A Single Arm, Open-label, Phase II Study to Assess the Efficacy of Pamiparib in Metastatic Castration-Resistant Prostate Cancer Patients With Homologous Recombination Deficiency (HRD) or BRCA1/2 Mutation

• ≥18 years old, male

• Have a histologically or cytologically confirmed adenocarcinoma or poorly differentiated carcinoma without neuroendocrine differentiation of the prostate. Mixed histology is accepted, except for small cell carcinoma.

• Have a deleterious mutation in BRCA1/2 , or HRD score ≥ 9.

• Eastern Cooperative Oncology Group (ECOG) performance status ≤1

• BPI<4

• Metastatic Castration-resistant Prostate Cancer (mCRPC): Presence of measurable target lesion according to RECIST criteria v1.1

• Male subject has been surgically or medically sterilized and has serum testosterone level ≤1.73nmol/L.

• Unsterilized male subject uses an acceptable method of contraception (defined as a barrier method with spermicide) to prevent pregnancy during the duration of the study and for 6 months after the last dose of Pamiparib.

• Experienced disease progression after having received at least 1 prior next-generation androgen receptor-targeted therapies, for metastatic castration-resistant disease.

• Capable of swallowing the whole capsule.

• Subjects must have normal organ and bone marrow function at baseline, as defined below:

• Hemoglobin ≥ 9.0 g/dL at least 28 days after transfusion . Absolute neutrophil count ≥ 1.5 × 10^9/L. Platelet count ≥ 100 × 10^9/L. Total bilirubin ≤ 1.5 × the upper limit of normal (ULN) specified. Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase/alanine aminotransferase (ALT) serum glutamic pyruvic transaminase) ≤ 3 × the specified ULN, unless liver metastases are present, in which case it must be ≤ 5 × ULN.

• Agree to sign informed consent form

• Agree not to participate in other interventional trials during this trial.