28th February is “Rare Disease Awareness Day“, shining a light on the 300 million people living with rare diseases.
Rare disease research is close to my heart. Regular readers of this blog will know about our work on laminins, and related rare disease including the devastating skin fragility disorder junctional epidermolysis bullosa, where the skin of patients is so fragile that it blisters with the mildest of touch. Also, identifying the mutations that cause laryngo-onycho-cutaneous syndrome was the major part of my PhD and cemented my love for laminins. Even my first real taste of scientific research during a summer students, involved identifying mutations responsible for the skin and nail disease pachyonychia congenita.
However, here I want to highlight aniridia a non-laminin disease and give a little insight into our work toward a new treatment.
Aniridia, like the name suggests, is an eye developmental disorder characterised by absence of an iris (the coloured part of the eye). Because the iris is missing, the pupil can be abnormal/misshapen and lead to photophobia and reduced sharpness of vision from birth.
However, the worst features of the disease develop later in life. Once patients reach their teens or early twenties, the clear front part of the eye, the cornea, begins to fail (aniridia-related keratopathy, meaning unhealthy cornea). When this happens, the conjunctiva, the white part of the eye, begins to grow across the front. This obscures vision and is painful.
When we talk to patients, such as the aniridia UK patient network meetings, it is this corneal defect that is the biggest problem. The patients say that they get used to the early problems but this second hit makes their life noticeably worse.
The corneal problems aren’t the only issue. The majority of aniridia patients also develop cataracts very early and many develop early onset glaucoma. Cataracts are generally relatively easy to surgically correct, although the eye shape issues in aniridia patients can make this more difficult. Glaucoma is more difficult and over time can cause blindness as the optic nerve gets increasingly damaged.
Video below from Aniridia Network:
Temporary Treatments but no cure (yet)
Failure of a cornea can be treated by a corneal graft. This involves literally removing the central cornea and replacing it with a healthy one from a organ donor. There is a shortage of organ donors, therefore there is a waiting list and there is also strong effort to produce artificial corneas to obviate the need for donors for this and other corneal disorders.
However, for aniridia patients, the corneal replacement doesn’t last long. The problem in aniridia is that the corneal defect occurs due to failure of the stem cells that live around the cornea in a region called the limbus. The “limbal stem cell failure” means that the central cornea doesn’t get replaced effectively and therefore even if a healthy cornea is sutured in place it will inevitably fail over time.
The result is a rare disease that requires extensive, complex and expensive ophthalmic interventions throughout life to temporarily relieve some of the symptoms while never addressing the cause of the problems.
Although aniridia is rare, the problems it causes are similar to lots of other diseases – e.g. limbal stem cell failure can occur due to chemical burn – and increasing knowledge of these rare diseases can help develop treatments for other conditions.
Researching a cure
There are a variety of different approaches toward a cure that are being trialled. The EU have funded a consortium effort aniridia-net.eu that has connected researchers across Europe into different working groups trying different approaches to treatment. These groups include repurposing of other drugs, developing new drugs that target the genetic defect and tell the cells to ignore the mutation and molecular therapeutics that try to restore tissue function by stabilising the mRNA or protein. The EU funded work is also building patients groups to allow clinical trials etc.
My lab is also working on a different strategy.
We have established a collaboration with MiNA therapeutics to use a process of gene activation to treat the disease (explainer video below). This collaboration has been going on for a few years now, and has reached an exciting stage where we have developed a candidate therapeutic that works in cells in a dish. I can’t say too much about the specifics yet but patents has been filed so expect a more complete picture in the public domain soon.
One of the super exciting things about our work is that if our new approach works as we expect for aniridia then a similar concept is likely to become an option for other rare diseases and also for some more common disorders.
There will be an announcement soon about a job associated with this project. Follow the blog to stay updated.
As a teaser, the in vitro success and the potential of our lead candidate to be developed into a new treatment for aniridia has led to us securing grant funding from Innovate UK. The goal of this grant is to push our candidate forward down the translational pipeline and getting it ready for use in patients.
Watch this space.
If you are living with aniridia, I suggest getting in touch with one or more of the patient groups, or if you want to donate, these organisations do some excellent work:
Aniridia Network (uk)
There is also an excellent book written for patients and families