This Phase II study aims to evaluate efficacy and safety of the combination of JSB462 (also known as luxdegalutamide) at 100 mg and 300 mg once a day (QD) doses + abiraterone compared with an androgen receptor pathway inhibitor (ARPI, abiraterone or enzalutamide) in participants with metastatic Hormone Sensitive Prostate Cancer (mHSPC) and to select the recommended dose of the combination for phase III. Towards that end, the totality of the efficacy, safety, tolerability and PK data from participants randomized in the study will be evaluated

The study for each participant consists of a Screening period (28 days), a treatment period, a post-treatment safety follow-up (30 days) followed by a long-term follow-up period.

During the treatment period:

• JSB462 is administered from randomization, orally, daily and continuously (100 mg or 300 mg QD) until disease progression per PCWG3-modified RECIST 1.1 as assessed by the investigator, the occurrence of unacceptable toxicities, death, participant decision or investigator decision.
• Abiraterone 1000 mg or enzalutamide 160 mg are administered from randomization, orally, daily, and continuously until disease progression per PCWG3-modified RECIST 1.1 as assessed by the investigator, the occurrence of unacceptable toxicities, death, participant decision or investigator decision.

During the post-treatment follow up period:

• Safety follow-Up: After discontinuation of study treatment, all participants will be followed for at least 1 safety follow-up visit (30 days [+/- 7 days] after treatment discontinuation). Subsequent lines of therapy may be administered according to investigator's discretion after treatment discontinuation.
• Long-term follow-up: Starts after the Safety follow-up period and lasts until the end of study. Safety, efficacy and survival information may be collected from participants during this period.

Key Inclusion Criteria:

• An Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) ≤2
• Histologically confirmed adenocarcinoma of the prostate. Participants with mixed histology (neuroendocrine) are not eligible
• High-volume mHSPC, defined by the presence of ≥1 metastatic visceral non-nodal lesion and/or ≥4 metastatic bone lesions (with at least one lesion outside the vertebral column and/or pelvis) in imaging exams (CT/MRI or bone scan) according to local radiology assessment by the investigator obtained ≤28 days prior to randomization
• Participants must have a castrate level of serum/plasma testosterone (<50 ng/dL or <1.7 nmol/L). Ongoing ADT (as defined by prior orchiectomy and/or ongoing GnRH analog/antagonist) for ≤90 days is allowed prior to randomization, provided that PSA zero (PSA level <0.2 ng/ml according to local laboratory as assessed by the investigator) is not achieved prior to randomization.

Key Exclusion Criteria:

• Prior exposure to a second generation ARPI (such as enzalutamide/darolutamide/apalutamide and/or abiraterone) for the treatment of advanced/metastatic disease is not allowed. Prior exposure to ARPI, to taxane chemotherapy (up to 6 cycles) or to RLT in the context of (neo)adjuvant treatment for localized prostate cancer is allowed, if the last dose of this treatment was administered >12 months from randomization. Prior use of a first generation ARPI (such as bicalutamide) in the context of ADT initiation with a GnRH analog is allowed, provided the first generation ARPI was administered for ≤14 days and last dose was administered ≥7 days from randomization.
• Participants with biochemical recurrence only or those without evidence of metastatic disease by radiological imaging (CT/MRI or bone scan) are not eligible

Other inclusion/exclusion criteria may apply.

Novartis is committed to sharing with qualified external researchers, access to patient-level data and supporting clinical documents from eligible studies. These requests are reviewed and approved by an independent review panel on the basis of scientific merit. All data provided is anonymized to respect the privacy of patients who have participated in the trial in line with applicable laws and regulations.

This trial data availability is according to the criteria and process described on www.clinicalstudydatarequest.com