A Study to Assess Efficacy and Safety of Efgartigimod PH20 SC PFS in Adult Participants With Graves' Disease. (VitaliThy)

November 2, 2026 updated by: argenx

A Phase 3, Randomized, Double-Masked, Placebo-Controlled, Multicenter Study Evaluating the Efficacy and Safety of Efgartigimod PH20 SC PFS in Adult Participants With Graves' Disease Inadequately Controlled With Antithyroid Drugs

The main purpose of this study is to look at how efgartigimod affects thyroid function in adults with Graves' Disease (GD). The study will also check whether efgartigimod is safe and well tolerated. It will look at how efgartigimod is distributed and eliminated in the body, how it changes antibody levels, and how the immune system responds to it.

The study consists of a part A double-blinded treatment period, a part B treatment/observation period and a part C open-label treatment/observation period. During the part A and part B treatment periods, participants will receive efgartigimod PH20 SC via Prefilled Syringe (PFS) or placebo. During the part C open-label treatment period, participants will receive efgartigimod PH20 SC PFS. Participation in the different parts of the study will depend on the participant's response to treatment.

The total study duration for participants ranges from 63 to 135 weeks, depending on the response to treatment.

More information can be found here: https://clinicaltrials.argenx.com/vitalithy

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
230

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • 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 Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Belgium
      • Ghent, Belgium, 9000
        • Recruiting
        • Universitair Ziekenhuis Gent
        • Contact:
    • Oost-Vlass
      • Aalst, Oost-Vlass, Belgium, 9300
  • Bulgaria
      • Pazardzhik, Bulgaria, 4400
        • Recruiting
        • Medical Center Tonus - 2013 OOD
        • Contact:
      • Plovdiv, Bulgaria, 4002
      • Sliven, Bulgaria, 8800
        • Recruiting
        • Multiprofile Hospital for Active Treatment Hadzhi Dimitar OOD
        • Contact:
      • Sofia, Bulgaria, 1680
        • Recruiting
        • Medical Center Kalimat
        • Contact:
      • Varna, Bulgaria, 9000
        • Recruiting
        • Diagnostic Consultative Center Ekvita OOD
        • Contact:
      • Varna, Bulgaria, 9000
      • Veliko Tarnovo, Bulgaria, 5000
        • Recruiting
        • Multi-Profile District Hospital for Active Treatment Dr. Stefan Cherkezov
        • Contact:
  • Canada
      • Surrey, Canada, V3T 2V6
        • Recruiting
        • TLC Diabetes and Endocrinology Clinic
        • Contact:
    • Quebec
      • Montreal, Quebec, Canada, H4J1E3
  • Denmark
    • Capital Region
  • Georgia
      • Batumi, Georgia, 6000
        • Recruiting
        • High Technology Hospital Medcenter LLC
        • Contact:
      • Tbilisi, Georgia, 0160
        • Recruiting
        • LTD MediClub Georgia
        • Contact:
      • Tbilisi, Georgia, 0102
  • Germany
      • Magdeburg, Germany, 39110
        • Recruiting
        • Institut fuer Praeventive Medizin & Klinische Forschung
        • Contact:
  • Greece
      • Athens, Greece, 15125
        • Recruiting
        • Athens Medical Center
        • Contact:
      • Athens, Greece, 10676
        • Recruiting
        • Evangelismos Hospital
        • Contact:
  • Italy
  • Japan
      • Iizuka, Japan, 820-8505
        • Recruiting
        • Aso Iizuka Hospital
        • Contact:
      • Kawasaki, Japan, 211-8533
        • Recruiting
        • Nippon Medical School Musashikosugi Hospital
        • Contact:
      • Kitakyushu, Japan, 807-8556
        • Recruiting
        • Hospital of University of Occupational and Environmental Health
        • Contact:
      • Kyoto, Japan, 612-0861
        • Recruiting
        • National Hospital Organization Kyoto Medical Center
        • Contact:
      • Nagasaki, Japan, 852-8501
        • Recruiting
        • Nagasaki University Hospital
        • Contact:
      • Shibuya City, Japan, 150-8308
      • Yokohama, Japan, 224-8503
      • Yonago, Japan, 683-8504
    • Okayama-ken
      • Okayama, Okayama-ken, Japan, 700-8558
        • Recruiting
        • Okayama University Hospital
        • Contact:
    • Tokyo
      • Bunkyō-Ku, Tokyo, Japan, 113-8431
        • Recruiting
        • Juntendo University Hospital
        • Contact:
      • Ōta-ku, Tokyo, Japan, 143-8541
        • Recruiting
        • Toho University Omori Medical Center
        • Contact:
  • Latvia
      • Adazi, Latvia, LV2164
        • Recruiting
        • LTD M & M Centers
        • Contact:
      • Riga, Latvia, 1012
        • Recruiting
        • Veselibas centrs 4
        • Contact:
  • Lithuania
      • Klaipėda, Lithuania, LT-92288
        • Recruiting
        • Klaipeda's University Hospital
        • Contact:
    • Kauno
      • Kaunas, Kauno, Lithuania, 50161
        • Recruiting
        • Hospital of Lithuanian University of Health Sciences Kaunas
        • Contact:
  • Poland
      • Bydgoszcz, Poland, 85-605
        • Recruiting
        • Centrum Medyczne INTERCOR Sp. z o.o.
        • Contact:
      • Chrzanów, Poland, 32-500
      • Lublin, Poland, 20-412
      • Lublin, Poland, 20607
        • Recruiting
        • Reumed Sp Z O.O.
        • Contact:
      • Warsaw, Poland, 01-691
      • Warsaw, Poland, 00-124
      • Warsaw, Poland, 02-677
        • Recruiting
        • Etg Warszawa Sp. z o.o.
        • Contact:
      • Zamość, Poland, 22400
    • Lesser Poland Voivodeship
      • Krakow, Lesser Poland Voivodeship, Poland, 30-074
    • Silesian Voivodeship
      • Katowice, Silesian Voivodeship, Poland, 40-600
  • Romania
      • Cluj-Napoca, Romania, 400396
        • Recruiting
        • Cluj County Clinical Emergency Hospital
        • Contact:
    • Sibiu County
      • Sibiu, Sibiu County, Romania, 550245
        • Recruiting
        • Clinical Hospital of Emergency Sibiu Ambulatory if Endocrinology
        • Contact:
  • Spain
      • Alzira, Spain, 46600
        • Recruiting
        • Hospital Universitario De La Ribera
        • Contact:
      • Barcelona, Spain, 08041
        • Recruiting
        • Hospital de la Santa Creu i Sant Pau
        • Contact:
      • Móstoles, Spain, 28935
        • Recruiting
        • Hospital Universitario de Móstoles
        • Contact:
      • Santander, Spain, 39011
        • Recruiting
        • Instituto De Investigacion Marques De Valdecilla (IDIVAL
        • Contact:
      • Seville, Spain, 41009

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Is at least 18 years of age and the local legal age of consent for clinical studies when signing the ICF.
  • Has a documented diagnosis of GD with TRAb (anti-thyrotropin receptor antibody) levels >=ULN (upper limit of normal) at screening
  • Has active hyperthyroidism due to GD with TSH (thyroid-stimulating hormone) <0.1 mIU/L at screening
  • Has been treated with MMI (methimazole) or CBZ (carbimazole) for at least 3 months before screening

Exclusion Criteria:

  • History of hyperthyroidism not caused by GD (eg, toxic adenoma or toxic multinodular goiter)
  • History of RAI (radioactive iodine) therapy or received a total thyroidectomy
  • T3- or T4-containing medication or supplement (eg, levothyroxine, liothyronine, desiccated thyroid preparations, or thyroid-support supplements) received <6 weeks before screening
  • Any complication of hyperthyroidism or underlying medical condition that would put the participant at undue risk. This includes arrhythmia or tachyarrhythmia related to GD, such as atrial fibrillation or atrial flutter not sufficiently controlled with medications.
  • Graves' orbitopathy/Thyroid Eye Disease (GO/TED) requiring systemic therapy (eg, corticosteroids), orbital injections, orbital surgery, or orbital radiation, or expected immediate surgical intervention and/or planned corrective surgery/irradiation or medical therapy during the study

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: Quadruple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Part A - efgartigimod PH20 SC PFS

Participants will receive efgartigimod PH20 SC Via Prefilled Syringe (PFS) during the part A double-blinded treatment period.
Biological: efgartigimod PH20 SC

Subcutaneous injection of Efgartigimod PH20 Via Prefilled Syringe (PFS)
Placebo Comparator: Part A - placebo PH20 SC PFS

Participants will receive placebo PH20 SC Via Prefilled Syringe (PFS) during the part A double-blinded treatment period.
Other: Placebo PH20 SC

Subcutaneous injection of placebo PH20 via Prefilled Syringe (PFS)
Experimental: Part B - efgartigimod PH20 SC PFS

Participants will receive efgartigimod PH20 SC Via Prefilled Syringe (PFS) during the part B treatment period.
Biological: efgartigimod PH20 SC

Subcutaneous injection of Efgartigimod PH20 Via Prefilled Syringe (PFS)
Experimental: Part B - placebo PH20 SC PFS

Participants will receive placebo PH20 SC Via Prefilled Syringe (PFS) during the part B treatment period.
Other: Placebo PH20 SC

Subcutaneous injection of placebo PH20 via Prefilled Syringe (PFS)
Experimental: Part C - efgartigimod PH20 SC PFS

Participants, will receive efgartigimod PH20 SC PFS in the part C open-label treatment period
Biological: efgartigimod PH20 SC

Subcutaneous injection of Efgartigimod PH20 Via Prefilled Syringe (PFS)

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Percentage of participants who are euthyroid (fT3, fT4, and TSH within normal ranges) off ATDs at week 24 in part A
Time Frame: up to 24 weeks (part A)

free triiodothyronine: [fT3]; free thyroxine: [fT4]; ATDs: antithyroid drugs
up to 24 weeks (part A)

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Time to becoming euthyroid
Time Frame: up to 24 weeks (part A) + up to 135 weeks
up to 24 weeks (part A) + up to 135 weeks
Efgartigimod serum concentrations over time
Time Frame: up to 24 weeks (part A) + 72 weeks (part C)
up to 24 weeks (part A) + 72 weeks (part C)
Time to becoming euthyroid off ATDs in part A
Time Frame: Up to 24 weeks (part A)

ATDs: antithyroid drugs
Up to 24 weeks (part A)
Percentage of participants who are euthyroid and receiving MMI ≤5 mg/day or CBZ ≤7.5 mg/day at week 24 in part A
Time Frame: up to 24 weeks (part A)

MMI: methimazole (also known as thiamazole); CBZ carbimazole
up to 24 weeks (part A)
Percentage of participants with fT3 and fT4 levels below the ULN off ATDs at week 24 in part A
Time Frame: Up to 24 weeks (part A)

ULN : upper limit of normal; ATDs: antithyroid drugs
Up to 24 weeks (part A)
Percentage of participants who are euthyroid off ATDs and TRAb seronegative at week 24 in part A
Time Frame: up to 24 weeks (part A)

TRAb: anti-TSHR autoantibodies; ATDs: antithyroid drugs
up to 24 weeks (part A)
Time to becoming euthyroid off ATDs and TRAb seronegative
Time Frame: up to 24 weeks (part A) + up to 135 weeks

ATDs: antithyroid drugs; TRAb: anti-TSHR autoantibodies
up to 24 weeks (part A) + up to 135 weeks
Time to becoming euthyroid and receiving an ATD dose of MMI ≤5 mg/day or CBZ ≤7.5 mg/day (part A)
Time Frame: up to 24 weeks

ATDs: antithyroid drugs; MMI: methimazole (also known as thiamazole); CBZ carbimazole
up to 24 weeks
Time to having fT3 and fT4 levels within normal ranges among participants who had fT3 and/or fT4 more than the ULN at baseline (part A)
Time Frame: up to 24 weeks (part A)

ULN : upper limit of normal
up to 24 weeks (part A)
Time to having TSH within normal ranges among participants who have TSH lower than the LLN at baseline (part A)
Time Frame: up to 24 weeks (part A)

TSH: thyroid-stimulating hormone; LLN: lower limit of normal
up to 24 weeks (part A)
Percentage of participants who remain euthyroid off ATDs
Time Frame: Up to 50 weeks (part B)

ATDs: antithyroid drug
Up to 50 weeks (part B)
Percentage of participants who are euthyroid and receiving MMI ≤5 mg/day or CBZ ≤7.5 mg/day
Time Frame: Up to 50 weeks (part B)

ATDs: antithyroid drug
Up to 50 weeks (part B)
Percentage of participants who remain euthyroid without ATDs
Time Frame: up to 98 weeks (part B)

ATDs: antithyroid drug
up to 98 weeks (part B)
Percentage of participants who remain euthyroid without ATDs and without efgartigimod PH20 SC PFS for 6, 12, and 18 months
Time Frame: up to 74 weeks (part B) + up to 135 weeks

ATDs: antithyroid drug
up to 74 weeks (part B) + up to 135 weeks
Percentage of participants who remain euthyroid without ATDs and without efgartigimod PH20 SC PFS
Time Frame: up to 72 weeks (part C)

ATDs: antithyroid drug
up to 72 weeks (part C)
Incidence of AEs and SAEs
Time Frame: up to 135 weeks

AEs: adverse events ; SAEs: serious adverse events
up to 135 weeks
Change in ThyPRO-39 over time
Time Frame: Up to 135 weeks

The Thyroid-Specific Patient-Reported Outcome Short Form (ThyPRO-39) 39 item version of the ThyPRO. Each item is related to a specific aspect of the participant's experience with their thyroid condition. Each item is scored on a 5-point Likert scale, and the scores are then transformed to a 0-to-100 scale. Higher scores indicate worse health status
Up to 135 weeks
Change in PROMIS-PF10a over time
Time Frame: up to 135 weeks

The Patient-Reported Outcomes Measurement Information System Physical Function-10 item (PROMIS-PF10a) is a self- administered physical functioning assessment comprising 10 items that measure respondents' ability to perform common physical tasks. Scoring involves summing the numerical responses to each item; higher scores indicate better physical function.
up to 135 weeks
Percentage change from baseline in total IgG levels in serum over time
Time Frame: up to 98 weeks

IgG: immunoglobulin G
up to 98 weeks
Percentage change from baseline in TRAb serum levels over time
Time Frame: up to 135 weeks

TRAb: anti-TSHR autoantibodies
up to 135 weeks
Incidence of ADA against efgartigimod in serum
Time Frame: up to 24 weeks (part A) + up to 135 weeks

ADA: antidrug antibody(ies)
up to 24 weeks (part A) + up to 135 weeks
Incidence of antibodies against rHuPH20 in plasma
Time Frame: up to 24 weeks (part A) + Up to 135 weeks

rHuPH20: recombinant human hyaluronidase PH20
up to 24 weeks (part A) + Up to 135 weeks
Incidence of NAb against efgartigimod in serum and rHuPH20 in plasma
Time Frame: up to 24 weeks (part A) + up to 135 weeks

NAb: neutralizing antibody(ies); rHuPH20: recombinant human hyaluronidase PH20
up to 24 weeks (part A) + up to 135 weeks

Collaborators and Investigators

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

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
June 10, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
June 1, 2028

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
May 1, 2030

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
May 13, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 13, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
May 19, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 3, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 2, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
September 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • ARGX-113-25-GRD-3001
  • 2025-523333-26-00 (Ctis)
  • 2025 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

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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