Myasterix (CV-MG01) is an investigational therapeutic vaccine being developed by Curavac to alleviate the symptoms of myasthenia gravis. Myasterix is likely to have fewer side effects and a simpler method of administration than other therapies.
How Myasterix works
Myasthenia gravis is a chronic autoimmune disorder that disrupts communication between nerves and muscles. To regulate muscle movement, the nervous system sends an electrical impulse from the brain all the way to the nerve associated with the muscle. The nerve cell then releases a neurotransmitter called acetylcholine that binds specialized receptors found on the surface of muscle cells, causing them to contract.
In myasthenia gravis patients, autobodies block or damage the acetylcholine receptors (AChR) at neuromuscular junctions, preventing acetylcholine binding. Unsuccessful communication between nerve and muscle cells results in muscle control issues. Myasthenia gravis can cause problems with control of eye movement, swallowing, breathing, or movement of the arms and legs.
The Myasterix vaccine induces the body to produce a different type of antibody, which binds to autoantibodies and T-cell receptors associated with myasthenia gravis. Obstructing receptors of the anti-AChR T-cells with the Mysterix-produced antibody prevents autoimmune production of anti-AChR antibodies. This is expected to unblock the AChR, restoring neuromuscular communication via acetylcholine successfully binding to its receptor.
This approach of introducing antibodies to deter autoimmune responses is called antigen receptor mimetic (ARM), and research is underway to use ARM vaccinations as potential treatments for many other autoimmune diseases. If clinical trials are successful, Myasterix could potentially replace daily therapies that have undesirable side effects.
Myasterix in clinical trials
Curavac’s first clinical trial (NCT02609022) for Myasterix is underway; it’s likely to wrap up by December 2017. The Phase 1b study — randomized, double-blind, placebo-controlled and dose-escalating — aims to assess the safety and tolerability of Myasterix and the immunogenic response it may trigger.
The study includes 24 myasthenia gravis patients aged 18 to 64, and consists of two parts: a five-month active period, during which the vaccine or placebo is administered, and a two-year observational period to assess the treatment’s long-term effects. The first two groups of eight patients have already completed the trial. These patients received three injections of low-dose Myasterix, high-dose Myasterix or placebo under the skin over three months. Preliminary results have been positive, with no serious adverse events reported, and indications that the higher dose was more successful in reducing concentrations of anti-AChR antibodies. Mild adverse events included injection site reactions that resolved without treatment in a few days. Curavac presented these results in May 2017 at the 13th International Conference on Myasthenia Gravis and Related Disorders, organized by The New York Academy of Science.
A second clinical trial (NCT03165435) is now recruiting participants. The phase 2/3 trial is a multi-center, randomized, double-blind, placebo-controlled, parallel group study and aims to demonstrate the clinical efficacy of Myasterix. About 66 patients will receive three consecutive under-the-skin injections of Myasterix or placebo over three months. Researchers will monitor safety and efficacy throughout the treatment period and for 12 weeks after the last injection.
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