Overall, patients taking Kadcyla lived about 2.6 years, compared with 2 years for patients taking the other drugs.
FDA specifically approved the drug for patients with advanced breast cancer who have already been treated with Herceptin and taxane, a widely used chemotherapy drug. Doctors are not required to follow FDA prescribing guidelines, and cancer researchers say the drug could have great potential in patients with earlier forms of breast cancer
Kadcyla will carry a boxed warning, the most severe type, alerting doctors and patients that the drug can cause liver toxicity, heart problems and potentially death. The drug can also cause severe birth defects and should not be used by pregnant women.
Kadcyla was developed by South San Francisco-based Genentech using drug-binding technology licensed from Waltham, Mass.-based ImmunoGen. The company developed the chemical that keeps the drug cocktail together and is scheduled to receive a $10.5 million payment from Genentech on the FDA decision. The company will also receive additional royalties on the drug's sales.
Shares of ImmunoGen Inc. rose 2 cents to $14.32 in afternoon trading. The stock has ttraded in a 52-wek range of $10.85 to $18.10.