Exelixis (EXEL) announced yesterday on Feb 19, 2015 that the FDA has accepted for priority review Genentech's New Drug Application - NDA - for Cobimetinib in combination with Vemurafenib to treat patients with a rare type of Melanoma with the BRAF V600 Mutation. Exelixis developed cobimetinib on its own to an IND - investigational new drug application - but had reached a deal with Genentech, a division of Roche (RHHBY), back in 2006. At the time of signing the deal Exelixis received upfront milestone payments and additional milestone payments for filing the Cobimetinib IND. Then in 2013 Exelixis agreed to share market and commercialization costs with Genentech in the U.S.

Exelixis will be able to receive royalty sales on the product outside the U.S. according to the deal. 

Cobimetinib is a selective inhibitor that blocks activity of MEK, a protein. This MEK protein is part of a pathway known as the  RAS-RAF-MEK-ERK - that is ultimately responsible for producing cell division and survival. This pathway is activated in many types of cancer but one in particular is in Melanoma. This pathway has a mutation that occurs with the BRAF that causes abnormality in about 50% of tumors. Some current treatments for the BRAF mutation have no effect on the mutated protein. That is because the BRAF protein develops a resistance to those treatments which then allows the disease to progress in the patient's body. Treatment in a study of Cobimetinib together with Vemurafenib was shown to block the resistance of the BRAF mutation. 

Vemurafenib, also known as Zelforab, is Roche's current marketed drug for Melanoma. But the combination of Cobimetinib together with Vemurafenib produced significantly higher progression-free survival - PFS - as compared to Vemurafenib on its own. As a matter in fact, Vemurafenib (Zelforab) produced a PFS rate of 6.2 months while the combination of Cobimetinib together with Vemurafenib produces a PFS rate of 9.9 months. That's roughly, about a 4 months increase in progression-free survival which is a highly significant improvement in patients with Melanoma. This combination drug has received FDA Priority Review and it is schedule to be reviewed by August 11 this year. In addition to seeking approval in the United States, both companies have also submitted a marketing Authorization Application - MAA - to the European Medicines Agency.