Cobimetinib (formerly GDC-0973/XL518) is a potent, highly selective inhibitor of MEK, also known as mitogen-activated protein kinase kinase. MEK is a serine/threonine kinase that is a component of the RAS/RAF/MEK/ERK pathway. This pathway mediates signaling downstream of growth factor receptors, and is prominently activated in a wide variety of human tumors. In preclinical studies, oral dosing of cobimetinib resulted in potent and sustained inhibition of MEK in RAS- or BRAF-mutant tumor models. Cobimetinib is being developed by Roche and Genentech (a member of the Roche Group) under a collaboration agreement with Exelixis.
Collaboration with Genentech
Exelixis discovered cobimetinib internally and advanced the compound to investigational new drug (IND) status. In late 2006, Exelixis entered into a worldwide co-development agreement with Genentech, under which Exelixis received initial upfront and milestone payments for signing the agreement and submitting the IND. Exelixis was responsible for development of cobimetinib through the initial phase 1 study, and Genentech exercised its option to develop the compound further.
Exelixis is entitled to an initial equal share of U.S. profits and losses, which will decrease as sales increase, and will share equally in the U.S. marketing and commercialization costs. Exelixis is eligible to receive royalties on any sales of the product outside the United States. In November 2013, Exelixis exercised its option under the co-development agreement to provide up to 25% of the total sales force in the United States, should cobimetinib be approved.
In July 2014, Genentech and Exelixis announced positive top-line results from coBRIM, the phase 3 pivotal trial evaluating cobimetinib in combination with vemurafenib in previously untreated patients with unresectable locally advanced or metastatic melanoma harboring a BRAFV600 mutation. coBRIM met its primary endpoint, delivering a statistically significant increase in progression-free survival for the combination as compared to vemurafenib alone. Based on the results from coBRIM, Genentech announced plans to initiate regulatory filings before the end of 2014.
Additional Trials Involving Cobimetinib
Additional phase 1 trials are ongoing assessing the ability to combine cobimetinib with other agents. These novel combinations are being studied in patients with advanced solid tumors. In some of these trials, entry is restricted to patients whose tumors carry specific genetic mutations. For more information on cobimetinib clinical trials, please visit www.ClinicalTrials.gov.