Apparent degradation forms of rhG-CSF under forced conditions: Insights for better quality-control of bioproducts.

Stability and quality control of therapeutic protein formulations is a substantial part of drug development process. The objective of this study is to obtain information about stability of a recombinant human granulocyte colony stimulating factor (rhG-CSF) against various stress factors. This will play a crucial role in the finished product formulation development. In this study, rhG-CSF was exposed to various chemical and physical stress conditions at different levels in order to identify degradation pathways and the nature of impurities generated. Experiments were performed by a combination of orthogonal analytical techniques (reversed phase chromatography (RP-HPLC), size exclusion chromatography (SEC-HPLC), polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing (IEF)) to set and characterize the different degraded samples. The SEC-HPLC results suggest that the major degradation factors generating aggregated forms of the protein are basically thermal stress, freeze-thaw cycles and vortexing. Meanwhile, deamidated rhG-CSF was induced by basic pH as shown by IEF electrophoregram. As well, oxidized forms were generated increasingly with the time of exposure to hydrogen peroxide as outlined by RP-HPLC analysis. Based on these results, it was possible to define the storage and handling conditions of rhG-CSF finished product during its shelf life.

Optimization of PEGylation reaction time and molar ratio of rhG-CSF toward increasing bioactive potency of monoPEGylated protein.

PEGylation is one of the strategies used for enhancing in vivo residence time of recombinant human Granulocyte Colony-Stimulating Factor (rhG-CSF) and therefore reducing in dose frequency to better fit with patient comfort treatment. In this study, three methoxy polyethylene glycol propionaldehydes (mPEG- ALD) of 10, 20 and 30kDa MW were utilized to produce biologically active monoPEGylated rhG-CSF with enhanced molecular weight. PEGylation reactions were carried out at room temperature and pH 5.0 in the presence of cyanoborohydride and two mPEG-ALD: protein molar ratios (3:1 and 5:1). The reactions were monitored with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography (SEC-HPLC). The results showed that a 2h reaction with 5:1 mPEG-ALD: protein molar ratio was sufficient to direct the reaction toward optimal yields of monoPEGylated protein (86%). Subsequently, isolation of the monoPEGylated forms was successfully achieved. The purified products were compared with respect to their purity (≥95%), identity and isoelectric focusing parameter characteristics. Biological potencies were measured by cell proliferation assay and showed 20.80-42.73% retention of bioactivities. This study highlights the possible improvement of rhG-CSF efficiency by PEGylation. Further studies will investigate in vitro and in vivo immunogenicity and toxicity of monoPEGylated conjugates.

Stereoselective Cyclopropanation to Homoquinones from Phenacyl Carbenes Obtained through Quinone-Electrogenerated Bases.

A series of new (E) and (Z)-benzoyl-homoquinones have been prepared in good yield by the parent quinone-electrogenerated base (EGB) in the presence of α-bromoacetophenones or α-bromopropiophenone. The EGB, obtained when electrolysis of p-benzoquinone, or 1,4-naphthoquinone, is carried out at the reduction potential of their first voltammetric peak, conducted to electrogenerated phenacyl carbenes after halide evolution on the first obtained bromo-enolates. The stereoselectivity of the [2 + 2]cycloaddition of the carbene to the quinoid substrate is highly dependent on the electrode nature. Reaction mechanism proposal is discussed.