Mohan Bala - 25 Oct 2025 Form 4 Insider Report for Mersana Therapeutics, Inc. (MRSN)

Reporting relationship: SVP, Chief Development Officer
Issuer ticker: MRSN
Reported as of: 25 Oct 2025
Net transaction value: -$762
SEC form: 4
Accepted by SEC: 28 Oct 2025, 16:10:09 UTC
Prior SEC filing: 17 Jan 2025
Next SEC filing: 06 Jan 2026
Source filing: View source filing
Reporting owner signature: /s/ Alejandra Carvajal, Attorney-in-Fact

Key filing fact

Mohan Bala filed Form 4 for Mersana Therapeutics, Inc. (MRSN) on 28 Oct 2025.

Key facts

This page summarizes Mohan Bala's Form 4 filing for Mersana Therapeutics, Inc. (MRSN).
3 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 28 Oct 2025, 16:10.

Change

Previous filing in this sequence was filed on 17 Jan 2025.
Current net transaction value: -$762.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001991787 Primary reporting owner

Bala Mohan

Relationship: SVP, Chief Development Officer
Address: C/O MERSANA THERAPEUTICS, INC., 840 MEMORIAL DRIVE, CAMBRIDGE
Signature: /s/ Alejandra Carvajal, Attorney-in-Fact
Signature date: 28 Oct 2025

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

MRSN transaction

Common Stock

Options Exercise

Transaction value: $0
Shares: +250
Change %: +9.1%
Price: $0.000000
Shares after: 2,999
Date: 25 Oct 2025
Ownership: Direct
Footnotes: F1, F2

MRSN transaction

Common Stock

Sale

Transaction value: $762
Shares: -77
Change %: -2.6%
Price: $9.90
Shares after: 2,922
Date: 27 Oct 2025
Ownership: Direct
Footnotes: F2, F3

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

MRSN transaction Derivative

Restricted Stock Unit

Options Exercise

Transaction value: $0
Shares: -250
Change %: -100%
Price: $0.000000
Shares after: 0
Date: 25 Oct 2025
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 250
Exercise price
Footnotes: F2, F4, F5

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Rule 10b5-1 trading plan

These transactions were reported as open-market trades under a Rule 10b5-1 plan. The plan lets an insider set trading instructions in advance, which can reduce the risk of trading while in possession of material nonpublic information.

Original filing language: transaction made pursuant to a contract, instruction, or written plan intended to satisfy Rule 10b5-1(c).

Explanation of responses 5 footnotes

Footnote F1

Represents shares of common stock received upon vesting of the restricted stock units ("RSUs") awarded to the Reporting Person on October 25, 2021.

Footnote F2

Amounts reported in this Form 4 reflect the one-for-twenty-five reverse stock split effected by the Issuer on July 25, 2025.

Footnote F3

Represents the sale of shares of common stock to satisfy the Reporting Person's tax withholding obligations in connection with the service-based vesting and settlement of the RSUs pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 10, 2023. The sale was effected through an automatic "sell to cover" transaction that did not represent a discretionary trade by the Reporting Person.

Footnote F4

Each RSU represents the contingent right to receive one share of common stock of the Issuer.

Footnote F5

Fully vested as of October 25, 2025.