Genentech came out with the first targeted antibody drug for breast cancer almost 15 years ago, and made headlines this week with a “supercharged” version that beats the original. What fewer people may realize is that it’s also gearing up this week to start selling a new and different targeted drug for breast cancer.
The South San Francisco-based company, a unit of Roche, is eagerly awaiting word from the FDA on whether it has the green light to market pertuzumab (Perjeta) in the U.S. as a new therapy for women with breast cancer that overexpresses the HER2 protein. The drug, pronounced per-JETT-uh, is designed to be given in combination with the original trastuzumab (Herceptin) for women who are getting their first round of treatment for metastatic disease, or for those who have suffered a relapse after surgery. The FDA gave this drug’s application a faster-than-usual six-month regulatory review, which it sometimes grants to groundbreaking new therapies. The agency’s deadline to complete its review is Friday.
Getting to the cusp of FDA approval represents a comeback for this drug, which could easily have been tossed on the R&D scrap heap a few years ago. The program stalled in 2005 when Genentech said the drug showed “limited activity” as a single-agent in mid-stage clinical studies against ovarian, breast, and prostate tumors. But the company’s scientists argued that it was worth trying pertuzumab in combination with trastuzumab to see if two targeted therapies for breast cancer might be better than one.
It was a provocative question that Genentech had to spend a lot of time and money to answer. The basic idea is this: The original trastuzumab zeroes in on a target known as HER2 that is abundant on the surface of breast cancer cells in about one-fourth of patients with a gene mutation. It has proven to be effective since winning FDA approval in 1998, but it’s not a cure, and patients eventually develop resistance.
By creating a different Y-shaped antibody that binds to a different location on the HER2 molecule, Genentech hoped to achieve a more comprehensive blockade of members of the HER family of signaling molecules, which are thought to help tumors spread and grow. The bet was essentially that the two drugs together could help hold the cancer in check for a greater percentage of patients, without adding excessive side effects.
Genentech ran 17 clinical studies of pertuzumab, giving the experimental medicine to 1,412 people, Willson says. The most important of those studies was called Cleopatra. That trial
