A Phase 3 Study to Evaluate the Efficacy and Safety of Efgartigimod IV in Patients With Acetylcholine Receptor Binding Antibody Seronegative Generalized Myasthenia Gravis (ADAPT SERON)

November 4, 2025 updated by: argenx

A Randomized, Double-Blinded, Placebo-Controlled, Phase 3, Parallel-Group Design Study Evaluating the Efficacy and Safety of Efgartigimod IV in Adult Participants With Acetylcholine Receptor Binding Antibody Seronegative Generalized Myasthenia Gravis

The primary purpose of this study is to measure the efficacy and safety of efgartigimod IV compared to placebo in participants with Acetylcholine Receptor Binding Antibody (AChR-Ab) seronegative Generalized Myasthenia Gravis (gMG). The study consists of a Part A where participants will be randomized to receive either efgartigimod IV or placebo IV and a Part B where participants completing part A will receive open-label efgartigimod IV. Participants will be in the study for up to (approximately) 2.5 years.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

119

Phase

  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Belgium
      • Anderlecht, Belgium, 1070
        • Hôpital Erasme
      • Brussels, Belgium, 1200
        • Cliniques universitaires Saint-Luc
      • Ghent, Belgium, 9000
        • AZ Sint-Lucas Gent
      • Leuven, Belgium, 3000
        • UZ Leuven
  • Canada
      • Calgary, Canada, T2N 4Z6
        • Heritage Medical Research Clinic
      • Montreal, Canada, H4A 3T2
        • Genge Partners Inc.
      • Ottawa, Canada, K1H 8L6
        • Ottawa Hospital - Civic Campus
  • China
      • Beijing, China, 100053
        • Xuanwu Hospital Capital Medical University
      • Changchun, China, 130021
        • The First Hospital of Jilin University
      • Chongqing, China, 400016
        • The First Affiliated Hospital of Chongqing Medical University
      • Chongqing, China, 400016
        • Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital
      • Fuzhou, China, 350001
        • Fujian Medical University Union Hospital
      • Guangxi, China, 530021
        • The First Affiliated Hospital of Guangxi Medical University
      • Guangzhou, China, 510405
        • The First Affiliated Hospital of Guangzhou University Chinese Medicine
      • Guangzhou, China, 518053
        • Guangdong Province Traditional Chinese Medical Hospital
      • Guiyang, China, 550004
        • The Affiliated Hospital of Guizhou Medical University
      • Ningbo, China, 315041
        • Ningbo Medical Center Lihuili Hospital
      • Qingdao, China, 266035
        • Qilu Hospital of Shandong University
      • Shanghai, China, 200040
        • Huashan Hospital Fudan University
      • Taiyuan, China, 030001
        • First Hospital of Shanxi Medical University
      • Wuhan, China, 430030
        • Tongji Hospital Tongji Medical College Huazhong University of Science and Technology
  • Cyprus
      • Égkomi, Cyprus, 2371
        • Cyprus Institute of Neurology and Genetics
  • Czechia
      • Brno, Czechia, 625 00
        • Fakultni Nemocnice Brno
      • Pardubice, Czechia, 530 03
        • Nemocnice Pardubickeho kraje, a.s., Pardubicka nemocnice
  • Denmark
      • Aarhus, Denmark, 8200
        • Aarhus Universitetshospital
      • Copenhagen, Denmark, 2100
        • Rigshospitalet
      • Odense C, Denmark, 5000
        • Odense Universitetshospital
  • Finland
      • Turku, Finland, 20540
        • Turun yliopistollinen keskussairaala
  • France
      • Marseille, France, 13386
        • AP-HM- Hôpital de La Timone
      • Nice, France, 06000
        • CHU de Nice-Hôpital Pasteur
      • Paris, France, 75013
        • AP-HP - Hôpital de la Pitié Salpétrière
  • Georgia
      • Kutaisi, Georgia, 4600
        • West Georgia Medical Center
      • Tbilisi, Georgia, 0114
        • New Hospitals
      • Tbilisi, Georgia, 0112
        • Petre Sarajishvili Institute of Neurology
      • Tbilisi, Georgia, 0112
        • Pineo Medical Ecosystem
      • Tbilisi, Georgia, 0186
        • LLC Caucasus Medical Centre
  • Germany
      • Berlin, Germany, 13353
        • Charite - Universitatsmedizin Berlin
      • Bochum, Germany, 44791
        • Katholisches Klinikum Bochum - St. Josef Hospital
      • Würzburg, Germany, 97080
        • Universitatsklinikum Wurzburg
  • Greece
      • Athens, Greece, 115 28
        • Eginitio Hospital
      • Chaïdári, Greece, 124 62
        • University General Hospital ''ATTIKON''
      • Pátrai, Greece, 265 04
        • University General Hospital of Patras
      • Thessaloniki, Greece, 546 36
        • AHEPA University General Hospital of Thessaloniki
  • Hungary
      • Budapest, Hungary, 1082
        • Semmelweis Egyetem Genomikai Medicina és Ritka Betegsegek Intezete
  • Netherlands
      • Leiden, Netherlands, 2333 ZA
        • Leiden University Medical Center
      • Utrecht, Netherlands, 3584 CX
        • Universitair Medisch Centrum Utrecht
  • Norway
      • Bergen, Norway, 5021
        • Haukeland Universitetssykehus
      • Oslo, Norway, 424
        • Oslo Universitetssykehus HF, Ulleval
  • Poland
      • Bydgoszcz, Poland, 85-065
        • MICS Centrum Medyczne Bydgoszcz
      • Katowice, Poland, 40-689
        • Centrum Medyczne Neurologia Slaska
      • Krakow, Poland, 31-503
        • Szpital Uniwersytecki w Krakowie
      • Krakow, Poland, 31-505
        • Krakowska Akademia Neurologii Sp. z o.o.
      • Lublin, Poland, 20-883
        • CLINIREM Sp z o.o.
      • Wroclaw, Poland, 50-556
        • Uniwersytecki Szpital Kliniczny im. Jana Mikulicza Radeckiego we Wroclawiu
  • Portugal
      • Lisbon, Portugal, 1150-199
        • ULS de Santa Maria, EPE - Hospital de Santa Maria
      • Lisbon, Portugal, 1349-019
        • ULS de Lisboa Ocidental, EPE - Hospital Egas Moniz
      • Porto, Portugal, 4050-011
        • Hospital de Santo António - Unidade Local de Saúde de Santo António
  • Romania
      • Cluj-Napoca, Romania, 400012
        • Cluj County Emergency Clinical Hospital
      • Sibiu, Romania, 550166
        • Sibiu Emergency County Clinical Hospital
  • Saudi Arabia
      • Riyadh, Saudi Arabia, 11211
        • King Faisal Specialist Hospital & Research Center
      • Riyadh, Saudi Arabia, 14611
        • National Guard Riyadh
  • Serbia
      • Belgrade, Serbia, 11000
        • Opsta bolnica MSB - Medicinski Sistemi Beograd
      • Kragujevac, Serbia, 34000
        • University Clinical Center Kragujevac
  • Spain
      • Alicante, Spain, 03010
        • Hospital General Universitario Dr. Balmis
      • Barcelona, Spain, 8035
        • Hospital Universitario Vall d'Hebron - PPDS
      • Barcelona, Spain, 8041
        • Hospital De La Santa Creu I Sant Pau
      • Lleida, Spain, 25198
        • Hospital Universitari Arnau de Vilanova
      • Madrid, Spain, 28304
        • Hospital Universitario Ramon y Cajal
      • Santiago de Compostela, Spain, 15706
        • Hospital Clínico Universitario de Santiago
      • Valencia, Spain, 46026
        • Hospital Universitari i Politecnic La Fe de Valencia
  • United Kingdom
      • Glasgow, United Kingdom, G51 4TY
        • Panthera Biopartners
      • Leeds, United Kingdom, LS1 3EX
        • Leeds General Infirmary
  • United States
    • Arizona
      • Scottsdale, Arizona, United States, 85251
        • HonorHealth Neurology - Bob Bove Neuroscience Institute
    • California
      • Fresno, California, United States, 93701-2234
        • Loma Linda University Health
    • Florida
      • Boca Raton, Florida, United States, 33428
        • First Choice Neurology Boca Raton
      • Boca Raton, Florida, United States, 33487
        • SFM Clinical Research LLC
      • Coral Springs, Florida, United States, 33067
        • The Neurology Institute / Healthcare Innovations Institute - Coral Springs
      • Maitland, Florida, United States, 32751
        • Neurology Associates PA
      • Miami, Florida, United States, 33136
        • Desai Sethi Medical Center
      • Port Charlotte, Florida, United States, 33952
        • Medsol Clinical Research Center Inc
      • St. Petersburg, Florida, United States, 33705-1410
        • BayCare - St. Anthony's Hospital
      • Tampa, Florida, United States, 33612
        • University of South Florida (USF) Health - Morsani Center for Advanced Healthcare
    • Georgia
      • Augusta, Georgia, United States, 30912
        • Wellstar - Augusta University Medical Center
    • Kansas
      • Fairway, Kansas, United States, 66205
        • Kansas University Medical Center - Kansas City
    • New Jersey
      • New Brunswick, New Jersey, United States, 08901-1962
        • Rutgers-Robert Wood Johnson Medical School
    • North Carolina
      • Chapel Hill, North Carolina, United States, 27599-7025
        • University of North Carolina - Chapel Hill
      • Durham, North Carolina, United States, 27710
        • Duke University School of Medicine - Duke Early Phase Clinical Research Unit
    • Ohio
      • Cleveland, Ohio, United States, 44195
        • Cleveland Clinic
    • Tennessee
      • Chattanooga, Tennessee, United States, 37403-2173
        • Erlanger Neuroscience Institute
    • Texas
      • Austin, Texas, United States, 78756
        • National Neuromuscular Research Institute
    • Washington
      • Seattle, Washington, United States, 98195
        • University of Washington Medical Center - Montlake

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • The participant is at least 18 years of age and the local legal age of consent for clinical studies when signing the ICF.
  • The participant is capable of providing signed informed consent and following with protocol requirements.
  • The participant agrees to use contraceptive measures consistent with local regulations and the women of child-bearing potential (WOCBP) must have a negative serum pregnancy test result at screening and a negative urine pregnancy test result at baseline before receiving the study drug.

  • The participant has no known weakness in infancy and later develop fatigable weakness after aged 16 years and diagnosed with acquired gMG of both of the following:

    1. History of abnormal neuromuscular transmission demonstrated by single fiber electromyography or repetitive nerve stimulation (RNS) or is anti-muscle-specific kinase antibodies (MuSK-Ab) seropositive
    2. Either a history of positive edrophonium chloride test OR a demonstrated improvement in MG signs with treatments such as oral acetylcholinesterase (AChE) inhibitors, plasma exchange (PLEX), immunoabsorption, or intravenous immunoglobulin (IVIg)/ subcutaneous immunoglobulin (SCIg) treatment
  • The participant is receiving a stable dose of MG therapy before screening that includes acetylcholinesterase (AChE) inhibitors, steroids, or nonsteroidal immunosuppressive therapies (NSISTs) in combination or alone.

Exclusion Criteria:

  • Known autoimmune disease or any medical condition that would interfere with an accurate assessment of clinical symptoms of gMG or puts the participant at undue risk
  • History of malignancy, cancer, unless considered cured by adequate treatment with no evidence of recurrence for ≥3 years. Adequately treated participants with the following cancers can be included at any time: Basal cell or squamous cell skin cancer, Carcinoma in situ of the cervix, Carcinoma in situ of the breast, Incidental histological findings of prostate cancer
  • Clinically significant active infection that is not sufficiently resolved in the investigator's opinion or positive serum test at screening for active infection with any of the following: Hepatitis B virus (HBV), Hepatitis C virus (HCV), HIV
  • History of or current alcohol, drug, or medication abuse as assessed by the investigator
  • Pregnant or lactating state or intention to become pregnant during the study
  • Live or live-attenuated vaccine received <4 weeks before screening
  • Worsening muscle weakness secondary to concurrent infections or medications
  • Received a thymectomy less than 3 months before screening or thymectomy is planned during the study

The complete list of exclusion criteria can be found in the protocol.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Efgartigimod IV
Patients receiving efgartigimod IV in both part A and part B
Biological: Efgartigimod IV
Intravenous infusion of efgartigimod
Placebo Comparator: Placebo
Patients receiving placebo during part A and receiving efgartigimod IV during part B
Biological: Efgartigimod IV
Intravenous infusion of efgartigimod
Other: Placebo IV
Intravenous infusion of placebo

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
MG-ADL total score change from baseline
Time Frame: Up to 29 days (part A)
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (normal symptoms) to 24 (most severe symptoms)
Up to 29 days (part A)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
QMG total score change from baseline
Time Frame: Up to 8 weeks (part A) + 2 years (part B)
The Quantitative myasthenia gravis (QMG) includes 13 items that measure endurance or fatigability and accounts for fluctuations in disease state. The total score ranges from 0 (no disease severity) to 39 (highest disease severity)
Up to 8 weeks (part A) + 2 years (part B)
Proportion of participants who are both MG-ADL and QMG responders in part A
Time Frame: Up to 8 weeks (part A)
Up to 8 weeks (part A)
Proportion of participants with MSE
Time Frame: Up to 8 weeks (part A) + 2 years (part B)
Minimal symptom expression (MSE) is defined as an MG-ADL total score of 0 or 1
Up to 8 weeks (part A) + 2 years (part B)
Proportion of participants who are MG-ADL responders in part A
Time Frame: Up to 8 weeks (part A)
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (normal symptoms) to 24 (most severe symptoms).
Up to 8 weeks (part A)
Proportion of participants who are QMG responders in part A
Time Frame: Up to 8 weeks (part A)
The Quantitative myasthenia gravis (QMG) includes 13 items that measure endurance or fatigability and accounts for fluctuations in disease state. The total score ranges from 0 (no disease severity) to 39 (highest disease severity)
Up to 8 weeks (part A)
Proportion of participants who are early MG-ADL responders in part A
Time Frame: Up to 8 weeks (part A)
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (normal symptoms) to 24 (most severe symptoms).
Up to 8 weeks (part A)
MG-ADL total score change from baseline over time in part A and part A+B
Time Frame: Up to 8 weeks (part A) + 2 years (part B)
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (normal symptoms) to 24 (most severe symptoms).
Up to 8 weeks (part A) + 2 years (part B)
MG-QoL15r change from baseline over time in part A and part A+B
Time Frame: Up to 8 weeks (part A) + 2 years (part B)
The Myasthenia Gravis Quality of Life-15 revised (MG-QoL15r) is a patient-reported instrument that measures the impact of MG symptoms on quality of life. The total scores range from 0 (best outcome) to 30 (worst outcome)
Up to 8 weeks (part A) + 2 years (part B)
EQ-5D-5L VAS change from baseline over time in part A and part A+B
Time Frame: Up to 8 weeks (part A) + 2 years (part B)
The EQ-5D-5L is a participant-reported measure of health status developed by the EuroQol Group. The questionnaire comprises 5 dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Current health status is rated on vertical visual analog score (VAS) from 0 to 100, with a score of 0 corresponding to "the worst health you can imagine" and 100 corresponding to "the best health you can imagine."
Up to 8 weeks (part A) + 2 years (part B)
Incidence of AEs and SAEs in part A and part A+B
Time Frame: Up to 8 weeks (part A) + 2 years (part B)
AE: adverse event; SAE: serious adverse event
Up to 8 weeks (part A) + 2 years (part B)
Total IgG concentrations percent changes from baseline over time in part A and part A+B
Time Frame: Up to 8 weeks (part A) + 2 years (part B)
Up to 8 weeks (part A) + 2 years (part B)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

argenx

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

April 16, 2024

Primary Completion (Actual)

June 30, 2025

Study Completion (Estimated)

June 1, 2027

Study Registration Dates

First Submitted

March 1, 2024

First Submitted That Met QC Criteria

March 1, 2024

First Posted (Actual)

March 7, 2024

Study Record Updates

Last Update Posted (Estimated)

November 5, 2025

Last Update Submitted That Met QC Criteria

November 4, 2025

Last Verified

November 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ARGX-113-2308
  • 2024-511796-15-00 (Other Identifier: CTIS number)

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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