New Study Shows Continuing Hope for Oral Peanut Allergy Tx
Sublingual desensitization therapy appears to ease peanut allergy, with better results the longer therapy continues, a small randomized trial showed.
After 44 weeks of gradually escalated daily doses, 70% of the 20 individuals tested could handle at least 10 times more peanut powder than they could at first, David M. Fleischer, MD, of National Jewish Health in Denver, and colleagues found.
By comparison, 15% reached the same threshold on challenge after getting only placebo (P<0.001), the group reported in the January issue of the Journal of Allergy and Clinical Immunology.
While encouraging, the effect of sublingual immunotherapy (SLIT) at 44 weeks appeared to be modest desensitization that didn't reach the threshold of 5 g without symptoms, which "might not provide clinically relevant protection," the group warned.
But the tolerance level among the responders continued to climb after a further 24 weeks of therapy, such that three could eat 5 g of peanut powder -- the equivalent of about 20 peanuts -- and two could consume twice that.
"These data suggest continued long-term therapy with peanut SLIT might confer reduced reactivity to peanut after further desensitization, allowing for protection against accidental ingestions, which are reactions to less than 100 mg of peanut protein in general," the group wrote.
Nevertheless, the treatment isn't ready for use in the general population, they warned.
Another randomized trial of peanut oral immunotherapy in children also suggested good results, but those researchers likewise warned against adoption in the clinic just yet. Oral immunotherapy is similar to SLIT but uses higher doses of solids versus the lower doses of liquids with the sublingual route.
With a modest effect and some risks, further study is needed to better understand the safety profile and how to improve adherence to SLIT, Fleischer's group acknowledged.
Symptoms occurred with 40% of the oral immunotherapy doses and less than 1% of the placebo doses, but most were oral-pharyngeal symptoms. Only 1% required any treatment.
One patient needed albuterol; another needed an oral antihistamine and epinephrine for grade I anaphylaxis at home and subsequently discontinued therapy. Ten couldn't finish treatments because of fear, poor compliance, or perceived lack of efficacy.
The findings overall, though, suggested a "favorable" safety profile of oral immunotherapy for peanut allergy, according to the researchers.
Their National Institutes of Health-funded Consortium of Food Allergy Research (CoFAR) trial included 40 individuals ages 12 to 37 with proven allergy to peanut but no history of severe anaphylaxis to it.
The participants were randomized to placebo or immunotherapy with liquid peanut protein started off at just a tiny fraction of a microgram, with in-office escalations every 2 weeks to doses that were then taken daily at home atop a peanut-free diet.
The median successfully-consumed dose at the 44-week oral challenge didn't differ significantly between groups, though it rose in the active treatment group (371 versus 21 mg, P=0.01) and not in the controls compared with baseline (146 versus 71 mg, P=0.14).
Most of the 14 SLIT-group participants who met the primary endpoint of tolerance to a 5-g peanut challenge or at least a 10-fold increase in their tolerance level did so at a dose of less than 500 mg.
Among these responders, the tolerance level climbed from 3.5 mg at baseline to a mean of 496 mg at 44 weeks and then to 996 mg after a further 24 weeks of unblinded maintenance treatment (P=0.05 versus week 44 and P=0.009 versus baseline).
All remained responders at week 68, but none of the others (except 44% of the crossovers from placebo at unblinding) became responders with longer treatment.
Peanut-specific antibody levels rose during active treatment, but without a significant difference at week 44 compared with the placebo group or among responders versus nonresponders.
The investigators cautioned about the small sample size and noted that the results wouldn't necessarily generalize to severe peanut allergy with a history of life-threatening reactions.
Another limitation was the definition of response, which excluded some with a numerically large but not 10-fold increase in the successfully tolerated peanut dose on challenge because they started with a relatively high baseline tolerance, but included some with relatively small numeric increases because of their low baseline dose.
Also, the results reflected only desensitization, not long-term tolerance or ability to start eating peanuts as a part of normal diet, the group warned.
The study was supported by the National Institute of Allergy and Infectious Diseases as well as the National Center for Research Resources and the National Center for Advancing Translational Sciences.
Fleischer reported having received grants from the National Institutes of Allergy and Infectious Diseases, consulting for sanofi-aventis, being employed by National Jewish Health, and receiving royalties from UpToDate.
Primary source: Journal of Allergy and Clinical Immunology
Source reference:
Fleischer DM, et al "Sublingual immunotherapy for peanut allergy: A randomized, double-blind, placebo-controlled multicenter trial" J Allergy Clin Immunol 2013; 131: 119-127.
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Crystal Phend
Staff Writer
Crystal Phend joined MedPage Today in 2006 after roaming conference halls for publications including The Medical Post, Oncology Times, Doctor's Guide, and the journal IDrugs. When not covering medical meetings, she writes from Silicon Valley, just south of the San Francisco fog.