A small-molecule pyridylsulfonamide inhibitor of phosphatidylinositol 3-kinase (PI3K) with potential antineoplastic activity. PI3K inhibitor GSK2126458 binds to and inhibits PI3K in the PI3K/mTOR signaling pathway, which may trigger the translocation of cytosolic Bax to the mitochondrial outer membrane, increasing mitochondrial membrane permeability and inducing apoptotic cell death. Bax is a member of the proapoptotic Bcl2 family of proteins. PI3K, often overexpressed in cancer cells, plays a crucial role in tumor cell regulation and survival.