Efficient Purification of rhG-CSF and its PEGylated Forms and Evaluation for In Vitro Activities.

Granulocyte-colony stimulating factor (G-CSF) has commonly been used to help the patients to recover from neutropenia inflicted due to radiotherapy, organ transplants and chemotherapy. As the number of people undergoing these therapies and procedures are increasing world-wide, the need for more economical ways of G-CSF production and improvement in its efficacy has become increasingly crucial. In the present study, recombinant human G-CSF (rhG-CSF) was expressed in E. coli and its purification process was optimized by demonstrating better efficiency and higher recoveries (upto 54%) in a multi-step chromatographic purification process, which is greater than the existing reports. Additionally, the efficacy of rhG-CSF was increased by derivatizing with polyethylene glycol (PEG; upto 85% PEGylation), which increases the plasma clearance time, reduces the immunogenicity and requires less frequent administration to the patient. Overall, the present study suggests a cost-effective purification process of rhG-CSF and also proposes its efficient conjugation with PEG for enhanced efficacy as compared to the existing commercially available forms.

A sensitive WST-8-based bioassay for PEGylated granulocyte colony stimulating factor using the NFS-60 cell line.

CONTEXT: Granulocyte colony stimulating factor (G-CSF) has been commonly used to treat neutropenia caused by chemotherapy, radiotherapy, and organ transplants. Improved in vitro efficacy of G-CSF has already been observed by conjugating it to polyethylene glycol (PEG). OBJECTIVE: The in vivo bioassay using tetrazolium dye with the NFS-60 cell line has been recommended for G-CSF but no such monographs are available for PEGylated G-CSF in pharmacopeias. In the present study, the assay recommended for G-CSF was evaluated for its suitability to PEGylated G-CSF. MATERIALS AND METHODS: The generally used MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium]-based assay was compared with a bioassay employing a water-soluble tetrazolium dye, WST-8 [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium], using NFS-60 cells at a concentration of 7 × 10(5) cells/ml against 800 IU/ml of PEGylated G-CSF at 24, 48, 72, and 72 h time points to determine the efficacy of PEGylated G-CSF. Further, the optimized WST-8 dye-based assay was used to test the potency of various commercially available PEGylated G-CSF preparations. RESULTS: The results demonstrated enhanced sensitivity of the WST-8-based assay over the conventional MTS-based assay for determining the potency of PEGylated G-CSF using the NFS-60 cell line. CONCLUSION: Our study demonstrates the potential application of WST-8-based bioassays for other biotherapeutic proteins of human and veterinary interest.

Refolding of recombinant human granulocyte colony stimulating factor: effect of cysteine/cystine redox system.

Granulocyte colony-stimulating factor (G-CSF) is a multifunctional cytokine which is widely used for treating neutropenia in humans. Evaluation of alternative to expensive components of redox buffer (reduced and oxidized glutathione) is an important step in reducing the cost of production of human biotherapeutic proteins. In the present study, refolding of recombinant human G-CSF expressed as inclusion bodies (IBs) in E. coli was optimized using cysteine and cystine redox agents. The refolding to correct native form of G-CSF was assessed by reverse phase high performance liquid chromatography (RP-HPLC). The optimized concentrations of cysteine and cystine for correct refolding of G-CSF were found to be 2 mM and 1 mM, respectively. The correctly refolded G-CSF was detected as early as 4 h of incubation in renaturation buffer containing optimized concentrations of cysteine (2 mM) and cystine (1 mM) redox agents. Refolding of G-CSF in optimized redox system increased with increase in shuffling time. Overall, the results suggested the use of cysteine/cystine redox pair could be an alternative to the costlier redox pairs for successful refolding of G-CSF and possibly other human biotherapeutic proteins of importance.