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 Trial

BACKGROUND AND PURPOSE: Efgartigimod, a neonatal Fc receptor inhibitor, reduces IgG recycling and thus decreases pathogenic IgG autoantibody levels. This subpopulation analysis aimed to assess the efficacy, safety, and tolerability of subcutaneous efgartigimod PH20 in Chinese participants with chronic inflammatory demyelinating polyneuropathy (CIDP). METHODS: ADHERE was a multistage, randomised-withdrawal, placebo-controlled phase II trial in adult participants with active CIDP. Eligible participants received open-label treatment with efgartigimod weekly for ≤12 weeks (Stage A) and those with confirmed evidence of clinical improvement (ECI) were randomised to receive double-blind treatment with efgartigimod or placebo weekly for ≤48 weeks (Stage B). Primary endpoints were proportion of participants with confirmed ECI (Stage A) and time to clinical deterioration as measured by adjusted Inflammatory Neuropathy Cause and Treatment score (Stage B). This descriptive analysis reports the results from the Chinese subpopulation. RESULTS: ADHERE enrolled 58 participants from mainland China for Stage A and of those, 47 were randomised (21 efgartigimod, 26 placebo) for Stage B. In Stage A, 45 (77.6%; 95% confidence interval [CI], 64.7%-87.5%) participants achieved confirmed ECI. In Stage B, median time to clinical deterioration was not reached with efgartigimod vs. 113.0 days (95% CI, 43.0-181.0 days) with placebo (hazard ratio, 0.313; 95% CI, 0.109-0.905). Across stages, most adverse events were mild or moderate, and no death occurred. No adverse events led to treatment discontinuation. CONCLUSIONS: Subcutaneous efgartigimod PH20 demonstrated clinical response and lowered the risk of clinical deterioration compared to placebo in Chinese participants with CIDP, while maintaining favourable safety and tolerability profiles.