Safety

The most common adverse events (AEs) regardless of attribution to study treatment in the 128 patients treated to date were: non-acneiform rash (35% [2% ≥ Grade 3] for vemurafenib-progressors; and 89% [13% ≥ Grade 3] for BRAFi-naïve), diarrhea (48% [3%]; 81% [8%]), photosensitivity/sunburn (48% [3%]; 70% [0%])), fatigue (28% [2%]; 67% [10%]), nausea (32% [3%]; 56% [3%]), arthralgia (11% [2%]; 48% [11%]), CPK elevation (15% [2%]; 43% [3%]), fever (14% [0%]; 43% [2%]), peripheral edema (20% [0%]; 41% [0%]), vomiting (19% [2%]; 37% [0%]), and acneiform rash (12% [2%]; 33% [3%]). Selected AEs were: choreoretinopathy (2% [0]; 9% [0%]), cardiomyopathy [0% [0%]; 2% [2%]), and squamous cell carcinoma/keratocanthoma (8% [6%]; 10% [5%]).

Temporary interruptions in vemurafenib, cobimetinib, or the combination of both agents were reported in 20%, 20%, and 19% of the 65 vemurafenib-progressor patients, respectively. Dose reductions were reported in 5% 3%, and 3% of vemurafenib-progressor patients, respectively, and permanent discontinuation was reported for vemurafenib (3%) only. Among the 63 BRAFi-naïve patients, temporary interruptions in vemurafenib, cobimetinib, or the combination of both agents were reported in 67%, 49%, and 46%, and dose reductions were reported in 19%, 16% and 2% of patients, respectively. Permanent discontinuation of cobimetinib was reported for one BRAFi-naïve patient (2%). None of the 128 patients receiving the combination of vemurafenib and cobimetinib discontinued treatment due to an adverse event to date.

About Cobimetinib (GDC-0973/XL518)

Cobimetinib is an inhibitor of MEK, 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 sustained inhibition of MEK in RAS or BRAF mutant tumor models. Cobimetinib is being developed by Genentech, a member of the Roche Group under a collaboration agreement with Exelixis.

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