In this phase 1 safety study, we have shown that participants allergic to multiple foods were safely and rapidly desensitized to up to five food allergens simultaneously, using a rush OIT protocol with concomitant treatment with omalizumab. To the best of our knowledge, this is the first study to use omalizumab with OIT to multiple allergens simultaneously. These findings are particularly relevant considering the already high (~30%) and likely growing number of food allergic participants who are sensitized to more than one food allergen [3, 53–56].
This study was designed as a proof of concept, open-label phase 1 study, with safety measurements as the primary endpoint. The rate of reactions observed in the rush mOIT group was similar to a group with the same eligibility and demographics undergoing mOIT in a previous study without omalizumab, despite the more rapid desensitization schedule . The goal of adding omalizumab in this phase 1 study was primarily to enable rapid desensitization rather than to suppress allergic symptoms during OIT.
As the half-life of omalizumab is 24 days, we further hypothesized that any protective safety effect might wane over time. Participants were observed closely for the development of symptoms, including hives, worsening of eczema, or wheezing after omalizumab discontinuation (at 8 weeks after initial dose escalation), and were instructed to keep a diary of food allergy symptoms throughout the study. Our data show that the home reaction rate actually went down after 24 weeks of therapy from 11 to 3 per 100 doses (p < 0.0001) (Figure 4). This increase in safety could relate to the fact that participants were not up-dosing anymore at that point. However, the only use of epinephrine occurred shortly after the participant had reached the maintenance phase, thus vigilance should not be relaxed at any point. Rescue epinephrine was also required during the maintenance phase of previous rush studies using omalizumab (2 of 2 and 1 of 4 in peanut and milk rush OIT respectively) [28, 52].
In addition to the safety data, this phase 1 study of rush mOIT provides initial preliminary evidence of increased dose tolerability. The median time at which participants on rush mOIT reached their maintenance dose (4000 mg per allergen) was 67 weeks earlier than that reported in a previous report on mOIT without omalizumab . This represents a difference of about 34 dose escalations and about 67 additional weeks of enrollment. This might be relevant from a pharmaco-economic perspective. Considering a cost per visit in 2013 of approximately $160 [approximate cost of an office open food challenge per MediCare or public health insurance in Canada (RAMQ)], those 34 extra visits represent a minimal additional cost of approximately $5,440 in 2013 . This could possibly offset the cost of omalizumab at the current time, which varies between $2,164 and $10,824 for 16 weeks, depending on the patient’s weight and total IgE levels. Furthermore, these calculations do not take into account the additional cost and impact of absenteeism from school and work for the participant and his/her parents during these approximate 34 additional visits . However, one should be cautious when comparing these two phase 1 trials as the dose progression schedules were different. A phase 2 study comparing omalizumab to placebo in participants with a similar dosing schedule is needed to truly assess the efficacy gained from the addition of omalizumab to mOIT.
There are limitations to this study. Oral immunotherapy regimens were customized to the participant’s food allergies. This has led to some diversity when comparing the composition of specific food allergies between subjects. However, no one food allergen was found to be associated with greater dose tolerability or safety. This is consistent with one of the key long term goals of the study which was to begin to develop customized, patient-based, regimens for oral immunotherapy that could be tested for safety, and dose tolerability.
Importantly, our study showed desensitization but not tolerance. Clinical tolerance is proven by demonstrating sustained unresponsiveness to the food after stopping the maintenance dose for a prolonged period of time. Future phase 2 trials on the use of omalizumab combined with OIT will be useful to see if omalizumab affects this outcome.
Our cohort did not include subjects with high total serum IgE levels as this is sometimes the case for children with multiple food allergies. Three subjects had total serum IgE slightly greater than 1500 kUa/L and received the maximum dose of Omalizumab (600 mg every 2 weeks). The optimal dosing for subjects with higher levels would require further study.
Serological analyses were performed for peanut to allow for consistent comparisons between participants, as this was the most frequent allergen. The serologic changes after 52 weeks of therapy were identical to those previously reported in subjects undergoing non-rush OIT (without omalizumab) [36, 58].
In conclusion, the data from a single site, phase 1 study demonstrate that a rush OIT protocol to multiple food allergens using adjunct omalizumab can be performed safely in a hospital setting. At this time, rush mOIT is an experimental treatment and should be conducted by trained research personnel with immediate access to emergency equipment. Phase 2, blinded, multicenter trials are needed to continue to determine safety and efficacy parameters of rush mOIT in larger numbers of multi-sensitized participants.