New insight into strategies used to develop long-acting G-CSF biologics for neutropenia therapy

Over the last 20 years, granulocyte colony-stimulating factors (G-CSFs) have become the major therapeutic option for the treatment of patients with neutropenia. Most of the current G-CSFs require daily injections, which are inconvenient and expensive for patients. Increased understanding of G-CSFs' structure, expression, and mechanism of clearance has been very instrumental in the development of new generations of long-acting G-CSFs with improved efficacy. Several approaches to reducing G-CSF clearance via conjugation techniques have been investigated. PEGylation, glycosylation, polysialylation, or conjugation with immunoglobulins or albumins have successfully increased G-CSFs' half-lives. Pegfilgrastim (Neulasta) has been successfully approved and marketed for the treatment of patients with neutropenia. The rapidly expanding market for G-CSFs has increased demand for G-CSF biosimilars. Therefore, the importance of this review is to highlight the principle, elimination's route, half-life, clearance, safety, benefits, and limitations of different strategies and techniques used to increase the half-life of biotherapeutic G-CSFs. Understanding these strategies will allow for a new treatment with more competitive manufacturing and lower unit costs compared with that of Neulasta.

Effect of ANITVNITV peptide fusion on the bioactivity and pharmacokinetics of human IFN-α2b and a hyper-N-glycosylated variant

Different strategies have been developed and successfully applied to biotherapeutics in order to improve their in vivo efficacy. The genetic fusion to natural or synthetic glycosylated peptides constitutes a promising strategy since it conserves the protein sequence and results in the improvement of the pharmacokinetic properties. The ANITVNITV peptide described by Perlmann and coworkers presents 9 amino acids and 2 potential N-glycosylation sites. Its fusion to FSH resulted in the increase of the molecular mass and negative charge of the protein. Consequently, the pharmacokinetics was considerably improved. The aim of the present study was to compare the influence of ANITVNITV peptide fusion on the physicochemical, biological and pharmacokinetic properties of native hIFN-α2b (IFNwt), which contains a single O-glycosylation site, and a hyperglycosylated variant (IFN4N), that bears, in addition, 4 N-linked glycans. The resulting molecules, IFNwtNter and IFN4NNter, evidenced a higher molecular mass and negative charge compared to IFNwt and IFN4N, respectively. Therefore, the pharmacokinetic properties of the new molecules were significantly improved. The molecules obtained by the synthetic peptide fusion strategy evidenced a decrease in their in vitro antiviral specific biological activities (SBA). However, in vitro antiproliferative SBA was differentially modified for IFNwtNter and IFN4NNter in comparison with the parental molecules. For IFNwtNter, a reduction in the antiproliferative SBA was also observed. Remarkably, the addition of the ANITVNITV peptide to the N-terminus of IFN4N had a positive impact on its growth-inhibitory activity. This feature together with its improved pharmacokinetics encourages the development of IFN4NNter as an IFN-α based biobetter.

Soluble prokaryotic overexpression and purification of bioactive human granulocyte colony-stimulating factor by maltose binding protein and protein disulfide isomerase

Human granulocyte colony-stimulating factor (hGCSF), a neutrophil-promoting cytokine, is an effective therapeutic agent for neutropenia patients who have undergone several cancer treatments. Efficient production of hGCSF using E. coli is challenging because the hormone tends to aggregate and forms inclusion bodies. This study examined the ability of seven different N-terminal fusion tags to increase expression of soluble hGCSF in E. coli. Four tag proteins, namely maltose-binding protein (MBP), N-utilization substance protein A, protein disulfide isomerase (PDI), and the b'a' domain of PDI (PDIb'a'), increased the solubility of hGCSF under normal conditions. Lowering the expression temperature from 30°C to 18°C also increased the solubility of thioredoxin-tagged and glutathione S-transferase-tagged hGCSF. By contrast, hexahistidine-tagged hGCSF was insoluble at both temperatures. Simple conventional chromatographic methods were used to purify hGCSF from the overexpressed PDIb'a'-hGCSF and MBP-hGCSF proteins. In total, 11.3 mg or 10.2 mg of pure hGCSF were obtained from 500 mL cultures of E. coli expressing PDIb'a'-hGCSF or MBP-hGCSF, respectively. SDS-PAGE analysis and silver staining confirmed high purity of the isolated hGCSF proteins, and the endotoxin levels were less than 0.05 EU/µg of protein. Subsequently, the bioactivity of the purified hGCSF proteins similar to that of the commercially available hGCSF was confirmed using the mouse M-NFS-60 myelogenous leukemia cell line. The EC₅₀s of the cell proliferation dose-response curves for hGCSF proteins purified from MBP-hGCSF and PDIb'a'-hGCSF were 2.83±0.31 pM, and 3.38±0.41 pM, respectively. In summary, this study describes an efficient method for the soluble overexpression and purification of bioactive hGCSF in E. coli.

Mycobacterium tuberculosis-induced expression of granulocyte-macrophage colony stimulating factor is mediated by PI3-K/MEK1/p38 MAPK signaling pathway

Members of the colony stimulating factor cytokine family play important roles in macrophage activation and recruitment to inflammatory lesions. Among them, granulocyte-macrophage colony stimulating factor (GM-CSF) is known to be associated with immune response to mycobacterial infection. However, the mechanism through which Mycobacterium tuberculosis (MTB) affects the expression of GM-CSF is poorly understood. Using PMA-differentiated THP-1 cells, we found that MTB infection increased GM-CSF mRNA expression in a dosedependent manner. Induction of GM-CSF mRNA expression peaked 6 h after infection, declining gradually thereafter and returning to its basal levels at 72 h. Secretion of GM-CSF protein was also elevated by MTB infection. The increase in mRNA expression and protein secretion of GM-CSF caused by MTB was inhibited in cells treated with inhibitors of p38 MAPK, mitogen-activated protein kinase kinase (MEK-1), and PI3-K. These results suggest that up-regulation of GM-CSF by MTB is mediated via the PI3-K/MEK1/p38 MAPK-associated signaling pathway. [BMB Reports 2013; 46(4): 213-218]

Antiapoptotic effects of Phe140Asn, a novel human granulocyte colony-stimulating factor mutant in H9c2 rat cardiomyocytes

Granulocyte colony-stimulating factor (G-CSF) is used for heart failure therapy and promotes myocardial regeneration by inducing mobilization of bone marrow stem cells to the injured heart after myocardial infarction; however, this treatment has one weakness in that its biological effect is transient. In our previous report, we generated 5 mutants harboring N-linked glycosylation to improve its antiapoptotic activities. Among them, one mutant (Phe140Asn) had higher cell viability than wild-type hG-CSF in rat cardiomyocytes, even after treatment with an apoptotic agent (H₂O₂). Cells treated with this mutant significantly upregulated the antiapoptotic proteins, and experienced reductions in caspase 3 activity and PARP cleavage. Moreover, the total number of apoptotic cells was dramatically lower in cultures treated with mutant hG-CSF. Taken together, these results suggest that the addition of an N-linked glycosylation was successful in improving the antiapoptotic activity of hG-CSF, and that this mutated product will be a feasible therapy for patients who have experienced heart failure. [BMB Reports 2012; 45(12): 742-747]