Cixutumumab, a human monoclonal antibody (HuMAb), targets the insulin-like growth factor receptor. Ramucirumab is a recombinant HuMAb that binds to vascular endothelial growth factor receptor-2. A non-comparative randomised phase II study evaluated cixutumumab or ramucirumab plus mitoxantrone and prednisone (MP) in metastatic castration-resistant prostate cancer (mCRPC).