GMP Recombinant human GM-CSF (HZ-1002-GMP) stimulates dose-dependent proliferation of the TF-1 human erythroleukemic indicator cell line. Cell number was quantitatively assessed by PrestoBlue® Cell Viability Reagent. TF-1 cells were treated with increasing concentrations of GMP recombinant GM-CSF for 72 hours. The EC50 was determined using a 4-parameter non-linear regression model. Activity determination was conducted in triplicate on a validated bioassay. The EC50 range is 0.08-0.8 ng/mL.