In this study, participants with hemophilia A or hemophilia B due to a nonsense mutation were treated with an investigational drug called ataluren (PTC124). Evaluation procedures to determine if a participant qualifies for the study was performed within 14 days prior to the start of treatment. Eligible participants who elected to enroll in the study then participated in a 28-day treatment period. Within the 28-day period, ataluren (PTC124) treatment was to be taken for 2 cycles of 14 days each 3 times per day with meals at a dose level of 5, 5, 10 milligrams/kilograms (mg/kg) in the first cycle and a dose level of 20, 20, 40 mg/kg in the second cycle. After the first 14-day cycle, study doses were changed to 10 mg/kg (morning), 10 mg/kg (midday), and 20 mg/kg (evening) and the doses were administered for 1 cycle only. Then, there was an interval of approximately 14 days without treatment. During the study, ataluren (PTC124) efficacy, safety, and pharmacokinetics were evaluated periodically with measurement of FVIII/FIX activity and inhibitor levels, other blood tests, and urinalysis.
