Cytotoxic T lymphocyte-associated antigen 4 blockade with ipilimumab: Long-term follow-up of 179 patients with metastatic melanoma.

Abstract

8544 Background: We have previously shown objective clinical responses in patients with metastatic melanoma treated with CTLA-4 blockade using ipilimumab. We have treated 179 patients in 3 separate clinical trials and now have long-term follow-up to evaluate the durability and unique features of this immunotherapy. Methods: A total of 179 patients with metastatic melanoma were treated in 3 trials: In Protocol 1, 56 patients received ipilimumab with gp100 peptide vaccines. In Protocol 2, 36 patients received ipilimumab with high-dose interleukin-2 (IL-2). In Protocol 3, 87 patients received intra-patient dose escalation of ipilimumab and were randomized to receive gp100 peptides. We have updated and analyzed the follow-up and survival data for these trials. Results: With median follow-up for Protocol 1, 2, and 3 being 80, 71, and 60 months, median survival was 15, 16, and 13 months, respectively. Objective tumor regression was 12% for Protocol 1, 25% for Protocol 2, and 21% for Protocol 3. Patients in Protocol 2 had a 17% complete response rate (6 patients: 77+, 74+, 72+, 71+, 71+, and 69+ months), as compared to 7% in Protocol 1 (4 patients: 82+, 81+, 79+, and 66+ months) and 8% in Protocol 3 (5 patients: 64+, 63+, 62+, 60+, and 55+ months); all complete responses are ongoing. Many patients who eventually became complete responders had continual tumor shrinkage after stopping therapy. Conclusions: CTLA-4 blockade with ipilimumab can achieve durable objective tumor regression in patients with metastatic melanoma. The combination of ipilimumab and IL-2 appears to have an increased complete response rate, although this needs to be tested in a prospective randomized trial. This report represents the largest single-institution experience with the longest follow-up for this agent; our results support its role as a viable treatment option for patients with metastatic melanoma. No significant financial relationships to disclose.