Abbreviated MAPK Targeted Therapy Plus Pembrolizumab in Melanoma

Inclusion Criteria: * Participants must have histologically confirmed metastatic or unresectable melanoma. * Participants must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded) as ≥ 20 mm with conventional techniques or as ≥10 mm with spiral CT scan. See section 11 for the evaluation of measureable disease. * Participants may have previously received ipilimumab, adjuvant anti-PD1 therapy, or high-dose IL-2. They may not have previously been treated with BRAF inhibitors (vemurafenib, dabrafenib, encorafenib), MEK inhibitors (selumetinib, trametinib, binimetinib, cobimetinib), and/or anti-PD1/PDL1 monoclonal antibodies for metastatic or unresectable disease. Participants must allow 2 weeks between prior chemotherapy targeted small molecule therapy, or radiation therapy prior to study Day 1 or recovery (i.e., ≤ Grade 1 or at baseline) from adverse events due to a previously administered agent. * Note: Subjects with ≤ Grade 2 neuropathy are an exception to this criterion and may qualify for the study. * Note: If subject received major surgery, they must have recovered adequately from the toxicity and/or complications from the intervention prior to starting therapy * Age greater than or equal to 18 years. Because no dosing or adverse event data are currently available on the use of the combination of trametinib with or without dabrafenib, and pembrolizumab in participants less t…