Recombinant human IL-28A (HZ-1235) stimulates dose-dependent induction of alkaline phosphatase production in a HEK293 reporter cell line. Alkaline phosphatase production was assessed using pNPP as a chromogenic substrate. The EC50 was determined using a 4-parameter non-linear regression model. The EC50 values range from 0.01-0.06 ng/mL.