STOCK TITAN

Seres Therapeutics (MCRB) officer sells shares after RSU vesting under 10b5-1 plan

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Seres Therapeutics, Inc. officer Matthew R. Henn reported several equity transactions. On May 15, 2026, he exercised restricted stock units (RSUs) that converted into 238 shares of common stock at a conversion price of $0.00 per share. The RSUs each represent a contingent right to one share of common stock and vest in quarterly installments. On May 18, 2026, he completed an open-market sale of 77 common shares at $7.53 per share, executed under a pre-arranged Rule 10b5-1 instruction adopted to cover taxes related to RSU vesting. Following these transactions, he directly held 7,838 common shares and 422 RSUs as reported in the filing, indicating a relatively small sale compared with his remaining equity position.

Positive

  • None.

Negative

  • None.
Insider Henn Matthew R
Role See Remarks
Sold 77 shs ($579.81)
Type Security Shares Price Value
Sale Common Stock 77 $7.53 $579.81
Exercise Restricted Stock Units 141 $0.00 --
Exercise Restricted Stock Units 97 $0.00 --
Exercise Common Stock 238 $0.00 --
Holdings After Transaction: Common Stock — 7,838 shares (Direct, null); Restricted Stock Units — 422 shares (Direct, null)
Footnotes (1)
  1. Each restricted stock unit represents a contingent right to receive one share of Issuer common stock. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on April 13, 2023, solely with the intent to cover taxes in connection with the vesting of the restricted stock units. The restricted stock units vested and settled as to 25% of the restricted stock units on February 15, 2024. The remainder of the restricted stock units have vested and settled or will vest and settle in 12 equal quarterly installments thereafter. The restricted stock units have no expiration date. The restricted stock units vested and settled as to 25% of the restricted stock units on February 15, 2025. The remainder of the restricted stock units have vested and settled or will vest and settle in 12 equal quarterly installments thereafter. The restricted stock units have no expiration date.
Shares sold 77 shares Open-market sale of common stock on May 18, 2026 at $7.53
Sale price $7.53 per share Price for 77 common shares sold on May 18, 2026
Common shares after sale 7,838 shares Direct holdings of common stock following reported transactions
Shares from RSU conversion 238 shares Common shares acquired via RSU exercises on May 15, 2026
RSUs converted (lot 1) 97 RSUs Restricted stock units converting into common stock on May 15, 2026
RSUs converted (lot 2) 141 RSUs Additional restricted stock units converting into common stock on May 15, 2026
RSUs remaining 422 RSUs Restricted stock units reported as held after RSU transactions
Rule 10b5-1 adoption date April 13, 2023 Date of instruction governing tax-related share sales
Restricted Stock Units financial
"The restricted stock units vested and settled as to 25% of the restricted stock units on February 15, 2024."
Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.
Rule 10b5-1 regulatory
"The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on April 13, 2023."
Rule 10b5-1 is a regulation that allows company insiders to buy or sell their shares at predetermined times, even if they have access to non-public information. It acts like setting a schedule in advance for transactions, helping prevent accusations of unfair trading. This rule provides a way for insiders to plan trades transparently, giving investors confidence that these transactions are not based on hidden information.
open market financial
"The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on April 13, 2023, solely with the intent to cover taxes in connection with the vesting of the restricted stock units."
An open market is a system where buying and selling of goods, services, or financial assets happen freely without restrictions or special controls. For investors, it means they can trade assets easily and quickly, which helps determine fair prices based on supply and demand. This environment encourages transparency and competition, making it easier to buy or sell with confidence.
derivative security financial
"Exercise or conversion of derivative security"
A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.
contingent right financial
"Each restricted stock unit represents a contingent right to receive one share of Issuer common stock."
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*
Henn Matthew R

(Last)(First)(Middle)
C/O SERES THERAPEUTICS, INC.
101 CAMBRIDGE PARK DRIVE

(Street)
CAMBRIDGE MASSACHUSETTS 02140

(City)(State)(Zip)

UNITED STATES

(Country)
2. Issuer Name and Ticker or Trading Symbol
Seres Therapeutics, Inc. [ MCRB ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
Director10% Owner
XOfficer (give title below)Other (specify below)
See Remarks
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
05/15/2026
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 Stock05/15/2026M238A(1)7,915D
Common Stock05/18/2026S(2)77D$7.537,838D
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
Restricted Stock Units(1)05/15/2026M141 (3) (3)Common Stock141$0422D
Restricted Stock Units(1)05/15/2026M97 (4) (4)Common Stock97$0683D
Explanation of Responses:
1. Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.
2. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on April 13, 2023, solely with the intent to cover taxes in connection with the vesting of the restricted stock units.
3. The restricted stock units vested and settled as to 25% of the restricted stock units on February 15, 2024. The remainder of the restricted stock units have vested and settled or will vest and settle in 12 equal quarterly installments thereafter. The restricted stock units have no expiration date.
4. The restricted stock units vested and settled as to 25% of the restricted stock units on February 15, 2025. The remainder of the restricted stock units have vested and settled or will vest and settle in 12 equal quarterly installments thereafter. The restricted stock units have no expiration date.
Remarks:
Chief Scientific Officer and EVP
/s/ Thomas J. DesRosier, attorney-in-fact for Matthew R. Henn05/19/2026
** 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)

FAQ

What insider transactions did Matthew R. Henn report at Seres Therapeutics (MCRB)?

Matthew R. Henn reported exercising restricted stock units into 238 Seres Therapeutics shares and selling 77 common shares. The sale occurred at $7.53 per share, alongside RSU vesting and settlement into common stock under his compensation arrangements.

How many Seres Therapeutics (MCRB) shares did Matthew R. Henn sell and at what price?

He sold 77 shares of Seres Therapeutics common stock at $7.53 per share. This open-market transaction was reported as a sale in the Form 4 and was executed under an existing Rule 10b5-1 trading instruction.

Were Matthew R. Henn’s Seres Therapeutics (MCRB) share sales under a Rule 10b5-1 plan?

Yes. The filing states the sales were effected under a Rule 10b5-1 instruction adopted on April 13, 2023. The instruction was established solely to cover taxes in connection with the vesting of restricted stock units granted to Henn.

How many Seres Therapeutics (MCRB) shares does Matthew R. Henn hold after these transactions?

After the reported transactions, Henn directly holds 7,838 Seres Therapeutics common shares. In addition, he holds 422 restricted stock units, each representing a contingent right to receive one share of issuer common stock upon vesting.

What restricted stock unit activity did Matthew R. Henn report for Seres Therapeutics (MCRB)?

He reported the conversion of 97 and 141 restricted stock units into an equal number of Seres Therapeutics common shares. These RSUs vest in quarterly installments after initial 25% vesting dates in February 2024 and February 2025, with no stated expiration date.