JAK inhibitors are small-molecule drugs that block Janus kinases (JAKs), essential signaling mediators downstream of many pro-inflammatory cytokines. They have shown promise in treating immune and inflammatory diseases like rheumatoid arthritis (RA), psoriasis, and inflammatory bowel disease (IBD). First-generation JAK inhibitors, such as tofacitinib and baricitinib, have demonstrated efficacy in clinical trials, but second-generation compounds with greater selectivity are currently under development. Despite their potential, important questions remain about their safety, optimal dosing, and patient selection. Tofacitinib, a first-generation JAK inhibitor, has been approved for RA and has shown efficacy in psoriasis, psoriatic arthritis, ankylosing spondylitis, and IBD. Baricitinib, another first-generation JAK inhibitor, has also been approved for RA and has shown efficacy in psoriasis. Peficitinib, which blocks all four JAK isoforms, has shown similar efficacy to other JAK inhibitors in RA. JAK inhibitors have also been tested in other autoimmune and autoinflammatory diseases, including alopecia areata, atopic dermatitis, and systemic lupus erythematosus (SLE). However, they are associated with potential adverse effects, including increased infection risk, anemia, leukopenia, and malignancy. Additionally, JAK inhibitors may affect lipid metabolism and cardiovascular health. Next-generation JAK inhibitors, such as filgotinib and upadacitinib, are being developed to improve selectivity and reduce adverse effects. Filgotinib is a JAK1-selective inhibitor that has shown efficacy in Crohn's disease, while upadacitinib is a JAK1-selective inhibitor that has shown efficacy in RA and psoriasis. Decernotinib is a JAK3-selective inhibitor that has shown efficacy in RA but may cause neutropenia. TYK2-selective inhibitors are being developed to target specific cytokines involved in autoimmune diseases. Overall, JAK inhibitors have shown promise in treating a wide range of immune and inflammatory diseases, but their long-term safety and efficacy need to be further evaluated.JAK inhibitors are small-molecule drugs that block Janus kinases (JAKs), essential signaling mediators downstream of many pro-inflammatory cytokines. They have shown promise in treating immune and inflammatory diseases like rheumatoid arthritis (RA), psoriasis, and inflammatory bowel disease (IBD). First-generation JAK inhibitors, such as tofacitinib and baricitinib, have demonstrated efficacy in clinical trials, but second-generation compounds with greater selectivity are currently under development. Despite their potential, important questions remain about their safety, optimal dosing, and patient selection. Tofacitinib, a first-generation JAK inhibitor, has been approved for RA and has shown efficacy in psoriasis, psoriatic arthritis, ankylosing spondylitis, and IBD. Baricitinib, another first-generation JAK inhibitor, has also been approved for RA and has shown efficacy in psoriasis. Peficitinib, which blocks all four JAK isoforms, has shown similar efficacy to other JAK inhibitors in RA. JAK inhibitors have also been tested in other autoimmune and autoinflammatory diseases, including alopecia areata, atopic dermatitis, and systemic lupus erythematosus (SLE). However, they are associated with potential adverse effects, including increased infection risk, anemia, leukopenia, and malignancy. Additionally, JAK inhibitors may affect lipid metabolism and cardiovascular health. Next-generation JAK inhibitors, such as filgotinib and upadacitinib, are being developed to improve selectivity and reduce adverse effects. Filgotinib is a JAK1-selective inhibitor that has shown efficacy in Crohn's disease, while upadacitinib is a JAK1-selective inhibitor that has shown efficacy in RA and psoriasis. Decernotinib is a JAK3-selective inhibitor that has shown efficacy in RA but may cause neutropenia. TYK2-selective inhibitors are being developed to target specific cytokines involved in autoimmune diseases. Overall, JAK inhibitors have shown promise in treating a wide range of immune and inflammatory diseases, but their long-term safety and efficacy need to be further evaluated.