GSK-2126458 is primarily used in research and development within the field of oncology. It functions as a potent inhibitor of PI3K and mTOR pathways, which are critical in the regulation of cell growth, survival, and metabolism. By targeting these pathways, it helps in studying their role in cancer progression and identifying potential therapeutic strategies. Its application extends to preclinical studies where it is used to evaluate its efficacy in inhibiting tumor growth and its potential as a treatment for various cancers, including breast, lung, and prostate cancer. Additionally, it is utilized in biochemical assays to understand the molecular mechanisms underlying drug resistance in cancer cells.