Phase 3 Study of Telitacicept in Active Primary Sjögren's Disease (UPSTREAM SjD)

Telitacicept (RC18) is a recombinant fusion protein designed to target B-cell-mediated immune pathways. It consists of the extracellular domain of transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) linked to the Fc portion of human immunoglobulin G1 (IgG1).

Telitacicept binds with high affinity to the cytokines B-lymphocyte stimulator (BLyS, also known as BAFF) and A Proliferation-Inducing Ligand (APRIL). By binding these soluble factors, telitacicept prevents their interaction with cell-surface receptors on B cells, including TACI, B-cell maturation antigen (BCMA), and BAFF receptor (BAFF-R).

This inhibition reduces BLyS/APRIL signaling, leading to decreased B-cell survival, reduced differentiation of B cells into immunoglobulin-producing plasma cells, and lowering of autoantibody production, increased BLyS and APRIL levels, B-cell hyperactivity, and autoantibody production are associated with multiple autoimmune diseases.

Modulation of the BLyS/APRIL pathway is intended to reduce pathogenic B-cell activity and downstream immune effects that contribute to disease manifestations in Sjogren's disease and other B-cell-mediated autoimmune conditions.

Inclusion Criteria:

1. Male or female aged 18 to 75 years of age (both inclusive) at screening
2. Participants must meet the 2016 American College of Rheumatology (ACR)/EULAR classification criteria for primary Sjogren's Syndrome at the time of screening.
3. ESSDAI ≥5 at screening (score calculated excluding renal, pulmonary and neurological domains)
4. Participants are seropositive for antibodies to Sjogren's Syndrome A (SSA)/Anti-Sjogren's Syndrome A (Ro) at the Screening Visit.

Additional inclusion criteria are defined in the protocol

Exclusion Criteria:

1. Participants who have a systemic autoimmune disease other than Primary Sjogren's Disease, such as rheumatoid arthritis, systemic lupus erythematosus, or systemic sclerosis, that can better explain the majority of the symptoms (i.e., secondary Sjogren's Disease)
2. Participants who have another autoimmune disease or inflammatory condition that could interfere with assessment of response of Primary Sjogren's Disease to therapy (e.g., systemic sclerosis, inflammatory bowel disease, gout).
3. Participants with severe fibromyalgia that could interfere with the assessment of response of Primary Sjogren's Disease to therapy
4. Active life-threatening or organ-threatening complications of Primary Sjogren's Disease at the time of screening based on investigator evaluation
5. Significant, uncontrolled medical disease in any organ system not related to Primary Sjogren's Disease (e.g., poorly controlled asthma, cardiovascular disease, accelerated hypertension, major depression, etc.) that in the opinion of the investigator would preclude participant participation.

Additional exclusion criteria are defined in the protocol