Kate Johnson

March 08, 2012

March 8, 2012 (Orlando, Florida) — Oral immunotherapy for peanut allergy results in more extensive immunologic changes than sublingual therapy, according to a study reported here at the American Academy of Allergy, Asthma and Immunology 2012 Annual Meeting.

Researchers compared 2 previously published studies, each conducted independent of the other and each looking at a single treatment.

The findings from the comparison suggest that oral immunotherapy (OIT) is more effective than sublingual immunotherapy (SLIT), said Stacy Chin, MD, from Duke University Medical Center in Durham, North Carolina, who presented the findings in a featured poster.

"At baseline, 1 year, and 2 years, immunologic changes occur in both SLIT and OIT, compared with placebo, but we see more extensive changes in the first 2 years with OIT than with SLIT," she told Medscape Medical News.

Safety and adverse-effects data were not presented, but the OIT therapy did seem to carry a heavier burden, Dr. Chin reported.

Dr. Chin and colleagues compared a double-blind placebo-controlled trial of OIT vs placebo (J Allergy Clin Immunol. 2011;127:654-660) with a double-blind placebo controlled trial of SLIT vs placebo (J Allergy Clin Immunol. 2011;127:640-646.e1) in peanut-allergic children. The mean ages of the study populations were 5.3 years and 6.3 years, respectively.

Median baseline peanut immunoglobulin (Ig)E was 58.5 kU/L in the OIT group and 61.7 kU/L in the SLIT group. Median baseline skin-prick test results were 14.5 mm and 11.5 mm, respectively.

Treated patients in the OIT group built up to a maintenance peanut protein dose of 4000 mg daily over 11 months, followed by a double-blind placebo-controlled food challenge (DBPCFC) of peanut protein 5000 mg after 4 weeks of the maintenance dose.

Treated patients in the SLIT group built up to a maintenance dose of 2 mg over 6 months, followed by a DBPCFC of 2500 mg after an additional 6 months on maintenance.

A comparison of the 2 studies showed that OIT resulted in greater changes in peanut-specific IgE (P = .03), IgG4 (P < .001), and basophil reactivity (P < .01). On skin-prick testing, serum peanut IgA, IgG, and T regulatory cells were not significantly different.

At 1 year, for subjects remaining in the studies, those receiving OIT were 3 times more likely to pass the 12-month desensitization than those receiving SLIT (18 of 20 subjects vs 8 of 19 subjects). The median dose tolerated by OIT subjects was 5000 mg and by SLIT subjects was 1710 mg.

At 1-year, "there was a greater threshold of desensitization in subjects on OIT compared with those on SLIT," said Dr. Chin. "But it's still early.... These studies go on for very many years."

Safety data, which she did not present but which were reported in both studies, suggest that SLIT is better tolerated than OIT, she said.

"With SLIT, the majority of side effects seem to be oropharyngeal pruritus that's self-limited, that resolves on its own. No one has had to use epinephrine at all with home dosing. With OIT, they tend to have an increased rate of GI symptoms, and a greater percentage of children do drop out because of those symptoms. In this study and other OIT studies, there have been a handful of patients who have had reactions on their maintenance dose, which they normally tolerate, but they happen to be on their menstrual cycle, or have a febrile illness, or have been exercising in close proximity to the dose and have a reaction," Dr. Chin noted.

Weighing efficacy and adverse effects is a difficult process, especially when considering different study protocols. Dr. Chin said she doesn't necessarily consider OIT safer.

"As we learn more about different factors that play into adverse reactions with OIT, we can provide anticipatory guidance to subjects, so we've had fewer reactions as we go along. I think it's still early to directly compare them head to head."

She said many questions remain about SLIT.

"I still don't think we know what the right dose is for SLIT. We've just started another study in which we doubled the dose from 2 to 4 mg. I think SLIT is great in that it does have a very nice safety profile, but there are a lot of things we still don't know. It seems to be pretty safe to increase the dose at home — there seem to be fewer side effects, it's easy to travel with, patients don't have to take it on a full stomach (which you have to do with OIT). We'll have to see if we get the same results."

After viewing the poster, Peter Arkwright, MD, PhD, a pediatric allergist at Royal Manchester Children's Hospital in Manchester, United Kingdom, said: "I think that [SLIT] is still experimental. It's a possible way forward. People should be enrolled in trials rather than seeing clinicians in the clinic and having the treatment there."

The fact that SLIT is not approved by the US Food and Drug Administration is mirrored in the United Kingdom; as in the United States, it is being used off-label. "It's not being used for peanut allergy outside of clinical trials, but for milk and egg, it is being used in clinical practice," he said.

In this context, it is important that patients are properly informed about the treatment, Dr. Arkwright added. Whatever treatment you do, you should let them know it's experimental — we still don't know whether it's going to work, or the optimal dose or duration, or if it's going to be durable. There are so many questions still to answer, but this study is a step in the right direction."

The study was funded by the National Institutes of Health, Wallace Research Foundation, Food and Allergy Anaphylaxis Network, the Food Allergy Initiative, Gerber Foundation, the Dorothy and Frank Robins Family, and the National Peanut Board. Dr. Chin and Dr. Arkwright have disclosed no relevant financial relationships.

American Academy of Allergy, Asthma and Immunology (AAAAI) 2012 Annual Meeting: Abstract 532. Presented March 4, 2012.

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