A Phase 2a/b Study to Assess the Efficacy, Safety and Tolerability of DDY391 in Participants With Sjögren's Disease

To evaluate efficacy, safety, and tolerability of DDY391 up to 52 weeks in participants with Sjögren's disease (SjD) and to determine the dose response relationship of DDY391 in participants with SjD, to support dose selection for Phase 3.

Key Inclusion Criteria: • Participants must have a diagnosis of SjD according to the ACR/EULAR 2016 classification criteria at screening: \- Positive anti-Ro (SSA) antibodies at screening. Participants negative for anti-Ro/SSA antibodies are eligible if they have documented previous biopsy showing evidence of salivary gland inflammation consistent with SjD. Key Exclusion Criteria: * Presence of another autoimmune rheumatic disease that is active at screening and constitutes the principal illness. * Exclusion based on medications being used for SjD: * Participants taking \> 400 mg/day hydroxychloroquine are excluded. Participants taking ≤400 mg/day hydroxychloroquine should be on a stable dose for at least 4 weeks prior to randomization. * Participants taking \> 400 mg/day hydroxychloroquine are excluded. Participants on ≤ 400 mg/day of hydroxychloroquine should be on a stable dose for at least 4 weeks prior to randomization. * Prior treatment with any of the following within 3 months prior to randomization: belimumab, abatacept, anti-tumor necrosis factor alpha biologic agents, immunoglobulins, plasmapheresis, intravenous (i.v.) or oral cyclophosphamide, mycophenolate mofetil, i.v. or oral cyclosporine A, or any other immunosuppressants (e.g., JAK inhibitors or other kinase inhibitors, IL-2, anti-IL-6, anti-IL-17). * Previous treatment with any cell-depleting therapies, including but not limited to anti-CD20, unless ≥ 12 months prior to screening. * Any viral, bacterial or other infections at the time of screening or randomization, or history of recurrent clinically significant infection or of recurrent bacterial infection. * History of malignancy of any organ system (other than localized non melanoma carcinoma of the skin or in situ cervical cancer) within the last five years of randomization or any malignancy not in remission. Other protocol-defined inclusion/exclusion criteria may apply.