This study is about testing a new medicine called **selpercatinib** (also known as LOXO-292) to see if it's safe and helps fight cancer. It focuses on advanced solid tumors, medullary thyroid cancer (MTC), and tumors with a special change in the RET gene, which can make the cancer grow. **RET fusion-positive** means the gene is joined with another, causing changes in the body. The study is open-label, so everyone knows they're getting the medicine, and it has two parts: Phase 1 to find the right dose, and Phase 2 to test how well it works. Participants take a dose of 160 milligrams twice a day. To join, participants need to have advanced cancer and tried other treatments that didn't work or couldn't use other treatments.
- Participants may need to visit multiple times for tests and check-ups.
- There is a possibility of side effects, but the study helps understand the drug's safety.
- Participants with certain types of cancer or who had specific treatments might not be eligible.