Further studies and ongoing trials suggest that combination immunotherapy, pairing ipilimumab with the programmed cell death 1, PD-1, monoclonal antibody, nivolumab, prolongs progression-free survival in untreated metastatic melanoma patients compared to either nivolumab alone [39] or ipilimumab alone [39–41]. The gene discussed is PDCD1; the disease is metastatic melanoma.