Seletalisib (UCB-5857) is primarily investigated for its potential in treating autoimmune and inflammatory diseases. It functions as a selective inhibitor of phosphoinositide 3-kinase delta (PI3Kδ), a key enzyme involved in immune cell signaling, activation, and proliferation. By targeting this pathway, seletalisib modulates overactive immune responses without broadly suppressing the entire immune system. It has shown promise in clinical development for conditions such as lupus (systemic lupus erythematosus) and other B-cell-mediated autoimmune disorders. The compound may help reduce disease activity by limiting the survival and function of autoreactive B cells and plasma cells that contribute to tissue damage and autoantibody production. Additionally, due to its targeted mechanism, seletalisib offers a potentially favorable safety profile compared to broad immunosuppressants, making it a candidate for chronic treatment in autoimmune conditions where long-term immune modulation is required. Research is ongoing to fully define its therapeutic role and efficacy across different immune-mediated diseases.