New Enterprise Associates 14 SC 13D/A Mersana Therapeutics, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C.  20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

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)

March 5, 2019

(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 20 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			(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 ITEM 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
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	PN

CUSIP No.     59045L106 13D Page 3 of 20 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			(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 ITEM 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
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	PN

CUSIP No.     59045L106 13D Page 4 of 20 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			(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 ITEM 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
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	CO

CUSIP No.     59045L106 13D Page 5 of 20 Pages    

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	Peter J. Barris
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(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 ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.     59045L106 13D Page 6 of 20 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			(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 ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.     59045L106 13D Page 7 of 20 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			(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 ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.     59045L106 13D Page 8 of 20 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			(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 ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER	��
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.     59045L106 13D Page 9 of 20 Pages    

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	David M. Mott
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(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 ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			12,934 shares
		8	SHARED VOTING POWER
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			12,934 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,903,072 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)
	25.0%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.     59045L106 13D Page 10 of 20 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			(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 ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.     59045L106 13D Page 11 of 20 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			(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 ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			11,890,138 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			11,890,138 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	11,890,138 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)
	24.9%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.     59045L106 13D Page 12 of 20 Pages    

Schedule 13D

Item 1. Security and Issuer.

This Amendment No. 1 ("Amendment No. 1") to Schedule 13D amends and restates the statement on Schedule 13D originally filed on July 11, 2017 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. 1 have the meanings assigned thereto in the Schedule 13D. Except as specifically set forth herein, this Amendment No. 1 does not modify any of the information previously reported on the Schedule 13D.

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) Peter J. Barris ("Barris"), Forest Baskett ("Baskett"), Anthony A. Florence, Jr. ("Florence"), Patrick J. Kerins ("Kerins"), David M. Mott ("Mott"), Scott D. Sandell ("Sandell") and Peter W. Sonsini ("Sonsini") (together, the "Directors"), M. James Barrett ("Barrett") and Ravi Viswanathan ("Viswanathan").  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 Barris, Kerins and Mott 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 13 of 20 Pages    

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

On March 5, 2019, the Issuer completed the closing of an underwritten offering of 21,250,000 shares of Common Stock of the Issuer (the "Offering").  At the closing of the Offering, NEA 14 purchased an aggregate of 3,750,000 shares of the Issuer's Common Stock at the Offering price of $4.00 per share from the Issuer.  Prior to the closing, NEA 14 held 8,140,138 shares of the Issuer's Common Stock (the "Prior NEA 14 Shares").  NEA 14 now holds a total of 11,890,138 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 14 of 20 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.

As of March 5, 2019, Mott is the record owner of options to purchase 12,934 shares of Common Stock (the "Mott Option Shares"), exercisable within 60 days.  Accordingly, Mott may be deemed to own beneficially the Mott Option Shares in addition to 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.

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 47,684,164 shares of Common Stock reported to be outstanding immediately after the Offering on the Issuer's Form 10-K, filed with the Securities Exchange Commission on March 8, 2019 (the "10-K Shares").  The percentage set forth on the cover sheet for Mott is calculated based on 47,697,098 shares of Common Stock, which includes (a) the 10-K Shares and (b) the Mott Options Shares.

(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) Each of Barrett and Viswanathan has ceased to own beneficially five percent (5%) or more of the Issuer's Common Stock as a result of ceasing to be a director of NEA 14 LTD.

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

NEA 14 has entered into a lock-up agreement with the underwriters of the Offering pursuant to which NEA 14 has generally agreed, subject to certain exceptions, not to offer, pledge, sell or contract to sell any Common Stock; sell any option or contract to purchase any Common Stock; purchase any option or contract to sell any Common Stock; grant any option, right or warrant to purchase any Common Stock; otherwise transfer or dispose of, directly or indirectly, any Common Stock; publicly disclose the intention to make any offer, sale, pledge or disposition; enter into any swap or other agreement or any transaction that transfers, in whole or in part, any economic consequence of ownership of any Common Stock, whether any such swap, agreement or transaction is to be settled by delivery of shares or other securities, in cash or otherwise; or make any demand for or exercise any right with respect to the registration of any shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock for a period of 90 days from February 28, 2019 without the prior written consent of SVB Leerink LLC on behalf of the underwriters.

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 15 of 20 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 13^th day of March, 2019.

NEW ENTERPRISE ASSOCIATES 14, L.P.

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

By: NEA 14 GP, LTDGeneral Partner

By:         *                                                 

        Peter J. Barris

Director

NEA PARTNERS 14, L.P.

By: NEA 14 GP, LTDGeneral Partner

By:                    *                                             

                 Peter J. Barris

                 Director

NEA 14 GP, LTD

By:                   *                                              

 Peter J. Barris 

 Director

CUSIP No.     59045L106 13D Page 16 of 20 Pages    

         *                                                              

Peter J. Barris

         *                                                              

Forest Baskett

         *                                                              

Patrick J. Kerins

         *                                                              

Anthony A. Florence, Jr.

         *                                                              

David M. Mott

         *                                                              

Scott D. Sandell

         *                                                              

Peter W. Sonsini

*/s/ Sasha O. Keough                        

Sasha O. Keough

As attorney-in-fact

This Amendment No. 1 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 17 of 20 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 13^th day of March, 2019.

NEW ENTERPRISE ASSOCIATES 14, L.P.

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

By: NEA 14 GP, LTDGeneral Partner

By:         *                                                 

      Peter J. Barris

      Director

NEA PARTNERS 14, L.P.

By: NEA 14 GP, LTDGeneral Partner

By:                    *                                             

                 Peter J. Barris

                 Director

NEA 14 GP, LTD

By:                   *                                              

 Peter J. Barris

 Director

CUSIP No.     59045L106 13D Page 18 of 20 Pages    

         *                                                              

Peter J. Barris

         *                                                              

Forest Baskett

         *                                                              

Patrick J. Kerins

         *                                                              

Anthony A. Florence, Jr.

         *                                                              

David M. Mott

         *                                                              

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 19 of 20 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

/s/ Vanessa Larco                        

Vanessa Larco

/s/ Joshua Makower                   

Joshua Makower

CUSIP No.     59045L106 13D Page 20 of 20 Pages    

/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