stock, when using an options contract. It matters because it helps determine whether exercising the option will be profitable or not, depending on the current market price. Think of it as the set price you agree on today to buy or sell later.

expiration date financial

"The shares underlying this option will vest and become exercisable in full on June 23, 2027 and expire on June 23, 2036."

The expiration date is the deadline after which a financial contract, such as an option or a futures agreement, is no longer valid or can be exercised. It matters to investors because it determines the timeframe during which they can take action or benefit from the contract, similar to how a coupon or a food item has a limited period of usefulness. Once the expiration date passes, the contract loses its value or ability to be used.

FAQ

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

What equity awards did Spero Therapeutics (SPRO) director Kathleen Tregoning receive?

Kathleen Tregoning received 10,000 restricted stock units and stock options for 20,000 shares. The RSUs convert into common stock at vesting, and the options give her the right to buy common shares at a fixed exercise price.

When do Kathleen Tregoning’s new Spero Therapeutics (SPRO) RSUs vest?

The 10,000 restricted stock units vest on June 23, 2027, if she continues serving through that date. Each RSU then converts into one share of Spero Therapeutics common stock, increasing her direct share ownership when the vesting condition is met.

What are the key terms of Kathleen Tregoning’s new Spero Therapeutics stock options?

She received options on 20,000 shares of common stock with a $2.1500 exercise price. These options vest and become exercisable in full on June 23, 2027, and expire on June 23, 2036, provided she continues serving as a director.

How many Spero Therapeutics (SPRO) shares does Kathleen Tregoning hold after these grants?

After the equity awards, Kathleen Tregoning directly holds 85,000 shares of Spero Therapeutics common stock. This figure reflects her post-transaction ownership reported in the filing and excludes the 20,000 underlying shares tied to the newly granted stock options.

Are Kathleen Tregoning’s Spero Therapeutics RSUs and options tied to continued service?

Yes. The RSUs vest on June 23, 2027, only if she continues serving through that date, and the options similarly vest and become exercisable in full on June 23, 2027, subject to her continued service as a director.

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

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Accepted by SEC EDGAR 06/25/2026 - 07:17 PM EDT Learn about SEC filing dates

SEC Form 4

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

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).

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^*

Tregoning Kathleen

(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)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/23/2026

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

X	Form 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)
			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 Kathleen Tregoning	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)