Safety and Efficacy Findings From a Phase Ib/II Study of ASP‐1929 Photoimmunotherapy With Pembrolizumab in Recurrent and/or Metastatic Head and Neck Squamous Cell Carcinoma

Background ASP‐1929 photoimmunotherapy—cetuximab conjugated to IRDye 700DX and red light (690 nm) for localized drug activation—results in rapid, selective cell killing. Methods This phase Ib/II open‐label study evaluated ASP‐1929 photoimmunotherapy plus pembrolizumab in patients with recurrent/metastatic HNSCC (≥ 1 accessible lesion, PD‐L1 combined positive score ≥ 1, ineligible for standard locoregional therapy). Primary objectives were safety/tolerability and objective response rate (ORR). Secondary objectives included overall survival (OS) and progression‐free survival (PFS). Results Eighteen patients (median age 63 years, 74% male) comprised the photoimmunotherapy‐evaluable population. The confirmed ORR was 27.8% (95% CI 9.7–53.5); four of five responders had complete responses (95% CI, 6.4–47.6). Median OS was 25.6 months (95% CI, 14.6–not evaluable); median PFS was 2.9 months (95% CI, 1.4–14.6). The most common serious adverse reactions were dysphagia and tongue edema (each n = 2; 10.5%). Conclusions ASP‐1929 photoimmunotherapy plus pembrolizumab was generally tolerable, with promising efficacy in patients with recurrent/metastatic HNSCC.