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

ARGX-113-2010 is an open-label extension study with the aim to provide supporting evidence that efgartigimod PH20 SC is a safe and effective long-term treatment for bullous pemphigoid (BP), providing symptom control and eventually remission, while also reducing the cumulative exposure to oral corticosteroids (OCS).All participants who complete the end-of-treatment period (EoTP) visit at week 36 in ARGX-113-2009 will be invited to enroll.In ARGX-113-2009, participants received efgartigimod PH20 SC or placebo with concurrent OCS, or rescue therapy (without efgartigimod PH20 SC or placebo). Depending on their clinical status at the time of rollover into ARGX-113-2010, participants may stop, continue or initiate efgartigimod PH20 SC treatment. In ARGX-113-2010, participants will stop efgartigimod PH20 SC treatment when they achieve complete remission (CR) or partial remission (PR) while being off other concurrent BP therapy for at least 8 weeks. Participants not in CR or PR while off OCS for ≥8 weeks and not on rescue therapy will either start or continue efgartigimod PH20 SC treatment, while maintaining the treatment allocation of ARGX-113-2009 blinded. Participants may also be retreated with efgartigimod PH20 SC after a relapse. In this study, loading doses of 2000 mg (on day 1 and day 8 of a treatment course) and weekly maintenance doses of 1000 mg will be used.

Inclusion Criteria:Has completed the week 36 visit of ARGX-113-2009Is capable of providing signed informed consent and complying with protocol requirementsAgrees to use contraceptive measures consistent with local regulations and the following:Male participants: An acceptable method of contraception is a condom. All nonsterilized male participants must use this method from signing of the ICF until the date of the last dose of IMPWomen of childbearing potential (WOCBP) must have a negative urine pregnancy test at baseline before receiving IMP. WOCBP must use one of the contraception methods described in the protocol from signing the ICF until the last dose of IMPExclusion 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 riskKnown hypersensitivity to IMP or 1 of its excipients