Effect of ADRB2 polymorphisms on response to longacting beta2-agonist therapy: a pharmacogenetic analysis of two randomised studies.

BACKGROUND

New evidence has suggested that people with asthma who are homozygous for arginine at aminoacid 16 of the beta2-adrenergic receptor (ADRB2) might not benefit from longacting beta2-agonist therapy. We, therefore, investigated whether ADRB2 polymorphisms affect response to longacting beta2-agonists in combination with inhaled corticosteroids.

METHODS

Asthmatics were stratified by ADRB2 genotype in two studies to assess the effects of inhaled corticosteroids plus longacting beta2-agonists on asthma exacerbations. In study 1 (double-blind), 2250 asthmatics were randomly assigned to budesonide plus formoterol maintenance and reliever therapy, fixed-dose budesonide plus formoterol, or fixed-dose fluticasone plus salmeterol for 6 months. Study 2 (open-label) consisted of 405 asthmatics and compared an adjustable regimen of budesonide plus formoterol with fixed-dose budesonide plus formoterol and fixed-dose fluticasone plus salmeterol for 7 months. The relation between ADRB2 polymorphism, severe asthma exacerbations, and other asthma outcomes was analysed. Primary endpoints for studies 1 and 2 were severe asthma exacerbation and asthma control as assessed by measures of exacerbations, respectively.

FINDINGS

In study 1, Gly16Arg genotype had no effect on the percentage of participants with severe exacerbations across all treatment groups (99 [12%] of 833 Gly/Gly, 110 [11%] of 1028 Gly/Arg, and 32 [9%] of 361 Arg/Arg participants). Secondary endpoints, including forced expiratory volume in 1 s, peak expiratory flow, use of as-needed medication, and number of nights with awakenings were similar between genotype groups. No relation was recorded between ADRB2 haplotype and primary and secondary endpoints. In study 2, the frequency of asthma exacerbations (15 [9%] of 168 Gly/Gly, 13 [8%] of 169 Gly/Arg, and 6 [9%] of 67 Arg/Arg participants) and other study endpoints were closely similar for all ADRB2 genotypes.

INTERPRETATION

Since we showed no pharmacogenetic effect of ADRB2 variation on therapeutic response in asthma, patients, irrespective of their genotype, can continue to receive inhaled corticosteroids plus longacting beta2-agonists.