Mersana Therapeutics, Inc. - Common Stock (MRSN)

Mersana Therapeutics reported mixed Q3 2025 results but the key news is its acquisition by Day One Biopharmaceuticals for $25.00 per share.

Mersana surged even as multiple firms downgraded the stock following Day One’s acquisition agreement.

Let's have a look at what is happening on the US markets after the closing bell on Thursday. Below you can find the top gainers and losers in today's after hours session.

Day One Biopharmaceuticals plans to acquire Mersana Therapeutics in a deal worth up to $285 million to expand its cancer drug portfolio.

Shares of Mersana Therapeutics catapulted early Thursday after Day One Biopharmaceuticals agreed to buy it.

The upfront purchase price of $25 alone represents a premium of 182% from Mersana’s closing price on Wednesday.

Let's have a look at what is happening on the US markets in the middle of the day on Thursday. Below you can find the top gainers and losers in today's session.

Today's session on Thursday is marked by notable gaps in various stocks. Stay informed with the gap up and gap down stocks in today's session.

The regular session of the US market on Thursday is now over, but let's get a preview of the after-hours session and explore the top gainers and losers driving the post-market movements.

Mersana shares Phase 1 data on Emi-Le for TNBC and details FDA's Fast Track status for XMT-1660 in advanced HER2-low breast cancer.