Peanut allergy treatment shown to be long-lasting

Researchers from the University of North Carolina have demonstrated that a peanut allergy treatment called sublingual immunotherapy, or SLIT, is effective and safe, offering durable desensitisation to peanuts in peanut-allergic children. The results of their four-year, phase 2 clinical trial have been published in The Journal of Allergy and Clinical Immunology.

SLIT is a treatment using a tiny amount of peanut protein that is the equivalent of only 1/75th of a peanut kernel. It is taken under the tongue, where it is absorbed into the body, as opposed to Palforzia peanut oral immunotherapy, which requires patients to eat medical-grade peanut flour each day.

In a 2011 pilot study of peanut SLIT, Associate Professor Edwin Kim and his group showed for the first time in a placebo-controlled study that desensitisation, defined as an increase in the amount of peanut it takes to cause an allergic reaction, was possible with peanut SLIT. When these children were kept on the treatment for five years, they showed that the desensitisation was maintained, the treatment remained safe, and a small group of these patients could stop treatment for a month and still be desensitised.

The current trial was designed to answer two key questions that emerged from this first study: could higher doses be more effective, and how long-lasting can the treatment effect be? First, the dose of the peanut SLIT was increased from 2 mg to 4 mg. Second, patients finishing peanut SLIT who were desensitised and considered to be protected against accidental exposures of peanut were taken off the peanut SLIT treatment for anywhere from one to 17 weeks to measure how long the protection would last.

Of the 54 peanut-allergic children participating in the study, 47 completed the treatment with 70% showing protection against accidental exposures of peanut (>800 mg peanut, ~3 peanuts) and 36% showing full desensitisation (5000 mg of peanut, ~16 peanuts). The average threshold after treatment for children in the study was 2723 mg of peanut, compared to 1700 mg using the 2 mg dose in the pilot study.

According to Kim, the study shows that SLIT can desensitise the majority of peanut-allergic children, providing a buffer of protection against any unexpected situations where cross-contamination and accidental ingestion may occur. Most importantly, the clinical study suggests the treatment is safe, with only 4% of the higher doses causing side effects and most of these involving a temporary itch in the mouth. No side effects required treatment with epinephrine (EpiPen).

Modelling of the time off peanut SLIT showed that, on average, it would take 22 weeks before the desensitisation would wear off and the patient would become reactive to small amounts again. Kim said this not only provides reassurance in the case of missed doses, but also may point to novel dosing strategies in the future.

“Sublingual immunotherapy is not a cure, but by striking that balance of protecting against allergic reactions while still being easy and safe to do, it could have the potential to help a lot of peanut-allergic patients and their families,” he said.

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