This Phase 1/2a study, known as the TRESR Study, is investigating the safety, how the body processes and responds to the drug (pharmacokinetics and pharmacodynamics), and the early effectiveness of RP-3500 (camonsertib) in treating advanced solid tumours with specific genetic mutations. RP-3500 will be tested both on its own and in combination with talazoparib (a PARP inhibitor) or gemcitabine (a chemotherapy drug) to determine its potential in fighting tumours.