Form 4: Seres EVP sells shares to cover RSU taxes

Seres Therapeutics EVP Teresa L. Young vested 4,228 RSUs and sold 1,042 shares at $17.30 under a Rule 10b5-1 plan to cover taxes, ending with 8,401 shares owned directly.

Summary

• On 11/15/2025, EVP, Chief Commercial & Strategy Officer Teresa L. Young acquired 4,228 shares via RSU vesting (3,998 + 132 + 98) and sold 1,042 shares at $17.30 under a Rule 10b5-1 instruction to cover taxes.
• Direct beneficial ownership after the transactions: 8,401 shares.
• The 3,998 RSUs vested in a single installment on 11/15/2025.
• An RSU grant that vested 25% on 02/15/2024 continues to vest in 12 equal quarterly installments thereafter; 664 RSUs remained outstanding after the 11/15/2025 settlement.
• Another RSU grant that vested 25% on 02/15/2025 continues to vest in 12 equal quarterly installments thereafter; 878 RSUs remained outstanding after the 11/15/2025 settlement.
• The reported sales were effected pursuant to a Rule 10b5-1 instruction adopted on 03/05/2023 solely to cover taxes related to RSU vesting.

Sentiment

Score: 5

Explanation: Neutral: routine RSU vesting and a small 10b5-1 tax sale; no implications for fundamentals.

Positives

• Sales executed under a pre-established Rule 10b5-1 instruction (adopted 03/05/2023), supporting trading independence and transparency.
• Sale was tax-related and limited (1,042 shares sold vs. 4,228 shares acquired), implying a net ownership increase of 3,186 shares.
• Continuing RSU vesting schedule supports retention and alignment of executive incentives with shareholders.

Negatives

• Insider sale, even if solely tax-related, can be perceived negatively by some investors.
• Share issuance from RSU settlement modestly increases the share count (4,228 shares issued).

Future Outlook

No forward-looking guidance provided; only vesting schedules for outstanding RSUs are described.

Management Comments

• Sales were effected pursuant to a Rule 10b5-1 instruction adopted on 03/05/2023 solely to cover taxes related to RSU vesting.
• One RSU grant vested in full on 11/15/2025; other RSU grants vest 25% at initial dates (02/15/2024 and 02/15/2025) with the remainder vesting in 12 equal quarterly installments thereafter.

Industry Context

Insider tax-withholding sales around RSU vest dates are routine in biotech and broader life sciences; the 25% initial vesting followed by quarterly vesting and use of Rule 10b5-1 plans aligns with common executive compensation practices at peers.

Comparison to Industry Standards

• Vesting cadence (25% initial tranche then quarterly installments) is standard across large and mid-cap biotech firms (e.g., Moderna, Biogen).
• Use of Rule 10b5-1 plans for tax-withholding sales is consistent with governance best practices to mitigate trading discretion and optics.
• Transaction scale (net increase in ownership despite tax sale) aligns with typical executive equity settlement patterns and is non-remarkable relative to industry norms.

Stakeholder Impact

• Minor dilution from issuance of shares upon RSU settlement.
• Executive retains increased net ownership (+3,186 shares), aligning incentives with shareholders.
• Use of Rule 10b5-1 for tax sales supports governance transparency and reduces trading optics concerns.

Next Steps

• Remaining RSUs continue to vest in equal quarterly installments per the schedules disclosed.

Key Dates

Keywords

Seres Therapeutics, MCRB, Form 4, insider transaction, RSU vesting, Rule 10b5-1, Teresa L. Young, executive compensation, tax withholding sale, biotech