Spero director granted RSUs and stock options

Spero Therapeutics director John C. Pottage Jr. reported equity awards consisting of both restricted stock units and stock options.

Rhea-AI Filing Summary

Spero Therapeutics director John C. Pottage Jr. reported equity awards consisting of both restricted stock units and stock options. He received 10,000 shares of Common Stock as restricted stock units that each convert into one share when they vest on June 23, 2027, subject to his continued service. Following this award, he directly holds 85,000 shares of common stock. He was also granted a stock option for 20,000 shares of common stock with an exercise price of $2.15 per share, expiring on June 23, 2036, which will vest and become exercisable in full on June 23, 2027 if he continues to serve as a director.

Insider Trade Summary

Grant/Award: 30,000 shares

Grant/Award 2 txns

Insider Pottage John C Jr

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 Shares held after grant: 85,000 shares Stock option size: 20,000 shares +2 more

5 metrics

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

Shares held after grant 85,000 shares Common stock directly held following RSU award

Stock option size 20,000 shares Underlying common shares for new option grant

Option exercise price $2.15 per share Exercise price of stock option granted June 23, 2026

Option expiration June 23, 2036 Expiration date of 20,000-share stock option

Key Terms

restricted stock units ("RSUs"), Stock Option (right to buy), vest, 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)"

vest financial

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

A vest is the process by which an employee earns the right to receive certain benefits or ownership interests, such as stock or retirement funds, over time. It’s similar to earning a reward gradually, ensuring that the benefit becomes fully yours only after a set period or meeting specific conditions. This makes it important for investors because it determines when they can actually claim or use those benefits.

exercise price financial

"conversion_or_exercise_price": "2.1500""

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

"expiration_date": "2036-06-23T00:00:00.000Z""

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 insider transactions did Spero Therapeutics (SPRO) disclose for John C. Pottage Jr.?

Spero Therapeutics disclosed that director John C. Pottage Jr. received 10,000 restricted stock units and a stock option for 20,000 shares at $2.15 per share, both granted on June 23, 2026 and subject to future vesting conditions.

How many Spero Therapeutics (SPRO) shares does John C. Pottage Jr. hold after this Form 4?

After these awards, John C. Pottage Jr. directly holds 85,000 shares of Spero Therapeutics common stock. In addition, he holds a stock option covering 20,000 shares, which is separate from his current share ownership and subject to vesting before exercise.

When do the new Spero Therapeutics (SPRO) restricted stock units for John C. Pottage Jr. vest?

The 10,000 restricted stock units granted to John C. Pottage Jr. vest on June 23, 2027. Each unit converts into one share of common stock, provided he continues to serve through that vesting date, aligning the award with ongoing board service.

What are the key terms of John C. Pottage Jr.’s new Spero Therapeutics (SPRO) stock option?

John C. Pottage Jr. received a stock option for 20,000 shares of common stock at an exercise price of $2.15 per share. The option vests in full on June 23, 2027, subject to continued service, and expires on June 23, 2036 if not exercised earlier.

Does the Spero Therapeutics (SPRO) Form 4 show any insider share sales by John C. Pottage Jr.?

The Form 4 reports only acquisitions through equity awards, not open-market sales. It shows grants of 10,000 restricted stock units and a 20,000-share stock option, with no reported dispositions or sales of Spero Therapeutics common stock in this filing.

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

Form 4 Insider Transactions: What Each Field Means →

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Accepted by SEC EDGAR 06/25/2026 - 06:55 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^*

Pottage John C Jr

(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 John C. Pottage, Jr.	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)