CFZ533 is a drug being developed by Novartis to treat myasthenia gravis (MG). It blocks immune responses that generate the antibodies responsible for causing muscle weakness.

How CFZ533 works

MG is caused by an autoimmune response. The immune system is designed to fight invaders, but in autoimmune diseases, it attacks the body’s own tissues instead. In MG, the body produces antibodies that block signals which pass from nerves to muscles, limiting muscle contraction.

Antibodies are produced by B-cells, a type of white blood cell. When the immune system responds to a specific protein — in this case, receptors that transmit nerve signals to muscles — B-cells are stimulated, or activated, to multiply and produce antibodies. CFZ533 blocks the activation of B-cells, limiting their ability to produce the antibodies that block nerve signals.

CFZ533 is able to block B-cell activation without depleting the number of B-cells in the body.

CFZ533 in clinical trials

A Phase 2 multicenter, double-blind, placebo-controlled trial (NCT02565576) to determine whether CFZ533 is an effective and safe treatment for MG is currently underway. Participants with moderate to severe MG will be randomized to receive either CFZ533 or placebo.

The primary endpoint of this study will be the change in participants’ Quantitative Myasthenia Gravis (QMG) score, which assesses a number of measures of muscle function, after 25 weeks of treatment.  The study will continue to measure scores to week 49 and will also assess the drug’s safety and its effect on daily living activities.

The study began in September 2015, with an estimated completion date of December 2017.  Several study centers are still recruiting participants.

Additional information

In this clinical trial of CFZ533, patients may continue to take one additional drug that suppresses or modulates the immune system during the study period, if they have been stable on that drug before beginning the study.

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