Iguratimod (IGU) is a synthetic, small-molecule drug used to treat rheumatoid arthritis (RA). It's a disease-modifying antirheumatic drug (DMARD) that helps reduce inflammation, relieve symptoms, and potentially slow the progression of RA. IGU works by suppressing the production of pro-inflammatory cytokines, like IL-1, IL-6, and TNF-α, which contribute to inflammation and autoimmune responses. It also regulates the balance of immune cells and cytokines.