A Cochrane review included 2 studies. One trial administered 10 mg/kg/day sapropterin in 89 children and adults with phenylketonuria (PKU) whose diets were not restricted and who had previously responded to saproterin. This trial lasted 6 weeks and measured change in blood phenylalanine concentration. The second trial screened 90 children (4 to 12 years) with PKU whose diet was restricted, for responsiveness to sapropterin; 46 responders entered the placebo-controlled part of the trial and received 20 mg/kg/day sapropterin. This trial lasted 10 weeks and measured change in both phenylalanine concentration and protein tolerance. Both trials reported adverse events.
The first study showed a significant lowering in blood phenylalanine concentration in the sapropterin group (MD -238.80 μmol/L, 95% CI -343.09 to -134.51); the second trial showed a non-significant difference (MD -51.90 μmol/L, 95% CI -197.27 to 93.47). The second trial also reported a significant increase in phenylalanine tolerance (MD18.00 mg/kg/day, 95% CI 12.28 to 23.72) in the sapropterin group. There were no serious adverse events associated with the treatment in the short term.
Comment: The quality of evidence is downgraded by indirectness (lack of long-term data and lack of data on the effectiveness of the treatment on intelligence, growth and quality of life and in people with severe PKU).