The purpose of the study is to evaluate the safety, tolerability, and efficacy of the two different treatment combinations of tulmimetostat in participants with de novo or recurrent Metastatic Hormone-Sensitive Prostate Cancer (mHSPC).
Adult men ≥ 18 years old with de novo or recurrent mHSPC (without neuroendocrine or small cell features). The tumor lesion(s) may be located in the bone, soft tissue/visceral region, or both.
Participants must have castrate levels of testosterone, i.e., ≤ 50 ng/dL (≤ 1.7 nM).
Eastern Cooperative Oncology Group (ECOG) performance status 0 to 2
Adequate bone marrow and organ function
Participants with evidence of mCRPC or biochemical recurrence / PSA only disease or asymptomatic prostate cancer without known metastatic disease and with no requirement for therapy and with normal PSA for ≥ 1 year prior to the start of study treatment.
Participants who have not received ARPI treatment for mHSPC and present with PSA levels of ≤0.5 ng/mL or those with prior/ongoing ARPI treatment presenting with PSA levels of ≤ 0.2 ng/mL prior to treatment assignment/randomization.
they have received prior therapy (e.g. surgery, radiotherapy, gamma knife), are neurologically stable and asymptomatic.
they are not receiving corticosteroid for the purpose of maintaining neurologic integrity and have baseline and subsequent radiological imaging of the brain.