What happened

Shares of ImmunoGen (NASDAQ:IMGN) were jumping 13.2% higher as of 3:11 p.m. EDT on Wednesday. The company didn't report any news. Instead, ImmunoGen's gains appeared to reflect continued interest from investors following the biotech's announcement last week of positive initial data from the Forward II phase 1/2b study evaluating mirvetuximab soravtansine in combination with Avastin as a treatment for ovarian cancer.

So what

ImmunoGen stock is up close to 30% since its May 13 update for the Forward II study. The initial results showed that the combination of mirvetuximab and Avastin demonstrated promising anti-tumor activity as well as a favorable safety profile. 

Scientist looking through a microscope

Image source: Getty Images.

The most notable result was a confirmed overall response rate of 61% in patients with high folate receptor alpha expression. Several types of cancer, including ovarian cancer, are often linked with expression of the protein.

But why are investors so excited about initial results from a phase 1/2b study? Probably because the encouraging data increases the level of confidence about the prospects for positive results for the late-stage Soraya study evaluating mirvetuximab as a monotherapy in treating platinum-resistant ovarian cancer. 

Now what

ImmunoGen continues to enroll patients in the Soraya study. Results from this study, which aren't expected until the middle of next year, could be a major catalyst for the biotech stock. In the meantime, the company plans to present updated data from the Forward II study in the fall of 2020 and should file for FDA approval to begin a phase 1 study of IMGC936 by the end of June.