BioPharma

ImmunoGen shares tank on ovarian cancer trial failure

Although an improvement in progression-free survival was shown in patients with high expression of the drug's target, it did not reach statistical significance. The company's shares lost half their value Friday.

Shares of a company developing biotech drugs designed to deliver small-molecule pharmaceuticals lost about half their value Friday after it announced the failure of a late-stage clinical trial in ovarian cancer.

Waltham, Massachusetts-based ImmunoGen said its Phase III FORWARD I trial of mirvetuximab soravtansine – an antibody-drug conjugate – failed to show that the drug, when administered as a single agent, improved patients’ survival without their disease getting worse, also known as progression-free survival. The trial was in patients with ovarian cancer whose disease expressed folate receptor alpha, also known as FRA, and was resistant to platinum-based chemotherapy.

Shares of ImmunoGen were down more than 46 percent on the Nasdaq Friday following the news.

Physicians had seen FRa as a promising target in ovarian cancer, and it had been subject to significant research. In particular, the drug had worked very well when combined with other agents. Indeed, prior data had shown strong activity for the drug. Data presented in October from the Phase Ib FORWARD II trial on a subset of 54 ovarian cancer patients receiving a combination of mirvetuximab soravtansine with Merck & Co.’s PD-1 checkpoint inhibitor Keytruda (pembrolizumab) showed 83 percent experienced tumor shrinkage. High response rates were also observed among other subsets in FORWARD II, who received the ImmunoGen drug together with Roche’s Avastin (bevacizumab) or the chemotherapy drug carboplatin.

“Even though FORWARD I did not meet its primary endpoint, I continue to be impressed with the efficacy and tolerability of mirvetuximab soravtansine in ovarian cancer patients, especially in the subset with high FRa expression,” University of Oklahoma Stephenson Cancer Center associate director of clinical research Dr. Kathleen Moore said in a statement on behalf of ImmunoGen. “I look forward to continuing to work with ImmunoGen to analyze the Phase III data and determine the most appropriate path to bringing mirvetuximab soravtansine to those patients who benefit most from it.”

Patients with high FRa expression accounted for 218 of the total 366 patients, and progression-free survival was indeed longer for those who received mirvetuximab soravtansine than it was for those who received chemotherapy. Ordinarily, in randomized clinical trials, statistical significance is indicated by a p-value of 0.05 or lower. In the case of high FRa-expressing patients in FORWARD I, the p-value was 0.049. Nevertheless, the study’s design was such that because the overall trial result did not reach statistical significance, p-values in patient subset groups – including those with high expression – could not exceed 0.025, meaning the progression-free survival result was also not statistically significant.

Photo: pictafolio, Getty Images

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