This study is testing a new treatment called **PRT3789** for people with advanced or spread-out tumors that have a specific genetic change called **SMARCA4 mutation**. The study will see how safe and tolerable this treatment is, both by itself and when combined with another drug called **docetaxel**. The study will also find the best dose to use in future treatments.

**Key Points:**

• The study is looking for about 186 participants who can complete all visits and tests.
• Participants will go through different stages of testing to find the right dose, and the study will keep going until the best dose is found.
• People with uncontrolled heart problems or other specific health issues cannot join.

To join, participants must have a tumor with a SMARCA4 mutation that cannot be treated with standard treatments. They must also be willing to provide tumor samples and follow the study plan. This study is an open-label study, meaning both the doctors and participants know what treatment is being given.