Structural and functional comparability study of anti-CD20 monoclonal antibody with reference product.

BACKGROUND: Cell surface protein, CD20, is extensively expressed on the surface of B cells. Antibodies targeting CD20 protein are being used to treat B-cell malignancies and B-cell mediated autoimmune diseases. Considering the cost of therapy with innovator monoclonal antibodies for these diseases, development of biosimilar products for the treatment of such diseases provides affordable solution to rising healthcare costs. MATERIALS AND METHODS: Reference products of rituximab (six batches) were procured and stored as per manufacturer's instructions. Cell lines used in bioassay were procured from American Type Culture Collection and all other reagents used for analysis were of analytical grade. Primary structure was studied by intact mass analysis, peptide fingerprinting, peptide mass fingerprinting and sequence coverage analysis. Higher order structure was studied by circular dichroism, ultraviolet-visible spectroscopy, fluorescence spectroscopy, and disulfide bridge analysis. Different isoforms of reference product and SB-02 were identified using capillary isoelectric focusing and capillary zone electrophoresis. Glycosylation was studied by N-glycan mapping using LC-ESI-MS, point of glycosylation, released glycan analysis using ultra performance liquid chromatography (UPLC). Product related impurities such as oligomer content analysis and oxidized impurities were studied using size exclusion chromatography and reverse phase high performance liquid chromatography, respectively. RESULTS AND CONCLUSION: Here, we report physicochemical and biological characterizations of Sun Pharma's proposed biosimilar (SB-02) to rituximab, a monoclonal anti-CD20 antibody approved for the treatment of non-Hodgkin's lymphoma and chronic lymphocytic leukemia. SB-02 and rituximab exhibited indistinguishable primary as well as higher-order structure upon analyzing with the array of analytical and extended characterization methods according to statistical methods. The molecule also displayed comparability to reference product in post-translational modifications and charge heterogeneity. In functional bioassays, SB-02 demonstrated comparable potency with respect to reference product. Our results indicate highly similar quality profile between SB-02 and rituximab.

Full-length Plasmodium falciparum circumsporozoite protein administered with long-chain poly(I·C) or the Toll-like receptor 4 agonist glucopyranosyl lipid adjuvant-stable emulsion elicits potent antibody and CD4+ T cell immunity and protection in mice.

The Plasmodium falciparum circumsporozoite (CS) protein (CSP) is a major vaccine target for preventing malaria infection. Thus, developing strong and durable antibody and T cell responses against CSP with novel immunogens and potent adjuvants may improve upon the success of current approaches. Here, we compare four distinct full-length P. falciparum CS proteins expressed in Escherichia coli or Pichia pastoris for their ability to induce immunity and protection in mice when administered with long-chain poly(I · C) [poly(I · C)LC] as an adjuvant. CS proteins expressed in E. coli induced high-titer antibody responses against the NANP repeat region and potent CSP-specific CD4(+) T cell responses. Moreover, E. coli-derived CS proteins in combination with poly(I · C)LC induced potent multifunctional (interleukin 2-positive [IL-2(+)], tumor necrosis factor alpha-positive [TNF-α(+)], gamma interferon-positive [IFN-γ(+)]) CD4(+) effector T cell responses in blood, in spleen, and particularly in liver. Using transgenic Plasmodium berghei expressing the repeat region of P. falciparum CSP [Pb-CS(Pf)], we showed that there was a 1- to 4-log decrease in malaria rRNA in the liver following a high-dose challenge and ~50% sterilizing protection with a low-dose challenge compared to control levels. Protection was directly correlated with high-level antibody titers but not CD4(+) T cell responses. Finally, protective immunity was also induced using the Toll-like receptor 4 agonist glucopyranosyl lipid adjuvant-stable emulsion (GLA-SE) as the adjuvant, which also correlated with high antibody titers yet CD4(+) T cell immunity that was significantly less potent than that with poly(I · C)LC. Overall, these data suggest that full-length CS proteins and poly(I · C)LC or GLA-SE offer a simple vaccine formulation to be used alone or in combination with other vaccines for preventing malaria infection.

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.