Roche has filed a BLA for trastuzumab-DM1, or T-DM1, seeking approval to market the pioneering conjugated monoclonal antibody to women with treatment-resistant HER2 positive breast cancer. For Roche, T-DM1 represents a potential mega-blockbuster capable of eventually rivaling Herceptin in the market for cancer drugs. And the filing marks a major milestone for the investigators at Genentech and Immunogen who successfully combined a monoclonal antibody with a toxic chemotherapy to single out cancer cells for termination–sparing healthy cells.  

“Conjugated monoclonal antibodies [such as T-DM1] are viewed by thought leaders in oncology as one of the next area[s] of significant innovation for the treatment of cancer,” Andrew Weiss of Bank Vontobel tells the Wall Street Journal.

If granted an accelerated review, Roche could gain marketing clearance in as little as six months to begin treating advanced breast cancer cases. In the meantime, Roche is pursuing an ambitious slate of late-stage trials to build T-DM1 into a major franchise drug. In Phase II, the drug shrank the tumors in one-third of women who had received on average seven prior medicines for advanced HER2-positive breast cancer–making T-DM1 a last line of defense, according to a statement. That argument will help Roche make a compelling case for approval on the basis of mid-stage data.

“While we’ve made great strides in treating HER2-positive breast cancer, there is a group of people whose breast cancer will come back after many treatments, leaving them with very limited options,” says Hal Barron, Roche’s chief medical officer. “Data from studies have shown that T-DM1 shrank tumors in these people, so we are excited to have submitted this application to the FDA in hopes offering a potential new medicine to people with this type of breast cancer.”