Rituximab reinfusion after 9 months can suppress neuromyelitis optica spectrum disorder (NMOSD) relapses with an annualized relapse rate of 0.035 counts per person-years, according to results from a clinical trial of compassionate use of rituximab published in Multiple Sclerosis and Related Disorders.
The trial called RIN-2 was the open-label extension of another multicenter, randomized, double-blind, placebo-controlled trial of rituximab called RIN-1. During the RIN-2 study, rituximab was infused repeatedly and CD19 and CD 20-positive B cell lymphocyte subsets were monitored monthly from 24 weeks after an infusion.
Most patients from the RIN-1 study (87%) enrolled in the RIN-2 study. They received rituximab between 1 to 5 times at an interval of 9.5 months on average. The patients were observed for a mean period of 20.5 months.
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Three patients dropped out of the trial because of withdrawals (2 patients) or adverse events (1 patient). During the trial, 2 patients had NMOSD relapses. The annualized relapse rate was 0.035 counts per person-years. In the placebo arm of the RIN-1 study, this rate was 0.321, around 10 fold higher.
There were a total of 14 severe adverse events in 18% of patients and 156 adverse events. Of these, 135 were grade 1, 11 were grade 2, and 10 were grade 3.
“Under B cell monitoring, the interval of [rituximab] re-infusion was elongated to nine months, and [neuromyelitis optica] relapses were suppressed with 0.035 of [annualized relapse rate],” the researchers wrote.
Rituximab is a B-cell depleting therapy, which targets CD20 and depletes B cell lineage cells from late pro-B cells through early plasmablasts. Even though it has been used to manage NMOSD for the past 15 years, rituximab had not yet been approved by the US Food and Drug Administration to treat the condition.
Tahara M, Oeda T, Okada K, et al. Compassionate open-label use of rituximab following a randomised clinical trial against neuromyelitis optica (RIN-2 study): B cell monitoring-based administration. Mult Scler Relat Disord. Published online March 6, 2022. doi:10.1016/j.msard.2022.103730