A Phase 1 interventional study of ARGX-119 and Placebo in Congenital Myasthenic Syndrome and CMS, sponsored by argenx. Active, not recruiting at 9 sites in 6 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-07-24.
Sponsored by argenx · Phase 1, Interventional, and Treatment
The purpose of this study is to assess the safety and tolerability of ARGX-119 in adult participants with DOK7- Congenital Myasthenic Syndromes. The study will also assess how ARGX-119 is processed by the body (pharmacokinetics), how the immune system reacts to it (immunogenicity), and how it may improve the way patients feel and function.
After the screening period, eligible participants will be randomized in a 4:1 ratio to receive intravenous infusions of ARGX-119 or placebo during the double-blinded treatment period. Participants will then enter the follow-up period. After the follow-up period, participants may enrol in the active-treatment period, where they will receive open-label ARGX-119.
The full duration of the study is approximately 38 months.
argenx is the lead sponsor of 87 studies on the registry; 33 are open to participants now.
Of its 22 completed or terminated interventional studies of FDA-regulated products, 16 (73%) have results posted.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
Participants receive ARGX-119 during the double-blinded treatment period
Biological: ARGX-119
Participants receive placebo during the double-blinded treatment period
Other: Placebo
Participants receive ARGX-119 during the active-treatment period
Biological: ARGX-119
Intravenous infusion of ARGX-119
Intravenous infusion of placebo
Assessment of adverse events (AEs)
Time frame: Up to week 42
Change from active-treatment baseline over time for 6MWT distance
The 6-minute walk test (6MWT) measures the distance a participant walks in 6 minutes. Before and after the 6MWT assessment, the participant's blood pressure, heart rate, and SPO2 will be recorded, and the participant's perception of fatigue and dyspnea will be measured.
Time frame: Up to 72 weeks
Maximum observed serum concentration (Cmax) of ARGX-119
Time frame: Up to 42 weeks + 72 weeks
Incidence of ADA against ARGX-119
ADA : anti-drug antibodies
Time frame: Up to 42 weeks + 72 weeks
Change from baseline over time for key components of the QMG scale
The Quantitative Myasthenia Gravis (QMG) scale is a standardized quantitative scoring system that was developed to assess disease severity based on impairment of body function and structures in patients with MG. Minimum value: 0 (no disease severity); Maximum value: 39 (highest disease severity). The change from active-treatment baseline will be used for the 72 week timepoint.
Time frame: Up to 42 weeks + 72 weeks
Change from baseline over time for MG-ADL
The Myasthenia Gravis Activities of Daily Living (MG-ADL) is an 8-item scale that assesses MG symptoms and their effects on daily activities. Minimum value: 0 (normal symptoms); Maximum value: 24 (most severe symptoms). The change from active-treatment baseline will be used for the 72 week timepoint.
Time frame: Up to 42 weeks + 72 weeks
Change from baseline over time for PROMIS-GH scale
The Patient-Reported Outcomes Measurement Information System Global Health (PROMIS-GH) is a 10-item participant completed quality of life questionnaire that measures global physical health and mental health. The participant records their response to each question on a 5-point Likert scale, with lower scores indicating poorer health (Minimum value: 0, Maximum value: 20)
Time frame: Up to 42 weeks
Change from active-treatment baseline over time for 6MWT cadence
The 6-minute walk test (6MWT) measures the distance a participant walks in 6 minutes. Before and after the 6MWT assessment, the participant's blood pressure, heart rate, and SPO2 will be recorded, and the participant's perception of fatigue and dyspnea will be measured.
Time frame: Up to 72 weeks
Change from active-treatment baseline over time for PROMIS PF-WMA-SF
The PROMIS PF-WMA-SF is an 11-item, participant-completed questionnaire that assesses lower and upper extremity function and associated activities of daily living. The questionnaire asks the participant to rate the items on a 5-point scale of 5 (without any difficulty) to 0 (unable to do).
Time frame: Up to 72 weeks
Change from active-treatment baseline over time for Neuro-QoL fatigue
Time frame: Up to 72 weeks
Change from active-treatment baseline over time for FVC
Time frame: Up to 72 weeks
Change from active-treatment baseline over time for PGI-C
Time frame: Up to 72 weeks
Change from active-treatment baseline over time for PGI-S
Time frame: Up to 72 weeks
Change from active-treatment baseline over time for CGI-C
Time frame: Up to 72 weeks
Change from active-treatment baseline over time for CGI-S
Time frame: Up to 72 weeks
Change from active-treatment baseline over time for EQ-5D-5L
Time frame: Up to 72 weeks
Incidence of AEs and SAEs
AE : Adverse events ; SAE : Serious Adverse events
Time frame: Up to 72 weeks
Plan to share: No
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This study is active, not recruiting, as verified in Jul 2026. You cannot join it, but the record below documents what was studied.
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Myasthenic Syndromes, Congenital
argenx