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Focusing on Glycans as Novel Drugs and Therapeutic Targets

Biotherapeutic protein producers have taken pains to ensure consistency in glycosylation of recombinant therapeutic proteins, mostly due to the potential immunogenic properties of non-self glycans, the impact of glycosylation pharmacokinetics, and glycan in vi

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Biotherapeutic protein producers have taken pains to ensure consistency in glycosylation of recombinant therapeutic proteins, mostly due to the potential immunogenic properties of non-self glycans, the impact of glycosylation pharmacokinetics, and glycan in vivo functionality. But according to an article published in the January 3 edition of Science, researchers are increasingly turning to modifications in these sugars that normally decorate proteins to develop clinically effective therapeutics.

In the January 3 Science article, titled “Emerging Principles for the Therapeutic Exploitation of Glycosylation,” Martin Dalziel, Ph.D., and colleagues at Oxford University discuss what researchers have, to date, learned about glycans in the context of pathogen invasion, cancer and autoimmunity, and congenital diseases. The authors reveal recent advances in recombinant cellular biosynthetic technologies that can produce defined “glycoforms,” and they describe several clinically effective therapeutics that have already been developed with such glycoforms.

The authors point out that glycans are not only essential to glycoprotein folding, cellular homeostasis, and immune regulation but are involved in multiple disease conditions. An increased molecular and structural understanding of the mechanistic role that glycans play in these pathological processes has driven the development of therapeutics and illuminated novel targets for drug design.

This knowledge has enabled the treatment of metabolic disorders and the development of antivirals, shaped cancer and viral vaccine strategies, and led to the development of specific drug glycoforms—for example, monoclonal antibodies—with enhanced potency.

In one such application, Dr. Dalziel and his colleagues note that HIV vaccine development is based on targeting the viral carbohydrate coat. This carbohydrate coat, the investigators have shown, remains remarkably constant despite huge variation in the underlying viral protein. The researchers have also been investigating using microbial mimics of this shield to elicit antibodies that can protect against the virus, showing that broadly neutralizing antibodies can recognize this shield despite structural variation in these “self” carbohydrate structures.

The investigators say they have also structurally characterized how different glycans impact antibody Fc structure and how they can be manipulated to fine-tune antibody effector functions. In addition, they say, they are developing a new approach for enhancing therapeutic antibodies against cancer that involves deactivating competing endogenous antibodies that can limit the potency of anticancer antibodies.

Methods, they and other authors have pointed out, are now becoming available that allow the production of recombinant monoclonal antibodies, rMAbs, bearing preselected oligosaccharides (glycoforms) to provide maximum efficacy for a given disease indication.

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Related questions

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Another obstacle to discovering new PPI inhibitors is the lack of libraries designed to hunt for them, points out Philippe Roche, PhD, senior scientist at the Integrative Structural and Chemical Biology team at the Cancer Research Center of Marseilles, France. “If you screen PPIs using libraries that were designed for kinases or GPCRs, that’s why you don’t get a lot of good results,” he says. To that end, his group began assembling a library focused on orthosteric inhibitors of PPIs. The result was 2P2Idb, a hand-curated, structural database cataloguing orthosteric inhibitors of PPIs for which the interface had been 3D characterized. From analyzing these known PPI inhibitors, and what structures they had in common, Roche and his colleagues developed a model to predict whether compounds would likely inhibit PPIs. Using this method, 2P2Idb creates an enriched screening library that dramatically increases the hit rate compared to standard libraries. Having proven their success with a small library of 1600 compounds, they are in the process of expanding the library to 10,000 compounds. Once that’s published, “the idea is to make this library available to labs around the world,” Roche says. “We will provide the library free of charge for people to be able to screen PPI targets.”

Source: www.genengnews.com ↗
02How stable is the antibody?

A crucial question often addressed during preclinical development focuses on the in vivo stability of therapeutic antibodies. Increasing the half-life of a therapeutic antibody has several benefits ranging from higher treatment efficacy to increased advantages for the patients who will have a fewer number of therapy sessions and a reduced cost. Given these compelling benefits, following the identification of therapeutic antibodies with the desired specificity, developers usually subject them to a refinement step to increase their stability. This process is often hindered by the lack of reliable experimental tools to predict the half-life of antibodies in patients. The major hurdle of using mouse models to predict antibody stability in the serum lies in the way immunoglobulin proteins are processed by the organism. In mammals, most proteins circulating in the serum undergo constant uptake by endothelial cells and are routed through the endosomes to the lysosomal compartment for degradation. In the endosomes, immunoglobulin G (IgG) proteins are recognized and bound by a transmembrane protein, called the neonatal Fc receptor (FcRn), which mediates their recycling to the plasma membrane and subsequent release back into the serum. As a result, the half-life of IgGs are significantly extended by this mechanism. Since most therapeutic antibodies belong to the IgG class, this recycling system is very relevant for their relative stability in the body. Remarkably, the relative affinity between IgGs and FcRn is extremely disparate between different species, with the mouse receptor showing a much higher affinity than its human counterpart.

Source: www.genengnews.com ↗
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Peptide Therapy Guide Editorial Team

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