Novel site-specific mono-conjugates of Granulocyte Colony Stimulating Factor (G-CSF) are hereby described, with analogues and derivatives thereof, which stimulate proliferation and differentiation of progenitor cells to mature neutrophiles. These conjugates have been obtained using transglutaminase to covalently and site-specifically bind a hydrophilic, non-immunogenic polymer to a single glutamine residue of the human G-CSF native sequence and analogues thereof. These novel site-specific mono-conjugated derivatives are recommended for therapeutic use since they are stable in solution and exhibit significant biological activity in vitro and a longer bloodstream half-life, as compared to the non-conjugated protein, with a consequent prolonged pharmacological activity.
