Phase II study of the anti-cytotoxic T-lymphocyte-associated antigen 4 monoclonal antibody, tremelimumab, in patients with refractory metastatic colorectal cancer.

Purpose: Safety and efficacy of tremelimumab (CP-675,206), a fully human anti-cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) monoclonal antibody, were assessed in patients with treatment-refractory colorectal cancer.

Patients And Methods: A single-arm, multicenter, phase II trial was conducted in patients with Eastern Cooperative Oncology Group performance status
Results: Forty-seven patients who had received extensive prior therapies (all had received fluoropyrimidines, oxaliplatin, and irinotecan; most [91%] had also received cetuximab) were treated. Grade 3/4 treatment-related adverse events (AEs) were diarrhea (n = 5; 11%), ulcerative colitis (n = 1; 2%), fatigue (n = 1; 2%), autoimmune thrombocytopenia (n = 1; 2%), and hypokalemia (n = 1; 2%), which resolved spontaneously or with interventions. Six patients discontinued because of an AE; two were considered treatment related. Of 45 response-evaluable patients, 44 did not reach second dose (43 progressive disease; one discontinuation). Twenty-one patients (45%) lived >or= 180 days after enrollment. One patient (2%; 90% CI, < 1% to 10%) had a stable pelvic mass and substantial regression in an adrenal mass (partial response). This patient received five tremelimumab doses; response duration was 6 months (enrollment to disease progression, 15 months).

Conclusion: Tremelimumab did not demonstrate clinically meaningful single-agent activity in this patient population, although the number of survivors at 6 months and the one patient with confirmed partial response are potentially interesting. Further study of tremelimumab in combination with other agents may be warranted.