A Study to Learn About The Effects of Felzartamab on Thyroid Function and Its Safety in Adults With Graves' Disease Ages 18 to 75 Years Old (GRAVITATE)

A Placebo-Controlled, Multicenter, Randomized Phase 2 Trial Evaluating the Efficacy and Safety of Felzartamab in Graves' Disease

In this study, researchers will learn more about the use of felzartamab in participants with Graves' Disease, also known as GD. GD is an autoimmune disease, which means the body's immune system attacks its own healthy cells. In people with GD, the immune system produces abnormal antibodies, called thyroid-stimulating hormone receptor antibodies (TRAb), that attack the thyroid gland. This causes the thyroid to become too active and produce too much hormone, a condition called hyperthyroidism.

Participants with GD are often treated with anti-thyroid drugs, or ATDs, which are medicines that help bring thyroid hormone levels back to normal. Felzartamab is designed to target certain immune cells that produce the abnormal TRAb antibodies.

The main goal of the study is to learn whether felzartamab can help bring thyroid hormone levels back to normal and allow participants to stop taking ATDs. Participants will receive either felzartamab or placebo during the study. A placebo looks like the study drug but contains no real medicine.

The main question that researchers want to answer is:

• How many participants have normal thyroid levels without receiving any ATD medicine at Week 24?

Researchers will also learn more about the safety of felzartamab and how the body processes the drug.

The study will be done as follows:

• Participants will be screened to check if they can join the study.
• This is a double-blind study, which means neither the participants, study doctor, or site staff will know if participants are receiving felzartamab or a placebo.
• Participants will be placed into 1 of 3 groups. Two groups will receive felzartamab while the other receives placebo.
• Participants will receive felzartamab or placebo as intravenous (IV) infusions, which are slow injections into a vein using a needle. The Treatment Period will last 20 weeks.
• During the Treatment Period, the study doctor may gradually lower the dose of the ATD if a participant's thyroid levels become normal.
• Afterwards, participants will enter a follow-up period which will last 12 weeks.
• In total, participants will have 22 study visits. Participants will stay in the study for about 9 months (up to 36 weeks).

Study Overview

• Status: Not yet recruiting
• Conditions: Graves' Disease
• Intervention / Treatment: Drug: Placebo; Drug: Felzartamab

Detailed Description

The primary objective of the study is to evaluate the efficacy of felzartamab compared to placebo in participants with Grave's disease (GD). The secondary objectives of the study are to evaluate the safety, efficacy and pharmacokinetics (PK) of felzartamab in participants with GD.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: US Biogen Clinical Trial Center; Phone Number: 866-633-4636; Email: clinicaltrials@biogen.com
• Study Contact Backup: Name: Global Biogen Clinical Trial Center; Email: clinicaltrials@biogen.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Key Inclusion Criteria:

• Have active disease and are thyroid-stimulating hormone receptor antibodies (TRAb) positive, defined as:

  • Free thyroxine (FT4) and free triiodothyronine (FT3), within the reference range,
  • suppressed thyroid-stimulating hormone (TSH)
  • TRAb levels > upper limit of normal (ULN)
• Participants must be receiving stable dose of anti-thyroid drugs (ATD) for at least 12 weeks prior to randomization.
• Must agree to refrain from blood product donation from Screening through end of study. If a participant terminates early from the study, they must refrain from blood product donation for 90 days following the last dose of study drug.

Key Exclusion Criteria:

• History of thyroidectomy or radioactive iodine therapy.
• ATD dose change within 12 weeks prior to Day1, or anticipated need for dose adjustment prior to randomization (except for protocol-defined safety management).
• Active, moderate-to-severe, or sight threatening thyroid eye disease (TED) (as assessed by the clinical activity score [CAS]), or requirement for imminent or ongoing TED-directed therapy (e.g., systemic glucocorticoids, biologic therapy, orbital radiation, surgery).
• Any history of malignancy within 5 years prior to Screening except for adequately treated in situ carcinoma of the cervix uteri, basal or squamous cell carcinoma or non-melanomatous skin cancer.
• History of hyperthyroidism not caused by GD (e.g. toxic multinodular goiter, autonomous thyroid nodule, acute inflammatory thyroiditis) and/or history or presence of thyroid storm.
• Type 1 diabetes and type 2 diabetes mellitus with hemoglobin A1c (HbA1c) > 8%.
• Known or suspected history of hypersensitivity to felzartamab or its excipients.
• Use of immunosuppressive therapy within 5 half-lives/12 weeks of Screening.
• Co-existing autoimmune diseases that require systemic immunosuppressants (e.g., cyclosporine, methotrexate, biologics, monoclonals).
• Prior use of an anti-Neonatal Fragment Crystallizable Receptor (FcRn) therapy or intravenous immunoglobulin (IVIg) within 6 months of the last dose prior to Screening.
• Any condition that requires chronic use of high-dose steroids.

NOTE: Other protocol-defined Inclusion/Exclusion criteria may apply.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Felzartamab; Participants will receive multiple IV doses of felzartamab.	Drug: Felzartamab; Administered IV; Other Names: MOR202; MOR03087; TJ202; BIIB148
Placebo Comparator: Placebo; Participants will receive multiple IV doses of placebo.	Drug: Placebo; Administered IV
Experimental: Felzartamab or Placebo; Participants will receive multiple IV doses of felzartamab or placebo.	Drug: Placebo; Administered IV; Drug: Felzartamab; Administered IV; Other Names: MOR202; MOR03087; TJ202; BIIB148

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Percentage of Participants who are Euthyroid and off Anti-Thyroid Drugs (ATD) at Week 24	At Week 24

Secondary Outcome Measures

Outcome Measure	Time Frame
Percentage of Participants who Have Down-Titrated to ≤ 50% of Their Baseline ATD and are Euthyroid at Week 12 and Week 24	At Weeks 12 and 24
Percentage of Participants who are Euthyroid at Week 12 and Week 24	At Weeks 12 and 24
Change From Baseline in Free Triiodothyronine (FT3)	Baseline up to Week 32
Change From Baseline in Free Thyroxine (FT4)	Baseline up to Week 32
Change From Baseline in Thyroid-Stimulating Hormone (TSH)	Baseline up to Week 32
Change From Baseline in ATD Levels	Up to Week 24
Number of Participants With Adverse Events (AEs), Serious Adverse Events (SAEs) and Adverse Events of Special Interest (AESI)	From first dose of study drug up to end of study follow-up (Up to Week 32)
Felzartamab Serum Concentrations Over Time	Predose and at multiple timepoints postdose up to Week 24
Number of Participants with Anti-drug Antibodies (ADAs) Against Felzartamab	Baseline up to Week 24

Collaborators and Investigators

• Sponsor: Biogen
• Investigators: Study Director: Medical Director, Biogen

Study record dates

Study Major Dates

• Study Start (Estimated): August 15, 2026
• Primary Completion (Estimated): January 31, 2028
• Study Completion (Estimated): March 31, 2028

Study Registration Dates

• First Submitted: July 20, 2026
• First Submitted That Met QC Criteria: July 20, 2026
• First Posted (Actual): July 23, 2026

Study Record Updates

• Last Update Posted (Actual): July 23, 2026
• Last Update Submitted That Met QC Criteria: July 20, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Hyperthyroidism
• Additional Relevant MeSH Terms: Endocrine System Diseases; Autoimmune Diseases; Immune System Diseases; Eye Diseases; Exophthalmos; Orbital Diseases; Goiter; Thyroid Diseases; Graves Disease; Hyperthyroidism; felzartamab
• Other Study ID Numbers: 299GD201; 2026-526482-19-00 (Ctis)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: In accordance with Biogen's Clinical Trial Transparency and Data Sharing Policy on https://www.biogentrialtransparency.com/

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