A Study of Metastases Free Survival With Saruparib vs Placebo Added to a Standard RT/ADT in Men With High-risk Prostate Cancer With a BRCA Mutation

Inclusion Criteria: * Male participants with a histologically documented diagnosis of prostate adenocarcinoma. * Newly diagnosed high-risk and very high-risk (localised/locally advanced) prostate cancer or a high-risk biochemical recurrence (BCR) following radical prostatectomy. * Provision of a formalin fixed and paraffin embedded (FFPE) tumour tissue sample. * Confirmed BRCA1 or BRCA2 mutation status by central tumour tissue is required for enrolment. * Participants required to have a computed tomography (CT) or magnetic resonance imaging (MRI) and a bone scan following the completion of their planned RT. This screening scan must confirm no evidence of disease or evidence of disease confined to the pelvis (M0). * Participants required to have a prostate-specific membrane antigen-positron emission tomography (PSMA-PET) following the completion of their planned RT. This screening scan must confirm no evidence of disease or evidence of disease confined to the pelvis (M0). * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 with no deterioration over the 2 weeks prior to randomization. * Minimum life expectancy of 12 months. * Adequate organ and bone marrow function as described in study protocol. * All participants will have received either primary or salvage RT. Participants must be eligible for randomisation within 10 months of initial diagnosis (de novo or BCR). Radiotherapy administered to the prostate (± pelvis) either in the primary or salvage setti…