Saruparib in Combination With Physician's Choice of ARPI in Patients With mHSPC Previously Treated With Docetaxel or 177Lu-PSMA Therapy Without Disease Progression and PSA ≥ 0.2 ng/mL (EvoPAR-PR05)

Inclusion Criteria: * Participant must be ≥ 18 at the time of signing the informed consent. * Histologically documented diagnosis of prostate adenocarcinoma that is de novo or recurrent and hormone-sensitive. * Metastatic disease confirmed prior to initiation of previous treatment with docetaxel or Lu-PSMA-containing regimens for mHSPC. * Previous treatment with docetaxel (IV, Q3w)- or Lu-PSMA (IV, Q6w) with last dose within past 6 months. * Participants must have the following: * Must be receiving ADT with a GnRH analogue or has undergone bilateral orchiectomy. * Had no evidence of disease progression * Had all toxicities related to docetaxel- or Lu-PSMA-containing treatment (except for alopecia and peripheral neuropathy) resolved to CTCAE Grade 1 or lower. * PSA ≥ 0.2 ng/mL within 14 days prior to randomization. * Serum testosterone \< 1.7 nmol/L or 50 ng/dL. * Palliative radiotherapy for symptoms management will be permitted and is to be completed at least 4 weeks prior to randomization for wide field radiation therapy and at least 2 weeks prior to randomization for limited field radiation therapy. * Provision of a FFPE tumor tissue sample and a blood sample (for ctDNA). * Confirmed HRRm, HRD and PTEN status. * Adequate organ and bone marrow function. * Minimum life expectancy of 6 months. * Male, assigned at birth, inclusive of all gender identities. * Contraceptive use by participants or participant partners should be consistent with local regulations. * Capable of giving signed informed consent. * \- - Exclusion Criteria: * Hypersensitivity to saruparib, ARPI or any excipients of these products or any contraindication or restriction based on the local label. * Any history of persisting (\> 2 weeks) severe cytopenia due to any cause (eg, ANC\< 0.5 × 10\^9/L or platelets \< 50 × 10\^9/L) * Any known predisposition to bleeding (eg, active peptic ulceration, recent \[within6 months\] hemorrhagic stroke, proliferative diabetic retinopathy. * Spinal cord compression or brain metastases unless asymptomatic and stable. * History of MDS/AML or with features suggestive of MDS/AML * History of another primary malignancy, with some exceptions. * Any chronic gastrointestinal diseases or conditions including inability to swallow the formulated product that would preclude adequate absorption of any study drug. * History of seizure or predispose to seizure, including any history of loss of consciousness or transient ischemic attack within 12 months of enrolment. * Serious, uncontrolled medical disorder, non-malignant systemic disease or active, uncontrolled infection. * Major surgical procedure or significant traumatic injury within 4 weeks of the first dose or an anticipated need for major surgery during the study. * Switched ARPI agent in previous treatment for mHSPC due to disease progression. Note: if the ARPI agent was switched due to any reason other than disease progression and switch was prior to ICF signature, participants will be eligible. * Any prior treatment with a PARPi or platinum chemotherapy. * \- -