Proof-of-concept simulations of biologics-induced liver injury responses for tocilizumab in BIOLOGXsym were made by integrating tocilizumab-induced ROS and steatosis, tocilizumab effects on IL-6 receptor signaling and selected downstream effects which were potentially relevant to tocilizumab-mediated hepatotoxicity (i.e., hepatocyte regeneration, macrophage recruitment, suppression of CYP expression), and by the hepatic exposure predicted by GastroPlus® PBPK modeling for a clinically reported tocilizumab protocol (i.e., 8 mg/kg IV tocilizumab given every four weeks for 12 weeks). The gene discussed is PPIG; the disease is steatosis.