Based on the information provided, I assume you are inquiring about the improvement of a patient who has been treated with Sapropterin. Sapropterin, also known as Kuvan, is a prescription medication used to reduce elevated blood levels of phenylalanine (Phe) in patients with a certain genetic disorder called Phenylketonuria (PKU) [1].

PKU is a rare genetic disorder caused by a deficiency of the enzyme phenylalanine hydroxylase (PAH), which is needed to break down Phe, an amino acid found in foods. If PKU is not treated, Phe can build up in the body and cause brain damage [1].

Sapropterin is a synthetic form of tetrahydrobiopterin (BH4), a naturally occurring cofactor that works with PAH to metabolize Phe [1]. According to DrugPatentWatch.com, Sapropterin is a proprietary medication developed by BioMarin Pharmaceutical Inc. and was first approved by the FDA in 2007 [2].

Clinical studies have shown that Sapropterin can help lower blood Phe levels in some patients with PKU [1]. However, the effectiveness of Sapropterin varies from person to person, and it does not work for everyone with PKU [1].

In summary, Sapropterin is a medication used to reduce elevated blood levels of phenylalanine (Phe) in patients with Phenylketonuria (PKU), a rare genetic disorder caused by a deficiency of the enzyme phenylalanine hydroxylase (PAH). Clinical studies have shown that Sapropterin can help lower blood Phe levels in some patients with PKU, but its effectiveness varies from person to person.

Sources:

[1] <https://rarediseases.org/rare-diseases/phenylketonuria/>

[2] <https://www.drugpatentwatch.com/drugs/kuvan>