11 September 2019

Peanut protein drops may improve tolerance

Allergies Research

Giving children with peanut allergies a tiny drop of peanut protein under the tongue each day could substantially improve their tolerance, a proof-of-concept study suggests.

In the study, 48 children with peanut allergies received a 2mg peanut protein drop sublingually daily. The drop was held under the tongue for two minutes.

This treatment continued for five years, with some patients dropping out at three years if their peanut-specific IgE levels fell below a set threshold.

By the end of the study, two-thirds of the children receiving peanut sublingual immunotherapy (SLIT) could eat 750mg of peanut protein or more without experiencing symptoms. (In other words, they could safely tolerate food products that were labelled as containing “traces of nuts”.)

Twelve patients could comfortably consume 5g of peanut protein – the equivalent of up to 20 peanut kernels. Ten of these patients showed sustained tolerance to peanut protein a few weeks after stopping SLIT.

The open-label study was led by Assistant Professor Edwin Kim from the UNC School of Medicine in the US.

The trial suggested that SLIT was a reasonably safe way to desensitise children to peanuts, the authors said.

Over the five years of the study, around 75,000 total doses of peanut protein were given and only 5% of doses were associated with symptoms.

The most common symptom was oropharyngeal itching, which generally resolved spontaneously. None of the symptoms resulted in a child needing epinephrine (adrenaline) during the trial.

The tiny doses of peanut protein used in SLIT made it less effective than oral immunotherapy, but SLIT was also less likely to land the patient in the ED, the authors said.

A meta-analysis of 12 studies published in The Lancet in April showed that, while oral immunotherapy increased peanut tolerance, it also tripled the risk of anaphylaxis and doubled the risk of epinephrine use.

Dr Derek Chu, an allergist from McMaster University in Canada and the lead author of this meta-analysis, said this latest peanut SLIT study was “encouraging” and showed that SLIT could be “another possible future treatment option for peanut allergy”.

“These data support the need for large, well-conducted randomised controlled trials in peanut SLIT to help clarify the full risks and benefits of this approach,” he said.

There are currently no approved treatments for peanut allergy and ASCIA advises parents to simply eliminate peanuts from their child’s diet.

The FDA in the US is currently considering whether to approve one oral immunotherapy product for peanut allergy.

Similar to sublingual immunotherapy, oral immunotherapy involves incrementally increasing the amount of a food allergen over time to desensitise the individual. But, with oral therapy, the allergen is swallowed and enters the system via the gastrointestinal tract whereas sublingual immunotherapy involves absorbing the allergen via the buccal mucosa.

There are several trials in Australia and around the world for peanut oral immunotherapy.

A combination of peanut flour and the probiotic Lactobacillus rhamnosus was trialled as an oral immunotherapy in 28 children in 2013 by The Murdoch Children’s Research Institute in Melbourne. Around 80% of children were no longer allergic to peanuts at the end of the 18-month trial.

Researchers at Alfred Health in Melbourne are partnering with Australian biotechnology company Aravax to run a phase II trial of their peanut oral immunotherapy, which involves giving patients with allergies increasing doses of peanut peptides.

Journal of Allergy and Clinical Immunology, September