Different from some IL-6 (R) antibodies that have been developed PK/PD models based on first-in-human studies with data from healthy volunteers (Xu et al., 2011), our modeling and simulation study in RA patients directly could avoid the aforementioned confounding factors and recommend more accurate dose regimens for phase Ib/IIa trials. The gene discussed is IL6; the disease is rheumatoid arthritis.