Long term survival with cytotoxic T lymphocyte-associated antigen 4 blockade using tremelimumab

Abstract Purpose One of the hallmarks of cancer immunotherapy is the long duration of responses, evident with cytokines like interleukin-2 or a variety of cancer vaccines. However, there is limited information available on very long term outcomes of patients treated with anti-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) antibodies. Tremelimumab is an anti-CTLA-4 antibody of immunoglobulin G2 (IgG2) isotype initially tested in patients with advanced melanoma over 12 years ago. Methods We reviewed the outcomes of patients with advanced melanoma enrolled in four phase 1 and 2 tremelimumab trials at two sites to determine response rates and long-term survival. Results A total of 143 patients were enrolled at two institutions from 2002 to 2008. Tremelimumab administration varied between a single dose of 0.01 mg/kg and 15 mg/kg every 3 months. Median overall survival was 13 months (95% confidence interval (CI), 10–16.6), ranging from less than a month to 12+ years. An objective response rate of 15.6% was observed, with median duration of response of 6.5 years, range of 3–136+ months. The Kaplan–Meier estimated 5 year survival rate was 20% (95% CI, 13–26%), with 10 and 12.5 year survival rates of 16% (95% CI, 9–23%). Conclusions CTLA-4 blockade with tremelimumab can lead to very long duration of objective anti-tumour responses beyond 12 years.