Onset of eosinophilic esophagitis during a clinical trial program of oral immunotherapy for peanut allergy

Allergen immunotherapy and eosinophilic esophagitis: friends or foes?

PURPOSE OF REVIEW

The connection between eosinophilic esophagitis (EoE) and food and airborne allergens is complex. Exposure to allergens (mainly food) is often the trigger for EoE flares. The development of EoE has been described as a side effect of allergen immunotherapy, especially oral immunotherapy (OIT, with food allergens), while isolated cases of EoE have been reported during sublingual immunotherapy (SLIT, with extracts of aeroallergens).

RECENT FINDINGS

EoE is currently recognized as a common side effect of OIT, while a solid correlation between SLIT and EoE is missing. Animal models have been developed to study the pathophysiological link between sensitization to aeroallergens and the induction of EoE and will probably provide an interpretation of why there are cases of EoE developed during SLIT. Recent findings in animal models suggest a genetic connection to EoE development after sensitization and re-exposure to airborne allergens. Subcutaneous allergen immunotherapy does not have a causative effect on EoE; on the contrary, a beneficial effect on EoE has been reported. Moreover, epicutaneous immunotherapy with a vector containing milk has also been used to treat children with milk-induced EoE.

SUMMARY

Discovering the immune links between allergens and EoE will further guide the proper use of allergen immunotherapy and help define future strategies for the management of EoE.

The Relationship Between Eosinophilic Esophagitis and Immunotherapy

Immunotherapy is a treatment approach based on the principle of incremental allergen exposure to achieve desensitization. Recently, oral immunotherapy has been introduced as a treatment of IgE-mediated food allergy. Some patients receiving oral immunotherapy for food allergy may develop eosinophilic esophagitis. Here, we summarize the literature examining this association, its treatment, and outcomes and discuss possible explanations for this clinical phenomenon. We further identify potential associations with aeroallergen sensitivity and other forms of immunotherapy including subcutaneous immunotherapy and sublingual immunotherapy. Finally, we discuss management of immunotherapy-induced eosinophilic esophagitis. Epicutaneous immunotherapy is highlighted as an area of therapeutic investigation.

Practical issues of oral immunotherapy for egg or milk allergy

Oral immunotherapy (OIT) has been recommended to reduce parental burden related to strict allergen avoidance and induce desensitization and immune tolerance for patients with long-lasting allergies to hen's eggs (HE) or cow's milk (CM). OIT should be monitored by pediatric allergists specializing in OIT and oral food challenge tests to manage allergic reactions. Although a previous history of anaphylaxis or multiple food allergies is not a contraindication to OIT, it is contraindicated if the patient has uncontrolled asthma, a malignancy, active systemic autoimmune disorders, or diseases requiring treatment with beta-blockers. A variety of OIT protocols have been de veloped to ensure better outcomes and safe up-dosing, including adjunctive therapies with biologics. This review provides insight into the practical issues of various immunotherapy options for children with HE or CM allergies.

Proton pump inhibitors in eosinophilic esophagitis (EoE) related to oral immunotherapy: is it as effective as in other EoE?

Oral immunotherapy (OIT) may induce eosinophilic esophagitis (EoE). Proton pump inhibitors (PPIs) are an effective treatment for EoE. However, the effect of PPI treatment is not well established in patients with EoE induced by OIT. Our primary aim was to compare the clinical, endoscopic, and histological response rates to PPIs in children with EoE induced by OIT (EoE+OIT) versus EoE patients without OIT (EoE-OIT). The secondary aims are to describe the clinical and histological features of EoE+OIT. Demographic, clinical, endoscopic, and histological findings of patients with EoE in the gastroenterology clinic at Shamir Medical Center between March 2015 and December 2022 were collected. Comparisons were performed between EoE+OIT and EoE-OIT patients. The study included 42 children (74% male, mean age 11.2), of whom 31 had EoE-OIT and 11 had EoE+OIT. There were no significant differences between groups regarding sex, comorbidities, symptoms, or endoscopic and histological characteristics at diagnosis. All 42 children were treated with PPIs after diagnosis with or without diet changes. The rates of any clinical response were 83.9% and 90.1% in the EoE-OIT group and EoE+OIT group, respectively (p = 1.0). The rate of any endoscopic response was 74.2% for EoE-OIT and 81.8% for EoE+OIT (p = 0.54). Histologically, PPIs were even more effective in the EoE+OIT group, where only 18.2% had no histological response at all compared to 51.6% in the EoE-OIT group (p = 0.1).

CONCLUSION

PPI treatment is as effective in EoE with OIT as it is in EoE due to other etiologies.

WHAT IS KNOWN

• Proton pump inhibitor (PPI) treatment is effective for achieving clinical response and histologic remission in some patients with eosinophilic esophagitis (EoE). • EoE has also been reported to be triggered by oral immunotherapy (OIT).

WHAT IS NEW

• PPI treatment in EoE with OIT is as effective as treatment for EoE due to other etiologies.

Eosinophil-Associated Gastrointestinal Manifestations During OIT

Gastrointestinal adverse events are common during oral immunotherapy (OIT) for food allergy and range from immediate IgE-mediated reactions to non-anaphylactic clinical presentations. This review aims to summarize recent findings on non-anaphylactic eosinophil-associated gastrointestinal adverse events during OIT. Two clinical presentations of non-anaphylactic eosinophil-associated gastrointestinal adverse events during OIT are identified, each with a different paradigm for treatment, and distinguished by their time of onset. In the first clinical entity, characterized by its onset early in the course of treatment, patients present with abdominal pain, nausea, and/or vomiting. The symptoms become evident typically within weeks to months of starting OIT. These symptoms, however, are not temporally related to the time of dose administration, as in the case of immediate IgE-mediated anaphylactic reactions. While esophageal biopsies, when performed, can demonstrate eosinophilic esophagitis (EoE), baseline esophageal eosinophilia has also been observed in food allergic patients prior to OIT. A potential non-invasive biomarker, the peripheral absolute eosinophil count (AEC), often rises during these reactions and subsides after dose reduction and subsequent resolution of symptoms. OIT can usually then be resumed, albeit at a slower pace, without a recurrence of symptoms. Risk factors for development of symptoms early during OIT include a high starting dose and a baseline AEC of greater than 600. The second, and much less frequently encountered, non-anaphylactic gastrointestinal adverse event related to OIT, presents months to years after initiating OIT. In this latter group, patients present with the classical clinical symptoms and endoscopic findings of EoE. In contrast to the acute onset group, peripheral eosinophilia is usually not observed in these cases. This OIT-associated EoE has shown good response to standard EoE treatment approaches of proton pump inhibitors or swallowed steroids. Most patients with eosinophil-associated adverse reactions are able to continue OIT and remain desensitized. Treatment approaches depend on the specific subtype of these reactions and relate to the stages of OIT treatment.

Ethical Implications of Continuing Oral Immunotherapy After the Development of Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is a chronic allergic inflammatory disease requiring maintenance therapy. Traditionally, EoE has been a contraindication to oral immunotherapy (OIT) and a rationale for discontinuing treatment because OIT may induce EoE. Most, but not all patients with OIT-induced EoE experience symptom resolution and histologic remission after discontinuing OIT. Recent studies report OIT continuation even after EoE onset, despite the previously accepted standard of care. This creates clinical as well as ethical challenges for allergists treating these patients. Considering the published literature on EoE and OIT and the primary medical ethics principles of beneficence, nonmaleficence, autonomy, and justice, we discuss the ethical implications of pursuing desensitization despite the potential complications associated with EoE. When ethical principles are in opposition, shared decision-making should be employed to determine whether OIT should be continued after an EoE diagnosis. This article highlights the ethical dilemmas allergists face when determining whether patients with a diagnosis of EoE should continue OIT.

Long-term safety and immunologic outcomes of daily oral immunotherapy for peanut allergy

Background

Oral immunotherapy containing peanut (Arachis hypogaea) allergen powder-dnfp (PTAH) (Palforzia [Aimmune Therapeutics, Brisbane, Calif]) for 9 to 12 months resulted in higher tolerated amounts of peanut protein in PTAH-treated individuals aged 4 to 17 years with peanut allergy than in placebo-treated participants.

Objective

We aimed to describe additional long-term pooled safety data and changes in peanut sensitization markers from baseline through approximately 5 years of treatment.

Methods

The results from 6 clinical trials of PTAH (3 controlled and 3 open-label extension studies [N = 1227]) were pooled, and analysis of safety outcomes and immunologic data was performed. The PTAH doses were administered sequentially as follows: initial dose escalation (dose increased to 6 mg over 2 days), updosing (dose increased every 2 weeks to 300 mg for a minimum of 6 months), and maintenance dosing (300 mg per day).

Results

There was a trend toward decreased adverse events (AEs) at years 1 and 2 that was maintained up to 5 years, with 94% of patients experiencing mild or moderate AEs and only 13% discontinuing PTAH use because of AEs overall. Gastrointestinal symptoms were the most commonly reported treatment-related AEs. A downward trend in systemic allergic reactions was also reported. PTAH treatment resulted in reduced levels of peanut-specific IgE after the first year and increased levels of peanut-specific IgG4, with a lowered peanut-specific IgE:IgG4 ratio. A reduction in median peanut skin prick test wheal diameter was observed (11.50 mm at baseline vs 5.75 mm at year 5).

Conclusion

Long-term immunomodulation without any new safety signals was reported with PTAH immunotherapy in the largest safety data set and longest treatment duration for oral immunotherapy published to date.

Peanut (Arachis hypogaea) allergen powder-dnfp for the mitigation of allergic reactions to peanuts in children and adolescents

INTRODUCTION

Peanut allergy can result in severe, sometimes fatal hypersensitivity reactions that place a considerable burden on the lives of patients. This article reviews the first approved immunotherapy for the mitigation of allergic reactions following accidental peanut exposure, peanut (Arachis hypogaea) allergen powder-dnfp (PTAH; Palforzia®, Aimmune Therapeutics).

AREAS COVERED

This article highlights the unmet need for patients with peanut allergy, describes the therapeutic landscape, and reviews the development of and clinical data for PTAH.

EXPERT OPINION

PTAH offers a standardized preparation of peanut allergen, with a tolerability and efficacy profile clearly defined through its robust clinical development and trial program. In children 4-17 years old, PTAH provides a standardized, approved product that many clinicians sought prior to initiating oral immunotherapy. PTAH reduced the likelihood of more severe reactions following exposure to peanut protein; although peanut avoidance remains essential, PTAH will enable more individuals with peanut allergy to participate in activities of daily life with less anxiety.

How We Manage Gastrointestinal Symptoms During Oral Immunotherapy Through a Shared Decision-Making Process-A Practical Guide for the Community Practitioner

Allergists addressing gastrointestinal (GI) symptoms during oral immunotherapy (OIT) may be biased toward diagnoses related to OIT; however, non-OIT causes may occur. Although there is currently a lack of robust data for evidence-based treatment recommendations, we provide 3 real-world illustrative cases along with a proposed management algorithm for GI symptoms encountered during OIT. This algorithm was developed because of a significant clinical need, given the number of new-to-OIT providers that include practicing allergists, trainees transitioning into practice, and allied health care providers who manage GI symptoms in OIT patients. We developed the algorithm based on the opinions of community and academic allergy clinics across Canada with significant clinical experience offering infant, preschool, and school-aged OIT patients, with gastroenterologist input. Further research is needed to fill the knowledge gaps in the management of GI symptoms during OIT before formal recommendations can be suggested.

Considerations for a shared decision-making conversation when initiating food oral immunotherapy

Oral immunotherapy (OIT) is an office-based procedure that offers potential treatment of immunoglobulin E mediated food allergy. OIT has multiple benefits, e.g., the ability to desensitize the individual with food allergy, which shifts the eliciting dose threshold required in that individual to trigger an allergic reaction, and also potentially to decrease the severity of any resulting reactions. However, OIT is not a cure and has distinct risks, including the risk of allergic reactions (including anaphylaxis) from the therapy itself, the potential risk of developing eosinophilic esophagitis (or similar clinical symptoms without a formal biopsy), and logistical issues in coordinating when to give the daily dose, and there are still uncertain intermediate-to-long-term outcomes with regard to OIT. The decision to start OIT is complex and potentially nuanced. Shared decision-making is a process that allows the patient and family and the clinician to undergo a mutual discussion of the risks, benefits, alternatives, and other considerations with regard to a medical decision (such as starting OIT) whereby there is an exchange of information that allows the patient and family to formally clarify and express their values and preferences with regard to facets of the decision in this particular context. The goal is for the patient to be able to make a fully informed decision that is reflective of his or her goals, values, preferences, and desires. This article outlined some of the key considerations to discuss with parents and patients before enrolling in an OIT program with regard to the risks and benefits, to assist in engaging in shared decision-making and obtaining informed consent.

Peanut oral immunotherapy – current trends in clinical trials

Immunotherapy for allergy has been practised for over 100 years. Low-dose repeated exposure to specific allergen extracts over several months to years can successfully induce clinical tolerance in patients with allergy to insect venoms, pollen, house dust mite and domestic animals. Different regimens and routes for immunotherapy include subcutaneous, sublingual, oral and intralymphatic. Food allergies have been difficult to treat in this way due to high anaphylactic potential and only recently the first immunotherapy for peanut allergy has received regulatory approval. Several clinical trials have indicated high efficacy in desensitisation of peanut-allergic individuals using oral immunotherapy, which allows for safer administration of relatively high allergen concentrations. Still, the risk of adverse events including serious allergic reactions and high anxiety levels for patients remains, demonstrating the need for further optimisation of treatment protocols. Here we discuss the design and outcomes of recent clinical trials with traditional oral immunotherapy, and consider alternative protocols and formulations for safer and more effective oral treatment strategies for peanut allergy.

Type 2 Inflammation in Eosinophilic Esophagitis: From Pathophysiology to Therapeutic Targets

Eosinophilic esophagitis (EoE) is a chronic immune-mediated disease of the esophagus characterized clinically by symptoms related to esophageal dysfunction and histologically by eosinophil-predominant inflammation, whose incidence is rising. It significantly affects patients’ quality of life and, if left untreated, results in fibrotic complications. Although broad consensus has been achieved on first-line therapy, a subset of patients remains non-responder to standard therapy. The pathogenesis of EoE is multifactorial and results from the complex, still mostly undefined, interaction between genetics and intrinsic factors, environment, and antigenic stimuli. A deep understanding of the pathophysiology of this disease is pivotal for the development of new therapies. This review provides a comprehensive description of the pathophysiology of EoE, starting from major pathogenic mechanisms (genetics, type 2 inflammation, epithelial barrier dysfunction, gastroesophageal reflux, allergens, infections and microbiota) and subsequently focusing on the single protagonists of type 2 inflammation (involved cells, cytokines, soluble effectors, surface proteins and transcription factors) that could represent present and future therapeutic targets, while summarizing previous therapeutic approaches in literature.