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

An Open-label Extension Study of ARGX-113-2009 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.

Inclusion Criteria:

• Has completed the week 36 visit of ARGX-113-2009
• Is capable of providing signed informed consent and complying with protocol requirements
• Agrees to use contraceptive measures consistent with local regulations and the following: Women of childbearing potential must have a negative urine pregnancy test at baseline before receiving the study drug and must use one of the contraception methods described in the protocol from signing the ICF until the last dose of the study drug

Exclusion Criteria:

• Clinically significant disease, recent major surgery (within 3 months of baseline), or intends to have surgery during the study; or any other medical condition that, in the investigator's opinion would confound the results of the study or put the participant at undue risk
• Known hypersensitivity to the study drug or 1 of its excipients
• Permanently discontinued IMP in ARGX-113-2009 due to an adverse event (AE) considered related to the study drug and for whom the benefit/risk balance is not considered positive