Dalpiciclib Isethionate Tablets Combined With Abiraterone Acetate Tablets (I) and Prednisone Tablets (AA-P) Versus Placebo Combined With AA-P in Treatment of High-volume, Metastatic, Hormone-sensitive Prostate Cancer (mHSPC)

Inclusion criteria

• Age of ≥ 18 years old,male
• ECOG PS score of 0 or 1；
• Prostate adenocarcinoma confirmed by histological。
• ADT no more than 3 months prior to randomization (when docetaxel is not used) with no radiographic or PSA progression
• Receiving or maintaining androgen deprivation therapy (ADT) during the planned study period, i.e. continuous treatment with luteinizing hormone-releasing hormone analogues (LHRHA) (drug castration) or prior bilateral orchiectomy (surgical castration)
• Voluntarily participate in this clinical trial, understand the study procedure and have signed informed consent

Exclusion criteria

• Previous ADT, chemotherapy, surgery, external radiation exposure, brachytherapy, radiopharmaceuticals, or experimental topical treatments (eg, radiofrequency ablation, cryoponic, high-energy focused ultrasound) for prostate cancer
• Previous use of CDK4/6 inhibitors (such as piperaciclib, rebocillib and abeceptil), second-generation androgen receptor antagonists (such as enzalutamide, apatamide, darotamide, revilumide and proclomide, etc.), ketoconazole, abiraterone acetate or other investigational drugs that inhibit androgen synthesis (such as TAK-700), other anti-tumor biological therapy, targeted therapy or tumor immunotherapy
• Confirmed by imaging, there are brain tumor foci
• History of severe lung disease such as interstitial pneumonia
• Plan to receive any other antitumor therapy during this trial
• Inability to swallow, chronic diarrhea and intestinal obstruction, or other factors that affect drug taking and absorption