Argenx’s Rare Disease Treatment Strikes Gold in Phase III

Memo Therapeutics Antibody

The Dutch biotech argenx aims to apply for FDA approval of its lead candidate efgartigimod after the first-in-class drug improved motor symptoms of the autoimmune disease myasthenia gravis in a phase III trial.

The phase III trial tested the effect of efgartigimod in 167 patients with generalized myasthenia gravis. In this incurable chronic condition, the immune system attacks proteins vital for communication between nerves and muscles, weakening muscles in the eyes, limbs, jaw, and eventually muscles vital for breathing. 

The company tested the drug in two types of myasthenia gravis patients: those whose immune system produces antibodies attacking a signaling protein called the acetylcholine receptor — the most common type — and those lacking antibodies against the acetylcholine receptor.

According to the trial results, efgartigimod improved motor symptoms for at least four weeks in 68% of patients with the most common type of myasthenia gravis, compared to only 30% of patients in the placebo group. In addition, efgartigimod allowed 40% of patients expressing antibodies against the acetylcholine receptor to show minimal or no motor symptoms, compared to just 11% in the placebo group. 

In the second type of patients, the placebo group showed a high response, and the benefits of efgartigimod were less clear. 

Buoyed by these results, argenx expects to apply for FDA approval for the treatment of myasthenia gravis by the end of 2020. Current treatments for the condition are limited to treating the symptoms with drugs such as immunosuppressants.

Patients with this devastating disease can experience chronic and potentially life-threatening muscle weakness that has a major impact on their quality of life, and more treatment options are needed,” stated James Howard, Professor of Neurology at the University of North Carolina, USA, and principal investigator for the trial. 

These data show efgartigimod has potential to make a meaningful impact on daily living activities.

Efgartigimod is an antibody fragment designed to block a protein called the neonatal Fc receptor, which prevents the removal of disease-causing antibodies from the blood. The drug therefore reduces the number of antibodies attacking the nerve-to-muscle communication machinery, and could offer a new treatment option for patients with this chronic condition.

In addition to myasthenia gravis, argenx is developing efgartigimod for other indications such as the autoimmune condition primary immune thrombocytopenia. The drug succeeded in a phase II trial in patients with the condition in 2018, and is now undergoing three phase III trials to confirm its benefits.

The latest clinical success has pushed argenx’s stocks up by more than 30% on the Nasdaq Stock Exchange as of this morning. This could enhance argenx’s already sky-high ability to raise big rounds. For example, the company launched a global offering worth a hefty €500M last year.

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