What happened

Shares of ImmunoGen, Inc. (IMGN), a biotech company prone to erratic price swings, fell 15% on Tuesday despite a complete lack of significant news for the company's experimental cancer therapies. A few days earlier, the company dropped some data concerning its lead candidate that investors should have found highly encouraging.

So what 

Unfortunately, it's not at all uncommon for ImmunoGen stock to bounce around without much significant news. This week has been particularly frustrating because the company presented pretty good data from a combination trial over the weekend. Mirvetuximab soravtansine, in combination with Merck & Co.'s (MRK 1.22%) Keytruda, looks like it could be a real winner for ovarian cancer patients that no longer respond to standard treatments. 

Frustrated person looking at stock charts.

Image source: Getty Images.

There were only eight patients who expressed mirvetuximab's target in the study, but the combination shrank tumors for five of them. That's a pretty small population to draw conclusions from, but it certainly warrants a larger study.

Now what

ImmunoGen and Merck don't have a collaboration agreement in place, but an eventual combination approval could be a huge win for the little biotech. If the pair of treatments continues to score high marks, you can expect the big pharma's sales reps to share the good news with their customers at no expense to ImmunoGen.

Of course, ImmunoGen probably won't need the combination study to succeed to get the word out about its lead candidate. It already has mirvetuximab in a pivotal study as a solo therapy for ovarian cancer patients who exhausted other options. The company finished 2017 with enough cash to keep operations humming along until data from the Forward I trial is ready -- probably in the first half next year.