Addition of SNS-301 to Checkpoint Inhibitor Treatment in Metastatic/Recurrent SCCHN

This is a Phase 1/2, open-label, multi-center trial to evaluate the safety, immunogenicity and preliminary clinical efficacy of SNS-301 delivered intradermally in addition to pembrolizumab in patients with locally advanced unresectable or metastatic/recurrent SCCHN. The trial population consists of patients with locally advanced unresectable or metastatic/recurrent SCCHN who are currently receiving checkpoint inhibitor (CPI) therapy (Cohort A) or are naïve to CPI therapy (Cohort B). Patients who are currently receiving CPI therapy must have a best response of stable disease (SD) or first evidence of progressive disease (PD) after a minimum of 12 weeks of treatment with a CPI. Patients receiving a CPI other than pembrolizumab will be switched over to pembrolizumab at the time of entering this study. Patients receiving pembrolizumab in the first line setting must be PD-L1 positive.