WEST PALM BEACH, FLA. – Compared with placebo, inebilizumab reduces the risk of attacks, the risk of disability worsening, the number of hospitalizations, and the number of new MRI lesions in patients with neuromyelitis optica spectrum disorder (NMOSD), according to a study presented at the meeting held by the Americas Committee for Treatment and Research in Multiple Sclerosis. The drug’s efficacy was sustained for one year in the study, and the treatment had an acceptable safety profile.

“Multiple lines of evidence suggest that NMO is predominantly a B-cell–mediated disorder,” said Bruce Cree, MD, PhD, professor of neurology at the University of California, San Francisco, Weill Institute for Neurosciences. Inebilizumab depletes B cells and reduces inflammatory disease activity in NMO potentially by altering immune networks that are dependent on B cells for cytokine production or antigen presentation.” Inebilizumab is an anti-CD19 monoclonal antibody.

Dr. Cree and colleagues conducted a randomized, controlled trial called N-MOmentum to characterize the long-term efficacy and safety of inebilizumab in patients with NMOSD. The investigators randomized patients with NMOSD to inebilizumab or placebo monotherapy in a 3:1 ratio for 6.5 months. The study’s primary outcome was the time to the first adjudicated attack. Patients who had an adjudicated attack or completed the trial could receive inebilizumab in an ongoing open-label extension.

The study was conducted at 99 sites in 25 countries. In all, 230 patients were randomized and dosed (174 received inebilizumab, and 56 received placebo). About 91% of the population was aquaporin-4-IgG–positive (AQP4-IgG+), and 91% was female. The population’s mean age at baseline was 43 years. The population’s median baseline Expanded Disability Status Scale score was approximately 3.5, and the range was from 0 to 8.0. Approximately 50% of participants were white, 20% were Asian, and 9% were of African descent. “The demographic profile is similar to that of many published studies,” said Dr. Cree.

Because of clear evidence of efficacy, the independent data monitoring committee recommended that the study be stopped early. In the randomized, controlled trial, inebilizumab reduced the risk of attack by 77.3% among AQP4-IgG+ patients and by 72.8% in the total population. The number needed to treat for 6.5 months to prevent one attack was 3.2 for the AQP4-IgG+ group and 3.7 for the total population.

Furthermore, inebilizumab significantly reduced the risk of worsening disability, the number of new MRI lesions, and NMOSD-related hospitalizations. After 1 year on inebilizumab, 85% of patients were free of an NMOSD attack. In safety analyses that combined data from the randomized, controlled trial and interim data from the open-label extension, the mean duration of inebilizumab treatment was 1.5 years.

“The rapid effect of inebilizumab on attack prevention is not mediated by decreasing AQP4-IgG, although it is possible that long-term inebilizumab treatment might eventually reduce AQP4-IgG production,” said Dr. Cree.

The most common adverse events (AEs) were urinary tract infection (UTI, 19.6%), nasopharyngitis (12.9%), and infusion-related reactions (IRRs, 11.6%). IRRs were most common with the first infusion. The proportion of inebilizumab-treated patients with IgG levels below the lower limit of normal was 7.5% at 1 year and 13.4% at 2 years. Serious AEs occurred in 12% of patients, and UTI was the most common (2.2%). Two patients died in the open-label extension; one death resulted from NMOSD, and one from new presumed inflammatory brain lesions of undetermined etiology.

“The open-label results show a striking durability of treatment effect,” said Dr. Cree. “Most of the attacks that occurred during the open-label extension occurred early on, suggesting that the risk of attack decreases with duration of B-cell depletion. The open-label study also is important for assessing the longer-term AE profile of inebilizumab treatment. One potentially important observation from the open-label extension is that the extent of B-cell depletion correlates with reduced attack risk. Approximately 95% of participants with deep B-cell depletion were free of attacks. Participants who either incompletely depleted B cells or who began to reconstitute B cells more rapidly were at increased risk of attack. Therefore, by monitoring B-cell counts in inebilizumab-treated patients, it may be possible to further reduce the risk of attack in patients who partially deplete, or replete B cells early, with an extra inebilizumab treatment.”

Viela Bio, which is developing inebilizumab, and MedImmune sponsored the study. Dr. Cree has received compensation for consulting services that he provided to Alexion, Atara, Biogen, EMD Serono, Novartis, and TG Therapeutics.

egreb@mdedge.com

SOURCE: Cree BA et al. ACTRIMS 2020. Abstract P207.

Inebilizumab benefits patients with NMOSD