Zilbrysq’s safety, efficacy in real-world study mirror trial findings

Zilbrysq (zilucoplan) helped ease disease symptoms and improve quality of life for most people with generalized myasthenia gravis (gMG) in an expanded access program (EAP) in France, a study showed.

EAPs provide access to experimental therapies, or those already approved but not yet on the market, outside clinical trials.

The efficacy and safety profile of Zilbrysq seen in this real-world analysis were largely consistent with findings from the clinical trials that supported the treatment’s approvals, the researchers said.

The study, “Real-world effectiveness and safety of zilucoplan in patients with anti-AChR myasthenia gravis: A retrospective cohort study in France,” was published in the Journal of Neuromuscular Diseases. 

Myasthenia gravis is an autoimmune disease marked by self-reactive antibodies that interfere with the communication between nerve and muscle cells, resulting in symptoms like muscle weakness and fatigue. The most common MG-causing antibodies target a protein called acetylcholine receptor (AChR).

UCB’s Zilbrysq works to ease gMG symptoms by blocking activation of the complement cascade, a group of immune proteins that are activated by MG-driving antibodies and contribute to the disease.

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U.S. and European regulators approved Zilbrysq in 2023 to treat AChR-related gMG. The approvals were based on clinical trial data demonstrating that the therapy, which is self-administered once daily by under-the-skin injection, was better than a placebo at easing symptoms.

Because clinical trials are conducted under strict supervision with specific inclusion criteria, they generally don’t reflect the wider realities of real-world practice. Apart from one recent study from Italy, there’s little published data on the use of Zilbrysq in gMG patients in real-world settings, the researchers said.

“Little information is available on the impact of [Zilbrysq] with respect to its benefits and risks in everyday clinical practice, and further studies in the real-world treatment setting are necessary,” the researchers wrote.

The team retrospectively analyzed data from 48 adults with hard-to-manage gMG and anti-AChR antibodies who started Zilbrysq in combination with standard therapy in France’s EAP.

This EAP opened after Zilbrysq was approved by the European Medicines Agency, allowing certain patients to access the therapy during the nearly two years it took for the French Health Authorities to also clear the therapy for use.

Patients in this analysis had six-month data prior to Zilbrysq start and at least six months of follow-up data or until the end of the EAP, if it ended before six months of follow-up. A little more than half of the participants were men, and they had been living with the disease for a mean of 11.6 years.

Nine (18.8%) discontinued Zilbrysq before the EAP ended: three due to perceived lack of efficacy, four due to side effects, and two for unspecified reasons. One patient interrupted Zilbrysq treatment after experiencing a resolution of symptoms, but restarted it when symptoms reappeared.

Data were available for 91.7% of patients after one month and 80% after six months. Mean scores on the MG activities of daily living scale (MG-ADL), which measures the disease’s impact on day-to-day activities, decreased (improved) significantly from 7.4 at the study’s start to 2.5 after six months of Zilbrysq treatment.

About half of the patients with effective evaluations at six months achieved minimal symptom expression, or no to mild symptoms, as reflected by an MG-ADL score of 0 or 1.

Other measures of disease severity and MG-related quality of life showed similar trends of improvement following Zilbrysq treatment, with improvements observed as early as a month after starting therapy. These improvements  “were sustained up to six months,” the researchers wrote.

In the six months prior to starting Zilbrysq, nearly half of the participants (47.2%) were free from myasthenic crisis, a life-threatening complication marked by difficulty breathing due to weakness of muscles in the chest. During Zilbrysq treatment, 87.5% did not experience such crises.

The mean oral corticosteroid dose was significantly reduced after starting Zilbrysq, and about half of the patients had discontinued these medications. Corticosteroids are immunosuppressive medicines commonly used to help manage MG, but they can cause unpleasant side effects, especially when used at high doses for long durations.

Over the course of the EAP, 53 adverse events were reported in 15 patients (31.3%), with the most common being headache, nausea, and injection site pain. “Most of the adverse events were mild to moderate in severity and no serious adverse events were reported,” the researchers wrote.

“The findings of this observational, retrospective study in the real-world treatment are supportive of the effectiveness of [Zilbrysq] in patients with anti-AChR gMG,” and are “largely consistent” with previously reported findings from clinical trials and the Italian real-world study, the team concluded.