Dr. Milad Khedr is a doctor at Royal Liverpool and Broadgreen University Hospitals. He is studying the effect of nitisinone on the tyrosine levels of AKU patients. Here, we ask him about his work.
1) What is the purpose of this study?
Alkaptonuria (AKU) means that the body is unable to break down tyrosine, contained in protein in food, properly. This causes high levels of a chemical called homogentisic acid (HGA). This in turn causes the symptoms of the disease. Since 2012, a drug called nitisinone has been used to treat AKU patients at the National AKU Centre (NAC) in Liverpool. Nitisinone can halt the production of HGA, but it leads to a rise in tyrosine levels. This can cause various eye symptoms: eye dryness and pain, itching, watering of the eye and irritation.
This study will look into how nitisinone affects the tyrosine levels in alkaptonuria. This will eventually help to improve the dietary advice given to AKU patients, as well as the use of nitisinone in treating AKU. We want to investigate how healthy adults and patients with AKU break down tyrosine differently. A comparison of results between the two groups will help us understand this better.
2) How is the study organised?
There are two groups of participants: healthy volunteers and AKU patients. The latter group is studied off and on nitisinone. At each study visit, the participant is given an intravenous injection of tyrosine and phenylalanine stable isotopes (also called tracers because they have comparable structures and go through the same chemical reactions in the body). After that, multiple blood samples are taken, at regular intervals, over a two hour period.