IL-6R superantagonist Sant7 is able to inhibit proliferation of INA-6 cells induced by hIL-6 in a dose-dependent manner. Effects of 0.5 ng/mL and 2.5 ng/mL hIL-6 could be blocked by 1 μg/mL and 10 μg/mL Sant7, respectively. A total of 2 μg/mL of vIL-6 could not be blocked with up to 10 μg/mL Sant7.