A Phase 2 Study of the Effects of 6R-BH4 in Subjects With Sickle Cell Disease

Subjects will receive oral, once-daily (for 2.5, 5, 10mg/kg/day doses) or twice-daily (for the 20 mg/kg/day dose) sapropterin dihydrochloride during a 16-week dose escalation phase, with dose levels increasing within subjects every 4 weeks as follows: 2.5, 5, 10, and 20 mg/kg/day. Dosing was with 100 mg tablets and rounded to the nearest whole tablet. Each dose was taken within 1 hour after the morning meal. Subjects may continue in an optional extension phase at the highest tolerated dose for up to a total of 2 years.