Eligible patients with nonsense-mutation cystic fibrosis ( aged @ years ; abnormal nasal potential difference ; sweat chloride > @ mmol/L ; forced expiratory volume in @ s -LSB- FEV@ -RSB- @ % and @ % ) were randomly assigned by interactive response technology to receive oral ataluren ( @ mg/kg in morning , @ mg/kg midday , and @ mg/kg in evening ) or matching placebo for @ weeks .