Talimogene Laherparepvec and Pembrolizumab in Treating Patients With Stage III-IV Melanoma

Inclusion Criteria: * Patients must have pathologically confirmed stage IV or unresectable stage III melanoma; patients must not have disease that is suitable for local therapy, administered with curative intent * Patients must have measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1; contrast-enhanced computed tomography (CT) scans of the chest, abdomen and pelvis are required; a whole body positron emission tomography (PET)/CT scan with diagnostic quality images and intravenous iodinated contrast may be used in lieu of a contrast enhanced CT of the chest, abdomen and pelvis; imaging of the head and neck, or the limbs is required only if the patient has a lesion(s) in these areas; contrast may be omitted if the treating investigator believes that exposure to contrast poses an excessive risk to the patient; if skin lesions are being followed as measurable disease, photograph with a ruler included and physician's measurements, must be kept in the patients chart as source documentation; all measurable lesions must be assessed within 28 days prior to registration; tests to assess non-measurable disease must be performed within 42 days prior to registration.; all disease must be assessed and documented on the baseline tumor assessment form (RECIST 1.1) * Cohort A: Patients must have at least one measurable visceral lesion (per RECIST 1.1); a visceral lesion is any solid organ except for skin, lymph node, and musculoskeletal tissue; at least one of th…