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

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

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.

Severity will be assessed using the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events ( CTCAE) definitions (current version): Grade 1 (mild) to Grade 5 (death related to adverse event)

Severity will be assessed using the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events ( CTCAE) definitions (current version): Grade 1 (mild) to Grade 5 (death related to adverse event)

Proportion of participants achieving complete remission or partial remission while off oral corticosteroids for ≥ 8 weeks

Proportion of participants achieving complete remission or partial remission while off oral corticosteroids for ≥ 8 weeks

Proportion of participants achieving complete remission while on minimal oral corticosteroids therapy for ≥ 8 weeks

Minimal oral corticosteroid therapy is defined as ≤0.10 mg/kg/day of prednisone (or an equivalent dose of another oral corticosteroid)

Proportion of participants achieving complete remission while off both oral corticosteroids and efgartigimod PH20 SC for ≥ 8 weeks

Proportion of participants achieving complete remission while off both oral corticosteroids and efgartigimod PH20 SC for ≥ 8 weeks

Proportion of participants achieving complete remission or partial remission while off both oral corticosteroids and efgartigimod PH20 SC for ≥ 8 weeks

Proportion of participants achieving complete remission or partial remission while off both oral corticosteroids and efgartigimod PH20 SC for ≥ 8 weeks

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 2, 4, 8, 16, 24, 32, 40, 48 and 56.

For participants continuing/starting efgartigimod PH20 SC treatment at rollover or relapse: at weeks 0, 2, 4 and 8 and then every 4 weeks until efgartigimod stop, every 8 weeks after efgartigimod stop and at weeks 48, 52 and 56.

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 2, 4, 8, 16, 24, 32, 40, 48 and 56.

For participants continuing/starting efgartigimod PH20 SC treatment at rollover or relapse: at weeks 0, 2, 4 and 8 and then every 4 weeks until efgartigimod stop, every 8 weeks after efgartigimod stop and at weeks 48, 52 and 56.

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 2, 4, 8, 16, 24, 32, 40, 48 and 56.

For participants continuing/starting efgartigimod PH20 SC treatment at rollover or relapse: at weeks 0, 2, 4 and 8 and then every 4 weeks until efgartigimod stop, every 8 weeks after efgartigimod stop and at weeks 48, 52 and 56.

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index - Aggregate Improvement Score (GTI-AIS) over time

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index - Aggregate Improvement Score (GTI-AIS) over time

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 24 and 48.

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index - Aggregate Improvement Score (GTI-AIS) over time

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index - Aggregate Improvement Score (GTI-AIS) over time

For participants continuing/starting efgartigimod treatment at rollover or relapse: weeks 0, 8, every 16 weeks until and after efgartigimod treatment stop and at week 48.

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index Cumulative Worsening Score (GTI-CWS) over time

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index Cumulative Worsening Score (GTI-CWS) over time

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 24 and 48.

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index Cumulative Worsening Score (GTI-CWS) over time

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index Cumulative Worsening Score (GTI-CWS) over time

For participants continuing/starting efgartigimod treatment at rollover or relapse: weeks 0, 8, every 16 weeks until and after efgartigimod treatment stop and at week 48.

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index Specific List (GTI-SL) over time

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index Specific List (GTI-SL) over time

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index Specific List (GTI-SL) over time

Glucocorticoid Toxicity Index (GTI)-related scores, including the Glucocorticoid Toxicity Index Specific List (GTI-SL) over time

For participants continuing/starting efgartigimod treatment at rollover or relapse: weeks 0, 8, every 16 weeks until and after efgartigimod treatment stop and at week 48.

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 24 and 48.

For participants continuing/starting efgartigimod treatment at rollover or relapse: at weeks 0, 8, every 16 weeks until and after efgartigimod PH20 SC treatment stop and at week 48.

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 24 and 48.

For participants continuing/starting efgartigimod treatment at rollover or relapse: at weeks 0, 8, every 16 weeks until and after efgartigimod PH20 SC treatment stop and at week 48.

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 24 and 48.

For participants continuing/starting efgartigimod treatment at rollover or relapse: at weeks 0, 8, every 16 weeks until and after efgartigimod PH20 SC treatment stop and at week 48.

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 2, 4, 8, 16, 24, 32, 40, 48 and 56.

For participants continuing/starting efgartigimod PH20 SC treatment at rollover or relapse: at weeks 0, 2, 4 and 8 and then every 4 weeks to efgartigimod stop, every 8 weeks after efgartigimod stop and at weeks 48, 52 and 56.

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 4, 8, 16, 24, 32, 40, 48 and 56.

For participants continuing/starting efgartigimod treatment at rollover or relapse: at weeks 0, 2, 4 and 8 and then every 8 weeks until and after efgartigimod PH20 SC stop and at weeks 48, 52 and 56.

For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 4, 8, 16, 24, 32, 40, 48 and 56.

For participants continuing/starting efgartigimod treatment at rollover or relapse: at weeks 0, 2, 4 and 8 and then every 8 weeks until and after efgartigimod PH20 SC stop and at weeks 48, 52 and 56.

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 IMP and must use one of the contraception methods described in the protocol from signing the ICF until the last dose of IMP 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 IMP or 1 of its excipients Permanently discontinued IMP in ARGX-113-2009 due to an AE considered related to IMP and for whom the benefit/risk balance is not considered positive