07:54 AM EDT, 06/18/2025 (MT Newswires) -- Merck ( MRK ) said Wednesday it has dosed the first patient in a phase 3 trial of ifinatamab deruxtecan in participants with pretreated metastatic castration-resistant prostate cancer.

The IDeate-Prostate01 phase 3 study is evaluating the efficacy and safety of the investigational drug against docetaxel.

Ifinatamab deruxtecan is an antibody-drug conjugate, which is being jointly developed by Merck ( MRK ) and Daiichi Sankyo, the company said.

The initiation of IDeate-Prostate01 is based on data from the IDeate-PanTumor01 phase 1/2 study, where ifinatamab deruxtecan demonstrated "promising" responses in heavily pretreated patients with metastatic castration-resistant prostate cancer, Merck ( MRK ) said.