A Study to Assess the Long-term Safety and Efficacy of a Subcutaneous Formulation of Efgartigimod in Adults With Active Idiopathic Inflammatory Myopathy

The main purpose of this study is to measure the long-term safety and tolerability of efgartigimod PH20 SC in adult participants with Idiopathic Inflammatory Myopathy (IIM) who previously participated in ARGX-113-2007. The study consists of a treatment period where participants will receive efgartigimod PH20 SC for up to 51 months. The treatment period will be followed by a treatment-free safety follow-up period of 56 days.

NCT Number	NCT05979441
Lead Sponsor	argenx
Conditions	Myositis, Active Idiopathic Inflammatory Myopathy, Dermatomyositis, Polymyositis, Immune-Mediated Necrotizing Myopathy, Antisynthetase Syndrome
Enrollment	240 participants
Start Date	2023-09-12
Primary Completion	2028-09 (estimated)
Study Completion	2028-09 (estimated)
Updated on ClinicalTrials.gov	2026-07-21