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

Study Overview
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Brief Summary
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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.

Official Title
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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

Conditions
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Bullous Pemphigoid

Intervention / Treatment
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* Biological: efgartigimod PH20 SC
* Drug: Prednisone


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: efgartigimod PH20 SC<br>participants receiving efgartigimod PH20 SC on top of Prednisone | Biological: efgartigimod PH20 SC<br>* Subcutaneous injection of efgartigimod coformulated with rHuPH20, a permeation enhancer<br>Drug: Prednisone<br>* Oral Prednisone<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of treatment-emergent adverse events | Incidence of treatment-emergent adverse events | Up to 56 weeks | 
| Severity of treatment-emergent adverse events | 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) | Up to 56 weeks | 
| Incidence of serious adverse events | Incidence of serious adverse events | Up to 56 weeks | 
| Severity of serious adverse events | Severity of serious adverse events | Up to 56 weeks | 
| Incidence of adverse events of special interest | Incidence of adverse events of special interest | Up to 56 weeks | 
| Severity of adverse events of special interest | 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) | Up to 56 weeks | 
| Rate of treatment discontinuation because of safety concerns | Rate of treatment discontinuation because of safety concerns | Up to 56 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Proportion of participants achieving complete remission while off oral corticosteroids for ≥ 8 weeks | Proportion of participants achieving complete remission while off oral corticosteroids for ≥ 8 weeks | Up to 56 weeks | 
| 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 | Up to 56 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) | Up to 56 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 while off both oral corticosteroids and efgartigimod PH20 SC for ≥ 8 weeks | Up to 56 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 | Up to 56 weeks | 
| Duration of sustained remission | Duration of sustained remission | Up to 56 weeks | 
| Proportion of participants who relapse | Proportion of participants who relapse | Up to 56 weeks | 
| Time to relapse | Time to relapse | Up to 56 weeks | 
| Incidence of relapse | Incidence of relapse | Up to 56 weeks | 
| Severity of relapse | Severity of relapse will be assessed based on the Bullous Pemphigoid Disease Area Index (BPDAI) | Up to 56 weeks | 
| Bullous Pemphigoid Disease Area Index (BPDAI) activity scores over time | Bullous Pemphigoid Disease Area Index (BPDAI) activity scores over time | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 2, 4, 8, 16, 24, 32, 40, 48 and 56. | 
| Bullous Pemphigoid Disease Area Index (BPDAI) activity scores over time | Bullous Pemphigoid Disease Area Index (BPDAI) activity scores over time | 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. | 
| Investigator Global Assessment of Bullous Pemphigoid (IGA-BP) scores over time | Investigator Global Assessment of Bullous Pemphigoid (IGA-BP) scores over time | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 2, 4, 8, 16, 24, 32, 40, 48 and 56. | 
| Investigator Global Assessment of Bullous Pemphigoid (IGA-BP) scores over time | Investigator Global Assessment of Bullous Pemphigoid (IGA-BP) scores over time | 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. | 
| Itch Numerical Rating Scale (NRS) over time | Itch Numerical Rating Scale (NRS) over time | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 2, 4, 8, 16, 24, 32, 40, 48 and 56. | 
| Itch Numerical Rating Scale (NRS) over time | Itch Numerical Rating Scale (NRS) over time | 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. | 
| Rate of treatment failure | Rate of treatment failure | Up to 56 weeks | 
| 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 | For participants not requiring treatment with efgartigimod at rollover: at weeks 0, 24 and 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 | 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. | 
| EQ-5D-5L scores over time | EQ-5D-5L scores over time | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 24 and 48. | 
| EQ-5D-5L scores over time | EQ-5D-5L scores over time | 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. | 
| Autoimmune Bullous Disease Quality of Life (ABQoL) scores over time | Autoimmune Bullous Disease Quality of Life (ABQoL) scores over time | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 24 and 48. | 
| Autoimmune Bullous Disease Quality of Life (ABQoL) scores over time | Autoimmune Bullous Disease Quality of Life (ABQoL) scores over time | 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. | 
| Dermatology Life Quality Index (DLQI) scores over time | Dermatology Life Quality Index (DLQI) scores over time | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 24 and 48. | 
| Dermatology Life Quality Index (DLQI) scores over time | Dermatology Life Quality Index (DLQI) scores over time | 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. | 
| Percent changes from baseline over time for anti-BP180 and anti-BP-230 antibody levels | Percent changes from baseline over time for anti-BP180 and anti-BP-230 antibody levels | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 2, 4, 8, 16, 24, 32, 40, 48 and 56. | 
| Percent changes from baseline over time for anti-BP180 and anti-BP-230 antibody levels | Percent changes from baseline over time for anti-BP180 and anti-BP-230 antibody levels | 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. | 
| Incidence of antidrug antibody(ies) (ADA) against efgartigimod (serum levels) | Incidence of antidrug antibody(ies) (ADA) against efgartigimod (serum levels) | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 4, 8, 16, 24, 32, 40, 48 and 56. | 
| Incidence of antidrug antibody(ies) (ADA) against efgartigimod (serum levels) | Incidence of antidrug antibody(ies) (ADA) against efgartigimod (serum levels) | 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. | 
| Prevalence of antidrug antibody(ies) (ADA) against efgartigimod (serum levels) | Prevalence of antidrug antibody(ies) (ADA) against efgartigimod (serum levels) | For participants not requiring treatment with efgartigimod PH20 SC at rollover: at weeks 0, 4, 8, 16, 24, 32, 40, 48 and 56. | 
| Prevalence of antidrug antibody(ies) (ADA) against efgartigimod (serum levels) | Prevalence of antidrug antibody(ies) (ADA) against efgartigimod (serum levels) | 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. |