Overview of the pharmacogenetics of asthma treatment

Allele-specific micro-RNA-mediated regulation of ADAM33 in childhood allergic asthma

BACKGROUND AND OBJECTIVE

A disintegrin and metalloprotease 33 (ADAM33) is associated with asthma susceptibility, and its genetic variations impact susceptibility and disease severity. However, the mechanisms remain unclear. This study aimed to investigate ADAM33 single nucleotide polymorphisms (SNPs) in childhood asthma susceptibility and explore their regulatory mechanisms.

METHODS

Eleven selected SNPs in ADAM33 were genotyped and identified the association with asthma susceptibility. In the validation cohort, we measured plasma sADAM33 levels and compared them with disease severity among children with different SNP genotypes. Computational predictions identified miRNAs targeting the SNP, and the impact of the SNP on miRNA regulation was confirmed using a dual luciferase reporter system. Finally, we validated the regulatory role of miRNAs on ADAM33 expression using an in vitro model with upregulated ADAM33 expression.

RESULTS

Only rs3918400 was associated with asthma susceptibility. In the validation cohort, children with allergic asthma exhibited higher plasma sADAM33 levels. Among asthmatic children, those with the rs3918400 CT/TT genotype had higher sADAM33 levels, poorer asthma control, more severe airway hyper-responsiveness, lower FEV1% and higher dust mite-specific IgE activity compared to those with the CC genotype. miR-3928-5p bound strongly to the rs3918400 C allele and effectively reduced ADAM33 protein expression in CC genotype cells. However, the binding affinity of miR-3928-5p to the T allele was weaker, resulting in diminished negative regulation of protein expression.

CONCLUSION

The rs3918400 SNP affects the negative regulation of ADAM33 by miR-3928-5p, potentially participating in a complex interplay of processes related to childhood asthma susceptibility.

Pharmacogenomics and Pediatric Asthmatic Medications

Asthma is a respiratory condition often stemming from childhood, characterized by difficulty breathing and/or chest tightness. Current treatment options for both adults and children include beta-2 agonists, inhaled corticosteroids (ICS), and leukotriene modifiers (LTM). Despite recommendations by the Global Initiative for Asthma, a substantial number of patients are unresponsive to treatment and unable to control symptoms. Pharmacogenomics have increasingly become the front line of precision medicine, especially with the recent use of candidate gene and genome- wide association studies (GWAS). Screening patients preemptively could likely decrease adverse events and therapeutic failure. However, research in asthma, specifically in pediatrics, has been low. Although numerous adult trials have evaluated the impact of pharmacogenomics and treatment response, the lack of evidence in children has hindered progress towards clinical application. This review aims to discuss the impact of genetic variability and response to asthmatic medications in the pediatric population.

Methods for Experimental Allergen Immunotherapy: Subcutaneous and Sublingual Desensitization in Mouse Models of Allergic Asthma

Allergic asthma is characterized by airway hyperresponsiveness, remodeling, and reversible airway obstruction. This is associated with an eosinophilic inflammation of the airways, caused by inhaled allergens such as house dust mite or grass pollen. The inhaled allergens trigger a type-2 inflammatory response with the involvement of innate lymphoid cells (ILC2) and Th2 cells, resulting in high immunoglobulin E (IgE) antibody production by B cells and mucus production by airway epithelial cells. As a consequence of the IgE production, subsequent allergen reexposure results in a classic allergic response with distinct early and late phases, both resulting in bronchoconstriction and shortness of breath. Allergen-specific immunotherapy (AIT) is the only treatment that is capable of modifying the immunological process underlying allergic responses including allergic asthma. Both subcutaneous AIT (SCIT) as well as sublingual AIT (SLIT) have shown clinical efficacy in long-term suppression of the allergic response. Although AIT treatments are very successful for rhinitis, application in asthma is hampered by variable efficacy, long duration of treatment, and risk of severe side effects. A more profound understanding of the mechanisms by which AIT induces tolerance to allergens in sensitized individuals is needed to be able to improve its efficacy. Mouse models have been very valuable in preclinical research for characterizing the mechanisms of desensitization in AIT and evaluating novel approaches to improve its efficacy. Here, we present a rapid and reproducible mouse model for allergen-specific immunotherapy. In this model, mice are sensitized with two injections of allergen adsorbed to aluminum hydroxide, followed by subcutaneous injections (SCIT) or sublingual administrations (SLIT) of allergen extracts as an immunotherapy treatment. Finally, mice are challenged by intranasal allergen administrations. We will also describe the protocols as well as the most important readout parameters for the measurements of invasive lung function, serum immunoglobulin levels, isolation of bronchoalveolar lavage fluid (BALF), and preparation of cytospin slides. Moreover, we describe how to perform ex vivo restimulation of lung single-cell suspensions with allergens, flow cytometry for identification of relevant immune cell populations, and ELISAs and Luminex assays for assessment of the cytokine concentrations in BALF and lung tissue.

Gene polymorphisms in VEGFA and COL2A1 are associated with response to inhaled corticosteroids in children with asthma

Aim: The purpose of this study was to investigate the involvement of single-nucleotide polymorphisms in VEGFA, TBX21 and COL2A1 in the response to inhaled corticosteroids in asthmatic children. Subjects & methods: Children with mild-to-moderate asthma were enrolled in the study. The SEQUENOM MassARRAY method was used to sequence 27 SNP genotypes. By ranking the data from smallest to largest, we could infer whether the change in distribution of forced expiratory volume in one second/forced vital capcacity (FEV₁/FVC) and fractional exhaled nitric oxide differed between genotype groups. Results: VEGFA rs3025039 T allele carriers had a smaller change in FEV₁ than CC carriers (p = 0.040), and in COL2A1 rs3809324, the frequency of T allele carriers was lower than that of GG carriers (p = 0.048). rs3025039 was also associated with changes in FEV₁/FVC (p = 0.016). Conclusion: VEGFA and COL2A1 polymorphisms are significantly associated with the response to inhaled corticosteroids in asthmatic children.

Asthma and Corticosteroid Responses in Childhood and Adult Asthma

Corticosteroids are the most effective treatment for asthma; inhaled corticosteroids (ICSs) are the first-line treatment for children and adults with persistent symptoms. ICSs are associated with significant improvements in lung function. The anti-inflammatory effects of corticosteroids are mediated by both genomic and nongenomic factors. Variation in the response to corticosteroids has been observed. Patient characteristics, biomarkers, and genetic features may be used to predict response to ICSs. The existence of multiple mechanisms underlying glucocorticoid insensitivity raises the possibility that this might indeed reflect different diseases with a common phenotype.

Developmental Pharmacogenetics of SLCO2B1 on Montelukast Pharmacokinetics in Chinese Children

Background

Montelukast, a potent oral selective leukotriene-receptor antagonist, inhibits the action of cysteinyl-leukotriene in patients with asthma. Although pharmacokinetic studies of montelukast have been reported in Caucasian adults and children, and showed large inter-individual variability on pharmacokinetics, none of these studies has been explored in Chinese children. Given the potential inter-ethnic difference, the purpose of the present study was to evaluate the effects of developmental factors and pharmacogenetics of CYP2C8 and SLCO2B1 on montelukast clearance in Chinese pediatric patients.

Methods

After the administration of montelukast, blood samples were collected from children and plasma concentrations were determined using an adapted micro high-performance liquid chromatography coupled with the fluorescence detection (HPLC-FLD) method. A previously published pharmacokinetic model was validated using the opportunistic pharmacokinetic samples, and individual patient’s clearance was calculated using the validated model. Population pharmacokinetic analysis was performed using a nonlinear mixed-effects model approach (NONMEM V 7.2.0) and variants of CYP2C8 and SLCO2B1 were genotyped.

Results

Fifty patients (age range: 0.7–10.0 years) with asthma were enrolled in this study. The clearance of montelukast was significantly higher in children with the SLCO2B1 c.935GA and c.935AA genotypes compared with that of children with the SLCO2B1 c.935GG genotype (0.94 ± 0.26 versus 0.77 ± 0.21, p = 0.020). The patient’s weight was also found to be significantly corrected with montelukast clearance (p <0.0001).

Conclusion

The developmental pharmacology of montelukast in Chinese children was evaluated. Weight and SLCO2B1 genotype were found to have independent significant impacts on the clearance of montelukast.

Association of genetic variants with level of asthma control in the Arab population

Background

Rates of asthma in Jordan have been doubled in the past decade, but this increased prevalence was not met with improved asthma control protocols. The aim of the present study was to assess whether there was any significant association between the level of asthma control and certain single-nucleotide polymorphisms (SNPs) in five genes: (ADRB2; rs1042713 and rs1042714), (CRHR1; rs1876828, rs242939, and rs242941), (STIP1; rs2236647), (ADH5, rs1154400), and (ARG1; rs2781659). These SNPs were selected based on their involvement in enzymes and receptors that are related to asthma pathways and subsequent response to medication and based on a high degree of linkage disequilibrium.

Patients and methods

A cross-sectional genetic association study was conducted from June 2016 to June 2017 in the two major hospitals in Jordan. The present study involved sampling from adult asthmatic patients of Arab descent who were selected from two phenotypic groups, ie, controlled and uncontrolled asthma. The blood samples and medical data were collected from the participants. DNA samples were extracted, quantified, and genotyped according to standard operating procedure. Allelic and haplotypic analyses were performed using the Haploview^®.

Results

A total of 245 Arab asthmatic patients were enrolled in this study. Genotyping analysis revealed that the two SNPs (rs1042713 and rs1042714) in ADRB2 gene, along with their related haplotypes, were nominally significantly associated with asthma control in the Jordanian population. The A-allele of rs1042713 and the C-allele of rs1042714 were more common in the uncontrolled asthma group than in the controlled asthma group (P=0.048 and P=0.017, respectively).

Conclusion

This was the first study that identified the nominal significant association between the level of asthma control and genetic variants in ADRB2 gene in Arab population. Further studies in other Arab region with larger sample size are recommended to confirm the relationship.

Review on Pharmacogenetics and Pharmacogenomics Applied to the Study of Asthma

Nearly one-half of asthmatic patients do not respond to the most common therapies. Evidence suggests that genetic factors may be involved in the heterogeneity in therapeutic response and adverse events to asthma therapies. We focus on the three major classes of asthma medication: β-adrenergic receptor agonist, inhaled corticosteroids, and leukotriene modifiers. Pharmacogenetics and pharmacogenomics studies have identified several candidate genes associated with drug response.In this chapter, the main pharmacogenetic and pharmacogenomic studies in addition to the future perspectives in personalized medicine will be reviewed. The ideal treatment of asthma would be a tailored approach to health care in which adverse effects are minimized and the therapeutic benefit for an individual asthmatic is maximized leading to a more cost-effective care.

Asthma-specific cognitions, self-focused attention, and fear of negative evaluation in adolescents and young adults diagnosed with childhood-onset asthma

The present study examined the impact of asthma-specific thought intrusion (TI) and thought suppression (TS) on two cognitive-affective variables (self-focused attention and fear of negative evaluation) among adolescents and young adults (AYAs) diagnosed with childhood-onset asthma. Participants were 290 AYAs who completed assessment questionnaires and participated in a written exercise electronically. Asthma-TI and TS were reported by participants following participation in a writing assignment. Asthma-TI was associated with increased private, public, and social anxiety self-focused attention, and greater fear of negative evaluation. Interestingly, asthma-TS was not associated with these same outcome variables. Findings suggest illness-specific cognitions are associated with cognitive-affective variables and it may be important to assess for illness-specific intrusive thoughts following asthma-focused medical appointments. Additionally, findings suggest the importance of assessing asthma-TI and TS separately in order to better understand thoughts about health and psychological functioning.

Effects of genetic factors to inhaled corticosteroid response in children with asthma: a literature review

Numerous studies have examined the association between pharmacogenetic effects and the response to inhaled corticosteroids (ICS) in patients with asthma. In fact, several single nucleotide polymorphisms of a number of candidate genes have been identified that might influence the clinical response to ICS in children with asthma. Their direct or indirect effects depend on their role in the inflammatory process in asthma or the anti-inflammatory action of corticosteroids, respectively. Among the genes identified, variants in T-box 21 (TBX21) and Fc fragment of IgE receptor II (FCER2) contribute indirectly to the variability in the response to ICS by altering the inflammatory mechanisms in asthma, while other genes such as corticotropin releasing hormone receptor 1 (CRHR1), nuclear receptor subfamily 3 group C member 1 (NR3C1), stress induced phosphoprotein 1 (STIP1), dual specificity phosphatase 1 (DUSP1), glucocorticoid induced 1 (GLCCI1), histone deacetylase 1 (HDAC), ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3), and vascular endothelial growth factors (VEGF) directly affect this variability through the anti-inflammatory mechanisms of ICS. The results to date indicate various potential genetic factors associated with the response to ICS, which could be utilized to predict the individual therapeutic response of children with asthma to ICS. Clinical trials are underway and their results are greatly anticipated. Further pharmacogenetic studies are needed to fully understand the effects of genetic variation on the response to ICS in children with asthma.

Subcutaneous and Sublingual Immunotherapy in a Mouse Model of Allergic Asthma

Allergic asthma, caused by inhaled allergens such as house dust mite or grass pollen, is characterized by reversible airway obstruction, associated with an eosinophilic inflammation of the airways, as well as airway hyper responsiveness and remodeling. The inhaled allergens trigger a type-2 inflammatory response with involvement of innate lymphoid cells (ILC2) and Th2 cells, resulting in high production of immunoglobulin E (IgE) antibodies. Consequently, renewed allergen exposure results in a classic allergic response with a distinct early and late phase, both resulting in bronchoconstriction and shortness of breath. Allergen specific immunotherapy (AIT) is the only treatment that is capable of modifying the immunological process underlying allergic responses including allergic asthma and both subcutaneous AIT (SCIT) as well as sublingual AIT (SLIT) have proven clinical efficacy in long term suppression of the allergic response. Although these treatments are very successful for rhinitis, application of AIT in asthma is hampered by variable efficacy, long duration of treatment, and the risk of severe side-effects. A more profound understanding of the mechanisms by which AIT achieves tolerance to allergens in sensitized individuals is needed to improve its efficacy. Mouse models have been very valuable as a preclinical model to characterize the mechanisms of desensitization in AIT and to evaluate novel approaches for improved efficacy. Here, we present a rapid and reproducible mouse model for allergen-specific immunotherapy. In this model, mice are sensitized with two injections of allergen absorbed to aluminum hydroxide to induce allergic sensitization, followed by subcutaneous injections (SCIT) or sublingual administrations (SLIT) of the allergen as immunotherapy treatment. Finally, mice are challenged by three intranasal allergen administrations. We will describe the protocols as well as the most important read-out parameters including measurement of invasive lung function measurements, serum immunoglobulin levels, isolation of broncho-alveolar lavage fluid (BALF), and preparation of cytospins. Moreover, we describe how to restimulate lung single cell suspensions, perform flow cytometry measurements to identify populations of relevant immune cells, and perform ELISAs and Luminex assays to measure the cytokine concentrations in BALF and lung tissue.

Salbutamol in paediatrics: pharmacology, prescribing and controversies

Salbutamol has become a key drug in respiratory medicine since it was first developed by Sir David Jack et al in 1968, 5000 years after the β agonist ephedrine was first used in its raw form, as the Ma Huang herb in Chinese medicine to treat asthma. It is one of the most commonly encountered medicines in paediatric practice and the authors have found that an understanding of its pharmacology in clinical practice is incredibly helpful. In this article, we discuss its pharmacology and pharmacodynamics, practical prescribing points and some unresolved issues surrounding its use, which should serve to provide an essential working knowledge for the busy paediatrician.

The Therapeutic Potential of Targeting Cytokine Alarmins to Treat Allergic Airway Inflammation

Asthma is a heterogeneous disorder that results in recurrent attacks of breathlessness, coughing, and wheezing that affects millions of people worldwide. Although the precise causes of asthma are unclear, studies suggest that a combination of genetic predisposition and environmental exposure to various allergens and pathogens contribute to its development. Currently, the most common treatment to control asthma is a dual combination of β2-adrenergic receptor agonists and corticosteroids. However, studies have shown that some patients do not respond well to these medications, while others experience significant side effects. It is reported that the majority of asthmas are associated with T helper type 2 (TH2) responses. In these patients, allergen challenge initiates the influx of TH2 cells in the airways leading to an increased production of TH2-associated cytokines and the promotion of allergy-induced asthma. Therefore, biologics that target this pathway may provide an alternative method to treat the allergic airway inflammation associated with asthma. As of now, only two biologics (omalizumab and mepolizumab), which target immunoglobulin E and interleukin-5, respectively, are FDA-approved and being prescribed to asthmatics. However, recent studies have reported that targeting other components of the TH2 response also show great promise. In this review, we will briefly describe the immunologic mechanisms underlying allergic asthma. Furthermore, we will discuss the current therapeutic strategies used to treat asthma including their limitations. Finally, we will highlight the benefits of using biologics to treat asthma-associated allergic airway inflammation with an emphasis on the potential of targeting cytokine alarmins, especially thymic stromal lymphopoietin.

The links between chronic obstructive pulmonary disease and comorbid depressive symptoms: role of IL-2 and IFN-γ

Depression is highly prevalent in COPD patients, and both diseases are believed to be associated with inflammation. The aim of this study was to elucidate the role of the immune system alterations in pathogenesis of depression in COPD patients. Blood was collected from patients diagnosed with chronic obstructive pulmonary disease and comorbid depressive symptoms [COPD + DS, (N = 13)], from individuals with either COPD (N = 16) or recurrent depressive disorder (rDD) alone (N = 15), and from healthy controls (N = 19). Surface phenotype expression of T regulatory and T effector cells was analyzed with a flow cytometry, and IL-2, IL-6, IL-8, IFN-γ, IL-17, and neopterin were detected with ELISA. We demonstrated that COPD, depression, and COPD with comorbid depression are associated with increased IL-6 levels when compared with healthy controls 42.2 ± 1.87, 40.9 ± 2.12, 41.7 ± 1.31, and 33.2 ± 1.23 pg/ml, respectively (p < 0.05). A significant increase in neopterin levels was observed both in rDD and COPD patients when compared with controls (15.69 ± 0.095, 13.98 ± 0.887 vs. 9.22 ± 0.466 nmol/l, p < 0.001 and p < 0.05, respectively). Concentrations of IFN-γ were significantly increased in COPD + DS patients when compared with controls (24.3 ± 1.49 and 17.8 ± 0.70 pg/ml, respectively, p < 0.05). IL-2 levels were highest in COPD + DS (3.20 ± 0.389 pg/ml) and differed significantly when this group was compared with controls (2.20 ± 0.184 pg/ml), p ≤ 0.05). In this study, we demonstrated for the first time that depressive symptoms in COPD patients may be related to inflammatory state as confirmed by increased levels of IL-6 both in COPD and depression and also in COPD with comorbid depressive symptoms, despite the fact that the patients were treated with anti-inflammatory drugs and/or antidepressants. We also identified IFN-γ and IL-2 as putative inflammatory agents associated with depressive symptoms in COPD patients. Prospective studies will need to confirm whether measuring IL-2 and IFN-γ can identify COPD patients at risk of depression. These findings suggest that T helper cell 1-derived cellular immune activation may play significant role in developing depressive symptoms in COPD patients.

Pharmacogenomics of long-acting β2-agonists

INTRODUCTION

Long-acting β2-agonists are an effective class of drugs, when combined with inhaled corticosteroids, for reducing symptoms and exacerbations in patients with asthma that is not adequately controlled by inhaled corticosteroids alone. However, because this class of drugs has been associated with severe adverse events, including hospitalization and death in small numbers of patients, efforts to identify a pharmacogenetic profile for patients at risk has been diligently investigated.

AREAS COVERED

The PubMed search engine of the National Library of Medicine was used to identify English-language and non-English language articles published from 1947 to March 2015 pertinent to asthma, pharmacogenomics, and long-acting β2-agonists. Keywords and topics included: asthma, asthma control, long-acting β2-agonists, salmeterol, formoterol, pharmacogenetics, and pharmacogenomics. This strategy was also used for the Cochrane Library Database and CINAHL. Reference types were randomized controlled trials, reviews, and editorials. Additional publications were culled from reference lists. The publications were reviewed by the authors and those most relevant were used to support the topics covered in this review.

EXPERT OPINION

Children, who carry the ADRB2 Arg16Arg genotype, may be at greater risk than adults for severe adverse events. Rare ADRB2 variants appear to provide better clues for identifying the at-risk population of asthmatics.

Influence of ethnicity on response to asthma drugs

INTRODUCTION

Understanding variability in the response to asthma medications is essential to ensure appropriate prescribing. Given that there are increased asthma treatment failures observed in ethnic minorities receiving asthma therapeutics, it is fundamental to understand the factors related to ethnicity that can modify the response to asthma therapy.

AREAS COVERED

Race/ethnicity is an important determinant of drug response and therefore contributes to interindividual variability. It is generally recognized that its effects on drug response are determined by both genetic and environmental factors to a varying extent, depending on the ethnic groups and probe drugs studied. Also, adherence to therapy can influence pharmacological response to asthma therapeutics.

EXPERT OPINION

Health-care professionals might never use the treatment in their patients irrespective of their ethnicity and thus inadvertently increase ethnic health inequality. However, our understanding of whether and/or how ethnicity influences pharmacological response to asthma therapeutics is still very scarce. A holistic, integrative systems biology approach that combines large-scale molecular profiling traits (e.g., transcriptomic, proteomic, metabolomic traits) and genetic variants could help to personalize the treatment of asthmatic patients regardless of race/ethnicity.

Beta2 adrenergic receptor (ADRβ2) haplotype pair (2/4) is associated with severe asthma

Background

β2 adrenergic receptor (ADRβ2) polymorphisms including ADRβ2+46G>A have been reported to cause adverse outcomes in mild asthmatics. The extent to which ADRβ2 polymorphisms and in particular their haplotypes contribute to severe asthma is unknown.

Objective

To determine the association of ADRβ2 polymorphisms and haplotypes with asthma severity.

Methods

Caucasians (n = 2979) were genotyped for 11 ADRβ2 polymorphisms. The cohort (mean age 39.6, 60% female) included 2296 non-asthmatics, 386 mild asthmatics, 172 moderate asthmatics and 125 severe asthmatics. Haplotype frequency and haplotype pair for each subject was determined using the PHASE algorithm.

Results

The three asthmatic cohorts were comparable in age and gender but were distinguishable from each other in terms of symptoms, spirometry, medication use and health care utilisation (p <0.001). None of the polymorphisms showed a genotypic or allelic association with asthma diagnosis or severity. Nine haplotypes were identified and no association was found with asthma diagnosis or severity per se. Haplotype pair 2/4 was associated with asthma severity (Trend Test, OR 1.42, p = 0.0008) but not with asthma per se. Prevalence of haplotype pair 2/2 appeared to decrease with asthma severity (Trend Test, OR 0.78, p = 0.067). Two new haplotypes were identified, occurring exclusively in asthmatics at a frequency of ≥ 1%. In addition, a positive association between carriage of ADRβ2 +523*C and increased risk of atopy was discovered.

Conclusions

ADRβ2 haplotype pair 2/4 is associated with severe asthma and is consistent with findings of poor bronchodilator response in mild asthmatics who are also haplotype 2/4.

Lung disease modifier genes in cystic fibrosis

Cystic fibrosis (CF) is recognized as a single gene disorder. However, a considerable diversity in its clinical phenotype has been documented since the description of the disease. Identification of additional gene alleles, so called "modifier genes" that directly influence the phenotype of CF disease became a challenge in the late '90ies, not only for the insight it provides into the CF pathophysiology, but also for the development of new potential therapeutic targets. One of the most studied phenotype has been the lung disease severity as lung dysfunction is the major cause of morbidity and mortality in CF. This review details the results of two main genetic approaches that have mainly been explored so far: (1) an "a priori" approach, i.e. the candidate gene approach; (2) a "without a priori" approach, analyzing the whole genome by linkage and genome-wide association studies (GWAS), or the whole exome by exome sequencing.

Integrative systems biology approaches in asthma pharmacogenomics

In order to improve therapeutic outcomes, there is a tremendous need to identify patients who are likely to respond to a given asthma treatment. Pharmacogenomic studies have explained a portion of the variability in drug response and provided an increasing list of candidate genes and SNPs. However, as phenotypic variation arises from a network of complex interactions among genetic and environmental factors, rather than individual genes or SNPs, a multidisciplinary, systems-level approach is required in order to understand the inter-relationships among these factors. Systems biology, which seeks to capture interactions between genetic factors and other variables, offers a promising approach to improved therapeutic outcomes in asthma. This aritcle will review and update progress in the pharmacogenomics of asthma and then discuss the application of systems biology approaches to asthma pharmacogenomics.

Can certain genotypes predispose to poor asthma control in children? A pharmacogenetic study of 9 candidate genes in children with difficult asthma

Objective

We tested the hypothesis that patients with difficult asthma have an increased frequency of certain genotypes that predispose them to asthma exacerbations and poor asthma control.

Methods

A total of 180 Caucasian children with confirmed asthma diagnosis were selected from two phenotypic groups; difficult (n = 112) versus mild/moderate asthma (n = 68) groups. All patients were screened for 19 polymorphisms in 9 candidate genes to evaluate their association with difficult asthma.

Key Results

The results indicated that LTA4H A-9188>G, TNFα G-308>A and IL-4Rα A1727>G polymorphisms were significantly associated with the development of difficult asthma in paediatric patients (p<0.001, p = 0.019 and p = 0.037, respectively). Haplotype analysis also revealed two haplotypes (ATA haplotype of IL-4Rα A1199>C, IL-4Rα T1570>C and IL-4Rα A1727>G and CA haplotype of TNFα C-863>A and TNFα G-308>A polymorphisms) which were significantly associated with difficult asthma in children (p = 0.04 and p = 0.018, respectively).

Conclusions and Clinical Relevance

The study revealed multiple SNPs and haplotypes in LTA4H, TNFα and IL4-Rα genes which constitute risk factors for the development of difficult asthma in children. Of particular interest is the LTA4H A-9188>G polymorphism which has been reported, for the first time, to have strong association with severe asthma in children. Our results suggest that screening for patients with this genetic marker could help characterise the heterogeneity of responses to leukotriene-modifying medications and, hence, facilitate targeting these therapies to the subset of patients who are most likely to gain benefit.

Pharmacotherapy for exercise-induced asthma: allowing normal levels of activity and sport

Exercise-induced bronchoconstriction (EIB) is experienced by the majority of an estimated 300 million individuals who have asthma, a condition that affects all ages and is increasing globally. Respiratory water loss with dehydration of the airways causing mediator release and airway narrowing is considered the cause of EIB, the severity of which will be increased if the inhaled air is cold or polluted. Adequate control of asthma is essential to minimize or prevent EIB and permit normal levels of physical activity and sport. This is important because exercise is a necessary component of daily living, assists in obtaining and maintaining a healthy body and has been demonstrated to benefit asthmatics. Inhaled glucocorticosteroids and inhaled β(2)-adrenoceptor agonists (IβA) are the pharmacological agents of choice to manage asthma and minimize EIB, assisted when necessary, by other drugs including leukotriene receptor antagonists and chromones. Tolerance from daily use of IβA is of concern and more flexible drug therapy needs to be considered. Optimal use of inhalers to deliver drugs effectively requires closer attention. Pharmacogenetics may hold the key to future drug therapy.

Systems pharmacology, pharmacogenetics, and clinical trial design in network medicine

The rapidly growing disciplines of systems biology and network science are now poised to meet the fields of clinical medicine and pharmacology. Principles of systems pharmacology can be applied to drug design and, ultimately, testing in human clinical trials. Rather than focusing exclusively on single drug targets, systems pharmacology examines the holistic response of a phenotype-dependent pathway or pathways to drug perturbation. Knowledge of individual pharmacogenetic profiles further modulates the responses to these drug perturbations, moving the field toward more individualized ('personalized') drug development. The speed with which the information required to assess these system responses and their genomic underpinnings is changing and the importance of identifying the optimal drug or drug combinations for maximal benefit and minimal risk require that clinical trial design strategies be adaptable. In this paper, we review the tenets of adaptive clinical trial design as they may apply to an era of expanding knowledge of systems pharmacology and pharmacogenomics, and clinical trail design in network medicine.

Updates on the use of inhaled corticosteroids in asthma

PURPOSE OF REVIEW

The purpose of this review is to compare and contrast the newer inhaled corticosteroid (ICS) ciclesonide with older ICSs in terms of pharmacodynamic and pharmacokinetic properties and how these affect comparative efficacy. In addition, clinical dosing strategies for ICSs including as-needed use will be explored.

RECENT FINDINGS

Ciclesonide has demonstrated similar efficacy to that of fluticasone propionate and mometasone furoate in equipotent doses with a potentially improved therapeutic index. Once-daily administration of ICSs is generally not as effective as twice-daily. Continuous administration of ICSs does not change the natural history of asthma in either children or adults. Long-term administration of medium dose ICSs does not increase the risk of cataracts or osteopenia in children and young adults. Studies of as-needed ICSs in mild persistent asthma in adults and children have demonstrated mixed results, with some showing equal efficacy to continuous therapy and others showing superiority of continuous therapy.

SUMMARY

Ciclesonide provides a newer ICS with favorable pharmacokinetics that may improve the therapeutic index, but assessment of its systemic effects such as growth await further studies. Continuous administration of ICSs in low to medium dose over many years is well tolerated. The use of as-needed ICSs in patients with mild persistent asthma is promising as a potential step-down therapy but awaits further studies.

Update on the role of genetics in the onset of age-related macular degeneration

Age-related macular degeneration (AMD), akin to other common age-related diseases, has a complex pathogenesis and arises from the interplay of genes, environmental factors, and personal characteristics. The past decade has seen very significant strides towards identification of those precise genetic variants associated with disease. That genes encoding proteins of the (alternative) complement pathway (CFH, C2, CFB, C3, CFI) are major players in etiology came as a surprise to many but has already lead to the development of therapies entering human clinical trials. Other genes replicated in many populations ARMS2, APOE, variants near TIMP3, and genes involved in lipid metabolism have also been implicated in disease pathogenesis. The genes discovered to date can be estimated to account for approximately 50% of the genetic variance of AMD and have been discovered by candidate gene approaches, pathway analysis, and latterly genome-wide association studies. Next generation sequencing modalities and meta-analysis techniques are being employed with the aim of identifying the remaining rarer but, perhaps, individually more significant sequence variations, linked to disease status. Complementary studies have also begun to utilize this genetic information to develop clinically useful algorithms to predict AMD risk and evaluate pharmacogenetics. In this article, contemporary commentary is provided on rapidly progressing efforts to elucidate the genetic pathogenesis of AMD as the field stands at the end of the first decade of the 21st century.

Pharmacogenetics of β2 adrenergic receptor gene polymorphisms, long-acting β-agonists and asthma

Adrenergic β2 receptor (ADRβ2) agonists are widely used in asthma. Approximately 10% of patients have severe, poorly controlled disease despite extensive use of ADRβ2 agonists. Variations in responses to ADRβ2 agonists can, in part, be attributed to genetic variation, with 49 different polymorphisms having been identified for the ADRβ2 gene. Although clear associations exist between ADRβ2 gene polymorphisms, such as +46G>A, and patient response, the importance of these polymorphisms remains controversial. Patient selection, the number of polymorphisms analysed, differences in the type/dose of ADRβ2 agonist, use of inhaled corticosteroids and population sizes have all varied. Most studies were limited to mild or moderate asthmatics using ADRβ2 agonists sparingly. It is difficult to extrapolate from these studies to individual patients who have severe asthma, use a variety of ADRβ2 agonists and do so frequently. The extent to which ADRβ2 gene polymorphisms are relevant to asthma management needs further review, both clinically and at the molecular level. In vitro studies have helped to define the functional changes induced by specific ADRβ2 gene polymorphisms, including 3'-untranslated region poly-C repeat. The resulting ADRβ2 gene haplotypes (rather than genotypes), the interactions among ADRβ2 gene haplotypes and variations in the chemistry of different agonists deserve more detailed assessment. Responses to ADRβ2 agonists depend on effective downstream signalling following ADRβ2 activation and also on receptor regulation. Studies on other regulators of ADRβ2 receptor signalling and trafficking may be equally important in understanding the functional role of ADRβ2 gene polymorphisms. The role of ADRβ2 gene polymorphisms in the pathogenesis and management of severe asthma cannot be clearly defined until more specific and targeted research studies are performed.

Comparative efficacy of inhaled albuterol between two hand-held delivery devices in horses with recurrent airway obstruction

REASONS FOR PERFORMING STUDY

Studies investigating the clinical efficacy of albuterol administered with the same propellant and commercially available delivery devices in horses with recurrent airway obstruction (RAO) are not currently available.

OBJECTIVES

To determine the efficacy of aerosolised albuterol administered to horses with RAO by means of 2 commercially available, hand-held delivery devices.

METHODS

Ten horses with RAO were kept in a dusty environment and fed mouldy hay to induce airway obstruction. Lung mechanics were measured before and after the procedure. ΔP(max) was measured 5 min after administration of 180 µg of albuterol from a pressurised metered dose inhaler, using an aerosol delivery device chosen randomly. This process was repeated every 5 min until maximal bronchodilation was achieved. After a 24 h washout period, lung mechanics data were again collected using the other aerosol delivery device.

RESULTS

Aerosolised albuterol induced a significant and rapid bronchodilation in the horses using both aerosol delivery devices. No statistically significant difference in pulmonary function was observed in response to albuterol therapy between the 2 devices. The dose required to achieve 50% of maximal bronchodilation was not statistically different between the 2 devices (173.35 ± 78.35 µg with Device 1 and 228.49 ± 144.99 µg with Device 2, P = 0.26). The decrease in lung resistance tended to be more pronounced after albuterol administration with Device 1 (P = 0.066).

CONCLUSIONS

Aerosolised albuterol is an effective bronchodilator in horses with recurrent airway obstruction. There is no statistically significant difference between the 2 commercially available aerosol delivery devices in terms of efficacy.

POTENTIAL RELEVANCE

Aerosolised albuterol is effectively delivered using currently available devices leading to maximal bronchodilation in horses with RAO at an average dose of 540 µg.

Determinants of exhaled breath condensate pH in a large population with asthma

BACKGROUND

Exhaled breath condensate (EBC) pH is 2 log orders below normal during acute asthma exacerbations and returns to normal with antiinflammatory therapy. However, the determinants of EBC pH, particularly in stable asthma, are poorly understood. We hypothesized that patients with severe asthma would have low EBC pH and that there would be an asthma subpopulation of patients with characteristically low values.

METHODS

We studied the association of EBC pH with clinical characteristics in 572 stable subjects enrolled in the Severe Asthma Research Program. These included 250 subjects with severe asthma, 291 with nonsevere asthma, and 31 healthy control subjects.

RESULTS

Overall, EBC in this population of stable, treated study subjects was not lower in severe asthma (8.02; interquartile range [IQR], 7.61-8.41) or nonsevere asthma (7.90; IQR, 7.52-8.20) than in control subjects (7.9; IQR, 7.40-8.20). However, in subjects with asthma the data clustered below and above pH 6.5. Subjects in the subpopulation with pH < 6.5 had lower fraction of exhaled NO (FeNO) values (FeNO = 22.6 ± 18.1 parts per billion) than those with pH ≥ 6.5 (39.9 ± 40.2 parts per billion; P < .0001). By multiple linear regression, low EBC pH was associated with high BMI, high BAL neutrophil counts, low prebronchodilator FEV(1) ratio, high allergy symptoms, race other than white, and gastroesophageal reflux symptoms.

CONCLUSION

Asthma is a complex syndrome. Subjects who are not experiencing an exacerbation but have low EBC pH appear to be a unique subpopulation.

Combined pharmacogenetic effect of ADCY9 and ADRB2 gene polymorphisms on the bronchodilator response to inhaled combination therapy

WHAT IS KNOWN AND OBJECTIVE

Inhaled combination therapy composing of long-acting β2-agonist and corticosteroid has been widely applied in the management of asthma, but observed treatment responses vary. The aim of this study was to evaluate the pharmacogenetic effect of the adenylyl cyclase type 9 (ADCY9) gene polymorphism on combination therapy.

MATERIALS AND METHODS

Eighty-six mild to moderate Korean asthmatics were enrolled in this clinical trial. After the 2-week 'run-in' period, patients received budesonide (an inhaled corticosteroid) and formoterol (long-acting β2-agonist) during the following 12-week active treatment period. Forced expiratory volume in 1 s (FEV(1) ) and maximum mid-expiratory flow (MMEF) levels were measured at all visits as primary outcome. ADCY9 (Ile772Met, 150127 C/T, 150130 C/T, 150397 C/T, 150479 C/T, TTTA (5/4) ) and β2-adrenergic receptor (ADRB2, Arg16Gly) gene polymorphisms were genotyped.

RESULTS

Significant associations were observed between the ADCY9 single nucleotide polymorphisms and percent changes in FEV(1) (Ile772Met T/C, P = 0·030) and MMEF (150397 C/T, P = 0·016) after 8 weeks of combination therapy. Haplotype associations were also observed with respect to percent changes in FEV(1) after 8 weeks of therapy (Ht3[TTCC], P = 0·017). Additive therapeutic effect was observed in those with the ADCY9 Ile772Met and ADRB2 Arg16Gly gene polymorphisms in terms of percent change in FEV(1) after 8 and 12 weeks of therapy (P = 0·002 and P = 0·027 respectively).

WHAT IS NEW AND CONCLUSION

Our results suggest that ADCY9 gene polymorphisms may alone, and in combination with ADRB2 gene polymorphisms, contribute to individual response to combination therapy in mild to moderate asthmatics.

The role of pharmacogenomics in improving the management of asthma

There is a large amount of interindividual variability in both therapeutic and adverse responses to asthma therapies. Genetic variability can account for 50% to 60% of this variability. Pharmacogenomics holds out the promise of allowing clinicians to prospectively choose therapies that have the greatest likelihood to be effective for individual patients and to avoid those that might have a high likelihood of producing adverse effects. In this article we review the principles of pharmacogenomic investigation. We explore the data developed from the early pharmacogenomic studies with the most common asthma therapies. Furthermore, we explore the potential use of pharmacogenomics, as well as caveats in interpreting such information.

Pharmacogenetic treatments for drug addiction: cocaine, amphetamine and methamphetamine

BACKGROUND

Pharmacogenetics uses genetic variation to predict individual differences in response to medications and holds much promise to improve treatment of addictive disorders.

OBJECTIVES

To review how genetic variation affects responses to cocaine, amphetamine, and methamphetamine and how this information may guide pharmacotherapy.

METHODS

We performed a cross-referenced literature search on pharmacogenetics, cocaine, amphetamine, and methamphetamine.

RESULTS

We describe functional genetic variants for enzymes dopamine-beta-hydroxylase (DbetaH), catechol-O-methyltransferase (COMT), and dopamine transporter (DAT1), dopamine D4 receptor, and brain-derived neurotrophic factor (BDNF). A single nucleotide polymorphism (SNP; C-1021T) in the DbetaH gene is relevant to paranoia associated with disulfiram pharmacotherapy for cocaine addiction. Individuals with variable number tandem repeats (VNTR) of the SLC6A3 gene 3'-untranslated region polymorphism of DAT1 have altered responses to drugs. The 10/10 repeat respond poorly to methylphenidate pharmacotherapy and the 9/9 DAT1 variant show blunted euphoria and physiological response to amphetamine. COMT, D4 receptor, and BDNF polymorphisms are linked to methamphetamine abuse and psychosis.

CONCLUSIONS

Disulfiram and methylphenidate pharmacotherapies for cocaine addiction are optimized by considering polymorphisms affecting DbetaH and DAT1 respectively. Altered subjective effects for amphetamine in DAT1 VNTR variants suggest a 'protected' phenotype.

SCIENTIFIC SIGNIFICANCE

Pharmacogenetic-based treatments for psychostimulant addiction are critical for successful treatment.

Genetics of chronic obstructive pulmonary disease: a succinct review, future avenues and prospective clinical applications

Chronic obstructive pulmonary disease (COPD) is influenced by genetic and environmental factors. A large number of candidate gene-association studies and genome-wide linkage scans have been conducted to elucidate the genetic architecture underlying this disease. The compilation of these studies clearly revealed the complex genetic nature of COPD. Multiple genes acting on specific environmental backgrounds are likely to be the tenet of this multifactorial disorder. Encouragingly, reproducible susceptibility genes, such as SERPINE2, were recently identified. Advances in genomic research offer unprecedented capabilities to interrogate the human genome and are likely to accelerate the discovery of new genes. A comprehensive catalogue of genes implicated in the pathogenesis of COPD has great potential to lead to the development of new therapies and explain interindividual response to treatment.

Additive role of tiotropium in severe asthmatics and Arg16Gly in ADRB2 as a potential marker to predict response

BACKGROUND

Recent findings have raised new interests about the use of anticholinergics, especially tiotropium, for the treatment of asthma. This study was performed to determine whether an additional improvement in lung function is obtained when tiotropium is administrated in addition to conventional therapies in severe asthmatics, and to identify factors capable of predicting the response to tiotropium, using a pharmacogenetic approach.

METHODS

A total of 138 severe asthmatics on conventional medications and with decreased lung function were randomly recruited. Tiotropium 18 microg was added once a day and lung functions were measured every 4 weeks. Responders were defined as those with an improvement of > or = 15% (or 200 ml) in the forced expiratory volume in 1 s (FEV1) that was maintained for at least 8 successive weeks. Eleven single nucleotide polymorphisms (SNPs) in CHRM1-3 (coding muscarinic receptors one to three) which were identified by re-sequencing, and Arg16Gly and Gln27Glu in ADRB2 (coding beta(2) adrenoreceptor) were scored in 80 of the 138 asthmatics.

RESULTS

Forty-six of the 138 asthmatics (33.3%) responded to tiotropium treatment. Logistic regression analyses (controlled for age, gender, and smoking status) showed that Arg16Gly in ADRB2 [P = 0.003, OR (95% CI) = 0.21 (0.07-0.59) in a minor allele-dominant model] was significantly associated with response to tiotropium.

CONCLUSIONS

As many as 30% of severe asthmatics on conventional medications with reduced lung function were found to respond to adjuvant tiotropium. The presence of Arg16Gly in ADRB2 may predict response to tiotropium.

Absorption of montelukast is transporter mediated: a common variant of OATP2B1 is associated with reduced plasma concentrations and poor response

OBJECTIVES

To (i) determine whether montelukast undergoes carrier-mediated uptake; (ii) classify the carrier protein(s) responsible for uptake; (iii) identify specific transporters that mediate transport of montelukast; and (iv) evaluate whether variation in the gene encoding the transport protein(s) influences the pharmacokinetics and pharmacodynamics of montelukast.

METHODS

In-vitro permeability studies of montelukast are carried out using Caco-2 cell culture, a standard model of human intestinal drug transport. In-vivo plasma concentrations of montelukast in an asthmatic population are determined by high-performance liquid chromatography, and genotyping of transport proteins is by LightTyper analysis.

RESULTS

Permeability of montelukast has an activation energy of 13.7+/-0.7 kcal/mol, consistent with carrier-mediated transport. Permeability is saturable at high concentrations of montelukast and follows Michaelis-Menten kinetics. Permeability is subject to competition by sulfobromophthalein, estrone-3-sulfate, pravastatin, taurocholic acid, and cholic acid (P<0.05, percentage of control: 72+/-7-86+/-7) and is inhibited by 5-10% citrus juice (P<0.05, maximal inhibition percentage of control: 31+/-2). An MDCKII cell line expressing OATP2B1 (coded for by the SLCO2B1 gene) displays significantly increased permeability of montelukast (P<0.05, percentage of control: 140+/-20). A nonsynonymous polymorphism in SLCO2B1, rs12422149; SLCO2B1 {NM_007256.2}:c.935G>A, associates with significantly reduced plasma concentration in patients measured on the morning after an evening dose (P<0.025, square root mean transformed plasma concentration+/-SE; c.[935G>A]+[935G]=3+/-1, c.[935G]+[935G]=7.0+/-0.9) and differential response as assessed by change in baseline Asthma Symptom Utility Index scores after 1 month of therapy (delta mean Asthma Symptom Utility Index; c.[935G>A]+[935G]=0.02+/-0.01, P=1.0; c.[935G]+[935G]=1.0+/-0.3, P<0.0001).

CONCLUSION

Altogether, these observations suggest that the genetics of SLCO2B1 may be an important variable in determining the pharmacokinetics and the pharmacodynamics of montelukast.

Clinical predictors and outcomes of consistent bronchodilator response in the childhood asthma management program

BACKGROUND

Among asthmatic subjects, bronchodilator response (BDR) to inhaled beta(2)-adrenergic agonists is variable, and the significance of a consistent response over time is unknown.

OBJECTIVE

We assessed baseline clinical variables and determined the clinical outcomes associated with a consistently positive BDR over 4 years in children with mild-to-moderate persistent asthma.

METHODS

In the 1041 participants in the Childhood Asthma Management Program, subjects with a change in FEV(1) of 12% or greater (and 200 mL) after inhaled beta(2)-agonist administration at each of their yearly follow-up visits (consistent BDR) were compared with those who did not have a consistent BDR.

RESULTS

We identified 52 children with consistent BDRs over the 4-year trial. Multivariable logistic regression modeling demonstrated that lower baseline prebronchodilator FEV(1) values (odds ratio, 0.71; P < .0001), higher log10 IgE levels (odds ratio, 1.97; P = .002), and lack of treatment with inhaled corticosteroids (odds ratio, 0.31; P = .009) were associated with a consistent BDR. Individuals who had a consistent BDR had more hospital visits (P = .007), required more prednisone bursts (P = .0007), had increased nocturnal awakenings caused by asthma (P < .0001), and missed more days of school (P = .03) than nonresponders during the 4-year follow-up.

CONCLUSIONS

We have identified predictors of consistent BDR and determined that this phenotype is associated with poor clinical outcomes.

Pharmacogenetic response to albuterol among asthmatics

Pharmacogenetics offers to individualize asthma treatment by identifying genetic variants associated with drug efficacy or adverse events. Several studies have focused on pharmacogenetic associations with albuterol, the most commonly prescribed medication for asthma worldwide. However, pharmacogenetic associations have varied within and between studies and across populations. Herein, we focus on pharmacogenetic associations between genetic variants in the beta(2)-adrenergic receptor gene and bronchodilator response to albuterol among subjects with asthma.

ARG1 is a novel bronchodilator response gene: screening and replication in four asthma cohorts

RATIONALE

Inhaled beta-agonists are one of the most widely used classes of drugs for the treatment of asthma. However, a substantial proportion of patients with asthma do not have a favorable response to these drugs, and identifying genetic determinants of drug response may aid in tailoring treatment for individual patients.

OBJECTIVES

To screen variants in candidate genes in the steroid and beta-adrenergic pathways for association with response to inhaled beta-agonists.

METHODS

We genotyped 844 single nucleotide polymorphisms (SNPs) in 111 candidate genes in 209 children and their parents participating in the Childhood Asthma Management Program. We screened the association of these SNPs with acute response to inhaled beta-agonists (bronchodilator response [BDR]) using a novel algorithm implemented in a family-based association test that ranked SNPs in order of statistical power. Genes that had SNPs with median power in the highest quartile were then taken for replication analyses in three other asthma cohorts.

MEASUREMENTS AND MAIN RESULTS

We identified 17 genes from the screening algorithm and genotyped 99 SNPs from these genes in a second population of patients with asthma. We then genotyped 63 SNPs from four genes with significant associations with BDR, for replication in a third and fourth population of patients with asthma. Evidence for association from the four asthma cohorts was combined, and SNPs from ARG1 were significantly associated with BDR. SNP rs2781659 survived Bonferroni correction for multiple testing (combined P value = 0.00048, adjusted P value = 0.047).

CONCLUSIONS

These findings identify ARG1 as a novel gene for acute BDR in both children and adults with asthma.

CFH and LOC387715/ARMS2 genotypes and treatment with antioxidants and zinc for age-related macular degeneration

OBJECTIVE

To determine if CFH and LOC387715/ARMS2 genotypes influence treatment response to AREDS-type nutritional supplementation with antioxidants and zinc.

DESIGN

Retrospective analysis of participants in a randomized, controlled clinical trial, the Age-Related Eye Disease Study (AREDS).

PARTICIPANTS AND/OR CONTROLS

Eight hundred seventy-six AREDS study participants who were considered at high risk for developing advanced age-related macular degeneration (AMD).

METHODS

Using DNA extracted from venous blood of 876 white participants in AREDS categories 3 and 4, that is, those considered to be at high risk for progression to advanced AMD, the authors genotyped for the single nucleotide polymorphisms in the CFH (Y402H, rs1061170) and LOC387715/ARMS2 (A69S, rs10490924) genes. The authors performed adjusted unconditional logistic regression analysis and assessed interactions of these genotypes to determine the relationship between CFH and LOC387715/ARMS2 genotype and treatment with antioxidants plus zinc.

MAIN OUTCOME MEASURES

Interaction between genetic variants and treatment response as determined by progression from high-risk to advanced AMD.

RESULTS

Progression occurred in 264 of 876 patients from AREDS category 3 (intermediate AMD) to category 4 or 5 (unilateral or bilateral advanced AMD, respectively), or from category 4 to category 5. A treatment interaction was observed between the CFH Y402H genotype and supplementation with antioxidants plus zinc (CC; P = 0.03). An interaction (P = 0.004) was observed in the AREDS treatment groups taking zinc when compared with the groups taking no zinc, but not in groups taking antioxidants compared with those taking no antioxidants (P = 0.59). There were no significant treatment interactions observed with LOC387715/ARMS2.

CONCLUSIONS

The findings of this study indicate that an individual's response to AREDS supplements may be related to CFH genotype. This could have clinical relevance by predicting treatment outcome and potentially preventing unwanted side effects in those who may not benefit. Corroboration of these analyses is needed before considering modification of current management. This is among the first pharmacogenetic studies to suggest interaction between genotype and treatment.

Pharmacogenetics of asthma

Asthma is a common disease characterized by airway inflammation and bronchorestriction. There are several common categories of medications for treating asthma; however, not all asthmatics have the same response to these medications, some of which are adverse responses that are potentially life threatening. Because interindividual responses to asthma medications can vary considerably, the potential for genetic contributions to variable drug responses is significant. This chapter reviews the most common biological pathways targeted by asthma therapy and briefly discusses the genetic contribution to varied responses to asthma therapy for four common types of asthma medications: beta-agonists, anticholinergics, leukotriene modifiers, and corticosteroids.

Interpatient variability in rates of asthma progression: can genetics provide an answer?

Asthma is a heterogeneous disorder with a variable natural history. In children 3 patterns of the natural history of asthma have been described: early onset but transient, persistent, and later onset, with only the former leading to persistent asthma later in childhood. In adults a range of different asthma phenotypes differing in their environmental, inflammatory, and prognostic characteristics have also been described. These extend beyond allergic (extrinsic) and nonallergic (intrinsic) asthma to include persistent airflow obstruction and accelerated decrease in lung function over time. Asthma progression can be defined as the change in an individual's phenotype along a continuum ranging from nonasthmatic to asthmatic and subsequent development of severe chronic disease. It is clear that for prevention of asthma progression in patients, there is a need for both better understanding of the pathophysiology of asthma and identification of predictors of progression. Interpatient genetic variability has been shown to affect multiple facets of asthma progression, including increased susceptibility to atopy and subsequent asthma, progression to severe disease, and modification of the response to treatment. Thus genetic testing might provide a means for predicting the likely progression of an individual along the continuum, allowing targeting of preventative treatment. However, the prospect of the use of genetic information in clinical practice raises important social and ethical issues that will need to be addressed before genetic testing can be used to inform the preventative treatment of patients to prevent the development of progression of asthma in individuals.

[Genetic polymorphisms and opioid therapies]

Interindividual variability in pain perception and response to opioids in terms of efficacy and side effects has been long noted. Numerous genes have been proposed as ideal candidate genes for the study of the genetic component of pain and pharmacogenetics of opioids. Despite the inherent complexity in studying pain, it is obvious that several genetic polymorphisms contribute to modulate nociception and the antinociceptive effects of opioids; specifically those involved in pharmacokinetics and the metabolism of opioids (cytochrome P450) and neurotransmitters (catechol-O-methyltransferase), as well as those affecting pharmacodynamics or the drug targets such as the mu-opioid receptor or the unexpected melanocortin 1-receptor.

Clinical consequences of ADRbeta2 polymorphisms

The most prescribed medication for controlling bronchoconstriction associated with asthma and chronic obstructive pulmonary disease are beta-agonists. The gene ADRbeta2 encodes the beta-2-adrenergic receptor and contains several common genetic variations that affect gene expression and receptor function in vitro. The ADRbeta2 variations Gly(16)Arg and Gln(27)Glu and, more recently, haplotypic variations, have been the focus of numerous pharmacogenetic studies looking at responses to short-acting (SABA) and long-acting beta-agonists (LABA) in subjects with asthma. Thus far, a consensus on the effects of ADRbeta2 genetic variations has not been reached, although there does appear to be a reproducible adverse effect in subjects homozygous for Arg(16) that are regularly treated with SABAs. The complexity of the genotype by response effects observed makes clinical application of ADRbeta2 genetic variations limited, and may require the use of detailed haplotypic variation to fully understand the role ADRbeta2 plays in regulating beta-agonist response.

beta-Adrenergic receptor polymorphisms: relationship to the beta-agonist controversy and clinical implications

Aspects of the 'beta-agonist controversy' have recently re-emerged with the publication of data implicating the long-acting beta-agonist salmeterol in increased mortality from asthma. The reasons underlying the adverse effects of beta2-agonists as a class are unclear. Polymorphisms of the beta2 adrenoceptor (ADRB2), notably the variant associated with an arginine moiety at position 16 of the ADRB2 protein result in changes in in vitro receptor function. There is now consistent clinical evidence showing that, in vivo, patients with asthma harbouring the Arg-16 genotype may experience reduced lung function and an increased frequency of exacerbations when treated with regular short-acting beta-agonists. This may, in part, explain why beta-agonists have been associated with adverse outcomes in the past. ADRB2 genotyping of patients with severe or difficult-to-control asthma may shed light on a possible contributor to their clinical instability.

Pharmacogenetics of the response to beta 2 agonist drugs: a systematic overview of the field

The response to beta2-agonist treatment shows large repeatability within individuals and may thus be determined by genetic influences. Here we present a systematic overview of the available genetic association and linkage data for beta2-agonist treatment response. Systematic searches identified 66 eligible articles, as of March 2007, pertaining either to B2AR gene polymorphisms and short-acting or long-acting beta2-agonists or to another 29 different genes. We systematize these study results according to gene, agent and type of outcomes addressed. The systematic review highlights major challenges in the field, including extreme multiplicity of analyses; lack of consensus for main phenotypes of interest; typically small sample sizes; and poor replicability of the proposed genetic variants. Future studies will benefit from standardization of analyses and outcomes, hypothesis-free genome-wide association testing platforms, potentially additional fine mapping around new discovered variants, and large-scale collaborative studies with prospective plans for replication among several teams, with transparent public recording of all data.

Long-term safety study of levalbuterol administered via metered-dose inhaler in patients with asthma

BACKGROUND

Previous studies have raised concerns regarding the safety of regular use of beta2-agonists for treating asthma. Few studies have explored the safety of at least 1 year of use of racemic albuterol, and none have examined long-term dosing of levalbuterol.

OBJECTIVE

To examine the long-term safety of levalbuterol hydrofluoroalkane (HFA) vs racemic albuterol HFA administered via metered-dose inhaler (MDI) in patients with stable asthma.

METHODS

Patients with mild to moderate asthma (mean forced expiratory volume in 1 second [FEVI], 68.3% of predicted) 12 years or older participated in a multicenter, parallel-group, open-label study. Patients were randomized to levalbuterol HFA MDI (90 microg; 2 actuations of 45 microg; n = 496) or racemic albuterol HFA MDI (180 microg; 2 actuations of 90 microg; n = 250) for 52 weeks of 4 times daily dosing. The primary end point was the incidence of postrandomization adverse events. Asthma exacerbations and pulmonary parameters were also assessed.

RESULTS

The overall incidence of adverse events was similar for levalbuterol (72.0%) and racemic albuterol (76.8%). Rates of beta-mediated adverse events, serious adverse events, and discontinuations because of adverse events were low (<15%) and were comparable between groups. Rates of asthma adverse events for levalbuterol and racemic albuterol were 18.3% and 19.6%, respectively. Mean percentage of predicted FEV1 improved after dosing and was stable for both groups.

CONCLUSION

In this trial, up to 52 weeks of regular use of levalbuterol HFA MDI or racemic albuterol HFA MDI was well tolerated, and no deterioration of lung function was detected during the study period.