Timothy B Lowinger - 01 Jul 2021 Form 4 Insider Report for Mersana Therapeutics, Inc. (MRSN)

Role: CS & Technology Officer
Signature: /s/ Brian DeSchuytner, as Attorney-in-Fact
Issuer symbol: MRSN
Transactions as of: 01 Jul 2021
Net transactions value: -$19,006
Form type: 4
Filing time: 02 Jul 2021, 16:32:11 UTC
Previous filing: 23 Jun 2021
Next filing: 09 Jul 2021
SEC: View on sec.gov

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	MRSN	Common Stock	Options Exercise	$6,588	+1,877	+6%	$3.51	33,321	01 Jul 2021	Direct	F1
transaction	MRSN	Common Stock	Options Exercise	$55.44	+9	+0.03%	$6.16	33,330	01 Jul 2021	Direct	F1
transaction	MRSN	Common Stock	Sale	$25,650	-1,886	-5.7%	$13.60^*	31,444	01 Jul 2021	Direct	F1

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	MRSN	Stock Option (right to buy)	Options Exercise	$0	-1,877	-15%	$0.000000	10,303	01 Jul 2021	Common Stock	1,877	$3.51	Direct	F1, F2
transaction	MRSN	Stock Option (right to buy)	Options Exercise	$0	-9	-0.01%	$0.000000	81,638	01 Jul 2021	Common Stock	9	$6.16	Direct	F1, F3

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Transaction effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 12, 2020.
F2	The option vests in equal quarterly installments over the first four years after the vesting commencement date, January 23, 2019.
F3	The option vests in equal quarterly installments over the first four years after the vesting commencement date, January 15, 2020.