Ataluren for the treatment of nonsense-mutation cystic fibrosis: a randomised, double-blind, placebo-controlled phase 3 trial

Abstract

Background: Ataluren was developed to restore functional protein production in genetic disorders caused by nonsense mutations, which are the cause of cystic fibrosis in 10% of patients. This trial was designed to assess the efficacy and safety of ataluren in patients with nonsense-mutation cystic fibrosis.

Methods: This randomised, double-blind, placebo-controlled, phase 3 study enrolled patients from 36 sites in 11 countries in North America and Europe. Eligible patients with nonsense-mutation cystic fibrosis (aged ≥ 6 years; abnormal nasal potential difference; sweat chloride >40 mmol/L; forced expiratory volume in 1 s [FEV1] ≥ 40% and ≤ 90%) were randomly assigned by interactive response technology to receive oral ataluren (10 mg/kg in morning, 10 mg/kg midday, and 20 mg/kg in evening) or matching placebo for 48 weeks. Randomisation used a block size of four, stratified by age, chronic inhaled antibiotic use, and percent-predicted FEV1. The primary endpoint was relative change in percent-predicted FEV1 from baseline to week 48, analysed in all patients with a post-baseline spirometry measurement. This study is registered with ClinicalTrials.gov, number NCT00803205.

Findings: Between Sept 8, 2009, and Nov 30, 2010, 238 patients were randomly assigned, of whom 116 in each treatment group had a valid post-baseline spirometry measurement. Relative change from baseline in percent-predicted FEV1 did not differ significantly between ataluren and placebo at week 48 (-2.5% vs -5.5%; difference 3.0% [95% CI -0.8 to 6.3]; p=0.12). The number of pulmonary exacerbations did not differ significantly between treatment groups (rate ratio 0.77 [95% CI 0.57-1.05]; p=0.0992). However, post-hoc analysis of the subgroup of patients not using chronic inhaled tobramycin showed a 5.7% difference (95% CI 1.5-10.1) in relative change from baseline in percent-predicted FEV1 between the ataluren and placebo groups at week 48 (-0.7% [-4.0 to 2.1] vs -6.4% [-9.8 to -3.7]; nominal p=0.0082), and fewer pulmonary exacerbations in the ataluern group (1.42 events [0.9-1.9] vs 2.18 events [1.6-2.7]; rate ratio 0.60 [0.42-0.86]; nominal p=0.0061). Safety profiles were generally similar for ataluren and placebo, except for the occurrence of increased creatinine concentrations (ie, acute kidney injury), which occurred in 18 (15%) of 118 patients in the ataluren group compared with one (<1%) of 120 patients in the placebo group. No life-threatening adverse events or deaths were reported in either group.

Interpretation: Although ataluren did not improve lung function in the overall population of nonsense-mutation cystic fibrosis patients who received this treatment, it might be beneficial for patients not taking chronic inhaled tobramycin.

Funding: PTC Therapeutics, Cystic Fibrosis Foundation, US Food and Drug Administration's Office of Orphan Products Development, and the National Institutes of Health.

Figure 1. Mean Relative Change in % predicted FEV₁ from Baseline to Week 48 (ITT Population)

The plotted values represent observed data (±SEM). The dotted lines represent the average treatment effect across all post-baseline visits. The p-values were obtained from a mixed-model repeated measures (MMRM) analysis. Covariates were baseline % predicted FEV₁, treatment, visit, treatment-by-visit interaction, baseline % predicted FEV₁-by-visit interaction, and the stratification factors of baseline inhaled antibiotics (yes vs no), baseline age (<18 vs ≥18 years), and baseline % predicted FEV₁ (40 to <65% vs ≥65 to 90%). Abbreviations: FEV₁ = forced expiratory volume in 1 second, ITT = intent-to-treat, MMRM = mixed-model repeated-measures

Figure 2. Week 48 Relative Change in % predicted FEV1 by Chronic Inhaled Antibiotic Use (ITT Population)

The plotted values represent observed data (±SEM). The plot on the left includes patients who were not taking tobramycin (either no antibiotics or antibiotics other than tobramycin) chronically at baseline. The plot on the right includes patients who were taking tobramycin (either alone or in combination with other antibiotics) chronically. Abbreviations: %FEV₁ = % predicted forced expiratory volume in 1 second, ITT = intent-to-treat

Figure 3

Mean relative change in percent-predicted FEV1 from baseline to week 48, by chronic inhaled antibiotic use in the intention-to-treat population (A) Patients who were not taking tobramycin (either no antibiotics or antibiotics other than tobramycin) chronically at baseline. (B) Patients who were taking tobramycin (either alone or in combination with other antibiotics) chronically. Datapoints show the mean change in FEV1 since baseline at each timepoint; error bars show SE. FEV1=forced expiratory volume in 1 s