Myasthenia gravis (MG) is an autoimmune disease that causes muscle weakness. The disease is incurable, but several available treatments can cause MG to go into remission, sparing patients its symptoms for awhile. However, these treatments do not work for everyone, and no approved treatments exist for rarer types of MG such as MuSK-MG .
Researchers continue to look for treatments that are more effective at managing the disease or ultimately curing it, with several clinical trials in the pipeline.
Investigational drugs
Firdapse (amifampridine phosphate) is being developed by Catalyst Pharmaceuticals in collaboration with BioMarin Pharmaceuticals, to treat multiple autoimmune conditions including MuSK-MG. Catalyst recently announced positive results from a proof-of-concept trial, and a Phase 3 trial (NCT02562066) is now recruiting U.S. participants to further test Firdapse.
Prograf (tacrolimus, FK506) suppresses the immune system. Developed by Astrella Pharmaceuticals to prevent organ transplant rejection, it’s also being investigated in autoimmune diseases like MG. Multiple clinical trials have assessed its potential benefit to MG patients, and results suggest it could be a promising therapy suitable for long-term use.
Other examples include tirasemtiv (CK-2017357) being developed by Cytokinetics to potentially treat amyotrophic lateral sclerosis (ALS)  and other diseases linked to muscle weakness. Tirasemtiv was tested in a Phase 2 clinical trial (NCT01268280). The results, published in the scientific journal Neurotherapeutics, showed it produced dose-related improvements in disease severity, was well-tolerated and did not cause any serious adverse events. Researchers concluded that tirasemtiv may improve muscle function in MG.
Biological drugs
Soliris (eculizumab) is being investigated by Alexion Pharmaceuticals as a therapy for drug-resistant generalized MG (gMG). On August 21, 2017, the European Commission (EC) approved Soliris as the first treatment for gMG. The approval was based on the results of a Phase 3 clinical trial called REGAIN (NCT01997229) which suggested a reduction in disease severity in patients treated with Soliris. In January 2017, the company also filed a supplementary Biologics License Application (sBLA) to the U.S. Food and Drug Administration (FDA) to extend the Soliris indication to include treatment for gMG.
Rozanolixizumab (UCB7665) is under development by UCB for the treatment of immunological disorders, including MG. UCB is currently recruiting participants for a Phase 2 clinical trial (NCT03052751) to assess the safety and efficacy of rozanolixizumab compared to a placebo in patients with MG.
CFZ533 is being developed by Novartis as an add-on therapy to standard of care in patients with MG and is currently in Phase 2 clinical trial (NCT02565576)Â to evaluate its safety, tolerability, and efficacy in comparison to a placebo.
Rituxan (rituximab), developed by Genentech, is being investigated as a therapy for MG. Multiple small pilot studies have reported Rituxan to be a well-tolerated and potentially effective treatment for MG, for example in the scientific journal Annals of Clinical and Translational Neurology. A Phase 2 trial (NCT02110706) called BeatMG is expected to be completed in December 2017, and a Phase 3 trial (NCT02950155) is currently recruiting participants. Rituxan is approved for the treatment of several other conditions, including other immune diseases such as rheumatoid arthritis and types of ANCA vasculitis.
Other examples of biological drugs include Orencia (abatacept) developed by Bristol-Meyers Squibb (NCT03059888), Hizentra (subcutaneous immunoglobulin) developed by CSL Behring (NCT02774239) and ARGX-113 developed by Argenx (NCT02965573).
Antisense drugs
Antisense drugs aim to stop production of a protein that causes a certain condition. Monarsen (EN101) is an antisense drug that could potentially treat MG. It works by binding to the messenger RNA, the molecule used by the protein synthesis machinery of a cell, and stops it from being read. The aim is to prevent the production of an enzyme known as acetylcholinesterase (AChE), which breaks down a chemical messenger called acetylcholine that carries signals between nerves and muscles. This should increase the amount of acetylcholine available to help muscle activation and contraction.
Amarin bought the rights to Monarsen, but that company has no plans to further develop the product. Other research groups are interested in Monarsen, but the drug’s future is currently unknown.
Vaccines
Myasterix (CV-MG01) is a vaccine for MG being developed by CuraVac in collaboration with several European companies, with funding from the European Commission. Myasterix aims to improve or cure symptoms of MG, and is currently being tested in a Phase 2/3 clinical trial (NCT03165435) to test its efficacy in people with MG. That trial is now recruiting participants.
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