Form 4: Seres Director Sells 217 Shares Under 10b5-1

Seres Therapeutics director Eric D. Shaff net-sold 217 shares at $17.30 under a pre-set 10b5-1 plan following RSU vesting and now directly owns 11,113 shares.

Summary

• Eric D. Shaff (Director) executed RSU settlements and a small sale on 2025-11-15.
• RSUs converted into 721 common shares in total (390 + 331) at $0 exercise price.
• Sold 217 shares at $17.30 per share pursuant to a Rule 10b5-1 plan solely to cover taxes.
• Direct holdings increased by a net 504 shares to 11,113 shares after these transactions.
• Remaining unvested/settled RSUs after the transactions: 1,954 (Grant 1) and 2,989 (Grant 2).
• Grant 1: 25% vested on 2024-02-15; remainder vests in 12 equal quarterly installments thereafter; no expiration.
• Grant 2: 25% vested on 2025-02-15; remainder vests in 12 equal quarterly installments thereafter; no expiration.
• Sales were effected under a Rule 10b5-1 plan adopted on 2023-03-02.

Sentiment

Score: 6

Explanation: Neutral-to-slightly positive: net increase in insider ownership and sales limited to tax coverage under a pre-established plan.

Positives

• Net increase in direct ownership of 504 shares, bringing total direct holdings to 11,113.
• Sales were limited (217 shares) and executed solely to cover taxes under a pre-established Rule 10b5-1 plan.
• Ongoing RSU vesting provides continued equity alignment (1,954 and 2,989 RSUs outstanding across two grants).

Negatives

• Insider sale occurred (217 shares), which can be perceived negatively despite being tax-related.

Future Outlook

RSU awards will continue to vest in 12 equal quarterly installments following the initial vesting dates (2024-02-15 and 2025-02-15); future automatic sales to cover taxes may occur under the existing Rule 10b5-1 plan.

Management Comments

• Sales were effected pursuant to a Rule 10b5-1 plan adopted on 2023-03-02, solely to cover taxes associated with RSU vesting.
• RSU grants vest 25% on the initial vest dates (2024-02-15 and 2025-02-15) with the remainder in 12 equal quarterly installments; RSUs have no expiration date.

Industry Context

Small, scheduled insider sales to cover taxes following RSU vesting are common practice in biotech and broader U.S. equities; such transactions generally do not imply a change in company fundamentals.

Comparison to Industry Standards

• Use of Rule 10b5-1 plans for tax-withholding sales is standard among biotech executives (e.g., routine filings by peers like Moderna, Vertex, Regeneron).
• The sale size (217 shares) is de minimis relative to typical tax-withholding sales seen at larger biotech peers, indicating limited market impact.
• Continued equity vesting with modest net share accumulation aligns with common executive compensation practices across the sector.

Stakeholder Impact

• Minimal dilution and market impact due to small sale size (217 shares).
• No cash impact to the company; transactions relate to executive compensation and tax withholding.
• Continued vesting supports management-shareholder alignment through sustained equity exposure.

Next Steps

• Ongoing quarterly RSU vesting per each grant’s schedule.
• Potential future automatic sales to cover tax obligations upon vesting under the Rule 10b5-1 plan.

Key Dates

Keywords

Seres Therapeutics, MCRB, Form 4, insider transaction, Eric D. Shaff, Rule 10b5-1, restricted stock units, RSU vesting, insider sale, beneficial ownership