Plexxikon, Roche Drug Extends Lives in Patients With Deadly Skin Cancer

1/19/11Follow @xconomy

Good news just crossed the wire from one of the Bay Area’s emerging cancer drug developers. Berkeley, CA-based Plexxikon said its experimental drug for a deadly form of skin cancer met its goal of helping keep tumors from spreading, and helping patients live longer, when compared directly to standard chemotherapy.

Plexxikon, which is developing PLX4032 along with Roche, spread the word after an interim analysis of results from a clinical trial of 675 patients. This study, known as BRIM3, randomly assigned patients with melanoma that has spread through the body to get either Plexxikon’s experimental drug or dacarbazine, a standard chemo drug. Patients in this study had to have a mutated form of BRAF, a protein implicated in uncontrolled cell division, which the Plexxikon drug is specifically designed to block. About half of melanoma patients are thought to have the mutated protein that makes them eligible for the drug.

The company didn’t release details on how much longer patients are living on the Plexxikon drug. It said the safety profile was consistent with results from prior studies. Patients who enrolled in the chemo group will now be able to “cross over” to the other arm of the study, to get the Plexxikon treatment. Full details of the study will be presented at a major medical meeting this year, and Plexxikon plans to seek FDA approval this year for clearance to start marketing the drug in the U.S.

“This positive effect on overall survival represents a significant development for melanoma patients,” said Peter Hirth, Plexxikon’s CEO, in a statement. “As a novel, first-in-class, personalized medicine, together with its companion diagnostic, PLX4032 sets the stage for a strong foundation for Plexxikon’s commercial franchise in oncology.” Hal Barron, the chief medical officer of Roche’s Genentech unit, said in a statement that the results represent the first time a personalized medicine has shown a significant survival benefit for melanoma patients. “This is an important advance,” he said.

This drug, and this trial, are among the most high profile studies of the moment in oncology, where there are said to be 800 new drugs in development. That’s because initial results from a study of 32 patients with metastatic melanoma, published in the New England Journal of Medicine in August, showed that 81 percent of patients had partial or complete tumor shrinkage, and they stayed in remission for a median time of seven months. That kind of response rate is unheard of in a vicious malignancy like melanoma, in which doctors are more accustomed to seeing 10 to 15 percent response rates.

Peter Hirth and Kathy Glaub

The findings were so powerful, in fact, that The New York Times ran a story in September questioning whether it was ethical to run a trial like BRIM3 — designed to give half of the patients a chemo drug that doesn’t work very well when PLX4032 clearly looked like a potent new therapy for patients who are dying.

Patients in the Plexxikon/Roche study took either a twice-daily pill, or an intravenous infusion of the chemo drug, every three weeks. The study started in December 2009.

Evidence has been mounting in favor of PLX4032 since the big New England Journal paper in August. Plexxikon reported on a mid-stage study back in November that showed that about half (52 percent) of 132 patients on the new drug had their tumors shrink at least by half. There was no control group in that study.

It’s still too early to draw conclusions about how long-lasting the effect is—which is always a vital question to ask in cancer, where many drugs that initially look effective eventually underwhelm doctors and patients as the tumors find a way to resist the new drug. Marty Tenenbaum, the founder of an open-source Cancer Commons that is seeking to capture all kinds of data on individual melanoma patients, said he’s beginning to hear reports of patients who are relapsing after their initial responses to PLX4032.

Plexxikon, of course, knows more about the body of evidence behind its drug than anybody at this point. And it showed a strong vote of confidence earlier this month when it opted to set up its own sales force to co-promote the product in the U.S. along with Roche’s Genentech unit in South San Francisco.

Plexxikon’s president, Kathy Glaub, pointed to the co-promotion deal with Genentech as a sign of bigger things to come. “That gives you an idea in terms of our confidence in this drug, and what we think is going to happen in terms of development,” she said last week during a meeting at the JP Morgan Healthcare Conference.

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