SEC FORM 3

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^*

Protopapas Anna

(Last)

(First)

(Middle)

C/O MERSANA THERAPEUTICS, INC.

840 MEMORIAL DRIVE

(Street)

CAMBRIDGE

02139

(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
X	Officer (give title below)	Other (specify below)
	President and CEO

5. If Amendment, Date of Original Filed (Month/Day/Year)

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)
Common Stock	120,302	D

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)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	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)
Option to Purchase Common Stock	⁽¹⁾	05/07/2025	Common Stock	758,783	$1.53	D
Option to Purchase Common Stock	⁽²⁾	08/29/2026	Common Stock	158,958	$4.1	D
Option to Purchase Common Stock	⁽³⁾	03/13/2027	Common Stock	66,666	$6.98	D
Series B-1 Convertible Preferred Stock	⁽⁴⁾	⁽⁴⁾	Common Stock	72,263	⁽⁴⁾	I	By Kinney/Protopapas Family Irrevocable Trust⁽⁵⁾

Explanation of Responses:

1. The original option grant for 879,085 option shares vested 25% on March 2, 2016 and in equal quarterly installments thereafter.

2. The options vest in equal quarterly installments over the first four years after the vesting commencement date, July 1, 2016.

3. The options vest in equal quarterly installments over the first four years after the vesting commencement date, March 14, 2017.

4. Series B-1 Convertible Preferred Stock is convertible into shares of common stock at any time at the holder's election and automatically upon the consummation of a public offering of the registrant. There is no expiration date for the Series B-1 Convertible Preferred Stock.

5. These securities are held in a trust for the benefit of the reporting person's children. The reporting person's spouse is trustee of the trust. The reporting person disclaims beneficial ownership of these securities, and the filing of this report is not an admission that the reporting person is the beneficial owner of these securities for purposes of Section 16 or for any other purpose.

Remarks:

Exhibit List Exhibit 24 - Power of Attorney

	/s/ Eva M. Jack, as 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.
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