FDA approves breast cancer drug partly developed by ImmunoGen

Federal regulators Friday morning said they approved T-DM1, a promising new breast cancer therapy with potentially serious side effects, for sale in the United States.

Key components of the drug were developed by Waltham biotechnology company ImmunoGen Inc., but the drug is being marketed by its partner, the Genentech division of Swiss drugmaker Roche AG, under the brand name Kadcyla.

Kadcyla was approved for sale to patients with HER2-positive metastatic breast cancer, an aggressive form of the disease, who have received prior treatment with the drug Herceptin along with a chemotherapy. It is the first antibody-drug conjugate for the disease okayed by the Food and Drug Administration.

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The approval comes two and a half years after the FDA surprised ImmunoGen, Genentech, and the patient community by rebuffing a bid to give T-DM1 fast-track status in a “refuse to file” letter that declined to accept an application for accelerated review.

While many patients have been taking the drugs in clinical trials or through so-called compassionate use programs, others have been unable to obtain it, sparking protest against the FDA.

In a statement Friday, the FDA did not address that controversy. But it said Kadcyla is being approved with a “boxed warning” label alerting patients and health care professionals that the drug can cause liver toxicity, heart toxicity and death. The label will also say the drug can also cause severe life-threatening birth defects, and pregnancy status should be verified prior to beginning treatment.

In its press release, ImmunoGen said: “FDA approval of Kadcyla triggers a $10.5 million milestone payment to ImmunoGen. The company also earns royalties on commercial sales of Kadcyla. Genentech is prepared to launch the product imminently.”

Shares of ImmunoGen rose nearly 4 percent to $14.87 on the Nasdaq stock exchange in morning trading.