Barata P, et al. - Herein, linsitinib's safety, as well as efficacy in a single-arm, phase II study including men with chemotherapy-naïve asymptomatic or mildly symptomatic metastatic castration resistant prostate cancer (mCRPC), was reported. With safety and good tolerability, no activity of single-agent linsitinib was shown in men with mCRPC. These results highlight the complexity of using insulin-like growth factor receptor-1 as a therapeutic target in this patient population.