The goal of this clinical study is to learn more about the study drug, GS-5319, its dosing, safety and tolerability in adults with solid tumors, where the participants show a specific gene alteration in the tumor. The gene helps produce methylthioadenosine phosphorylase (MTAP) enzyme. MTAP enzyme helps in normal growth of cells. The primary objectives of the study are to assess the safety and tolerability of GS-5319 in participants with methylthioadenosine phosphorylase (MTAP)-deleted advanced solid tumors and to identify the maximum tolerated dose (MTD)/maximum administered dose (MAD) and/or the recommended dose for expansion (RDE).