A trial to learn how well saruparib works and how safe it is when combined with an ARPI in people with metastatic hormone-sensitive prostate cancer whose cancer has not gotten worse after receiving androgen-lowering treatment with docetaxel or Lu-PSMA but who still have high PSA levels

Prior treatment

• 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.

Other illness

• Hypersensitivity to saruparib, ARPI or any excipients of these products or any contraindication or restriction based on the local label.
• Any known predisposition to bleeding (eg, active peptic ulceration, recent [within6 months] hemorrhagic stroke, proliferative diabetic retinopathy.
• 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.

Lab values

• 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)

Other

• Spinal cord compression or brain metastases unless asymptomatic and stable.

• Participant must be ≥ 18 at the time of signing the informed consent.
• 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.
• 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).