Albugranin™, a recombinant human granulocyte colony stimulating factor (G-CSF) genetically fused to recombinant human albumin induces prolonged myelopoietic effects in mice and monkeys

Purpose. Albugranin(TM) fusion protein is recombinant granulocyte colony stimulating factor (rG-CSF) genetically fused at its N-terminus to the C-terminus of recombinant serum human albumin and is expected to have a relatively long half-life compared with rG-CSF alone. In this study, the pharmacodynamics and pharmacokinetics of Albugranin were evaluated in BDF1 mice and cynomolgus monkeys. Methods. Single doses of Albugranin (0.25-5 mg/kg) or Filgrastim (methionyl rG-CSF, 0.25, or 1.25 mg/kg) were administered subcutaneously (SC) to mice and multiple doses of Albugranin (25-100 mug/kg every 4 or 7 days) or Filgrastim (5 mug/kg daily) were administered SC for 14 days to monkeys for hematologic evaluation. For pharmacokinetics studies, mice were injected intravenously (IV) or SC with single doses of Albugranin (0.25-1.25 mg/kg) or Filgrastim (0.25 mg/kg) and monkeys were injected SC with multiple doses of Albugranin (100-1000 mug/kg once weekly for 5 weeks). Plasma levels of Albugranin and Filgrastim were measured by enzyme-linked immunosorbent assay. Results. In mice, administration of Albugranin effectively increased the number of peripheral granulocytes and mobilized hematopoietic progenitor cells for up to 5 days. The magnitude and duration of this effect were dose-dependent. In contrast, administration of Filgrastim resulted in a small increase in both cell types on day 1 only. Albugranin administered to cynomolgus monkeys caused an increase in peripheral neutrophils, with a less prominent increase in peripheral monocytes. Albugranin-induced neutrophilia peaked 24 h following each dose administration. Administration of Filgrastim daily in monkeys resulted in moderate increases in neutrophils that were maximal on days 8-12 during the course of treatment. Compared with Filgrastim, Albugranin had a longer terminal half-life (t(1/2,term)), and mean residence time (MRT), and slower clearance (CL/F) in mice. The t(1/ 2, term), MRT, and CL/F of Albugranin following SC administration to BDF1 mice were 5.6-5.7 h, 16.7-20.7 h, and 6.37-12.2 mL/h/kg, respectively, compared with 2.54 h, 4.9 h, and 164 mL/h/kg, respectively for Filgrastim. In cynomolgus monkeys, the corresponding values of t1/ 2, term, MRT, and CL/F for Albugranin were 7.73-13.3 h, 19.4-27.3 h, and 7.90-27.5 mL/h/kg, respectively, for doses of 1001000 mug/kg. An exposure-response relationship that could be empirically described with a simple E-max model with baseline was found between day 15 absolute neutrophil count and area under the curve following the first dose in cynomolgus monkeys. Conclusion. The sustained activity of Albugranin in mice and monkeys demonstrated in these studies suggests that this agent could be given less frequently than Filgrastim to achieve similar therapeutic effects in patients.