JAK inhibitors are key drugs for treating inflammatory diseases and cancer, with billions in revenue. They target JAK enzymes, crucial for cytokine signaling, reducing inflammation and symptoms. Approved for atopic dermatitis, ulcerative colitis, rheumatoid arthritis, psoriasis, and alopecia areata, they offer significant benefits. For cancer, they treat myelofibrosis and are being explored in combinations with immune checkpoint inhibitors. Safety concerns led to FDA and EMA restrictions, but market growth is expected due to rising autoimmune disease prevalence.