This study is looking at how well a new drug called **mevrometostat** works with a medicine named **enzalutamide** in treating a type of prostate cancer known as **mCSPC**. mCSPC stands for metastatic castration-sensitive prostate cancer, which means the cancer has spread but still responds to treatments that lower testosterone. The study is for males who are **ARPI naïve**, meaning they have not taken medicines that block androgens (hormones that help cancer grow). Participants will be divided into two groups: one will receive mevrometostat with enzalutamide, and the other will receive a placebo (a harmless pill) with enzalutamide. This is a **Phase 3 trial**, the last stage before a drug can be approved for public use.

• The study lasts for several months and involves multiple visits for treatment and check-ups.
• Participants will be randomly assigned to one of two treatment groups.
• There are specific health conditions that may exclude some from participating.