RSC-1255 is an orally bioavailable, small-molecule direct pan-mutant and wild-type RAS inhibitor. RSC-101 is a Phase 1a/1b, open-label, multi-center, non-randomized, Dose Escalation and Dose Expansion study in participants with advanced solid tumor malignancies. Study enrollment is approximately 134 participants. All participants receive oral RSC-1255, twice daily as monotherapy. Following Phase 1a (Dose Escalation) to identify the Maximum Tolerated Dose and Recommended Dose for use in Phase 1b, additional participants are enrolled in the Phase 1b (Dose Expansion) to further characterize the safety, pharmacology, and the clinical efficacy of RSC-1255 as monotherapy and in combination with the autophagy inhibitor hydroxychloroquine (HCQ).