A phase 4 study is testing whether patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) can switch directly from intravenous immunoglobulin (IVIG) to subcutaneous efgartigimod PH20 without first experiencing disease worsening. The open-label trial, presented at the 2026 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Annual Meeting, enrolled 23 adults who had been stable on IVIG doses of 0.5 to 2 grams per kilogram every 3 to 6 weeks for at least three doses.
Participants transitioned to weekly subcutaneous efgartigimod PH20 at 1,000 milligrams for 12 weeks, beginning within one week of their last IVIG dose. The primary goal is to measure how many continue treatment through the full period. Secondary outcomes include changes in quality-of-life assessments, patient-reported disease improvement, treatment satisfaction, and safety profiles. A follow-up visit was scheduled four weeks after the final dose.
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This study builds on earlier findings from the phase 2 ADHERE trial, which demonstrated that subcutaneous efgartigimod reduced the risk of clinical deterioration in active CIDP. In that trial, 77.6% of Chinese participants showed confirmed clinical improvement during initial treatment, while those on placebo experienced deterioration at a rate of 61.5% compared to 28.6% for those continuing efgartigimod during withdrawal.
However, ADHERE required participants to show disease worsening before starting efgartigimod, leaving unanswered whether stable patients on IVIG could transition without first experiencing relapse. The phase 4 study directly addresses this gap by evaluating a direct switch in patients who remain stable on their current therapy.
