humanized definition
To reduce the immunogenicity of CDR-grafted humanized antibodies, the murine content in the CDR-grafted humanized antibodies is minimized through SDR grafting. Within each CDR, there are more variable positions that are directly involved in the interaction with antigen, i.e., specificity-determining residues (SDRs), whereas there are more conserved residues that maintain the conformations of CDRs loops. SDRs may be identified from the 3D structure of the antigen antibody complex and/or the mutational analysis of the CDRs. An SDR-grafted humanized antibody is constructed by grafting the SDRs and the residues maintaining the conformations of the CDRs onto human template, and its immunogenic potential is evaluated by measuring the reactivity to the sera from patients who had been immunized with the parental antibody.
To reduce the immunogenicity of CDR-grafted humanized antibodies, the murine content in the CDR-grafted humanized antibodies is minimized through SDR grafting. Within each CDR, there are more variable positions that are directly involved in the interaction with antigen, i.e., specificity-determining residues (SDRs), whereas there are more conserved residues that maintain the conformations of CDRs loops. SDRs may be identified from the 3D structure of the antigen antibody complex and/or the mutational analysis of the CDRs. An SDR-grafted humanized antibody is constructed by grafting the SDRs and the residues maintaining the conformations of the CDRs onto human template, and its immunogenic potential is evaluated by measuring the reactivity to the sera from patients who had been immunized with the parental antibody.
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<strong>humanized</strong> <strong>definition</strong><br />
• Creative Biolabs has extensive experience to offer the antibody humanization service for therapeutic and diagnostic development. We have<br />
successfully performed 15 mouse/rat humanization projects during the past decade with at least one <strong>humanized</strong> antibody entered the<br />
clinical trials. We also provide humanization service to antibodies derived from other species, such as non-human primate (NHP), rabbit, dog,<br />
chicken, llama and etc.<br />
• Humanization is important for reducing the immunogenicity of monoclonal antibodies derived from xenogeneic sources (commonly rodent)<br />
and for improving their activation of the human immune system. Since the development of the hybridoma technology, a large number of<br />
rodent monoclonal antibodies with specificity for antigens of therapeutic interest have been generated and characterized. Rodent<br />
antibodies are highly immunogenic in humans, which limits their clinical applications, especially when repeated administration is required.<br />
Importantly, they are rapidly removed from circulation and can cause systemic inflammatory effects as well. As a means of circumventing<br />
these problems, we have developed three antibody humanization strategies that can preserve the specificity and affinity of the antibody<br />
toward the antigen whereas significantly or completely eliminate the immunogenicity of the antibody in humans. The first approach is CDR<br />
grafting and the second is chain shuffling. These two methods are all based on phage display of <strong>humanized</strong> scFv variants and selection of<br />
high-affinity <strong>humanized</strong> binders through bio-panning. The third method, <strong>humanized</strong> IgG library screening, is somehow unique. We will make<br />
a library of <strong>humanized</strong> whole IgG to be displayed on the surface of mammalian cells and then high affinity binders will be sorted by FACS.
• CDR Grafting & SDR Grafting<br />
• We have established a CDR (complementarity-determining region) grafting platform, which is featured with<br />
randomization of a small set of framework residues using phage display technology and computer modeling. In this<br />
platform, six CDR loops comprising the antigen-binding site are grafted into corresponding human framework<br />
regions. Unfortunately, simple grafting of the rodent CDRs into human frameworks does not always reconstitute<br />
the binding affinity and specificity of the original antibody because framework residues are involved in antigen<br />
binding, either indirectly, by supporting the conformation of the CDR loops, or directly, by contacting the antigen.<br />
For this reason, we have developed a computer modeling method to randomize certain framework residues in<br />
addition to CDR grafting. The grafted CDRs together with the randomized residues are cloned into a phage display<br />
library and the <strong>humanized</strong> antibodies with the best affinity are selected by screening of the library. This approach<br />
allows the epitope specificity of the original antibody to be retained. Of note, humanization by this approach is not<br />
100% since the CDR regions are still of a rodent origin.
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