What happened

Shares of ImmunoGen (NASDAQ:IMGN) closed with an 11.98% gain on Wednesday after Mark Goldberg, who is a member of the biotech's board of directors, purchased 30,000 shares for $5.76 each. The $172,800 purchase more than doubled Goldberg's position in ImmunoGen, bringing his share count to 53,800.

So what

As they say, insiders sell for many reasons, but they buy for only one reason: to make money on the investment.

It's unlikely that Goldberg knows anything investors don't. ImmunoGen's near-term value will be based on the results of Forward I, a phase 3 study testing its lead drug, mirvetuximab, as a monotherapy for ovarian cancer. The data will remain blinded to ImmunoGen until the study is complete next year.

But Goldberg's investment certainly appears to be a signal that he sees value in ImmunoGen's shares, especially at this knocked-down price.

Doctor with a clipboard talking to a patient in front of a window

Image source: Getty Images.

Now what

Today's move may have come from investors following Goldberg's lead, but considering how volatile the biotech has been over the past year or more, it's possible the insider buy was just a trigger that gave day traders license to play.

Long-term investors should ignore the daily gyrations and focus on the Forward I data due in the first half of next year, as well as data from ImmunoGen's early-stage pipeline of drugs -- specifically IMGN779 and IMGN632 -- that's scheduled to be presented at the American Society of Hematology meeting in December.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.