A Study to Evaluate the Safety,Tolerability,Pharmacokinetics and Pharmacodynamics of Cenerimod in Adult Chinese Participants With Moderate-to-severe Systemic Lupus Erythematosus (SLE)

The goal of this clinical trial is to learn about the safety, how the body processes the drug, and its effects of a drug called cenerimod in adult Chinese participants (aged 18-75) with moderate to severe Systemic Lupus Erythematosus (SLE) who are already receiving standard background therapy. The main questions it aims to answer are: * What is the safety and tolerability of a daily 4 mg dose of cenerimod in Chinese participants with SLE? * How is cenerimod processed by the body (pharmacokinetics) in this population? * What is the effect of cenerimod on the level of lymphocytes in the blood (pharmacodynamics)? This is a single-arm study without a comparison group. Participants will: * Take one 4 mg cenerimod tablet by mouth once daily for up to 12 months. * Continue their stable, pre-existing background SLE medications throughout the study. * Attend regular clinic visits over a period of up to 22 months for tests and check-ups, including blood draws, heart monitoring (12-lead electrocardiogram), vital signs(blood pressure),and physical examinations. * Undergo a final safety follow-up 6 months after their last dose of the study drug.