CTLA4 and melanoma: Both retrospective and prospective phase II and III studies have recently demonstrated a significant antitumor activity of the anti-CTLA-4 blocking antibody ipilimumab in advanced melanoma.19 The response rate in patients with advanced-stage disease who failed previous therapies and had no other potential therapeutic opportunities approached 40% and was translated into an improved survival.20,21 Interestingly, response was accompanied by increase in lymphocyte count and a decrease in regulatory T cells (Tregs).21