Reduced FcepsilonRI-mediated release of asthma-promoting cytokines and chemokines from human basophils during omalizumab therapy

The new biologic drugs: Which children with asthma should get what?

Novel biologics (targeted antibody therapies) have revolutionized the management of severe childhood asthma. However, it is important that the right biologic is selected for the right patient, and understanding the evidence base for each biologic is crucial. Currently, four biologics (all monoclonal antibodies) are licensed in the UK for the treatment of children with severe asthma - omalizumab (Xolair), mepolizumab (Nucala), and dupilumab (Dupixent) in children aged 6 years and over; and tezepelumab (Tezspire), only in children aged 12 years and over. Tezepelumab is the only licensed biological that may be beneficial in severe asthma without evidence of Type 2 inflammation. All have a good safety profile but varying degrees of clinical efficacy in children, with wide variation in treatment responsiveness between individual patients. When selecting biologics for severe asthma, it is essential to remember the limitations of the current pediatric evidence. At present, there are no results from randomized, head-to-head trials of biologics in severe asthma. TREAT is an ongoing trial comparing omalizumab to mepolizumab and will be one of the first to provide such evidence. We must be especially aware of the dangers of extrapolating data from adults to children, because the pathophysiology and role of biomarkers may differ significantly from adult asthma. Given the current level of knowledge, even after treatment has been initiated, children should be regularly reviewed to determine the efficacy of treatment, side-effect profile and consideration of when treatment with the biologic should be discontinued.

The Incredible Adventure of Omalizumab

The basis of our current understanding of allergies begins with the discovery of IgE in the mid-1960s. The whole theory of the physiology and pathophysiology of allergic diseases, including rhinitis and asthma, dates from that period. Among the key regions of IgE identified were the FAB (fragment antigen binding) portion that has the ability to capture allergens, and the Cε3 domain, through which IgE binds to its membrane receptor. It was then postulated that blocking IgE at the level of the Cε3 domain would prevent it from binding to its receptor and thus set in motion the allergic cascade. This was the beginning of the development of omalizumab, a monoclonal antibody with an anti-IgE effect. In this article, we review the pathophysiology of allergic disease and trace the clinical development of omalizumab. We also review the benefits of omalizumab treatment that are apparently unrelated to allergies, such as its effect on immunity and bronchial remodeling.

Solar Urticaria: An Ambispective Study in a Long-term Follow-up Cohort with Emphasis on Therapeutic Predictors and Outcomes

Solar urticaria is a rare photodermatosis with several unknown pathogenic, clinical and therapeutic aspects. This study analysed the clinical and therapeutic features of a long-term follow-up solar urticaria cohort, with a focus on omalizumab management and outcomes, and characterized omalizumab response with the use of the high-affinity immunoglobulin E (IgE) receptor (FcεRI) and the Urticaria Control Test. An observational, unicentric, ambispective study was conducted from 2007 to 2023. Solar urticaria was diagnosed in 41 patients with a median follow-up of 60 months. Thirteen patients were prescribed omalizumab, with a median treatment time of 48 months. A significant decrease in FcεRI baseline levels and subsequent median increase in Urticaria Control Test was evidenced after omalizumab prescription in all patients. Drug survival at 48 months was at 88.9%. Omalizumab stepping-down protocol led to sustained omalizumab discontinuation in only 1 patient. Median basal Urticaria Control Test was lower (p < 0.01) in patients who were prescribed omalizumab and in patients without remission. This study contributes to our knowledge of omalizumab outcomes in real-life clinical practice and highlights the pathogenic importance of IgE-mediated pathways in solar urticaria, where FcεRI emerges as a possible biomarker of omalizumab response.

Developments in the Management of Severe Asthma in Children and Adolescents: Focus on Dupilumab and Tezepelumab

Severe asthma in children and adolescents exerts a substantial health, financial, and societal burden. Severe asthma is a heterogeneous condition with multiple clinical phenotypes and underlying inflammatory patterns that might be different in individual patients. Various add-on treatments have been developed to treat severe asthma, including monoclonal antibodies (biologics) targeting inflammatory mediators. Biologics that are currently approved to treat children (≥ 6 years of age) or adolescents (≥ 12 years of age) with severe asthma include: anti-immunoglobulin E (omalizumab), anti-interleukin (IL)-5 (mepolizumab), anti-IL5 receptor (benralizumab), anti-IL4/IL13 receptor (dupilumab), and antithymic stromal lymphopoietin (TSLP) (tezepelumab). However, access to these targeted treatments varies across countries and relies on few and crude indicators. There is a need for better treatment stratification to guide which children might benefit from these treatments. In this narrative review we will assess the most recent developments in the treatment of severe pediatric asthma, as well as potential biomarkers to assess treatment efficacy for this patient population.

Effect of Neurokinin-1 Receptor Knockdown on the Expression of RANTES in Allergic Rhinitis

BACKGROUND

Neurokinin-1 receptor (NK-1R) and normal T cell expressed and secreted (RANTES) have been shown to play important roles in allergic rhinitis (AR). However, whether the regulating effect of NK-1R in AR is achieved via RANTES remains unknown.

METHODS

In the present study, Sprague-Dawley rats were sensitized and challenged with ovalbumin to make AR models. During the challenge period, the rats were treated intranasally with NK-1R-specific small interfering RNA (siRNA) for NKR group, negative siRNA for NCS group, rats in NSAR group and NS group were given saline. The amount of nasal secretion and the numbers of nose rubs and sneezes were measured in each rat. The levels of NK-1R and RANTES in the nasal mucosal tissues were determined through real-time fluorescence quantitative RT-PCR and immunohistochemical staining. The numbers of eosinophils in the collected nasal lavage fluid (NLF) were counted, and the concentration of RANTES in NLF was determined by enzyme-linked immunosorbent assay.

RESULTS

Compared with that in the NS group, the expression of NK-1R and RANTES was significantly higher in the nasal mucosa of NSAR and NCS group rats. The sneezing and nose rubbing counts and the amount of nasal secretions were increased significantly in the NSAR and NCS groups. Rats in the NKR group experienced greater relief from AR symptoms than rats in the NSAR and NCS groups. Furthermore, knockdown of NK-1R expression also significantly eliminated RANTES expression and eosinophil infiltration in the nasal mucosa of NKR group rats.

CONCULSION

For the first time, we show that intranasal treatment with NK-1R-specific siRNA can significantly decrease RANTES expression, AR-related symptoms, and eosinophil inflammation, suggesting that the regulating effect of NK-1R in the development of AR occurs via alteration of RANTES expression.

Successful treatment of urticarial vasculitis with omalizumab in children: a case series

Urticarial vasculitis (UV) is a small vessel leucocytoclastic vasculitis, which often needs to be distinguished from urticaria and other dermatoses. Treatment of UV in children is challenging because of the unsatisfying efficacy of antihistamines and the safety concern of long-term systemic corticosteroids or immunosuppressive agents. As a classic biological agent widely used in chronic spontaneous urticaria, omalizumab might also be a potential therapeutic option in the treatment of children with UV. This report presented four children, aged 4-6 years, with glucocorticoid-unresponsive UV successfully treated by omalizumab, thus providing evidence that omalizumab can be used to treat UV with good efficacy and tolerability in the paediatric population.

The Effectiveness of Oral Immunotherapy in Patients with Sesame Anaphylaxis using Omalizumab

OBJECTIVE

Sesame allergy is the most prevalent allergy to seeds. Oral immunotherapy (OIT) is defined as continuous consumption of an allergen at special doses and time. Omalizumab (Anti-IgE) increases tolerance to allergens used in OIT. This study evaluated the effectiveness of a new sesame OIT protocol in patients with sesame anaphylaxis in combination with omalizumab.

METHODS

In this prospective open-label interventional trial study, 11 patients with a history of sesame anaphylaxis were enrolled after confirmation by oral food challenge (OFC) test. At baseline, skin prick test (SPT) and skin prick to prick (SPP) test were performed. Serum sesame-specific IgE (sIgE) levels were measured. The maintenance phase was continued at home with daily sesame intake for 4 months. At the end of month 4, the OFC and above-mentioned tests were repeated to evaluate the treatment effectiveness.

RESULTS

All 11 patients who underwent sesame OIT after 4 months could tolerate a dietary challenge of 22 ml tahini (natural sesame seed, equal to 5,000 mg of sesame protein and higher) and the average of wheal diameter in the SPT and SPP tests significantly decreased after desensitization.

CONCLUSION

This OIT protocol may be a promising desensitization strategy for patients with sesame anaphylaxis. Also, omalizumab appears to have reduced the severity of reactions.

Basophils as a potential therapeutic target in cancer

Basophils, which are considered as redundant relatives of mast cells and the rarest granulocytes in peripheral circulation, have been neglected by researchers in the past decades. Previous studies have revealed their vital roles in allergic diseases and parasitic infections. Intriguingly, recent studies even reported that basophils might be associated with cancer development, as activated basophils synthesize and release a variety of cytokines and chemokines in response to cancers. However, it is still subject to debate whether basophils function as tumor-protecting or tumor-promoting components; the answer may depend on the tumor biology and the microenvironment. Herein, we reviewed the role of basophils in cancers, and highlighted some potential and promising therapeutic strategies.

Novel Approaches in the Inhibition of IgE-Induced Mast Cell Reactivity in Food Allergy

Allergy is an IgE-dependent type-I hypersensitivity reaction that can lead to life-threatening systemic symptoms such as anaphylaxis. In the pathogenesis of the allergic response, the common upstream event is the binding of allergens to specific IgE, inducing cross-linking of the high-affinity FcεRI on mast cells, triggering cellular degranulation and the release of histamine, proteases, lipids mediators, cytokines and chemokines with inflammatory activity. A number of novel therapeutic options to curb mast cell activation are in the pipeline for the treatment of severe allergies. In addition to anti-IgE therapy and allergen-specific immunotherapy, monoclonal antibodies targeted against several key Th2/alarmin cytokines (i.e. IL-4Rα, IL-33, TSLP), active modification of allergen-specific IgE (i.e. inhibitory compounds, monoclonal antibodies, de-sialylation), engagement of inhibitory receptors on mast cells and allergen-specific adjuvant vaccines, are new promising options to inhibit the uncontrolled release of mast cell mediators upon allergen exposure. In this review, we critically discuss the novel approaches targeting mast cells limiting allergic responses and the immunological mechanisms involved, with special interest on food allergy treatment.

IgE-Binding Monocytes Have an Enhanced Ability to Produce IL-8 (CXCL8) in Animals with Naturally Occurring Allergy

IL-8 is a potent chemokine that recruits neutrophils and basophils to promote inflammation in many species. IL-8 is produced by many cell types, including monocytes. In this study, we report a novel role for IgE-binding monocytes, a rare peripheral immune cell type, to promote allergic inflammation through IL-8 production in a horse model of natural IgE-mediated allergy. We developed a mAb with confirmed specificity for both recombinant and native equine IL-8 for flow cytometric analysis. Equine IL-8 was produced by CD14⁺/MHC class II⁺/CD16^- monocytes, including a subpopulation of IgE-binding monocytes, following stimulation with LPS. In addition, IgE cross-linking induced IL-8 production by both peripheral blood basophils and IgE-binding monocytes. IL-8 production was compared between healthy horses and those with a naturally occurring IgE-mediated skin allergy, Culicoides hypersensitivity. Allergic horses had significantly higher percentages of IL-8⁺ IgE-binding monocytes after IgE cross-linking. In contrast, frequencies of IL-8⁺ basophils after IgE cross-linking were similar in all horses, regardless of allergic disease, highlighting IgE-binding monocytes as a novel source of IL-8 during allergy. We concluded that IgE-binding monocytes from allergic individuals have an increased capacity for IL-8 production and likely contribute to the recruitment of innate immune cells during IgE-mediated allergy and promotion of inflammation during repeated allergen contact.

An Omalizumab Biobetter Antibody With Improved Stability and Efficacy for the Treatment of Allergic Diseases

The critical role of IgE in allergic diseases is well-documented and clinically proven. Omalizumab, a humanized anti-IgE antibody, was the first approved antibody for the treatment of allergic diseases. Nevertheless, omalizumab still has some limitations, such as product instability and dosage restriction in clinical application. In this study, we attempted to develop an omalizumab biobetter antibody with the potential to overcome its limitations. We removed two aspartic acid isomerization hotspots in CDRs of omalizumab to improve antibody candidate’s stability. Meanwhile, several murine amino acids in the framework region of omalizumab were replaced with human source to reduce the potential immunogenicity. Yeast display technology was then applied to screen antibody candidates with high binding affinity to IgE. Moreover, YTE mutation in Fc fragment was introduced into the candidates for extending their serum half-life. A lead candidate, AB1904Am15, was screened out, which showed desired biophysical properties and improved stability, high binding affinity and elevated potency in vitro, prolonged half-life in human FcRn transgenic mouse, and enhanced in vivo efficacy in cynomolgus monkey asthma model. Overall, our study developed a biobetter antibody of omalizumab, AB1904Am15, which has the potential to show improved clinical benefit in the treatment of allergic diseases.

Effects of omalizumab on basophils: Potential biomarkers in asthma and chronic spontaneous urticaria

Omalizumab is an anti-IgE humanized monoclonal antibody approved for the treatment of severe asthma and chronic spontaneous urticaria. Omalizumab binds free serum IgE and antagonizes its interaction with FcεRI, which is considered the main pharmacodynamic mechanism responsible for the clinical response to the treatment. The reduction of IgE serum concentration down-regulates the cellular expression of FcεRI on basophils. However, the biological events occurring on basophils during the therapy with omalizumab are multiple and complex. Here we review the current evidence regarding the specific biological effects of omalizumab on basophils in patients with asthma and chronic spontaneous urticaria. In addition to the modulation of IgE receptors, omalizumab may affect basophils homeostasis, intra-cellular signaling, cellular responsiveness/activation and cytokine release. These effects may be partially responsible for the clinical success of omalizumab and potentially provide useful biological markers for future assessment of the clinical response to the treatment. However, further investigation is required to better elucidate the role of basophils during the treatment with omalizumab.

Is There a Role for Basophils in Cancer?

Basophils were identified in human peripheral blood by Paul Ehrlich over 140 years ago. Human basophils represent <1% of peripheral blood leukocytes. During the last decades, basophils have been described also in mice, guinea pigs, rabbits, and monkeys. There are many similarities, but also several immunological differences between human and mouse basophils. There are currently several strains of mice with profound constitutive or inducible basophil deficiency useful to prove that these cells have specific roles in vivo. However, none of these mice are solely and completely devoid of all basophils. Therefore, the relevance of these findings to humans remains to be established. It has been known for some time that basophils have the propensity to migrate into the site of inflammation. Recent observations indicate that tissue resident basophils contribute to lung development and locally promote M2 polarization of macrophages. Moreover, there is increasing evidence that lung-resident basophils exhibit a specific phenotype, different from circulating basophils. Activated human and mouse basophils synthesize restricted and distinct profiles of cytokines. Human basophils produce several canonical (e.g., VEGFs, angiopoietin 1) and non-canonical (i.e., cysteinyl leukotriene C₄) angiogenic factors. Activated human and mouse basophils release extracellular DNA traps that may have multiple effects in cancer. Hyperresponsiveness of basophils has been demonstrated in patients with JAK2^V617F-positive polycythemia vera. Basophils are present in the immune landscape of human lung adenocarcinoma and pancreatic cancer and can promote inflammation-driven skin tumor growth. The few studies conducted thus far using different models of basophil-deficient mice have provided informative results on the roles of these cells in tumorigenesis. Much more remains to be discovered before we unravel the hitherto mysterious roles of basophils in human and experimental cancers.

Safety and Tolerability of Omalizumab: A Randomized Clinical Trial of Humanized Anti-IgE Monoclonal Antibody in Systemic Lupus Erythematosus

OBJECTIVE

Autoreactive IgE antibodies have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). We hypothesize that omalizumab, a monoclonal antibody binding IgE, may improve SLE activity by reducing type I interferon (IFN) production by hampering plasmacytoid dendritic cells and basophil activation. This study was undertaken to assess the safety, tolerability, and clinical efficacy of omalizumab in mild to moderate SLE.

METHODS

Sixteen subjects with SLE and a Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score of ≥4 and elevated autoreactive IgE antibody levels were randomized to receive omalizumab or placebo (2:1) for 16 weeks, followed by 16 weeks of open-label treatment and a 4-week washout period. The SLEDAI-2K score, British Isles Lupus Assessment Group index (BILAG 2004) score, and physician's global assessment of disease activity were recorded at each visit. The type I IFN-induced gene signature was determined using quantitative polymerase chain reaction.

RESULTS

Omalizumab was well tolerated with no allergic reactions, and mostly mild adverse events comparable to those experienced with placebo treatment. SLEDAI-2K scores improved in the omalizumab group compared to the placebo group at week 16 (P = 0.038), as well as during the open-label phase in subjects initially receiving placebo (P = 0.02). No worsening in BILAG scores or the physician's global assessment was detected. There was a trend toward a reduction in IFN gene signature in subjects treated with omalizumab (P = 0.11), especially in subjects with a high baseline IFN signature (P = 0.052).

CONCLUSION

Our findings indicate that omalizumab is well tolerated in SLE and is associated with improvement in disease activity. Larger randomized clinical trials will be needed to assess the efficacy of omalizumab in patients with SLE.

Omalizumab may decrease the thickness of the reticular basement membrane and fibronectin deposit in the bronchial mucosa of severe allergic asthmatics

Introduction: Immunoglobulin E is an important modulator of the inflammatory reaction in allergic asthma. It also contributes to airway remodeling in the course of the disease. The authors evaluated airway structural changes in severe allergic asthma during the omalizumab therapy. Patients and methods: The study included 13 patients with severe allergic asthma treated with omalizumab for at least one year. In each patient clinical, laboratory, and spirometry parameters were evaluated before and after the treatment. In addition, bronchoscopy with bronchial mucosa biopsy and bronchoalveolar lavage was performed. The basal lamina thickness, inflammatory cell infiltration, fibronectin, as well as type I and III collagen accumulation were assessed in bronchial mucosa specimens, together with the assessment of bronchoalveolar lavage cellularity. Results: The omalizumab therapy led to a decrease in the basal lamina thickness (p = 0.002), and to a reduction in fibronectin (p = 0.02), but not collagen deposits in the bronchial mucosa. The decrease in fibronectin accumulation was associated with an improvement in asthma control and quality of life (p = 0.01, both), and a diminished dose of systemic corticosteroids (p = 0.001). It was also associated with a tendency towards reduction of the eosinophil count in the peripheral blood, bronchoalveolar lavage fluid, and bronchial mucosa specimens. Conclusion: Our study has shown that omalizumab, effective in the treatment of severe allergic asthma, may also decrease unfavorable structural airway changes in allergic asthmatics, at least with respect to the fibronectin deposit and an increased thickness of the basal lamina. However, more extensive observational studies are needed to verify the above hypothesis.

Omalizumab and unmet needs in severe asthma and allergic comorbidities in Japanese children

Childhood asthma is one condition within a family of allergic diseases, which includes allergic rhinitis, atopic dermatitis, and food allergy, among others. Omalizumab is an anti-IgE antibody therapy that was approved in Japan for children with asthma and added to the Japanese pediatric asthma guidelines in 2017. This review highlights the Japanese clinical perspectives in pediatric allergic asthma, and consideration for allergic comorbidities, and reflects on omalizumab clinical trials in progress to present comprehensive future opportunities.

Human mast cells and basophils-How are they similar how are they different?

Mast cells and basophils are key contributors to allergies and other inflammatory diseases since they are the most prominent source of histamine as well as numerous additional inflammatory mediators which drive inflammatory responses. However, a closer understanding of their precise roles in allergies and other pathological conditions has been marred by the considerable heterogeneity that these cells display, not only between mast cells and basophils themselves but also across different tissue locations and species. While both cell types share the ability to rapidly degranulate and release histamine following high-affinity IgE receptor cross-linking, they differ markedly in their ability to either react to other stimuli, generate inflammatory eicosanoids or release immunomodulating cytokines and chemokines. Furthermore, these cells display considerable pharmacological heterogeneity which has stifled attempts to develop more effective anti-allergic therapies. Mast cell- and basophil-specific transcriptional profiling, at rest and after activation by innate and adaptive stimuli, may help to unravel the degree to which these cells differ and facilitate a clearer understanding of their biological functions and how these could be targeted by new therapies.

Treatment of chronic spontaneous urticaria: Immunomodulatory approaches

This paper summarizes and reviews the mechanisms of action and data concerning efficacy of recommended treatments as well as other treatments that have been tested, independently of the outcomes, in the management of chronic spontaneous urticaria. Due to the central role of mast cells, basophils and histamine in the pathophysiology of this disease, H₁-antihistamines remain the first-line treatment. However, current knowledge about this complex disease, also recognizes an important role for T lymphocytes, B lymphocytes, and autoantibodies. Implications of these others mediators thus provide further targets for treatment. Indeed, agents previously used to treat other autoimmune and inflammatory diseases, have demonstrated efficacy in chronic spontaneous urticaria and are therefore potential therapeutic alternatives for antihistamine unresponsive patients.

Mechanisms of action that contribute to efficacy of omalizumab in chronic spontaneous urticaria

The monoclonal anti-immunoglobulin E (IgE) antibody, omalizumab, was the first drug approved for use in patients with chronic idiopathic/spontaneous urticaria (CIU/CSU) who remain symptomatic despite H₁ -antihistamine treatment. Omalizumab binds to free IgE, which lowers free IgE levels and causes FcεRI receptors on basophils and mast cells to be downregulated. It has been shown to improve symptoms of CIU/CSU, but its mechanism of action is not currently understood. Potential mechanisms in CIU/CSU include reducing mast cell releasability, reversing basopenia and improving basophil IgE receptor function, reducing activity of IgG autoantibodies against FcεRI and IgE, reducing activity of IgE autoantibodies against an antigen or autoantigen that has yet to be definitively identified, reducing the activity of intrinsically 'abnormal' IgE, and decreasing in vitro coagulation abnormalities associated with disease activity. However, none of these theories alone or in combination fully account for the pattern of symptom improvement seen with omalizumab therapy, and therefore, no one mechanism is likely to be the definitive mechanism of action. Additional research is needed to further clarify the involvement of omalizumab in relieving symptoms associated with the complex, multifactorial pathogenesis of CIU/CSU.

Allergen Valency, Dose, and FcεRI Occupancy Set Thresholds for Secretory Responses to Pen a 1 and Motivate Design of Hypoallergens

Ag-mediated crosslinking of IgE-FcεRI complexes activates mast cells and basophils, initiating the allergic response. Of 34 donors recruited having self-reported shrimp allergy, only 35% had significant levels of shrimp-specific IgE in serum and measurable basophil secretory responses to rPen a 1 (shrimp tropomyosin). We report that degranulation is linked to the number of FcεRI occupied with allergen-specific IgE, as well as the dose and valency of Pen a 1. Using clustered regularly interspaced palindromic repeat-based gene editing, human RBL^rαKO cells were created that exclusively express the human FcεRIα subunit. Pen a 1-specific IgE was affinity purified from shrimp-positive plasma. Cells primed with a range of Pen a 1-specific IgE and challenged with Pen a 1 showed a bell-shaped dose response for secretion, with optimal Pen a 1 doses of 0.1-10 ng/ml. Mathematical modeling provided estimates of receptor aggregation kinetics based on FcεRI occupancy with IgE and allergen dose. Maximal degranulation was elicited when ∼2700 IgE-FcεRI complexes were occupied with specific IgE and challenged with Pen a 1 (IgE epitope valency of ≥8), although measurable responses were achieved when only a few hundred FcεRI were occupied. Prolonged periods of pepsin-mediated Pen a 1 proteolysis, which simulates gastric digestion, were required to diminish secretory responses. Recombinant fragments (60-79 aa), which together span the entire length of tropomyosin, were weak secretagogues. These fragments have reduced dimerization capacity, compete with intact Pen a 1 for binding to IgE-FcεRI complexes, and represent a starting point for the design of promising hypoallergens for immunotherapy.

Advances in the understanding and clinical management of mastocytosis and clonal mast cell activation syndromes

Clonal mast cell activation syndromes and indolent systemic mastocytosis without skin involvement are two emerging entities that sometimes might be clinically difficult to distinguish, and they involve a great challenge for the physician from both a diagnostic and a therapeutic point of view. Furthermore, final diagnosis of both entities requires a bone marrow study; it is recommended that this be done in reference centers. In this article, we address the current consensus and guidelines for the suspicion, diagnosis, classification, treatment, and management of these two entities.

Omalizumab Treatment Response in a Population With Severe Allergic Asthma and Overlapping COPD

BACKGROUND

Asthma and COPD are common airway diseases. Individuals with overlapping asthma and COPD experience increased health impairment and severe disease exacerbations. Efficacious treatment options are required for this population. Omalizumab (anti-IgE) therapy is effective in patients with severe persistent asthma, but limited data are available on efficacy in populations with overlapping asthma and COPD.

METHODS

Data from the Australian Xolair Registry were used to compare treatment responses in individuals with asthma-COPD overlap with responses in patients with severe asthma alone. Participants were assessed at baseline and after 6 months of omalizumab treatment. We used several different definitions of asthma-COPD overlap. First, we compared participants with a previous physician diagnosis of COPD to participants with no COPD diagnosis. We then made comparisons based on baseline lung function, comparing participants with an FEV₁ < 80% predicted to those with an FEV₁ > 80% predicted after bronchodilator use. In the population with an FEV₁< 80%, analysis was further stratified based on smoking history.

RESULTS

Omalizumab treatment markedly improved asthma control and health-related quality of life in all populations assessed based on the Asthma Control Questionnaire and Asthma Quality of Life Questionnaire scores. Omalizumab treatment did not improve lung function (FEV₁, FVC, or FEV₁/FVC ratio) in populations that were enriched for asthma-COPD overlap (diagnosis of COPD or FEV₁ < 80%/ever smokers).

CONCLUSIONS

Our study suggests that omalizumab improves asthma control and health-related quality of life in individuals with severe allergic asthma and overlapping COPD. These findings provide real-world efficacy data for this patient population and suggest that omalizumab is useful in the management of severe asthma with COPD overlap.

Anti-IgE treatment, airway inflammation and remodelling in severe allergic asthma: current knowledge and future perspectives

Asthma is a disorder of the airways involving various inflammatory cells and mediators and characterised by bronchial hyperresponsiveness, chronic inflammation and structural alterations in the airways, also known as remodelling. IgE is an important mediator of allergic reactions and has a central role in allergic asthma pathophysiology, as it is implicated in both the early and late phase allergic response. Moreover, clinical and mechanistic evidence has lately emerged, implicating IgE in the development of airway remodelling. The use of monoclonal antibodies targeting IgE, such as omalizumab, has proven very effective in improving respiratory symptoms and quality of life, while reducing asthma exacerbations, emergency room visits and the use of systemic corticosteroids in allergic severe asthma. These effects are believed to be mainly mediated by omalizumab's inhibitory effect on the initiation and further propagation of the allergic inflammation cascade. However, there is evidence to suggest that anti-IgE treatment remains effective long after it has been discontinued. In part, these findings could be attributed to the possible ameliorating effects of anti-IgE treatment on airway remodelling. In this review, we discuss recent findings supporting the notion that anti-IgE treatment modulates the complex immune responses that manifest clinically as asthma and ameliorates airway remodelling changes often observed in allergic severe asthma phenotypes.

Efficacy and safety of multiple doses of QGE031 (ligelizumab) versus omalizumab and placebo in inhibiting allergen-induced early asthmatic responses

BACKGROUND

Omalizumab is an established anti-IgE therapy for the treatment of allergic diseases that prevents IgE from binding to its receptor. QGE031 is an investigational anti-IgE antibody that binds IgE with higher affinity than omalizumab.

OBJECTIVE

This study compared the effects of QGE031 with those of omalizumab on clinical efficacy, IgE levels, and FcεRI expression in a clinical model of allergic asthma.

METHODS

Thirty-seven patients with mild allergic asthma were randomized to subcutaneous omalizumab, placebo, or QGE031 at 24, 72, or 240 mg every 2 weeks for 10 weeks in a double-blind, parallel-group multicenter study. Inhaled allergen challenges and skin tests were conducted before dosing and at weeks 6, 12, and 18, and blood was collected until 24 weeks after the first dose.

RESULTS

QGE031 elicited a concentration- and time-dependent change in the provocative concentration of allergen causing a 15% decrease in FEV₁ (allergen PC₁₅) that was maximal and approximately 3-fold greater than that of omalizumab (P = .10) and 16-fold greater than that of placebo (P = .0001) at week 12 in the 240-mg cohort. Skin responses reached 85% suppression at week 12 in the 240-mg cohort and were maximal at week 18. The top doses of QGE031 consistently suppressed skin test responses among subjects but had a variable effect on allergen PC₁₅ (2-fold to 500-fold change). QGE031 was well tolerated.

CONCLUSION

QGE031 has greater efficacy than omalizumab on inhaled and skin allergen responses in patients with mild allergic asthma. These data support the clinical development of QGE031 as a treatment of asthma.

Anti-IgE treatment, airway inflammation and remodelling in severe allergic asthma: current knowledge and future perspectives

Asthma is a disorder of the airways involving various inflammatory cells and mediators and characterised by bronchial hyperresponsiveness, chronic inflammation and structural alterations in the airways, also known as remodelling. IgE is an important mediator of allergic reactions and has a central role in allergic asthma pathophysiology, as it is implicated in both the early and late phase allergic response. Moreover, clinical and mechanistic evidence has lately emerged, implicating IgE in the development of airway remodelling. The use of monoclonal antibodies targeting IgE, such as omalizumab, has proven very effective in improving respiratory symptoms and quality of life, while reducing asthma exacerbations, emergency room visits and the use of systemic corticosteroids in allergic severe asthma. These effects are believed to be mainly mediated by omalizumab's inhibitory effect on the initiation and further propagation of the allergic inflammation cascade. However, there is evidence to suggest that anti-IgE treatment remains effective long after it has been discontinued. In part, these findings could be attributed to the possible ameliorating effects of anti-IgE treatment on airway remodelling. In this review, we discuss recent findings supporting the notion that anti-IgE treatment modulates the complex immune responses that manifest clinically as asthma and ameliorates airway remodelling changes often observed in allergic severe asthma phenotypes.

Long-term efficacy of omalizumab in seven patients with treatment-resistant chronic spontaneous urticaria

BACKGROUND

Monoclonal anti-IgE antibody omalizumab is a promising therapeutic option in patients with chronic urticaria (CU) resistant to non-sedating H1-antihistamines (nsAH). However, data about its long-term efficacy and safety are still scant.

OBJECTIVE

We retrospectively analysed the clinical course of patients with severe recalcitrant CU that were treated in our department with omalizumab for a period greater than 24 months.

METHODS AND PATIENTS

Seven patients (six females, median 43 years) treated for a median of 35 months have been evaluated. Before treatment, all suffered from persistent symptoms despite receiving high doses of nsAH [4×/day], leukotriene antagonists and prednisolone (10-30 mg/day for a median duration of 48 months). Response to treatment was assessed using urticaria activity score (UAS) and a combined symptom/medication score.

RESULTS

There was a complete remission of disease in four patients after the first dose of omalizumab. Before the 5th administration, all patients had a UAS of 0. We found a significant improvement in UAS between pre-treatment and first dose (p=0.017) and a gradual decrease in the symptom/medication score over the course of the first five administrations. Tapering of prednisolone was possible in all patients. Administration intervals were gradually increased, although all experienced resurgence of symptoms in cycles greater than six weeks. There were no reported adverse reactions attributable to the drug.

CONCLUSION

Omalizumab was a safe and effective corticosteroid alternative for maintaining long-term remission of symptoms in these patients. Treatment intervals required individual patient-by-patient determination. The drug did not seem to alter the natural history of the disease.

Potential benefit of omalizumab in respiratory diseases

OBJECTIVE

To provide an overview of primary and secondary mechanisms associated with anti-IgE therapy and their relation to other potential indications in diseases affecting the respiratory tract.

DATA SOURCES

Literature from PubMed searches for publications providing insight into secondary mechanisms resulting from anti-IgE therapy and publications reporting on the use of omalizumab to treat conditions that affect the respiratory tract, other than severe atopic asthma.

STUDY SELECTIONS

Clinical trials or case reports were identified for asthma in patients without atopy, allergic rhinitis, nasal polyposis, and allergic bronchopulmonary aspergillosis.

RESULTS

There is substantial evidence from controlled trials supporting a benefit for allergic rhinitis. Case reports and series on more than 50 patients with allergic bronchopulmonary aspergillosis have been published, including patients with or without cystic fibrosis; most have reported benefits in terms of decreased steroid use, exacerbation rates, and, in patients with cystic fibrosis, improvement in lung function. Several small controlled studies on nasal polyposis have shown equivocal results. One small controlled trial in patients with nonatopic asthma showed a significant improvement for lung function but not in exacerbation rate or asthma scores.

CONCLUSION

Recent insight into the immunopathology of respiratory diseases should be used to identify patient populations likely to respond to anti-IgE therapy. Controlled clinical trials are needed to confirm efficacy and determine the clinical significance of the effects of omalizumab in these populations.

Effect of omalizumab on biomarkers in middle ear effusion in patients with eosinophilic otitis media

CONCLUSIONS

Eosinophil cationic protein (ECP) concentrations in middle ear effusion (MEE) in patients with eosinophilic otitis media (EOM) were significantly decreased at 3 months after the administration of omalizumab from the baseline level (p < 0.05). This study provides new evidence that omalizumab reduces eosinophilic inflammation in the middle ear and that the reduction of ECP may not be caused by suppression of interleukin (IL)-5 production in the middle ear mucosa.

OBJECTIVE

EOM is an intractable otitis media characterized by a highly viscous effusion containing eosinophils. We recently reported that anti-IgE therapy using omalizumab was efficacious in the treatment of EOM. To clarify the underlying mechanism, we determined changes in biomarkers in MEE related to eosinophilic inflammation after therapy.

METHODS

Nine patients with EOM received the anti-IgE agent omalizumab for 3 months. Among them, five patients continued anti-IgE therapy for longer than 1 year. Eight EOM patients without administration of omalizumab were also included in the study as controls. The concentrations of eosinophilic inflammatory markers such as ECP, IgE, IL-4, and IL-5 in MEE were measured before and after the administration of omalizumab.

RESULTS

After 3 months of omalizumab therapy, the ECP concentration in MEE was significantly reduced from the baseline level (p < 0.05), while no significant change of ECP in the serum was observed. The concentrations of IL-4 and IL-5 in MEE showed no significant change before and after the therapy in EOM patients treated with omalizumab.

Omalizumab: a review of its use in patients with severe persistent allergic asthma

Omalizumab (Xolair(®)) is a subcutaneously administered monoclonal antibody that targets circulating free IgE and prevents its interaction with the high-affinity IgE receptor (FCεRI), thereby interrupting the allergic cascade. In the EU, the drug is approved as add-on therapy in adults, adolescents and children aged ≥6 years with severe persistent allergic asthma. In well designed clinical trials, add-on omalizumab significantly reduced the asthma exacerbation rate (primary endpoint) compared with placebo in adults, adolescents and children with severe persistent allergic asthma. Furthermore, add-on omalizumab reduced the need for inhaled corticosteroids in adults and adolescents, and improved asthma control and symptoms, and asthma-related quality of life in all age groups. The efficacy of omalizumab was also demonstrated in the real-world setting, with add-on therapy leading to reduced rates of hospitalizations, emergency room visits and unscheduled doctor's visits, as well as improvements in asthma symptom scores and the physician's overall assessment of treatment response. More data are needed to determine the optimum duration of treatment, and currently the duration is at the discretion of the treating physician. Omalizumab was generally well tolerated in clinical trials; the most common adverse event was transient injection-site reactions. In cost-utility analyses modelled over a life-time horizon, add-on omalizumab was cost effective compared with standard therapy, with incremental cost-effectiveness ratios falling within generally accepted willingness-to-pay thresholds. Thus, in difficult-to-treat patients with severe persistent allergic asthma, omalizumab provides a valuable treatment option.

Basophils and allergic inflammation

Basophils were discovered by Paul Ehrlich in 1879 and represent the least abundant granulocyte population in mammals. The relative rarity of basophils and their phenotypic similarities with mast cells resulted in this cell lineage being historically overlooked, both clinically and experimentally. However, recent studies in human subjects and murine systems have shown that basophils perform nonredundant effector functions and significantly contribute to the development and progression of TH2 cytokine-mediated inflammation. Although the potential functions of murine and human basophils have provoked some controversy, recent genetic approaches indicate that basophils can migrate into lymphoid tissues and, in some circumstances, cooperate with other immune cells to promote optimal TH2 cytokine responses in vivo. This article provides a brief historical perspective on basophil-related research and discusses recent studies that have identified previously unappreciated molecules and pathways that regulate basophil development, activation, and function in the context of allergic inflammation. Furthermore, we highlight the unique effector functions of basophils and discuss their contributions to the development and pathogenesis of allergic inflammation in human disease. Finally, we discuss the therapeutic potential of targeting basophils in preventing or alleviating the development and progression of allergic inflammation.

Elevated serum IgE in recurrent aphthous stomatitis and associations with disease characteristics

OBJECTIVES

To characterize demographic, clinical and serological parameters in recurrent aphthous stomatitis (RAS) patients and analyse their association with serum immunoglobulin E (IgE) levels.

SUBJECTS AND METHODS

Forty-nine patients with RAS responded to a questionnaire that included demographic background, stress status, smoking habits, history and course of RAS episodes. They were also subjected to relevant laboratory tests, including determination of serum IgE levels.

RESULTS

A familial history of RAS was reported by 47.9% of the patients, stress in the previous year by 51.1% and smoking by 18.4%. Non-Caucasian origin, familial history of RAS, stress and smoking were associated with increased severity of RAS episodes. Haematological deficiencies were observed in 18.7% of RAS patients. Average IgE levels were increased and were significantly associated ‎with younger ‎age, ‎≤12 years of schooling, ‎female gender, ‎RAS ‎episode frequency of every ‎2 weeks‎,‎ early onset of RAS episodes and elevated C reactive protein levels.

CONCLUSION

Immunoglobulin E levels may be considered as part of the RAS patient's work-up. Further research is needed to identify biological mechanisms that account for the observed associations.

Treatment of severe cold contact urticaria with omalizumab: case reports

We report 2 patients with cold urticaria with different response to treatment with omalizumab (Xolair^®). Cold contact urticaria (CCU) is a common subtype of physical urticaria. It is characterized by the development of wheal and/or angioedema within minutes after cold contact. Clinical manifestation of CCU can range from mild, localized whealing to life-threatening anaphylactic shock reactions. Omalizumab has been described to be useful in cases of chronic urticaria and may be an interesting option for treatment of CCU. We describe one patient with significant and long-lasting improvement of symptoms and one without any improvement after anti-immunoglobulin E therapy. In our case reports, we want to highlight that there is still a small group of patients without benefit from omalizumab treatment. It is necessary to identify this minor subgroup of patients where omalizumab does not represent an effective treatment possibility.

Omalizumab: clinical use for the management of asthma

Omalizumab, a humanized monoclonal antibody that binds circulating IgE antibody, is a treatment option for patients with moderate to severe allergic asthma whose asthma is poorly controlled with inhaled corticosteroids and inhaled long-acting β₂ agonist bronchodilators. This review considers the mechanism of action, pharmacokinetics, efficacy, safety and place in management of omalizumab in asthma and focuses particularly on key articles published over the last three years. Omalizumab reduces IgE mediated airway inflammation and its effect on airway remodeling is under investigation. Recent long-term clinical trials confirm the benefits of omalizumab in reducing exacerbations and symptoms in adults and in children with moderate to severe allergic asthma. No clinical or immunological factor consistently predicts a good therapeutic response to omalizumab in allergic asthma. In responders, the duration of treatment is unclear. The main adverse effect of omalizumab is anaphylaxis, although this occurs infrequently. Preliminary data from a five-year safety study has raised concerns about increased cardiovascular events and a final report is awaited. Clinical trials are in progress to determine whether omalizumab has efficacy in the treatment of non-allergic asthma.

A randomized, placebo-controlled, dose-ranging study of single-dose omalizumab in patients with H1-antihistamine-refractory chronic idiopathic urticaria

BACKGROUND

Proof-of-concept studies with omalizumab in patients with chronic idiopathic urticaria (CIU) have shown significant decreases in mean urticaria activity scores (UASs).

OBJECTIVE

We sought to evaluate the efficacy and safety of omalizumab in patients with CIU who remain symptomatic despite concomitant H(1)-antihistamine therapy.

METHODS

This phase II, prospective, double-blind, placebo-controlled, dose-ranging study investigated omalizumab in patients aged 12 to 75 years in the United States and 18 to 75 years in Germany with a UAS over 7 days (UAS7) of 12 or greater despite antihistamine therapy. Patients were randomized 1:1:1:1 to receive a single subcutaneous dose of 75, 300, or 600 mg of omalizumab or placebo added to a stable dose of H(1)-antihistamine. The primary efficacy outcome was change from baseline to week 4 in UAS7. Patients were followed for an additional 12 weeks to monitor safety.

RESULTS

Ninety patients from the United States or Germany were enrolled. Both the 300-mg omalizumab group (-19.9 vs -6.9, P < .001) and the 600-mg omalizumab group (-14.6 vs -6.9, P = .047) showed greater improvement versus the placebo group in UAS7. No meaningful difference was observed for the 75-mg omalizumab group. Similar results were seen for key secondary end points of weekly hive and itch scores. Onset of effect occurred after 1 to 2 weeks. Omalizumab was well tolerated, and the incidence of adverse events was similar across treatment groups.

CONCLUSION

This study demonstrated that a fixed dose of 300 or 600 mg of omalizumab provides rapid and effective treatment of CIU in patients who are symptomatic despite treatment with H(1)-antihistamines.

Omalizumab for pediatric asthma

IMPORTANCE TO THE FIELD

Omalizumab is of proven efficacy in the treatment of severe allergic bronchial asthma and works through inhibiting the activity of IgE and the allergic immune mechanism IgE mediates. It has been demonstrated to be efficacious in children with asthma but is not approved by the FDA for use in children below 12 years of age.

AREAS COVERED IN THIS REVIEW

Omalizumab is a 95% humanized monoclonal antibody that binds to circulating IgE at the same site on the Fc domain as the high-affinity IgE receptor, FcϵRI. This blocks the interaction between IgE and mast cells and basophils, thereby preventing the release of inflammatory mediators that cause allergic signs and symptoms.

WHAT THE READER WILL GAIN

From the review of the literatures and statements from the FDA, Genentec and Novartis, the reader will gain a better appreciation of the value of omalizumab in treatment of severe asthma and the current status of its reported side effects.

TAKE HOME MESSAGE

Omalizumab is of proven efficacy in adults and children with severe asthma and allows a markedly reduced dependence on oral and inhaled corticosteroids and decreased hospitalizations. A potential mechanism of omalizumab's effect on thrombus formation and cardiovascular effect is postulated.

Effectiveness of omalizumab in reducing corticosteroid burden in patients with moderate to severe persistent allergic asthma

BACKGROUND

Asthma guidelines advocate maintaining asthma control while minimizing corticosteroid exposure.

OBJECTIVE

To assess the reduction in corticosteroid burden during long-term treatment and the corresponding impact of this reduction on asthma control, lung function, and inflammation in patients with moderate to severe allergic asthma.

METHODS

We conducted a pooled analysis (N = 1,071) of 2 similarly designed, randomized, double-blind, placebo-controlled omalizumab trials and their extension phases. Each study included a 16-week steroid-stable phase, a 12-week steroid-reduction phase, and a 24-week extension phase. Patients received subcutaneous omalizumab (minimum, 0.016 mg/kg/IU (IgE/mL) every 4 weeks) or placebo every 2 or 4 weeks. Outcomes included change from baseline in inhaled corticosteroid dose, number of oral corticosteroid bursts, and other clinical measures, including asthma exacerbations and change in asthma quality-of-life score (questionnaire), lung function, and eosinophil count.

RESULTS

The median reduction from baseline in inhaled corticosteroid dose (beclomethasone dipropionate equivalent dose) by the completion of the extension phase was greater for the omalizumab group than for the placebo group (-420.0 vs -252.0 μg/d; P < .001). During that time, omalizumab-treated patients required fewer oral corticosteroid bursts overall for treatment of acute exacerbations (mean, 0.2 vs 0.3; relative risk, 0.56; 95% confidence interval, 0.41 to 0.76; P < .001) and demonstrated greater improvements in measures of asthma control.

CONCLUSION

The addition of omalizumab to baseline therapy in patients 12 years or older with moderate to severe persistent allergic asthma resulted in a durable reduction in the overall steroid burden and improvement in other clinical measures of asthma control.

Anti-IgE in the treatment of allergic disorders in pediatrics

PURPOSE OF REVIEW

Neutralization of IgE antibodies is a conceptually new approach for the treatment of allergic diseases. This article reviews current concepts of anti-IgE therapy, with a focus on recent studies that provide insights into underlying mechanisms. Findings of the most recent clinical trials of anti-IgE in the treatment of allergic disorders are discussed.

RECENT FINDINGS

Anti-IgE therapy in allergic asthma has been evaluated mostly in adults, but some studies have documented potential clinical efficacy in children and adolescent patients with moderate to severe uncontrolled asthma despite maximal conventional therapy. Pilot investigations have revealed some promising results regarding the use of anti-IgE in the treatment of other atopic diseases and as an adjunctive therapy in conjunction with allergen-specific immunotherapy. Recent work has provided novel insights into the kinetics of cellular responses to anti-IgE treatment and has identified significant anti-IgE effects on both basophils and dendritic cells, suggesting significant roles for these cells as effectors of IgE-mediated disease.

SUMMARY

Studies of anti-IgE therapy have significantly advanced our understanding of IgE-mediated disease mechanisms and have demonstrated clinical efficacy in the treatment of allergic asthma in adults and children. Further studies are needed in children to evaluate long-term safety and to better define its potential use in allergic diseases other than asthma.

Regulation of Syk kinase and FcRbeta expression in human basophils during treatment with omalizumab

BACKGROUND

In human basophils from different subjects, maximum IgE-mediated histamine release and the level of Syk protein expression correlate well. Recent studies suggest that in some patients treated with omalizumab, the response to stimulation with anti-IgE antibody increases. In unrelated studies there is also evidence that the composition of FcepsilonRI in basophils differs among subjects. This observation raised the possibility that the stoichiometry of FcRbeta/FcepsilonRIalpha is not fixed to a 1:1 ratio and might be modifiable during changes in the basophil's environment.

OBJECTIVE

We sought to determine whether treatment with omalizumab results in increases in Syk expression and anti-IgE-mediated histamine release and disproportionately alters the relative presence of FcRbeta and FcepsilonRIalpha.

METHOD

Syk, FcepsilonRIalpha, and FcRbeta expression was monitored during the treatment of subjects with omalizumab.

RESULTS

Treatment with omalizumab reduced histamine release from peripheral blood leukocytes stimulated with cat allergen in vitro, but histamine release stimulated with anti-IgE antibody increased 2-fold. Expression of Syk increased 1.86-fold. There was no change in the expression of c-Cbl, a signaling element that is sensitive to the presence of IL-3, and no increase in response to formyl-met-leu-phe (tripeptide), a response that also increases in the presence of IL-3. There was a 60% decrease in the FcRbeta/FcepsilonRIalpha ratio in patients treated with omalizumab.

CONCLUSIONS

In the context of previous studies, these studies provide support for a proposal that Syk expression is modulated in vivo through an IgE-dependent mechanism and that the ratio of FcepsilonRI alpha and beta subunits in basophils is influenced by factors extrinsic to the cell.

Roles for the High Affinity IgE Receptor, FcεRI, of Human Basophils in the Pathogenesis and Therapy of Allergic Asthma: Disease Promotion, Protection or Both?

The role of basophils, the rarest of blood granulocytes, in the pathophysiology of allergic asthma is still incompletely understood. Indirect evidence generated over many decades is consistent with a role for basophils in disease promotion. Recent improvements in procedures to purify and analyze very small numbers of human cells have generally supported this view, but have also revealed new complexities. This chapter focuses on our analyses of Fcε R1 function in basophils in the context of understanding and treating human allergic asthma. In long-term studies, we demonstrated that asthmatic subjects have higher circulating numbers of basophils than non-atopic non-asthmatic subjects and that their basophils show higher rates of both basal and anti-IgE or antigen-stimulated histamine release. These results hint at a direct role for basophils in promoting asthma. Supporting this interpretation, the non-releaser phenotype that we linked to the excessive proteolysis of Syk via the ubiquitin/proteasomal pathway is less common in basophils from asthmatic than non-asthmatic donors. The discovery of a basophil-specific pathway regulating Syk levels presents a clear opportunity for therapy. Another route to therapy was revealed by evidence that basophil FcεRI signaling can be downregulated by co-crosslinking the ITAM-containing IgE receptor, FcγRI, to the ITIM-containing IgG receptor, FcγRIIB. Based on this discovery, hybrid co-crosslinking fusion proteins are being engineered as potential therapies targeting basophils. A third distinguishing property of human basophils is their high dependence on IgE binding to stabilize membrane FcεRI. The circulating IgE scavenging mAb, Omalizumab, reduces FcεRI expression in basophils from asthmatics by over 95% and produces a substantial impairment of IL-4, IL-8 and IL-13 production in response to the crosslinking of residual cell surface IgE-FcεRI. A search for small molecule inhibitors that similarly impair high affinity IgE binding to basophils may yield reagents that mimic Omalizumab's therapeutic benefits without the potential for immune side effects. Although studies on allergen and FcεRI-mediated basophil activation all point to a role in promoting disease, a case can also be made for an alternative or additional role of basophil FcεRI in protection against allergic asthma. Human basophils have high affinities for IgE, they upregulate receptor levels over a >100-fold range as circulating IgE levels increase and they have short half-lives in the circulation. Thus, when allergen is absent, basophil FcεRI could serve as scavengers of serum IgE and therefore protectors against mast cell IgE-mediated inflammatory responses. Further studies are clearly needed to determine if FcεR-expressing basophils play pathogenic or protective roles - or both - in human allergic asthma and other IgE-mediated inflammatory disorders.