Controversies in Allergy: The Potential Role of Biologics as First-Line Therapy in Eosinophilic Disorders

Idiopathic hypereosinophilic syndromes and rare dysimmune conditions associated with hyper-eosinophilia in practice: An innovative multidisciplinary approach

Hypereosinophilic syndromes (HES) represent a group of rare dis-immune conditions characterized by blood hyper-eosinophilia and eosinophilic related burden. Especially the idiopathic subtype (I-HES) is particularly difficult to diagnose because of its heterogeneous clinical presentation, the lack of specific findings on physical exam, lab tools, and imaging informative enough to unequivocally confirm the diagnosis and the overlap with other entities, including eosinophilic organ-diseases or systemic dis-immune conditions other than I-HES (from atopy to eosinophilic granulomatosis with polyangiitis [EGPA], the last often extremely difficult to distinguish from HES). Taken together, all the features mentioned above account for an extremely difficult early recognition HES and on-time referral to a specialized centre. The referral itself is challenging due to a not univocal specialist identification, because of the variability of physicians managing HES in different settings (including allergist/clinical immunologist, haematologist, internal medicine doctors, pulmonologist, rheumatologist). Furthermore, the approach in terms of personalized treatment identification and follow-up plan (timing, organ assessment), is poorly standardized. Further translational and clinical research is needed to address the mentioned unmet needs, but on practical grounds increasing the overall clinicians' awareness on HES and implementing healthcare pathways for HES patients represent a roadmap that every clinician might try to realize in his specific setting. The present review aims at providing an overview about the current challenges and unmet needs in the practical approach to HES and rare hypereosinophilic allergo-immunological diseases, including a proposal for an innovative multidisciplinary organizational model.

Dupilumab for Eosinophilic Esophagitis in Patients 1 to 11 Years of Age

BACKGROUND

Dupilumab is a human monoclonal antibody that blocks interleukin-4 and interleukin-13 pathways and has shown efficacy in five different atopic diseases marked by type 2 inflammation, including eosinophilic esophagitis in adults and adolescents.

METHODS

In this phase 3 trial, we randomly assigned, in a 2:2:1:1 ratio, patients 1 to 11 years of age with active eosinophilic esophagitis who had had no response to proton-pump inhibitors to 16 weeks of a higher-exposure or lower-exposure subcutaneous dupilumab regimen or to placebo (two groups) (Part A). At the end of Part A, eligible patients in each dupilumab group continued the same regimen and those in the placebo groups were assigned to higher-exposure or lower-exposure dupilumab for 36 weeks (Part B). At each level of exposure, dupilumab was administered in one of four doses tiered according to baseline body weight. The primary end point was histologic remission (peak esophageal intraepithelial eosinophil count, ≤6 per high-power field) at week 16. Key secondary end points were tested hierarchically.

RESULTS

In Part A, histologic remission occurred in 25 of the 37 patients (68%) in the higher-exposure group, in 18 of the 31 patients (58%) in the lower-exposure group, and in 1 of the 34 patients (3%) in the placebo group (difference between the higher-exposure regimen and placebo, 65 percentage points [95% confidence interval {CI}, 48 to 81; P<0.001]; difference between the lower-exposure regimen and placebo, 55 percentage points [95% CI, 37 to 73; P<0.001]). The higher-exposure dupilumab regimen led to significant improvements in histologic, endoscopic, and transcriptomic measures as compared with placebo. The improvements in histologic, endoscopic, and transcriptomic measures between baseline and week 52 in all the patients were generally similar to the improvements between baseline and week 16 in the patients who received dupilumab in Part A. In Part A, the incidence of coronavirus disease 2019, nausea, injection-site pain, and headache was at least 10 percentage points higher among the patients who received dupilumab (at either dose) than among those who received placebo. Serious adverse events were reported in 3 patients who received dupilumab during Part A and in 6 patients overall during Part B.

CONCLUSIONS

Dupilumab resulted in histologic remission in a significantly higher percentage of children with eosinophilic esophagitis than placebo. The higher-exposure dupilumab regimen also led to improvements in measures of key secondary end points as compared with placebo. (Funded by Sanofi and Regeneron Pharmaceuticals; EoE KIDS ClinicalTrials.gov number, NCT04394351.).

One-food versus six-food elimination diet therapy for the treatment of eosinophilic oesophagitis: a multicentre, randomised, open-label trial

BACKGROUND

Empirical elimination diets are effective for achieving histological remission in eosinophilic oesophagitis, but randomised trials comparing diet therapies are lacking. We aimed to compare a six-food elimination diet (6FED) with a one-food elimination diet (1FED) for the treatment of adults with eosinophilic oesophagitis.

METHODS

We conducted a multicentre, randomised, open-label trial across ten sites of the Consortium of Eosinophilic Gastrointestinal Disease Researchers in the USA. Adults aged 18-60 years with active, symptomatic eosinophilic oesophagitis were centrally randomly allocated (1:1; block size of four) to 1FED (animal milk) or 6FED (animal milk, wheat, egg, soy, fish and shellfish, and peanut and tree nuts) for 6 weeks. Randomisation was stratified by age, enrolling site, and gender. The primary endpoint was the proportion of patients with histological remission (peak oesophageal count <15 eosinophils per high-power field [eos/hpf]). Key secondary endpoints were the proportions with complete histological remission (peak count ≤1 eos/hpf) and partial remission (peak counts ≤10 and ≤6 eos/hpf) and changes from baseline in peak eosinophil count and scores on the Eosinophilic Esophagitis Histology Scoring System (EoEHSS), Eosinophilic Esophagitis Endoscopic Reference Score (EREFS), Eosinophilic Esophagitis Activity Index (EEsAI), and quality of life (Adult Eosinophilic Esophagitis Quality-of-Life and Patient Reported Outcome Measurement Information System Global Health questionnaires). Individuals without histological response to 1FED could proceed to 6FED, and those without histological response to 6FED could proceed to swallowed topical fluticasone propionate 880 μg twice per day (with unrestricted diet), for 6 weeks. Histological remission after switching therapy was assessed as a secondary endpoint. Efficacy and safety analyses were done in the intention-to-treat (ITT) population. This trial is registered on ClinicalTrials.gov, NCT02778867, and is completed.

FINDINGS

Between May 23, 2016, and March 6, 2019, 129 patients (70 [54%] men and 59 [46%] women; mean age 37·0 years [SD 10·3]) were enrolled, randomly assigned to 1FED (n=67) or 6FED (n=62), and included in the ITT population. At 6 weeks, 25 (40%) of 62 patients in the 6FED group had histological remission compared with 23 (34%) of 67 in the 1FED group (difference 6% [95% CI -11 to 23]; p=0·58). We found no significant difference between the groups at stricter thresholds for partial remission (≤10 eos/hpf, difference 7% [-9 to 24], p=0·46; ≤6 eos/hpf, 14% [-0 to 29], p=0·069); the proportion with complete remission was significantly higher in the 6FED group than in the 1FED group (difference 13% [2 to 25]; p=0·031). Peak eosinophil counts decreased in both groups (geometric mean ratio 0·72 [0·43 to 1·20]; p=0·21). For 6FED versus 1FED, mean changes from baseline in EoEHSS (-0·23 vs -0·15; difference -0·08 [-0·21 to 0·05]; p=0·23), EREFS (-1·0 vs -0·6; difference -0·4 [-1·1 to 0·3]; p=0·28), and EEsAI (-8·2 vs -3·0; difference -5·2 [-11·2 to 0·8]; p=0·091) were not significantly different. Changes in quality-of-life scores were small and similar between the groups. No adverse event was observed in more than 5% of patients in either diet group. For patients without histological response to 1FED who proceeded to 6FED, nine (43%) of 21 reached histological remission; for patients without histological response to 6FED who proceeded to fluticasone propionate, nine (82%) of 11 reached histological remission.

INTERPRETATION

Histological remission rates and improvements in histological and endoscopic features were similar after 1FED and 6FED in adults with eosinophilic oesophagitis. 6FED had efficacy in just less than half of 1FED non-responders and steroids had efficacy in most 6FED non-responders. Our findings indicate that eliminating animal milk alone is an acceptable initial dietary therapy for eosinophilic oesophagitis.

FUNDING

US National Institutes of Health.

The Role of Benralizumab in Eosinophilic Immune Dysfunctions: A Case Report-Based Literature Review

In the past years, the knowledge of eosinophils playing a primary pathophysiologic role in several associated conditions has led to the development of biologics targeting therapies aiming at normalizing the immune response, reducing chronic inflammation, and preventing tissue damage. To better illustrate the potential relationship between different eosinophilic immune dysfunctions and the effects of biological therapies in this scenario, here, we present a case of a 63-year-old male first referred to our department in 2018 with a diagnosis of asthma, polyposis, and rhinosinusitis and presenting a suspicion of nonsteroidal anti-inflammatory drugs' allergy. He also had a past medical history of eosinophilic gastroenteritis/duodenitis (eosinophilia counts >50 cells/high-power field HPF). The use of multiple courses of corticosteroid therapy failed to completely control these conditions. In October 2019, after starting benralizumab (an antibody directed against the alpha chain of the IL-5 cytokine receptor) as add-on treatment for severe eosinophilic asthma, important clinical improvements were reported both on the respiratory (no asthma exacerbations) and gastrointestinal systems (eosinophilia count 0 cells/HPF). Patients' quality of life also increased. Since June 2020, systemic corticosteroid therapy was reduced without worsening of gastrointestinal symptoms or eosinophilic inflammation. This case warns of the importance of early recognition and appropriate individualized treatment of eosinophilic immune dysfunctions and suggests the conduction of further larger studies on the use of benralizumab in gastrointestinal syndromes aiming at better understanding its relying mechanisms of action in the intestinal mucosa.

Clinical guidance for the use of dupilumab in eosinophilic esophagitis: A yardstick

The Joint Task Force for the American Academy of Allergy Asthma Immunology and American College of Allergy Asthma Immunology and the American Gastroenterology Association recently published guidelines for the management of eosinophilic esophagitis (EoE). Because the guideline was published, dupilumab became the first and only medication to gain regulatory approval for the treatment of EoE. This expert opinion document provides a framework for how the clinician can consider using dupilumab in the treatment strategy for patients with EoE.

Approach to the patient with suspected hypereosinophilic syndrome

Hypereosinophilic syndromes (HES) are a heterogenous group of rare disorders with clinical manifestations ranging from fatigue to life-threatening endomyocardial fibrosis and thromboembolic events. Given the broad differential diagnosis of HES, a comprehensive approach is needed to identify potential secondary (treatable) causes and define end-organ manifestations. Classification by clinical HES subtype is also useful in terms of assessing prognosis and guiding therapy. Corticosteroids remain the mainstay of initial therapy in the setting of acute, life-threatening PDGFR mutation-negative HES. Whereas the recent availability of eosinophil-targeted therapies with extraordinary efficacy and little apparent toxicity is changing the treatment paradigm, especially for idiopathic HES and overlap syndromes, questions remain unanswered regarding the choice of agent, impact of combination therapies, and long-term effects of eosinophil depletion. This review provides a case-based discussion of the differential diagnosis of HES, including the classification by clinical HES subtype. Treatment options are reviewed, including novel eosinophil-targeted agents recently approved for the treatment of HES and/or other eosinophil-associated disorders. Primary (myeloid) disorders associated with hypereosinophilia are not be addressed in depth in this review.

Relapse of Eosinophilic Esophagitis on Dupilumab

Dupilumab is approved for the treatment of eosinophilic esophagitis (EoE). We report a teenager with difficult-to-treat EoE on topical corticosteroids (TS) who achieved clinical and histological remission when initiated on dupilumab for a primary indication of atopic dermatitis. However, when his TS were weaned after achieving remission, his disease relapsed with worsening of his dysphagia and a peak eosinophilic count (PEC) of 55 eosinophils per high power field (eos/hpf). Upon restarting TS to his ongoing dupilumab, symptoms fully resolved, and he achieved histologic remission (PEC 10 eos/hpf). This report underscores the: (1) importance of longitudinal monitoring for EoE patients on dupilumab, (2) unmet need for guidance on how to transition EoE patients on traditional therapies to dupilumab, and (3) need for longitudinal follow-up data on dupilumab to help personalize therapy for EoE patients.

Eosinophils in the Gastrointestinal Tract: Key Contributors to Neuro-Immune Crosstalk and Potential Implications in Disorders of Brain-Gut Interaction

Eosinophils are innate immune granulocytes actively involved in defensive responses and in local and systemic inflammatory processes. Beyond these effector roles, eosinophils are fundamental to maintaining homeostasis in the tissues they reside. Gastrointestinal eosinophils modulate barrier function and mucosal immunity and promote tissue development through their direct communication with almost every cellular component. This is possible thanks to the variety of receptors they express and the bioactive molecules they store and release, including cytotoxic proteins, cytokines, growth factors, and neuropeptides and neurotrophines. A growing body of evidence points to the eosinophil as a key neuro-immune player in the regulation of gastrointestinal function, with potential implications in pathophysiological processes. Eosinophil–neuron interactions are facilitated by chemotaxis and adhesion molecules, and the mediators released may have excitatory or inhibitory effects on each cell type, with physiological consequences dependent on the type of innervation involved. Of special interest are the disorders of the brain–gut interaction (DBGIs), mainly functional dyspepsia (FD) and irritable bowel syndrome (IBS), in which mucosal eosinophilia and eosinophil activation have been identified. In this review, we summarize the main roles of gastrointestinal eosinophils in supporting gut homeostasis and the evidence available on eosinophil–neuron interactions to bring new insights that support the fundamental role of this neuro-immune crosstalk in maintaining gut health and contributing to the pathophysiology of DBGIs.