Open-label study of the efficacy, safety and durability of peanut sublingual immunotherapy in peanut-allergic children

Abstract

Background:

Studies are limited on the efficacy of peanut sublingual immunotherapy (SLIT). The durability of desensitization after SLIT has not been well described.

Objective:

To evaluate the efficacy and safety of 4 mg peanut SLIT and persistence of desensitization after SLIT discontinuation.

Methods:

Challenge proven peanut-allergic 1–11 year old children were treated with open-label 4 mg peanut SLIT for 48 months. Desensitization after peanut SLIT was assessed by 5000 mg double-blind, placebo-controlled food challenge (DBPCFC). A novel randomly assigned avoidance period between 1–17 weeks was followed by a DBPCFC. Skin prick testing (SPT), immunoglobulins, basophil activation testing (BAT), T_H1, T_H2, and IL-10 cytokines were measured longitudinally. Safety was assessed through patient-reported home diaries.

Results:

Fifty-four participants were enrolled and 47 (87%) completed peanut SLIT and the 48-month DBPCFC per protocol. Mean successfully consumed dose (SCD) during DBPCFC increased from 48 mg to 2723 mg peanut protein after SLIT (p<0.0001), with 70% achieving clinically significant desensitization (SCD >800 mg) and 36% full desensitization (SCD = 5000 mg). Modeled median time to loss of clinically significant desensitization was 22 weeks. Peanut SPT; peanut-specific IgE, IgG4, IgG4/IgE ratio; and peanut-stimulated BAT, IL-4, IL-5, IL-13, IFN-gamma, and IL-10 changed significantly compared to baseline with changes seen as early as 6 months. Median rate of reaction per dose was 0.5% with transient oropharyngeal itching most common and no dosing symptoms requiring epinephrine.

Conclusion:

In this open-label, prospective study, peanut SLIT was safe and induced clinically significant desensitization in the majority of children lasting more than 17 weeks after discontinuation of therapy.

Capsule summary:

Peanut SLIT results in durable desensitization to >800 mg in the majority of peanut-allergic children. Peanut SLIT appears safe with <5% of doses causing side effects and most being transient mouth itch.

Introduction:

Food allergy continues to be a growing public health problem.^{1, 2} Much of the focus in food allergy research has been on peanut allergy due to its low rate of natural resolution and its propensity for more severe reactions.³ Approximately 1–2% of children are affected by peanut allergy and it remains one of the most common causes of anaphylaxis treated in emergency departments and the most common cause of fatal food allergic reactions.^{4, 5} The typical approach of strict allergen avoidance has been shown to greatly reduce the frequency of allergic reactions; however, over time most patients experience accidental ingestions with unpredictable and sometimes severe symptoms.⁶ Furthermore, strict allergen avoidance has led to the unintended consequence of a significant decrease in quality of life driven by factors such as anxiety⁷, social isolation⁸, restricted daily activities⁹, and financial burden.¹⁰ Immunotherapy has been the best studied approach to treatment with numerous positive studies of oral immunotherapy (OIT)^11–14 leading to the recent regulatory approval of the first product for peanut OIT. However, administration of OIT is still complicated by allergic adverse events, taste aversion, and frequent clinical appointments for observed dosing.

Sublingual immunotherapy (SLIT) for peanut allergy has shown promise in particular due to its relative ease of administration and favorable safety profile. We have previously shown successful desensitization, defined as an increase in reaction threshold to peanut, after 2 mg peanut SLIT in 1–11 year old children. Participants on peanut SLIT for 12 months safely tolerated 1710 mg of peanut compared to 85 mg for those on placebo¹⁵ and this increased reaction threshold was maintained after an extended 3–5 years of treatment.¹⁶ However, the degree of desensitization with peanut SLIT has varied across published studies^15–19 and within our own cohort there was variation among individual participants with some tolerating the maximum 5000 mg of peanut protein and others reacting at the lowest 250 mg dose on oral food challenge (OFC). Of the subset of 12 participants who passed the 5000 mg OFC without allergic symptoms, 10 participants again passed a 5000 mg OFC after stopping peanut SLIT for 2–4 weeks demonstrating durable desensitization for at least a limited time in these participants. However, because we assessed treatment avoidance only in participants who fully passed the end of treatment OFC, we could not assess whether lower degrees of desensitization could be maintained or estimate how long this desensitization might last off therapy.

To better describe the efficacy of peanut SLIT and address these limitations, we designed the current study of peanut SLIT with the key changes of increasing the peanut SLIT maintenance dose from 2 mg up to 4 mg and incorporating OFCs at baseline to allow for assessment of individual responses to treatment. In addition, we implemented a first-of-its-kind randomly assigned treatment avoidance period designed to assess the durability of desensitization in all participants with clinically significant treatment response up to 17 weeks off peanut SLIT.²⁰

Methods:

Study population

Participants between ages 1 and 11 years of age and of any sex, race, and ethnicity were enrolled. Enrollment began at Duke University Medical Center (Durham, NC) in 2011 and was completed at the University of North Carolina (UNC) (Chapel Hill, NC) after the research group moved in 2012. Peanut allergy was confirmed by: 1) a convincing history of peanut allergy defined as the onset of IgE-mediated allergic symptoms within 2 hours of a suspected ingestion of peanut; 2) positive peanut-specific IgE (Pn-sIgE) > 0.35 kU_A/L; and 3) reaction during 1000 mg peanut protein screening double-blind, placebo-controlled food challenge (DBPCFC). Select exclusion criteria included severe anaphylaxis after peanut exposure, severe asthma (2007 NHLBI steps 5 or 6)²¹, prior peanut interventional study participation, and prior eosinophilic gastrointestinal disease. Full inclusion and exclusion criteria are presented in supplemental table 1.

Study design

Participants meeting all inclusion and exclusion criteria were started on open-label peanut SLIT. Peanut SLIT was composed of peanut protein in glycerol-saline at a stock concentration of 5000 mcg/ml that was obtained from Greer Laboratories (Lenoir, NC). Dilutions of peanut SLIT were prepared by trained staff following Good Manufacturing Practice guidelines and aliquoted into 32.6 ml vials capped with a 50 μl actuator pump. SLIT dosing was administered once daily under the tongue and held for 2 minutes prior to swallowing as previously reported.¹⁵ Participants were instructed not to eat or drink for 15 minutes prior and 30 minutes after dosing. Participants were cautioned about dosing while febrile or during exercise but these were not restricted in the protocol. Several modifications were made to the dose escalation protocol from our prior report including escalation over a shorter 5-month period, incorporating weekly to biweekly at-home dose increases combined with monthly in-clinic observed doses, and increasing the daily maintenance dose to 4 mg of peanut protein (supplemental table 2). Upon achieving the maintenance dose, participants repeated this dose daily for a total treatment duration of 48 months.

Reaction thresholds to peanut were assessed by DBPCFC with each individual participant undergoing 3 total DBPCFCs: at baseline, after 48 months of peanut SLIT, and after the avoidance phase (supplemental figure 1). The per protocol (PP) population was defined as participants completing peanut SLIT dosing with evaluable baseline and 48-month DBPCFC. Reaction thresholds were reported as the successfully consumed dose (SCD) defined as the cumulative amount of peanut protein ingested prior to the DBPCFC dose that led to allergic symptoms and discontinuation of the DBPCFC.²²

For the avoidance phase, PP participants with an SCD of 300 mg or greater were randomly assigned to 1 to 17 weeks of peanut SLIT avoidance prior to returning for the final DBPCFC as previously described.²⁰ Continuation of strict peanut avoidance was emphasized during the avoidance phase. Block randomization was implemented to allocate even numbers of participants to 1–6, 7–12, and 13–17 week assignments with approximately 3 participants assigned to each avoidance week.²⁰ In cases where assigned and actual avoidance times differed due to scheduling conflicts, actual avoidance time was utilized for calculations. For analysis purposes, clinically significant desensitization was defined as an SCD of ≥800 mg peanut protein during DBPCFC after completion of peanut SLIT dosing.

DBPCFCs

The baseline 1000 mg DBPCFC was administered in 5 increasing doses as follows: 25, 50, 100, 250, 575 mg peanut protein. The 5000 mg DBPCFC at 48 months and after avoidance was designed after the Fibonacci series as previously described to allow for increased granularity at higher dose levels and administered in 6 increasing doses as follows: 100, 200, 500, 800, 1300, 2100 mg peanut protein.²⁰ Oat flour was used as a placebo and administered in identical increments by weight. The DBPCFC was discontinued and appropriate rescue medication was administered if objective and/or persistent subjective allergic symptoms were observed including but not limited to diffuse hives, severe nasal congestion, lip and tongue swelling, throat pain, coughing, moderate-to-severe abdominal pain, and vomiting.

Safety monitoring

DBPCFCs and observed SLIT dosing were monitored by a study nurse or physician in the clinical research unit. For daily home dosing, parents were instructed to monitor participants for 2 hours after dosing and document all symptoms in home diaries. Timing of symptoms relative to dosing and treatment of symptoms were also recorded. Dosing while febrile or actively ill was discouraged; however, no formal restrictions were made regarding specific times for dosing or dosing around exercise. Seventeen types of dosing symptoms were broadly grouped into local, skin, upper respiratory, lower respiratory, and abdominal categories for reporting purposes (supplemental table 3).

Immune mechanistic studies

Peanut skin prick testing

Peanut skin prick testing (Pn-SPT) was performed at baseline; after 12, 24, 36, and 48 months of peanut SLIT dosing; and after SLIT avoidance. Pn-SPT were performed with a GREER Pick (Greer Laboratories, Lenoir, NC) using a standard 1:20 dilution peanut extract and with positive and negative controls. Wheal size was calculated as the average of the longest diameter and the perpendicular midpoint diameter. Pn-SPT results were reported as the peanut wheal size minus the wheal size of the saline negative control.

Peanut-specific immunoglobulins

Blood for immune studies was collected at baseline; after 6, 12, 24, 36, 48 months of peanut SLIT; and after SLIT avoidance. Serum Pn-sIgE and peanut-specific IgG4 (Pn-sIgG4) levels were measured using the ImmunoCAP 100 (Thermo Scientific, Waltham, MA), as previously described.^{15, 23} Ratios of Pn-sIgG4 to Pn-sIgE were calculated using a conversion factor of 2.42 mcg/L = 1 kU/L for Pn-sIgE.

Peanut-stimulated basophil activation test

Peripheral blood was collected in sodium heparin tubes for basophil activation tests (BAT). Using whole blood in the presence of 2 ng/ml human IL-3 (Miltenyi Biotec, Gaithersburg, MD), the BAT was performed with 1000, 100, 10, and 1 ng/mL dilutions of crude peanut extract (CPE), polyclonal anti-IgE (1000 ng/mL, Bethyl Laboratories, Montgomery, TX), and media alone for 30 minutes. Cells were then stained for CD123, CD203c, and CD63. Basophils were identified as CD123+ CD203c+ double-positive events, with CD63 as the marker of activation. Samples were acquired on a CyAn Flow Cytometer (Beckman Coulter, Brea, CA) and data was analyzed using FlowJo^™ v10.8 software (BD Life Sciences, Ashland, Oregon).

Peanut-simulated T-cell cytokines

Peripheral blood mononuclear cells (PBMC) were isolated from heparinized blood by using Fico/Lite LymphoH density gradient sedimentation (Atlanta Biologicals, Lawrenceville, GA) and suspended in 10% autologous plasma and culture media (RPMI-1640 with 2 mmol/L L-glutamine, 25 mmol/L HEPES buffer with 100 IU/mL penicillin, and 100 mg/mL streptomycin; Mediatech, Manassas, VA). The PBMCs were plated in triplicate at a concentration of 0.5 million cells per well with CPE (200 mcg/mL), concanavalin A (40 mcg/ml), or media alone. Next, the PBMCs were incubated at 37°C in a 5% CO2 humidified atmosphere for 72 hours. Finally, supernatants were collected and stored at −80°C until analysis. Quantities of IL-4, IL-5, IL-13, IFN-gamma, TNF-alpha, IL-10 were measured by means of ELISA (R&D Systems, Minneapolis, MN). Cytokine levels in culture media controls were subtracted from CPE levels before reporting.

Statistical analysis

The primary objectives of this study were to describe the DBPCFC threshold after 48 months of SLIT and to describe the kinetics of the loss of desensitization after SLIT was stopped. As we analyzed the data, we realized that the statistical methods described in the protocol for these descriptive objectives were unwieldy and inconsistent with current methods of reporting the results of oral food challenges. We analyzed the oral food challenge results as follows. Paired T-tests were used to assess changes in DBPCFC between baseline and 48 months. For assessment of longitudinal changes from baseline through 48 months for Pn-SPT, Pn-sIgE, Pn-sIgG4, Pn-sIgG4/IgE ratio, BAT, and T-cell cytokines, a mixed effects model was used with Dunnett’s test for multiple comparisons. Analysis of the DBPCFC, Pn-SPT, peanut-specific immunoglobulins, BAT, and T-cell cytokines were performed on the PP population. All tests were two-sided with p<0.05 considered significant. To estimate time to loss of desensitization we used a parametric model of interval censored survival-time data that accommodated the fact that desensitization was assessed at varying time intervals, assuming a Weibull survival distribution using the stintreg command in STATA 17. Modeled survival curves by 48-month OFC threshold were created. All analyses were done using GraphPad Prism 9 and STATA 17.

Ethics

The study was registered on clinicaltrials.gov (NCT01373242) and conducted under a US Food and Drug Administration investigational new drug application. The protocol and consent forms were approved by the Duke University and University of North Carolina (UNC) institutional review boards. Written informed consent was obtained from parents/guardians.

Results:

Study participants

Fifty-four participants were enrolled in the study and began peanut SLIT dosing. Baseline characteristics of all enrolled participants are shown in Table 1. The mean age of participants was 7.1 years (SD = 2.6, range 2.3 – 11.9 years) with a majority being male sex, white race and all being non-Hispanic ethnicity. The population was highly atopic with 70.4%, 59.3% and 40.7% reporting atopic dermatitis, allergic rhinitis, and asthma respectively. Additional food allergies were also reported by 27.8% of participants. The mean baseline Pn-sIgE was 212.3 kU_A/L (SD = 336.5) and mean Pn-SPT wheal was 16.6 mm (SD = 7.2). Mean SCD during baseline DBPCFC was 66.2 mg of peanut protein (SD = 124, range <25 – 425 mg). Baseline DBPCFC results are described in more detail in supplemental table 4.

Table 1:

Baseline characteristics of the 54 enrolled participants undergoing the baseline DBPCFC and receiving at least 1 dose of peanut SLIT.

	Peanut SLIT
n	54
Age, mean (range)	7.1 years (SD = 2.6)
Sex, n (%)
Male	34 (63.0%)
Female	20 (37.0%)
Race, n (%)
White	49 (90.7%)
Asian	4 (7.4%)
Mixed race	1 (1.9%)
Comorbid atopic diseases, n (%)
Asthma	22 (40.7%)
Atopic dermatitis	38 (70.4%)
Allergic rhinitis	32 (59.3%)
Other food allergies	15 (27.8%)
Baseline Pn-sIgE, median, mean	84.3 kUA/L, 212.3 kUA/L (SD = 336.5)
Baseline Pn-sIgG4, median, mean	0.38 mg/L, 1.1 mg/L (SD = 2.9)
Baseline Pn-SPT, median, mean	16 mm, 16.6 mm (SD = 7.2)
Baseline DBPCFC successfully consumed dose, median, mean	12.5 mg, 66.2 mg (SD = 124.0)

Participant flow

Of the 54 enrolled participants, 7 participants withdrew during peanut SLIT dosing and 47 completed peanut SLIT dosing and the 48-month DBPCFC comprising the PP population. Three PP participants did not qualify for the avoidance DBPCFC due to a 48-month SCD of less than 300 mg. Seven PP participants declined to participate in the avoidance phase after completion of the 48-month DBPCFC. In total, 37 participants completed the avoidance DBPCFC (Figure 1).

Figure 1:

Participant flow diagram

Desensitization outcomes

DBPCFC

The mean SCD during the 48-month DBPCFC for the PP population increased significantly from a baseline mean SCD of 48.4 mg (SD = 93.2) to a 48-month mean SCD of 2723 mg (SD = 1904) peanut protein (p<0.0001) (Figure 2). Seventeen PP participants (36%) completed the 48-month DBPCFC without symptoms and were reported as an SCD of 5000 mg. Thirty-three PP participants (70.2%) achieved an SCD of 800 mg or greater and were considered to have clinically significant desensitization.

Figure 2:

Mean successfully consumed dose (SCD) during DBPCFC for the PP group at baseline and after 48 months of peanut SLIT. Colors represent the different levels of SCD achieved during the 48 month DBPCFC. ***p<0.0001.

Peanut skin prick testing and peanut-specific immunoglobulins

Pn-SPT for the PP population was significantly decreased by 12 months of treatment and remained significantly decreased over the course of treatment from a mean wheal size of 16.5 mm (SD = 7.0) at baseline to 9.1 mm (SD = 4.9) after 48 months (p<0.0001) (Figure 3). Peanut-specific immunoglobulin levels also changed significantly after peanut SLIT (Figure 3). Pn-sIgE increased significantly from baseline after 6 months, then returned towards baseline by 12 months. Pn-sIgE was significantly decreased by 24 months and through the duration of treatment from a mean level of 213.0 kU_A/L (SD = 351.2) at baseline down to 60.7 kU_A/L (SD = 162.7) after 48 months (p<0.0001). Pn-sIgG4 was significantly increased from baseline at 6 months and remained significantly increased over the course of treatment from a mean level of 0.8 mg/L (SD = 1.4) at baseline up to 20.6 mg/L (SD = 47.9) after 48 months (p<0.0001). Pn-sIgG4/Pn-sIgE ratio was increased from baseline at 6 months but did not reach statistical significance until 12 months after which the ratio remained increased over the course of treatment from a mean level of 6.7 (SD = 10.7) at baseline to 1176.0 (SD = 2823) after 48 months (p=0.0012).

Figure 3:

Pn-SPT, Pn-sIgE, Pn-sIgG4 and Pn-sIgG4/IgE ratio for the PP group at baseline and during peanut SLIT. Mean values at all time points were compared to baseline. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001.

Peanut-stimulated basophil activation test

Mean percentage of CD63+ basophils decreased from baseline during BAT at the 10 ng/ml and 1 ng/ml dilution starting at 6 months and lasting through the course of treatment. Decreases at the 10 ng/ml CPE dilution were significant across all time points while decreases at the 1 ng/ml CPE dilution were significant at the 24 and 48-month time points. Overall, mean percentage of CD63+ basophils at the 10 ng/ml dilution decreased from 34.0% (SD = 30.1) at baseline to 18.8% (SD = 22.9) after 48 months (p=0.0012) and at the 1 ng/ml dilution from 19.7% (SD = 24.8) at baseline to 9.1% (SD = 17.8) after 48 months (p=0.0178) (Figure 4). There was an unexpected significant increase in basophil activation at 12 and 24 months (p<0.05) at the 1000 ng/ml CPE dilution that was no longer present after 48 months while changes at the 100 ng/ml CPE dilution were not significant.

Figure 4:

Basophil activation testing stimulated with 1000, 100, 10 and 1 ng/ml CPE for the PP group at baseline and during peanut SLIT. Mean values at all time points were compared to baseline. *p<0.05, **p<0.01.

Peanut-stimulated T-cell cytokines

T_H2 cytokine levels after peanut stimulation were decreased significantly from baseline after 12 months and remained decreased after completion of peanut SLIT (Figure 5). IL-4 decreased from a mean level of 2.2 pg/ml (SD = 3.2) at baseline to 0.6 pg/ml (SD = 0.6) after 48 months (p=0.0012). IL-5 decreased from a mean level of 778.3 pg/ml (SD = 949.6) at baseline to 141.1 pg/ml (SD = 144.6) after 48 months (p=0.0002). IL-13 decreased from a mean level of 40.9 pg/ml (SD = 46.9) at baseline to 9.6 pg/ml (SD = 11.4) after 48 months (p<0.0001). IFN-gamma levels were significantly decreased only after 48 months, however TNF-alpha was unchanged after peanut SLIT. IL-10 levels were decreased from baseline after 12 and 48 months of peanut SLIT (supplemental figure 2)

Figure 5:

Peanut stimulated IL-4, IL-5 and IL-13 levels for the PP group at baseline and during peanut SLIT. Mean values at all time points were compared to baseline. **p<0.01, ***p<0.001, ****p<0.0001

Avoidance outcomes

In total, 37 participants completed the avoidance phase. Figure 6 shows the Kaplan-Meier survival curve demonstrating time to loss of clinically significant desensitization (SCD <800 mg peanut protein during the avoidance DBPCFC). The estimated median time to loss of desensitization was 22 weeks (IQR: 10->100 weeks). When considering an alternative threshold for clinically significant desensitization of 300 mg, none of the 37 participants undergoing the avoidance DBPCFC reacted below this threshold during the 17-week avoidance phase. If we alternatively considered loss of desensitization as losing one step in the DBPCFC threshold, 49% lost desensitization within the 17-week follow-up time. If we employed interval censored survival analysis, we estimated a median time to loss of one step during the DBPCFC of 12 weeks (IQR: 11–12 weeks).

Figure 6:

Post-desensitization Kaplan-Meier survival analysis modeling the proportion of participants estimated to tolerate greater than 800 mg peanut protein during DBPCFC across increasing periods of peanut avoidance.

Dosing compliance and safety

Of 81,031 possible dosing days, 97.6% of peanut SLIT doses were reported as taken. Symptoms were reported after 4.0% of home administered doses with a median rate of reaction per person per dose of 0.49% (Table 2). Seven participants accounted for 2525 of the 3203 (83.3%) reported dosing symptoms in the study, one of whom withdrew from the study. The most common dosing symptom category reported was local (oropharyngeal itching, lip swelling) occurring with 3.7% of doses. Skin symptoms and abdominal symptoms (belly pain, vomiting, diarrhea) were each reported with 0.1% of doses. Antihistamines were administered for 143 symptom episodes (0.14% of doses taken) and no epinephrine was administered for any SLIT dosing symptoms.

Table 2:

Dosing compliance and safety for the 54 enrolled participants.

	Peanut SLIT (n = 54)
Total dosing days	81,031
Missed doses	2,019 (2.49%)
Total doses taken	79,012 (97.51%)
Dosing symptoms, n (% doses taken)	3,203 (4.05%)
Local, n (% doses taken)
Oropharyngeal pruritus	2,841 (3.60%)
Lip swelling	50 (0.06%)
Skin, n (% doses taken)	113 (0.14%)
Upper respiratory tract, n (% doses taken)	7 (0.01%)
Lower respiratory tract, n (% doses taken)	28 (0.03%)
Abdominal, n (% doses taken)
Belly pain	89 (0.11%)
Vomiting	18 (0.02%)
Diarrhea	5 (0.01%)
Treatment administered, n (% doses taken)
Antihistamine	143 (0.18%)
Epinephrine	0

Three participants withdrew during peanut SLIT dosing due to abdominal side effects. One participant experienced recurrent belly pain and vomiting and discontinued peanut SLIT. The participant was evaluated by a gastroenterologist and ultimately improved on proton pump inhibitor therapy. A second participant with recurrent belly pain was diagnosed by their gastroenterologist with severe constipation and withdrew to focus on their constipation treatment. The third participant developed significant food aversion which improved with discontinuation of peanut SLIT. No participants were diagnosed with eosinophilic esophagitis (EoE) during the study.

Discussion:

In our study of a 4 mg peanut SLIT in 1–11 year old peanut-allergic children, we demonstrate the strongest desensitization after SLIT to date with a mean SCD of 2723 mg for the cohort after 48 months of treatment. One-third of PP participants passed the 5000 mg DBPCFC without dose-limiting symptoms despite a treatment dose of only 4 mg. When considering the more recent concept of “bite-proof” protection, described as being unlikely to have an allergic reaction after a bite of a peanut-containing or peanut-contaminated product²⁴, peanut SLIT was highly effective with 70.2% of participants achieving an SCD of at least 800 mg.^{25, 26}

Baseline biomarkers indicated that the cohort were unlikely to naturally outgrow their peanut allergy with a baseline peanut SPT of 16.6 mm and ps-IgE of 212.3 kU_A/L. Immediate effector cell response, represented by SPT and basophil activation tests, was decreased after peanut SLIT changes while changes in pn-sIgE, pn-sIgG4 and pn-sIgG4/IgE ratio represented alterations of the humoral immune response. In addition, secretion of T_H2 cytokines (IL-4, IL-5 and IL-13), IFN-gamma, as well as IL-10 were significantly decreased after peanut SLIT. Taken together, we demonstrate that peanut SLIT broadly alters the allergic immune response across mast cells and basophils, B-cells, and T-cells.

The changes in B and T-cells in particular suggest the possibility of a more durable desensitization effect which was supported by the findings in our novel avoidance phase of the study. In participants achieving clinically significant desensitization with an SCD of at least 800 mg, our survival analysis demonstrated an estimated median time to loss of desensitization of 22 weeks to fall below this threshold. If we instead used 300 mg to represent clinically significant desensitization as has been suggested by Baumert, et al in simulation studies of real-life peanut exposure²⁵, the median time to loss of desensitization was estimated to be well beyond 17 weeks as no participants in the study fell below 300 mg within the 17-week assessment period. With the goal of peanut allergy treatment increasingly focused on protection from accidental ingestions of peanut²⁷, our data for peanut SLIT supports a treatment response in the majority of patients that importantly appears to be able to withstand lapses in therapy of up to several weeks.

Two presumed benefits of peanut SLIT when compared to other forms of immunotherapy are its ease of administration and the safety and tolerability of the approach. Despite a doubling of the maintenance dose from our prior reports^{15, 16}, we demonstrated strong compliance with over 97% of doses taken over the 4 year treatment period. Dosing side effects were only reported with 4% of doses and in agreement with prior reports of SLIT, the majority of these involved transient oropharyngeal itching. Encouragingly, allowing self-administration and home dose escalation was relatively safe as no dosing reactions required treatment with epinephrine.

EoE is a known concern with peanut OIT²⁸ and is an integral part of the risk discussion when deciding to initiate OIT. There have been rare case reports of EoE with SLIT for environmental allergies^29–32; however, to date there have been no reports of EoE with food SLIT. Three participants withdrew from the study with abdominal symptoms, one that improved on PPI therapy and another with food aversion that improved with discontinuation of peanut SLIT. While it was reassuring that EoE was not diagnosed in any participants, it will be important to continue to monitor the development of GI symptoms and their sequelae in future studies of peanut SLIT.

Although the study was not designed to compare the overall side effects and safety of peanut SLIT to that of peanut OIT, from published studies, the side effects after peanut SLIT appear to be significantly less. When considering that tolerance does not appear likely with food immunotherapy and that treatment is likely to be required long-term if not indefinitely, these results demonstrating the feasibility and safety of keeping up the daily peanut SLIT regimen for multiple years take on particular importance.

There are a few limitations to the study. First, there was no blinding of the treatment or avoidance phases of the study. Up to 20% of patients might be expected to spontaneously outgrow peanut allergy, however with a median participant age of 7 years at the start of treatment and a mean Pn-sIgE of 212.3 kU_A/L, natural resolution of peanut allergy was not expected to be common for the cohort. Even with a conservative estimate of 20% natural resolution, our finding of 70% of participants achieving an SCD of at least 800 mg and 36% passing the DBPCFC would support a treatment effect with peanut SLIT. Exclusion of patients with past anaphylaxis involving hypoxia, hypotension or neurological compromise and those with NHLBI step 5 and 6 asthma limits the generalizability of our results to patients who have experienced the most severe forms of anaphylaxis. Advance knowledge of the avoidance assignment might be expected to affect dosing compliance. To mitigate this effect, the assignment was not revealed until 2 weeks prior to the end of SLIT treatment. While there was concern for a disproportionate withdrawal of participants with longer avoidance assignments, 15 of 17 participants assigned between 12 to 17 weeks completed avoidance and the subsequent DBPCFC. Finally, while median time to loss of desensitization was able to be estimated during the avoidance phase, the study was not powered to calculate a week-to-week decay or half-life of the desensitization effect.

In conclusion, in our study of peanut SLIT in 1 to 11 year old children treated for 48 months, we show improved desensitization with peanut SLIT compared to our prior studies and importantly with no meaningful increase in dosing reactions. Our updated dosing protocol with home updosing steps should allow for improved access to treatment for a broader range of peanut-allergic patients. Finally, our novel finding of maintained protection against accidental ingestions of peanut even after weeks without therapy further supports the real-world feasibility of peanut SLIT by providing reassurance in the case of missed doses or other gaps in treatment. Taken together, these data suggest a balance of efficacy and safety that could make peanut SLIT a promising option for the treatment for peanut allergy.

Key Messages:

• 4 mg peanut SLIT results in clinically significant desensitization that persists for several months after discontinuation of therapy

• The rate of side effects were low, mostly consisted of mouth itch and did not require epinephrine.

Abbreviations:

BAT

basophil activation test

CPE

crude peanut extract

DBPCFC

double blind, placebo-controlled food challenge

EPIT

epicutaneous immunotherapy

IgE

immunoglobulin E

IgG4

immunoglobulin G4

NHLBI

National Heart, Lung and Blood Institute

NIAID

National Institute of Allergy and Infectious Diseases

NIH

National Institutes of Health

OFC

oral food challenge

OIT

oral immunotherapy

PBMC

peripheral blood mononuclear cells

Pn-sIgE

peanut-specific IgE

Pn-sIgG4

peanut-specific IgG4

Pn-SPT

peanut skin prick test

PP

per protocol

SCD

successfully consumed dose

SLIT

sublingual immunotherapy

SPT

skin prick test

SU

sustained unresponsiveness

UNC

University of North Carolina