A Study to Assess the Long-term Safety and Efficacy of a Subcutaneous Formulation of Efgartigimod in Adults With Chronic Inflammatory Demyelinating Polyneuropathy (CIDP, an Autoimmune Disorder That Affects the Peripheral Nerves)

Study Overview
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Brief Summary
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This is the open-label extension study of phase II ARGX-113-1802 to evaluate the long-term safety and efficacy of the subcutaneous formulation of efgartigimod in adults with CIDP. Patients already stabilized on efgartigimod PH20 SC will also have the opportunity to participate in a sub study to explore less frequent dosing of efgartigimod PH20 SC.

Official Title
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Open-label Extension of the ARGX-113-1802 Trial to Investigate the Long-term Safety, Tolerability, and Efficacy of Efgartigimod PH20 SC in Patients With Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)

Conditions
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Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)

Intervention / Treatment
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* Biological: Efgartigimod PH20 SC


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Ability to understand the requirements of the trial, provide written informed consent (including consent for the use and disclosure of research-related health information), willingness and ability to comply with the trial protocol procedures (including required trial visits) of this trial. Male or female patient with one of the following options: Have completed the Week-48 visit of Stage B of the ARGX-113-1802 trial and are considered to be eligible for treatment with efgartigimod PH20 SC; or Have deteriorated during Stage B of the ARGX-113-1802 trial and are considered to be eligible for treatment with efgartigimod PH20 SC, or Have been offered the participation in the OLE trial due to early termination of the ARGX-113-1802 trial (because sufficient events for the primary endpoint analysis of the that trial have been reached and it is stopped) and are considered to be eligible for treatment with efgartigimod PH20 SC treatment; or Have completed the Week-48 visit of the previous cycle of the OLE trial and are considered to be eligible to continue with efgartigimod PH20 SC treatment. Women of childbearing potential who have a negative urine pregnancy test at baseline before IMP administration. Women of childbearing potential must use an acceptable method of contraception from signing the ICF until the date of the last administration of IMP. Exclusion Criteria: Week-48/ED visit in the ARGX-113-1802 trial or the Week-48 visit of the previous OLE participation occurred more than 14 days prior to SD1 of the OLE trial or the start of a new treatment cycle in the OLE trial and more than 21 days since the last dose of IMP. Pregnant and lactating women and those intending to become pregnant during the trial. Patients with clinical evidence of other significant serious disease or patients who underwent a recent or have a planned major surgery, or patients who (intend to) use prohibited medications (see protocol) and therapies during the trial, or any other reason which could confound the results of the trial or put the patient at undue risk.

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>Patients treated with efgartigimod PH20 SC | Biological: Efgartigimod PH20 SC<br>* Subcutaneous administration of efgartigimod<br>* Other names: ARGX-113;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of treatment-emergent adverse events and serious adverse events |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline over time of the adjusted INCAT score |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time of the MRC Sum score |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time of I-RODS disability scores |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time of mean grip strength |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time of TUG score |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Percentage of patients without clinical deterioration over time, defined by adjusted INCAT deterioration ≥1 point compared to baseline. |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Percentage of patients with titers of binding antibodies towards efgartigimod and the presence of neutralizing antibodies against efgartigimod. |  | Up to 51 weeks | 
| Efgartigimod serum concentrations |  | Up to 51 weeks | 
| Changes from baseline over time of serum IgG levels (total) |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time in EQ-5D-5L |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time in BPI SF |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time in TSQM-9 |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time in RT-FSS |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Change from baseline over time in HADS |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Percentage of patients performing self-administration over time |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study | 
| Percentage of patients with treatment administered by caregiver over time. |  | Up to 48 weeks per cycle (each cycle is 48 weeks) until the end of the study |