Confirmed beta16 Arg/Arg polymorphism in a patient with uncontrolled asthma

The emerging role of tiotropium for patients with asthma

OBJECTIVE

To review clinical data on the use of the long-acting anticholinergic agent tiotropium in patients with asthma.

DATA SOURCES

A literature search was performed via EMBASE and MEDLINE (1966-November 2012). The search was limited to human data published in the English language. Search terms included asthma, tiotropium, and long-acting anticholinergics.

STUDY SELECTION AND DATA EXTRACTION

Relevant information related to the use of tiotropium in patients with asthma was reviewed. Randomized controlled trials and open-label trials were included. The references of published articles identified in the search were also examined for additional studies appropriate to include in the review. Data were prioritized if they originated from human studies, especially if derived from randomized, placebo-controlled trials. Trials and case reports involving the use of long-acting anticholinergic tiotropium in asthma patients were included; conversely, trials involving ipratropium were not.

DATA SYNTHESIS

Two large randomized controlled trials support the safety and efficacy of adding tiotropium to the treatment regimen of select patients with poorly controlled asthma already receiving combination high-dose glucocorticosteroid/long-acting β-agonist (LABA) therapy. Pharmacogenomic studies have shown that patients with polymorphisms of the β2-adrenoreceptor (ADRB2; 16 Arg/Arg and 16 Arg/Gly) are particularly responsive to treatment with tiotropium. Smaller studies indicate that the advantages may be most pronounced in patients with a predominance of sputum neutrophils and that tiotropium can assist with decreasing the inhaled corticosteroid (ICS) dose. An increased risk of cardiovascular events was not identified.

CONCLUSIONS

Tiotropium should be considered in patients with asthma who remain symptomatic while receiving high-dose ICS and LABA therapy. Specifically, patients with high sputum neutrophil levels or with 16 Arg/Arg or 16 Arg/Gly polymorphism of the ADRB2 gene appear to respond best.

Polymorphisms of the β2-adrenergic receptor correlated to nocturnal asthma and the response of terbutaline nebulizer

BACKGROUND

Inhaled β(2)-adrenergic receptor (β(2)-AR) agonists are the mainstay of treatment of acute asthma. Polymorphisms of the β(2)-AR, especially codons 16, 27, and 164, may affect the functions of the receptor. This study was conducted to investigate whether different polymorphisms of the β(2)-AR are related to the treatment responses of an inhaled β(2)-AR agonist in children with nocturnal and nonnocturnal asthma in Taiwan.

METHODS

The nocturnal asthma group consisted of 27 children (mean age of 10.3±2.4 years), and the nonnocturnal asthma group consisted of 24 patients (mean age of 9.9±3.0 years). Allele-specific polymerase chain reaction was performed to determine 16, 27, and 164 loci alleles of β(2)-AR genetic polymorphisms, and peak expiratory flow (PEF) was measured before and 1 hour after inhalation of 0.2mg/kg/dose of terbutaline to determine the treatment response in these patients.

RESULTS

The polymorphisms of β(2)-AR 27 but not 16 or 164 were significantly associated with the response to terbutaline nebulizer (p<0.05). The polymorphism of β(2)-AR 16 was associated with nocturnal asthma (p=0.027). The Gly16 allele was more prevalent in the nocturnal asthma group (9/27; 33.3%) than in the nonnocturnal asthma group (3/24; 12.5%). Arg16 allele was less prevalent in the nocturnal asthma (3/27; 11.1%) than in the nonnocturnal asthma group (10/24; 41.7%). There was also a linkage disequilibrium found between β(2)-AR 16 (Arg/Arg) and β(2)-AR 27 (Gln/Gln).

CONCLUSION

These findings suggest that polymorphisms of β(2)-AR 16 are related to nocturnal asthma and polymorphisms of β(2)-AR 27 are associated with the variable responses to the inhaled terbutaline in children with nocturnal and nonnocturnal asthma.