Phase I Trial of Cetuximab, Radiotherapy, and Ipilimumab in Locally Advanced Head and Neck Cancer

Purpose: Concurrent radiotherapy with cetuximab, an anti-EGFR mAb, is a standard treatment for locally advanced head and neck squamous carcinoma (HNSCC). Cytotoxic T lymphocyte antigen-4–positive (CTLA-4^þ) regulatory T cells (Treg) dampen cellular immunity and correlate negatively with clinical outcomes. This phase I study added ipilimumab, an anti–CTLA-4 mAb, to cetuximab-radiotherapy. Patients and Methods: A (3 þ 3) design was used to establish the recommended phase II dose (RP2D) of ipilimumab, added at week 5 for four, every-3-week doses to fixed, standard cetuximab-radiotherapy. Eligible subjects had stage III to IVb, high-risk [human papillomavirus–negative (HPV^-)] or intermediate-risk HPV-positive (HPV^þ)] HNSCC. Dose-limiting toxicity (DLT) was defined as any grade 4 adverse event (AE) except in-field radiation dermatitis or immune-related (ir) AE requiring ≥2 weeks of systemic steroids. Baseline tumor and serial blood specimens were collected for immune correlatives. Results: From July 2013 to May 2016, 18 patients enrolled. Two of 6 in cohort 1 (ipilimumab 3 mg/kg) experienced grade 3 dermatologic DLTs, triggering deescalation of ipilimumab to 1 mg/kg. Dose level -1 was expanded to N = 12 without DLT. irAE included: grade 1, 2, and 3 dermatitis (2, 1, and 3 cases), grade 4 colitis (1), and grade 1 hyperthyroidism (1). Three-year disease-free survival (DFS) and overall survival were 72% [90% confidence interval (CI), 57–92] and 72% (90% CI, 56–92). High expression of coinhibitory receptors PD1/LAG3/CD39 on baseline tumor-infiltrating Treg was associated with worse DFS (HR = 5.6; 95% CI, 0.83–37.8; P = 0.08). Conclusions: The RP2D for ipilimumab plus standard cetuximab–radiotherapy is 1 mg/kg in weeks 5, 8, 11, and 14. The regimen is tolerable and yields acceptable survival without cytotoxic chemotherapy.