Form 4: Seres CSO Henn Sells 1,257 Shares Post RSU Vest

Chief Scientific Officer Matthew R. Henn converted 4,236 RSUs and sold 1,257 shares at $17.3 under a pre-set Rule 10b5-1 plan to cover taxes, retaining 7,527 shares and 1,582 unvested RSUs.

Summary

• On 11/15/2025, Matthew R. Henn executed three RSU conversions totaling 4,236 shares of Seres Therapeutics common stock (3,998 + 140 + 98).
• On the same date, 1,257 shares were sold at $17.3 per share under a Rule 10b5-1 plan adopted on 04/13/2023 solely to cover taxes related to RSU vesting.
• Post-transactions, direct beneficial ownership stands at 7,527 common shares.
• Unvested RSUs remaining: 704 units from one award and 878 units from another, totaling 1,582 RSUs.
• One RSU grant vested in full on 11/15/2025; two other RSU grants vest in 12 equal quarterly installments after initial 25% tranches on 02/15/2024 and 02/15/2025.

Sentiment

Score: 6

Explanation: Neutral-to-slightly positive: a routine, tax-driven sale under a 10b5-1 plan with continued equity exposure and significant unvested RSUs.

Positives

• Sales were executed under a pre-established Rule 10b5-1 plan (adopted 04/13/2023), enhancing transparency and reducing timing discretion.
• Insider retains 7,527 common shares post-sale, indicating ongoing equity exposure.
• Significant remaining unvested RSUs (1,582 units) align incentives with shareholders and provide future ownership accrual.
• RSU conversions occurred at $0 exercise price, minimizing cash outlay.

Negatives

• An insider sale of 1,257 shares at $17.3 may be perceived negatively despite being for tax coverage.
• Common shareholding following the sale (7,527 shares) is modest, which may limit immediate exposure versus a larger outright ownership stake.

Future Outlook

Remaining RSUs will vest and settle in 12 equal quarterly installments following initial 25% vesting on 02/15/2024 and 02/15/2025; no financial guidance or operational outlook is provided.

Management Comments

• Sales were effected pursuant to a Rule 10b5-1 instruction adopted on 04/13/2023, solely to cover taxes in connection with RSU vesting.
• One RSU grant vested in a single installment on 11/15/2025; other RSUs vest quarterly after initial 25% tranches.

Industry Context

Executive tax-related sales and structured 10b5-1 plans are common across biotech and broader public companies, particularly around RSU vesting events; such activity generally has limited read-through to company fundamentals.

Comparison to Industry Standards

• Use of Rule 10b5-1 plans for tax-withholding sales aligns with standard practices at U.S. biotechs such as Moderna, Biogen, and Regeneron.
• Quarterly vesting schedules following an initial cliff are typical for executive RSU programs across the sector.
• The magnitude of shares sold (1,257) relative to ongoing holdings and unvested RSUs is consistent with routine tax-related transactions rather than discretionary liquidation.

Stakeholder Impact

• No dilution to shareholders; transactions relate to RSU vesting and an open-market sale.
• Limited impact on trading dynamics due to modest sale size; transparency enhanced by 10b5-1 usage.
• Employee and executive alignment maintained via remaining unvested RSUs.

Next Steps

• Ongoing quarterly vesting and settlement of remaining RSUs per schedules noted.
• Any subsequent insider transactions to be reported on future Forms 4.

Key Dates

Keywords

Seres Therapeutics, MCRB, Form 4, insider transaction, Rule 10b5-1, restricted stock units, RSU vesting, biotech, executive compensation, tax withholding