A Phase 3 interventional study of Efgartigimod PH20 SC in Myositis, Active Idiopathic Inflammatory Myopathy and Dermatomyositis, sponsored by argenx. Enrolling by invitation at 92 sites in 29 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-21.
Sponsored by argenx · Phase 3, Interventional, and Treatment
The main purpose of this study is to measure the long-term safety and tolerability of efgartigimod PH20 SC in adult participants with Idiopathic Inflammatory Myopathy (IIM) who previously participated in ARGX-113-2007.
The study consists of a treatment period where participants will receive efgartigimod PH20 SC for up to 51 months. The treatment period will be followed by a treatment-free safety follow-up period of 56 days.
Exclusion Criteria:
Participants receiving efgartigimod PH20 subcutaneously
Biological: Efgartigimod PH20 SC
Subcutaneous injection of Efgartigimod PH20 given by vials or prefilled syringe (PFS)
Incidence of AEs, SAEs and AESIs over time
AE : adverse event ; SAE : serious adverse event ; AESI : adverse event of special interest.
Time frame: Up to 53 months
C-GTI comprising the AIS over time
The Composite Glucocorticoid Toxicity Index (C-GTI) serves as a primary instrument to capture toxicities likely caused by glucocorticoid exposure and enables monitoring of long-term tolerability of glucocorticoids during prolonged use. The Aggregate Improvement Score (AIS) is an analytical scores generated from the weighted C-GTI. The AIS can be used to assess whether a new therapy is effective in reducing glucocorticoid toxicity over time; higher AIS scores are associated with less toxicity.
Time frame: Up to 51 months
C-GTI comprising the CWS over time
The Composite Glucocorticoid Toxicity Index (C-GTI) serves as a primary instrument to capture toxicities likely caused by glucocorticoid exposure and enables monitoring of long-term tolerability of glucocorticoids during prolonged use. The Cumulative Worsening Score (CWS) is an analytical score generated from the weighted C-GTI. The CWS is designed to assess cumulative glucocorticoid toxicity; higher scores indicate increased steroid toxicity.
Time frame: Up to 51 months
C-GTI comprising the GTI-MD over time
The Composite Glucocorticoid Toxicity Index (C-GTI) serves as a primary instrument to capture toxicities likely caused by glucocorticoid exposure and enables monitoring of long-term tolerability of glucocorticoids during prolonged use. The Glucocorticoid Toxicity Index-Metabolic Domains (GTI-MD) is an abbreviated GTI version limited to the 4 metabolic domains. A GTI-MD score of 0 indicates a low likelihood of toxicity in the assessed metabolic domains.
Time frame: Up to 51 months
Prednisone dose reduction (average monthly dose) over time
Time frame: Up to 51 months
TIS over time
The total improvement score (TIS) assesses minimal, moderate, and major clinical response, and it is assessed using the ACR/EULAR criteria. The total score varies between 0 and 100, with higher scores indicating greater improvement.
Time frame: Up to 51 months
Proportion of TIS responders (minimal, moderate, major) over time
The total improvement score (TIS) assesses minimal, moderate, and major clinical response, and it is assessed using the ACR/EULAR criteria. The total score varies between 0 and 100, with higher scores indicating greater improvement
Time frame: Up to 51 months
Individual CSMs of the TIS over time
The total improvement score (TIS) assesses minimal, moderate, and major clinical response, and it is assessed using the ACR/EULAR criteria. The ACR/EULAR criteria calculate TIS using the 6 core set measure (CSMs): MDGA, PGA, MMT8, HAQ-DI, muscle enzymes, and extramuscular global assessment (assessed by the MDAAT).
Time frame: Up to 51 months
Percentage of participants with clinically inactive disease
Clinically inactive disease is defined as no evidence of disease activity, based on an Physician Global Assessment of Disease Activity (MDGA) and Extramuscular Global Assessment of the Myositis Disease Activity Assessment Tool (MDAAT) of 0 and normal creatine kinase (CK) values for at least 12 weeks (at week 28 and every 24 weeks thereafter).
Time frame: Up to 51 months
Percentage of participants with remission during the study
Remission is defined as a clinically inactive disease for at least 24 weeks
Time frame: Up to 51 months
PGI-S over time
The Patient Global Impression of Severity (PGI-S) asks participants to rate the severity of their disease symptoms over the past 7 days on a 4-point Likert scale, where scores range from "no symptoms" to "severe."
Time frame: Up to 51 months
CGI-S over time
The Clinical Global Impression of Severity (CGI-S) asks the physician to rate the severity of the participant's disease on a 4-point Likert scale, where scores range from "no activity" to "severe".
Time frame: Up to 51 months
Physical Functioning subscale and Physical Component Summary scores of the SF-36v2 over time
The 36-Item Short Form Survey version 2 (SF-36v2) is a 36-item scale constructed to survey health-related quality of life in 8 domains.
Time frame: Up to 51 months
EQ-5D-5L utilities over time
The EQ-5D-5L questionnaire is a standardized test recognized by many health authorities as a generic measure of health status for clinical and economic appraisal. The descriptive system comprises 5 dimensions, each having 5 levels ranging from "No problem" to "Extreme problem".
Time frame: Up to 51 months
EQ-5D-5L VAS over time
The EQ-5D-5L questionnaire is a standardized test recognized by many health authorities as a generic measure of health status for clinical and economic appraisal. A visual analog scale (VAS) is included in the EQ-5D-5L, where participants will mark their health status from 0 (the worst health you can imagine) to 100 (the best health you can imagine).
Time frame: Up to 51 months
Percent change from baseline in total IgG levels in serum over time
Time frame: Up to 53 months
Incidence of ADA against efgartigimod (serum levels) over time
ADA : anti-drug antibodies.
Time frame: Up to 53 months
Proportion of participants achieving sustained low disease activity while on IMP, over time
Sustained low disease activity is defined as a CGI-S score of "mild" or "no activity" and a PGI-S score of "mild" or "no symptoms" for at least 12 weeks.
Time frame: Up to 51 months
Proportion of participants with low disease activity over time, while on IMP
Low disease activity is defined as a CGI-S score of "mild" or "no activity" and a PGI-S score of "mild" or "no symptoms"
Time frame: Up to 51 months
Proportion of participants with low disease activity who continue dosing every 2 weeks at week 52 and every 24 weeks thereafter
Low disease activity is defined as a CGI-S score of "mild" or "no activity" and a PGI-S score of "mild" or "no symptoms"
Time frame: Up to 51 months
Proportion of participants who have marked worsening during the period of dosing every 2 weeks
Marked worsening is defined as a CGI-S score of "moderate" or "severe" and a PGI-S score of "moderate" or "severe"
Time frame: Up to 51 months
Duration of dosing every 2 weeks
Time frame: Up to 51 months
Plan to share: Undecided
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