The genetic disorder that indicates sapropterin use is Phenylketonuria (PKU). PKU is a rare, inherited disorder in which the body cannot metabolize an amino acid called phenylalanine (Phe) [3]. If PKU is not treated, Phe can build up to harmful levels in the body, leading to serious health problems [3].

Sapropterin is a medication used to reduce elevated phenylalanine levels in people with PKU [1]. It is a synthetic form of tetrahydrobiopterin (BH4), a cofactor that plays a crucial role in the metabolism of phenylalanine [2]. By providing BH4, sapropterin helps the body break down phenylalanine more effectively, reducing its levels in the body [2].

It is important to note that sapropterin is not effective for everyone with PKU, and its use should be determined by a healthcare professional [2]. A low-phenylalanine diet is still the primary treatment for PKU, and sapropterin is used as an adjunct therapy [3].

In summary, sapropterin is used to treat PKU, a genetic disorder that affects the body's ability to metabolize phenylalanine. Sapropterin provides BH4, a cofactor that helps break down phenylalanine, reducing its levels in the body.

Sources:

[1] <https://www.drugpatentwatch.com/p/tradename/SAPROPTERIN>
[2] <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6404194/>
[3] <https://www.nhs.uk/conditions/phenylketonuria/>