Total serum IgE levels in a large cohort of patients with severe or difficult-to-treat asthma

Anti-IgE and other antibody targets in asthma

Asthma is a heterogeneous disorder of unknown etiology that manifests as recurrent episodes of coughing, wheezing, and breathlessness. These symptoms are often debilitating and exacerbations usually are unexpected, resulting in work or school absences, limitations in activity, reduced quality of life, and personal and economic hardships. Over the past several decades, a great deal has been learned about asthma pathophysiology, and currently available therapies have revolutionized asthma treatment. However, asthma remains a global public health problem, and the hope is that newer therapies targeting specific biological mediators of asthma, particularly antibody-mediated therapies, offer exciting new modes to the control of this disease. We will review some of these therapies, with the majority of attention devoted to anti-IgE therapy which has been approved for treatment of adult and childhood asthma by the US Food and Drug Administration (FDA) since 2003.

Immunoglobulin E blockade in the treatment of asthma

Patients with moderate-to-severe asthma often have persistent symptoms despite aggressive pharmacotherapy, enthusiastic patient compliance, and proper technique in using delivery devices. Persistent symptoms have detrimental effects on patients' quality of life and result in a tremendous financial burden because of an increased utilization of health care resources. Guidelines from the National Asthma Education and Prevention Program list symptom prevention, near-normal lung function, and participation in activities (e.g., school, work) as goals of successful asthma therapy. The development of pharmacologic and biologic therapies that target different aspects of airway inflammation will help patients with persistent asthma symptoms achieve these goals. Immunoglobulin E (IgE) is increasingly recognized as a key component of asthma pathophysiology and contributes to both the early- and late-phase inflammatory cascade of the airways by inhibiting allergen-induced activation of mast cells. Both epidemiologic and clinical evidence support the use of IgE blockade for asthma treatment. Omalizumab is currently the only IgE-targeted therapy approved by the United States Food and Drug Administration for asthma treatment. The drug improves symptoms, reduces exacerbations, and improves quality of life in certain patient populations.

Immunoglobulin E-mediated airway inflammation is active in most patients with asthma

PURPOSE

To review the role of immunoglobulin E (IgE)-mediated inflammation in the pathogenesis of asthma, limitations of standard therapies, and IgE as a logical target for therapy with omalizumab aimed at attaining asthma symptom control.

DATA SOURCES

Review of worldwide scientific literature on the role of IgE-mediated inflammation in patients with asthma, supplemented with a clinical case study.

CONCLUSIONS

Clinical trials point to an important role for IgE blocker therapy as an add-on to current therapy to reduce exacerbations and corticosteroid use and to improve quality of life in patients with moderate-to-severe asthma. Omalizumab, a monoclonal antibody that binds IgE, has been shown to be an effective, well-tolerated treatment in these patients.

IMPLICATIONS FOR PRACTICE

A significant number of patients with moderate-to-severe asthma do not achieve asthma symptom control, despite adhering to current guidelines-based standards of therapy, including the use of inhaled corticosteroids, beta-agonists, and leukotriene modifiers. None of these therapies directly addresses IgE-mediated inflammation. Therefore, patients with persistent symptoms of moderate-to-severe asthma should be evaluated and considered for therapy with the IgE blocker omalizumab.

[Allergy and refractory asthma: new etiological and treatment pathways]

Severe asthma is often refractory to standard treatments and presents real problems of management. It necessitates rigorous clinical procedures to identify the aggravating factors. Allergic factors probably play an important role but are often ignored; atopy is more often associated with mild or moderate asthma. The prevalence of severe refractory asthma is not known with any precision, in view of the lack of a consensus definition. Few studies have examined the role of allergic factors. From a pathophysiologic perspective, genetic factors are probably responsible for greater severity, and allergic response plays an important role in some severe asthma phenotypes. From an environmental perspective, some airborne allergens are associated with the refractory character of the disease. Molds such as Alternaria are, for example, implicated in the onset of asthma attacks, as are some occupational exposure. Better knowledge of the pathophysiology of refractory asthma and its allergic dimensions have made it possible to use new treatment agents, such as omalizumab. New treatment targets are being discovered and evaluated in this domain.

Anti-IgE antibodies for the treatment of IgE-mediated allergic diseases

The pharmacological purposes of the anti-IgE therapy are to neutralize IgE and to inhibit its production to attenuate type I hypersensitivity reactions. The therapy is based on humanized IgG1 antibodies that bind to free IgE and to membrane-bound IgE on B cells, but not to IgE bound by the high-affinity IgE.Fc receptors on basophils and mast cells or by the low-affinity IgE.Fc receptors on B cells. After nearly 20 years since inception, therapeutic anti-IgE antibodies (anti-IgE) have been studied in about 30 Phase II and III clinical trials in many allergy indications, and a lead antibody, omalizumab, has been approved for treating patients (12 years and older) with moderate-to-severe allergic asthma. Anti-IgE has confirmed the roles of IgE in the pathogenesis of asthma and helped define the concept "allergic asthma" in clinical practice. It has been shown to be safe and efficacious in treating pediatric allergic asthma and treating allergic rhinitis and is being investigated for treating peanut allergy, atopic dermatitis, latex allergy, and others. It has potential for use to combine with specific and rush immunotherapy for increased safety and efficacy. Anti-IgE thus appears to provide a prophylactic and therapeutic option for moderate to severe cases of many allergic diseases and conditions in which IgE plays a significant role. This chapter reviews the evolution of the anti-IgE concept and the clinical studies of anti-IgE on various disease indications, and presents a comprehensive analysis on the multiple intricate immunoregulatory pharmacological effects of anti-IgE. Finally, it reviews other approaches that target IgE or IgE-expressing B cells.

Association between IgE levels and asthma severity among African American, Mexican, and Puerto Rican patients with asthma

BACKGROUND

High levels of IgE are associated with asthma. Whether higher levels of IgE are associated with more severe asthma is still unclear.

OBJECTIVE

To determine whether IgE is associated with asthma severity among Latino and African American subjects with asthma.

METHODS

We assessed lung function and asthma severity among African American, Mexican, and Puerto Rican patients with asthma with high IgE levels (> or =100 IU/mL; n = 492) and compared these values to those of patients with asthma with low IgE levels (<100 IU/mL; n = 247). We also examined IgE as a continuous variable among these groups.

RESULTS

Patients with asthma with high IgE had a lower mean FEV(1) (87.6 +/- 17.1, percent of predicted) than patients with asthma with low IgE (91.5 +/- 17.0; P = .031). Regardless of race and ethnicity, baseline FEV(1), forced expiratory flow, and FEV(1)/forced vital capacity were lower among subjects with high IgE than among subjects with low IgE (P = .031, P < .0001, P = .0001, respectively). In addition, 54.7% of patients with asthma with high IgE had been previously hospitalized, compared with 44.1% of patients with asthma with low IgE (odds ratio, 1.33; 95% CI, 1.04-1.71).

CONCLUSION

Higher IgE is associated with lower baseline lung function and more severe asthma among these populations.

CLINICAL IMPLICATIONS

Among patients with asthma from 3 ethnically distinct groups, total IgE levels are inversely correlated with baseline lung function and asthma severity.

Demographic and clinical characteristics of children and adolescents with severe or difficult-to-treat asthma

BACKGROUND

Young patients with severe or difficult-to-treat asthma are an understudied population.

OBJECTIVE

To assess age-associated and gender-associated differences in children and adolescents in the observational study, The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens.

METHODS

Cross-sectional baseline data for patients greater than or equal to 6 years and less than or equal to 17 years (n = 1261) were stratified by age group (6-8, 9-11, 12-14, and 15-17 years). The chi(2) test for categorical variables and analysis of variance for continuous variables were used to identify differences among age groups, stratified by gender.

RESULTS

Most patients had moderate (55%) or severe (41%) asthma by physician assessment. Of those using greater than or equal to 3 long-term controllers (62%), 53% of children (6-11 years) and 44% of adolescents (12-17 years) reported an oral corticosteroid burst and 25% and 19%, respectively, had an emergency department visit in the previous 3 months; 10% and 15%, respectively, reported past intubation. In females, weight for age ranged between the 67th and 70th percentiles; height for age was between the 42nd and 54th percentiles (P < .01 among age groups). Lung function was lower in adolescents than children: prebronchodilator percent predicted forced expiratory volume in 1 second (FEV(1))/forced vital capacity was 0.92 (6-8 years) and 0.83 (15-17 years), P less than .05, in males; and 0.94 (6-8 years) and 0.87 (15-17 years), P less than .05, in females.

CONCLUSIONS

Children and adolescents demonstrated high rates of health care use and loss of lung function, despite using multiple long-term controllers.

CLINICAL IMPLICATIONS

Asthma treatments that prevent loss of lung function and reduce health care resource use are needed in young patients with severe or difficult-to-treat asthma.

Severe asthma in adults: what are the important questions?

The term severe refractory asthma (SRA) in adults applies to patients who remain difficult to control despite extensive re-evaluation of diagnosis and management following an observational period of at least 6 months by a specialist. Factors that influence asthma control should be recognized and adequately addressed prior to confirming the diagnosis of SRA. This report presents statements according to the literature defining SRA in order address the important questions. Phenotyping SRA will improve our understanding of mechanisms, natural history, and prognosis. Female gender, obesity, and smoking are associated with SRA. Atopy is less frequent in SRA, but occupational sensitizers are common inducers of new-onset SRA. Viruses contribute to severe exacerbations and can persist in the airways for long periods. Inflammatory cells are in the airways of the majority of patients with SRA and persist despite steroid therapy. The T(H)2 immune process alone is inadequate to explain SRA. Reduced responsiveness to corticosteroids is common, and epithelial cell and smooth muscle abnormalities are found, contributing to airway narrowing. Large and small airway wall thickening is observed, but parenchymal abnormalities may influence airway limitation. Inhaled corticosteroids and bronchodilators are the mainstay of treatment, but patients with SRA remain uncontrolled, indicating a need for new therapies.

Does anti-IgE therapy help in asthma? Efficacy and controversies

Omalizumab, a humanized monoclonal antibody against IgE, is clinically efficacious when it neutralizes almost all free IgE and reduces IgE receptors on basophils and mast cells. Asthmatic subjects on inhaled corticosteroids who are treated with omalizumab as an add-on therapy experience only modest benefits in symptoms and perhaps in quality of life, but the most significant effects are reductions in airway inflammation and in exacerbation rate. Airway obstruction and hyperresponsiveness do not change significantly. Although the magnitude of the beneficial effects is small, they are observed even in the most severe cases, particularly the reduction in exacerbation rate. The safety profile of omalizumab is very encouraging, although phase IV studies are ongoing to clarify the incidence of neoplasias. Because of its cost, omalizumab therapy may be most cost-effective in patients with severe and refractory asthma, particularly those with frequent exacerbations requiring hospital care. Further clinical studies are now evaluating the best place for omalizumab in the algorithm of asthma management.

Features of severe asthma in school-age children: Atopy and increased exhaled nitric oxide

BACKGROUND

Children with severe asthma have persistent symptoms despite treatment with inhaled corticosteroids (ICSs). The differentiating features of severe asthma in children are poorly defined.

OBJECTIVE

To identify features of severe versus mild-to-moderate asthma in school-age children using noninvasive assessments of lung function, atopy, and airway inflammation.

METHODS

A total of 75 children (median age, 10 years) with asthma underwent baseline characterization including spirometry and lung volume testing, methacholine bronchoprovocation, allergy evaluation, and offline measurement of exhaled nitric oxide (F(ENO)). Twenty-eight were followed longitudinally over 6 months. Participants were assigned to the severe asthma subgroup if they required high-dose ICS plus 2 or more minor criteria.

RESULTS

Children with severe versus mild-to-moderate asthma had more symptoms, greater airway obstruction, more gas trapping, and increased bronchial responsiveness to methacholine. Subjects with severe asthma also had higher concentrations of F(ENO) and significantly greater sensitization to aeroallergens. With long-term study, both the reduction in FEV(1) and increase in F(ENO) persisted in the severe versus mild-to-moderate group. Furthermore, despite adjustments in ICS doses, the frequency of exacerbations was significantly higher in subjects with severe (83%) versus mild-to-moderate asthma (43%).

CONCLUSION

Severe asthma in childhood is characterized by poor symptom control despite high-dose ICS treatment and can be differentiated from mild-to-moderate asthma by measurement of lung function and F(ENO).

CLINICAL IMPLICATIONS

Clinicians should suspect severe asthma in children with poor response to ICS, airway obstruction, and high F(ENO).

The level of IgE produced by a B cell is regulated by norepinephrine in a p38 MAPK- and CD23-dependent manner

Although the causes of asthma vary, the severity of the disease correlates with the level of IgE produced. In this study we show that mice produced less IgE when they were depleted of the neurotransmitter norepinephrine (NE) before the administration of Ag. The suppression was prevented when a beta2-adrenergic receptor (beta2AR)-selective agonist was administered, suggesting that NE stimulated the beta2AR to regulate the level of an IgE response in vivo. Although the cell targeted by NE to produce this effect in vivo is unknown, we show in vitro that the level of IgE increased on a per cell basis without an effect on class switch recombination when NE stimulated the beta2AR on a B cell directly. The beta2AR-induced increase in IgE depended on p38 MAPK but not protein kinase A activation, was due to an increased rate of mature IgE mRNA transcription, and was lost when beta2AR-deficient B cells were used. Also, CD23 transcription was increased in a p38 MAPK-dependent manner and resulted in an increased level of soluble CD23 (sCD23). The beta2AR-induced increase in sCD23 was associated with IgE up-regulation and possibly interacted with CD21/CD19. Using B cells from respective knockout mice, data showed that the beta2AR-induced increase in IgE depended on B cell expression of CD23, CD21, and CD19. These findings suggest that at least one mechanism by which endogenous B cell activity in vivo is regulated by NE involves stimulation of the beta2AR on the B cell alone to increase the level of IgE produced in a p38 MAPK- and sCD23-dependent manner.

Gender differences in IgE-mediated allergic asthma in the epidemiology and natural history of asthma: Outcomes and Treatment Regimens (TENOR) study

BACKGROUND

The TENOR study consists of a large cohort of subjects with severe or difficult-to-treat asthma. The objective of this analysis was to evaluate demographic and clinical characteristics of subjects 12 years of age or older with immunoglobulin E (IgE)-mediated allergic asthma (skin test positive with an IgE level = 30 to =700 IU/mL), and specifically, to assess gender differences in this cohort.

METHODS

A total of 4,756 subjects were enrolled by 283 US study sites between January and October 2001. Of those subjects 12 years or older at baseline with an IgE measure and who were skin tested (n = 2,843), 1,783 (63%) were skin test positive and had an IgE level between = 30 to = 700 IU/mL.

RESULTS

Compared to males, females reported significantly greater healthcare utilization (steroid bursts in previous 3 months: 50% vs 42%, p < 0.001; unscheduled office visits in previous 3 months: 50% vs 36%, p < 0.0001; missed 1+ days of work/school in previous 2 weeks: 14% vs 10%, p < 0.01). Females also reported significantly more asthma control problems and lower asthma-related quality of life (4.6 +/- 1.3 vs 5.2 +/- 1.2; p < 0.0001); the difference was clinically meaningful. Asthma triggers and allergic comorbidities, such as allergic rhinitis and atopic dermatitis, were more common in female subjects. Despite their overall worse health outcomes, female subjects demonstrated better lung function, had similar treatment patterns, and showed no differences in physician-assessed asthma severity when compared with males.

CONCLUSIONS

The reasons for these gender differences in subjects with IgE-mediated allergic asthma are complex, but results from this analysis suggest that detailed evaluations of asthma patients, including symptom-related questions and asthma-related healthcare utilization, are needed to accurately assess asthma severity and control.