The objective of this study is to see if providing an appropriate therapy based on the genomic testing of prostate tumour tissue will result in an improved clinical response. Each participant will be treated with 8 weeks of a luteinizing hormone-releasing hormone agonist (LHRHa) plus apalutamide (APA) while genome sequence characterization is being done. Participants with biopsy specimens deemed unevaluable for genomic testing will remain on LHRHa plus APA for an additional 16 weeks. Participants with evaluable tissue will be assigned to one of the open-label sub-studies on the basis of genomic profiling results. Within each group, they will be randomized to a specific treatment arm either LHRHa plus APA alone or adding abiraterone acetate and prednisone, docetaxel or niraparib. The study will evaluate the response rate and outcomes after radical prostatectomy in each arm of the trial.

This is a multi-centre adaptive multi-arm phase II study. Participants are treated with an induction period of at least 8 weeks of LHRH agonist/antagonist (LHRHa) plus apalutamide (APA) while genome sequence characterization is being done. Genomic sequencing analysis will be performed centrally by Tempus, a CLIA (Clinical Laboratory Improvement Amendments)-certified laboratory. For the DNA gene profiling, formalin-fixed paraffin-embedded (FFPE) prostate cancer and surrounding healthy tissue from diagnostic biopsies will be used for genetic analysis. Copy number profiling will be performed using array Comparative Genomic Hybridisation (aCGH). Targeted sequencing using MiSeq (Illumina) and Ion Proton (Life Technologies) platforms will be performed to identify mutations in a panel of 648 genes. Based on previous studies, we conservatively expect up to 25% of unevaluable needle biopsy specimens with inadequate/insufficient tumor tissue for genome sequencing. The patients with unevaluable tissue will continue on the master protocol (LHRHa + APA) for an additional 16 weeks followed by radical prostatectomy. The genomically evaluable patients will be assigned to a specific sub-protocol according to the results of the genomic profile and randomized to a treatment arm within the sub-protocol for 16 weeks, with additional inclusion and exclusion criteria specified in dedicated sub-protocols. Radical prostatectomy will follow sub-protocol treatment. Sub-protocol 1 - AR axis: No targetable actionable aberration; presence of TMPRSS2-ERG fusion, CHD1 loss or SPOP mutations: (\~50% expected prevalence in study population) randomized to: 1. LHRHa + APA for 16 weeks or 2. LHRHa + APA + AAP (Abiraterone Acetate + Prednisone) for 16 weeks Sub-protocol 2 - Loss of tumour suppressor genes - PTEN, TP53 or TB loss (\~40%, bad prognosis) randomized to: 1. LHRHa + AAP for 16 weeks or 2. LHRHa + AAP + docetaxel for 6 cycles Sub-protocol 3 - DNA damage response alterations (e.g. BRCA1/2, ATM, FANCONI, CDK12) in 6-8% assigned to: * LHRHa + AAP + PARP (Poly \[ADP-ribose\] polymerase) inhibitors (niraparib) for 16 weeks Sub-protocol 4 - Hypermutation, microsatellite instability (MSI), Lynch syndrome or CDK12 in less than 5% assigned to: a. LHRHa + APA plus PD-L1 inhibitor (atezolizumab) for 16 weeks