to bind to a different place on the HER2 molecule than trastuzumab, which Genentech has long wagered would provide a more complete blockade of the HER2 tumor-signaling pathway. The two-antibody strategy began to emerge in the medical community at last year’s San Antonio breast cancer conference, when it showed it could help completely wipe out tumors in about 46 percent of breast cancer patients getting prepped for surgery, compared 29 percent who did that well on existing standard of care.
“We have been studying the HER2 pathway for 30 years to bring personalized medicines to people with HER2-positive breast cancer,” said Hal Barron, Genentech’s chief medical officer, in a company statement. “These results show we may soon improve on the current standard of care, Herceptin plus chemotherapy, to further help people with this advanced form of the disease.”
While combining two antibody drugs sometimes raises concerns about adding extra toxicity, that didn’t appear to be a problem in the Cleopatra study. Researchers said that 69 of the 402 patients in the pertuzumab group died, compared with 96 of the 406 patients in the control group. Researchers will have to spend more time following up patients over time to see if the new antibody truly helps patients live longer in a statistically significant way, and if so, how much difference it really makes.
One other question that isn’t really a part of today’s presentation—but which will surely come up with insurers if pertuzumab wins FDA approval—is cost. New antibodies for cancer can sometimes cost as much as $100,000 a year, so insurers are surely going to want to see compelling evidence of benefit before reimbursing physicians for prescribing two expensive drugs instead of just one. But that will be an interesting business question for another day.
