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Learn more about PKU

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PKU is a lifelong disease without a cure, however treatment is available to reduce the impacts of the disease. One of the more prevalent pharmaceutical treatments called, Kuvan can help many, but not all.  

Pharmaceutical Treatment 

Medications and enzyme replacement therapy help the body to break down phenylalanine, or to help the body tolerate it better. Depending on the impacted person’s genetic make-up they may or may not be receptive to leading medications resulting in much stricter diets and medical food reliance.  For those receptive to medication, Kuvan is prescribed from infant through any age, although many late year teenagers are starting to take Palynziq.


How Kuvan Works

When you eat foods with protein, your body breaks the protein down into several different building blocks called amino acids. One of these is phenylalanine, or Phe.


In the body, the PAH enzyme converts Phe into tyrosine in the presence of tetrahydrobiopterin (BH4). BH4 is a natural substance found in the body that helps the PAH enzyme reduce Phe to safe levels in the blood.


The active ingredient in KUVAN® (sapropterin dihydrochloride) Tablets or Powder for Oral Solution is a pharmaceutical version of BH4. It works in the same way as your body’s BH4. KUVAN adds more BH4 and stimulates the PAH enzyme to process Phe in people with PKU via a powder that is typically added to a drink. However, not all PKU affected people are receptive to Kuvan based on genetic make-up.


The PAH enzyme begins to convert Phe to tyrosine, and helps to keep your blood Phe levels low.

Key Terms

  • Phe—short for phenylalanine, this is an amino acid that comes from protein and is toxic to the brain at high levels

  • Enzyme—something your body makes that changes a chemical from one thing to another

  • PAH—short for phenylalanine hydroxylase, an enzyme that works with BH4 to break down Phe and is either missing or not working properly in people with PKU

  • BH4—short for tetrahydrobiopterin, a helper (also known as a co-factor) of the enzyme PAH

  • T—short for tyrosine, an amino acid that works as a building block for several important brain chemicals

People without PKU - working PAH enzyme


people without PKU.jpg

People without PKU can break Phe down into tyrosine with an enzyme called PAH and its helper, BH4.

People with PKU - Non-working PAH enzyme

People who have PKU were born with PAH that’s missing or not working properly, which makes it hard to break down Phe. This causes a buildup of Phe that can have toxic effects in the body and brain.

KUVAN - helping the PAH enzyme

KUVAN acts like the body’s own BH4 to help break down Phe in people with PAH that is missing or not working properly.

How Palynziq Works

PALYNZIQ is the first and only treatment to act as a substitute for your PAH enzyme through a daily injectable treatment. PALYNZIQ lowers blood Phe levels by substituting for the PAH enzyme that is missing or not working properly. PALYNZIQ is available only through a restricted program called the PALYNZIQ REMS (Risk Evaluation and Mitigation Strategy). 

people w pku PAH.jpg
kuvan helper.jpg

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