A Study of Empasiprubart as Add-On Therapy to IVIg in Adult Participants With Guillain-Barré Syndrome

The main purpose of this study is to learn whether empasiprubart, when given in addition to intravenous immunoglobulin (IVIg), helps adults with Guillain-Barré syndrome (GBS) recover and whether it is safe. About 63 participants will be assigned by chance to receive either empasiprubart or placebo by intravenous infusion; all participants will also receive IVIg. The study includes screening for up to 72 hours, study treatment through Day 12, and follow-up through Week 67 (15 months after the last dose of study treatment). Participation lasts up to 67 weeks.

Inclusion Criteria: * Clinically diagnosed with Guillain-Barré syndrome (GBS) according to NINDS (National Institute of Neurological Disorders and Stroke) diagnostic criteria * GBS-related weakness beginning within 7 days before the first study treatment * GBS Disability Scale (GBS-DS) score of 3, 4, or 5 at screening and baseline * Was able to walk approximately 10 m or more without assistance before the onset of GBS symptoms * Agrees to receive antibiotic prophylaxis against N. meningitidis and S. pneumoniae for the first 90 days of the study or until a completed vaccination schedule against these bacterial pathogens per local guidelines has been shown. Exclusion Criteria: * History of a previous GBS episode or diagnosis of an atypical GBS variant * Clinical diagnosis of systemic lupus erythematosus (SLE) or known complement deficiency * Autoimmune or neuromuscular diseases or medical conditions (eg, clinically significant renal, hepatic, cardiac, pulmonary, hematologic, or neurological conditions or clinically significant laboratory abnormalities) that would interfere with an accurate assessment of clinical symptoms of GBS, confound the study results, or put the participant at undue risk * IVIg therapy contraindications or another medical condition that, in the opinion of the investigator, would make IVIg administration unsafe * Recent treatment with IVIg or plasma exchange (PLEX), or recent use of certain immune-modulating or immunosuppressive therapies