For 55 years, the inborn error of metabolism known as phenylketonuria (PKU) has been managed with a phenylalanine-free diet. In 1961, dietary management successfully prevented mental retardation in children with PKU when Dr Robert Guthrie developed a simple blood test that permitted identification of affected newborns early enough for dietary therapy to prevent brain damage from phenylalanine (Phe) accumulation.

A new drug, sapropterin dihydrochloride (Kuvan, BioMarin Pharmaceuticals, Novato, California), is the first drug of its kind approved by the Food and Drug Administration for treatment of PKU.1 Along with a Phe-restricted diet, sapropterin dihydrochloride reduces blood Phe levels in patients with hyperphenylalaninemia. Sapropterin dihydrochloride is a naturally occurring enzyme cofactor that works in conjunction with phenylalanine hydroxylase to metabolize Phe. Phe is found in foods that contain proteins (meats, dairy, egg products). It is estimated that 30% to 50% of PKU patients will respond to sapropterin dihydrochloride. Patients who do not follow a Phe-restricted diet will not benefit from sapropterin dihydrochloride.

Reference