SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* Nayeem Sara M. (Last) (First) (Middle) 1954 GREENSPRING DRIVE SUITE 600 (Street) TIMONIUM MD 21093 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 06/27/2017	3. Issuer Name and Ticker or Trading Symbol Mersana Therapeutics, Inc. [ MRSN ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year) 06/27/2017
			6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

Remarks:

No securities are beneficially owned.

	/s/ Sasha Keough, attorney-in-fact	06/27/2017
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

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, 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 herself as an individual or in 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 section 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 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/ Sara M. Nayeem