The prevalence and recognition of peanut allergy have been on the rise in the U.S. and other Western countries during the past decade. To avoid accidental exposure, labeling has been added to prepackaged foods to indicate if the product was made in a peanut-containing facility and child-care centers increasingly prohibit peanut-containing products. Recent studies (e.g., the Learning Early about Peanut [LEAP] trial) have shown that early introduction of peanuts reduces the development of peanut allergy in children. As a result, guidelines have shifted from elimination to early introduction of infant-safe forms of peanut to prevent the development of peanut allergies. But, evidence is limited for an effective treatment for patients with existing, and often life-threatening, peanut allergy.
In a randomized-controlled study published in NEJM, Vickery and colleagues examined the safety and efficacy of AR101, a manufactured peanut flour preparation, in 551 children and adults with peanut allergies. During the 1-year trial, participants who had a dose-limited allergic reaction to no more than 100 mg of peanut protein (about one third of a peanut kernel) underwent supervised dose escalation with either AR101 or matching placebo. Participants who completed the trial underwent an exit food challenge with increasing doses of peanut protein. The authors defined one peanut kernel as containing 300 mg of peanut protein.
In the primary analysis of 496 children and adolescents aged 4-17 years, significantly more participants treated with AR101, as compared with placebo, successfully ingested a single dose of at least 600 mg of peanut protein with no more than mild symptoms (67% vs. 4%). However, 11% of AR101 recipients compared with 2% of placebo recipients withdrew from the trial due to adverse events. Furthermore, during the intervention period, 14% of patients who received AR101 were treated with epinephrine for reactions thought to be related to peanut exposure, compared with 6.5% in the placebo group.
What are the practical implications of these results regarding future treatment options for patients with peanut allergies? Although we now have an oral medication that can deliver a peanut allergen in a small, precise quantity and can effectively induce desensitization, the safety data should give us pause before running to try this effective, potent therapy in the clinic. Additionally, in an accompanying editorial, Dr. Michael Perkins highlights an ongoing concern: “The major concern regarding immunotherapy is that the allergen tolerance that is induced will be temporary and lost if regular consumption ceases.” He adds that the investigators did not attempt to establish a duration of therapy for which allergen tolerance is maintained.
How long immunotherapies need to continue and when patients can declare themselves free from peanut allergy remain important clinical questions.
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Angela Castellanos is a general pediatrician and editorial fellow at the NEJM.