Filgotinib is primarily used in the treatment of autoimmune and inflammatory conditions, most notably rheumatoid arthritis. It functions as a selective inhibitor of Janus kinase 1 (JAK1), which plays a key role in the signaling pathways of various pro-inflammatory cytokines. By targeting JAK1 with high specificity, filgotinib helps reduce inflammation and modulate the overactive immune response seen in autoimmune diseases. It has shown efficacy in reducing joint pain, swelling, and stiffness, and may help prevent long-term joint damage. Clinical studies support its use in patients who have not responded adequately to other disease-modifying antirheumatic drugs (DMARDs), including biologics. Additionally, filgotinib is being investigated for use in other inflammatory conditions such as Crohn’s disease, ulcerative colitis, and psoriatic arthritis, due to its targeted immunomodulatory effects. Its selectivity for JAK1 over other JAK family members may offer a more favorable safety profile, particularly in reducing off-target effects associated with broader JAK inhibition, making it a valuable option in chronic inflammatory disease management.