Tocilizumab is safe and tolerable and reduces C-reactive protein concentrations in the plasma and cerebrospinal fluid of ALS patients

Introduction/aims We tested safety, tolerability, and target engagement of tocilizumab in amyotrophic lateral sclerosis (ALS) patients. Methods Twenty-two participants, whose peripheral blood mononuclear cell (PBMC) gene expression profile reflected high messenger ribonucleic acid (mRNA) expression of inflammatory markers, were randomized 2:1 to 3 tocilizumab or placebo treatments (weeks 0, 4, and 8; 8 mg/kg intravenous). Participants were followed every 4 weeks in a double-blind fashion for 16 weeks and assessed for safety, tolerability, plasma inflammatory markers, and clinical measures. Cerebrospinal fluid (CSF) was collected at baseline and after the third treatment. Participants were genotyped for Asp358 Ala polymorphism of the IL6R gene. Results Baseline characteristics, safety, and tolerability were similar between treatment groups. One serious adverse event was reported in the placebo group; no deaths occurred. Mean plasma C-reactive protein (CRP) level decreased by 88% in the tocilizumab group and increased by 4% in the placebo group (-3.0-fold relative change, P Discussion Tocilizumab treatment was safe and well tolerated. PBMC gene expression profile was inadequate as a predictive or pharmacodynamic biomarker. Treatment reduced CRP levels in plasma and CSF, with CSF effects potentially dependent on IL6R Asp358 Ala genotype. IL-6 trans-signaling may mediate a distinct central nervous system response in individuals inheriting the IL6R C allele. These results warrant further study in ALS patients where IL6R genotype and CRP levels may be useful enrichment biomarkers. Classification of evidence This study provides Class I evidence that tocilizumab therapy is safe and well tolerated in ALS patients with high mRNA expression of inflammatory markers. Clinical trial registration Registered at ClinicalTrials.gov (NCT02469896). This article is protected by copyright. All rights reserved.