Peanut immunotherapy is currently undertaken privately in the UK as well as part of clinical trials in various UK centres. Oral peanut immunotherapy is conducted with either roasted defatted peanut flour or boiled peanut. The only licenced product available at present is Palforzia which was FDA approved in January 2020 and is used extensively in the United States. More recently, Palforzia has received approval from the European Commission for the treatment of peanut allergy in children 4 – 17 years old with a confirmed diagnosis of peanut allergy. This needs to be undertaken in conjunction with a peanut-free diet.
Oral peanut immunotherapy generally starts at very low doses (1 – 25 mg of peanut protein) taken on a daily basis and increased every 2 – 3 weeks until the maintenance dose (generally 200 – 4000 mg of peanut protein) is achieved. This initial escalation phase can take between 6 – 12 months to achieve depending on the tolerance of the individual and the desired maintenance dose. Approximately 70 – 90 % of individuals will achieve the maintenance dose with the rest discontinuing for a variety of reasons including side effects (mainly oral itching and chronic gastrointestinal symptoms including abdominal pain). A minority also exhibit anaphylaxis although no deaths have been described to date. Large phase 3 studies of Palforzia indicate that approximately 60 % of individuals treated with 300 mg peanut flour using an incremental regime are able to tolerate a single 1000 mg challenge (the equivalent of 6 peanuts) after 12 months. Sustained unresponsiveness appears to be more frequent in younger children (infants and toddlers).
Boiling peanuts results in a modified hypoallergenic form which facilitates desensitisation. There are far fewer studies been published looking at this approach but in a pilot study, all 24 children in the active group who completed the 12 month study, achieved the primary outcome of being desensitised to more than 1.4 g of peanut protein (the equivalent of approximately 6-8 whole peanuts). Of these approximately 44% tolerated more than 4.4 g of peanut protein and over 50 % achieved a 4 week period of sustained unresponsiveness.
Oral peanut immunotherapy is associated with an improvement in the participant’s quality of life, particularly in the perceived likelihood of future accidental exposure and in the risk of severe reactions. However, peanut immunotherapy is also potentially life threatening (as a consequence of the initial confirmatory oral food challenge), expensive and time consuming. Moreover, it depends on compliance of the individual (and usually their parents) and can be associated with severe side effects. The majority (approximately three quarters) of individuals who discontinue treatment due to adverse events do so within the first 6 months such as eosinophilic oesophagitis.