Sensei Biotherapeutics (SNSE) Proxy filing summary

Executive summary

• Supplement updates prior proxy statement regarding board reconstitution if key stockholder matters are approved.

• Board size will be set at five directors effective June 12, 2026, pending approvals.

• Forward-looking statements address timing and effectiveness of board appointments and related governance changes.

Voting matters and shareholder proposals

• Stockholders will vote on Required Company Stockholder Matters at the June 10, 2026 Annual Meeting.

• Board recommendations for each proposal remain unchanged from the definitive proxy statement.

Board of directors and corporate governance

• Appointment of Karen Vousden, Ph.D. delayed to later in 2026 for personal reasons; board to consider her in Q3 or Q4.

• Bob Holmen to be appointed chair of the Nominating and Corporate Governance Committee effective June 12, 2026.

• Board size to be set at five directors as of June 12, 2026, if proposals are approved.