Humanized monoclonal antibodies structure

Changes in bioengineered expression systems can alter the number and composition of carbohydrate residues attached to recombinant or monoclonal antibody products [301]. The use of high pH anion-exchange HPLC and pulsed amperometric detection (Dionex Corp) has enabled the analytical profiling or mapping of the characteristic biantennary carbohydrate structures following their enzymatic release from both murine and humanized monoclonal antibodies [302]. 

For PK assays, it may be the case that a human-derived molecule is being dosed to a different species. In this case, an assessment should be made of whether structurally similar molecules in that species are likely to cross-react. If the molecule does not appear naturally in the species, for example, a humanized monoclonal antibody, then the assay can be used for that species, but potential matrix differences have to be investigated and solved, that is, parallelism, dilution linearity, and so on. 

In a different, reverse approach, epitopes common to several important serotypes may be useful for defining simple chemical structures that are capable of generating protective antibodies to multiple pneumococcal serogroups. The human monoclonal antibody Dobl, " which is a hybridoma-secreting human IgG2 antibody to the PS of serotype 6B, binds to and opsonizes pneumococci of serogroup 6. 

Fig. 15.7 Glycosylation of an antibody produced in tobacco plants expressing a human 3(l,4)-galactosyltransferase. As illustrated for Guy sl3 in Fig. 15.4, when the monoclonal antibody Mgr48 is produced in wild type tobacco plants (left panel), its glycosylation is structurally different and more heterogeneous than that of its mammalian counterpart (lower panel). When this antibody is produced in tobacco plants expressing the human galactosyltransferase (right panel), 30% of its N-glycans show terminal N-acetyllactosamine sequences identical to those carried by this antibody when it is produced in hybridoma cells.

Recombinant DNA technology has provided an alternative (and successful) route of reducing the innate immunity of murine monoclonals. The genes for all human immunoglobulin sub-types have been cloned, and this has allowed generation of various hybrid antibody structures of reduced immunogenicity. 

Mammalian cells are commonly employed for the production of therapeutic and diagnostic proteins, since they are able to correctly synthetize the large and complex structures that the human body requires as medicine [1]. Nowadays, they are employed for the large-scale production of recombinant therapeutic proteins, monoclonal antibodies (MAbs) and viruses used in the preparation of vaccines (e.g. against rabies, hepathytis B, polio, etc) [2]. An overview of some licensed/approved products derived from mammalian cell culture is given in Table 1. 

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