UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 3)*

Mersana Therapeutics, Inc.

(Name of Issuer)

Common Stock, $.0001 par value

(Title of Class of Securities)

59045L106

(CUSIP Number)

Louis S. Citron, Esq.

New Enterprise Associates

1954 Greenspring Drive, Suite 600, Timonium, MD 21093

(410) 842-4000

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

September 14, 2020

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

^* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 59045L106 13D Page 2 of 19 Pages    

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) New Enterprise Associates 14, L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (see instructions)	(a) ☐ (b) ☐
3.	SEC USE ONLY
4.	SOURCE OF FUNDS (see instructions) WC
5.	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)	☐
6.	CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7.	SOLE VOTING POWER 0 Shares
	8.	SHARED VOTING POWER 5,959,520 shares
	9.	SOLE DISPOSITIVE POWER 0 Shares
	10.	SHARED DISPOSITIVE POWER 5,959,520 shares

11.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,959,520 shares
12.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (see instructions)	☐
13.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.7%
14.	TYPE OF REPORTING PERSON (see instructions) PN

CUSIP No. 59045L106 13D Page 3 of 19 Pages    

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) NEA Partners 14, L.P.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (see instructions)	(a) ☐ (b) ☐
3.	SEC USE ONLY
4.	SOURCE OF FUNDS (see instructions) AF
5.	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)	☐
6.	CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7.	SOLE VOTING POWER 0 Shares
	8.	SHARED VOTING POWER 5,959,520 shares
	9.	SOLE DISPOSITIVE POWER 0 Shares
	10.	SHARED DISPOSITIVE POWER 5,959,520 shares

11.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,959,520 shares
12.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (see instructions)	☐
13.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.7%
14.	TYPE OF REPORTING PERSON (see instructions) PN

 CUSIP No. 59045L106 13D Page 4 of 19 Pages    

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) NEA 14 GP, LTD
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (see instructions)	(a) ☐ (b) ☐
3.	SEC USE ONLY
4.	SOURCE OF FUNDS (see instructions) AF
5.	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)	☐
6.	CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7.	SOLE VOTING POWER 0 Shares
	8.	SHARED VOTING POWER 5,959,520 shares
	9.	SOLE DISPOSITIVE POWER 0 Shares
	10.	SHARED DISPOSITIVE POWER 5,959,520 shares

11.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,959,520 shares
12.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (see instructions)	☐
13.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.7%
14.	TYPE OF REPORTING PERSON (see instructions) CO

  CUSIP No. 59045L106 13D Page 5 of 19 Pages    

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Forest Baskett
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (see instructions)	(a) ☐ (b) ☐
3.	SEC USE ONLY
4.	SOURCE OF FUNDS (see instructions) AF
5.	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)	☐
6.	CITIZENSHIP OR PLACE OF ORGANIZATION United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7.	SOLE VOTING POWER 1,602 shares
	8.	SHARED VOTING POWER 5,959,520 shares
	9.	SOLE DISPOSITIVE POWER 1,602 shares
	10.	SHARED DISPOSITIVE POWER 5,959,520 shares

11.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,961,122 shares
12.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (see instructions)	☐
13.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.7%
14.	TYPE OF REPORTING PERSON (see instructions) IN

CUSIP No. 59045L106 13D Page 6 of 19 Pages    

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Anthony A. Florence, Jr.
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (see instructions)	(a) ☐ (b) ☐
3.	SEC USE ONLY
4.	SOURCE OF FUNDS (see instructions) AF
5.	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)	☐
6.	CITIZENSHIP OR PLACE OF ORGANIZATION United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7.	SOLE VOTING POWER 3,210 shares
	8.	SHARED VOTING POWER 5,959,520 shares
	9.	SOLE DISPOSITIVE POWER 3,210 shares
	10.	SHARED DISPOSITIVE POWER 5,959,520 shares

11.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,962,730 shares
12.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (see instructions)	☐
13.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.7%
14.	TYPE OF REPORTING PERSON (see instructions) IN

CUSIP No. 59045L106 13D Page 7 of 19 Pages    

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Patrick J. Kerins
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (see instructions)	(a) ☐ (b) ☐
3.	SEC USE ONLY
4.	SOURCE OF FUNDS (see instructions) AF
5.	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)	☐
6.	CITIZENSHIP OR PLACE OF ORGANIZATION United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7.	SOLE VOTING POWER 3,594 shares
	8.	SHARED VOTING POWER 5,959,520 shares
	9.	SOLE DISPOSITIVE POWER 3,594 shares
	10.	SHARED DISPOSITIVE POWER 5,959,520 shares

11.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,963,114 shares
12.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (see instructions)	☐
13.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.7%
14.	TYPE OF REPORTING PERSON (see instructions) IN

CUSIP No. 59045L106 13D Page 8 of 19 Pages    

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Scott D. Sandell
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (see instructions)	(a) ☐ (b) ☐
3.	SEC USE ONLY
4.	SOURCE OF FUNDS (see instructions) AF
5.	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)	☐
6.	CITIZENSHIP OR PLACE OF ORGANIZATION United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7.	SOLE VOTING POWER 1,105 shares
	8.	SHARED VOTING POWER 5,959,520 shares
	9.	SOLE DISPOSITIVE POWER 1,105 shares
	10.	SHARED DISPOSITIVE POWER 5,959,520 shares

11.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,960,625 shares
12.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (see instructions)	☐
13.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.7%
14.	TYPE OF REPORTING PERSON (see instructions) IN

CUSIP No. 59045L106 13D Page 9 of 19 Pages    

1.	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Peter W. Sonsini
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (see instructions)	(a) ☐ (b) ☐
3.	SEC USE ONLY
4.	SOURCE OF FUNDS (see instructions) AF
5.	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)	☐
6.	CITIZENSHIP OR PLACE OF ORGANIZATION United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7.	SOLE VOTING POWER 1,341 shares
	8.	SHARED VOTING POWER 5,959,520 shares
	9.	SOLE DISPOSITIVE POWER 1,341 shares
	10.	SHARED DISPOSITIVE POWER 5,959,520 shares

11.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,960,861 shares
12.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (see instructions)	☐
13.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.7%
14.	TYPE OF REPORTING PERSON (see instructions) IN

CUSIP No. 59045L106 13D Page 10 of 19 Pages    

Item 1.  Security and Issuer.

This Amendment No. 3 (“Amendment No. 3”) to Schedule 13D amends and restates the statement on Schedule 13D originally filed on July 11, 2017, Amendment No. 1 thereto filed on March 14, 2019 and Amendment No. 2 thereto filed on April 24, 2020 relating to the common stock, $.0001 par value (the “Common Stock”) of Mersana Therapeutics, Inc. (the “Issuer”) having its principal executive office at 840 Memorial Drive, Cambridge, Massachusetts 02139.

Certain terms used but not defined in this Amendment No. 3 have the meanings assigned thereto in the Schedule 13D (including Amendment No. 1 and Amendment No. 2 thereto). Except as specifically set forth herein, this Amendment No. 3 does not modify any of the information previously reported on the Schedule 13D (including Amendment No. 1 and Amendment No. 2 thereto).

Item 2.  Identity and Background.

This statement is being filed by:

(a) New Enterprise Associates 14, L.P. (“NEA 14”);

(b) NEA Partners 14, L.P. (“NEA Partners 14”), which is the sole general partner of NEA 14; and NEA 14 GP, LTD (“NEA 14 LTD” and, together with NEA Partners 14, the “Control Entities”), which is the sole general partner of NEA Partners 14; and

(c) Forest Baskett (“Baskett”), Anthony A. Florence, Jr. (“Florence”), Patrick J. Kerins (“Kerins”), Scott D. Sandell (“Sandell”) and Peter W. Sonsini (“Sonsini”) (together, the “Directors”). The Directors are the directors of NEA 14 LTD.

The persons named in this Item 2 are referred to individually herein as a “Reporting Person” and collectively as the “Reporting Persons.”

The address of the principal business office of NEA 14 and each Control Entity is New Enterprise Associates, 1954 Greenspring Drive, Suite 600, Timonium, MD 21093. The address of the principal business office of each of Kerins is New Enterprise Associates, 5425 Wisconsin Avenue, Suite 800, Chevy Chase, MD 20815. The address of the principal business office of Baskett, Sandell and Sonsini is New Enterprise Associates, 2855 Sand Hill Road, Menlo Park, California 94025. The address of the principal business office of Florence is New Enterprise Associates, 104 5^th Avenue, 19^th Floor, New York, NY 10001.

The principal business of NEA 14 is to invest in and assist growth-oriented businesses located principally in the United States. The principal business of NEA Partners 14 is to act as the sole general partner of NEA 14. The principal business of NEA 14 LTD is to act as the sole general partner of NEA Partners 14. The principal business of each of the Directors is to manage the Control Entities, NEA 14 and a number of affiliated partnerships with similar businesses.

During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

NEA 14 and NEA Partners 14 are exempted limited partnerships organized under the laws of the Cayman Islands. NEA 14 LTD is an exempted company organized under the laws of the Cayman Islands. Each of the Directors is a United States citizen.

CUSIP No. 59045L106 13D Page 11 of 19 Pages    

Item 3.  Source and Amount of Funds or Other Consideration.

On September 14, 2020, NEA 14 engaged in a stock distribution of 2,000,000 shares of the Issuer’s Common Stock to its partners for no consideration. NEA Partners 14 acquired 20,000 shares of the Issuer’s Common Stock as a result of the NEA 14 distribution and subsequently engaged in a stock distribution of 20,000 shares of the Issuer’s Common Stock to its partners for no consideration. NEA 14 now holds a total of 5,959,520 shares of the Issuer’s Common Stock (the “NEA 14 Shares”).

The working capital of NEA 14 was the source of the funds for the purchase of the NEA 14 Shares. No part of the purchase price of the NEA 14 Shares was represented by funds or other consideration borrowed or otherwise obtained for the purpose of acquiring, holding, trading or voting the NEA 14 Shares.

Item 4.  Purpose of Transaction.

NEA 14 acquired the NEA 14 Shares for investment purposes. Depending on market conditions, its continuing evaluation of the business and prospects of the Issuer and other factors, NEA 14 and other Reporting Persons may dispose of or acquire additional shares of the Issuer. Except as set forth above, none of the Reporting Persons has any present plans which relate to or would result in:

(a) The acquisition by any person of additional securities of the Issuer, or the disposition of securities of the Issuer;

(b) An extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries;

(c) A sale or transfer of a material amount of assets of the Issuer or any of its subsidiaries;

(d) Any change in the present board of directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board;

(e) Any material change in the present capitalization or dividend policy of the Issuer;

(f) Any other material change in the Issuer’s business or corporate structure;

(g) Changes in the Issuer’s charter, bylaws or instruments corresponding thereto or other actions which may impede the acquisition of control of the Issuer by any person;

(h) Causing a class of securities of the Issuer to be delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association;

(i) A class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Securities Exchange Act of 1934; or

(j) Any action similar to any of those enumerated above.

CUSIP No. 59045L106 13D Page 12 of 19 Pages    

Item 5.  Interest in Securities of the Issuer.

(a) NEA 14 is the record owner of the NEA 14 Shares. As the sole general partner of NEA 14, NEA Partners 14 may be deemed to own beneficially the NEA 14 Shares. As the sole general partner of NEA Partners 14, NEA 14 LTD may be deemed to own beneficially the NEA 14 Shares. As members of NEA 14 LTD, each of the Directors may be deemed to own beneficially the NEA 14 Shares.

Each Reporting Person disclaims beneficial ownership of the NEA 14 Shares other than those shares which such person owns of record.

As of September 14, 2020, Florence is the record owner of 3,210 shares of Common Stock (the “Florence Shares”). Accordingly, Florence may be deemed to own beneficially the Florence Shares in addition to the NEA 14 Shares.

As of September 14, 2020, Kerins is the record owner of 3,594 shares of Common Stock (the “Kerins Shares”). Accordingly, Kerins may be deemed to own beneficially the Florence Shares in addition to the NEA 14 Shares.

As of September 14, 2020, Sonsini is the record owner of 745 shares of Common Stock (the “Sonsini Shares”) and the Peter and Diane Sonsini Family Trust dated January 17, 2007 (the “Sonsini Trust”) is the record owner of 596 shares of Common Stock (the “Sonsini Trust Shares”). As trustee of the Sonsini Trust, Sonsini may be deemed to own beneficially the Sonsini Trust Shares in addition to the Sonsini Shares and the NEA 14 Shares.

As of September 14, 2020, the Blue Mountain Trust, dated April 29, 2019 (the “Blue Mountain Trust”) is the record owner of 829 shares of Common Stock (the “Blue Mountain Trust Shares”), Genevieve P. Hardigg, as trustee of the Jennifer Ayer Sandell Rising River Trust, dated December 20, 2012 (the “Jennifer Rising River Trust”) is the record owner of 138 shares of Common Stock (the “Jennifer Rising River Trust Shares”) and Genevieve P. Hardigg, as trustee of the Scott Sandell Rising River Trust, dated December 20, 2012 (the “Scott Rising River Trust”) is the record owner of 138 shares of Common Stock (the “Scott Rising River Trust Shares”). Sandell may be deemed to own beneficially (i) the Blue Mountain Trust Shares as trustee of the Blue Mountain Trust and (ii) the Jennifer Rising River Trust Shares and Scott Rising River Trust Shares as beneficial owner of the Jennifer Rising River Trust and Scott Rising River Trust, in addition to the NEA 14 Shares.

As of September 14, 2020, the Baskett Family Trust U/A DTD 10/12/2010 (the “Baskett Trust”) is the record owner of 1,602 shares of Common Stock (the “Baskett Trust Shares”). As trustee of the Baskett Trust, Baskett may be deemed to own beneficially the Baskett Trust Shares in addition to the NEA 14 Shares.

The percentage of outstanding Common Stock of the Issuer which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Person’s cover sheet. Such percentage was calculated based on the 68,415,100 shares of Common Stock reported to be outstanding as of August 4, 2020 on the Issuer’s Form 10-Q filed with the Securities and Exchange Commission on August 7, 2020.

(b) Regarding the number of shares as to which such person has:

(i) sole power to vote or to direct the vote: See line 7 of cover sheets

(ii) shared power to vote or to direct the vote: See line 8 of cover sheets

(iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets

(iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets

(c) Except as set forth in Item 3 above, none of the Reporting Persons has effected any transaction in the Common Stock during the last 60 days.

(d) No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, Shares beneficially owned by any of the Reporting Persons.

(e) Not applicable.

CUSIP No. 59045L106 13D Page 13 of 19 Pages    

Item 6.  Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer.

Not applicable.

Item 7.  Material to Be Filed as Exhibits.

Exhibit 1 – Agreement regarding filing of joint Schedule 13D.

Exhibit 2 – Power of Attorney regarding filings under the Securities Exchange Act of 1934, as amended.

CUSIP No. 59045L106 13D Page 14 of 19 Pages    

SIGNATURE

After reasonable inquiry and to the best of its knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

EXECUTED this 21^st day of September, 2020.

NEW ENTERPRISE ASSOCIATES 14, L.P.

By: NEA PARTNERS 14, L.P. General Partner

By: NEA 14 GP, LTD General Partner

  By:          *                                

 Scott D. Sandell

 Director 

NEA PARTNERS 14, L.P.

By: NEA 14 GP, LTD
General Partner

By:          *                                

Scott D. Sandell

Director

NEA 14 GP, LTD

By:          *                                

Scott D. Sandell

Director

CUSIP No. 59045L106 13D Page 15 of 19 Pages    

                 *                        

Forest Baskett

                 *                        

Anthony A. Florence, Jr.

                 *                        

Patrick J. Kerins

                 *                        

Scott D. Sandell

                 *                        

Peter W. Sonsini

*/s/ Sasha O. Keough           

Sasha O. Keough

As attorney-in-fact

This Amendment No. 3 to Schedule 13D was executed by Sasha O. Keough on behalf of the individuals listed above pursuant to a Power of Attorney a copy of which is attached as Exhibit 2.

CUSIP No. 59045L106 13D Page 16 of 19 Pages    

EXHIBIT 1

AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, the undersigned hereby agree that only one statement containing the information required by Schedule 13D need be filed with respect to the ownership by each of the undersigned of shares of stock of Mersana Therapeutics, Inc.

EXECUTED this 21^st day of September, 2020.

NEW ENTERPRISE ASSOCIATES 14, L.P.

By: NEA PARTNERS 14, L.P. General Partner

By: NEA 14 GP, LTD General Partner

  By:          *                                

 Scott D. Sandell

 Director 

NEA PARTNERS 14, L.P.

By: NEA 14 GP, LTD
General Partner

By:          *                                

Scott D. Sandell

Director

NEA 14 GP, LTD

By:          *                                

Scott D. Sandell

Director

CUSIP No. 59045L106 13D Page 17 of 19 Pages    

                 *                        

Forest Baskett

                 *                        

Patrick J. Kerins

                 *                        

Anthony A. Florence, Jr.

                 *                        

Scott D. Sandell

                 *                        

Peter W. Sonsini

*/s/ Sasha O. Keough           

Sasha O. Keough

As attorney-in-fact

This Agreement relating to Schedule 13D was executed by Sasha O. Keough on behalf of the individuals listed above pursuant to a Power of Attorney a copy of which is attached hereto as Exhibit 2.

CUSIP No. 59045L106 13D Page 18 of 19 Pages    

EXHIBIT 2

POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes and appoints Louis S. Citron, Timothy Schaller, Sasha Keough and Stephanie Brecher, and each of them, with full power to act without the others, his or her true and lawful attorney-in-fact, with full power of substitution, to sign any and all instruments, certificates and documents that may be necessary, desirable or appropriate to be executed on behalf of himself as an individual or in his or her capacity as a direct or indirect general partner, director, officer or manager of any partnership, corporation or limited liability company, pursuant to section 13 or 16 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and any and all regulations promulgated thereunder, and to file the same, with all exhibits thereto, and any other documents in connection therewith, with the Securities and Exchange Commission, and with any other entity when and if such is mandated by the Exchange Act or by the Financial Industry Regulatory Authority, granting unto said attorney-in-fact full power and authority to do and perform each and every act and thing necessary, desirable or appropriate, fully to all intents and purposes as he or she might or could do in person, thereby ratifying and confirming all that said attorney-in-fact, or his or her substitutes, may lawfully do or cause to be done by virtue hereof.

IN WITNESS WHEREOF, this Power of Attorney has been signed as of the 13th day of March, 2017.

/s/ M. James Barrett            

M. James Barrett

/s/ Peter J. Barris                

Peter J. Barris

/s/ Forest Baskett                

Forest Baskett

/s/ Ali Behbahani                 

Ali Behbahani

/s/ Colin Bryant                   

Colin Bryant

/s/ Carmen Chang               

Carmen Chang

/s/ Anthony A. Florence, Jr.

Anthony A. Florence, Jr.

/s/ Carol G. Gallagher          

Carol G. Gallagher

/s/ Dayna Grayson               

Dayna Grayson

/s/ Patrick J. Kerins             

Patrick J. Kerins

/s/ P. Justin Klein                

P. Justin Klein

CUSIP No. 59045L106 13D Page 19 of 19 Pages    

/s/ Vanessa Larco               

Vanessa Larco

/s/ Joshua Makower             

Joshua Makower

/s/ Mohamad H. Makhzoumi

Mohamad H. Makhzoumi

/s/ Edward T. Mathers         

Edward T. Mathers

/s/ David M. Mott                

David M. Mott

/s/ Sara M. Nayeem            

Sara M. Nayeem

/s/ Jason R. Nunn                

Jason R. Nunn

/s/ Gregory Papadopoulos    

Gregory Papadopoulos

/s/ Chetan Puttagunta          

Chetan Puttagunta

/s/ Jon Sakoda                     

Jon Sakoda

/s/ Scott D. Sandell              

Scott D. Sandell

/s/ A. Brooke Seawell          

A. Brooke Seawell

/s/ Peter W. Sonsini             

Peter W. Sonsini

/s/ Melissa Taunton             

Melissa Taunton

/s/ Frank M. Torti                

Frank M. Torti

/s/ Ravi Viswanathan           

Ravi Viswanathan

/s/ Paul E. Walker               

Paul E. Walker

/s/ Rick Yang                      

Rick Yang