The immune system plays a vital role in regulating tumor growth, and the oncology community has witnessed an exciting resurgence in clinical research to develop effective immunotherapeutic strategies. The utility of these strategies in advanced melanoma has been at the forefront of these developments. In particular, blockade of programmed cell death protein 1 (PD-1) in advanced melanoma has proven to be a most promising new anticancer strategy. Pembrolizumab is a humanized IgG4 anti-PD-1 antibody that exerts its anti-tumor effect through blocking the interaction of the immune inhibitory molecule PD-1 with its ligands. Its effect has been most convincingly demonstrated in the setting of advanced melanoma, with growing evidence of clinical responses across a broad spectrum of other solid and hematological malignancies.