FDA Grants Orphan Drug Status to Ra Pharma’s Zilucoplan as Potential MG Treatment

The U.S. Food and Drug Administration (FDA) has granted orphan drug designation to zilucoplan, Ra Pharmaceuticals‘ lead candidate for the treatment of myasthenia gravis (MG). This status helps to support the potential therapy’s development by granting Ra Pharma certain incentives.

Zilucoplan, formerly known as RA101495, is an artificial peptide that binds to complement 5 (C5), blocking its activity and preventing the overactivation of the complement system — a set of more than 50 blood proteins that form part of the body’s immune defenses — which is thought to be involved in the formation of harmful autoantibodies in MG.

It is currently being developed to treat people with generalized MG, immune-mediated necrotizing myopathy (IMNM), and other rare complement system disorders currently lacking treatment options.

“gMG is a chronic and debilitating neuromuscular disease that affects more than 60,000 patients in the U.S. who have limited treatment options,” Doug Treco, PhD, president and chief executive officer of Ra Pharma, said in a press release.

“We’ve designed zilucoplan, a macrocyclic peptide inhibitor of C5, as an easy-to-use, self-administered subcutaneous [under the skin] treatment option to address the underlying cause of gMG through targeted complement control,” he added.

A Phase 2 trial (NCT03315130) in 44 gMG patients showed that zilucoplan, when administered over 12 weeks at a daily dose of 0.3 mg/kg, significantly lower scores in quantitative MG (QMG) and myasthenia gravis activities of daily living (MG-ADL) tests for those treated compared to people given a placebo.

Of note, QMG is a test that measures muscle weakness, while MG-ADL measures a therapy’s ability to improve participants’ engagement in daily life activities.

Ra Pharma is now preparing to launch a 12-week Phase 3 trial to further explore the effectiveness of zilucoplan, given as a 0.3 mg/kg dose under-the-skin injection, in up to 130 gMG patients.

“With site activations underway, we are on track to initiate our single, pivotal, 12-week, Phase 3 trial of zilucoplan for the treatment of gMG in the second half of this year,” Treco said.

Orphan drug status is given to investigative treatments for people with a rare disease, defined in the U.S. as disorders that affect fewer than 200,000 people. The designation comes with certain benefits, including financial incentives for therapy development and commercialization, U.S. market exclusivity for a period of seven years following approval, FDA support for clinical studies, and special fee exemptions and reductions.