QLC5508 in Participants With Metastatic Prostate Cancer

Inclusion Criteria: * Male, aged ≥18 years. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. * Life expectancy of at least 3 months. * Histologically or cytologically confirmed adenocarcinoma of the prostate without evidence of small-cell features. * Diagnosis of metastatic castration-resistant prostate cancer (mCRPC). * Prior treatment with novel hormonal agents (NHAs) and documented disease progression. * Adequate organ function. * Recovery from all reversible adverse events (AEs) related to prior anticancer therapies. Exclusion Criteria: * 1\. Prior treatment with a B7-H3-targeted therapy, or with an antibody-drug conjugate (ADC) using a topoisomerase I inhibitor (TOP1i) as the payload, or with any TOP1i-class agent. 2\. History of or current significant cardiovascular or cerebrovascular disease. 3. Active, uncontrolled infection. 4. Concurrent or prior history of another primary malignancy 5. History of interstitial lung disease (ILD) or non-infectious pneumonitis, or current ILD/non-infectious pneumonitis 6. Current hepatic encephalopathy, hepatorenal syndrome, or cirrhosis classified as Child-Pugh class B or worse. 7\. Known hypersensitivity or allergy to any investigational product or its excipients.