Spero Therapeutics (SPRO) director receives 10,000 RSUs and 20,000-share option grant

Rhea-AI Filing Summary

Director Cynthia Smith of Spero Therapeutics, Inc. received new equity compensation in the form of restricted stock units and stock options. She was granted 10,000 shares of Common Stock at a price of $0.00 per share, increasing her direct holdings to 85,000 shares. She also received a stock option for 20,000 shares of Common Stock with an exercise price of $2.15 per share, expiring on June 23, 2036.

The 10,000 RSUs will vest on June 23, 2027, provided she continues serving through that date. The 20,000-share option will also vest and become fully exercisable on June 23, 2027 under the same service condition. These awards are compensation-related grants rather than open-market purchases or sales.

Insights

Equity Compensation Analyst

Routine director equity grants, adding time-based RSUs and options.

Spero Therapeutics granted director Cynthia Smith 10,000 RSUs and a 20,000-share stock option at an exercise price of $2.15. Both awards vest on June 23, 2027, contingent on continued board service.

These awards are recorded at a transaction price of $0.00 per share, reflecting compensation rather than market purchases. There are no open-market buys or sells, and the filing shows no remaining derivative positions beyond this new 20,000-share option grant.

Because the grants are time-based and service-contingent, they primarily align the director’s incentives with shareholders over the vesting period, without signaling any discretionary trading view on SPRO shares.

Insider Trade Summary

2 transactions reported

Mixed 2 txns

Insider Smith Cynthia

Role null

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

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

Footnotes (1)

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. 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 Option grant size: 20,000 shares +4 more

7 metrics

RSU grant 10,000 shares Restricted stock units granted June 23, 2026; vest June 23, 2027

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

Option grant size 20,000 shares Stock option covering common stock granted June 23, 2026

Option exercise price $2.15 per share Exercise price for 20,000-share stock option

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

RSU vesting date June 23, 2027 RSUs vest if service as director continues

Option vesting date June 23, 2027 Option vests and becomes exercisable in full

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 through the applicable vesting date."

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.

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 06/25/2026 - 07:15 PM Accepted by SEC EDGAR 06/25/2026 - 07:14 PM 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^*

Smith Cynthia

(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 Cynthia Smith	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)

FAQ

What did Cynthia Smith acquire in this Spero Therapeutics (SPRO) Form 4?

Cynthia Smith received equity compensation, not open-market shares. She was granted 10,000 restricted stock units and a stock option for 20,000 shares, both tied to Spero Therapeutics common stock, reflecting standard director compensation rather than trading activity.

When do Cynthia Smith’s new Spero Therapeutics RSUs and options vest?

Both awards vest on June 23, 2027. The 10,000 RSUs and the 20,000-share stock option each require Cynthia Smith to continue serving as a director through that date before they convert into shares or become exercisable.

What is the exercise price and expiration of Cynthia Smith’s SPRO stock option?

The new stock option covers 20,000 Spero Therapeutics common shares at an exercise price of $2.15 per share. The option expires on June 23, 2036, giving a long-dated opportunity to exercise once fully vested in 2027.

How many Spero Therapeutics shares does Cynthia Smith hold after these grants?

After the RSU grant, Cynthia Smith is reported as holding 85,000 shares of Spero Therapeutics common stock directly. This figure reflects her position following the 10,000-share RSU award detailed in the Form 4 filing.

Were there any open-market purchases or sales by Cynthia Smith in this SPRO Form 4?

No open-market trades occurred. The Form 4 only reports compensation-related acquisitions coded as “A”: 10,000 RSUs and a 20,000-share stock option. Both have a reported transaction price of $0.00 per share, indicating non-cash awards.