Binding of human IL-17A to ixekizumab or human IL-17RA/Fc fusion (R&D Systems) was measured using a Biacore T100 system (Biacore Life Sciences) with a CM5 chip immobilized with human IL-17A using the amine-coupling chemistry (GE Healthcare Bio-sciences Corp.). All experiments were performed at 25°C with a flow rate of 5 µL/min. Binding of human IL-17RA/Fc to human IL-17A on the chip surface was demonstrated by injecting 50 µL of human IL-17RA/Fc at 1 µM. After regeneration, 50 µL of ixekizumab at 500 nM was added nearly saturating the human IL-17A on the surface. To determine whether ixekizumab blocks human IL-17A binding to human IL-17RA, ixekizumab at 500 nM was first injected to nearly saturate the human IL-17A surface followed by an injection of human IL-17RA/Fc at 1 µM.