GSK2118436 is an orally administered, potent and selective small molecule BRAF inhibitor that is being developed for the treatment of BRAF mutation-positive tumors. This is a 4-part study (in 4 separate cohorts of subjects) designed to examine the interaction potential of GSK2118436, either as a perpetrator (i.e., effect of GSK2118436 on warfarin; Part A) or victim (i.e., effect of other drugs on GSK2118436; Part B: ketoconazole and Part C: gemfibrozil), as well as to evaluate the single and repeat dose pharmacokinetic parameters of GSK2118436 (Part D). A sufficient number of subjects will be screened to obtain approximately 12 evaluable subjects each for Part A, Part B, Part C and Part D. Following completion of this study, subjects may continue dosing with GSK2118436 in the roll-over study, Protocol BRF114144.