Satralizumab (Enspryng®) treatment may be linked with severe febrile neutropenia in patients with neuromyelitis optica spectrum disorder (NMOSD) based on the case of a patient from Argentina who developed it 2 weeks after the start of treatment, according to a study.

These findings suggest that analytic control for satralizumab should be used to closely monitor neutrophil count and prevent complications at week 2, instead of the recommended 4 weeks, Edgar Carnero Contentti, of the Hospital Alemán in Buenos Aires, Argentina, and colleagues noted.

Although mild neutropenia has been reported in 15% of patients being treated with satralizumab in a phase 3 clinical trial, no cases of severe neutropenia have been reported worldwide, the authors noted.  The multicenter, randomized, double-blind, placebo-controlled trial tested the safety, efficacy, pharmacodynamic, pharmacokinetic, and immunogenic profiles of the treatment in addition to baseline immunosuppressive treatment in patients with NMOSD, they added.

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The case study is published in the Multiple Sclerosis Journal

The case presented here is that of a 24-year-old female patient with aquaporin-4 (AQP-4) antibody-positive NMOSD who developed severe neutropenia 2 weeks after satralizumab was added to her azathioprine treatment.

NMOSD is a rare and chronic inflammatory disease of the central nervous system. It is characterized by the production of autoantibodies against the AQP-4 water channel found on astrocytes in most cases, leading to severe optic neuritis and/or myelitis. 

Satralizumab is an interleukin-6 (IL-6) receptor antagonist. Its exact mechanism of action is not well understood, but it is thought to involve the inhibition of IL-6-mediated signaling by binding to soluble and membrane-bound IL-6 receptors.

Satralizumab is approved by the US Food and Drug Administration for the treatment of adults with NMOSD.


Pestchanker C, Diaconchuk M, Lopez P, et al. Severe febrile neutropenia associated with satralizumab in an Argentinian neuromyelitis optica spectrum disorder patient. Mult Scler. Published online November 27, 2022. doi:10.1177/13524585221137231