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Mersana Therapeutics (NASDAQ: MRSN) bought with $25 cash CVR payout

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Mersana Therapeutics director Willard H. Dere reported changes in his holdings following the completion of a merger in which Mersana became a wholly owned subsidiary of Day One Biopharmaceuticals. Each share of Mersana common stock tendered in the offer was exchanged for $25.00 in cash per share plus one contingent value right (CVR) per share, with the CVR providing for potential milestone payments of up to $30.25 per CVR in cash. In connection with the merger’s effective time on January 6, 2026, Dere’s 1,567 shares of common stock and multiple stock options were either cashed out or cancelled in accordance with the merger agreement mechanics, leaving him with no reported remaining Mersana equity.

Positive

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Negative

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Insights

Director equity is cashed out or cancelled under fixed $25 plus CVR merger terms.

The report shows how a completed merger between Mersana Therapeutics and Day One Biopharmaceuticals affects a director’s equity. Each Mersana share tendered into the offer was exchanged for $25.00 in cash plus one CVR, with each CVR tied to contingent milestone payments of up to $30.25 in cash, subject to specified milestones under a contingent value rights agreement. After the tender offer, Emerald Merger Sub merged into Mersana, which continues as a wholly owned subsidiary of Day One as of January 6, 2026.

The filing also details treatment of employee and director stock options. Options with an exercise price below the $25.00 upfront cash consideration became fully vested and were automatically cancelled in exchange for the offer price minus the option’s exercise price. Options with an exercise price equal to or above $25.00 were fully vested and exercisable only for a limited window before closing; any such options not exercised by the last exercise date were cancelled at the effective time with no consideration. Dere’s positions reflect these rules, with his reported common stock and all listed stock options reduced to zero.

From an investor perspective, this clarifies the per-share economics for Mersana stockholders—upfront cash plus CVR—and the final status of outstanding options at closing. It does not, by itself, provide information on how these terms compare to prior trading levels or broader valuation metrics, but it confirms that legacy Mersana equity, including director grants, has been converted or extinguished under the merger agreement.

Insider Dere Willard H
Role Director
Type Security Shares Price Value
Disposition Stock Option (right to buy) 2,460 $0.00 --
Disposition Stock Option (right to buy) 800 $0.00 --
Disposition Stock Option (right to buy) 544 $0.00 --
Disposition Stock Option (right to buy) 1,000 $0.00 --
Disposition Stock Option (right to buy) 450 $0.00 --
Disposition Stock Option (right to buy) 368 $0.00 --
Disposition Stock Option (right to buy) 125 $0.00 --
Disposition Stock Option (right to buy) 1,002 $0.00 --
Disposition Stock Option (right to buy) 513 $0.00 --
Disposition Stock Option (right to buy) 1,800 $0.00 --
Disposition Stock Option (right to buy) 734 $0.00 --
Disposition Stock Option (right to buy) 2,200 $0.00 --
U Common Stock 1,567 $0.00 --
Holdings After Transaction: Stock Option (right to buy) — 0 shares (Direct); Common Stock — 0 shares (Direct)
Footnotes (1)
  1. Pursuant to the terms of that certain Agreement and Plan of Merger (the "Merger Agreement"), by and among the Issuer, Day One Biopharmaceuticals, Inc. ("Parent") and Parent's direct wholly-owned subsidiary, Emerald Merger Sub, Inc. ("Purchaser"), dated as of November 12, 2025, the shares (the "Shares") of common stock, par value $0.0001 per share, of the Issuer (the "Common Stock") that were tendered to Purchaser prior to the expiration time of the Offer were exchanged for: (i) $25.00 per Share, net to the stockholder in cash, without interest and less any applicable tax withholding (the "Upfront Cash Consideration"), plus (ii) one non-tradeable contingent value right per Share (each, a "CVR"), (continued from footnote 1) which 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, upon the achievement of certain specified milestones in accordance with the terms and subject to the conditions of a contingent value rights agreement entered into by Parent and the rights agent (the Upfront Cash Consideration plus one CVR, collectively, the "Offer Price"). After completion of the tender offer, pursuant to the terms of the Merger Agreement, Purchaser merged with and into the Issuer, effective as of January 6, 2026 (the "Effective Time"), with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent. Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each option to purchase shares of Common Stock ("Issuer Option") that was outstanding and unexercised as of immediately prior to the Effective Time and had an exercise price per Share that was less than the Upfront Cash Consideration (each, a "Cash-Out Option"), became fully vested and was automatically cancelled and converted into the right to receive, without interest and subject to deduction for any required tax withholding, (i) the Offer Price minus (ii) the exercise price payable per share of Common Stock underlying such Cash-Out Option. Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.
SEC Form 4
FORM 4 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
OMB APPROVAL
OMB Number: 3235-0287
Estimated average burden
hours per response: 0.5
X
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.
1. Name and Address of Reporting Person*
Dere Willard H

(Last) (First) (Middle)
C/O MERSANA THERAPEUTICS, INC.
840 MEMORIAL DRIVE

(Street)
CAMBRIDGE MA 02139

(City) (State) (Zip)
2. Issuer Name and Ticker or Trading Symbol
Mersana Therapeutics, Inc. [ MRSN ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
X Director 10% Owner
Officer (give title below) Other (specify below)
3. Date of Earliest Transaction (Month/Day/Year)
01/06/2026
4. If Amendment, Date of Original Filed (Month/Day/Year)
6. Individual or Joint/Group Filing (Check Applicable Line)
X Form filed by One Reporting Person
Form filed by More than One Reporting Person
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 01/06/2026 U(1)(2) 1,567 D (1)(2) 0 D
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year) 7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (right to buy) $9.0775 01/06/2026 D 2,460 (3) (3) Common Stock 2,460 (3) 0 D
Stock Option (right to buy) $434.5 01/06/2026 D 800 (4) (4) Common Stock 800 (4) 0 D
Stock Option (right to buy) $107.75 01/06/2026 D 544 (4) (4) Common Stock 544 (4) 0 D
Stock Option (right to buy) $107.75 01/06/2026 D 1,000 (4) (4) Common Stock 1,000 (4) 0 D
Stock Option (right to buy) $134 01/06/2026 D 450 (4) (4) Common Stock 450 (4) 0 D
Stock Option (right to buy) $572.5 01/06/2026 D 368 (4) (4) Common Stock 368 (4) 0 D
Stock Option (right to buy) $527.25 01/06/2026 D 125 (4) (4) Common Stock 125 (4) 0 D
Stock Option (right to buy) $372.5 01/06/2026 D 1,002 (4) (4) Common Stock 1,002 (4) 0 D
Stock Option (right to buy) $161 01/06/2026 D 513 (4) (4) Common Stock 513 (4) 0 D
Stock Option (right to buy) $90.5 01/06/2026 D 1,800 (4) (4) Common Stock 1,800 (4) 0 D
Stock Option (right to buy) $216 01/06/2026 D 734 (4) (4) Common Stock 734 (4) 0 D
Stock Option (right to buy) $56.5 01/06/2026 D 2,200 (4) (4) Common Stock 2,200 (4) 0 D
Explanation of Responses:
1. Pursuant to the terms of that certain Agreement and Plan of Merger (the "Merger Agreement"), by and among the Issuer, Day One Biopharmaceuticals, Inc. ("Parent") and Parent's direct wholly-owned subsidiary, Emerald Merger Sub, Inc. ("Purchaser"), dated as of November 12, 2025, the shares (the "Shares") of common stock, par value $0.0001 per share, of the Issuer (the "Common Stock") that were tendered to Purchaser prior to the expiration time of the Offer were exchanged for: (i) $25.00 per Share, net to the stockholder in cash, without interest and less any applicable tax withholding (the "Upfront Cash Consideration"), plus (ii) one non-tradeable contingent value right per Share (each, a "CVR"),
2. (continued from footnote 1) which 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, upon the achievement of certain specified milestones in accordance with the terms and subject to the conditions of a contingent value rights agreement entered into by Parent and the rights agent (the Upfront Cash Consideration plus one CVR, collectively, the "Offer Price"). After completion of the tender offer, pursuant to the terms of the Merger Agreement, Purchaser merged with and into the Issuer, effective as of January 6, 2026 (the "Effective Time"), with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent.
3. Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each option to purchase shares of Common Stock ("Issuer Option") that was outstanding and unexercised as of immediately prior to the Effective Time and had an exercise price per Share that was less than the Upfront Cash Consideration (each, a "Cash-Out Option"), became fully vested and was automatically cancelled and converted into the right to receive, without interest and subject to deduction for any required tax withholding, (i) the Offer Price minus (ii) the exercise price payable per share of Common Stock underlying such Cash-Out Option.
4. Pursuant to the terms of the Merger Agreement, effective as of 10 business days prior to the closing of the Merger (the "Acceleration Date"), each Issuer Option then outstanding and unexercised that had an exercise price per Share that was equal to or greater than the Upfront Cash Consideration (each, an "OTM Option"), became fully vested and exercisable up to and through the closing of regular trading on the Nasdaq Stock Market on the fifth business day following the Acceleration Date (the "Last Exercise Date"). OTM Options not exercised on or prior to the Last Exercise Date were cancelled and ceased to exist as of the Effective Time, and no consideration was delivered in exchange for such OTM Option.
/s/ Willard Dere 01/06/2026
** Signature of Reporting Person Date
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FAQ

What insider transaction does this Mersana Therapeutics (MRSN) Form 4 report?

The Form 4 reports changes in director Willard H. Dere’s Mersana holdings in connection with the completion of a merger. His 1,567 shares of common stock and multiple stock option grants were either cashed out or cancelled under the merger agreement, leaving him with no reported remaining Mersana equity.

What did Mersana Therapeutics (MRSN) shareholders receive in the Day One Biopharmaceuticals merger?

Each tendered share of Mersana common stock was exchanged for $25.00 in cash per share, plus one non-tradeable contingent value right (CVR) per share. Each CVR provides for potential cash milestone payments of up to an aggregate of $30.25 per CVR, subject to specified milestones and conditions.

How were Mersana cash-out stock options treated in this merger?

Under the merger agreement, each outstanding and unexercised Mersana stock option with an exercise price per share below $25.00 became fully vested and was automatically cancelled and converted into the right to receive the offer price minus the option exercise price per underlying share, in cash, subject to tax withholding.

What happened to out-of-the-money Mersana stock options held at $25.00 or above?

Each option with an exercise price per share equal to or greater than $25.00 became fully vested and exercisable from the acceleration date up through the fifth business day afterward. Any such out-of-the-money option not exercised by that last exercise date was cancelled at the effective time with no consideration.

What is the contingent value right (CVR) mentioned for Mersana (MRSN) shareholders?

The CVR is a non-tradeable right granted on a one-per-share basis to former Mersana stockholders. Each CVR represents the right to receive contingent cash milestone payments of up to an aggregate of $30.25 per CVR, if specified milestones are achieved under the contingent value rights agreement.

What corporate structure resulted from the Mersana and Day One Biopharmaceuticals deal?

After completion of the tender offer, Emerald Merger Sub, Inc. merged with and into Mersana Therapeutics. As of the January 6, 2026 effective time, Mersana continues as the surviving corporation and a wholly owned subsidiary of Day One Biopharmaceuticals.