MRSN / Mersana Therapeutics, Inc. - SEC फाइलिंग, वार्षिक रिपोर्ट, प्रॉक्सी स्टेटमेंट

मेर्साना थेरेप्यूटिक्स, इंक.

मूलभूत आँकड़े
LEI 529900VWD5VDZ7PVOS22
CIK 1442836
SEC Filings
All companies that sell securities in the United States must register with the Securities and Exchange Commission (SEC) and file reports on a regular basis. These reports include company annual reports (10K, 10Q), news updates (8K), investor presentations (found in 8Ks), insider trades (form 4), ownership reports (13D, and 13G), and reports related to the specific securities sold, such as registration statements and prospectus. This page shows recent SEC filings related to Mersana Therapeutics, Inc.
SEC Filings (Chronological Order)
यह पृष्ठ SEC फाइलिंग की एक पूरी, कालानुक्रमिक सूची प्रदान करता है, ओनरशिप फाइलिंग को छोड़कर, जो हम अन्यत्र प्रदान करते हैं।
September 5, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 5, 2025 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 5, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

August 13, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 13, 2025 MERSANA THERAPEUT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 13, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commiss

August 13, 2025 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Second Quarter 2025 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Second Quarter 2025 Financial Results · More than 45 patients enrolled in Emi-Le Phase 1 dose expansion cohorts in post-topoisomerase-1 inhibitor ADC (post-topo-1) triple-negative breast cancer (TNBC) · Plan to report initial clinical data from Emi-Le expansion cohorts in second half of 2025 · Conference call today at 8:00 a.

August 13, 2025 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeutics,

August 13, 2025 EX-3.1

Fifth Amended and Restated Certificate of Incorporation, as amended, as of

Exhibit 3.1 FIFTH AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF MERSANA THERAPEUTICS, INC. (Composite document reflecting amendments through July 24, 2025) ARTICLE I — NAME The name of the corporation is Mersana Therapeutics, Inc. (the “Corporation”). ARTICLE II — REGISTERED OFFICE AND AGENT The address of the Corporation’s registered office in the State of Delaware is located at Corporatio

July 24, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 24, 2025 MERSANA THERAPEUTIC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 24, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissio

July 24, 2025 EX-3.1

Certificate of Amendment to Fifth Amended and Restated Certificate of Incorporation, as amended, of Mersana Therapeutics, Inc.

Exhibit 3.1 CERTIFICATE OF AMENDMENT TO FIFTH AMENDED AND RESTATED CERTIFICATE OF INCORPORATION, AS AMENDED OF MERSANA THERAPEUTICS, INC. Pursuant to Section 242 of the General Corporation Law of the State of Delaware Mersana Therapeutics, Inc. (hereinafter called the “Corporation”), a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware, d

July 3, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 1, 2025 MERSANA THERAPEUTICS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 1, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

June 13, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 12, 2025 MERSANA THERAPEUTIC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 12, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissio

June 2, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 2, 2025 MERSANA THERAPEUTICS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 2, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

June 2, 2025 EX-99.1

Mersana Therapeutics Reports Additional Positive Interim Phase 1 Clinical Data for Emi-Le in Oral Presentation at 2025 ASCO Annual Meeting

Exhibit 99.1 Mersana Therapeutics Reports Additional Positive Interim Phase 1 Clinical Data for Emi-Le in Oral Presentation at 2025 ASCO Annual Meeting · 31% confirmed ORR (8 responses in 26 evaluable patients) across B7-H4 high tumors at intermediate doses o 44% confirmed ORR (7 responses in 16 evaluable patients) in the subset of patients with ≤4 prior lines of therapy CAMBRIDGE, Mass., June 2,

May 15, 2025 EX-99.1

Mersana Therapeutics Provides Business Update and Announces First Quarter 2025 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces First Quarter 2025 Financial Results · Updated clinical data from Emi-Le Phase 1 dose escalation and backfill cohorts presented today at ESMO Breast Cancer 2025 o ORR increased to 31% across tumor types among evaluable patients with B7-H4 high tumors receiving intermediate doses o Encouraging preliminary time-to-event data in

May 15, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 15, 2025 MERSANA THERAPEUTICS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 15, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

May 15, 2025 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeutics,

May 6, 2025 EX-99.1

Mersana Therapeutics Announces Strategic Restructuring and Reprioritization Plan Focused on Advancing Emi-Le in Triple-Negative Breast Cancer

Exhibit 99.1 Mersana Therapeutics Announces Strategic Restructuring and Reprioritization Plan Focused on Advancing Emi-Le in Triple-Negative Breast Cancer · Cost-saving initiatives expected to extend company’s cash runway and support current operating plan commitments into mid-2026 · Company to host conference call at 8:00 a.m. ET on May 15 to discuss business updates and first quarter 2025 financ

May 6, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 5, 2025 MERSANA THERAPEUTICS,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 5, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

April 29, 2025 DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant x Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ¨ Defin

April 29, 2025 DEF 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 1

April 18, 2025 PRE 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 1

March 3, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 3, 2025 MERSANA THERAPEUTIC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 3, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissio

March 3, 2025 EX-19

Insider Trading Policy.

Mersana Therapeutics, Inc. Insider Trading Policy (Effective as of June 8, 2023) Policy Principles •Employees, directors, other applicable members of management and designated contractors and consultants (each a “Covered Person,” and collectively, “Covered Persons”) of Mersana Therapeutics, Inc. and its subsidiaries (together, the “Company”) are responsible for understanding the obligations that c

March 3, 2025 EX-10.41

Non-Employee Director Compensation Policy, as amended through December

Mersana Therapeutics, INC. Amended and Restated NON-EMPLOYEE DIRECTOR COMPENSATION POLICY As Amended Through December 4, 2024 Each member of the Board of Directors (the “Board”) of Mersana Therapeutics, Inc. (the “Company”) who is not also serving as an employee of the Company or any of its subsidiaries (each such member, an “Non-Employee Director”) will be eligible to receive the compensation des

March 3, 2025 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024. OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38

March 3, 2025 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2024 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2024 Financial Results · Announced positive initial Phase 1 clinical data and an additional Fast Track designation for Emi-Le · Initiated first expansion cohort in patients with triple-negative breast cancer (TNBC) previously treated with at least one topoisomerase-1 inhibitor (topo-1) ADC · Plan

February 28, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 25, 2025 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 25, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

February 14, 2025 EX-99.1

JOINT FILING AGREEMENT

EX-99.1 2 ex-99-02142025110241.htm JOINT FILING AGREEMENT EXHIBIT 99.1 JOINT FILING AGREEMENT In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a statement on Schedule 13G (including amendments thereto) with respect to the Common Stock of Mersana Therapeutics, Inc. and further agree that th

February 5, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 5, 2025 MERSANA THERAPEU

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 5, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

January 14, 2025 S-8

As filed with the Securities and Exchange Commission on January 14, 2025

As filed with the Securities and Exchange Commission on January 14, 2025 Registration No.

January 14, 2025 EX-FILING FEES

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) Mersana Therapeutics, Inc.

January 10, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 10, 2025 MERSANA THERAPEU

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 10, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

January 10, 2025 EX-99.1

Mersana Therapeutics Announces Positive Initial Clinical Data from Phase 1 Clinical Trial of Emiltatug Ledadotin (XMT-1660); Initiation of Expansion in Triple Negative Breast Cancer

Exhibit 99.1 Mersana Therapeutics Announces Positive Initial Clinical Data from Phase 1 Clinical Trial of Emiltatug Ledadotin (XMT-1660); Initiation of Expansion in Triple Negative Breast Cancer - Emiltatug ledadotin observed to be generally well tolerated with differentiated safety and tolerability profile - Promising clinical activity observed in patients with triple-negative breast cancer (TNBC

January 10, 2025 EX-99.2

Mersana Therapeutics Announces Additional FDA Fast Track Designation Granted to Emiltatug Ledadotin (XMT-1660) Conference call to discuss positive initial Phase 1 clinical data today at 8:30 a.m. ET

Exhibit 99.2 Mersana Therapeutics Announces Additional FDA Fast Track Designation Granted to Emiltatug Ledadotin (XMT-1660) Conference call to discuss positive initial Phase 1 clinical data today at 8:30 a.m. ET CAMBRIDGE, Mass., January 10, 2025 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug

January 10, 2025 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 10, 2025 MERSANA THERAPEU

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 10, 2025 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

January 10, 2025 EX-99.3

Initial Phase 1 Dose Escalation Data for Emi - Le ( emiltatug ledadotin ; XMT - 1660) January 10, 2025

Exhibit 99.3 Initial Phase 1 Dose Escalation Data for Emi - Le ( emiltatug ledadotin ; XMT - 1660) January 10, 2025 Legal Disclaimer 2 This presentation contains “forward - looking” statements and information within the meaning of the Private Securities Litigation Reform Act of 1995 . These statements may be identified by words such as “aims,” “anticipates,” “believes,” “could,” “estimates,” “expe

December 26, 2024 EX-99.1

JOINT FILING AGREEMENT

EXHIBIT 99.1 JOINT FILING AGREEMENT We, the undersigned, hereby express our agreement that the attached Schedule 13G (or any amendments thereto) relating to the Common Stock of Mersana Therapeutics, Inc. is filed on behalf of each of us. Dated: December 26, 2024 Nextech Crossover I SCSp By: Nextech Crossover I GP S.à r.l. its General Partner By: /s/ Ian Charoub Name: Ian Charoub Title: Manager By:

December 23, 2024 EX-99.1 AGREEMENT

AGREEMENT REGARDING JOINT FILING OF STATEMENT ON SCHEDULE 13D OR 13G

EXHIBIT 99.1 AGREEMENT REGARDING JOINT FILING OF STATEMENT ON SCHEDULE 13D OR 13G The undersigned agree to file jointly with the Securities and Exchange Commission (the “SEC”) any and all statements on Schedule 13D or Schedule 13G or Forms 3, 4 or 5(and any amendments or supplements thereto) required under section 13(d) and 16(a) of the Securities Exchange Act of 1934, as amended, in connection wi

December 19, 2024 EX-10.1

Exchange Agreement, dated as of December 19, 2024, by and among Mersana Therapeutics, Inc. and the holders of the common stock listed on Schedule I attached thereto

Exhibit 10.1 December 19, 2024 Mersana Therapeutics, Inc. 840 Memorial Drive Cambridge, MA 02139 Re:         Section 3(a)(9) Exchange Agreement Ladies and Gentlemen: This letter agreement (the “Agreement”) confirms the agreement of Mersana Therapeutics, Inc., a Delaware corporation (the “Company”), and the holders of the Common Stock listed on Schedule I attached hereto (the “Stockholders”), pursu

December 19, 2024 EX-4.1

Form of Pre-Funded Warrants

Exhibit 4.1 MERSANA THERAPEUTICS, INC. FORM OF PRE-FUNDED WARRANTS TO PURCHASE COMMON STOCK Number of Shares: [·] (subject to adjustment) Warrant No. [·] Original Issue Date: December [·], 2024 Mersana Therapeutics, Inc., a Delaware corporation (the “Company”), hereby certifies that, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, [•] or its regis

December 19, 2024 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 19, 2024 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 19, 2024 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

November 15, 2024 SC 13D/A

MRSN / Mersana Therapeutics, Inc. / Bain Capital Life Sciences Fund II, L.P. - SC 13D/A Activist Investment

SC 13D/A 1 d863651dsc13da.htm SC 13D/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13D (Rule 13d-101) Information to be Included in Statements Filed Pursuant to § 240.13d-1(a) and Amendments Thereto Filed Pursuant to § 240.13d-2(a) Under the Securities Exchange Act of 1934 (Amendment No. 6) MERSANA THERAPEUTICS, INC. (Name of Issuer) Common Stock, $0.0001 par val

November 14, 2024 SC 13G/A

MRSN / Mersana Therapeutics, Inc. / BALYASNY ASSET MANAGEMENT LLC - SC 13G/A Passive Investment

SC 13G/A 1 d901805dsc13ga.htm SC 13G/A SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* Mersana Therapeutics Inc (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 59045L106 (CUSIP Number) September 30, 2024 (Date of Event Which Requires Filing of this Statement) Check the appr

November 14, 2024 EX-99.1

JOINT FILING AGREEMENT

EX-99.1 Exhibit 99.1 JOINT FILING AGREEMENT In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the persons named below agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including additional amendments thereto) with respect to the shares of Common Stock, $0.0001 par value per share, of Mersana Therapeutics Inc. This Joint Fil

November 14, 2024 SC 13G/A

MRSN / Mersana Therapeutics, Inc. / Nextech Crossover I GP S.a r.l. - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* Mersana Therapeutics, Inc. (Name of Issuer) Common stock, $0.0001 par value per share (Title of Class of Securities) 59045L106 (CUSIP Number) September 30, 2024 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designat

November 13, 2024 8-K

Regulation FD Disclosure, Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 13, 2024 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

November 13, 2024 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeut

November 13, 2024 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Third Quarter 2024 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Third Quarter 2024 Financial Results - Plan to announce initial clinical data for XMT-1660 at a company event by the end of 2024 - Dose escalation advancing in Phase 1 clinical trial of XMT-2056 - Conference call today at 8:00 a.m. ET CAMBRIDGE, Mass., November 13, 2024 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-

October 15, 2024 SC 13G/A

MRSN / Mersana Therapeutics, Inc. / SILVERARC CAPITAL MANAGEMENT, LLC - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 59045L106 (CUSIP Number) October 11, 2024 (Date of Event which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which th

August 13, 2024 8-K

Regulation FD Disclosure, Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 13, 2024 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commiss

August 13, 2024 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Second Quarter 2024 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Second Quarter 2024 Financial Results - Dose escalation advancing in Phase 1 clinical trials of both XMT-1660 and XMT-2056 - Continue to expect to announce initial XMT-1660 clinical data and initiate expansion in the second half of 2024 - Capital resources expected to support current operating plan commitments into 2026 - Con

August 13, 2024 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeutics,

June 11, 2024 8-K

Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 11, 2024 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissio

May 17, 2024 SC 13G

MRSN / Mersana Therapeutics, Inc. / Nextech Crossover I GP S.a r.l. - SC 13G Passive Investment

SC 13G 1 tm2414799d1sc13g.htm SC 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Mersana Therapeutics, Inc. (Name of Issuer) Common stock, $0.0001 par value per share (Title of Class of Securities) 59045L106 (CUSIP Number) May 14, 2024 (Date of Event Which Requires Filing of this Statement) Check t

May 9, 2024 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeutics,

May 9, 2024 424B5

$100,000,000 Common Stock

TABLE OF CONTENTS  Filed Pursuant to Rule 424(b)(5)  Registration No. 333-271766 PROSPECTUS SUPPLEMENT (To Prospectus Dated May 9, 2024) $100,000,000 Common Stock We previously entered into a sales agreement, or the sales agreement, with Cowen and Company, LLC, or TD Cowen, on February 28, 2024 pursuant to which we may issue and sell, from time to time, shares of our common stock, $0.0001 per shar

May 9, 2024 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 9, 2024 MERSANA THERAPEUTICS,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 9, 2024 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

May 9, 2024 EX-99.1

Mersana Therapeutics Provides Business Update and Announces First Quarter 2024 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces First Quarter 2024 Financial Results - Maximum tolerated dose not yet established in Phase 1 clinical trial of XMT-1660; enrollment in dose escalation and backfill cohorts continuing in parallel; expect to announce initial clinical data and initiate expansion in the second half of 2024 - Patient recruitment ongoing in Phase 1

April 26, 2024 DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant x Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ¨ Defin

April 26, 2024 DEF 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 1

February 28, 2024 POSASR

As filed with the Securities and Exchange Commission on February 28, 2024

TABLE OF CONTENTS As filed with the Securities and Exchange Commission on February 28, 2024 Registration No.

February 28, 2024 EX-FILING FEES

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Post-Effective Amendment No. 1 to Form S-3 (Form Type) Mersana Therapeutics, Inc. (Exact Name of Registrant as Specified in its Charter) Table 1—Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price

February 28, 2024 EX-97

Amended and Restated

Exhibit 97 Effective October 2, 2023 MERSANA THERAPEUTICS, INC. Amended and Restated Clawback Policy This Amended and Restated Clawback Policy (this “Policy”) is adopted by Mersana Therapeutics, Inc. (the “Company”) in accordance with Nasdaq Listing Rule 5608 (“Rule 5608”), which implements Rule 10D-1 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”) (as promulgated pursua

February 28, 2024 POS AM

As filed with the Securities and Exchange Commission on February 28, 2024

TABLE OF CONTENTS As filed with the Securities and Exchange Commission on February 28, 2024 Registration No.

February 28, 2024 EX-10.24

, 2021, between Mersana Therapeutics, Inc. and

Exhibit 10.24 July 20, 2021 VIA E-MAIL Mersana Therapeutics, Inc. 840 Memorial Dr. Cambridge, MA 02139 Mohan Bala, Ph.D. c/o Mersana Therapeutics, Inc. 840 Memorial Drive Cambridge, MA 02139 Dear Mohan, I am pleased to offer you the position of SVP, Strategic Product Planning & Program Leadership of Mersana Therapeutics, Inc. (the “Company”), and present you with the terms and conditions of your e

February 28, 2024 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 28, 2024 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 28, 2024 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

February 28, 2024 EX-10.43

Non-Employee Director Compensation Policy,

Exhibit 10.43 Mersana Therapeutics, INC. Amended and Restated NON-EMPLOYEE DIRECTOR COMPENSATION POLICY As Amended Through December 15, 2023 Each member of the Board of Directors (the “Board”) of Mersana Therapeutics, Inc. (the “Company”) who is not also serving as an employee of the Company or any of its subsidiaries (each such member, an “Non-Employee Director”) will be eligible to receive the c

February 28, 2024 EX-1.1

(incorporated by reference to Exhibit 1.1 to the Current Report on Form 8-K (File No. 001-38129) filed with the S

Exhibit 1.1 Execution Version MERSANA THERAPEUTICS, INC. $100,000,000 common stock SALES AGREEMENT February 28, 2024 Cowen and Company, LLC 599 Lexington Avenue New York, NY 10022 Ladies and Gentlemen: Mersana Therapeutics, Inc., a Delaware Corporation (the “Company”), confirms its agreement (this “Agreement”) with Cowen and Company, LLC (“Cowen”), as follows: 1.              Issuance and Sale of

February 28, 2024 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 28, 2024 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 28, 2024 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

February 28, 2024 424B5

$100,000,000 Common Stock

TABLE OF CONTENTS   Filed Pursuant to Rule 424(b)(5)   Registration No. 333-271766 PROSPECTUS SUPPLEMENT (To Prospectus Dated February 28, 2024) $100,000,000 Common Stock We entered into a sales agreement, or the sales agreement, with Cowen and Company, LLC, or TD Cowen, on February 28, 2024 pursuant to which we may issue and sell, from time to time, shares of our common stock, $0.0001 per share,

February 28, 2024 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2023 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2023 Financial Results · Enrollment in dose escalation and backfill cohorts continuing in Phase 1 clinical trial of XMT-1660; expect to initiate tumor-specific expansion cohorts in the second quarter of 2024 and announce initial clinical data in mid-2024 · Phase 1 clinical trial of XMT-2056 restar

February 28, 2024 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023. OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38

February 14, 2024 SC 13G/A

MRSN / Mersana Therapeutics, Inc. / Venrock Healthcare Capital Partners III, L.P. - SC 13G/A Passive Investment

SC 13G/A 1 tm246235d18sc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1)* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 59045L106 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of this State

February 14, 2024 SC 13G/A

MRSN / Mersana Therapeutics, Inc. / Avoro Capital Advisors LLC - MERSANA THERAPEUTICS, INC. Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 2)* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 59045L106 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of This Statement) Check the appropriate box to designate the rule pu

February 14, 2024 SC 13G

MRSN / Mersana Therapeutics, Inc. / BALYASNY ASSET MANAGEMENT LLC - SC 13G Passive Investment

SC 13G SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 Mersana Therapeutics Inc (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 59045L106 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which

February 14, 2024 SC 13G/A

MRSN / Mersana Therapeutics, Inc. / ORBIMED ADVISORS LLC - AMENDMENT NO. 1 Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No.

February 14, 2024 EX-99.A

JOINT FILING AGREEMENT

EX-99.A 2 ss3005734ex99a.htm JOINT FILING AGREEMENT EXHIBIT A JOINT FILING AGREEMENT The undersigned hereby agree that this Amendment No. 1 to the Statement on Schedule 13G, dated December 31, 2023 (this “Schedule 13G”), with respect to the Common Stock, $0.0001 par value per share, of Mersana Therapeutics, Inc. is filed on behalf of each of us pursuant to and in accordance with the provisions of

February 14, 2024 EX-99.1

JOINT FILING AGREEMENT

EX-99.1 2 d753345dex991.htm EX-99.1 Exhibit 99.1 JOINT FILING AGREEMENT In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the persons named below agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including additional amendments thereto) with respect to the shares of Common Stock, $0.0001 par value per share, of Mersana Ther

February 14, 2024 SC 13G

MRSN / Mersana Therapeutics, Inc. / SILVERARC CAPITAL MANAGEMENT, LLC - SCHEDULE FILED TO REPORT ACQUISITION OF BENEFICIAL OWNERSHIP Passive Investment

SC 13G 1 mrsn-sc13g123123.htm SCHEDULE FILED TO REPORT ACQUISITION OF BENEFICIAL OWNERSHIP UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 59045L106 (CUSIP Number) December 31, 2023 (Date of Event which Requires Fil

February 14, 2024 EX-99.(A)

Joint Filing Agreement

EX-99.(A) 2 ex99-a.htm JOINT FILING AGREEMENT SilverArc Capital Management, LLC 13G EXHIBIT A JOINT FILING AGREEMENT The undersigned hereby agree that the statement on Schedule 13G with respect to the common stock of Mersana Therapeutics, Inc., dated as of February 14, 2024, is, and any amendments thereto (including amendments on Schedule 13D) signed by each of the undersigned shall be, filed on b

February 13, 2024 SC 13G

MRSN / Mersana Therapeutics, Inc. / VANGUARD GROUP INC - SCHEDULE 13G Passive Investment

SC 13G 1 tv01443-mersanatherapeuticsi.htm SCHEDULE 13G SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 Name of issuer: Mersana Therapeutics Inc Title of Class of Securities: Common Stock CUSIP Number: 59045L106 Date of Event Which Requires Filing of this Statement: December 29, 2023 Check the appropriate box to designate the rule pur

January 12, 2024 EX-FILING FEES

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) Mersana Therapeutics, Inc.

January 12, 2024 S-8

As filed with the Securities and Exchange Commission on January 12, 2024

As filed with the Securities and Exchange Commission on January 12, 2024 Registration No.

January 5, 2024 EX-99.1

Mersana Therapeutics Announces Business Updates, Expected 2024 Milestones and Upcoming Presentation at the 42nd Annual J.P. Morgan Healthcare Conference

Exhibit 99.1 Mersana Therapeutics Announces Business Updates, Expected 2024 Milestones and Upcoming Presentation at the 42nd Annual J.P. Morgan Healthcare Conference · Enrollment in dose escalation and backfill cohorts continuing in Phase 1 clinical trial of XMT-1660, Dolasynthen B7-H4 ADC; expect to initiate expansion in Q2 2024 and announce initial clinical data in mid-2024 · Phase 1 clinical tr

January 5, 2024 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 5, 2024 MERSANA THERAPEUT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 5, 2024 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commiss

December 21, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 15, 2023 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 15, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

November 7, 2023 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeut

November 7, 2023 EX-10.2

Amendment No. 2 to the Research Collaboration and License Agreement (effective February 2, 2022), dated

Exhibit 10.2 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. Execution Copy AMENDMENT NO. 2 TO RESEARCH COLLABORATION AND LICENSE AGREEMENT This Amendment No. 2 to Research Collaboration and License Agreement (this “Amen

November 7, 2023 EX-10.4

etter, dated September 5, 2023, by and between Mersana Therape

Exhibit 10.4 Mersana Therapeutics, Inc. 840 Memorial Dr. Cambridge, MA 02139 September 5, 2023 VIA Electronic Delivery Martin Huber, M.D. Dear Marty: I am pleased to offer you the position of President and Chief Executive Officer (“CEO”) of Mersana Therapeutics, Inc. (the “Company”), and present you with the terms and conditions of your employment by the Company, as set forth in this letter agreem

November 7, 2023 EX-10.5

, 2023, by and between Mersana Therapeutics

Exhibit 10.5 VIA ELECTRONIC MAIL September 6, 2023 Arvin Yang Dear Arvin: As we discussed, your employment with Mersana Therapeutics, Inc. (the “Company”) will end effective September 29, 2023 (the “Separation Date”). As we also discussed, the Company will provide you with the severance benefits described in paragraph 1 below if you sign and return this letter agreement to me on, but not before, t

November 7, 2023 EX-10.1

Amendment No. 1 to the Research Collaboration and License Agreement (effective February 2, 2022), dated July 14, 2023, by and between Mersana Therapeutics, Inc. and Janssen Biotech, Inc.

Exhibit 10.1 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. CONFIDENTIAL AMENDMENT NO. 1 to the RESEARCH COLLABORATION AND LICENSE AGREEMENT by and between MERSANA THERAPEUTICS, INC. and JANSSEN BIOTECH, INC. (effective

November 7, 2023 EX-10.3

Retirement and Separation Agreement, dated September 5, 2023, by and between Mersana Therapeutics, Inc. and Anna Protopapas (incorporated by reference to Exhibit 10.3 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on November 7, 2023).

Exhibit 10.3 EXECUTION COPY RETIREMENT AND SEPARATION AGREEMENT This Retirement and Separation Agreement (the “Agreement”) is made as of September 5, 2023 (the “Agreement Effective Date”) by and between Anna Protopapas (the “Executive”) and Mersana Therapeutics, Inc. (“Mersana” or the “Company”) (together, the “Parties”). WHEREAS, the Company and Executive are parties to that certain amended and r

November 7, 2023 8-K

Regulation FD Disclosure, Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 7, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

November 7, 2023 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Third Quarter 2023 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Third Quarter 2023 Financial Results · Advancing dose escalation portion of Phase 1 clinical trial of XMT-1660, Mersana’s B7-H4 Dolasynthen ADC · Preparations underway to resume enrollment in Phase 1 clinical trial of XMT-2056, Mersana’s HER2 Immunosynthen ADC · Capital resources expected to support current operating plan com

October 31, 2023 8-K

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 31, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

October 31, 2023 EX-99.1

Mersana Therapeutics Announces FDA has Lifted Clinical Hold on Phase 1 Clinical Trial of XMT-2056

Exhibit 99.1 Mersana Therapeutics Announces FDA has Lifted Clinical Hold on Phase 1 Clinical Trial of XMT-2056 CAMBRIDGE, Mass., October 31, 2023 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet medical need, today announced that the U.

September 12, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 12, 2023 MERSANA THERAP

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 12, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Comm

September 6, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 1, 2023 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 1, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

August 8, 2023 EX-99.1

Mersana Therapeutics Announces Second Quarter 2023 Financial Results

Exhibit 99.1 Mersana Therapeutics Announces Second Quarter 2023 Financial Results · Organization fully focused on product candidates and collaborations based on next-generation ADC platforms · Capital resources expected to support current operating plan commitments into 2026 CAMBRIDGE, Mass., August 8, 2023 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company foc

August 8, 2023 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 8, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissi

August 8, 2023 EX-10.2

Form of Restricted Stock Unit Agreement for Employees under the Mersana Therapeutics, Inc. 2017 Stock Incentive Plan (incorporated by reference to Exhibit 10.2 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on August 8, 2023).

Exhibit 10.2 Name: [●] Number of RSUs: [●] Date of Grant: [●] Vesting Commencement Date [●] MERSANA THERAPEUTICS, INC. 2017 STOCK INCENTIVE PLAN RESTRICTED STOCK UNIT AGREEMENT This agreement (this “Agreement”) evidences a grant of restricted stock units (“RSUs”) by Mersana Therapeutics, Inc. (the “Company”) to the individual named above (the “Grantee”), an employee of the Company, pursuant to and

August 8, 2023 EX-10.1

Form of Restricted Stock Unit Agreement under the Mersana Therapeutics, Inc. 2022 Inducement Stock Incentive Plan (incorporated by reference to Exhibit 10.1 to the Quarterly Report on Form 10-Q (File No. 001-23819) filed with the SEC on August 8, 2023).

Exhibit 10.1 Name: [●] Number of RSUs: [●] Date of Grant: [●] Vesting Commencement Date [●] MERSANA THERAPEUTICS, INC. 2022 INDUCEMENT STOCK INCENTIVE PLAN RESTRICTED STOCK UNIT AGREEMENT This agreement (this “Agreement”) evidences a grant of restricted stock units (“RSUs”) by Mersana Therapeutics, Inc. (the “Company”) to the individual named above (the “Grantee”), pursuant to and subject to the t

August 8, 2023 EX-10.3

Form of Restricted Stock Unit Agreement for Non-Employee Directors under the Mersana Therapeutics, Inc. 2017 Stock Incentive Plan (incorporated by reference to Exhibit 10.3 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on August 8, 2023).

Exhibit 10.3 Form of RSU Award Agreement for Non-Employee Directors Name: [●] Number of RSUs: [●] Date of Grant: [●] Vesting Commencement Date [●] MERSANA THERAPEUTICS, INC. 2017 STOCK INCENTIVE PLAN RESTRICTED STOCK UNIT AGREEMENT This agreement (this “Agreement”) evidences a grant of restricted stock units (“RSUs”) by Mersana Therapeutics, Inc. (the “Company”) to the individual named above (the

August 8, 2023 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeutics,

August 7, 2023 SC 13G

MRSN / Mersana Therapeutics Inc / Venrock Healthcare Capital Partners III, L.P. - SC 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 59045L106 (CUSIP Number) July 28, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the

July 27, 2023 EX-99.1

Mersana Therapeutics Announces Topline Data from UPLIFT Clinical Trial in Patients with Platinum-Resistant Ovarian Cancer and Strategic Reprioritization

Exhibit 99.1 Mersana Therapeutics Announces Topline Data from UPLIFT Clinical Trial in Patients with Platinum-Resistant Ovarian Cancer and Strategic Reprioritization - UPLIFT clinical trial did not meet its primary endpoint - Company realigns focus and significantly reduces expenses to extend cash runway into 2026 - Conference call today at 8:00 a.m. ET Cambridge, Mass., July 27, 2023 – Mersana Th

July 27, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 26, 2023 MERSANA THERAPEUTIC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 26, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissio

July 27, 2023 SC 13G

MRSN / Mersana Therapeutics Inc / EcoR1 Capital, LLC Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. ) Mersana Therapeutics, Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 59045L106 (CUSIP Number) July 27, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the r

June 15, 2023 EX-99.1

Mersana Therapeutics Announces Partial Clinical Hold on UP-NEXT and UPGRADE-A Clinical Trials UPLIFT top-line data expected by early August

Exhibit 99.1 Mersana Therapeutics Announces Partial Clinical Hold on UP-NEXT and UPGRADE-A Clinical Trials UPLIFT top-line data expected by early August CAMBRIDGE, Mass., June 15, 2023 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet me

June 15, 2023 8-K

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 15, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissio

June 9, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 8, 2023 MERSANA THERAPEUTICS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 8, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

June 9, 2023 EX-3.1

Fifth Amended and Restated Certificate of Incorporation, as amended, as of June 8, 2023 (incorporated by reference to Exhibit 3.1 to the Company's Current Report on Form 8-K filed with the SEC on June 9, 2023).

Exhibit 3.1 FIFTH AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF MERSANA THERAPEUTICS, INC. (Composite document reflecting amendments through June 8, 2023) ARTICLE I — NAME The name of the corporation is Mersana Therapeutics, Inc. (the “Corporation”). ARTICLE II — REGISTERED OFFICE AND AGENT The address of the Corporation’s registered office in the State of Delaware is located at Corporation

May 9, 2023 EX-99.1

Mersana Therapeutics Provides Business Update and Announces First Quarter 2023 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces First Quarter 2023 Financial Results - Initiated dose expansion portion of UPGRADE-A clinical trial of UpRi in combination with carboplatin; interim data expected in second half of 2023 - Advanced enrollment in Phase 3 UP-NEXT clinical trial of UpRi and Phase 1 clinical trial of XMT-1660 - Plan to report topline data from UPL

May 9, 2023 EX-10.5

Amendment 3 to the Collaboration and Commercial License Agreement, dated February 28, 2017, by and between Mersana Therapeutics, Inc. and Merck KGaA.

Exhibit 10.5 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. AMENDMENT 3 TO COLLABORATION AND COMMERCIAL LICENSE AGREEMENT This Amendment 3 to Collaboration and Commercial License Agreement (“Amendment 3”) is entered int

May 9, 2023 EX-10.2

Collaboration and Commercial License Agreement, dated June 23, 2014, by and between Mersana Therapeutics, Inc. and Merck KGaA.

Exhibit 10.2 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. COLLABORATION AND COMMERCIAL LICENSE AGREEMENT between MERSANA THERAPEUTICS, INC. and MERCK KGaA TABLE OF CONTENTS 1. Definitions and Interpretation 1 1.1. Def

May 9, 2023 8-K

Regulation FD Disclosure, Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 9, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

May 9, 2023 EX-10.1

Fourth Amendment to Loan and Security Agreement, dated March 23, 2023, between Oxford Finance LLC, the Lenders named therein including Silicon Valley Bridge Bank, N.A., and Mersana Therapeutics, Inc.

Exhibit 10.1 FOURTH AMENDMENT TO LOAN AND SECURITY AGREEMENT THIS FOURTH AMENDMENT TO LOAN AND SECURITY AGREEMENT (this “Amendment”) is entered into as of March 23, 2023, by and among OXFORD FINANCE LLC, a Delaware limited liability company with an office located at 115 South Union Street, Suite 300, Alexandria, Virginia 22314 (“Oxford”), as collateral agent (in such capacity, “Collateral Agent”),

May 9, 2023 S-3ASR

As filed with the Securities and Exchange Commission on May 9, 2023

TABLE OF CONTENTS As filed with the Securities and Exchange Commission on May 9, 2023 Registration No.

May 9, 2023 EX-10.4

Amendment 2 to the Collaboration and Commercial License Agreement, dated August 12, 2016, by and between Mersana Therapeutics, Inc. and Merck KGaA.

Exhibit 10.4 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. AMENDMENT 2 TO COLLABORATION AND COMMERCIAL LICENSE AGREEMENT This Amendment 2 to Collaboration and Commercial License Agreement (“Amendment”) is entered into

May 9, 2023 EX-10.6

License, Development and Commercialization Agreement, dated July 9, 2015, by and between Mersana Therapeutics, Inc. and Recepta Biopharma S.A.

Exhibit 10.6 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. LICENSE, DEVELOPMENT AND COMMERCIALIZATION AGREEMENT between MERSANA THERAPEUTICS, INC. and RECEPTA BIOPHARMA S.A. TABLE OF CONTENTS Page 1. DEFINITIONS 1 2. L

May 9, 2023 EX-10.3

Amendment 1 to the Collaboration and Commercial License Agreement, dated June 1, 2016, by and between Mersana Therapeutics, Inc. and Merck KGaA.

Exhibit 10.3 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. AMENDMENT 1 TO COLLABORATION AND COMMERCIAL LICENSE AGREEMENT This Amendment 1 to Collaboration and Commercial License Agreement (“Amendment”) is entered into

May 9, 2023 EX-FILING FEES

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) Mersana Therapeutics, Inc.

May 9, 2023 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeutics,

May 9, 2023 EX-10.7

Agreement Regarding LICR Technology, dated July 9, 2015, by and between Ludwig Institute for Cancer Research, Recepta Biopharma S.A. and Mersana Therapeutics, Inc.

Exhibit 10.7 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. EXECUTION VERSION AGREEMENT REGARDING LICR TECHNOLOGY This Agreement Regarding LICR Technology (“Agreement”), effective as of July 9, 2015, is by and between L

April 28, 2023 DEF 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

DEF 14A 1 tm231888-2def14a.htm DEF 14A TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the

April 28, 2023 DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  ) Filed by the Registrant x Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ¨ Defi

April 14, 2023 PRE 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 1

March 31, 2023 EX-3.1

Second Amended and Restated Bylaws (incorporated by reference to Exhibit 3.1 to the Company’s Current Report on Form 8-K filed with the SEC on March 31, 2023).

Exhibit 3.1 MERSANA THERAPEUTICS, INC. SECOND AMENDED AND RESTATED BYLAWS (Adopted March 31, 2023) SECTION 1 - STOCKHOLDERS Section 1.1. Annual Meeting. An annual meeting of the stockholders of Mersana Therapeutics, Inc., a Delaware corporation (the “Corporation”), for the election of directors to succeed those whose terms expire and for the transaction of such other business as may properly come

March 31, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 31, 2023 MERSANA THERAPEUTI

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 31, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissi

March 24, 2023 8-K

Entry into a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 23, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissi

March 13, 2023 EX-99.2

Mersana Therapeutics Announces Clinical Hold on XMT-2056 Phase 1 Clinical Trial

Exhibit 99.2 Mersana Therapeutics Announces Clinical Hold on XMT-2056 Phase 1 Clinical Trial CAMBRIDGE, Mass., March 13, 2023 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet medical need, today announced that the Phase 1 trial of XMT-2

March 13, 2023 8-K

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 10, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissi

March 13, 2023 EX-99.1

Mersana Therapeutics Provides Statement About SVB

Exhibit 99.1 Mersana Therapeutics Provides Statement About SVB CAMBRIDGE, Mass., March 10, 2023 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet medical need, today provided an update about its capital resources. A de minimis amount of

February 28, 2023 EX-10.42

Non-Employee Director Compensation Policy, effective as of December 1, 2022.

Exhibit 10.42 Mersana Therapeutics, INC. AMENDED AND RESTATED NON-EMPLOYEE DIRECTOR COMPENSATION POLICY Each member of the Board of Directors (the “Board”) of Mersana Therapeutics, Inc. (the “Company”) who is not also serving as an employee of the Company or any of its subsidiaries (each such member, an “Non-Employee Director”) will be eligible to receive the compensation described in this Amended

February 28, 2023 EX-21.1

(incorporated by reference to Exhibit 21.1 to t

Exhibit 21.1 Subsidiaries of the Registrant Entity State of Incorporation or Organization Mersana Securities Corp. Massachusetts

February 28, 2023 EX-4.3

Exhibit 4.3

Exhibit 4.3 DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 The following description summarizes selected information regarding our capital stock, as well as relevant provisions of: (i) our fifth amended and restated certificate of incorporation, as amended, or the Restated Certificate, (ii) our amended and restated bylaws, or Byl

February 28, 2023 EX-97

Clawback Policy

Exhibit 97 MERSANA THERAPEUTICS, INC. Clawback Policy 1. Persons Subject to this Policy. This policy is applicable to all officers (as defined in Rule 16(a)-f under the Securities Exchange Act of 1934, as amended) of Mersana Therapeutics, Inc. (the “Company”). This policy will also apply to such other employees, or classes of employees, of the Company as may be determined from time to time by the

February 28, 2023 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2022 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Fourth Quarter and Full Year 2022 Financial Results - Commenced dose expansion portion of Phase 1 UPGRADE-A clinical trial of UpRi in combination with carboplatin - Initiated patient dosing in Phase 1 clinical trial of lead Immunosynthen ADC candidate, XMT-2056 - Entered new research collaboration and commercial license agree

February 28, 2023 EX-10.22

Third Amendment to Loan and Security Agreement, dated December 27, 2022, between Oxford Finance LLC, the Lenders named therein including Silicon Valley Bank, and Mersana Therapeutics, Inc.

Exhibit 10.22 THIRD AMENDMENT TO LOAN AND SECURITY AGREEMENT THIS THIRD AMENDMENT TO LOAN AND SECURITY AGREEMENT (this “Amendment”) is entered into as of December 27, 2022, by and among OXFORD FINANCE LLC, a Delaware limited liability company with an office located at 115 South Union Street, Suite 300, Alexandria, Virginia 22314 (“Oxford”), as collateral agent (in such capacity, “Collateral Agent”

February 28, 2023 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2022. OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38

February 28, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 28, 2023 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 28, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

February 28, 2023 S-8

As filed with the Securities and Exchange Commission on February 28, 2023

As filed with the Securities and Exchange Commission on February 28, 2023 Registration No.

February 28, 2023 EX-FILING FEES

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) Mersana Therapeutics, Inc.

February 28, 2023 EX-10.40

Mersana Therapeutics, Inc. 2017 Employee Stock Purchase Plan, as amended (incorporated by reference to Exhibit 10.40 to the Annual Report on Form 10-K (File No. 001-38129) filed with the SEC on February 28, 2023).

Exhibit 10.40 MERSANA THERAPEUTICS, INC. 2017 EMPLOYEE STOCK PURCHASE PLAN (AS AMENDED THROUGH JANUARY 23, 2019) 1. DEFINED TERMS The following terms, when used in the Plan (as defined below), have the meanings and are subject to the provisions set forth below: (a) “401(k) Plan”: A savings plan qualifying under Section 401(k) of the Code that is sponsored by the Company for the benefit of its empl

February 28, 2023 EX-10.21

Second Amendment to Loan and Security Agreement, dated October 17, 2022, between Oxford Finance LLC, the Lenders named therein including Silicon Valley Bank, and Mersana Therapeutics, Inc.

Exhibit 10.21 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. SECOND AMENDMENT TO LOAN AND SECURITY AGREEMENT THIS SECOND AMENDMENT TO LOAN AND SECURITY AGREEMENT (this “Amendment”) is entered into as of October 17, 2022

February 28, 2023 EX-10.18

Collaboration and Commercial License Agreement, dated December 22, 2022, between Mersana Therapeutics, Inc. and Ares Trading S.A.

Exhibit 10.18 CONFIDENTIAL Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. COLLABORATION AND COMMERCIAL LICENSE AGREEMENT between MERSANA THERAPEUTICS, INC. and ARES TRADING S.A. Table of Contents Background 1 Article 1

February 14, 2023 EX-99.A

JOINT FILING AGREEMENT

EXHIBIT A JOINT FILING AGREEMENT The undersigned hereby agree that the Statement on this Schedule 13G dated December 31, 2022 (the “Schedule 13G”), with respect to the Common Stock, $0.

February 14, 2023 SC 13G/A

MRSN / Mersana Therapeutics Inc / Rho Ventures V, L.P. Passive Investment

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No.

February 14, 2023 SC 13G

MRSN / Mersana Therapeutics Inc / ORBIMED ADVISORS LLC - SCHEDULE 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 Mersana Therapeutics, Inc.

February 14, 2023 SC 13G/A

MRSN / Mersana Therapeutics Inc / BB BIOTECH AG - SC 13G/A Passive Investment

SC 13G/A United States SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock, $0.0001 par value (Title of Class of Securities) 59045L106 (CUSIP Number) December 31, 2022 (Date of Event Which Requires Filing This Statement) Check the appropriate box to designate the

February 14, 2023 EX-99.B

POWER OF ATTORNEY

EX-99.B Exhibit B POWER OF ATTORNEY The Undersigned, Hugo van Neutegem herewith gives Power of Attorney to Mrs. Nathalie M.A. Isidora-Kwidama, born in Curacao on, holder of a passport issued by the Kingdom of the Netherlands, with number, to represent the Company in the broadest sense of the word and in the best interest of the Company and further to do if were the Undersigned personally present.

February 14, 2023 SC 13G/A

MRSN / Mersana Therapeutics Inc / Avoro Capital Advisors LLC - MERSANA THERAPEUTICS, INC. Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1)* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 59045L106 (CUSIP Number) December 31, 2022 (Date of Event Which Requires Filing of This Statement) Check the appropriate box to designate the rule pu

February 9, 2023 SC 13G/A

MRSN / Mersana Therapeutics Inc / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 1)* Name of issuer: Mersana Therapeutics Inc. Title of Class of Securities: Common Stock CUSIP Number: 59045L106 Date of Event Which Requires Filing of this Statement: December 30, 2022 Check the appropriate box to designate the rule pursuant to which this Schedule is fi

February 6, 2023 SC 13G/A

MRSN / Mersana Therapeutics Inc / WELLINGTON MANAGEMENT GROUP LLP - SEC SCHEDULE 13G Passive Investment

SC 13G/A 1 SEC13GFiling.htm SEC SCHEDULE 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 2 )* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 59045L106 (CUSIP Number) December 30, 2022 (Date of Event Which Requires Filing of this Statement) Check the appropriate

February 1, 2023 EX-99.1

Mersana Therapeutics Initiates Expansion Portion of UPGRADE-A Combination Clinical Trial in Platinum-Sensitive Ovarian Cancer Company plans to report interim data for the combination of UpRi with carboplatin in the second half of 2023

Exhibit 99.1 Mersana Therapeutics Initiates Expansion Portion of UPGRADE-A Combination Clinical Trial in Platinum-Sensitive Ovarian Cancer Company plans to report interim data for the combination of UpRi with carboplatin in the second half of 2023 CAMBRIDGE, Mass., February 1, 2023 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and de

February 1, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 1, 2023 MERSANA THERAPEU

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 1, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

January 25, 2023 EX-99.1

Mersana Therapeutics Announces Initiation of Phase 1 Trial of XMT-2056 in HER2-Expressing Tumors First Immunosynthen ADC product candidate enters the clinic

Exhibit 99.1 Mersana Therapeutics Announces Initiation of Phase 1 Trial of XMT-2056 in HER2-Expressing Tumors First Immunosynthen ADC product candidate enters the clinic CAMBRIDGE, Mass., January 25, 2023 – Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in ar

January 25, 2023 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 25, 2023 MERSANA THERAPEU

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 25, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

January 19, 2023 SC 13G/A

MRSN / Mersana Therapeutics Inc / MILLENNIUM MANAGEMENT LLC Passive Investment

SC 13G/A 1 MRSNSC13GA12023.htm UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (AMENDMENT NO. 1) MERSANA THERAPEUTICS, INC. (Name of Issuer) COMMON STOCK, PAR VALUE $0.0001 PER SHARE (Title of Class of Securities) 59045L106 (CUSIP Number) DECEMBER 31, 2022 (Date of event which requires filing of this statement) Check th

January 6, 2023 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Strategic Objectives and Expected Milestones

EX-99.1 2 tm232318d1ex99-1.htm EXHIBIT 99.1 Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Strategic Objectives and Expected Milestones - Report top-line data from UPLIFT registrational trial in mid-2023, submit potential BLA around year end 2023, and prepare for potential U.S. commercial launch in 2024 - Advance Phase 3 UP-NEXT and Phase 1 UPGRADE-A trials in platinum-se

January 6, 2023 8-K

Regulation FD Disclosure, Financial Statements and Exhibits, Results of Operations and Financial Condition, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 6, 2023 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commiss

December 27, 2022 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 27, 2022 MERSANA THERAPE

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 27, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

December 22, 2022 8-K

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 22, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

December 22, 2022 EX-99.1

Mersana Therapeutics Announces Research Collaboration and Commercial License Agreement with Merck KGaA, Darmstadt, Germany to Develop Novel Immunosynthen Antibody-Drug Conjugates

Exhibit 99.1 Mersana Therapeutics Announces Research Collaboration and Commercial License Agreement with Merck KGaA, Darmstadt, Germany to Develop Novel Immunosynthen Antibody-Drug Conjugates - Collaboration focuses on discovering novel STING-agonist ADCs for up to two targets leveraging Mersana?s proprietary immunostimulatory platform - Mersana to receive $30 million upfront payment, up to $800 m

November 7, 2022 EX-10.1

Collaboration, Option and License Agreement, dated August 6, 2022, between Mersana Therapeutics, Inc. and GlaxoSmithKline Intellectual Property (No. 4) Limited (incorporated by reference to Exhibit 10.1 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on November 7, 2022).

Exhibit 10.1 EXECUTION VERSION Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. COLLABORATION, OPTION AND LICENSE AGREEMENT Between GLAXOSMITHKLINE INTELLECTUAL PROPERTY (NO. 4) LIMITED And MERSANA THERAPEUTICS, INC. AUGU

November 7, 2022 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeut

November 7, 2022 424B5

$150,000,000 Common Stock

TABLE OF CONTENTS  Filed Pursuant to Rule 424(b)(5)  Registration No. 333-260895 PROSPECTUS SUPPLEMENT (To Prospectus Dated November 18, 2021) $150,000,000 Common Stock We entered into a sales agreement, or the sales agreement, with Cowen and Company, LLC, or Cowen, on November 7, 2022 pursuant to which we may issue and sell, from time to time, shares of our common stock, $0.0001 per share, having

November 7, 2022 8-K

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 7, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

November 7, 2022 EX-1.1

Sales Agreement, dated November 7, 2022, between Mersana Therapeutics, Inc. and Cowen and Company, LLC (incorporated by reference to Exhibit 1.1 to the Current Report on Form 8-K (File No. 001-38129) filed with the SEC on November 7, 2022).

EX-1.1 2 tm2229816d1ex1-1.htm EXHIBIT 1.1 Exhibit 1.1 Execution Version MERSANA THERAPEUTICS, INC. $150,000,000 common stock SALES AGREEMENT November 7, 2022 Cowen and Company, LLC 599 Lexington Avenue New York, NY 10022 Ladies and Gentlemen: Mersana Therapeutics, Inc. (the “Company”), confirms its agreement (this “Agreement”) with Cowen and Company, LLC (“Cowen”), as follows: 1. Issuance and Sale

November 7, 2022 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 7, 2022 MERSANA THERAPEU

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 7, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

November 7, 2022 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Third Quarter 2022 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Third Quarter 2022 Financial Results - Completed enrollment in UPLIFT clinical trial; topline data expected mid-2023; potential Biologics License Application (BLA) submission anticipated by the end of 2023 - Initiated patient enrollment and dosing in Phase 1 clinical trial of XMT-1660 - Strengthened balance sheet with $100 mi

October 6, 2022 EX-99.1

Mersana Therapeutics Announces Completion of Enrollment in UPLIFT, a Single-Arm Registrational Trial of Upifitamab Rilsodotin (UpRi) in Platinum-Resistant Ovarian Cancer

Exhibit 99.1 Mersana Therapeutics Announces Completion of Enrollment in UPLIFT, a Single-Arm Registrational Trial of Upifitamab Rilsodotin (UpRi) in Platinum-Resistant Ovarian Cancer - Topline data from UPLIFT expected in mid-2023 - Targeting potential Biologics License Application (BLA) submission by the end of 2023 CAMBRIDGE, Mass., October 6, 2022 ? Mersana Therapeutics, Inc. (NASDAQ: MRSN), a

October 6, 2022 8-K

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 6, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commiss

August 16, 2022 EX-99.1

Mersana Therapeutics Announces Initiation of Phase 1 Trial of XMT-1660 in Breast, Endometrial and Ovarian Cancers

Exhibit 99.1 Mersana Therapeutics Announces Initiation of Phase 1 Trial of XMT-1660 in Breast, Endometrial and Ovarian Cancers CAMBRIDGE, Mass., August 16, 2022 ? Mersana Therapeutics, Inc. (NASDAQ: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet medical need, today announ

August 16, 2022 8-K

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 16, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commiss

August 8, 2022 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeutics,

August 8, 2022 EX-99.1

Mersana Therapeutics Provides Business Update and Announces Second Quarter 2022 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces Second Quarter 2022 Financial Results - Approaching full enrollment in UPLIFT clinical trial; initiated patient screening in UP-NEXT clinical trial - Cleared INDs for XMT-1660 and XMT-2056 - Enhanced balance sheet with $100 million upfront option purchase fee to be paid by GSK for XMT-2056 - Conference call today at 4:30 p.m.

August 8, 2022 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 8, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissi

August 8, 2022 EX-99.1

Mersana Therapeutics Announces Option Agreement with GSK for the Co-Development and Commercialization of XMT-2056, an Immunosynthen ADC Targeting HER2

Exhibit 99.1 Mersana Therapeutics Announces Option Agreement with GSK for the Co-Development and Commercialization of XMT-2056, an Immunosynthen ADC Targeting HER2 - GSK receives exclusive global license option for XMT-2056 - Mersana to receive $100 million upfront option purchase fee - If GSK exercises its option, Mersana to receive exercise payment; potential for additional development, regulato

August 8, 2022 8-K

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 6, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissi

June 10, 2022 EX-3.1

Fifth Amended and Restated Certificate of Incorporation, as amended, as of June 9, 2022.

Exhibit 3.1 FIFTH AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF MERSANA THERAPEUTICS, INC. (Composite document reflecting amendments through June 9, 2022) ARTICLE I ? NAME The name of the corporation is Mersana Therapeutics, Inc. (the ?Corporation?). ARTICLE II ? REGISTERED OFFICE AND AGENT The address of the Corporation?s registered office in the State of Delaware is located at Corporation

June 10, 2022 8-K

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 9, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

May 11, 2022 SC 13D/A

MRSN / Mersana Therapeutics Inc / Bain Capital Life Sciences Fund II, L.P. - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13D (Rule 13d-101) Information to be Included in Statements Filed Pursuant to ? 240.

May 9, 2022 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38129 Mersana Therapeutics,

May 9, 2022 EX-10.3

Amendment No. 1 to the Amended and Restated Commercial License and Option Agreement, dated February 2, 2022, between Mersana Therapeutics, Inc. and Synaffix B.V. (incorporated by reference to Exhibit 10.3 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on May 9, 2022).

Exhibit 10.3 EXECUTION COPY Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. Amendment #1 to the Amended and Restated Commercial License and Option Agreement This Amendment #1 (this "Amendment") dated February 2, 2022 (th

May 9, 2022 EX-99.1

Mersana Therapeutics Provides Business Update and Announces First Quarter 2022 Financial Results

Exhibit 99.1 Mersana Therapeutics Provides Business Update and Announces First Quarter 2022 Financial Results - Advanced UpRi development across UPLIFT, UPGRADE, and UP-NEXT clinical trials - Prepared for expected initiation of patient dosing in Phase 1 clinical trials of XMT-1660 and XMT-2056 in mid-2022 - Entered research collaboration and license agreement with Janssen, which provided $40 milli

May 9, 2022 EX-10.4

First Amendment to Loan and Security Agreement, dated February 17, 2022, between Oxford Finance LLC, the Lenders named therein including Silicon Valley Bank, and Mersana Therapeutics, Inc. (incorporated by reference to Exhibit 10.4 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on May 9, 2022).

Exhibit 10.4 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. FIRST AMENDMENT TO LOAN AND SECURITY AGREEMENT THIS FIRST AMENDMENT TO LOAN AND SECURITY AGREEMENT (this ?Amendment?) is entered into as of February 17, 2022,

May 9, 2022 EX-10.6

Offer Letter, dated June 15, 2021, between Mersana Therapeutics, Inc. and Tushar Misra (incorporated by reference to Exhibit 10.6 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on May 9, 2022).

Exhibit 10.6 Mersana Therapeutics, Inc. 840 Memorial Dr. Cambridge, MA 02139 June 15, 2021 VIA E-MAIL Tushar Misra c/o Mersana Therapeutics, Inc. 840 Memorial Drive Cambridge, MA 02139 Dear Tushar: I am pleased to offer you the position of SVP and Chief Manufacturing Officer of Mersana Therapeutics, Inc. (the ?Company?), and present you with the terms and conditions of your employment by the Compa

May 9, 2022 EX-10.2

Research Collaboration and License Agreement, dated February 2, 2022, between Mersana Therapeutics, Inc. and Janssen Biotech, Inc. (incorporated by reference to Exhibit 10.2 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on May 9, 2022).

Exhibit 10.2 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. RESEARCH COLLABORATION AND LICENSE AGREEMENT between MERSANA THERAPEUTICS, INC. and JANSSEN BIOTECH, INC. Table of Contents ARTICLE 1 1 1.1 Definitions 1 1.2 C

May 9, 2022 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 9, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

May 9, 2022 EX-10.5

Offer Letter, dated March 5, 2021, by and between Mersana Therapeutics, Inc. and Alejandra Carvajal (incorporated by reference to Exhibit 10.5 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on May 9, 2022).

Exhibit 10.5 Mersana Therapeutics, Inc. 840 Memorial Dr. Cambridge, MA 02139 March 7, 2021 VIA E-MAIL Alejandra Carvajal c/o Mersana Therapeutics, Inc. 840 Memorial Drive Cambridge, MA 02139 Dear Alejandra: I am pleased to offer you the position of SVP and General Counsel of Mersana Therapeutics, Inc. (the ?Company?), and present you with the terms and conditions of your employment by the Company,

April 29, 2022 DEF 14A

our definitive proxy statement on Schedule 14A for the 2022 Annual Meeting of Stockholders;

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549? SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ?) Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? ? Confidential, for Use of the Commission Only (as permitted by Rul

April 29, 2022 DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ?) Filed by the Registrant x Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Defi

April 18, 2022 PRE 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

PRE 14A 1 tm223478-1pre14a.htm PRE 14A TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the

April 14, 2022 SC 13D/A

MRSN / Mersana Therapeutics Inc / Bain Capital Life Sciences Fund II, L.P. - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13D (Rule 13d-101) Information to be Included in Statements Filed Pursuant to ? 240.

February 28, 2022 8-K

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 28, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

February 28, 2022 EX-10.28

2022 Inducement Stock Incentive Plan (incorporated by reference to Exhibit 10.28 to the Annual Report on Form 10-K (File No. 001-38129) filed with the SEC on February 28, 2022).

Exhibit 10.28 MERSANA THERAPEUTICS, INC. 2022 INDUCEMENT STOCK INCENTIVE PLAN 1.DEFINED TERMS The following terms, when used in the Plan (as defined below), have the meanings and are subject to the provisions set forth below: (a)?Accounting Rules?: Financial Accounting Standards Board Accounting Standards Codification Topic 718, or any successor provision. (b)?Administrator?: The Compensation Comm

February 28, 2022 EX-FILING FEES

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) Mersana Therapeutics, Inc.

February 28, 2022 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 28, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

February 28, 2022 EX-21.1

Subsidiaries of Mersana Therapeutics, Inc.

Exhibit 21.1 Subsidiaries of the Registrant Entity State of Incorporation or Organization Mersana Securities Corp. Massachusetts

February 28, 2022 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ? ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2021. OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38

February 28, 2022 424B5

$100,000,000 Common Stock

TABLE OF CONTENTS ?Filed Pursuant to Rule 424(b)(5)? ?Registration No. 333-260895? PROSPECTUS SUPPLEMENT (To Prospectus Dated November 18, 2021) $100,000,000 Common Stock We entered into a sales agreement, or the sales agreement, with Cowen and Company, LLC, or Cowen, on February 28, 2022 pursuant to which we may issue and sell, from time to time, shares of our common stock, $0.0001 per share, hav

February 28, 2022 EX-99.2

Mersana Therapeutics, Inc. 2022 Inducement Stock Incentive Plan (filed herewith)

Exhibit 99.2 MERSANA THERAPEUTICS, INC. 2022 INDUCEMENT STOCK INCENTIVE PLAN 1. DEFINED TERMS The following terms, when used in the Plan (as defined below), have the meanings and are subject to the provisions set forth below: (a) ?Accounting Rules?: Financial Accounting Standards Board Accounting Standards Codification Topic 718, or any successor provision. (b) ?Administrator?: The Compensation Co

February 28, 2022 EX-10.30

Form of Non-statutory Stock Option Agreement under the 2022 Inducement Stock Incentive Plan (incorporated by reference to Exhibit 10.30 to the Annual Report on Form 10-K (File No. 001-38129) filed with the SEC on February 28, 2022).

Exhibit 10.30 Name: [?] Number of Shares of Stock subject to the Stock Option: [?] Exercise Price Per Share: $[?] Date of Grant: [?] Vesting Commencement Date [?] MERSANA THERAPEUTICS, INC. 2022 INDUCEMENT STOCK INCENTIVE PLAN NON-STATUTORY STOCK OPTION AGREEMENT This agreement (this ?Agreement?) evidences a stock option granted by the Company to the individual named above (the ?Optionee?), pursua

February 28, 2022 EX-1.1

(incorporated by reference to Exhibit 1.1 to the Company's Current Report on Form 8-K filed

Exhibit 1.1 MERSANA THERAPEUTICS, INC. $100,000,000 common stock SALES AGREEMENT February 28, 2022 Cowen and Company, LLC 599 Lexington Avenue New York, NY 10022 Ladies and Gentlemen: Mersana Therapeutics, Inc. (the ?Company?), confirms its agreement (this ?Agreement?) with Cowen and Company, LLC (?Cowen?), as follows: 1. Issuance and Sale of Shares. The Company agrees that, from time to time duri

February 28, 2022 EX-10.15

Amended and Restated Commercial License and Option Agreement, dated November 23, 2021, by and between Synaffix B.V. and Mersana Therapeutics, Inc. (incorporated by reference to Exhibit 10.15 to Annual Report on Form 10-K (File No. 001-38129) filed with the SEC on February 28, 2022).

Exhibit 10.15 CONFIDENTIAL EXECUTION COPY Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks denote omissions. AMENDED AND RESTATED COMMERCIAL LICENSE AND OPTION AGREEMENT BETWEEN SYNAFFIX B.V. AND MERSANA THERAPEUTICS, INC. DATED AS OF JANU

February 28, 2022 EX-10.14

Loan and Security Agreement, dated October 29, 2021, by and between Oxford Finance LLC, Silicon Valley Bank and Mersana Therapeutics, Inc. (incorporated by reference to Exhibit 10.14 to Annual Report on Form 10-K (File No. 001-38129) filed with the SEC on February 28, 2022).

Exhibit 10.14 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Double asterisks demote omissions. LOAN AND SECURITY AGREEMENT THIS LOAN AND SECURITY AGREEMENT (as the same may from time to time be amended, modified, supplemented or restated, this ?Agreemen

February 28, 2022 S-8

As filed with the Securities and Exchange Commission on February 28, 2022

As filed with the Securities and Exchange Commission on February 28, 2022 Registration No.

February 28, 2022 EX-10.29

(incorporated by reference to Exhibit 10.29 to the Annual Report on Form 10-K (File No. 001-38129) filed with the SEC on February 28, 2022).

Exhibit 10.29 Name: [?] Number of RSUs: [?] Date of Grant: [?] Vesting Commencement Date [?] MERSANA THERAPEUTICS, INC. 2022 INDUCEMENT STOCK INCENTIVE PLAN RESTRICTED STOCK UNIT AGREEMENT This agreement (this ?Agreement?) evidences a grant of restricted stock units (?RSUs?) by Mersana Therapeutics, Inc. (the ?Company?) to the individual named above (the ?Grantee?), pursuant to and subject to the

February 28, 2022 EX-99.1

Mersana Therapeutics Announces Fourth Quarter and Full Year 2021 Financial Results and Provides Business Update - UPLIFT on track to complete enrollment Q3 2022, UP-NEXT to initiate in Q2 2022, and UPGRADE on track for 2H 2022 interim data readout -

Exhibit 99.1 Mersana Therapeutics Announces Fourth Quarter and Full Year 2021 Financial Results and Provides Business Update - UPLIFT on track to complete enrollment Q3 2022, UP-NEXT to initiate in Q2 2022, and UPGRADE on track for 2H 2022 interim data readout - XMT-1660 and XMT-2056 expected to enter clinic mid-2022 - Research collaboration and license agreement with Janssen leverages Mersana?s A

February 17, 2022 SC 13G

MRSN / Mersana Therapeutics Inc / MILLENNIUM MANAGEMENT LLC Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 MERSANA THERAPEUTICS, INC. (Name of Issuer) COMMON STOCK, PAR VALUE $0.0001 PER SHARE (Title of Class of Securities) 59045L106 (CUSIP Number) FEBRUARY 15, 2022 (Date of event which requires filing of this statement) Check the appropriate box to designate the rule pursuant

February 10, 2022 SC 13G

MRSN / Mersana Therapeutics Inc / VANGUARD GROUP INC - SCHEDULE 13G Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 Name of issuer: Mersana Therapeutics Inc. Title of Class of Securities: Common Stock CUSIP Number: 59045L106 Date of Event Which Requires Filing of this Statement: December 31, 2021 Check the appropriate box to designate the rule pursuant to which this Schedule is filed: ☒ Rule 13d-1(b)

February 8, 2022 SC 13D/A

MRSN / Mersana Therapeutics Inc / Bain Capital Life Sciences Fund II, L.P. - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13D (Rule 13d-101) Information to be Included in Statements Filed Pursuant to ? 240.

February 4, 2022 SC 13G/A

MRSN / Mersana Therapeutics Inc / WELLINGTON MANAGEMENT GROUP LLP - SEC SCHEDULE 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1 )* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 59045L106 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which

February 3, 2022 8-K

Entry into a Material Definitive Agreement, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 2, 2022 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

January 3, 2022 SC 13D/A

MRSN / Mersana Therapeutics Inc / Bain Capital Life Sciences Fund II, L.P. - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13D (Rule 13d-101) Information to be Included in Statements Filed Pursuant to ? 240.

November 23, 2021 8-K

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 23, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

November 16, 2021 CORRESP

MERSANA THERAPEUTICS, INC. 840 Memorial Drive Cambridge, MA 02139

MERSANA THERAPEUTICS, INC. 840 Memorial Drive Cambridge, MA 02139 November 16, 2021 VIA EDGAR Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F. Street, N.E. Washington, D.C. 20549 Attention: Chris Edwards Re: Mersana Therapeutics, Inc. Registration Statement on Form S-3 (File No. 333-260895) Request for Acceleration Ladies and Gentlemen: Pursuant to

November 9, 2021 S-3

As filed with the Securities and Exchange Commission on November 9, 2021 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-3 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MERSANA THERAPEUTICS, INC. (Exact name o

TABLE OF CONTENTS As filed with the Securities and Exchange Commission on November 9, 2021 ? ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

November 9, 2021 EX-99.1

Mersana Therapeutics Announces Third Quarter 2021 Financial Results and Provides Business Update

Exhibit 99.1 Mersana Therapeutics Announces Third Quarter 2021 Financial Results and Provides Business Update - Reported updated data from the UpRi ovarian cancer expansion cohort further bolstering confidence in UPLIFT registration strategy - Introduced UP-NEXT, a Phase 3 study of UpRi monotherapy maintenance in platinum-sensitive ovarian cancer - Presented preclinical data for XMT-2056, a HER2-t

November 9, 2021 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 9, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commis

November 9, 2021 EX-10.1

Certain portions of this exhibit have been omitted because they are not material and is the type of information that the registrant treats as private or confidential

Exhibit 10.1 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Triple asterisks denote omissions. SECOND AMENDMENT TO THE LICENSE, DEVELOPMENT AND COMMERCIALIZATION AGREEMENT This Second Amendment (the ?Second Amendment?) to the License, Development and Com

November 9, 2021 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number 001-38129 Mersana Therapeutics, Inc. (Exact name of registran

October 29, 2021 8-K

Entry into a Material Definitive Agreement, Termination of a Material Definitive Agreement, Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 29, 2021 MERSANA THERAPEUTICS, INC. (Exact Name of Company as Specified in its Charter) Delaware 001-38129 04-3562403 (State or Other Jurisdiction of Incorporation) (Commissio

September 16, 2021 SC 13G

MRSN / Mersana Therapeutics Inc / BB BIOTECH AG - SC 13G Passive Investment

SC 13G United States SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 MERSANA THERAPEUTICS, INC. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 59045L106 (CUSIP Number) September 10, 2021 (Date of Event Which Requires Filing This Statement) Check the appropriate box to designate the rule purs

September 10, 2021 EX-99.1

Interim Data from the Ovarian Cancer Expansion Cohort and Next Steps for UpRi Development Plan September 10, 2021 Legal Disclaimer This presentation contains “forward-looking” statements within the meaning of federal securities laws. These forward-lo

Exhibit 99.1 Interim Data from the Ovarian Cancer Expansion Cohort and Next Steps for UpRi Development Plan September 10, 2021 Legal Disclaimer This presentation contains ?forward-looking? statements within the meaning of federal securities laws. These forward-looking statements are not statements of historical facts and are based on management?s beliefs and assumptions and on information currentl

September 10, 2021 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 10, 2021 MERSANA THERAP

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 10, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Comm

August 16, 2021 EX-99.1

Mersana Therapeutics Announces Appointment of Tushar Misra, Ph.D., as Chief Manufacturing Officer - Dr. Misra to succeed Michael Kaufman, Ph.D., Chief Manufacturing Officer, who will retire in September 2021 following a planned transition period

Exhibit 99.1 Mersana Therapeutics Announces Appointment of Tushar Misra, Ph.D., as Chief Manufacturing Officer - Dr. Misra to succeed Michael Kaufman, Ph.D., Chief Manufacturing Officer, who will retire in September 2021 following a planned transition period CAMBRIDGE, Mass., August 16, 2021 - Mersana Therapeutics, Inc. (Nasdaq: MRSN), a clinical-stage biopharmaceutical company focused on discover

August 16, 2021 8-K

Regulation FD Disclosure, Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 16, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commiss

August 6, 2021 EX-99.1

Mersana Therapeutics Announces Second Quarter 2021 Financial Results and Provides Business Update

Exhibit 99.1 Mersana Therapeutics Announces Second Quarter 2021 Financial Results and Provides Business Update - Initiated UPGRADE, a Phase 1 platinum combination cohort in platinum-sensitive ovarian cancer - Company plans to disclose target and preclinical data for XMT-2056, first Immunosynthen STING-agonist ADC, at AACR-NCI-EORTC - Ended second quarter with $227.4M in cash and equivalents CAMBRI

August 6, 2021 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number 001-38129 Mersana Therapeutics, Inc. (Exact name of registrant as

August 6, 2021 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 6, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissi

August 6, 2021 EX-10.1

Form of Restricted Stock Unit Agreement under the Mersana Therapeutics, Inc. 2017 Stock Incentive Plan (incorporated by reference to Exhibit 10.1 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on August 6, 2021).

Exhibit 10.1 MERSANA THERAPEUTICS, INC. 2017 STOCK INCENTIVE PLAN RESTRICTED STOCK UNIT AGREEMENT This agreement (this ?Agreement?) evidences a grant of restricted stock units (?RSUs?) by Mersana Therapeutics, Inc. (the ?Company?) to the individual named above (the ?Grantee?), an employee of the Company, pursuant to and subject to the terms of the Mersana Therapeutics, Inc. 2017 Stock Incentive Pl

June 17, 2021 8-K

Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 11, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissio

May 10, 2021 EX-10.3

Amended and Restated Offer Letter, by and between Mersana Therapeutics, Inc. and Michael Kaufman, dated March 8, 2017.

Exhibit 10.3 Mersana Therapeutics, Inc. 840 Memorial Dr. Cambridge, MA 02139 March 8, 2017 VIA HAND DELIVERY Michael J. Kaufman C/O Mersana Therapeutics, Inc. 840 Memorial Drive Cambridge, MA 02139 Dear Michael: This letter agreement (this ?Agreement?) amends and restates in its entirety, as of the date set forth above, the offer letter between you and Mersana Therapeutics, Inc. (the ?Company?) da

May 10, 2021 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 10, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commission

May 10, 2021 EX-10.1

Eighth Lease Modification Agreement to the Lease Between Rivertech Associates II LLC and Mersana Therapeutics, Inc., effective as of April 5, 2021, by and between Mersana Therapeutics, Inc. and Rivertech Associates II LLC (incorporated by reference to Exhibit 10.1 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on May 10, 2021).

Exhibit 10.1 RIVERSIDE TECHNOLOGY CENTER EIGHTH LEASE MODIFICATION AGREEMENT TO THE LEASE BETWEEN RIVERTECH ASSOCIATES II LLC AND MERSANA THERAPEUTICS, INC. This Eighth Lease Modification Agreement entered into this 25th day of March, 2021 (the ?Eighth Lease Amendment?) by and between Rivertech Associates II LLC, a Massachusetts limited liability company with a principal address c/o The Abbey Grou

May 10, 2021 EX-99.1

Mersana Therapeutics Announces First Quarter 2021 Financial Results and Provides Business Update - Initiated UPLIFT single-arm registration strategy for evaluation of UpRi in platinum-resistant ovarian cancer - Ended first quarter of 2021 with $228 m

EX-99.1 5 tm2115779d1ex99-1.htm EXHIBIT 99.1 Exhibit 99.1 Mersana Therapeutics Announces First Quarter 2021 Financial Results and Provides Business Update - Initiated UPLIFT single-arm registration strategy for evaluation of UpRi in platinum-resistant ovarian cancer - Ended first quarter of 2021 with $228 million in cash CAMBRIDGE, Mass., May 10, 2021 - Mersana Therapeutics, Inc. (NASDAQ:MRSN), a

May 10, 2021 10-Q

Quarterly Report - 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number 001-38129 Mersana Therapeutics, Inc. (Exact name of registrant as

May 10, 2021 EX-10.2

Offer Letter, by and between Mersana Therapeutics, Inc. and Arvin Yang, dated November 5, 2020 (incorporate by reference to Exhibit 10.2 to the Quarterly Report on Form 10-Q (File No. 001-38129) filed with the SEC on May 10, 2021).

Exhibit 10.2 Mersana Therapeutics, Inc. 840 Memorial Dr. Cambridge, MA 02139 November 5, 2020 VIA E-MAIL Arvin S. Yang, MD, PHD c/o Mersana Therapeutics, Inc. 840 Memorial Drive Cambridge, MA 02139 Dear Arvin: I am pleased to offer you the position of SVP and Chief Medical Officer of Mersana Therapeutics, Inc. (the ?Company?), and present you with the terms and conditions of your employment by the

May 10, 2021 S-8

- FORM S-8

Registration No. 333- As filed with the Securities and Exchange Commission on May 10, 2021 UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM S-8 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 04-3562403 (State or other jurisdiction of incorporation or organization) (I.R.S. E

May 10, 2021 EX-99.1

Form of Inducement Stock Option Agreement for inducement grants made in August and October 2021

Exhibit 99.1 Name: Number of Shares of Stock subject to the Stock Option: Exercise Price Per Share: Date of Grant: Vesting Commencement Date MERSANA THERAPEUTICS, INC. Inducement Stock Option Agreement This agreement (this ?Agreement?) evidences a stock option (the ?Stock Option?) granted by the Company to the individual named above (the ?Optionee?), as an inducement material to the Optionee?s ent

April 27, 2021 DEF 14A

definitive proxy statement on Schedule 14A, as filed with the SEC on April 27, 2021;

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant x Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) x Defin

April 27, 2021 DEFA14A

- DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant x Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Defin

April 9, 2021 8-K

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 5, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissio

March 11, 2021 EX-99.1

Mersana Therapeutics Announces Appointment of Allene Diaz to Board of Directors

Exhibit 99.1 Mersana Therapeutics Announces Appointment of Allene Diaz to Board of Directors CAMBRIDGE, Mass., March 11, 2021 - Mersana Therapeutics, Inc. (Nasdaq: MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet medical need, today announced the appointment of Allene Diaz

March 11, 2021 8-K

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 11, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commissi

February 26, 2021 EX-21.1

Subsidiaries of Mersana Therapeutics, Inc.

EX-21.1 2 exhibit21110kfy2020q4.htm EX-21.1 Exhibit 21.1 Subsidiaries of the Registrant Entity State of Incorporation or Organization Mersana Securities Corp. Massachusetts

February 26, 2021 EX-99.1

Mersana Therapeutics Announces Fourth Quarter and Full Year 2020 Financial Results and Provides Business Update - UPLIFT, a single-arm registration strategy evaluating upifitamab rilsodotin (UpRi) in platinum-resistant ovarian cancer, on track to beg

EX-99.1 2 tm218056d1ex99-1.htm EXHIBIT 99.1 Exhibit 99.1 Mersana Therapeutics Announces Fourth Quarter and Full Year 2020 Financial Results and Provides Business Update - UPLIFT, a single-arm registration strategy evaluating upifitamab rilsodotin (UpRi) in platinum-resistant ovarian cancer, on track to begin in Q1 2021 - Significantly progressed pipeline of ADC candidates from the Company’s innova

February 26, 2021 8-K

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 26, 2021 MERSANA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38129 04-3562403 (State or other jurisdiction of incorporation) (Commi

February 26, 2021 10-K

Annual Report - 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ? ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2020. OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-38

February 12, 2021 SC 13G

Mersana Therapeutics, Inc.

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Mersana Therapeutics, Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 59045L106 (CUSIP Number) December 31, 2020 (Date of Event Which Requires Filing of This Statement) Check the appropriate box to designate the rule pursu

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