This Phase I study aims to evaluate the safety, tolerability and PK of JSB462 in Japanese patients with metastatic prostate cancer.

Participants will receive JSB462 at the starting dose of 300 mg QD to evaluate its safety, tolerability and PK. Any Adverse Events (AEs) and Dose Limiting Toxicities (DLTs) will be assessed. DLTs will be evaluated in the first (28-day) cycle. If 300 mg once a day (QD) is considered intolerable by investigators and Novartis study personnel during dose evaluation meeting, the tolerability of 100 mg QD dose level cohort may be assessed.

Study treatment will be administered until disease progression (per PCWG3-modified RECIST v1.1 assessed by the investigator), unacceptable toxicity, death, withdrawal of consent, lost to follow-up or investigator's decision.

The End of Treatment Visit and the Safety Follow-up Visit will be performed within 7 days and 30 days from the last dose of JSB462, respectively. If participants discontinue study treatment for reasons other than disease progression (per PCWG3-modified RECIST v1.1 assessed by the investigator), death, lost to follow-up, or withdrawal of consent, then tumor assessments should continue to be performed in the Efficacy Follow-up Visit according to the planned schedule until disease progression (per PCWG3-modified RECIST v1.1 assessed by the investigator), death, withdrawal of consent or lost to follow-up.

Key Inclusion Criteria:

• Adult male patients with histologically or cytologically confirmed and documented adenocarcinoma of the prostate.
• At least 1 bone or visceral metastatic lesion (according to local radiology assessment by the investigator) present on baseline CT, MRI, or bone scan imaging obtained ≤28 days prior to enrollment. Lymph nodes as only site of metastases are not allowed.
• Patients with prostate cancer must have failed or refused available standard therapies, be intolerant or ineligible to receive such therapy, or for whom no standard therapy exists.
• Patients 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) is allowed prior to enrollment.
• Patients with an Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) ≤ 1.

Key Exclusion Criteria:

• Patients with CNS metastases.
• Patients with any other active malignancy other than prostate cancer. Exceptions to this criterion include the following: malignancies that were treated curatively at least 3 years before starting study treatment which have not recurred; basal cell carcinoma of the skin or squamous cell carcinoma of the skin that has undergone potentially curative local therapy or other tumors that will not affect life expectancy.

Other inclusion/exclusion criteria may apply