Form 4: Mersana Director's Shares & Options Disposed in Merger

Mersana Therapeutics Director Allene Diaz disposed of all common stock and options following the company's merger with Day One Biopharmaceuticals.

Summary

• Allene M. Diaz, a Director of Mersana Therapeutics, Inc. (MRSN), reported the disposition of all her beneficial ownership in the company's common stock and derivative securities.
• The transactions occurred on January 6, 2026, coinciding with the effective time of the merger between Mersana Therapeutics, Inc. and Day One Biopharmaceuticals, Inc. (Parent), through its subsidiary Emerald Merger Sub, Inc.
• Under the Merger Agreement dated November 12, 2025, Mersana shareholders received an Upfront Cash Consideration of $25.00 per share, net, plus one non-tradeable Contingent Value Right (CVR) per share.
• Each CVR represents the right to receive certain contingent milestone payments of up to an aggregate of $30.25 per CVR in cash, without interest and less any applicable tax withholding.
• Following the tender offer, Mersana Therapeutics, Inc. merged with Emerald Merger Sub, Inc., becoming a wholly-owned subsidiary of Day One Biopharmaceuticals, Inc.
• Stock options with an exercise price less than the Upfront Cash Consideration ('Cash-Out Options') became fully vested, cancelled, and converted into the Offer Price minus their exercise price.
• Stock options with an exercise price equal to or greater than the Upfront Cash Consideration ('OTM Options') became fully vested and exercisable for a limited period; those not exercised were cancelled without consideration.
• Allene Diaz disposed of 578 shares of common stock and various stock options, resulting in 0 shares and 0 derivative securities beneficially owned after the transaction.

Sentiment

Score: 7

Explanation: The completion of the merger provides a definitive exit for shareholders, offering an upfront cash payment and potential additional value through contingent value rights, which is a positive outcome for investors in the acquired entity.

Positives

• Shareholders of Mersana Therapeutics received a definitive upfront cash payment of $25.00 per share.
• Shareholders also received Contingent Value Rights (CVRs) offering potential additional payments of up to $30.25 per CVR upon achievement of specified milestones, providing potential upside beyond the initial cash consideration.

Negatives

• Mersana Therapeutics, Inc. ceased to be an independent publicly traded company, becoming a wholly-owned subsidiary of Day One Biopharmaceuticals, Inc.
• Out-of-the-money (OTM) stock options that were not exercised by the specified Last Exercise Date were cancelled without any consideration.

Risks

• The contingent value rights (CVRs) are non-tradeable, limiting liquidity for this portion of the consideration.
• Payments from CVRs are contingent upon the achievement of certain specified milestones, which are not guaranteed and may not be realized.
• The value of the CVRs is subject to the future performance and strategic decisions of Day One Biopharmaceuticals, Inc.

Future Outlook

Mersana Therapeutics, Inc. is now a wholly-owned subsidiary of Day One Biopharmaceuticals, Inc., and its independent public operations and strategic direction have ceased. The future outlook for the former Mersana assets and programs is integrated into Day One Biopharmaceuticals' strategy, with potential additional value for former Mersana shareholders tied to the achievement of specific contingent milestones.

Industry Context

This merger represents a strategic acquisition within the biotechnology and pharmaceutical industry, where larger companies often acquire smaller, innovative firms to expand their pipeline or gain access to specific technologies. The use of Contingent Value Rights (CVRs) is a common mechanism in biotech M&A to bridge valuation gaps and share future development risks and rewards.

Corporate Governance

Stakeholder Impact

• Shareholders: Received upfront cash consideration and contingent value rights (CVRs) for their shares, providing a defined exit value and potential future upside.
• Employees: Mersana employees are now part of Day One Biopharmaceuticals, Inc., subject to the acquiring company's policies and structure.

Next Steps

• Monitoring the achievement of specified milestones for potential contingent value right (CVR) payments.

Key Dates

Keywords

Mersana Therapeutics, Day One Biopharmaceuticals, Merger, Acquisition, Form 4, Insider Transaction, Stock Options, Contingent Value Right, CVR, Beneficial Ownership