Phase 1/2a, open‐label, multicenter study of<scp>RM</scp>‐1929 photoimmunotherapy in patients with locoregional, recurrent head and neck squamous cell carcinoma

Background Recurrent head and neck squamous cell carcinoma (rHNSCC) represents a significant global health burden with an unmet medical need. In this study we determined the safety and efficacy of RM-1929 photoimmunotherapy in patients with heavily pretreated rHNSCC. Methods RM-1929 (anti-EGFR-IR700 dye conjugate) was infused, followed by tumor illumination. We evaluated safety, tumor response, and pharmacokinetics. Results Nine patients were enrolled in Part 1 (dose-finding) and 30 patients in Part 2 (safety and efficacy). No dose-limiting toxicities were experienced in Part 1; 640 mg/m2 with fixed light dose (50 J/cm2 or 100 J/cm) was recommended for Part 2. Adverse events (AEs) in Part 2 were mostly mild to moderate but 19 (63.3%) patients had AE ≥Grade 3, including 3 (10.0%) with serious AEs leading to death (not treatment related). Efficacy in Part 2: unconfirmed objective response rate (ORR) 43.3% (95% CI 25.46%-62.57%); confirmed ORR 26.7% (95% CI 12.28%-45.89%); median overall survival 9.30 months (95% CI 5.16-16.92 months). Conclusions Treatment was well tolerated. Responses and survival following RM-1929 photoimmunotherapy in heavily pretreated patients with rHNSCC were clinically meaningful and warrant further investigation. Clinical trial information NCT02422979.