CTLA4 and metastatic melanoma: Since 2011, continued advance in melanoma treatment strategies improved significantly the survival of patients with stage IV disease; the advent of immune checkpoint inhibitors (ICI) targeting programmed cell death protein 1 (PD1) as monotherapy or in combination with cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors ushered in a Copernican revolution in the treatment of metastatic melanoma that rapidly spread to a large spectrum of tumors [1, 2].