Study design (if review, criteria of inclusion for studies)
Double-blind, placebo-controlled, crossover study
Participants
Twenty CF patients with at least one G551D mutation from a single centre
Interventions
Crossover study of ivacaftor with 28days of active treatment.
Outcome measures
Sputum microbiota composition was assessed by 16S rRNA gene amplicon sequencing and quantitative PCR at five key time points, along with regular clinical review, respiratory function assessment, and peripheral blood testing.
Main results
No significant difference in microbiota composition was observed in subjects following ivacaftor treatment or placebo (PERMANOVA P=0.95, square root ECV=-4.94, 9479 permutations). Microbiota composition variance was significantly greater between subjects, than within subjects over time (P<0.0001, Mann Whitney U test), and an additional within-patient paired assessment of microbiota similarity was therefore performed. Again, change in microbiota composition was not significantly greater during treatment with ivacaftor compared to placebo (Wilcoxon test, P=0.51). A significant change in microbiota composition was however associated with any change in antibiotic exposure, regardless of whether ivacaftor or placebo was administered (P=0.006). In a small, subgroup analysis of subjects whose antibiotic exposure did not change within the study period, a significant reduction in total bacterial load was observed during treatment with ivacaftor (P=0.004, two-tailed paired Student's t-test).
Authors' conclusions
The short-term impact of ivacaftor therapy on sputum microbiota composition in patients with G551D mutations are modest compared to those resulting from antibiotic exposure, and may be masked by changes in antibiotic treatment regimen.