Rabbit Anti-Peg-filgrastim polyclonal antibody

Pegfilgrastim is composed of the protein filgrastim to which a 20-kDa polyethylene glycol (PEG) is covalently bound at the N-terminal residue resulting in decreased renal clearance and increased plasma half-life compared with filgrastim. This open-label, randomized, phase 2 study compared two doses of single administration pegfilgrastim (60 and 100 mug/kg) with daily doses of filgrastim (5 mug/kg/day) or no cytokine treatment after standard CHOP (cyclophosphamide, doxorubicin, vincristine and prednisolone) chemotherapy for non-Hodgkin's lymphoma in 50 elderly patients. The primary endpoint was the duration of grade 4 (severe) neutropenia (absolute neutrophil count <0.5 x 10(9)/l) in cycle 1. Duration of grade 4 neutropenia in cycle 1 was 2.2 (SD 1.2), 1.5 (SD 1.1), 0.8 (1.2) and 5.0 (2.0) days for patients who received pegfilgrastim 60 mu g/kg, pegfilgrastim 100 mu g/kg, filgrastim 5 mu g/kg and no cytokine, respectively. The baseline characteristics of the pegfilgrastim and filgrastim groups were imbalanced with increased bone-marrow involvement and prior therapy in the former. When the treatment groups were balanced for these risk factors, duration of grade 4 neutropenia was comparable with 2.0 and 3.0 vs. 0.6 and 0.5 days for pegfilgrastim 100 mu g/kg and filgrastim patients with and without these risk factors, respectively. The incidence of febrile neutropenia (defined as ANC < 0.5 x 10(9)/l and temperature > 38.2degreesC) was low (10% of patients). Pegfilgrastim was well tolerated with a safety profile similar to daily filgrastim. Once per chemotherapy cycle administration of pegfilgrastim was comparable to filgrastim in this clinical setting.

Previously we showed that granulocyte colony-stimulating factor (G-CSF) in vitro bioactivity is preserved when the protein is joined via a flexible 7 amino acid linker to an immunoglobulin-1 (IgG1)-Fc domain and that the G-CSF/IgG1-Fc fusion protein possessed a longer circulating half-life and improved hematopoietic properties compared to G-CSF in normal rats. We have extended this analysis by comparing the relative hematopoietic potencies of G-CSF/IgG1-Fc to G-CSF in normal mice and to G-CSF and polyethylene glycol (PEG) - modified G-CSF in neutropenic rats. Mice were treated for 5 days using different doses and dosing regimens of G-CSF/IgG1-Fc or G-CSF and circulating neutrophil levels in the animals measured on Day 6. G-CSF/IgG1-Fc stimulated greater increases in blood neutrophils than comparable doses of G-CSF when administered using daily, every other day or every third day dosing regimens. In rats made neutropenic with cyclophosphamide, G-CSF/IgG1-Fc accelerated recovery of blood neutrophils to normal levels (from Day 9 to Day 5) when administered as 5 daily injections or as a single injection on Day 1. By contrast, G-CSF accelerated neutrophil recovery when administered as 5 daily injections, but not when administered as a single injection. G-CSF/IgG1-Fc was as effective as PEG-G-CSF at accelerating neutrophil recovery following a single injection in neutropenic rats. G-CSF/IgG1-Fc and G-CSF/IgG4-Fc fusion proteins in which the 7 amino acid linker was deleted also were effective at accelerating neutrophil recovery following a single injection in neutropenic rats. These studies confirm the enhanced in vivo hematopoietic properties of G-CSF/IgG-Fc fusion proteins.