Additional Study Information: The purpose of this study is to test an experimental drug called RMC-6236 (the study drug) for solid tumor cancer with a KRAS mutation. The KRAS protein sends signals that cause cancer cells to grow. RMC-6236 is designed to prevent the KRAS protein from sending these signals, and this blocking action may slow or stop the growth of your cancer cells. RMC-6236 is an experimental drug, which means that it is not approved by the United States (US) Food and Drug Administration (FDA) or any other health authorities. This is the first study in which RMC-6236 will be tested in humans. The safety of different doses of RMC-6236 and how it is processed by your body will be tested. Cancers include: bladder cancer, breast cancer, colon and rectal cancer, esophageal cancer, ovarian cancer, head and neck/oral cancer, kidney cancer, liver cancer, lung cancer, pancreatic cancer, prostate cancer, stomach cancer, testicular cancer, and thyroid cancer.