Form 4: Mersana Therapeutics Merger Closes, Executive Equity Converted

Mersana Therapeutics, Inc. completed its merger with Day One Biopharmaceuticals, Inc., converting executive Timothy B Lowinger's equity holdings into cash and contingent value rights.

Summary

• Mersana Therapeutics, Inc. has been acquired by Day One Biopharmaceuticals, Inc. (Parent) through its subsidiary, Emerald Merger Sub, Inc. (Purchaser), effective January 6, 2026.
• The merger agreement was dated November 12, 2025.
• Shareholders received an Offer Price consisting of $25.00 per share in upfront cash consideration and 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.
• Timothy B Lowinger, SVP, Chief Sci.&Tech. Officer, reported the conversion of his beneficial ownership due to the merger.
• His 10,466 shares of Common Stock (including 160 shares acquired in June 2025 via an employee stock purchase plan) were exchanged for the Offer Price.
• Stock options with an exercise price less than the $25.00 upfront cash consideration became fully vested, were cancelled, and converted into the Offer Price minus their exercise price.
• Stock options with an exercise price equal to or greater than the $25.00 upfront cash consideration became fully vested and exercisable for a limited period; those not exercised by the Last Exercise Date were cancelled without consideration.
• Restricted Stock Units (RSUs) were automatically cancelled and converted into the right to receive the Offer Price.

Sentiment

Score: 7

Explanation: The merger successfully closed, providing shareholders with immediate cash and potential future value through CVRs. However, unexercised out-of-the-money options were cancelled without consideration, and the CVRs introduce future uncertainty.

Positives

• The merger successfully closed, providing Mersana Therapeutics shareholders with immediate cash consideration 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.
• Equity awards such as common stock, in-the-money stock options, and restricted stock units held by the reporting person were converted into cash and CVRs, providing liquidity and potential future value.

Negatives

• Stock options with an exercise price equal to or greater than the $25.00 upfront cash consideration (Out-of-the-Money Options) were cancelled without consideration if not exercised by a specific date prior to the merger's effective time.
• The contingent value rights are non-tradeable, limiting liquidity and immediate valuation for the potential future payments.
• Mersana Therapeutics, Inc. ceased to be an independent publicly traded company, becoming a wholly-owned subsidiary of Day One Biopharmaceuticals, Inc.

Risks

• The value of the contingent value rights (CVRs) is uncertain and dependent on the achievement of specific future milestones, which may or may not occur.
• CVRs are non-tradeable, meaning holders cannot sell them on the open market to realize their value before milestones are met or if they wish to exit the investment.
• Unexercised out-of-the-money stock options were cancelled without any consideration, resulting in a loss of potential value for holders of those specific options.

Future Outlook

Mersana Therapeutics, Inc. is now a wholly-owned subsidiary of Day One Biopharmaceuticals, Inc. The future financial outcome for former Mersana shareholders who received CVRs is contingent upon the achievement of specific milestones as outlined in the contingent value rights agreement.

Industry Context

This transaction represents a common strategy in the biotechnology and pharmaceutical sectors where larger companies acquire smaller firms, often for their pipeline assets or technological platforms. The inclusion of contingent value rights (CVRs) is a frequent mechanism used in such mergers to bridge valuation gaps and share the risk and reward of future drug development or commercialization milestones.

Comparison to Industry Standards

• The use of contingent value rights (CVRs) in this merger aligns with common practices in the biotechnology industry for acquisitions, particularly when the acquired company's value is heavily tied to future clinical or regulatory milestones.
• The structure of an upfront cash payment combined with CVRs is a standard approach to provide immediate value to shareholders while allowing the acquirer to mitigate risk associated with future development.

Stakeholder Impact

• Shareholders of Mersana Therapeutics, Inc. received cash and contingent value rights in exchange for their shares, concluding their investment in the independent public entity.
• Employees, including the reporting person, had their equity compensation converted according to the merger terms, impacting their personal financial holdings.
• Mersana Therapeutics, Inc. as a corporate entity ceased independent public operations and became a wholly-owned subsidiary of Day One Biopharmaceuticals, Inc.

Next Steps

• Monitoring the achievement of specified milestones that would trigger payments under the contingent value rights agreement.

Key Dates

Keywords

Mersana Therapeutics, Day One Biopharmaceuticals, Merger, Acquisition, Form 4, Beneficial Ownership, Stock Options, Restricted Stock Units, Contingent Value Rights, MRSN, Biotechnology, Pharmaceuticals