ImmunoGen's shares plunge after FDA calls for additional late-stage study of experimental ovarian cancer therapy mirvetuximab soravtansine

Shares in ImmunoGen fell as much as 32 percent Wednesday after the company disclosed that the FDA recommended a new Phase III study of the experimental antibody-drug conjugate (ADC) mirvetuximab soravtansine in patients with high folate receptor (FR) alpha-positive, platinum-resistant ovarian cancer. The agency's advice came during a meeting with ImmunoGen this week to discuss results from the late-stage FORWARD I trial and a potential path to registration for mirvetuximab monotherapy. 

In March, ImmunoGen reported that the 366-patient FORWARD I study had failed to meet its primary endpoint of progression-free survival. As a result, the FDA advised that data generated assessing the secondary endpoints "could not be used to support an application for accelerated approval."

ImmunoGen's 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." She also indicated that the company is "encouraged by the consistent signal of anti-tumour activity and the favourable benefit-risk profile" in patients with high FR-alpha expression in the FORWARD I trial. 

Meanwhile, CEO Mark Enyedy said "the mirvetuximab combination cohorts continue to advance and, with approximately $270 million on the balance sheet as of the end of [the first quarter], we remain focused on developing innovative ADC therapeutics." During its financial results presentation earlier this month, ImmunoGen said it was conducting an operational review of the business with the aim of extending its cash runway. 

According to ImmunoGen, mirvetuximab soravtansine, formerly known as IMGN853, uses a humanised FR-alpha-binding antibody to target the ADC specifically to FR-alpha-expressing cancer cells, and the DM4 anti-tumour agent to destroy targeted cancer cells. 



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