Rituximab Improves Muscle Recovery for Some With Refractory Anti-HMGCR Myopathy

One-third of patients with refractory anti-HMGCR antibodies had improved strength or other evidence of improved disease activity after rituximab treatment.

Rituximab may improve muscle strength and disease activity in patients with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) immune-mediated necrotizing myopathy, according to results from a study published in The Journal of Rheumatology.

Researchers retrospectively analyzed data from a cohort of 9 patients who received rituximab from 2009 to 2017. The majority of patients were given a single, 1-g dose of rituximab administered intravenously, followed by a second dose given 2 weeks later, with subsequent doses given every 6 months thereafter if indicated by the prescribing physician. The investigators evaluated muscle strength, using the Medical Research Council-5 scale and manual muscle testing.

After analysis, the researchers found that approximately one-third of patients showed stable or improved muscle strength with testing. In addition, treatment with rituximab allowed for cessation of intravenous immunoglobulin therapy and corticosteroid dose reduction in 2 patients from the cohort.

The primary study limitation was the use of multiple drug therapies, which limited attribution of the clinical benefits solely to rituximab.

“[Rituximab] was clearly ineffective in some patients, yet may have demonstrated a beneficial effect in one-third of patients with refractory anti-HMGCR [immune-mediated necrotizing myopathy],” the researchers wrote.

“A prospective randomized trial is needed to confirm these findings and clarify the role of [rituximab] in the treatment of patients with shorter disease duration,” they concluded.

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Landon-Cardinal O, Allenbach Y, Soulages A, et al. Rituximab in the Treatment of Refractory Anti-HMGCR Immune-mediated Necrotizing Myopathy [published online December 15, 2018]. J Rheumatol. doi: 10.3899/jrheum.171495