This study is testing a new drug called **ARX517** for men with a type of prostate cancer that has spread and does not respond to low testosterone levels. This is a phase 1 study, meaning it's the first time the drug is being tested in humans to see if it's safe. The study has two parts: Phase 1a, where different doses of the drug are tried to find the safest amount, and Phase 1b, where more patients are treated to learn more about the drug. Men can join the study if they are 18 or older, have a certain low level of testosterone, and have had at least two treatments for their cancer.

• The study requires multiple visits, as it is done in a few stages to find the best dose.
• Participants must have a history of prostate cancer treatments.
• There may be risks, like potential side effects from the new drug.