Part D allocation for 1 cohort will be randomized.
This is a first-in-human (FIH) study to evaluate the safety and tolerability and to determine the maximum tolerated dose (MTD) and/or the recommended Phase 2 dose (RP2D) of GS-1811 as monotherapy and in combination with Zimberelimab in participants with advanced solid tumors.~This study will be conducted in 4 parts (Part A and Part B: monotherapy, Part C and Part D: combination therapy), in participants with advanced solid tumors who have received, been intolerant to, or been ineligible for all treatments known to confer clinical benefit.