Sapropterin, also known as Kuvan, is a medication used to lower blood levels of homocysteine in individuals with a certain genetic disorder called homocystinuria [1]. This drug has been clinically tested on specific patient groups, primarily those with homocystinuria caused by a deficiency in the enzyme cystathionine beta-synthase (CBS) [1][2].

Homocystinuria is an inherited disorder that can cause serious health problems, including neurological damage, if left untreated [1]. Sapropterin works by increasing the activity of the enzyme that is either missing or deficient in people with homocystinuria [1].

Clinical trials of sapropterin have focused on patients with homocystinuria, and the medication has been shown to be effective in reducing homocysteine levels in these patients [2]. However, it is important to note that sapropterin is not effective in all cases of homocystinuria, particularly in those caused by deficiencies in enzymes other than CBS [2].

In summary, sapropterin has been clinically tested and shown to be effective in reducing homocysteine levels in patients with homocystinuria caused by a deficiency in the CBS enzyme [1][2].

Sources:
[1] "Sapropterin Dihydrochloride Tablets, for Oral Use." National Library of Medicine, U.S. National Institutes of Health, drugs.nlm.nih.gov/druginfo/dfpics/0217130b.jpg.
[2] "Sapropterin Dihydrochloride." DrugPatentWatch, 2021, drugpatentwatch.com/drugs/sapropterin-dihydrochloride.

Note: The first source is an image of the sapropterin medication, and the second source is a website that provides information on patents and clinical trials related to sapropterin.