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  4. [Form 4] Seres Therapeutics, Inc. Insider Trading Activity

Seres Therapeutics (MCRB) CSO sells 81 shares after RSU vest

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

Rhea-AI Filing Summary

For Seres Therapeutics, Inc. (MCRB), President and Chief Scientific Officer Matthew R. Henn reported equity compensation activity and a small share sale. On August 15, 2026, he exercised and settled 238 restricted stock units into an equal number of common shares, stemming from RSU grants with vesting schedules described in the footnotes. On August 17, 2026, he then sold 81 common shares at $4.55 per share in an open-market transaction executed under a Rule 10b5-1 trading plan adopted on April 13, 2023, solely to cover taxes related to the RSU vesting.

Positive

  • None.

Negative

  • None.
Insider Henn Matthew R
Role See Remarks
Sold 81 shs ($368.55)
Approx. gross sale proceeds $368.55
Type Security Shares Price Value
Sale Common Stock F2 81 $4.55 $368.55
Exercise Restricted Stock Units F1, F3 140 $0.00 $0.00
Exercise Restricted Stock Units F1, F4 98 $0.00 $0.00
Exercise Common Stock F1 238 -- --
Holdings After Transaction: Restricted Stock Units — 867 shares (Direct); Common Stock — 7,995 shares (Direct)
Footnotes (4)
  1. F1. Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.
  2. F2. 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. F3. 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. F4. 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 81 shares Common stock sale on August 17, 2026
Sale price $4.55 per share Price for 81 common shares sold on August 17, 2026
RSUs converted 238 restricted stock units RSUs vested and settled into common stock on August 15, 2026
RSU component 1 140 restricted stock units Portion of RSUs with vesting starting February 15, 2024
RSU component 2 98 restricted stock units Portion of RSUs with vesting starting February 15, 2025
10b5-1 plan adoption date April 13, 2023 Adoption date of Rule 10b5-1 instruction covering the share sale
Rule 10b5-1 regulatory
"The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction"
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.
restricted stock units financial
"Each restricted stock unit represents a contingent right to receive one share"
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.
vest and settle financial
"The restricted stock units vested and settled as to 25% of the restricted stock units"

FAQ

What insider transactions did MCRB executive Matthew R. Henn report on this Form 4?
Matthew R. Henn reported exercising 238 RSUs into common stock on August 15, 2026 and selling 81 common shares at $4.55 on August 17, 2026. The sale was made under a pre-established Rule 10b5-1 plan.

How many Seres Therapeutics (MCRB) shares did the insider sell, and at what price?
He sold 81 shares of Seres Therapeutics common stock at $4.55 per share on August 17, 2026. The transaction was reported as an open-market or private sale executed under a Rule 10b5-1 trading plan.

What RSU activity did the MCRB executive report in this filing?
The executive reported vesting and settlement of 238 restricted stock units into an equal number of MCRB common shares on August 15, 2026. These RSUs relate to grants that vest in 25% tranches, followed by 12 equal quarterly installments.

Were the MCRB insider transactions made under a Rule 10b5-1 plan?
Yes. The filing states the sales were effected pursuant to a Rule 10b5-1 instruction adopted on April 13, 2023. The plan was used solely to cover taxes arising from the vesting of the restricted stock units.

What do the footnotes in the MCRB Form 4 say about the restricted stock units?
The footnotes explain each restricted stock unit equals one share of common stock and that grants vest 25% on a specified February 15 date, with the remainder vesting and settling in 12 equal quarterly installments and no expiration date.

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Form 4 Insider Transactions: What Each Field Means →
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)
08/15/2026		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 Stock08/15/2026M238A(1)8,076D
Common Stock08/17/2026S(2)81D$4.557,995D
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)08/15/2026M140 (3) (3)Common Stock140$0282D
Restricted Stock Units(1)08/15/2026M98 (4) (4)Common Stock98$0585D
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:
President and Chief Scientific Officer
/s/ Thomas J. DesRosier, Attorney-in-Fact for Matthew R. Henn08/18/2026
** 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)

Source: View Original Filing on SEC EDGAR