Phase 4 Study Evaluates Transition From IVIG to Subcutaneous Efgartigimod in CIDP

A phase 4 study is evaluating whether adults with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) who are stable on intravenous immunoglobulin (IVIG) can transition directly to subcutaneous efgartigimod PH20 (Vyvgart Hytrulo; argenx) without first experiencing disease worsening. The open-label, multicenter study (NCT06637072), presented at the 2026 American Association of Neuromuscular & Electrodiagnostic Medicine Annual Meeting, is designed to assess the feasibility, safety, and tolerability of this treatment transition.¹

Led by Arjun Seth, MD, assistant professor of neurology at Northwestern University Feinberg School of Medicine in Chicago, Illinois, the study enrolled 23 adults with CIDP who had received stable IVIG doses of 0.5 to 2 g/kg every 3 to 6 weeks for at least 3 doses. Following a screening period of up to 3 weeks, participants transitioned to efgartigimod PH20 1000 mg administered subcutaneously once weekly for 12 weeks, beginning within 1 week of their last IVIG dose. The primary end point is the proportion of participants who continue receiving efgartigimod PH20 throughout the treatment period.¹

Secondary end points include changes from baseline in quality-of-life assessments, patient-reported disease improvement and severity, treatment satisfaction, and safety and tolerability. Following the treatment period, participants could receive further treatment at their investigator's discretion, in accordance with routine clinical practice. A safety follow-up visit was scheduled for 4 weeks after the final study dose.¹

The phase 4 study builds on findings from the phase 2 ADHERE trial (NCT04281472), which evaluated subcutaneous efgartigimod PH20 in adults with active CIDP. ADHERE used a 2-stage design, with participants initially receiving open-label efgartigimod for up to 12 weeks, after which those achieving confirmed evidence of clinical improvement entered a randomized withdrawal phase comparing continued treatment with placebo. In the overall study, efgartigimod PH20 reduced the risk of clinical deterioration compared with placebo during the randomized-withdrawal phase.²

ADHERE detailed the trial's findings supporting efgartigimod as a treatment option for CIDP. A subsequent analysis of Chinese participants in ADHERE reported confirmed clinical improvement in 77.6% of participants during the initial treatment stage. During the randomized-withdrawal stage, clinical deterioration occurred in 28.6% of participants receiving efgartigimod PH20 vs 61.5% receiving placebo.³

However, ADHERE required participants to demonstrate disease worsening before initiating efgartigimod PH20, limiting its ability to address treatment transitions among patients who remain stable on IVIG. The phase 4 study is designed to address this clinical question by evaluating whether patients can switch to weekly subcutaneous efgartigimod PH20 without first experiencing disease deterioration.

REFERENCES
1. Seth A, Lerman A, Remmerie A, et al. Intravenous immunoglobulin to subcutaneous efgartigimod PH20 transition in chronic inflammatory demyelinating polyradiculoneuropathy: a phase 4 study in progress. Presented at: American Association of Neuromuscular & Electrodiagnostic Medicine Annual Meeting; September 29-October 2, 2026; Orlando, FL.
2. Lin J, Ding M, Wang Q, et al. Efficacy, Safety, and Tolerability of Subcutaneous Efgartigimod PH20 in Chinese Patients With Chronic Inflammatory Demyelinating Polyneuropathy: A Prespecified Subpopulation Analysis of the Multicentre, Randomised-Withdrawal, Double-Blind, Placebo-Controlled, Phase II ADHERE Tsafety, and tolerability of subcutaneous efgartigimod PH20 in Chinese patients with chronic inflammatory demyelinating polyneuropathy: a prespecified subpopulation analysis of the multicentre, randomised-withdrawal, double-blind, placebo-controlled, phase II ADHERE trial. J Clin Neurol. 2026;22(1):76-88. doi:10.3988/jcn.2025.0247
3. Allen JA, Lin J, Basta I, et al. Safety, tolerability, and efficacy of subcutaneous efgartigimod in patients with chronic inflammatory demyelinating polyradiculoneuropathy (ADHERE): a multicentre, randomised-withdrawal, double-blind, placebo-controlled, phase 2 trial. Lancet Neurol. 2024;23(10):1013-1024. doi:10.1016/S1474-4422(24)00309-0