Zilucoplan is an experimental treatment for myasthenia gravis. The treatment was developed originally by Ra Pharmaceuticals, which has been acquired by UCB. UCB will continue the development of zilucoplan, which has been granted orphan drug status by the U.S. Food and Drug Administration (FDA).

What is myasthenia gravis?

Myasthenia gravis is an autoimmune disease that affects the junction between nerve cells and muscles, the so-called neuromuscular junction. The attack by the immune system weakens the junctions, causing nervous signals to be effectively transported to muscles, leading to muscle weakness and fatigue, among other symptoms.

How does zilucoplan work?

Zilucoplan is a small, synthetic molecule that is designed to bind and inhibit portions of the immune system called the complement system. The complement system is made up of a large group of proteins that are involved in activating the immune cells that produce antibodies.

In myasthenia gravis, the complement system is thought to be involved in stimulating the production of harmful autoantibodies.

By blocking the complement system, zilucoplan may be able to reduce the release of autoantibodies that attack the neuromuscular junction. This should slow the progression of myasthenia gravis and lessen its symptoms.

Zilucoplan is delivered as a subcutaneous (under-the-skin) injection and can be self-administered by patients.

Zilucoplan in clinical trials

A Phase 2 clinical trial (NCT03315130) is evaluating the safety and effectiveness of zilucoplan in treating 44 myasthenia gravis patients. Participants are assigned randomly to receive 0.1 mg zilucoplan per kilogram  (kg) of body weight, 0.3 mg zilucoplan per kg body weight, or placebo, administered under the skin every day for 12 weeks.

The primary outcome measured is QMG (quantitative myasthenia gravis), a test that assesses a patient’s level of muscle weakness. The secondary outcome measured was the patients’ engagement in daily activities using the myasthenia gravis activities of daily living (MG-ADL) scale, a test of daily activities patients are able to perform.

Preliminary, 12-week results from the trial showed that patients treated with zilucoplan had significant improvement in both QMG and MG-ADL compared to those given placebo. The higher dose of zilucoplan produced more significant improvements. Only mild adverse side effects not related to treatment were reported.

Based on the Phase 2 results, a Phase 3 clinical trial (NCT04115293) called RAISE is now recruiting 130 myasthenia gravis patients at 31 sites worldwide to further test the effectiveness of zilucoplan. Patients will be assigned randomly to receive either 0.3 mg zilucoplan per kg body weight, or placebo, via a daily under-the-skin injection for 12 weeks. The primary outcome measure will be changes in MG-ADL scores from the beginning to the end of the study, with the secondary outcome measure being changes in QMG from the beginning to the end of the study.


Last updated: Oct. 16, 2019


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