This is a first-in-human, phase 1, open-label, multicenter clinical trial designed to evaluate safety, tolerability, pharmacokinetics, biomarkers, pharmacodynamics and preliminary activity of orally administered KST-6051 as monotherapy or in combination with other anticancer agents. The trial seeks to enroll adults with advanced or metastatic KRAS mutant solid tumors including but not limited to pancreatic ductal adenocarcinoma, colorectal cancer, and non-small cell lung cancer whose cancers have progressed after prior therapy or in whom standard therapy was not tolerated. The trial includes a dose escalation phase in which higher doses of KST-6051 will be given in subsequent groups of participants. The trial also includes a dose expansion phase to further investigate KST-6051. Participants can stay in the trial as long as they benefit from the treatment and can tolerate it.