Pegylated feline granulocyte colony-stimulating factor increases neutrophil levels in cats

Neutropenia can often be corrected by treatment with granulocyte-colony stimulating factor (G-CSF) and off-label use of commercial human G-CSF (HuG-CSF) is a commonly used treatment for neutropenic animals. However, long-term HuG-CSF treatment can be associated with adverse effects, including neutropenia. Here, feline (Fe) G-CSF was produced in Pichia pastoris, pegylated (Peg) FeG-CSF and tested in cats. A randomized controlled clinical trial was conducted to evaluate the efficacy of PegFeG-CSF compared to FeG-CSF or HuG-CSF in FIV-infected (n=14), FIV-uninfected healthy cats (n=19), and in HuG-CSF-induced neutropenic cats (n=4). Daily FeG-CSF doses induced higher neutrophil production than HuG-CSF after the second week of treatment (P⩽0.002). Weekly doses of PegFeG-CSF induced higher neutrophil counts and showed greater sustained activity than weekly doses of FeG-CSF. PegFeG-CSF provided the most therapeutic and sustainable neutrophil production (P