A Comparative Dose-finding Study of RS-113 in Patients With Metastatic Castration-resistant Prostate Cancer

This is an open-label, randomized, comparative phase II clinical trial conducted in 4 treatment arms: * Arm 1: RS-113 160 mg (2 capsules) once daily (QD) * Arm 2: RS-113 240 mg (3 capsules) QD * Arm 3: RS-113 320 mg (4 capsules) QD * Arm 4: abiraterone 1000 mg (4 tablets) QD plus prednisolone 10 mg QD All enrolled patients who have not previously undergone a surgical castration will receive androgen deprivation therapy (ADT) with luteinizing hormone-releasing hormone (LHRH) analogues throughout the study The study will include the following periods: 1. Screening period: up to 28 days Days \[-27 to -0\] prior to the first dose of the study treatment 2. Core study: up to 2 years Days \[1 to 728\] Eligible patients should be randomized to one of four treatment arms (in a 1:1:1:1 ratio): * Arm 1: RS-113 160 mg (2 capsules) QD * Arm 2: RS-113 240 mg (3 capsules) QD * Arm 3: RS-113 320 mg (4 capsules) QD * Arm 4: abiraterone 1000 mg (4 tablets) QD plus prednisolone 10 mg QD During the core study, the treatment will continue until the earliest of the following: * Day 728 (+7 days) * Disease progression (per RECIST 1.1 and PCWG3 criteria) * Unacceptable toxicity * Patient withdrawal from the study During the core study tumor response assessments will be performed approximately every 8 weeks for the first 24 weeks, and every 12 weeks thereafter 3. Extension phase Patients who had stable disease or tumor response within 2 years of treatment may be enrolled in an extension study. During the Extension phase, patients will continue to receive the same treatment regimen as assigned in the Core study During the Extension phase, the treatment will be administered from Day 728 until the earliest of the following: * Disease progression * Unacceptable toxicity * Patient withdrawal from the study 4. Follow-up period (follow-up/FU) * Patients who complete the planned 2-year study treatment and are not enrolled in the Extension phase will have one in-person Follow-up (FU) visit 28±3 days after the last dose of investigational product/comparator. This will be the final study visit for these patients. Subsequent treatment will be provided through the national healthcare system (as part of routine clinical practice) if indicated. * Patients who discontinue treatment early due to disease progression will have one in-person FU visit 28±3 days after the last dose of investigational product/comparator (for safety data collection). Thereafter, follow-up will be conducted via telephone contacts every 12 weeks until Day 728 or death (for survival data collection). * Patients who discontinue treatment early for reasons other than disease progression will have one in-person FU visit 28±3 days after the last dose of investigational product/comparator (for safety data collection). Subsequently, they will undergo FU visits with tumor response assessments every 8 weeks until Day 169, and then every 12 weeks until Day 728, disease progression, or initiation of new treatment, whichever occurs first Completing the last visit means the end of participation in the clinical trial for each particular patient