A Phase 3 Study to Evaluate the Long-term Safety, Tolerability and Efficacy of Efgartigimod PH20 SC in Adult Participants With Bullous Pemphigoid

The purpose of this study is to evaluate the safety of efgartigimod PH20 SC over a longer period of time in adult participants with moderate-to-severe bullous pemphigoid (BP) who have completed ARGX-113-2009 study. The study will also evaluate the efficacy of efgartigimod PH20 SC.

Eligible participants can roll over from the main study (ARGX-113-2009) to this open-label extension study (ARGX-113-2010). The study consists of a treatment period of up to 48 weeks in which participants could receive efgartigimod PH20 SC according to their clinical status. After the first 5 visits, the participants will visit the study centres at least once every 4 weeks. The participants who are not receiving efgartigimod PH20 SC (after the main study or currently on the study), will enter an observation period with study visits at least once every 8 weeks. If the participant relapses, they can re-enter the treatment period where they will receive efgartigimod PH20 SC. The treatment and observation period is followed by a follow-up period of 8 weeks. Oral or topical corticosteroids can be administered at the investigator's discretion.