In the Phase 1b safety lead-in portion, up to 12 patients will be enrolled into each cohort and evaluated for dose-limiting toxicities (DLT) during the first 2 cycles of treatment. If investigational products administration in a cohort is deemed safe in the Phase 1b lead-in, enrollment will be expanded into the Phase 2 cohort expansion. Up to approximately 40 patients in each cohort (including those enrolled in the Phase 1b lead-in and those enrolled in the Phase 2 cohort expansion) will be enrolled and treated with avelumab plus chemotherapy in the initial portion of the study and, in future portions of the study, with avelumab plus chemotherapy with or without other anti-cancer immunotherapies.