474 patients were screened for the trial between 2004 and 2006. The B16 alleles were in Hardy-Weinberg equilibrium (p=0.95) in this population. 244 subjects had eligible genotypes (78 B16 Arg/Arg and 166 B16 Gly/Gly). Several of these subjects (9 Arg/Arg and 42 Gly/Gly) withdrew consent following screening because no appropriate match was identified and they no longer wanted to participate in the pre-match protocol. Forty-two B16 Arg/Arg and 45 B16 Gly/Gly subjects were randomized ().
Fate of 474 screened subjects in LARGE trial
Demographic, clinical, and physiological characteristics of randomized subjects at enrollment in the run-in of the main study (following at least 3 weeks of standard inhaled corticosteroid therapy) are in . Matching by lung function was successful. Mean FEV1 was 78.6% predicted in Arg/Arg subjects and 79.6% predicted in Gly/Gly subjects. At baseline, patients in both genotypic groups used an average 1 puff/day of rescue albuterol. Arg/Arg and Gly/Gly subjects did not differ significantly at the beginning of each treatment period with respect to any measured baseline characteristic (data not shown).
Demographics and Baseline Characteristics of Randomized LARGE subjects
Of 1910 scheduled main study visits, 1901 (99.5%) were completed. During the double-blind treatment periods, subjects recorded their AM PEF 95.7% (90.1%, 98.4%) (median (Q1,Q3)) of the days. Based on data from the DOSER™ and the Diskus, subjects took 95.1% (90.1%, 97.9%) of their scheduled QVAR puffs and 94.9% (88.2%, 98.6%) of their scheduled LABA/placebo puffs.
After 18 weeks, LABA/ICS treatment resulted in an AM PEF 21.4 (95% CI (11.8, 31.1)) L/min greater than treatment with placebo/ICS in Arg/Arg subjects (p<0.0001). Similarly, in Gly/Gly subjects, AM PEF following treatment with LABA/ICS was 21.5 (95% CI (11.0, 32.1)) L/min greater than treatment with placebo/ICS (p<0.0001). The difference between genotypes (Arg/Arg – Gly/Gly) was −0.1 (95% CI (−14.4, 14.2)) L/min (p=0.99) (). reveals both the raw and modeled data for AM PEF in B16 Arg/Arg and Gly/Gly subjects receiving ICS with placebo or LABA from beginning to end of the 18 week treatment periods. There was no significant difference between the two genotype groups (p=0.99). Correspondingly, AM PEF in the run-out did not differ significantly between those treated with LABA/ICS or placebo/ICS (data not shown)
Figure 3 Figure 3A. AM PEF in B16 Arg/Arg subjects and B16 Gly/Gly subjects receiving ICS with placebo or LABA. Both groups of subjects ended up with a higher AM PEF with LABA/ICS than with Placebo/ICS, but there was no significant difference between the two groups. (more ...)
Analyses of prespecified secondary outcomes are shown in . This table includes results of outcome characteristics stratified by genotype and between different treatment options following 18 weeks of each treatment regimen. The difference between genotypes for each treatment option is also reported (Arg/Arg difference- Gly/Gly difference). There were within- genotype differences between the LABA/ICS and placebo/ICS groups with respect to PM PEF, peak flow variability, FEV1
reversibility with albuterol, asthma symptoms, rescue therapy use, and methacholine PC20
. Most changes were quite small, and there were no other genotype specific differences (Arg/Arg vs. Gly/Gly) , except for methacholine PC20
. In Gly/Gly subjects, the methacholine PC20
doubled when LABA was added to ICS (p<0.0001), while in Arg/Arg subjects it remained unchanged (p=0.87) (). The genotype-specific difference in methacholine responsiveness was significant (1.32 doubling dose difference between genotypes (95%CI 0.43,2.21)p=0.0038) and plots of individual subjects are depicted in (and in online supplement
). Of note, there were no significant differences in exhaled NO nor in EBC pH.
Outcome characteristics following 18 weeks of treatment with Placebo/ICS or LABA/ICS in Arg/Arg and B16 Gly/Gly subjects
Figure 4 Figure 4a. Methacholine responsiveness in B16 Arg/Arg subjects and B16 Gly/Gly subjects receiving ICS with placebo or LABA. While B16 Gly/Gly subjects demonstrated a doubling of their methacholine PC20 with salmeterol compared with placebo (P<0.0001), (more ...)
Both genotype groups had a relatively high degree of reversibility to 4 puffs of ipratropium (7.6–10.1%), comparable to the degree of reversibility following 4 puffs of albuterol (6.7–10.8%) (). Post-bronchodilator FEV1 was comparable when participants took albuterol or ipratropium. There was no genotype-specific advantage for one bronchodilator over another. However, independent of genotype, the degree of bronchodilation with albuterol was significantly higher when subjects were on placebo/ICS than on LABA/ICS (10.3% vs. 6.7% in Arg/Arg, p=0.001, 10.8% vs. 8.5% in Gly/Gly, p = 0.04). This finding was not observed with ipratropium; individuals responded equally to ipratropium whether taking placebo/ICS or LABA/ICS.
As expected, exacerbation rates were low (7 Arg/Arg subjects, 5 with placebo/ICS and 2 with LABA/ICS, versus 6 Gly/Gly subjects, 3 with placebo/ICS and 3 with LABA/ICS), and no genotype-specific differences were appreciated. Five serious adverse events were reported, one each during the pre-match and run-in phases on open-label ICS, two during double-blind treatment with LABA/ICS, and one during double-blind treatment with Placebo/ICS. None of the serious events was asthma-related or related to study medications or procedures. All subjects recovered. The most prevalent non-serious adverse events reported were expected and respiratory in nature, with 94 events occurring during the prematch/run-in/run-out phases of the study, 74 occurring during double-blind treatment with Placebo/ICS and 57 occurring during double-blind treatment with LABA/ICS. Acute nasopharyngitis and acute pharyngitis comprised the majority of these adverse events.
While results among Caucasian participants alone mirrored those of the entire study population, exploratory post-hoc subgroup analyses in African Americans revealed significant changes in AM and PM PEF in the 8 Gly/Gly subjects (29 L/min, p=0.013 and 45 L/min, p= 0.0005, respectively) treated with LABA/ICS vs. placebo/ICS but not in the 9 Arg/Arg subjects (−12 L/min, p=0.57, −2.2. L/min, p=0.92) (). PEF measured at clinic visits during spirometry also improved with LABA vs. placebo in African American Gly/Gly (39 L/min, p=0.0016) but not Arg/Arg subjects (−4.8 L/min, p=0.73). Although these subgroups were small, these genotype-specific differences in AM PEF (p=0.09) and PM PEF (p=0.07) approached statistical significance, while clinic-measured PEF reached statistical significance (p=0.02). Methacholine PC20 differences paralleled the genotype-differentiated trend in the entire study cohort.
Figure 5 AM and PM PEF in the 9 African American B16 Arg/Arg and the 8 B16 Gly/Gly subjects receiving ICS with placebo or LABA. African American B16 Gly/Gly subjects ended up with a higher AM PEF with LABA/ICS than with Placebo /ICS; this was not observed with (more ...)
In addition to the African American subjects reported above, there were only 2 Asian Arg/Arg (only 1 of whom completed a phase of the trial), and 1 Asian Gly/Gly in the dataset, and 4 Hispanic Arg/Arg and 5 Hispanic Gly/Gly. For such small groups, model-derived estimates could not be obtained in our statistical model. Because of the relative heterogeneity of this ”other group” , it is more appropriate to assess genotype specific differences within ethnic groups if sufficient numbers of subjects are available for analysis.
There were no other significant genotype-specific differences in other subgroups analyzed, including in preplanned subanalyses of those who reversed by greater than or less than 12% with albuterol, or in posthoc subanalyses including only those who completed the entire trial, those who were on a controller within 6 weeks of study initiation, or males versus females (data not shown).