No pizza. No ice cream. No hotdogs and definitely no hamburgers. What sounds like a list of banned food for someone trying to lose weight is actually a way of life for children with a rare metabolic disorder, phenylketonuria (PKU), which prevents digestion of an essential amino acid found in most meats, eggs, dairy products, nuts and breads.
Tulane University's Hayward Genetics Center is one of the first to offer a drug therapy designed to help PKU patients manage their condition when taken as a supplement to their diet regimen.
The drug, marketed as Kuvan, was approved by the Food and Drug Administration in mid-December 2007 but was prescribed in clinical trials at Tulane for more than a month before then.
Individuals with PKU are born with a deficiency in the activity of the enzyme called phenylalanine hydroxylase (PAH), says Hans Andersson, director of the Hayward Genetics Center. With little or no PAH activity, they are unable to metabolize an essential amino acid, called phenylalanine (Phe), which is found in most foods. When Phe cannot be metabolized by the body, abnormally high levels of it accumulate in the blood and are toxic to the brain. If left untreated, PKU can result in mental retardation and other neurological problems.
In the past, PKU patients had only one option to manage the disease—a strict, low-protein diet to restrict Phe levels. Kuvan can reduce Phe levels in some patients. Andersson says he has several patients who have responded to the drug since early November 2007.
“I am very excited about this approach to therapy because it is the first novel intervention we have had for PKU patients in over 30 years,” says Andersson, an associate professor of pediatrics at Tulane.
While diet restrictions remain the primary therapy for PKU, some patients on Kuvan will be able to eat previously restricted foods, such as pizza or pasta, in limited quantities without consequence, Andersson says.