WASHINGTON – The Food and Drug Administration has approved a first-of-a-kind breast cancer medication that targets tumor cells while sparing healthy ones.

The drug Kadcyla from Roche combines the established drug Herceptin with a powerful chemotherapy drug and a third chemical linking the medicines together. The chemical keeps the cocktail intact until it binds to a cancer cell, delivering a potent dose of anti-tumor poison.

Cancer researchers say the drug is an important step forward because it delivers more medication while reducing the unpleasant side effects of chemotherapy.