This clinical trial is focused on studying a type of prostate cancer known as Metastatic Hormone-sensitive Prostate Cancer that is characterized by a deficiency in a gene called PTEN. The study is investigating the effectiveness and safety of a treatment combination involving two medications: Capivasertib and Abiraterone. Capivasertib is a medication taken as a film-coated tablet, and it is being tested alongside Abiraterone, which is already used in treating prostate cancer. Some participants will receive a placebo instead of Capivasertib to compare the outcomes.

The purpose of this study is to compare how well the combination of Capivasertib and Abiraterone works against the combination of a placebo and Abiraterone in patients with this specific type of prostate cancer. The study will monitor how long patients live without their cancer getting worse, which is known as radiographic progression-free survival. Participants will be randomly assigned to receive either the Capivasertib and Abiraterone combination or the placebo and Abiraterone combination. The study will be conducted in a double-blind manner, meaning neither the participants nor the researchers will know who is receiving which treatment until the study is completed.

Throughout the study, participants will take the medication orally and will have regular check-ups to monitor their health and the progression of their cancer. The study aims to provide valuable information on the potential benefits of adding Capivasertib to the treatment regimen for patients with PTEN-deficient metastatic hormone-sensitive prostate cancer. The trial is expected to continue until 2027, with recruitment starting in 2024.