I don’t need to tell you, dear reader, that peanut allergy is a big problem. It’s incidence is increasing for unclear reasons, avoidance is difficult, reactions can be severe, even life-threatening, and there is no treatment available for general clinical use. Yet.
Oral desensitization is being done in research settings, as well as by some maverick allergists, and it works for some folks. It is, however, very time consuming and systemic reactions are common. Indeed, many people are unable to complete the desensitization because of reactions.
If we had a way to reduce or eliminate the reactions during desensitization, we could make the process safer and allow more people to be desensitized. Enter omalizumab. Omalizumab is an injectable medication that essentially eliminates the body’s ability to have an acute allergic reaction. (For more on omalizumab and its mechanism, see my old blog post here.)
Studies have shown that omalizumab can protect peanut allergic patients from having reactions to peanuts. The big question has been: If you use omalizumab during a peanut desensitization to prevent allergic reactions, what happens when you stop the omalizumab. A new study in the JACI helps answer this.
This is a small, pilot study with only 13 participants, all of whom had clinical peanut allergy. By pretreating with omalizumab, they were able to have patients tolerate a cumulative dose of almost 1g of peanut flour, about the weight of a peanut, within 8 hours. They then underwent an 8-week dose escalation while continuing the omalizumab, up to 4g of peanut flour per day. During this phase there were a few mild reactions. Then they stopped the omalizumab.
I’ve got to say that takes some guts. I would guess that you really had no idea how the patients would respond off omalizumab, but they did fine, for the most part. Once the omalizumab was stopped, the participants kept taking 4g of peanut flour daily for the next 12 weeks. During this phase, there were more reactions and a couple of patients required epinephrine, but there were some extenuating circumstances. In the end, 11 of the 13 patients continued with regular peanut ingestion, from 10 to 20 peanuts a day.
This is a very promising study. IMHO, this will be the way peanut desensitization makes it in to general clinical use. It also has implications for desensitization of other food allergies.
As usual, there are some caveats. First, the doses of omalizumab used were, in some cases, much higher than those used for the treatment of allergic asthma. Omalizumab is still an incredibly expensive medication and the doses some patients received in this study would be upwards of $5,000 a month or $25,000 for the total study period. Also, some patients still had reactions off omalizumab. Granted, these were not 100% linked to peanut ingestion, but it still does give one pause. Finally, this is a very small study. Fortunately, larger studies are underway to help refine this process. I am looking forward to seeing the results.