Roche and Exelixis tout PhI cancer combo with late-stage data on the way

South San Francisco biotech Exelixis ($EXEL) and partner Roche ($RHHBY) say their in-development combo treatment for melanoma extended survival in an early-stage trial, setting the stage for Phase III results that could make or break the treatment's future.

In a 129-patient Phase Ib trial, a combination of Exelixis' cobimetinib and Roche's Zelboraf charted an 87% overall response rate in melanoma sufferers who had never been treated with BRAF-blocking treatments. BRAF-inibitor-naive patients taking the combo charted median progression-free survival of 13.7 months, beating out the 2.8 months for those already treated with Roche's drug.

The study hasn't run long enough to get full overall survival numbers, but the duo estimates an 83% one-year survival rate for the former group of patients compared to a 32% clip for the latter.

Exelixis CEO Michael Morrissey

Those are "encouraging signs of clinical activity," Exelixis CEO Michael Morrissey said in a statement, but the big catalyst is due later this year, when Roche expects to unveil top-line data from a Phase III trial pitting a cobimetinib-Zelboraf cocktail against the old drug alone in patients with no BRAF-blocking history. That study, dubbed coBRIM, will determine whether Roche follows through on its plans to submit the drug for approvals this year.

Exelixis discovered cobimetinib in-house and advanced it to the IND stage before signing a deal with Roche's Genentech, reaping $40 million up front with the chance to pocket more milestones down the line. The drug works by shutting down the kinase MEK, a pathway that regulates growth factor receptors and plays a hand in helping tumors proliferate.

The biotech could use a bit of good news after its prostate cancer treatment cabozantinib ran afoul of investors last month. Exelixis reached a pre-specified interim analysis point in its Phase III study of the drug, and, finding no problems or runaway successes, decided to stay the course. Some investors, however, were banking on a positive early termination, and their frustration sent the company's shares down nearly 40%.

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