PQ401 is a diarylurea-based inhibitor of IGF-1R, inhibiting autophosphorylation in MCF-7 cells and the IGF-1R isolated kinase domain at IC50s of 12 uM and < 1 uM, respectively. In IGF-1R stimulated MCF-7 cells, PQ401 was more effective at an IC50 of 6 uM. In MCF-7 cells IGF-1-mediated signaling is decreased by way of the Akt antiapoptotic pathway. Prolonged incubation with PQ401 induces a dose-dependent increase in caspase activation. (1)