Omalizumab: Practical considerations regarding the risk of anaphylaxis

A risk of serious anaphylatic reactions to asthma biologics: a pharmacovigilance study based on a global real-world database

Asthma is a chronic inflammatory condition that affects the lung airways. Chronic use of oral glucocorticoids in patients with severe asthma is associated with several adverse events (AEs). Biologics (omalizumab, benralizumab, mepolizumab, reslizumab, and dupilumab) have been developed as alternative therapies for the treatment of asthma. In this study, we aimed to evaluate the risk of anaphylactic reactions associated with these five biologics based on a large global database. We utilized individual case reports from the Uppsala Monitoring Center from January 1968 to December 29, 2019. A disproportionality analysis was performed over all drugs and monoclonal antibodies. Anaphylactic reactions were defined according to the "anaphylactic reaction" of the standardized MedDRA queries. Contrary to dupilumab, omalizumab, benralizumab, and mepolizumab demonstrated positive signals related to anaphylactic reactions over all drugs and monoclonal antibodies. Reslizumab, which represented only 315 cases of all AEs, requires more reports to determine its association with anaphylactic reactions. More anaphylactic reactions have been identified than are known, and most cases (96.2%) are reported to be serious. Our findings indicate that omalizumab, benralizumab, and mepolizumab for asthma treatment are associated with a high risk of anaphylactic reactions; thus, more careful monitoring in the post-administration period is recommended.

Gene Therapy for Immunoglobulin E, Complement-Mediated, and Eosinophilic Disorders

Immunoglobulin E, complement, and eosinophils play an important role in host defense, but dysfunction of each of these components can lead to a variety of human disorders. In this review, we summarize how investigators have adapted gene therapy and antisense technology to modulate immunoglobulin E, complement, and/or eosinophil levels to treat these disorders.

Drug delivery targets and strategies to address mast cell diseases

INTRODUCTION

Current and developing mast cell therapeutics are reliant on small molecule drugs and biologics, but few are truly selective for mast cells. Most have cellular and disease-specific limitations that require innovation to overcome longstanding challenges to selectively targeting and modulating mast cell behavior. This review is designed to serve as a frame of reference for new approaches that utilize nanotechnology or combine different drugs to increase mast cell selectivity and therapeutic efficacy.

AREAS COVERED

Mast cell diseases include allergy and related conditions as well as malignancies. Here, we discuss the targets of existing and developing therapies used to treat these disease pathologies, classifying them into cell surface, intracellular, and extracellular categories. For each target discussed, we discuss drugs that are either the current standard of care, under development, or have indications for potential use. Finally, we discuss how novel technologies and tools can be used to take existing therapeutics to a new level of selectivity and potency against mast cells.

EXPERT OPINION

There are many broadly and very few selectively targeted therapeutics for mast cells in allergy and malignant disease. Combining existing targeting strategies with technology like nanoparticles will provide novel platforms to treat mast cell disease more selectively.

Allergy to Omalizumab: Lessons from a Reaction to the Coronavirus 2019 Vaccine

Omalizumab can cause hypersensitivity reactions. We herein report the first case of an 18-year-old woman with refractory cough-predominant asthma that correlated with allergic reactions caused by omalizumab and the coronavirus disease 2019 (COVID-19) vaccine. The patient developed angioedema after taking omalizumab. She had previously experienced intense coughing immediately after receiving a COVID-19 vaccine. A skin prick test was positive for polysorbate 20, which was probably the cause of the allergic reactions to omalizumab and the COVID-19 vaccine. Clinicians should check for an allergic reaction, irrespective of its intensity, triggered by polysorbate and be careful when prescribing biologics to patients in order to avoid allergic reactions.

Efficacy and Safety of Omalizumab Treatment Over a 16-Year Follow-Up: When a Clinical Trial Meets Real-Life

Purpose

Treatment of severe asthma has made great strides thanks to rapid progress in understanding immune response and inflammatory pathways. This led to the advent of the first biologic for severe allergic asthma (SAA), omalizumab. Although the long-term efficacy and safety of omalizumab has been confirmed, increasingly longer follow-up data can further reinforce this evidence and potentially provide new ones, for example on any loss of efficacy or the appearance of unexpected side effects. This study reports omalizumab treatment-related outcomes after 16 years of follow-up.

Patients and Methods

In this real-life retrospective study, an extension of a previous 9-year follow-up study on patients initially recruited in a clinical trial, we enrolled 8 adult patients with SAA followed-up from November 2005 to December 2021. Study subjects were selected based on omalizumab eligibility criteria.

Results

Exacerbation rate significantly decreased from 3.6 ± 2.1 events in year before index date to 0.1 ± 0.4 after 32 weeks of treatment (p < 0.0001). Mean annual number of mild-to-moderate exacerbations at 16 years was 0.88 compared with 1.8 in the year before the index date and 1.1 at 32 weeks. No hospitalizations were documented during the 16-year follow-up compared to 0.3 hospitalizations/patient in the year before the index date. Respiratory function also progressively and significantly improved. Regarding patient-reported outcomes (PROs), The AQLQ and ACT significantly improved from baseline throughout the follow-up, particularly up to 9 years of follow-up. During the study, an overall reduction in doses of asthma medications was observed, with a significant OCS-sparing effect.

Conclusion

Our study, the longest clinical follow-up on patients treated with anti-IgE, confirms and amplifies the results of the studies carried out so far, as they are maintained over a very long interval of time without drops in efficacy without any type of side effect.

Home-based treatment of biologics for asthma: who, what, where, when and why

INTRODUCTION

The advent of biologic therapies for severe asthma has profoundly changed the management of this pathology. The introduction of home administration is therefore an important innovation to optimize the patients' management, even if there are many aspects that need to be clarified and pointed out.

AREAS COVERED

This review summarizes the path that led to the possibility of self-administration of biologics, and what the pandemic has changed in the management of these patients.

EXPERT OPINION

The growing understanding of asthma phenotypes and endotypes is enabling the careful selection of patients suitable for biologics. In this context, the availability of reliable and simple self-injection devices is important in implementing self-administration. The transition to self-injection is also possible thanks to the high safety profile of biologics. With attention, most patients may potentially be suitable for self-administration. The transition process from hospital to home administration can therefore be carried out correctly by clinicians with adequate expertise in the field of severe asthma and biologic therapies, with the support of other health professionals, pharmacists, and general practitioners. Home administration is probably the best way to guarantee high adherence and high-level satisfaction of patients, even in the long term.

Emerging Challenges and Innovations in Surfactant-mediated Stabilization of Biologic Formulations

Biologics may be subjected to various destabilizing conditions during manufacturing, transportation, storage, and use. Therefore, biologics must be appropriately formulated to meet their desired quality target product profiles. In the formulations of protein-based biologics, one critical component is surfactant. Polysorbate 80 and Polysorbate 20 remain the most commonly used surfactants. Surfactants can stabilize proteins through different mechanisms and help the proteins withstand destabilization stresses. However, the challenges associated with surfactants, for instance, impurities, degradation, and potential triggering of adverse immune responses, have been encountered. Therefore, there are continued efforts to develop novel surfactants to overcome these challenges associated with traditional surfactants. Meanwhile, surfactants have also found their use in formulations of newer and novel modalities, namely, antibody-drug conjugates, bispecific antibodies, and adeno-associated viruses (AAV). This review provides an updated in-depth discussion of surfactants in the above-mentioned areas, namely mechanism of action of surfactants, a critical review of challenges with surfactants and current mitigation approaches, and emerging technologies to develop novel surfactants. In addition, gaps, current mitigations, and future directions have been presented to trigger further discussion and research to facilitate the use and development of novel surfactants.

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.

Self-administration of omalizumab: why not? A literature review and expert opinion

Introduction: Omalizumab is used to treat severe uncontrolled allergic asthma and chronic spontaneous urticaria (CSU), and is approved for self-administration in prefilled syringes. It is thus important to understand the advantages, critical issues, and indications for home administration.Areas covered: The present review summarizes the available evidence on home administration of omalizumab in asthma and CSU to illustrate the advantages derived from self-administration of patients in this setting.Expert opinion: The available data suggest that patients can safely administer biologics at home with suitable training, and that home administration is time saving and cost-effective. The majority of patients with severe asthma or CSU treated with omalizumab are likely to be suitable candidates for self-administration, which can be proposed to anyone that the clinician deems suitable. In addition to clinicians, pharmacists can also play a key role in managing patients who are prescribed home administration. A practical flow chart is proposed on selection of patients and their management during home administration. Self-administration of biologics can be considered as a valid alternative to traditional injections in a clinical setting, and the evidence has shown that no major issues need to be overcome in terms of safety or efficacy.

Anaphylaxis to three humanized antibodies for severe asthma: a case study

Background

Omalizumab, mepolizumab, benralizumab, and dupilumab are the currently available biologics used to treat asthma in Japan. Anaphylaxis following treatment with mepolizumab or benralizumab is considered rare.

Case presentation

We report the case of a 35-year-old woman with severe asthma, who experienced anaphylaxis following the administration of benralizumab, mepolizumab, and omalizumab, separately. The therapy with biologics was chosen to avoid the repeated use of systemic corticosteroids for asthma exacerbations. The mechanisms underlying anaphylaxis caused by these three biologics remain unclear. The patient’s asthma symptoms and lung function improved after treatment with bronchial thermoplasty.

Conclusions

To our knowledge, this is the first report of an asthmatic patient developing anaphylaxis after commencement of benralizumab, mepolizumab, and omalizumab therapy. These three biologics should be administered carefully, and patients should be monitored for anaphylaxis.

Intersection of biology and therapeutics: type 2 targeted therapeutics for adult asthma

Asthma is a disease of reversible airflow obstruction characterised clinically by wheezing, shortness of breath, and coughing. Increases in airway type 2 cytokine activity, including interleukin-4 (IL-4), IL-5, and IL-13, are now established biological mechanisms in asthma. Inhaled corticosteroids have been the foundation for asthma treatment, in a large part because they decrease airway type 2 inflammation. However, inhaled or systemic corticosteroids are ineffective treatments in many patients with asthma and few treatment options exist for patients with steroid resistant asthma. Although mechanisms for corticosteroid refractory asthma are likely to be numerous, the development of a new class of biologic agents that target airway type 2 inflammation has provided a new model for treating some patients with corticosteroid refractory asthma. The objective of this Therapeutic paper is to summarise the new type 2 therapeutics, with an emphasis on the biological rationale and clinical efficacy of this new class of asthma therapeutics.

The mechanistic and functional profile of the therapeutic anti-IgE antibody ligelizumab differs from omalizumab

Targeting of immunoglobulin E (IgE) represents an interesting approach for the treatment of allergic disorders. A high-affinity monoclonal anti-IgE antibody, ligelizumab, has recently been developed to overcome some of the limitations associated with the clinical use of the therapeutic anti-IgE antibody, omalizumab. Here, we determine the molecular binding profile and functional modes-of-action of ligelizumab. We solve the crystal structure of ligelizumab bound to IgE, and report epitope differences between ligelizumab and omalizumab that contribute to their qualitatively distinct IgE-receptor inhibition profiles. While ligelizumab shows superior inhibition of IgE binding to FcεRI, basophil activation, IgE production by B cells and passive systemic anaphylaxis in an in vivo mouse model, ligelizumab is less potent in inhibiting IgE:CD23 interactions than omalizumab. Our data thus provide a structural and mechanistic foundation for understanding the efficient suppression of FcεRI-dependent allergic reactions by ligelizumab in vitro as well as in vivo.

Immunoglobulin E (IgE) plays a central role in allergic responses, yet therapeutic targeting of IgE with antibodies such as omalizumab is met with various limitations. Here the authors characterize the molecular properties and crystal structure of a new anti-IgE antibody, ligelizumab, for mechanistic insights related to its enhanced suppression activity.

Are Injection Site Reactions in Monoclonal Antibody Therapies Caused by Polysorbate Excipient Degradants?

Injection site reactions (ISRs) and other adverse side effects are commonly observed during therapy with biologics. These hypersensitivity-related side effects can vary from simple rash to life-threatening anaphylactic reaction and may be linked to the immunogenicity of the drug including formation of antidrug antibodies. Reactions can also occur as a consequence of excipients in the product. We report the case of a patient who developed erythematous ISRs to both commercial PCSK9i formulations and had to go off therapy even though efficacy was not impacted. Skin testing showed that the patient was reacting to the polysorbates. Polysorbates are added to stabilize the biotherapeutic. Polysorbates can also activate complement and lead to a range of acute hypersensitivity and systemic immunostimulation reactions. Oxidative degradation products can function as haptens by reacting with proteins at the injection site. Reactive degradation products may even form adducts with the biologic itself, creating a potential neoantigen. Further research is needed to understand the fundamental causes of ISRs. It is critical that only the highest quality raw material is used, and proper storage conditions are employed to minimize degradation of polysorbates in the product. Although complete elimination of ISRs is unlikely, all efforts must be made to minimize them.

Real-world safety and efficacy of omalizumab in patients with severe allergic asthma: A long-term post-marketing study in Japan

BACKGROUND

Omalizumab (anti-IgE monoclonal antibody) is an approved add-on therapy for Japanese patients with severe allergic asthma. As directed by the Ministry of Health, Labor and Welfare Japan, a post-marketing surveillance (PMS) study on omalizumab was conducted between 2009 and 2017.

METHODS

The PMS observed safety and efficacy of omalizumab in patients treated with open-label omalizumab for 52 weeks (with optional 2-year extension period). Primary safety outcomes included incidence and severity of adverse events (AEs) and adverse drug reactions (ADRs). Primary efficacy outcomes included physician-assessed global evaluation of treatment effectiveness (GETE). Asthma-exacerbation-related events including requirement for additional systemic steroid therapy, hospitalization, emergency room visits, unscheduled doctor visits, and absenteeism were also evaluated.

RESULTS

Of 3893 patients registered, 3620 (age [mean ± SD] 59.3 ± 16.11 years) were evaluated for 52 weeks; 44.12% were aged ≥65 years and 64.45% were women. Overall, 32.24% reported AEs and 15.30% reported serious AEs. ADRs were seen in 292 (8.07%) patients. GETE results showed that the majority of patients experienced clinical improvements (58.29% at 16 weeks and 62.40% at 52 weeks). Nearly half of all patients (47.96%) were free from asthma exacerbations after therapy. Omalizumab also reduced all events related to asthma exacerbations. No specific ADRs were observed in the elderly population.

CONCLUSIONS

This post-marketing study confirmed the clinically meaningful benefits of omalizumab in a majority of patients from Japan, and showed safety and efficacy in a real-life clinical setting to be consistent with previous reports.

Role of omalizumab in insulin hypersensitivity: a case report and review of the literature

BACKGROUND

Insulin allergy is a rare yet severe side effect of exogenous insulin use. Management typically involves use of alternative antihyperglycaemic agents, symptom control with antihistamines, use of different insulin formulations, and induction of tolerance with incremental doses of insulin. This treatment regimen is not always successful, and the use of omalizumab, an anti-IgE monoclonal antibody, has been used to induce tolerance to insulin.

CASE REPORT

G.M. is a 62-year-old man with Type 2 diabetes mellitus. His condition was not optimized on oral agents, and insulin therapy was required. G.M. had anaphylaxis to insulin NPH, and subsequent skin-prick testing was positive to insulin aspart, insulin NPH, insulin glulisine, insulin detemir, regular insulin, insulin glargine 100 units/ml and insulin glargine 300 units/ml. He received incremental doses of several insulin formulations; however, he experienced diffuse urticaria preventing optimal glycaemic control. Three successful cases have been described in the literature of omalizumab inducing tolerance to exogenous insulin; therefore, G.M. was started on omalizumab. He subsequently tolerated treatment doses of insulin glulisine and insulin detemir with no allergic reactions and with improvement in glycaemic control.

CONCLUSION

To our knowledge, this is the first described case of allergy to insulin glargine 300 units/ml and reiterates the potential use of omalizumab in insulin allergy. Further research is warranted to determine if omalizumab should be considered standard of care in difficult-to-treat insulin hypersensitivity.

Nanomedicine safety in preclinical and clinical development: focus on idiosyncratic injection/infusion reactions

Injection/infusion reactions to nanopharmaceuticals (and particulate drug carriers) are idiosyncratic and well documented. The molecular basis of nanoparticle-mediated injection reactions is debatable, with two hypotheses as front-runners. The first is complement-activation-related 'pseudoallergy', where a causal role for nanoparticle-mediated complement activation in injection/infusion reactions is considered. However, the second hypothesis (the rapid phagocytic response hypothesis) states a transitional link from robust clearance of nanoparticles (NPs) from the blood by strategically placed responsive macrophages to adverse hemodynamic and cardiopulmonary reactions, regardless of complement activation. Here, I critically examine and discuss these hypotheses. Current experimentally derived evidence appears to be more in support of the rapid phagocytic response hypothesis than of the 'pseudoallergy' hypothesis.

From IgE to Omalizumab

IgE is the least abundant Ig isotype, yet it plays a critical role in allergic reactions and host protection from helminth infection. Although IgE was discovered 50 years ago, the ultimate evidence for its role in human allergic diseases was obtained by the efficacy of anti-IgE therapy in many clinical trials on asthma and other allergic diseases. Beginning from the discovery of IgE 50 y ago, followed by studies of IgE receptors and activation mechanisms, this review provides a historic perspective of allergy research that has led to the development of anti-IgE therapy and other strategies targeting IgE and its receptors. Current IgE studies toward future precision medicine are also reviewed.

Risk and safety requirements for diagnostic and therapeutic procedures in allergology: World Allergy Organization Statement

One of the major concerns in the practice of allergy is related to the safety of procedures for the diagnosis and treatment of allergic disease. Management (diagnosis and treatment) of hypersensitivity disorders involves often intentional exposure to potentially allergenic substances (during skin testing), deliberate induction in the office of allergic symptoms to offending compounds (provocation tests) or intentional application of potentially dangerous substances (allergy vaccine) to sensitized patients. These situations may be associated with a significant risk of unwanted, excessive or even dangerous reactions, which in many instances cannot be completely avoided. However, adverse reactions can be minimized or even avoided if a physician is fully aware of potential risk and is prepared to appropriately handle the situation. Information on the risk of diagnostic and therapeutic procedures in allergic diseases has been accumulated in the medical literature for decades; however, except for allergen specific immunotherapy, it has never been presented in a systematic fashion. Up to now no single document addressed the risk of the most commonly used medical procedures in the allergy office nor attempted to present general requirements necessary to assure the safety of these procedures. Following review of available literature a group of allergy experts within the World Allergy Organization (WAO), representing various continents and areas of allergy expertise, presents this report on risk associated with diagnostic and therapeutic procedures in allergology and proposes a consensus on safety requirements for performing procedures in allergy offices. Optimal safety measures including appropriate location, type and required time of supervision, availability of safety equipment, access to specialized emergency services, etc. for various procedures have been recommended. This document should be useful for allergists with already established practices and experience as well as to other specialists taking care of patients with allergies.

Anti-hIgE gene therapy of peanut-induced anaphylaxis in a humanized murine model of peanut allergy

BACKGROUND

Peanuts are the most common food to provoke fatal or near-fatal anaphylactic reactions. Treatment with an anti-hIgE mAb is efficacious but requires frequent parenteral administration.

OBJECTIVE

Based on the knowledge that peanut allergy is mediated by peanut-specific IgE, we hypothesized that a single administration of an adeno-associated virus (AAV) gene transfer vector encoding for anti-hIgE would protect against repeated peanut exposure in the host with peanut allergy.

METHODS

We developed a novel humanized murine model of peanut allergy that recapitulates the human anaphylactic response to peanuts in NOD-scid IL2Rgamma^null mice transferred with blood mononuclear cells from donors with peanut allergy and then sensitized with peanut extract. As therapy, we constructed an adeno-associated rh.10 serotype vector coding for a full-length, high-affinity, anti-hIgE antibody derived from the Fab fragment of the anti-hIgE mAb omalizumab (AAVrh.10anti-hIgE). In the reconstituted mice peanut-specific IgE was induced by peanut sensitization and hypersensitivity, and reactions were provoked by feeding peanuts to mice with symptoms similar to those of human subjects with peanut allergy.

RESULTS

A single administration of AAVrh.10anti-hIgE vector expressed persistent levels of anti-hIgE. The anti-hIgE vector, administered either before sensitization or after peanut sensitization and manifestation of the peanut-induced phenotype, blocked IgE-mediated alterations in peanut-induced histamine release, anaphylaxis scores, locomotor activity, and free IgE levels and protected animals from death caused by anaphylaxis.

CONCLUSION

If this degree of persistent efficacy translates to human subjects, AAVrh.10anti-hIgE could be an effective 1-time preventative therapy for peanut allergy and possibly other severe, IgE-mediated allergies.

Position statement for the use of omalizumab in the management of chronic spontaneous urticaria in Indian patients

Chronic spontaneous urticaria (CSU) affects 1% of the world population and also their quality of life, and 50% of these patients are refractory to H1-antihistamines. Omalizumab is a humanized monoclonal anti-IgE antibody that binds with free IgE antibodies and reduces the circulating levels of free IgE. This reduction in free IgE prevents mast-cell degranulation. The EAACI/GA2LEN/EDF/WAO guidelines recommend omalizumab as the third-line of therapy as an add-on to antihistamines. The recommended dose of omalizumab is 300 mg, 4 weekly in the management of CSU refractory to standard of care with H1-antihistamines in adults and adolescents ≥12 years of age. In some patients, a dose of 150 mg may be acceptable. Omalizumab has a good safety profile. However, due to the biologic nature of the drug, all patients administered omalizumab must be observed for 2 h after administration for anaphylactoid reactions. There have been no studies on the effect of impaired renal or hepatic function on the pharmacokinetics of omalizumab. While no particular dose adjustment is recommended, omalizumab should be administered with caution in these patients.

Omalizumab-A Review

Omalizumab is a recombinant, humanized, monoclonal antibody against human immunoglobulin E (IgE). The US FDA has approved this molecule for chronic urticaria.

New strategies with anti-IgE in allergic diseases

IgE has long been known as a therapeutic target for allergic disease, but the difficulty has been in selecting agents that don't trigger cross linkage of IgE when bound to its high affinity receptor (FceR1) on mast cells and basophils. By "designing" a monoclonal antibody (mAb) which targets that part of IgE that binds to that binds to the a-chain of FceR1, the allergic cascade can be effectively interrupted and diseases such as asthma greatly improved, providing a substantial part of their phenotype engages IgE. Clinical trials and real life studies confirm this. Beyond asthma, a whole range of other diseases dependent upon IgE initiation and triggering are being identified. These diseases are now being explored as being amenable to anti-IgE therapy some of which are comorbidities of asthma and others not. The advent of an even more potent anti-IgE mAb - QGE031 - is creating further opportunities for anti-IgE therapy to improve the lives of so many people with IgE-related diseases.

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.

Immunogenicity of therapeutic proteins: influence of aggregation

The elicitation of anti-drug antibodies (ADA) against biotherapeutics can have detrimental effects on drug safety, efficacy, and pharmacokinetics. The immunogenicity of biotherapeutics is, therefore, an important issue. There is evidence that protein aggregation can result in enhanced immunogenicity; however, the precise immunological and biochemical mechanisms responsible are poorly defined. In the context of biotherapeutic drug development and safety assessment, understanding the mechanisms underlying aggregate immunogenicity is of considerable interest. This review provides an overview of the phenomenon of protein aggregation, the production of unwanted aggregates during bioprocessing, and how the immune response to aggregated protein differs from that provoked by non-aggregated protein. Of particular interest is the nature of the interaction of aggregates with the immune system and how subsequent ADA responses are induced. Pathways considered here include 'classical' activation of the immune system involving antigen presenting cells and, alternatively, the breakdown of B-cell tolerance. Additionally, methods available to screen for aggregation and immunogenicity will be described. With an increased understanding of aggregation-enhanced immune responses, it may be possible to develop improved manufacturing and screening processes to avoid, or at least reduce, the problems associated with ADA.

Can anti-IgE therapy prevent airway remodeling in allergic asthma?

Airway remodeling is a central feature of asthma. It is exemplified by thickening of the lamina reticularis and structural changes to the epithelium, submucosa, smooth muscle, and vasculature of the airway wall. Airway remodeling may result from persistent airway inflammation. Immunoglobulin E (IgE) is an important mediator of allergic reactions and has a central role in airway inflammation and asthma-related symptoms. Anti-IgE therapies (such as omalizumab) have the potential to block an early step in the allergic cascade and therefore have the potential to reduce airway remodeling. The reduction in free IgE levels following anti-IgE therapy leads to reductions in high-affinity IgE receptor (FcεRI) expression on mast cells, basophils, and dendritic cells. This combined effect results in attenuation of several markers of inflammation, including peripheral and bronchial tissue eosinophilia and levels of granulocyte macrophage colony-stimulating factor, interleukin (IL)-2, IL-4, IL-5, and IL-13. Considering the previously demonstrated anti-inflammatory effects of anti-IgE therapy, along with results from a small study showing continued benefit after discontinuation of long-term treatment, a larger study to assess its effect on markers of airway remodeling is underway.