Pharmacotherapy of severe asthma

A Novel in vivo System to Test Bronchodilators

The incidence and severity of asthma continue to rise worldwide. β-agonists are the most commonly prescribed therapeutic for asthma management but have less efficacy for some subsets of asthmatic patients and there are concerns surrounding the side effects from their long-term persistent use. The demand to develop novel asthma therapeutics highlights the need for a standardized approach to effectively screen and test potential bronchoprotective compounds using relevant in vivo animal models. Here we describe a validated method of testing potential therapeutic compounds for their fast-acting efficacy during the midst of an induced bronchoconstriction in a house dust mite challenged animal model.

Synergistic interaction between PPAR ligands and salbutamol on human bronchial smooth muscle cell proliferation

BACKGROUND AND PURPOSE

An important objective in asthma therapy is to prevent the accelerated growth of airway smooth muscle cells which leads to hyperplasia and bronchial hyperreactivity. We investigated the effect of combination of salbutamol and PPARγ agonists on growth factor-stimulated human bronchial smooth muscle cell (BSMC) proliferation.

EXPERIMENTAL APPROACH

Synergism was quantified by the combination index-isobologram method. Assays used here included analyses of growth inhibition, cell viability, DNA fragmentation, gene transcription, cell cycle and protein expression.

KEY RESULTS

The PPARγ gene was highly expressed in BSMC and the protein was identified in cell nuclei. Single-agent salbutamol or PPARγ agonists prevented growth factor-induced human BSMC proliferation within a micromolar range of concentrations through their specific receptor subtypes. Sub-micromolar levels of combined salbutamol-PPARγ agonist inhibited growth by 50% at concentrations from ∼2 to 12-fold lower than those required for each drug alone, without induction of apoptosis or necrosis. Combination treatments also promoted cell cycle arrest at the G1/S transition phase and inhibition of ERK phosphorylation.

CONCLUSIONS AND IMPLICATIONS

The synergistic interaction between PPARγ agonists and β(2) -adrenoceptor agonists on airway smooth muscle cell proliferation highlights the anti-remodelling potential of this combination in chronic lung diseases.

Difficult childhood asthma: management and future

Diagnosis and management of severe asthma implies the definition of different entities, that is, difficult asthma and refractory severe asthma, but also the different phenotypes included in the term refractory severe asthma. A complete evaluation by a physician expert in asthma is necessary, adapted for each child. Identification of mechanisms involved in different phenotypes in refractory severe asthma may improve the therapeutic approach. The quality of care and monitoring of children with severe asthma is as important as the prescription drug, and is also crucial for differentiating between severe asthma and difficult asthma, whereby expertise is required.

Hypothalamic-pituitary-adrenal axis function in patients with complex regional pain syndrome type 1

An exaggerated inflammatory process is considered an important pathophysiological feature of complex regional pain syndrome type 1 (CRPS-1). The hypothalamic-pituitary-adrenal (HPA) axis serves as a negative feedback mechanism for inflammatory processes. The present study examined the HPA axis function in patients with CRPS-1 by a determination of cortisol concentrations in saliva. Three sets of saliva samples were sequentially collected from 24 patients with CRPS-1 during medication (on-Med), 72 h after stopping medication (off-Med) and 8h after the oral administration of 1mg dexamethasone. One set of saliva samples was collected from healthy controls. The cortisol awakening response (CAR) and diurnal cortisol decline (DCD) were used as indices for HPA axis function. Cortisol levels during the post-awakening period in patients were increased following withdrawal of medications. The CAR during the off-Med condition was disappeared after administration of dexamethasone. Among the examined CRPS-related numerical variables, the frequency of spontaneous pain attacks showed relationships with the indices of HPA axis function. After classifying the patients into two subgroups, we observed that the CAR and DCD in patient who had a relatively high frequency of spontaneous pain attacks (subgroup 5 ≤) were lower and less steep than those in patient who had a relatively low frequency of spontaneous pain attacks (subgroup 0-4) for the on- and off-Med conditions. The CAR and DCD in subgroup 5 ≤ during their off-Med condition were comparable to those in controls. These results suggest that the increase in frequency of spontaneous pain attacks is associated with a reduced CAR and flattened DCD in patients CRPS-1.

Two-start design within a Sephadex inflammatory model--a means to generate reliable ED50 data whilst significantly reducing the number of animals used

Pulmonary inflammation disorders represent a major healthcare burden, and novel anti-inflammatory agents are critically needed for the treatment of patients unresponsive to current therapies. In vivo animal models play a key role in the preclinical assessment of novel anti-inflammatory compounds. The implementation of streamlined in vivo experimental designs that are time-and cost-efficient, while keeping animal usage low, is a key consideration for drug optimization programs. The Sephadex rat model of pulmonary inflammation captures many pathophysiologic characteristics of clinical asthma and allergy, such as eosinophilic infiltration andinterstitial edema. Using the in vivo Sephadex model, we compared two different study designs that were implemented to screen and select two novel candidate drugs for a drug discovery project. The traditional one-start design, which utilizes few dose-testing groups with many animals per group, was used to select the first candidate drug. Due to tight timelines, the selection process for the second candidate drug had to be optimized, leading to the development of the novel two-start design, an approach whereby dose ranges are optimized in two experimental phases. Here we show that both study designs were comparable in their generation of robust median effective dose values for selected candidate drugs, as represented by similar confidence interval ratios. However, implementation of the two-start design resulted in approximately 50% fewer animals and 50% less time taken to assess the efficacy of an equal number of compounds compared with the one-start design. These results demonstrate that the two-start design is a more efficient experimental approach, and its widespread implementation in drug optimization programs will impact upon the selection process for candidate drugs with regards to time, cost, and animal usage.

Therapy with omalizumab for patients with severe allergic asthma improves asthma control and reduces overall healthcare costs

BACKGROUND

Patients with asthma who have persistent symptoms despite treatment with inhaled steroids and long-acting beta agonists are considered to have severe asthma. Omalizumab is a monoclonal antibody directed against IgE, which is used as an add-on treatment for patients who have severe persistent allergic asthma.

AIMS

The aim of this study was to assess the clinical benefit and healthcare utilisation of patients who responded to omalizumab therapy and to establish an overall cost implication.

METHODS

This was an observational retrospective cohort study designed to investigate the effect of omalizumab on exacerbations of asthma before and after 6 months of treatment in Irish patients.

RESULTS

Centres who had treated patients with severe allergic asthma for the 6 months prior and post omalizumab treatment were audited with a standardised assessment tool. Sixty-three (32 male) patients were studied. In the 6 months prior to omalizumab 41 of 63 (66%) had been hospitalised, and this fell to 15 of 63 (24%), p < 0.0001 in the 6 months after treatment was started. Hospital admissions reduced from 2.4 ± 0.41 to 0.8 ± 0.37 and the mean number of bed days occupied was reduced from 16.6 ± 2.94 to 5.3 ± 2.57 days, p < 0.001. The number of oral corticosteroid doses used fell from 3.1 ± 0.27 to 1.2 ± 0.17, p < 0.001. The overall cost saving per omalizumab responder patients for 6 months was <euro>834.

CONCLUSIONS

Six months therapy with omalizumab reduced the number of bed days, the number of hospitalisations and the use of oral corticosteroids compared to the 6 months prior to commencement. Despite the cost of the additional therapy there were overall savings in health costs.

A soluble form of the high affinity IgE receptor, Fc-epsilon-RI, circulates in human serum

Soluble IgE receptors are potential in vivo modulators of IgE-mediated immune responses and are thus important for our basic understanding of allergic responses. We here characterize a novel soluble version of the IgE-binding alpha-chain of Fc-epsilon-RI (sFcεRI), the high affinity receptor for IgE. sFcεRI immunoprecipitates as a protein of ∼40 kDa and contains an intact IgE-binding site. In human serum, sFcεRI is found as a soluble free IgE receptor as well as a complex with IgE. Using a newly established ELISA, we show that serum sFcεRI levels correlate with serum IgE in patients with elevated IgE. We also show that serum of individuals with normal IgE levels can be found to contain high levels of sFcεRI. After IgE-antigen-mediated crosslinking of surface FcεRI, we detect sFcεRI in the exosome-depleted, soluble fraction of cell culture supernatants. We further show that sFcεRI can block binding of IgE to FcεRI expressed at the cell surface. In summary, we here describe the alpha-chain of FcεRI as a circulating soluble IgE receptor isoform in human serum.