In his more than 35 years of practice, Dr. Lowell Schnipper has seen a lot of women die from breast cancer. A patient’s options start to dwindle by the time tumor cells set up outposts in the bones, lungs, and other organs, defying all attempts to keep them under control. But in June, when the government approved Perjeta, Schnipper had something new to offer. The drug is one of an innovative class of drugs known as ‘targeted therapies.