Nitisinone is in clinical development for the treatment of alkaptonuria. Alkaptonuria is a rare metabolic disorder, in which patients lack a functional enzyme that prevents the body fully breaking down two amino acids called tyrosine and phenylalanine. This results in a build-up of a chemical called homogentisic acid (HGA) in the body, which is deposited as black pigment in tissues, in a process called ochronosis. This results in dark colouration of urine, joint problems, breathing difficulties and heart, kidney and prostate problems. In the later stage, patients may experience physical disability and inability to perform daily activities. Early recognition and management of alkaptonuria is desirable to slow the progression of this disease.
Nitisinone, which is administered orally, works by blocking the production of the HGA molecule, and early trial evidence confirms a reduction in HGA levels and suggests the nitisinone could slow down or stop the disease and may partially reverse ochronosis. If licensed, nitisinone may provide the first pharmacological treatment option for patients with alkaptonuria who do not have any approved treatment.
Migalastat works by stabilizing the body’s own dysfunctional enzyme, so it can clear the accumulated disease substrate in patients who have amenable mutations. Migalastat is currently licenced for patients aged 16 or over with Fabry disease and an amenable mutation. If the license is extended, migalastat may offer an additional treatment option for paediatric subjects 12 to 15 years old with Fabry disease and an amenable mutation, who weight over 45Kgs.