Anti-IgE therapy for asthma

Published on January 17, 2013   24 min

A selection of talks on Pharmaceutical Sciences

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Hello. My name is Andrew Menzies-Gow. I'm a consultant respiratory physician at the Royal Brompton Hospital. I'm going to talk to you about Anti-IgE therapy for asthma.
During my talk, I'll cover the evidence for omalizumab therapy in asthma, the current situation within the United Kingdom, and evidence from real life studies. An important question that I'm often asked about omalizumab therapy is, how long patients should start it and stay on it, if it is of benefit?
We know that the majority of asthmatics attacks are also atopics. They have positive skin tests for common aeroallergens. In large surveys of asthma from across the world, up to 90% of asthma occurs in association with allergy. We also know that allergen specific IgE can both initiate and maintain the inflammatory response which is characteristic of asthma and associated with Th2 inflammation and then infiltration of eosinophils into the airway mucosa. Therefore, IgE becomes a very logical target for asthma therapy. Whenever we think about blocking part of the immune system, we need to be certain that it's going to have relatively few side effects and not cause a catastrophic failure of the immune system. We know that the physiological root of IgE appears to be fighting parasitic infections, primarily anti-nematode infections. Therefore, certainly in the western world, blocking IgE is likely to prevent allergic inflammation with no significant impact on the immune system's ability to fight infections.
Anti-IgE is a monoclonal antibody that's injected subcutaneously. It finds its way to the serum where it binds to free IgE and produces multimers that are removed by the reticular endothelial system. It prevents IgE binding to the surface of mast cells, so it very quickly depletes pre-serum IgE, but it can take up to eight weeks before the levels of IgE on the surface of mast cells and basophils start to decrease, which is why the treatment takes at least 8 to 16 weeks before we see any improvement in asthma symptoms. Importantly, anti-IgE does not bind to IgE that's already on the surface of mast cells or basophils. Therefore, it can't induce an anaphylactic reaction by directly cross-linking IgE on the surface of mast cells and basophils.