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Chimerization and Humanization

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Structure factor. Structure of the biologics. Chimerization and that’s why we use several approaches to modify the structure and the first one I want to talk about is c chimerization it’s also called humanization.
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We scaled down the antibody structure. So as to reduce the immuno genic response. The two important implications or applications. Therapeutically, it prolongs residence time in a body and to make it more effective, because then the biologics get to stay in the system to bring about the effect. And the diagnostic application. With chimerization, the renal, biliary or colonic uptake is enhanced. And that makes it a more efficient diagnostic agent. Chimerization. How do we do that? This is a chemical structure for a regular immunoglobulin molecule. That’s the antibody structure. And that is the constant region. We can trim down the constant region to become smaller, or we can use a fragment of the antibody.
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Or even we can use the variable region only as to antibody. And by doing so, we reduced structure; reduced the size of the biologics, making it less detectable by the human body system. And that’s how they get to stay in the system longer to be able to bring out the effect. I’m going to turn to the formulation factors for emergentist
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Now there’s a big problem with the biologic formulation and that is aggregation. Proteins are charged molecules. And they tend to attract each other by way of electrostatic interaction. And once polymerized, they are subject it to detection by the host system. The Monell merica protein is less immunogenic than the polymeric proteins, And that’s why we use serum albumin or some sort of effective to reduce aggregation. So look at this example, the monomeric proteins. They have immune tolerance, in other words, they are not immunogenic. The aggregated proteins, they’re polymerized and they have breakdown immune tolerance and that’s why they are immunogenic. Formulations factors, glycosylation, it refers to the covalent attachment of glycans or carbohydrate through the protein surface.
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With glycosylation, protein is stabilized. Circulatory turnover and the clearance rate are reduced. And also to increase the subcutaneous absorption and improve the distribution. So we talked about glycation as a strategy to modify the biologics structure. And this table shows a lists of glycosylated product. Let’s look at just one example here, the Darbopoetin alpha, the commercial name is ARANESP. And it’s derived from the CHO cells, the Chinese hamster ovary cells, via recombinant protein technology. And then it’s glycosylated at the nitrogen position and with the glycosylation, the half-life is increased by several times. And therefore instead of being given two to three times a day, now ARANESP can be given just once weekly. So that’s a tremendous convenience to the patient.
Specific mouse mAbs can be routinely generated in large amounts with the use of hybridoma technology. However, mouse mAbs cannot be used for therapy in human due to their immunogenicity. Advances in chimerization and humanization technologies have dramatically improved the performance of mAbs. Recently the use of human antibody-producing transgenic mice and phage display technologies have allowed the development of fully human mAbs.
Chimeric antibodies are made by fusing variable domains from one species, such as a mouse, with constant domains from another species, such as a human being. With such biotechnical manipulation, chimeric antibodies retain the foreign antibody’s antigen specificity and affinity. The development of chimeric and humanized mAbs is facilitated by molecular biology tools like recombinant DNA and fusion technology (not shown here) Note that a fusion protein is a protein consisting of at least two domains that are encoded by separate genes that have been joined as a single unit Structural modifications such as glycosylation and pegylation are introduced herein as formulation factors
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