What happened

ImmunoGen (IMGN) is up 10.6% at 1:19 p.m. EDT following last night's release of abstracts for this year's American Society of Clinical Oncology (ASCO) meeting and a press release of updated data.

So what

As previously discussed, there are two sets of data that ImmunoGen's investors should be focused on: pooled phase 1 data testing mirvetuximab soravtansine as a monotherapy and combination data from the phase 1b FORWARD II trial testing mirvetuximab soravtansine with other oncology drugs.

Doctor talking to patient

Image source: Getty Images.

The pooled data from multiple phase 1 trials in patients with ovarian cancer are important because a monotherapy treatment is ImmunoGen's shortest pathway to approval of mirvetuximab soravtansine via the ongoing phase 3 FORWARD I trial testing mirvetuximab soravtansine as a monotherapy. In the pooled data, 17 of the 36 patients who met the FORWARD I enrollment criteria showed a response to the drug. There's no control group to compare to, but a 47% response rate seems pretty good considering these patients had failed one to three previous treatments, including a platinum-based chemotherapy. ImmunoGen quotes an oncologist from University of Oklahoma who says response rates for monotherapies of patients with platinum-resistant disease are typically in the 15% to 20% range.

The FORWARD II trial also didn't have a control group, but looked promising for some of the combinations. When mirvetuximab soravtansine was combined with Roche's Avastin in patients with a median of six prior treatments, 29% of patients responded. When combined with carboplatin in patients with a median of three prior treatments, 65% of patients responded. And finally, a combination perhaps not worth pursuing, mirvetuximab soravtansine in combination with Johnson & Johnson's (JNJ -0.43%) Doxil produced a 13% response rate in patients with a median of two prior treatments.

Now what

Normally, ASCO abstracts are out of date by the time they're published since researchers have to turn them in months earlier, but ImmunoGen issued its own separate press release that contained the update data above, so it isn't clear that the data will change that much -- if at all -- when the data is presented in a few weeks on June 3.