Merger cashes out Mersana Therapeutics (NASDAQ: MRSN) insider awards

Rhea-AI Filing Summary

Mersana Therapeutics insider Alejandra Carvajal, SVP and Chief Legal Officer, reported automatic changes to her equity holdings following the company’s acquisition by Day One Biopharmaceuticals. Common shares tendered in the offer were exchanged for $25.00 per share in cash plus one contingent value right, which can pay up to an additional $30.25 per share if specified milestones are met. After the tender offer, Emerald Merger Sub merged into Mersana, making Mersana a wholly owned subsidiary of Day One.

Under the merger agreement, vested in-the-money stock options were cancelled in return for the cash-and-CVR offer price minus the option exercise price. Out-of-the-money options became fully vested shortly before closing but expired without payment if not exercised by the last exercise date. All outstanding restricted stock units were cancelled and converted into the right to receive the same offer price as common shares.

Insights

Equity compensation and M&A analyst

Mersana’s sale to Day One converts insider equity into cash and CVRs under preset merger terms.

The filing shows how Mersana Therapeutics equity awards held by SVP and Chief Legal Officer Alejandra Carvajal were treated in the completed merger with Day One Biopharmaceuticals. Common shares tendered into the offer receive $25.00 in cash per share plus one contingent value right that may pay up to an additional $30.25 in cash upon achieving specified milestones. This structure combines immediate liquidity with potential future milestone-based payments.

Stock options with exercise prices below $25.00 became fully vested and were cancelled in exchange for the offer value minus the exercise price, effectively cashing out in-the-money options. Options with exercise prices at or above the cash amount were fully vested for a limited window before closing; any such options not exercised by the last exercise date lapsed with no consideration. Restricted stock units were cancelled and replaced by the same cash-and-CVR offer price as common stock, aligning their treatment with shareholders’ outcome.

The mechanics described apply generally to the company’s equity plans, not just this individual, and confirm that at the effective time on January 6, 2026, Mersana became a wholly owned subsidiary of Day One. Actual value realized from the CVRs will depend on whether the specified milestones are met under the contingent value rights agreement.

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
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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^*

Carvajal Alejandra

(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)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	SVP, Chief Legal Officer

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)		3,131	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)	$16.0125	01/06/2026		D			3,047	(3)	(3)	Common Stock	3,047	(3)	0	D
Stock Option (right to buy)	$16.0125	01/06/2026		D			6,702	(3)	(3)	Common Stock	6,702	(3)	0	D
Stock Option (right to buy)	$424.5	01/06/2026		D			4,500	(4)	(4)	Common Stock	4,500	(4)	0	D
Stock Option (right to buy)	$157	01/06/2026		D			1,800	(4)	(4)	Common Stock	1,800	(4)	0	D
Stock Option (right to buy)	$151.5	01/06/2026		D			1,527	(4)	(4)	Common Stock	1,527	(4)	0	D
Stock Option (right to buy)	$151.5	01/06/2026		D			4,922	(4)	(4)	Common Stock	4,922	(4)	0	D
Stock Option (right to buy)	$75.5	01/06/2026		D			1,078	(4)	(4)	Common Stock	1,078	(4)	0	D
Stock Option (right to buy)	$75.5	01/06/2026		D			7,921	(4)	(4)	Common Stock	7,921	(4)	0	D
Restricted Stock Units	$0	01/06/2026		D			100	(5)	(5)	Common Stock	100	(5)	0	D
Restricted Stock Units	$0	01/06/2026		D			717	(5)	(5)	Common Stock	717	(5)	0	D
Restricted Stock Units	$0	01/06/2026		D			1,500	(5)	(5)	Common Stock	1,500	(5)	0	D
Restricted Stock Units	$0	01/06/2026		D			2,166	(5)	(5)	Common Stock	2,166	(5)	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.

5. Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each Company restricted stock unit award, which represented the right to receive one share of Common Stock, that was then outstanding was automatically cancelled and converted into the right to receive, without interest and subject to deduction for any required tax withholding, the Offer Price.

	/s/ Alejandra Carvajal	01/06/2026
	** Signature of Reporting Person	Date
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FAQ

What insider activity did this Form 4 report for Mersana Therapeutics (MRSN)?

The Form 4 reports that SVP and Chief Legal Officer Alejandra Carvajal’s Mersana equity holdings, including common stock, stock options, and restricted stock units, were automatically converted or cancelled on January 6, 2026 in connection with the closing of the merger with Day One Biopharmaceuticals.

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

Each Mersana common share tendered was exchanged for $25.00 in cash per share, plus one non-tradeable contingent value right representing the right to receive up to an additional $30.25 in cash per share upon achievement of specified milestones.

How were Mersana stock options treated in the merger described in this Form 4?

In-the-money options with exercise prices below the $25.00 cash amount became fully vested and were cancelled in exchange for the offer price minus the exercise price. Out-of-the-money options with exercise prices at or above $25.00 vested before closing but expired without payment if not exercised by the last exercise date.

What happened to restricted stock units held by the Mersana insider?

Each outstanding restricted stock unit, which represented the right to receive one share of Mersana common stock, was automatically cancelled immediately before the effective time and converted into the right to receive the same cash-and-CVR offer price as a share of common stock.

Did this filing confirm that Mersana Therapeutics is now owned by Day One Biopharmaceuticals?

Yes. The disclosure states that after completion of the tender offer, Emerald Merger Sub merged with and into Mersana, with Mersana continuing as the surviving corporation and a wholly owned subsidiary of Day One Biopharmaceuticals as of January 6, 2026.

Was the insider sale made under a Rule 10b5-1 trading plan for Mersana Therapeutics (MRSN)?

The form includes a checkbox for Rule 10b5-1 plans, but the key transactions reflect automatic conversions and cancellations required by the merger agreement rather than discretionary open-market trades.