Ipilimumab(MDX-010, BMS-734016)is a fully human monoclonal immunoglobulin(IgG1k)specific for human cytotoxic T lymphocyte antigen 4(CTLA-4, CD152), which is expressed on a subset of activated T-cells as a negative regulator of T-cell activation. Blockade of CTLA-4 can potentiate a robust antitumor immune response and lead to long-term tumor regression. Moreover, 2 global phase 3 clinical studies(MDX010-20 and CA184-024)on ipilimumab have demonstrated an improved survival in patients with both untreated and treated advanced melanoma. Ipilimumab(Yervoy TM)has been approved for clinical use for the treatment of advanced melanoma in over 40 countries, including the United States(March 2011)and the European Union(July 2011), as the first agent to show overall survival benefit in patients with advanced melanoma. In Japan, several clinical trials for ipilimumab are ongoing in patients with conditions such as melanoma, non-small cell lung cancer, small-cell lung cancer, and gastric cancer. On the basis of experiences in both clinical development and clinical use of ipilimumab in more than 13,000 patients, several unique features of immunotherapy have been identified. In this article, clinical data on ipilimumab along with its unique effects and safety profile will be introduced, and some possible options for the further development of ipilimumab will be briefly discussed.