This is an open-label, single-arm, Phase 2 study of pembrolizumab plus platinum and gemcitabine (PG) in subjects with recurrent or metastatic head and neck cancer squamous cell carcinoma (R/M HNSCC). Evaluable 63 subjects with R/M HNSCC will be enrolled for examination of the efficacy and safety of the combination of pembrolizumab (200 mg IV on Day 1 of each 3-week cycle, up to 35 cycles) in combination with platinum (either cisplatin at 35 mg/m2 IV using a split-dose regimen on Day 1 and Day 8 or carboplatin at AUC 5 IV on Day 1 of each 3-week cycle, up to 6 cycles) and gemcitabine at 1250 mg/m2 IV on Day 1 and 8 of each 3-week cycle, for up to 6 cycles as first-line treatment. This study will be conducted in conformance with Good Clinical Practices. Specific procedures to be performed during the trial, as well as their prescribed timelines and associated visit windows, are outlined in the protocol.

This is an open label, single arm, Phase 2 study of pembrolizumab plus platinum and gemcitabine (PG) in subjects with recurrent or metastatic head and neck cancer squamous cell carcinoma (R/M HNSCC) to be conducted in conformance with Good Clinical Practices. Evaluable 63 subjects with R/M HNSCC will be enrolled for examination of the efficacy and safety of the combination of pembrolizumab with PG as first line treatment. The purpose of the study is to determine Pembrolizumab in combination with platinum and gemcitabine chemotherapies would be comparable with or better than the combination of pembrolizumab with platinum plus 5-FU chemotherapies, in terms of objective response rate(ORR), overall survival (OS) and safety as first-line treatment in R/M HNSCC. All subjects will be given pembrolizumab (200 mg IV on Day 1 of each 3-week cycle, up to 35 cycles) in combination with platinum (either cisplatin at 35 mg/m2 IV using a split dose regimen on Day 1 and Day 8 or carboplatin at AUC 5 IV on Day 1 of each 3-week cycle, up to 6 cycles) and gemcitabine at 1250 mg/m2 IV on Day 1 and 8 of each 3-week cycle, for up to 6 cycles. Disease status will be followed by imaging studies at 6 weekly intervals (±7 days) during the first year, and every 9 weeks (±7 days) after the first year, until disease progression, withdrawal of consent, death or end of study. RECIST 1.1 will be used as the primary efficacy endpoint of response rate. Safety will be monitored according to the National Cancer Institute CTCAE Version 5.0. Specific procedures to be performed during the trial, as well as their prescribed times and associated visit windows, are outlined in the protocol under section Schedule of Activities (SoA).