The first patient has just been dosed in a Phase 3 trial of a drug to treat spinal muscular atrophy, reports Benzinga.
The drug, called AVXS-101, is a gene therapy developed by the company AveXis. It is designed to treat spinal muscular atrophy Types 1, 2, and 3.
Spinal muscular atrophy (SMA) is a rare genetic condition that causes muscles to weaken over time. It is thought to affect one in 10,000 children and is the most common genetic reason for infant mortality. It is caused by a change in the SMN1 gene that codes for the SMN protein, which is involved in the survival of motor neurons. Motor neurons are nerves that connect the brain and central nervous system to muscles and glands. The malfunction of these neurons in patients with SMA leads to progressive muscle weakness that causes symptoms such as floppy arms and legs, movement issues, tremors, difficulties breathing and swallowing, and bone problems like a curved spine.
There are four types of SMA. Type 1 is the most severe and affects approximately 60% of SMA patients. This form tends to develop in babies before they reach 6 months. Approximately 27% of children with SMA have Type 2, which appears between 7-18 months. This form is less severe than Type 1, but most children affected will need support to stand and walk, and it is associated with a significantly increased risk of mortality. Types 3 and 4 affect 13% of SMA patients and appear after 18 months or in adulthood, respectively.
There is not currently an approved treatment for SMA, and most medical support focuses on reducing the symptoms of the disease, but research into this is ongoing. The gene therapy called AVXS-101 is currently being trialled in a study called SPRINT that assesses its safety and usefulness as a treatment for patients with SMA Types 1, 2, and 3.
The therapy works by inserting a functional copy of the SMN1 gene that is defective in SMA patients in a one-time treatment. The study will take place in thirteen different countries, including at several sites in the US. Researchers plan to treat and follow up 44 children with SMA who receive the therapy before their symptoms begin to appear. It is crucial to treat children with SMA as soon as possible, as this study is doing, because motor neurons become permanently damaged over time. The measure of success will be different for different participants depending on their specific form of SMA. For some children the outcome hoped for will be being able to sit for 30 seconds without support, while for others it will be standing unsupported for three seconds, or not developing symptoms of the condition at all.
