Kate Johnson

February 27, 2013

SAN ANTONIO, Texas — Sublingual immunotherapy for peanut allergy might help induce clinical tolerance, according to an interim analysis presented here at the American Academy of Allergy, Asthma & Immunology (AAAAI) 2013 Annual Meeting.

This is the first report of such a response.

"It's unclear whether it's true tolerance," said presenter Edwin Kim, MD, from the University of North Carolina at Chapel Hill. "Larger and longer studies are needed before peanut sublingual immunotherapy can be considered as a therapeutic option."

Wesley Burks, MD, senior investigator of the study and current chair of pediatrics at the University of North Carolina at Chapel Hill, told Medscape Medical News that the definition of tolerance is still hotly debated in the field of allergy, and the word itself can be misleading.

"We're really careful not to use the word 'tolerant' when we talk to parents. We tell them the child is able to eat the food, but not that it's a permanent thing, and then we continue to follow the child," explained Dr. Burks, who is the outgoing AAAAI president. "We are continuing to follow the children in this study."

Positive Result

This work extends the double-blind placebo-controlled study in which 18 children underwent 6 months of dose-escalation followed by 6 months of maintenance sublingual immunotherapy with peanut protein (J Allergy Clin Immunol. 2011;127:640-646).

The current study involves the 11 patients who continued maintenance immunotherapy up to 36 months, using a 2 mg dose of peanut protein, and who passed a double-blind placebo-controlled food challenge with 5 g of peanut protein.

These subjects were told to withhold peanut immunotherapy for 1 month and return for an identical oral peanut challenge.

Five of these patients passed the second challenge after 1 month without peanut sublingual immunotherapy, meeting the study's definition of clinical tolerance.

Clinical improvements after peanut skin prick testing were seen in all 11 patients.

Table. Peanut Skin Testing Findings for All 11 Patients

Measure Baseline 36 Months
Median wheal size 9 mm 6 mm
Immunoglobulin (Ig)E* 31 KU/L 9.8 KU/L
IgG4 0.3 mg/L 14.9 mg/L
IgE/IgG4 ratio 104 1.08
*Did not reach significance
†Increased significantly

Dr.Burks cautioned against reading too much into the results. "It just means that after a month off therapy, they can tolerate peanuts in their diet and they're eating peanuts an average of about 3 or 4 times a week. It doesn't say anything about long-term at all," he said.

Session moderator Stacie Jones, MD, from Arkansas Children's Hospital in Little Rock, agrees that it is too early to pass judgment on immunotherapy, either oral or sublingual.

We're so excited, but we're not ready for clinical practice.

"This is all incredible, we're so excited," she told Medscape Medical News, "but we're not ready for clinical practice because we don't know the duration, we don't know the timing, and we don't have the nuances yet of which patient needs what therapy."

Dr. Jones noted that "we need to be able to tailor that better. If we don't, we sacrifice safety and we have patients playing around once they're considered tolerant.... We better get this therapy right before its ready for the clinic."

One of the delegates attending the meeting, James Thompson, MD, an allergist in private practice in Chicago, Illinois, said that his patients are more likely to stick with sublingual immunotherapy therapy than oral therapy.

"With the oral, you are still getting a lot of side effects; you don't get as many with sublingual immunotherapy," he said during an interview. "The family and the patient will tolerate it better."

But Dr. Thompson pointed out that it depends on the goal of therapy. "If your end point is to have someone consume milk and peanuts regularly, then you might try the oral, but if you're just trying to keep them from having an unexpected severe allergic reaction, then you should probably just go with sublingual. This is often good enough for most parents. They don't care if the kid can eat peanuts, they just want to make sure that if he eats something by mistake or sits at the nonpeanut-free table, he's going to be okay," he explained.

The investigators, Dr. Jones, and Dr. Thompson have reported no relevant financial relationships.

American Academy of Allergy, Asthma & Immunology (AAAAI) 2013 Annual Meeting: Abstract 468. Presented February 24, 2013.