A Clinical Study of Ifinatamab Deruxtecan (I-DXd) in People With Metastatic Prostate Cancer (MK-2400-001)

Researchers are looking for new ways to treat metastatic castration-resistant prostate cancer (mCRPC). Researchers have designed a study medicine called ifinatamab deruxtecan (also called I-DXd or MK-2400) to treat mCRPC. The goal of this study is to learn if people who receive I-DXd live longer overall and live longer without the cancer growing or spreading than people who receive chemotherapy.

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Has histologically- or cytologically-confirmed adenocarcinoma of the prostate without small cell histology * Has prostate cancer progression while on androgen deprivation therapy (ADT) (or post bilateral orchiectomy) within 6 months prior to Screening * Has current evidence of distant metastatic disease (M1 disease) documented by either bone lesions on bone scan and/or soft tissue disease by computed tomography (CT)/magnetic resonance imaging (MRI) * Has received prior treatment with 1 or 2 androgen receptor pathway inhibitors (ARPIs) and progressed during or after at least 8 weeks of treatment * Has provided tumor tissue from a core or excisional biopsy from soft tissue not previously irradiated and obtained after disease progression on the most recent prior therapy * Has recovered from adverse events (AEs) due to previous anticancer therapies Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * Is unable to swallow tablets/capsules * Has any of the following indicators of interstitial lung disease (ILD)/pneumonitis: 1. Has any history of ILD/pneumonitis that required steroid use, except for a history of radiation pneumonitis that did not require steroids 2. Has current ILD/pneumonitis 3. Has a clinical or radiographic suspicion of ILD for which the diagnosis of ILD cannot be ruled out * Has clinically severe pulmonary compromise resulting from intercurrent pulmonary illnesses * Has uncontrolled or significant cardiovascular disease * Has received prior treatment with a taxane-based chemotherapy agent for metastatic castration-resistant prostate cancer (mCRPC) * Has had prior discontinuation of an antibody drug conjugate (ADC) that consists of an exatecan derivative (eg, trastuzumab deruxtecan) due to treatment-related toxicities * Has a "superscan" bone scan