# EDGAR Filing Document

**Accession Number:** 0001442836
**File Stem:** 0001104659-26-001368
**Filing Date:** 2026-1
**Character Count:** 10963
**Document Hash:** 240cae2023f51466438d7d6592625839
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-26-001368.hdr.sgml**: 20260106

**ACCESSION NUMBER**: 0001104659-26-001368

**CONFORMED SUBMISSION TYPE**: 4

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20260106

**FILED AS OF DATE**: 20260106

**DATE AS OF CHANGE**: 20260106

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** MOTT DAVID M
- **CENTRAL INDEX KEY:** 0001219871

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 4
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-38129
- **FILM NUMBER:** 26512270

**MAIL ADDRESS:**
- **STREET 1:** 1119 ST. PAUL STREET
- **CITY:** BALTIMORE
- **STATE:** MD
- **ZIP:** 21202
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Mersana Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001442836
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 840 MEMORIAL DRIVE
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139
- **BUSINESS PHONE:** 617-498-0020

**MAIL ADDRESS:**
- **STREET 1:** 840 MEMORIAL DRIVE
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MERSANA THERAPEUTICS INC
- **DATE OF NAME CHANGE:** 20080813

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## FORM 4

### STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

[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**<sup>*</sup><br>MOTT DAVID M<br><sub>(Last) (First) (Middle)</sub><br>C/O MERSANA THERAPEUTICS, INC.<br>840 MEMORIAL DRIVE<br><sub>(Street)</sub><br>CAMBRIDGE, MA 02139<br><sub>(City) (State) (Zip)</sub> | **3. Date of Earliest Transaction (Month/Day/Year)**<br>2026-01-06 | **5. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[X] Director [ ] 10% Owner<br>[ ] Officer (give title below) [ ] Other (specify below)<br>_ _ |
| **2. Issuer Name and Ticker or Trading Symbol**<br>Mersana Therapeutics, Inc. [ MRSN ] | **4. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | 3. Transaction Code (V) | 3. Transaction Code (V) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | Code | V | Amount | (A) or (D) | Price | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| Common Stock | 2026-01-06 |  | U<sup>(1)(2)</sup> |  | 23546 | D | <sup>(1)(2)</sup> | 0 | D |  |
| Common Stock | 2026-01-06 |  | U<sup>(1)(2)</sup> |  | 383 | D | <sup>(1)(2)</sup> | 0 | I | See Footnote<sup>(5)</sup> |

---

## Table II - Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | 4. Transaction Code (V) | 4. Transaction Code (V) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 6. Date Exercisable and Expiration Date | 6. Date Exercisable and Expiration Date | 7. Title and Amount of Underlying Securities | 7. Title and Amount of Underlying Securities | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| Stock Option (right to buy) | $9.0775 | 2026-01-06 |  | D |  |  | 2460 | <sup>(3)</sup> | <sup>(3)</sup> | Common Stock | 2460 | <sup>(3)</sup> | 0 | D |  |
| Stock Option (right to buy) | $434.75 | 2026-01-06 |  | D |  |  | 264 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 264 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $306.75 | 2026-01-06 |  | D |  |  | 400 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 400 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $107.75 | 2026-01-06 |  | D |  |  | 1011 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 1011 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $107.75 | 2026-01-06 |  | D |  |  | 1000 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 1000 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $134.00 | 2026-01-06 |  | D |  |  | 788 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 788 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $572.50 | 2026-01-06 |  | D |  |  | 368 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 368 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $527.25 | 2026-01-06 |  | D |  |  | 181 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 181 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $372.50 | 2026-01-06 |  | D |  |  | 1002 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 1002 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $161.00 | 2026-01-06 |  | D |  |  | 740 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 740 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $90.50 | 2026-01-06 |  | D |  |  | 1800 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 1800 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $216.00 | 2026-01-06 |  | D |  |  | 734 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 734 | <sup>(4)</sup> | 0 | D |  |
| Stock Option (right to buy) | $56.50 | 2026-01-06 |  | D |  |  | 2200 | <sup>(4)</sup> | <sup>(4)</sup> | Common Stock | 2200 | <sup>(4)</sup> | 0 | D |  |

---

### Footnotes:

(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) The securities were held directly by the David Mott Declaration of Trust dated May 31, 2001, as amended (the "Mott Trust"). The Reporting Person disclaims beneficial ownership within the meaning of Section 16 of the Securities Act of 1934, as amended, or otherwise of such portion of the securities held by the Mott Trust in which the Reporting Person has no pecuniary interest.

**Signature:** /s/ David Mott  
**Date:** 2026-01-06

### Remarks:

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

**Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.**