This study is testing a new medicine called Afimetoran for people with a disease called Systemic Lupus Erythematosus (SLE). SLE is a condition where the immune system, which usually fights infections, attacks the body by mistake. The study will check if Afimetoran works well and is safe. People in the study will first get Afimetoran or a placebo, which is a pill that doesn't have any medicine in it. Later, everyone can try Afimetoran.

Eligibility: Participants must have been diagnosed with SLE for at least 12 weeks. They need to test positive for specific lupus antibodies and have a certain score on a disease activity test. People with serious kidney or brain problems related to lupus cannot join.

• The study includes a long-term extension period for safety data.
• Participants initially on placebo will later receive Afimetoran.
• Participants need to have specific lupus antibodies and disease scores.