A Phase 2/3 Study of Efgartigimod PH20 SC in Adult Participants With Bullous Pemphigoid

Primary Outcome Measures

1. Number of Participants With CRoff at Week 36
   CRoff = complete remission while receiving efgartigimod PH20 SC or placebo and being off oral corticosteroid therapy for at least 8 weeks. Complete remission is defined as the absence of new lesions, complete healing of existing lesions and absence of pruritus.

Secondary Outcome Measures

1. Cumulative OCS Dose
   OCS = oral corticosteroid
2. Number of Participants Who Achieve an IGA-BP Score of 0 While Off OCS Therapy for ≥8 Weeks at Week 36
   IGA-BP = Investigator Global Assessment of Bullous Pemphigoid. IGA-BP scores range from 0-4, with a higher score representing severe BP. OCS = oral corticosteroid
3. Number of Participants With CDA Who Remained Free of Relapse Through Week 36
   Control of disease activity (CDA) is defined as the point at which new lesions ceased to form, established lesions began to heal, and pruritic symptoms started to abate. Relapse is defined as the appearance of 3 or more new lesions a month or at least 1 large lesion that did not heal within 1 week, or extension of established lesions or daily pruritus in a participant who had achieved CDA.
4. Number of Participants With CRmin at Week 36
   CRmin = complete remission receiving minimal oral corticosteroids for at least 8 weeks. Minimal oral corticosteroid (OCS) therapy is defined as ≤0.1 mg/kg/day of prednisone (or equivalent).
5. Change From Baseline to Week 36 in the 24-Hour Average Itch NRS Score
   Itch NRS = Itch Numerical Rating Scale. The Itch NRS scores range from 0-10 with 10 representing the worst imaginable itch.
6. Changes From Baseline in the BPDAI Total Activity Score
   BPDAI = Bullous Pemphigoid Disease Area Index (BPDAI) Total Activity Score is a tool to objectively measure disease activity. BPDAI scores range from 0 to 360 with a higher score indicating more severe disease (max 240 for total skin activity and 120 for mucosal activity).
7. Time to CDA
   CDA = control of disease activity, the point at which new lesions ceased to form, established lesions began to heal, and pruritic symptoms started to abate.
8. Time to CR
   CR = complete remission, the absence of new lesions, complete healing of existing lesions, and absence of pruritus.
9. Time to CRmin
   CRmin = complete remission, the absence of new lesions, complete healing of existing lesions, and absence of pruritus while being on minimal dose of OCS for ≥8 Weeks. OCS = oral corticosteroid. Minimal OCS therapy is defined as an oral prednisone dosage of ≤0.10 mg/kg/day (or equivalent).
10. Time to CRoff/PRoff
    CRoff= complete remission (the absence of new lesions, complete healing of existing lesions, and absence of pruritus) while receiving efgartigimod PH20 SC or placebo and being off oral corticosteroid therapy for at least 8 weeks. PRoff = partial remission (the presence of only new transient lesions) while receiving efgartigimod PH20 SC or placebo and being off oral corticosteroid therapy for at least 8 weeks.
11. Time to CRoff
    CRoff is defined as the absence of new lesions, complete healing of existing lesions, and absence of pruritus while being off OCS therapy for ≥8 weeks.
12. Time From CDA to Achieve Relapse
    CDA is defined as the point at which new lesions ceased to form, established lesions began to heal, and pruritic symptoms started to abate. Relapse is defined as the appearance of 3 or more new lesions a month or at least 1 large lesion that did not heal within 1 week, or extension of established lesions or daily pruritus in a participant who had achieved CDA.
13. Number of Participants Who Receive Rescue Therapy Before Week 36
14. The AIS From the GTI
    The Aggregate Improvement Score (AIS) from the Glucocorticoid Toxicity Index (GTI) can range from -346 to 439 with a higher score representing greater corticosteroid toxicity. If a study drug is effective at lowering greater corticosteroid toxicity over time, the score will be lower.
15. The CWS From the GTI
    The Cumulative Worsening Score (CWS) from the Glucocorticoid Toxicity Index (GTI) can range from 0 to 439 with a higher score representing greater corticosteroid toxicity.
16. EQ-5D-5L VAS Scores Over Time
    The EuroQol 5-Dimension 5-Level Visual Analog Scale (EQ-5D-5L VAS) scores range from 0-100 with 0 representing the worst health.
17. DLQI Scores Over Time
    Dermatology Life Quality Index (DLQI) assess the participant's perception of the impact of skin diseases on different aspects of their health-related QoL. Scores range from 0 to 30 with a higher score representing a worse quality of life.
18. ABQoL Scores Over Time
    Autoimmune Bullous Disease Quality of Life Index (ABQoL) questionnaire assesses the impact of Autoimmune Bullous Disease and their therapies on the daily life of patients. Scores range from 0 to 51 with a higher score representing a worse quality of life.
19. Efgartigimod Serum Concentrations
20. Percent Change of Total IgG Serum Levels From Baseline Over Time
21. Percent Change of Anti-BP180 and Anti-BP230 Antibodies From Baseline Over Time
22. Incidence of Antidrug Antibodies Against Efgartigimod and Antibodies Produced Against rHuPH20
23. Number of Participants (or Their Caregivers) Who Are Determined by Site Staff to be Sufficiently Competent in (Self-)Administering Efgartigimod PH20 SC