PKU Treatment: Medical Foods vs Kuvan vs Palynziq

Gerald Vockley, MD, PhD, Head of the Division of Medical Genetics at UPMC Children’s Hospital of Pittsburgh, discusses the limitations of the current treatment options for individuals with phenylketonuria (PKU).

As Dr. Vockley explains, PKU is a rare genetic metabolic disorder that results in reduced activity of phenylalanine hydroxylase that leads to an accumulation of phenylalanine in the body, which can cause significant organ damage, especially in the central nervous system. If left untreated, PKU patients can develop chronic intellectual, neurodevelopmental, and psychiatric disabilities, as well as seizures and heart problems.

The currently approved treatments for PKU are medical foods, sapropterin (Kuvan), and pegvaliase (Palynziq). Dr. Vockley notes the limitations of each of those therapies and the need for more treatment options. Medical foods are protein rich meals with no, or very little, phenylalanine. Adhering to this diet can be very difficult and can be very expensive. Sapropterin is synthetic cofactor (BH4) that can enhance enzyme activity to degrade phenylalanine. This medication is effective in about one-third to one-half of patients with PKU but typically cannot normalize phenylalanine levels and patients need to remain on a fairly strict diet.

Pegvaliase reduces blood phenylalanine concentrations by converting phenylalanine to ammonia and trans-cinnamic acid. It is only approved for adults with PKU.