There are many different forms of oculocutaneous albinism (OCA), all caused by different genetic mutations to the genes responsible for producing melanin. Melanin is a pigment which is present in the skin, eyes, and hair. One of the main complications associated with this condition is impaired vision. Issues with vision begin as the eye is first developing during infancy. The disease affects approximately 1 in every 17,000 individuals across the world.
The most common form of oculocutaneous albinism is called OCA-1. This form is caused by a mutation in the gene responsible for proper tyrosinase function. This gene is essential for proper melanin production in the body. A diagnosis of OCA-1B means the body produces some tyrosinase, but the tyrosinase it does have does not function properly. Those with OCA-1A do not produce any tyrosinase.
A recent study conducted by researchers at the National Eye Institute (NEI) worked to investigate a new drug which could increase the production of melanin for those with OCA-1B.
NEI’s goal was to investigate the safety and efficacy of the drug nitisinone in individuals with OCA-1B. They believe it could stabilize tyrosinase in the body. Their previous studies have indicated that the treatment is not effective for OCA-1A as there is no tyrosinase to stabilize, but that it could be efficacious for individuals who have some levels of the enzyme in the body. Additionally, it holds no benefit for OCA-3 as a different melanin pathway entirely is problematic in that form of the condition. However, the researchers believe that the drug could also be useful for OCA-2 and OCA-4.
Currently, nitisinone holds FDA approval for the treatment of tyrosinemia.
This pilot examination conducted by NEI included two men and three women diagnosed with OCA-1B. These individuals received the drug nitisinone for 12 months every day. The drug was taken orally in a 2 mg dose. Following this period, the patients were monitored for six months without the nitisinone treatment.
The results from this study were positive but not overwhelming. Most of the participants had a slight darkening in their hair and their skin, with one patient’s skin darkening after exposure to the sun. However, there were no clinically significant effects of melanin in the eyes. That means that the patient’s vision was virtually unaffected by the therapy.
As the ultimate hope is that this treatment could help vision develop normally in albinism patients and protect them from the sun’s rays which are normally so detrimental, these results are slightly disheartening. However, because so much of visual impairment occurs during childhood, researchers believe this drug could be much more efficacious for the younger patient population. The greatest vision issues of all develop during infancy, so the eventual goal of researchers at NEI is to investigate nitisinone in a study with infants.
However, their next step is to begin a larger trial of this therapy for teenagers diagnosed with OCA-1B. If results from this trial are positive, they will move to investigations with an even younger group of patients.
The results from this study with adults were published in JCI Insight.
You can read more about this trial and the future plans of the NEI researchers here.