Extended activity in cynomolgus monkeys of a granulocyte colony-stimulating factor mutein conjugated with high molecular weight polyethylene glycol

The activity of a granulocyte colony-stimulating factor (G-CSF) mutein (nar tograstim; [NTG]) conjugated with an average of two polyethylene glycol (PE G) chains per protein molecule was examined in cynomolgus monkeys following a single s.c. injection, Groups of monkeys mere given 10 mu g/kg, 30 mu g/ kg, or 100 mu g/kg. For comparison, one group of monkeys was given 5 mu g/k g of recombinant human G-CSF (rHuG-CSF) daily for six days. In monkeys give n 100 mu g/kg of PEG-NTG, neutrophil levels reached a peak one day after in jection approximately 20-fold higher than baseline levels. Neutrophil numbe rs in these animals were still significantly elevated six days after inject ion, In contrast, peak neutrophil levels in monkeys given six injections of rHuG-CSF reached a peak only on day 6 and were approximately the same as t hat in monkeys given a single dose of PEG-NTG six days before, Pharmacokine tics of PEG-NTG in these monkeys indicated that the area under the plasma c oncentration time curve (AUC) increased with increasing the dose from 497 n g.h/ml at 10 mu g/kg, 6,140 ng.h/ml at 30 mu g/kg to 27,900 ng.h/ml at 100 mu g/kg. In a separate study, the effects of single doses of 100 mu g/kg of PEG-NTG, rHuG-CSF, and unmodified NTG were compared, In this experiment, p eak numbers of neutrophils mere reached two days after injection in animals receiving PEG-NTG and one day after in animals given unmodified proteins, The pharmacokinetic parameters demonstrated increased exposure for PEG-NTG relative to the unmodified proteins with an AUC(0). (infinity) of 21,012 ng .h/ml compared with 5,492 ng.h/ml for rHuG-CSF and 5,153 ng.h/ml for NTG, T hese results demonstrate that conjugation of a G-CSF mutein with high molec ular n eight PEG results in a preparation that can induce prolonged elevati on of neutrophils in normal nonhuman primates following a single injection.