ImmunoGen Plunges After Phase III Ovarian Cancer Treatment Fails to Hit PFS Endpoint

Shares of Waltham, Mass.-based ImmunoGen, Inc. have plunged nearly 50 percent in premarket trading after the company’s Phase III ovarian cancer treatment failed to meet the primary endpoint of progression-free survival. ImmunoGen’s FORWARD I trial was testing the safety and efficacy of mirvetuximab soravtansine compared to chemotherapy in patients with folate receptor alpha (FRα)-positive, platinum-resistant ovarian cancer. The company said that the late-stage study did not hit its primary endpoint in either the entire study population or in the pre-specified subset of patients with high FRα expression. The 366-patient trial randomized participants 2:1 to receive either mirvetuximab soravtansine or the physician's choice of single-agent chemotherapy (pegylated liposomal doxorubicin, topotecan, or weekly paclitaxel). Data shared from the trial showed that in the entire study population, the confirmed overall response rate was higher for mirvetuximab soravtansine than for chemotherapy, 22 percent vs. 12 percent. ImmunoGen said that was without a significant difference in the primary endpoint of PFS or overall survival.