New Phase 3 Trials to Test Empasiprubart Against Placebo, IVIG in CIDP

Empasiprubart, an investigational complement C2 inhibitor, is being evaluated in 2 global phase 3 trials designed to assess its efficacy and safety in adults with CIDP. Findings presented at the 2026 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Annual Meeting outlined the designs of the two studies, dubbed EMNERGIZE (NCT07091630) and EMVIGORATE (NCT06920004).¹

Led by Simon Rinaldi, MRCP(Neuro), PhD, professor of neurology and honorary consultant neurologist at the University of Oxford, and colleagues, the presentation detailed the trials' primary and secondary end points. Both studies will assess changes in the adjusted Inflammatory Neuropathy Cause and Treatment (aINCAT) disability score at week 24, with a reduction of at least 1 point from baseline specified as the primary end point. Secondary end points include changes in the Inflammatory Rasch-built Overall Disability Scale score, Medical Research Council sum score, dominant-hand grip strength, and Timed Up and Go performance.¹

EMNERGIZE Trial

EMNERGIZE will enroll approximately 160 adults with CIDP, with recruitment beginning in September 2025, and including participants across multiple international sites. Patients will be randomly assignedin a 2:1 ratio to receive intravenous empasiprubart or placebo over a 24-week double-blind treatment period. During the double-blind portion of the trial, patients will receive doses on days 1 and 8 followed by administration every 4 weeks through week 24. Participants completing this phase will transition into a long-term extension period consisting of a 4-week blinded rollover phase followed by a 23-month open-label treatment period and a subsequent 15-month safety follow-up.²

Eligible participants must meet 2021 European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) criteria for typical CIDP or selected CIDP variants, including motor, multifocal, focal, or distal forms of the disease. Investigators are enrolling patients with residual disability and evidence of active disease, including both treatment-naïve individuals and those willing to discontinue existing CIDP therapies before study entry.²

EMVIGORATE Trial

EMVIGORATE is a phase 3 trial that plans to enroll approximately 218 adults with CIDP across international study sites. Unlike EMNERGIZE, which compares empasiprubart with placebo, EMVIGORATE evaluates empasiprubart against maintenance intravenous immunoglobulin (IVIG) in patients already receiving stable IVIG treatment.³

Participants will be randomly assigned in a 1:1 ratio to receive intravenous empasiprubart plus an IVIG-matched placebo or continue their existing IVIG regimen with an empasiprubart-matched placebo during a 24-week double-blind, double-dummy treatment period. Following this phase, participants will transition to an open-label treatment period in which all participants receive empasiprubart, followed by a safety follow-up.³

Like EMNERGIZE, eligible participants for EMVIGORATE must meet the 2021 EAN/PNS criteria for typical CIDP or selected variants. Participants must have responded to IVIG within the previous 5 years, be receiving stable maintenance IVIG, and have residual disability and evidence of active disease. By studying this population, EMVIGORATE will assess whether empasiprubart may provide an alternative to continued IVIG treatment for patients with CIDP.³

Empasiprubart and Similarities Between Trials

Following the initial treatment period, both trials will include a 4-week double-blind rollover, a 23-month open-label treatment period, and a 15-month safety follow-up. The studies will evaluate empasiprubart in complementary populations, including adults with CIDP receiving maintenance IVIG, to further characterize its efficacy and safety across both treatment settings.

Empasiprubart, formerly known as ARGX-117, is a humanized IgG1 monoclonal antibody designed to bind complement component C2 and inhibit activation of the classical and lectin complement pathways while leaving the alternative pathway intact. The antibody is engineered to bind the neonatal Fc receptor (FcRn), which is intended to extend its half-life through recycling and reduce its degradation. By targeting C2, empasiprubart is being developed to modulate complement-mediated inflammation implicated in autoimmune conditions, including CIDP.⁴

REFERENCES
1. Rinaldi S, Brannagan T, Doneddu PE, et al. EMPASIPRUBART VERSUS PLACEBO (EMNERGIZE) OR IMMUNOGLOBULIN (EMVIGORATE) IN CHRONIC INFLAMMATORY DEMYELINATING POLYRADICULONEUROPATHY: STUDY DESIGNS. Presented at: 2026 AANEM Annual Meeting and MGFA Scientific Session; September 29-October 2, 2026; Orlando, FL.
2. Rinaldi S, Brannagan T, Doneddu PE, et al. Empasiprubart Versus Placebo in Chronic Inflammatory Demyelinating Polyradiculoneuropathy: EMNERGIZEPhase 3 Study Design. Presented at: Peripheral Nerve Society (PNS) Annual Meeting; June 13-17, 2026; Maastricht, Netherlands.
3.EMVIGORATE: A phase 3 study of empasiprubart in participants with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Argenx. Accessed September 29, 2026. https://clinicaltrials.argenx.com/emvigorate
4. Empasiprubart.Argenx. News Release.2026. Accessed September 29, 2026. https://argenx.com/pipeline/empasiprubart