Phase II trial of tremelimumab (CP-675,206) in patients with advanced refractory or relapsed melanoma.

PURPOSE: This phase II study assessed the antitumor activity of tremelimumab, a fully human, anti-CTL-associated antigen 4 monoclonal antibody, in patients with melanoma. EXPERIMENTAL DESIGN: Patients with refractory/relapsed melanoma received 15 mg/kg tremelimumab every 90 days. After 4 doses, patients with tumor response or stable disease were eligible to receive < or =4 additional doses. Primary endpoint was best overall tumor response assessed by an independent endpoint review committee, and secondary endpoints included duration of response, overall survival, progression-free survival, and safety. RESULTS: Of 251 patients enrolled, 246 (241 response-evaluable) received tremelimumab. Objective response rate was 6.6% (16 partial responses); duration of response was 8.9 to 29.8 months. Eight (50%) objective responses occurred in patients with stage IV M(1c) disease, and 11 (69%) were ongoing at last tumor assessment. Eight (3.3%) patients achieved responses in target lesions (Response Evaluation Criteria in Solid Tumors) despite progressive disease within the first cycle. All 8 survived for >20 months; 5 (63%) remained alive. Clinical benefit rate (overall response + stable disease) was 21% (16 partial responses and 35 stable disease), and median overall survival was 10.0 months. Progression-free survival at 6 months was 15%, and survival was 40.3% at 12 months and 22% at 24 months. Common treatment-related adverse events were generally mild to moderate, and grade 3/4 adverse events included diarrhea (n = 28, 11%), fatigue (n = 6, 2%), and colitis (n = 9, 4%). There were 2 (0.8%) treatment-related deaths. CONCLUSIONS: Tremelimumab showed an objective response rate of 6.6%, with all responses being durable > or =170 days since enrollment, suggesting a potential role for tremelimumab in melanoma.

Detailed analysis of immunologic effects of the cytotoxic T lymphocyte-associated antigen 4-blocking monoclonal antibody tremelimumab in peripheral blood of patients with melanoma.

BACKGROUND: CTLA4-blocking antibodies induce tumor regression in a subset of patients with melanoma. Analysis of immune parameters in peripheral blood may help define how responses are mediated. METHODS: Peripheral blood from HLA-A*0201-positive patients with advanced melanoma receiving tremelimumab (formerly CP-675,206) at 10 mg/kg monthly was repeatedly sampled during the first 4 cycles. Samples were analyzed by 1) tetramer and ELISPOT assays for reactivity to CMV, EBV, MART1, gp100, and tyrosinase; 2) activation HLA-DR and memory CD45RO markers on CD4+/CD8+ cells; and 3) real-time quantitative PCR of mRNA for FoxP3 transcription factor, preferentially expressed by T regulatory cells. The primary endpoint was difference in MART1-specific T cells by tetramer assay. Immunological data were explored for significant trends using clustering analysis. RESULTS: Three of 12 patients eligible for immune monitoring had tumor regression lasting > 2 years without relapse. There was no significant change in percent of MART1-specific T cells by tetramer assay. Additionally, there was no generalized trend toward postdosing changes in other antigen-specific CD8+ cell populations, FoxP3 transcripts, or overall changes in surface expression of T-cell activation or memory markers. Unsupervised hierarchical clustering based on immune monitoring data segregated patients randomly. However, clustering according to T-cell activation or memory markers separated patients with clinical response and most patients with inflammatory toxicity into a common subgroup. CONCLUSION: Administration of CTLA4-blocking antibody tremelimumab to patients with advanced melanoma results in a subset of patients with long-lived tumor responses. T-cell activation and memory markers served as the only readout of the pharmacodynamic effects of this antibody in peripheral blood. CLINICAL TRIAL REGISTRATION NUMBER: NCT00086489.

Antitumor activity in melanoma and anti-self responses in a phase I trial with the anti-cytotoxic T lymphocyte-associated antigen 4 monoclonal antibody CP-675,206.

PURPOSE: Cytotoxic T lymphocyte-associated antigen 4 (CTLA4) blockade with CP-675,206, a fully human anti-CTLA4 monoclonal antibody, may break peripheral immunologic tolerance leading to effective immune responses to cancer in humans. A phase I trial was conducted to test the safety of CP-675,206. PATIENTS AND METHODS: Thirty-nine patients with solid malignancies (melanoma, n = 34; renal cell, n = 4; colon, n = 1) received an intravenous (IV) infusion of CP-675,206 at seven dose levels. The primary objective was to determine the maximum-tolerated dose and the recommended phase II dose. RESULTS: Dose-limiting toxicities and autoimmune phenomena included diarrhea, dermatitis, vitiligo, panhypopituitarism and hyperthyroidism. Two patients experienced complete responses (maintained for 34+ and 25+ months), and there were two partial responses (26+ and 25+ months) among 29 patients with measurable melanoma. There have been no relapses thus far after objective response to therapy. Four other patients had stable disease at end of study evaluation (16, 7, 7, and 4 months). Additionally, five patients had extended periods without disease progression (36+, 35+, 26+, 24+, and 23+ months) after local treatment of progressive metastases. Longer systemic exposure to CP-675,206 achieved in higher dose cohorts predicted for a higher probability of response. CONCLUSION: CP-675,206 can be administered safely to humans as a single IV dose up to 15 mg/kg, resulting in breaking of peripheral immune tolerance to self-tissues and antitumor activity in melanoma.