798 Safety, tolerability, and immunogenicity of mRNA-4157 in combination with pembrolizumab in subjects with unresectable solid tumors (KEYNOTE-603): an update by Aaron Scott, Manish Patel, Julie Bauman, Jeffrey Clarke, Howard Burris, Justin Gainor, Martin Gutierrez, Daniel Cho, Ricklie Julian, Pamela Cohen, Joshua Frederick, Celine Robert-Tissot, Honghong Zhou, Kinjal Mody, Karen Keating, Robert Meehan