Filgotinib is primarily used in the treatment of autoimmune diseases, particularly rheumatoid arthritis. It works by selectively inhibiting the JAK1 enzyme, which plays a key role in the inflammatory process. This inhibition helps reduce inflammation and slow disease progression, providing relief from symptoms such as joint pain and swelling. It is often prescribed for patients who have not responded adequately to other treatments like methotrexate or biologic agents. Additionally, it is being investigated for its potential in treating other inflammatory conditions, such as Crohn's disease and ulcerative colitis, due to its targeted mechanism of action. Its oral administration offers a convenient alternative to injectable therapies.