A Study to Evaluate the Efficacy and Safety of Abiprubart in Participants With Sjögren's Disease

Inclusion Criteria:

• Has a diagnosis of Sjögren's Disease according to 2016 American College orRheumatology (ACR)-EULAR Classification Criteria.

• Has ESSDAI value ≥ 5, counting only the biological, hematological, articular,cutaneous, glandular, lymphadenopathy, and constitutional organ domains atScreening.

• Is seropositive at Screening for anti-Sjögren's-syndrome-related antigen Aautoantibodies (SSA) antibodies tested at a central laboratory.

• Has stimulated whole salivary flow rate at Screening of ≥ 0.05 mL/min

• Weighs at least 40 kg and no more than 150 kg and has a body mass index (BMI) withinthe range of 18-40 kg/m2.

Exclusion Criteria:

• Prior exposure to any other anti-CD40/CD154 agent.

• Diagnosis of Sjögren's Disease overlap syndromes where another autoimmune rheumaticdisease constitutes the principal illness, including fibromyalgia with currentlyactive, inadequately controlled symptoms.

• Has received cataract surgery, Lasik, or other ophthalmologic surgery procedure (e.g., lachrymal plug) in the 6 months prior to Screening.

• Injectable corticosteroids (including intra-articular) within 8 weeks prior torandomization.

• Has started, stopped or adjusted dose/regimen of medications for treatment of, orknown to cause dry mouth/eyes within the 30 days prior to screening or isanticipating change to these treatment regimens during the study.

• Has history of immunodeficiency (e.g., immune disorders or disorders that result indecreased immunity), including human immunodeficiency virus (HIV).

• History of thromboembolic event or a significant risk of future thromboembolicevents.

• Has a known high risk of infection; Has a history of chronic or recurrent infectiousdisease; Has any known or suspected active infection, or has had a serious infectionrequiring hospitalization, or has been treated with IV/IM antibiotics for aninfection within 8 weeks prior to first dose of study drug or treatment with oralantibiotics for an infection within 2 weeks prior to first dose of study drug.