Cenerimod 4 mg for Systemic Lupus Erythematosus (OPUS OLE Trial)

The goal of this clinical study is to learn about the long-term safety and tolerability of cenerimod in adult patients with moderate to severe symptoms of systemic lupus erythematosus. The main questions it aims to answer are: * Whether cenerimod causes any adverse effects ('side effects') when given on top of drugs already being given for systemic lupus erythematosus. * How well cenerimod works to reduce symptoms of systemic lupus erythematosus when taken for at least 1 year and up to 3 years. Participants taking part in this study will have already taken part in another study, where they received either cenerimod or placebo (look-alike substance containing no active drug) for 1 year. In this clinical study approximately 680 participants will receive cenerimod (on top of drugs already being given for systemic lupus erythematosus) for at least 1 year and up to 3 years.