This is a parallel group, Phase 2, 2-arm study to measure the treatment effect and safety of rilzabrutinib dose 1 or rilzabrutinib dose 2 in participants with Graves' disease, with and without Graves' orbitopathy, aged 18 years or older.

Study details include:

• Screening period (up to 4 weeks).
• Treatment period (up to 16 weeks).
• Follow-up period (4 weeks). The number of visits will be up to 13.

Inclusion Criteria:

• Participants who have a confirmed diagnosis of Graves' disease with active hyperthyroidism, with or without active Graves' orbitopathy at the time of screening.
• A subset of participants will have a diagnosis of active Graves' orbitopathy, as confirmed by ophthalmic exam at screening and a clinical activity score (CAS) ≥3 for the most severely affected eye, and associated with one or more of the following: lid retraction ≥2 mm, moderate or severe soft tissue involvement, proptosis ≥2 mm, and/or intermittent or constant diplopia.
• Contraceptive use by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

Exclusion Criteria:

• History of hyperthyroidism not caused by Graves' disease (eg, hyperthyroidism due to toxic multinodular goiter, autonomous thyroid nodule, acute inflammatory thyroiditis).
• History of thyroid storm or at high risk of developing thyroid storm as determined by evaluating clinician.
• Enlarged thyroid goiter causing upper airway obstruction and/or requiring surgical intervention during the study period.
• For participant with Graves' orbitopathy, requires immediate surgical ophthalmological intervention or is planning corrective surgery/irradiation during the course of the study.
• Sight threatening Graves' orbitopathy or decreased visual acuity due to optic neuropathy within the last 6 months.
• Corneal decompensation unresponsive to medical management.
• Onset of Graves' orbitopathy symptoms >9 months prior to baseline.

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org