Andrew Hack - Jun 8, 2023 Form 4 Insider Report for Mersana Therapeutics, Inc. (MRSN)

Role: Director
Signature: /s/ Andrew Hack
Stock symbol: MRSN
Transactions as of: Jun 8, 2023
Transactions value $: $0
Form type: 4
Date filed: 6/12/2023, 05:25 PM
Previous filing: May 31, 2023
Next filing: Jun 16, 2023

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	MRSN	Common Stock	Award	$0	+14.5K		$0.00	14.5K	Jun 8, 2023	Direct	F1, F2
holding	MRSN	Common Stock						8.66M	Jun 8, 2023	See footnotes	F3, F4

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)	Award	$0	+18.4K		$0.00	18.4K	Jun 8, 2023	Common Stock	18.4K	$8.64	Direct	F2

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

Explanation of Responses:

Id	Content
F1	Represents a restricted stock unit ("RSU") award. Each RSU represents the contingent right to receive one share of Common Stock of the Issuer.
F2	The award will vest in full on the earlier of the first anniversary of the date of grant or the date of the 2024 Annual Meeting of Stockholders of the Issuer, subject to the Reporting Person's continuous service with the Issuer on such vesting date.
F3	Represents shares of Common Stock held directly by Bain Capital Life Sciences Fund II, L.P. ("BCLS II"), BCIP Life Sciences Associates, LP ("BCIPLS") and BCLS II Investco, LP ("BCLS II Investco" and, together with BCLS II and BCIPLS, the "Bain Capital Life Sciences Entities").
F4	Bain Capital Life Sciences Investors, LLC ("BCLSI") (i) is the ultimate general partner of each of BCLS II and BCLS II Investco and (ii) governs the investment strategy and decision-making process with respect to investments held by BCIPLS. The Reporting Person is a Partner of BCLSI. As a result, the Reporting Person may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. The Reporting Person disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.