Researchers are looking for new ways to treat rheumatoid arthritis (RA). Methotrexate (MTX) is a standard (usual) treatment for RA. However, MTX and other current treatments may not work well to treat RA symptoms for many people. This study will help find out if a study medicine called tulisokibart can treat symptoms of active RA in people who are taking MTX. In this study, researchers will look at different doses of tulisokibart. Researchers want to learn if at least one of the study doses of tulisokibart works better than a placebo to lessen RA symptoms. A placebo looks like the study medicine but has no study medicine in it. Using a placebo helps researchers better understand the effects of the study medicine.