A Study to Learn More About the Long-Term Safety of Litifilimab (BIIB059) Injections and it's Effects on Symptoms in Adults With Systemic Lupus Erythematosus (SLE)

In this study, researchers will learn more about a study drug called litifilimab (BIIB059) in participants with systemic lupus erythematosus (SLE). The study will focus on adults who have active disease and are already taking standard of care medications. These may include antimalarials, steroids, and immunosuppressants. This is an extension study of 230LE303 and 230LE304 (TOPAZ-1 and TOPAZ-2). It will include participants who completed the treatment periods of either one of those parent studies. The main goal of the study is to learn more about the long-term safety of litifilimab in adults. The main question researchers want to answer is: \- How many participants have adverse events and serious adverse events during the study? Adverse events are health problems that may or may not be caused by the study drug. Researchers will also learn about: * The effect of litifilimab on controlling symptoms of SLE and lowering its activity. * How participants' immune systems respond to litifilimab. * The effect of litifilimab on the quality of life of participants. The study will be done as follows: * This study begins when the participant has finished 1 of the parent studies (either 230LE303 or 230LE304). * Participants who were getting either a high or low dose of litifilimab in either parent study will continue getting the same doses. * Participants who were getting the placebo in the parent studies will be randomized to get either a high or low dose of litifilimab. * Neither the researchers nor the participants will know which doses of litifilimab the participants are getting. * All participants will get litifilimab as injections under the skin once every 4 weeks. The treatment period will last up to 260 weeks. Participants may continue to take their standard of care medications. * There will be a follow-up safety period that lasts up to 24 weeks. * In total, participants will have up to 73 study visits. At these visits, the study doctor will do tests to check the par