The efficacy of sapropterin, a drug used for the treatment of phenylketonuria (PKU), has been confirmed through patient response as observed in various clinical studies. PKU is a genetic disorder characterized by the body's inability to break down an amino acid called phenylalanine, leading to its buildup in the body, which can cause brain damage [1].

Sapropterin, also known as tetrahydrobiopterin, is a cofactor for phenylalanine hydroxylase, the enzyme that metabolizes phenylalanine [2]. By providing sapropterin, the enzyme's function can be restored, thereby reducing the levels of phenylalanine in the body.

The efficacy of sapropterin has been demonstrated through patient response in several clinical trials. One study published in the Journal of Inherited Metabolic Disease found that sapropterin treatment led to a significant reduction in plasma phenylalanine levels in PKU patients [2]. The study also reported that sapropterin was well-tolerated, with only a few mild adverse events.

Another study published in the American Journal of Medical Genetics reported that sapropterin treatment resulted in a significant reduction in phenylalanine levels in PKU patients, with a greater response observed in patients with higher baseline phenylalanine levels [3]. The study also found that sapropterin treatment was associated with improved neurocognitive function in PKU patients.

In addition, a systematic review and meta-analysis of 13 clinical trials found that sapropterin treatment was associated with a significant reduction in phenylalanine levels in PKU patients [4]. The review also reported that sapropterin treatment was well-tolerated, with only a few mild adverse events.

In conclusion, the efficacy of sapropterin in the treatment of PKU has been confirmed through patient response in various clinical studies. Sapropterin has been shown to significantly reduce phenylalanine levels in PKU patients, with a greater response observed in patients with higher baseline phenylalanine levels. Sapropterin has also been found to be well-tolerated, with only a few mild adverse events.

Sources:

[1] <https://www.drugpatentwatch.com/p/tradename/SAPROPTERIN>
[2] <https://pubmed.ncbi.nlm.nih.gov/25563006/>
[3] <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9013411/>
[4] <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6164033/>