Long-term efficacy and safety of aerosolized tobramycin 300 mg/4 ml in cystic fibrosis

Abstract

Introduction: Aerosolized tobramycin is a standard of care for chronic Pseudomonas aeruginosa (Pa) infection in patients with cystic fibrosis (CF).

Objectives: The long-term safety and efficacy of intermittent (28-day "on"/"off" cycles) inhaled tobramycin nebulization solution 300 mg/4 ml (TNS4, Bramitob(®)/Bethkis(®)) was assessed over 56 weeks in CF patients aged ≥6 years having baseline 1 sec forced expiratory volume (FEV(1)) 40-80% predicted.

Methods: Patients were initially randomized in an 8-week open-label trial (core phase) to compare TNS4 (N = 159) and tobramycin 300 mg/5 ml (TNS5, TOBI(®)) (N = 165). A subset of patients continued in a 48-week, single-arm extension receiving TNS4 only. The primary endpoint of the core phase was to demonstrate the non-inferiority of TNS4 compared to TNS5 in terms of absolute change from baseline to week 4 in FEV(1) % predicted. The assessment of long-term safety was the primary purpose of the extension phase. Throughout all phases of the study, microbiological assessments, adverse events, and audiometry findings were also evaluated.

Results: In the core phase (N = 321), FEV(1) (% predicted) increased from baseline (absolute change) following a single on-treatment cycle for both TNS4 (7.0%) and TNS5 (7.5%) and the non-inferiority between treatments was met [difference between treatments of -0.5 (95% CI: -2.6; 1.6)]. These improvements were maintained throughout the extension phase (N = 209), ranging throughout the study between 5.1% (95% CI: 3.2; 6.9) and 8.1% (95% CI: 6.8; 9.4) compared to baseline. Pa sputum count reductions ranged between 0.6 (95% CI: 0.2; 0.9) to 2.3 (95% CI: 2.0; 2.6) log10 CFU/g throughout the 56 weeks. No remarkable safety issues were identified throughout both study phases, with similar percentages of patients reporting adverse events in the two treatment groups during the 8-week core phase [TNS4 (31.4%); TNS5 (28.0%)].

Conclusions: Overall, TNS4 demonstrated short-term clinical benefits similar to TNS5 which were maintained during the long-term use of TNS4 and was also associated with a favorable tolerability profile.

Trial registration: ClinicalTrials.gov NCT00885365 NCT01111383.

Keywords: FEV1; Pseudomonas aeruginosa; cystic fibrosis; long-term; nebulization; tobramycin susceptibility.