This study is testing a drug called **axelopran** for people with advanced cancer who take opioids (strong pain medicines). The goal is to see if axelopran helps control cancer, improves bowel function, and is safe for long-term use. Participants will take axelopran pills every day for up to a year and go to 10 study visits. Each visit lasts 1-2 hours and includes exams, blood tests, and surveys. Patients must have certain types of advanced cancer, like lung, breast, pancreas, or prostate cancer, that hasn't responded to other treatments. They must be able to delay new cancer treatments until day 43 of the study to check if the cancer has changed. Patients should report on their bowel movements and other health details.

• Study lasts up to 1 year with daily medication and 10 visits.
• Participants must have certain advanced cancers and be on opioids.
• Safety and impact on cancer and bowel function are being tested.