In the past several years, a deeper understanding of the myasthenia gravis disease process has enabled the development of many new targeted medications that act quickly and with fewer side effects. Now for the first time, people with MG have a new treatment option that doesn’t require a trip to a medical provider or infusion center.
On October 17, the U.S. Food and Drug Administration (FDA) approved the targeted C5 complement inhibitor Zilbrysq (zilucoplan) for generalized myasthenia gravis (gMG) in adults who are anti-acetylcholine receptor (AChR) antibody-positive, according to a press release from UCB, the manufacturer of the drug.
New Drug Offers Freedom and Flexibility
For people living with gMG, the unpredictable nature of the severity and frequency of symptoms such as muscle weakness and fatigue can be debilitating and can have a substantial impact on many aspects of their day-to-day lives, says lead investigator in the phase 3 clinical trial for Zilbrysq (the RAISE trial), James F. Howard, MD, distinguished professor of neuromuscular disease and professor of neurology, medicine, and allied health at the University of North Carolina Chapel Hill School of Medicine.
For a broad population of AChR antibody-positive gMG, Zilbrysq offers many benefits, including patient choice and patient freedom, says Dr. Howard.
“As the only self-administered complement inhibitor, the patient is no longer wedded to an infusion center, clinic, or home infusion service to receive an IV administration of the drug either at two-week or an eight-week interval,” he says. The daily subcutaneous injection is given in the fatty tissue, just under the skin.
Additionally, the medication may be stored at room temperature, which allows the patient to travel without concern as to when and where the next IV infusion will be, says Howard. “They can pack the syringes in the suitcase and go!” he adds.
In addition to the flexibility that Zilbrysq offers, the drug has shown remarkable promise for individuals with generalized myasthenia gravis in the clinical trials, says Rachana Gandhi Mehta, MD, a neurologist at Atrium Health Wake Forest Baptist in Winston Salem, North Carolina, who was not involved in the approval of the drug.
“Rapid symptom improvements were observed as early as one week, with significant benefits by Week 12,” Dr. Mehta says.
Debilitating Weakness and Fatigue Common People With MG
Myasthenia gravis is a chronic autoimmune neuromuscular disease that causes weakness in the skeletal muscles, which are the muscles that connect to your bones and contract to allow body movement in the arms and legs and allow for breathing.
About 20 in every 100,000 people have MG, and more than 70,000 people are diagnosed with the disease in the United States, according to the Myasthenia Gravis Foundation of America.
In people with gMG, weakness is commonly experienced during physical exertion, which can significantly limit day-to-day activities, says Mehta. “Patients frequently report symptoms such as double vision and drooping of the eyes, particularly when engaging in prolonged activities like reading, watching TV, driving, or working on a computer. Even simple tasks like walking, climbing stairs, rising from a seated position, taking showers, dressing, combing hair, brushing teeth, and shaving can pose challenges due to the weakness in limb muscles,” she says.
Furthermore, myasthenia gravis can also affect bulbar muscles, leading to difficulties in swallowing, chewing, speaking, and breathing, says Mehta.
Zilbrysq Offers Improvements in Symptoms and Function
The primary endpoint for the RAISE study, published in May 2023 in The Lancet Neurology, was change from baseline to week 12 in the myasthenia gravis activities of daily living (MG-ADL) score, an eight-item, patient-reported outcome measure assessing MG symptoms and functional activities related to activities of daily living such as breathing, talking, swallowing, and being able to rise from a chair.
Each of the eight items is measured, with a score of 0 indicating normal function and a score of 3 signifying the most severe loss of that function. The total score can vary from 0 to 24, and a higher score signifies a greater level of impairment.
The efficacy of Zilbrysq was also measured using the quantitative myasthenia gravis (QMG) total score, which is a 13-item categorical grading system that assesses muscle weakness. Each item is assessed on a 4-point scale where a score of 0 represents no weakness and a score of 3 represents severe weakness. A total possible score ranges from 0 to 39, where higher scores indicate more severe impairment.
At week 12, treatment with Zilbrysq demonstrated a statistically significant improvement from baseline compared with placebo for MG-ADL total score and QMG total score, with improvements seen as early as one week.
“Zilbrysq’s rapid onset of action and overall good tolerability make it particularly beneficial for patients with moderate to severe generalized myasthenia gravis by providing quick symptom control and improving their quality of life,” says Mehta.
Zilbrysq Could Improve Management of MG
The ability for patients to manage their treatment at home has benefits that go beyond independence and convenience, she says.
“It effectively resolves pressing challenges in myasthenia gravis management, such as the delays in starting new infusions for generalized MG patients, caused by extended wait times for infusion center appointments and rescheduling issues, thus ensuring timely treatment,” says Mehta.
Administering the treatment at home also reduces the risk of exposure to hospital-acquired infections, improving patient safety, she adds.
An additional benefit of Zilbrysq is that it’s a small molecule, which makes it different from other C5 inhibitors, which are full-size antibodies, says Howard. As a peptide, it can be used at the same time as intravenous immunoglobulin and plasma exchange, treatments given during myasthenic crises, or periods of symptom worsening.
More Medication Options Needed for MG
Zilbrysq is one of many new medications for MG that have been approved recently, says Charles Cho, MD, clinical professor and neurologist at Stanford Neuroscience Health Center in Palo Alto, California, who was not involved in the phase 3 clinical trials.
“In addition, there are a dozen other older medications that are still widely used for MG, so these additions help and give more options, he says.
“The unmet need in MG was the refractory patient who had failed multiple medications, or had side effects or tolerance issues. And since MG is a lifelong disease process that degrades over time, most patients will require switching to many meds over decades,” says Dr. Cho.
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Safety and Side Effects of Zilbrysq
The drug is overall well-tolerated, says Mehta. The most frequently reported treatment-related side effects, according to UCB, include injection-site bruising, diarrhea, and injection-site pain.
Zilbrysq affects part of the immune system and may lower a person’s ability to fight certain infections. The drug increases the likelihood of getting serious and life-threatening meningococcal infections.
People must complete or update two types of meningococcal vaccines (for both serogroup B infections and serogroup A, C, W, and Y infections) at least two weeks before taking their first dose of Zilbrysq.
How to Access Zilbrysq
The drug is expected to be available by the end of 2023 through a program called the Zilbrysq REMS. Before prescribing the medication, the healthcare provider must:
- Enroll in the Zilbrysq REMS.
- Counsel the patient about the risk of meningococcal infection.
- Provide information to the patient about the risks, signs, and symptoms of meningococcal infection.
- Make sure the patient is vaccinated with two types of meningococcal vaccines and, if needed, gets revaccinated with the meningococcal vaccines.
The company has not disclosed what the cost of Zilbrysq will be.