UCB, a biopharma company headquartered in Brussels, Belgium, recently announced that the US Food and Drug Administration (FDA) has granted approval for its drug, Rystiggo (rozanolixizumab), for the treatment of generalized myasthenia gravis (gMG). UCB specializes in the discovery and development of innovative medicines for severe diseases that affect the immune system or central nervous system.
Rystiggo received FDA approval under the Priority Review designation, specifically for the treatment of gMG in adult patients who have tested positive for anti-acetylcholine receptor (AChR) or anti-muscle-specific tyrosine kinase (MuSK) antibodies.
“There is a significant need for new, innovative treatment options to reduce the day-to-day burden of gMG. Rozanolixizumab-noli is a new treatment option, targeting one of the mechanisms of disease to provide symptom improvement in patient-and physician-reported outcomes at Day 43,” said Vera Bril, professor of Medicine (Neurology) at the University of Toronto, and lead investigator of the MycarinG study, in the company’s news release.
What Is Generalized Myasthenia Gravis (gMG)?
Generalized myasthenia gravis (gMG) is a chronic autoimmune neuromuscular disease characterized by skeletal muscle weakness. It affects the muscles responsible for body movement in the arms and legs, as well as those involved in breathing. The disease is considered rare, with a global prevalence ranging from 100 to 350 cases per 1 million people. Individuals with gMG can experience various symptoms, including severe muscle weakness that may lead to life-threatening respiratory muscle weakness, double vision, drooping eyelids and difficulties with swallowing, chewing and speaking.
The root cause of myasthenia gravis is the disruption of nerve signal transmission to the muscles. This disruption takes place at the neuromuscular junction, the site where nerve cells form connections with the muscles they regulate. In the case of gMG, certain autoantibodies target specific proteins on the post-synaptic membrane of the neuromuscular junction, thereby impairing synaptic transmission. As a result, the nerves fail to stimulate the muscles effectively, leading to weakened muscle contractions.
“gMG can cause unpredictable fluctuations in severity and frequency of symptoms, which are often debilitating and can substantially impact the lives of patients. People living with gMG often face treatment options that are broad-acting, and that have traditionally only offered symptomatic relief,” Bril further added.
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How Does Rystiggo (Rozanolixizumab) Work?
Rystiggo (rozanolixizumab) is a medication indicated for the treatment of gMG in adult patients who test positive for AChR or MuSK antibodies. The active ingredient in Rystiggo is rozanolixizumab, a humanized IgG4 monoclonal antibody. It works by blocking the neonatal Fc receptor (FcRn), which leads to a reduction in circulating IgG levels. Peak plasma levels of rozanolixizumab are typically reached approximately two days after subcutaneous administration.
The FDA’s approval of Rystiggo is underpinned by substantial clinical evidence that affirms its efficacy. The Phase III MycarinG study was instrumental in securing this approval. This study compared different treatment groups based on changes from the baseline in the Myasthenia Gravis-Activities of Daily Living (MG-ADL) total score on Day 43. The MG-ADL scoring system measures the ability to perform daily activities, with a score of 0 indicating normal function and a score of 3 signifying a loss of that function. The total score can vary from 0 to 24, where a higher score signifies a greater level of impairment.
The findings showed a significant and favorable difference in the MG-ADL total score change from the baseline in the groups treated with rozanolixizumab (7 mg/kg and ≈10 mg/kg dose levels), with an improvement of 3.4 points at either dose compared to 0.8 points in the placebo-treated group.
Furthermore, a grading system that evaluates muscle weakness showed a statistically significant difference favoring rozanolixizumab. The change in total score from the baseline was -5.4 points and -6.7 points in the groups treated with rozanolixizumab at approximately 7 mg/kg and 10 mg/kg dosage levels, respectively. This was in contrast to the -1.9 points observed in the group treated with a placebo.
“Building on our decades of experience in neurology and immunology, we are proud to support the MG community with solutions to help improve patient lives, including a new FDA-approved treatment, education and support,” said Iris Loew-Friedrich, executive VP and chief medical officer at UCB, in the news release. “The approval following priority review of rozanolixizumab-noli is a testament to this medicine’s potential as a generally well-tolerated treatment option that is targeted to the individual needs of patients.”
The most frequently reported adverse reactions, occurring in at least 10 percent of patients, included headache, infections, diarrhea, fever, hypersensitivity reactions and nausea. Despite these common adverse reactions, the study indicated that Rystiggo was well-tolerated by patients.
Rystiggo will be commercially available in the US during the third quarter of 2023 with a list price of approximately $6,050 per vial.
Other New Drugs for Generalized Myasthenia Gravis Treatment
Several medications have recently secured FDA approval for the treatment of gMG. Argenx, a global immunology company, received FDA approval in 2021 for their drug Vyvgart (efgartigimod) for gMG. Vyvgart, a neonatal Fc receptor blocker, is recommended for adult patients with gMG who have tested positive for AChR antibodies. The FDA’s approval was predicated on the favorable results from the global Phase III ADAPT trial, which showed a significantly higher response rate on the MG-ADL scale among anti-AChR antibody-positive gMG patients treated with efgartigimod compared to those given a placebo (68 percent versus 30 percent).
In addition, AstraZeneca received FDA approval last year for their drug Ultomiris (ravulizumab) for the treatment of gMG. Ultomiris, a long-acting C5 complement inhibitor, offers immediate, complete and sustained complement inhibition by targeting the C5 protein in the terminal complement cascade, a part of the body’s immune system. The FDA’s approval of Ultomiris was based on the positive results from the CHAMPION-MG Phase III trial, where ravulizumab outperformed the placebo in the primary endpoint, which evaluated the change from baseline in the MG-ADL total score at Week 26.