An experimental antibody-drug conjugate therapy from the Genentech unit of Roche(RHHBY) delayed by more than three months the re-growth of breast cancer compared to the current standard of care, according to a phase III study being presented today at the American Society of Clinical Oncology (ASCO) annual meeting. The drug, known as T-DM1, will be filed for regulatory approval in the U.S. and Europe later this year, Roche said. T-DM1 is a second-generation version of Genentech’s blockbuster breast cancer drug Herceptin. The drug consists of Herceptin (also known as trastuzumab) linked to a tumor-killing chemotherapy payload developed by ImmunoGen(IMGN_).