- Previous treatment with a BRAF inhibitor (including but not limited to dabrafenib, vemurafenib, LGX818, and XL281/BMS-908662) or MEK inhibitor (including but not limited to trametinib, AZD6244, and RDEA119) prior to start of study treatment (Note: Prior treatment with dabrafenib is allowed for crossover subjects in Cohort A);