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Friday, December 6, 2013

Treatment of peanut allergy with omalizumab

Peanut allergy is a well known food allergy estimated to include 3-4% of the US population and accounts for a disproportionate number of severe allergic reactions. The vast majority of food allergy death is related to peanut allergy and is often ingested accidentally despite strict food avoidance. Peanut allergy sensitivity often fails to diminish over time compared to other food allergens causing a lifetime of anxiety and food avoidance for patients and families. The only effective treatment option for this epidemic other than food avoidance is ready access to injectable epinephrine. 

Recent clinical trials using double blind, placebo controlled food challenges (DBPCFC) have reported success with allergen immunotherapy and desensitization with common food allergens including peanut. Although long term tolerance can be achieved with daily intake, most patients experienced mild to severe symptoms including anaphylaxis which occurred in up to 25% of patients with a high peanut specific IgE. Nevertheless, these trials demonstrate that oral food challenge is a useful method for treating food allergies by increasing the threshold for tolerance with possible resolution.

Schneider et al hypothesized that treatment with an anti-IgE monoclonal antibody (mAb) such as omalizumab may contribute to a more rapid desensitization with greater success (Journal of Allergy and Clinical Immunology 2013; 132(6): 1368-1374). Omalizumab binds free IgE which inhibits allergic reactions and is currently approved for older children and adults with moderate to severe asthma. 

The authors administered the drug prior to and during oral peanut desensitization to 13 children who failed initial DBPCFC at low doses (< 100 mg of peanut flour). After pretreatment, all subjects tolerated initial desensitization doses given on the first day, including the maximum dose of 500 mg of peanut flour and 12 subjects reached the maximum daily dose of 4000mg/day within a median time of 8 weeks, at which point omalizumab was discontinued.  The 12 subjects continued the 4000mg/day of peanut flour and subsequently tolerated a challenge of 8000 mg which is up to 400 times the dose that was tolerated before desensitization.  Of the 13 subjects, 6 experienced mild or no allergic symptoms, 6 had a grade 2 reaction, and 2 had a grade 3 reaction which all responded rapidly to treatment. 

These results suggest that omalizumab can facilitate a more rapid oral desensitization in high risk patients with high peanut specific IgE. Schneider’s results provide strong evidence that omalizumab can effectively reduce allergic reactions and expedite rapid oral desensitization.  Larger studies are currently under way to confirm the beneficial role of omalizumab in facilitating oral peanut desensitization.

Questions for the authors:

Could this treatment be used for other severe allergic diseases not yet indicated?  Could longer treatment with omalizumab prevent or reduce other side effects such as eosinophil esophagitis?

Further studies would be needed to determine whether this approach can be applied to other severe allergic diseases.  We don't know if  longer treatment with omalizumab would reduce reactions during desensitization since this was not part of the study.

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