A Phase I/II, Open-label, Two Part Study of GSK3359609 in Combination With Tremelimumab in Participants With Selected, Advanced Solid Tumors

The purpose of this study is to evaluate if the combination of GSK3359609 and tremelimumab is safe and tolerable (Part 1) and provides significant survival benefit to subjects with relapsed/refractory (R/R) Head and Neck Squamous Cell Carcinomas (HNSCC) to warrant further clinical investigation (Part 2). Part 1 (dose escalation) will enroll subjects with advanced, selected solid tumors. Subjects will receive escalating doses of GSK3359609 and tremelimumab in combination in Part 1. Part 2 is randomized expansion and will enroll subjects with R/R HNSCC who have disease progression after receiving at least 1 platinum-based chemotherapy and at least 1 anti-programmed death receptor protein-1 (PD-1)/anti-programmed death-ligand 1 (PD-L1) therapy, whether in combination or separately. In Part 2, subjects will be randomized in a ratio of 2:1 to receive either GSK3359609 in combination with tremelimumab at the recommended Phase 2 dose or investigators choice of a single-agent standard of care (SOC) therapy including paclitaxel, docetaxel or cetuximab. The total duration of subjects in the study will be approximately 4 years.