Two babies have recently been reported to have been given the first-ever treatment for a severe neurological disease called Tay-Sachs disease after more than 14 years of development.
The Conversation describes this illness as a severe disease caused by a deficiency in an enzyme known as HexA. Such an enzyme breaks down a fat-like substance that typically exists in very tiny, harmless amounts in the brain.
Minus this particular enzyme, this fatlike substance can accrue to poisonous levels that impair and destroy neurons.
One of this disease's symptoms was initially described in the early 1880s by Warren Tay, a British ophthalmologist who saw a cherry-red spot on the back of the eye of affected babies.
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Tay-Sachs Disease
In the latter part of the 1880s, Bernard Sachs, an American neurologist, described the Tay-Sachs disease's profound neurological symptoms in a paper saying nothing unusual was observed until the age of two to three months when parents observed that the baby was much more listless compared to other children of the age.
The baby would typically lay upon its back and was unable to change its position. More so, it never attempted any voluntary movement. Additionally, the child grew steadily weaker and stop taking food properly. More so, his bronchial tubes increased, and eventually, pneumonia developed and he died in August 1886.
Such a depressing description of Tay-Sachs stays current, and those with the illness typically die by age five. Some individuals develop Tay-Sachs later in life, with symptoms beginning in their teens getting progressively worse over several decades.
Unfortunately, there remains no therapy for Tay-Sachs which is detailed on the National Organization for Rare Disorders website. Hostile medical treatment can prolong survival although it does not improve neurological function.
Repairing the HexA Enzyme in the Brain
The only effective way for treating Tay-Sachs is to repair the HexA enzyme in the brain. This is problematic though since the blood-brain barrier is preventing most molecules from passing into the brain.
Miguel Sena-Esteves, a member of a research team from UMass Chan Medical School and Auburn University developed a gene therapy that may help address such a barrier.
Their treatment is using two harmless viral vectors to deliver DNA instructions to brain cells that teach them how to produce the missing enzyme.
Similar approaches have been applied for the treatment of a number of associated diseases, as well as other conditions.
As specified in the study published in the Nature Medicine journal, in the case of the Tay-Sachs, the DNA instructions are entering the nucleus of these cells and remain there, allowing for long-term HexA production.
According to previous studies, by successfully testing the gene treatment on different animal species, delivering the therapy to a central portion of the brain enables the enzyme to travel along its links to other regions to be distributed across the whole brain.
Recipients of the First-Ever Gene Therapy
The first child who was given the gene therapy treatment was then aged two-and-a-half, with late-stage symptoms of the disease. After three months of treatment, they had better muscle regulation and could focus their eyes.
Now aged five, the child has been reported to be in stable health and is seizure-free, which typically is not possible for patients at this age.
The second child treated at age seven months had improved brain development by the three-month follow-up and stays seizure-free at age a little over two.
There is a need for more testing to verify if the treatment can totally stop the progression of the disease. Given that this was the first time such therapy was given to humans, the developers used a conservative dose below the maximum treatment effects seen in animal studies.
Safety and Efficacy of Increased Doses
The team is currently carrying out a follow-up clinical trial to test the increased doses' safety and efficacy in a larger group of patients.
The rising cost of manufacturing these therapies is making it very difficult, if impossible, to develop test gene treatment for a lot of ultra-rare diseases where the group of patients globally is very small, not to mention profitably low.
They were able to deliver such therapies to the children in the ongoing clinical tests giving credit only to financial backing from a generous family whose own child is part of the project.
This grassroots method is a typical theme in the ultra-rare disease study, development and testing are frequently supported by parents, federal grants, and foundations.
Related information about Tay-Sachs disease is shown on Osmosis's YouTube video below:
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