Inclusion Criteria: - Capable of given written informed consent, which includes compliance with the requirements and restrictions listed in the consent form. - Male or female age 18 years or greater; able to swallow and retain oral medication. - BRAF mutation positive melanoma; other BRAF mutation positive tumor types may be considered. - Measurable disease according to RECIST version 1.1. - Eastern Cooperative Oncology Group Performance Status of 0 or 1 for Parts A and B. Subjects with Eastern Cooperative Oncology Group Performance Status of 2 or less may be entered into Part C with approval of medical monitor. - Agree to contraception requirements. - Calcium phosphorus product less than 4.0mmol2/L2. - Adequate organ system function. - Subjects who test positive for Human Papilloma Virus may be enrolled after informed consent regarding discussion of risk of papilloma virus infection. If enrolled these subjects must use condoms for sexual activity, regardless of the use of other contraceptive measures. Exclusion Criteria: - Currently receiving cancer therapy (chemotherapy, radiation therapy, immunotherapy, or biologic therapy). - Prior exposure to BRAF or MEK inhibitors unless approved by the medical monitor. - Received an investigational anti-cancer drug within 4 weeks or 5 half-lives (whichever is shorter) of study drug administration--- at least 14 days must have passed between the last dose of prior investigational anti-cancer drug and the first dose of study drug. - Current use of a prohibited medication or requires any of these medications during treatment with study drug. - Current use of therapeutic warfarin within 7 days prior to the first dose of GSK1120212. - Any major surgery, radiotherapy, or immunotherapy within the last 4 weeks. Limited radiotherapy within the last 2 weeks. - Chemotherapy regimens with delayed toxicity within the last 4 weeks. Chemotherapy regimens given continuously or on a weekly basis with limited potential for delayed toxicity within the last 2 weeks. - Unresolved toxicity greater than National Cancer Institute-Common Terminology Criteria for Adverse Events version 4 Grade 1 from previous anti-cancer therapy except alopecia. - History of retinal vein occlusion, central serous retinopathy or glaucoma. - Predisposing factors to retinal vein occlusion including uncontrolled hypertension, uncontrolled diabetes, uncontrolled hyperlipidemia, and coagulopathy. - Visible retinal pathology as assessed by ophthalmologic exam that is considered a risk factor for retinal vein occlusion or central serous retinopathy. - Intraocular pressure greater than 21mm Hg as measured by tonography. - Glaucoma diagnosed within one month prior to study Day 1. - Presence of active gastrointestinal disease or other condition that will interfere significantly with the absorption, distribution, metabolism or excretion of drugs. - Known human immunodeficiency virus, Hepatitis B or Hepatitis C infection. - Primary malignancy of the central nervous system. - Untreated or symptomatic brain metastasis, leptomeningeal disease or spinal cord compression. Subjects who are on a stable dose of corticosteroids for more than 1 month or off corticosteroids for 2 weeks can be enrolled with approval of medical monitor. Subjects are not permitted to receive enzyme-inducing anti-epileptic drugs. - History of alcohol or drug abuse within 6 months prior to screening. - Psychological, familial, sociological or geographical conditions that do not permit compliance with the protocol. - QTc interval greater than or equal to 480msecs. - History of acute coronary syndromes (including unstable angina), coronary angioplasty, or stenting within the past 24 weeks. - Class II, III, or IV heart failure as defined by the New York Heart Association functional classification system. - Abnormal cardiac valve morphology (subjects with minimal abnormalities can be entered on study with approval from the medical monitor. - Known immediate or delayed hypersensitivity reaction or idiosyncrasy to drugs chemically related to the study drugs or excipients. - Pregnant or lactating female. - Unwillingness or inability to follow the procedures required in the protocol. - Uncontrolled diabetes, hypertension or other medical conditions that may interfere with assessment of toxicity. - Subjects with known glucose 6 phosphate dehydrogenase deficiency.