What happened

Shares of ImmunoGen (IMGN) had fallen 31.3% as of 11:08 a.m. EDT on Wednesday. The plunge began after ImmunoGen announced that the U.S. Food and Drug Administration (FDA) wants it to conduct another phase 3 clinical study of experimental ovarian cancer drug mirvetuximab soravtansine before seeking approval for it.

So what

ImmunoGen announced in March that in its late-stage Forward I clinical trial, mirvetuximab soravtansine failed to meet the primary endpoint of progression-free survival in either the entire group of enrolled patients or the prespecified subset of patients with high folate receptor alpha expression. However, the company had hoped to be able to file for FDA approval based on the drug's meeting secondary endpoints in the study.

Scientist wearing a mark with a dropper and test tubes in the foreground

Image source: Getty Images.

That's not a viable path now. The FDA told ImmunoGen that the data on the secondary endpoints of the Forward I study couldn't be used to support a filing for accelerated approval of mirvetuximab. However, the FDA did provide some guidance for designing another study that could lead to approval for the drug.

ImmunoGen is taking the bad news as well as it can. Chief Medical Officer Anna Berkenblit said, "We appreciate the constructive engagement with [the] FDA and look forward to aligning with the agency on the design of a new registration trial in this population." CEO Mark Enyedy added, "Our meeting with [the] FDA enabled us to clarify a regulatory path forward for mirvetuximab and we are evaluating all avenues to bring this promising therapy to ovarian cancer patients."

Now what

ImmunoGen continues to evaluate mirvetuximab in combination with other drugs. The company will also work with the FDA on finalizing the design of another phase 3 study in hopes of eventually winning approval to treat ovarian cancer.

Cash could be an issue down the road, though. ImmunoGen had close to $270 million in cash and cash equivalents at the end of the first quarter. The company is reviewing its operations to identify potential ways to stretch out its cash now that potential FDA approval for its lead pipeline candidate has been pushed further into the future.