Checkpoint blockade has revolutionized the treatment of melanoma; however, it benefits only the minority of patients. Several agents have been combined with immunotherapy to improve T-cell activation and persistence including growth factor, chemotherapy, and radiation. Preclinical data suggest that temozolomide, which metabolizes to the same active compound as dacarbazine, selectively depletes regulatory T cells. This potential immunomodulatory effect of temozolomide provides rationale for combination with ipilimumab. We performed an open-label single-arm phase II study of ipilimumab plus temozolomide in the frontline setting for patients with metastatic melanoma and LDH ≤2× upper limit of normal. Ipilimumab was given at 10 mg/kg on day 1 and temozolomide 200 mg/m2 orally days 1-4 every 3 weeks for four doses followed by maintenance ipilimumab every 12 weeks plus temozolomide every 4 weeks. The primary objective of the study was 6-month PFS. A total of 64 patients were enrolled and the 6-month PFS was 45% with median OS of 24.5 months. There were 10 (15.6%) confirmed partial responses and 10 (15.6%) confirmed complete responses. Duration of response amongst responders is 35 months with 10 patients demonstrating an ongoing response at median follow-up of 20 months. There were no deaths or unexpected toxicities on study. The most common gastrointestinal side effects were nausea and constipation rather than diarrhea or colitis. These results suggest that the combination of induction ipilimumab plus temozolomide could potentially be an effective strategy to enhance antitumor activity with a manageable toxicity profile. These findings warrant further evaluation in a large prospective study.
Keywords: Clinical trial; Ipilimumab; Melanoma; Regulatory T cells; Temozolomide.