Genentech, ImmunoGen Breast Cancer Drug Extends Lives

Xconomy San Francisco — 

Genentech’s new souped-up antibody drug for breast cancer was the star of the show at the American Society of Clinical Oncology’s big conference in June, even though the clinical data wasn’t yet fully baked. But now the data is in, and confirms what most everybody thought it would show—that the drug is extending lives.

South San Francisco-based Genentech, a unit of Roche, said late last night that trastuzumab emtansine (T-DM1) significantly extended the lives of women with breast cancer who overexpress the HER2 protein. The finding came from the study known as Emilia, which enrolled 991 women who previously had gotten treatment with Genentech’s original anti-HER2 antibody, trastuzumab (Herceptin), and a taxane chemotherapy. The company didn’t disclose how much longer patients lived on the new drug compared with those who got GlaxoSmithKline’s lapatinib (Tykerb) and Roche’s capecitabine (Xeloda), but it said details will be presented at an upcoming medical meeting.

The drug is important not just for the patients who stand to live longer, but also for scientists, because of the novel way it works. Like the original trastuzumab that was introduced to the U.S. market in 1998, the treatment is designed to seek out diseased cells and mostly spare healthy cells. The big difference is that T-DM1 is also linked to a toxin that gives it extra tumor-killing punch. Scientists have been trying to make anti-cancer antibodies like this for decades, but only recently have overcome some key technical hurdles to make this possible.

Genentech, encouraged by early data showing the drug’s ability to slow the spread of tumors, has already submitted an application to the FDA for clearance to start marketing the new drug for breast cancer, and the regulatory agency could give it the green light in the first half of 2013, said Simos Simeonidis, an analyst with Cowen & Co. in New York. Over time, the drug has potential to reach Herceptin’s level of worldwide sales, at about $5.4 billion, he said. That’s important not just for Genentech, but for Waltham, MA-based ImmunoGen (NASDAQ: IMGN), which is in line to collect a mid-single digit percentage royalty on sales of the drug under a technology license.

“Our consultants view T-DM1 as an ‘extraordinarily efficacious drug,’ with an ‘unusually benign safety profile’” Simeonidis said in a note to clients. “We believe that once approved, T-DM1 will rapidly take over a significant portion of Herceptin’s market share in the metastatic setting.”

Even though the detailed stats on the drug’s survival advantage weren’t released today, it’s a safe bet that it will be substantial by cancer drug standards. Back in June at the ASCO conference, Genentech reported preliminary results that showed 65.4 percent of the T-DM1 patients were still alive after two years of follow-up, compared with 47.5 percent of patients on the combo of GlaxoSmithKline’s lapatinib (Tykerb) and capecitabine (Xeloda) chemotherapy.