Glycosylation of recombinant human granulocyte colony stimulating factor: implications for stability and potency

The production of recombinant human granulocyte colony stimulating factor (HuG-CSF) by gene cloning has made this growth factor available in large quantities for clinical application. There is accumulating evidence to suggest that the glycosylation of HuG-CSF confers advantages in terms of in vitro stability to temperature, pH and degradation by proteases, and a recent report attributes a greater biological potency, in the absence of larger biological mass, to the property of glycosylation. In this study, the biological potency of glycosylated rHuG-CSF (lenograstim) was compared with that of non-glycosylated rmetHuG-CSF (filgrastim) and a non-glycosylated rHuG-CSF (non-commercial preparation), using duplicate assays of neutrophil and erythroid colony formation in three human bone marrows. Serial doubling dilutions of each rHuG-CSF resulted in a concentration range of 0.008-128 ng/ml. Qualitative (number) and quantitative (size) assessments of colonies were performed at day 14 of culture. Lenograstim proved twice as potent as filgrastim (and non-commercial rHuG-CSF) at maximal colony stimulation, and 20 times more potent than both at half-maximal colony stimulation (P = 0.0001). Incubation with lenograstim also produced a higher proportion of colonies with > 200 cells than either of the other preparations. In conclusion, glycosylated rHuG-CSF (lenograstim) had a greater qualitative and quantitative potency than the non-glycosylated rHuG-CSFs (filgrastim and non-commercial rHuG-CSF), indicating that glycosylation confers a potency advantage on lenograstim.