Sapropterin Dihydrochloride is a synthetic form of tetrahydrobiopterin (BH4), a cofactor for the enzyme phenylalanine hydroxylase (PAH). It is used in the treatment of phenylketonuria (PKU), a metabolic disorder characterized by an inability to break down the amino acid phenylalanine. This leads to high levels of phenylalanine in the blood, which can cause severe intellectual disability and other neurological issues if left untreated.
