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: 1. Age of ≥ 18 years old,male 2. ECOG PS score of 0 or 1； 3. Prostate adenocarcinoma confirmed by histological。 4. ADT no more than 3 months prior to randomization (when docetaxel is not used) with no radiographic or PSA progression 5. 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) 6. Voluntarily participate in this clinical trial, understand the study procedure and have signed informed consent Exclusion Criteria: 1. Previous ADT, chemotherapy, surgery, external radiation exposure, brachytherapy, radiopharmaceuticals, or experimental topical treatments (eg, radiofrequency ablation, cryoponic, high-energy focused ultrasound) for prostate cancer 2. 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 3. Confirmed by imaging, there are brain tumor foci 4. History of severe lung disease such as interstitial pneumonia 5. Plan to receive any other antitumor therapy during this trial 6. Inability to swallow, chronic diarrhea and intestinal obstruction, or other factors that affect drug taking and absorption