On weak day for biotech stocks, ImmunoGen slides on setbacks for 2 experimental drugs

Shares of cancer drugmaker ImmunoGen slumped Monday as Wall Street digested two hits to the company's drug development pipeline.

On a down day for biotech stocks, ImmunoGen shares sank $1.03, or 10.3 percent, to $8.93 in afternoon trading.

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ImmunoGen said Friday that French drugmaker Sanofi had ended a partnership on a drug called SAR3419, or coltuximab ravtansine. That means Sanofi no longer wants to develop the drug and returned its rights to ImmunoGen.

The company also stopped early human testing of a drug called IMGN289 and would do more preclinical research.

On a conference call, Chief Development Officer Charles Morris said the study was stopped because of "an unexpected safety concern."

RBC Capital Markets analyst Simos Simeonidis said the results are big, surprising setbacks for the company because Sanofi and ImmunoGen had considered both drugs to be promising. In June ImmunoGen reported positive results from a study of coltuximab as a treatment for diffuse large B-cell lymphoma, a cancer that affects a type of white blood cell.

Simeonidis said investors will now focus on mirvetuximab soravtansine, or IMGN853, which the company is studying as a treatment for ovarian cancer and endometrial cancer.

ImmunoGen doesn't have any approved drugs of its own, but it has partnerships with companies including Sanofi, Novartis AG, and Amgen Inc. The company helped develop Kadcyla, a Roche breast cancer drug that was approved in February 2013. Roche had made royalty payments ImmunoGen based on sales of the drug, but ImmunoGen sold the rights to those payments in March. It received $200 million in cash and said it would use that money to fund studies of its drug candidates.

Shares of the Waltham, Massachusetts-based company fell 2.8 percent Friday. As of Friday's close, however, the stock had risen 63 percent in 2015.