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Historical data indicate that the combination of PD-1 antibodies and EGFR inhibitors show synergistic effect in recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC). This study aimed to determine the efficacy and safety of serplulimab (a novel recombinant humanized anti-PD-1 monoclonal antibody) plus HLX07 (a novel anti-EGFR antibody) in patients with R/M HNSCC who had failed platinum-based chemotherapy.

This is an ongoing, open-label, multicentre, two-stage phase 2 study (NCT04297995). Patients with PD-L1 positive (combined positive score ≥1, as determined by immunohistochemistry) and histologically-proven R/M HNSCC who had previously failed platinum-based chemotherapy were recruited. In stage 1, 13 eligible patients were planned to be enrolled and given intravenous infusion of serplulimab 3 mg/kg (every two weeks) in combination with HLX07 600 mg (every week). Treatment responses were evaluated every 6 weeks after the first infusion of study drugs, and statistical analyses were performed 12 weeks after the first infusion in the last patient. If four or more patients respond, this study will proceed to stage 2 (N=30, with the same dose regimen as stage 1) following Simon's Two-stage Optimal Design. Otherwise, an additional 13 patients will be enrolled in stage 1 to receive 3 mg/kg of serplulimab (every two weeks) in combination with HLX07 800 mg (every week). The primary endpoints were objective response rate (ORR, assessed by independent radiological review committee [IRRC] per RECIST v1.1) 18 weeks after the first infusion of study drugs and the proportion of patients suffered from drug related toxicities.

Here we mainly report the results in stage 1. By cut-off date August 25, 2021, 13 eligible Chinese patients were enrolled, with a median age of 52.0 (range: 34.0–68.0) years and a median BMI of 20.4 (range: 13.9–24.6) kg/m². Of the 13 patients, four were non-smokers, eight were ex-smokers and one was a smoker at the time of enrolment; while six were non-drinkers, five were former-drinkers and two were drinkers at the time of enrolment. The ORR assessed by IRRC and investigators were both 38.5% (n=5; 95% CI: 13.9%–68.4%). The DCR assessed by IRRC and investigators were both 76.9% (n=10; 95% CI: 46.2%–95.0%). The median PFS and median OS were not reached. Nine (69.2%) patients experienced grade 3 or worse treatment-emergent adverse events (TEAEs), most commonly hypomagnesaemia (n=4, 30.8%) and rash (n=2, 15.4%). No TEAEs leading to permanent discontinuation of study drugs or death were reported.

The results above demonstrated a manageable safety profile and encouraging efficacy of serplulimab plus HLX07 in patients with R/M HNSCC who had failed platinum-based chemotherapy, supporting a new treatment option that warrants further investigations.