A Totally Novel Approach to Asthma Therapy
The FDA recently approved a completely new type of anti-allergic treatment. Omalizumab (Anti-IgE), a humanized monoclonal antibody targeted against the receptor binding region of IgE, was given an indication for adults with moderate to severe allergic asthma. It seems to work by non-specifically binding serum IgE and "disarming" the mast cell. Anti-IgE has been shown to decrease serious exacerbations by about 50% in allergic asthmatics already being treated with inhaled steroids. This represents a significant advance in our management of these severe asthmatics, but it is not a "magic bullet" at least in terms of asthma therapy.
The reason for this has to do with the complexity of asthma, a disease that some thought leaders would rather call a "syndrome." That is, IgE may have greater or lesser importance in the pathphysiology of a given asthmatic, leading to spectacular results in some patients and modest results in others. Still, given the fact that asthma kills thousands of Americans per year, Anti-IgE has generated a great deal of excitement in those that treat asthma.
However, even more excitement surrounds this drug because of its potential benefit in other allergic diseases such as food allergy. There are two reasons why allergists are so interested in this molecule in this regard. First, anaphylaxis via food allergy is almost solely an IgE-mediated disorder, so Anti-IgE should be extremely effective. Secondly, we currently have no effective treatment for food allergy besides avoidance (it is essentially impossible to avoid accidental ingestion of peanuts, for instance). In fact, a recently published study suggested that a similar Anti-IgE molecule could prevent anaphylaxis resulting from accidental peanut ingestion. This drug may also make the use of standard allergen immunotherapy safer and much more efficient, since it's side effects are mainly IgE-mediated. In addition, Anti-IgE may be of use in certain clinical situations of drug and insect allergy. Unfortunately, these and other indications for Anti-IgE are years away.
As far as the practical use of Anti-IgE for asthma, it will be given to those adult allergic asthmatics having significant exacerbations while on multiple controller therapies (e.g. inhaled steroids, long-acting bronchodilators and leukotriene modifiers). It will be given SQ on a q2 week or q4 week basis, with the dose being based on weight and pre-treatment serum IgE levels. In clinical trials there has been a very small number of moderate anaphylactic-appearing reactions to Anti-IgE injections, so the drug should be given in a physician's office at least until more safety data is collected. Other safety data looks very good. There was, however, a higher cancer rate in those receiving study drug. The tumors were of a variety of cell types and were age-appropriate. These cases were reviewed by an independent panel of oncologists, who found that it was very unlikely that the tumors were treatment related.
Finally, the cost of this drug will limit its use in the early going. A reasonable estimate would be approximately $1,000 per month. The cost to a given insurance carrier will probably equal the savings provided by fewer hospital admissions. The future use of this drug in childhood asthma, where it appears to be even more effective and drug costs will be lower due to weight, shows a great deal of promise. The use of Anti-IgE for other indications will require a great deal of future study and a reduction in the cost of this therapy to make it feasible.