PP121 is a potent dual inhibitor targeting both PI3K and mTOR signaling pathways, making it valuable in cancer research. It is primarily used in preclinical studies to investigate tumor growth suppression, especially in cancers with hyperactivated PI3K/mTOR pathways such as breast, lung, and prostate cancers. Its ability to cross the blood-brain barrier enhances its utility in studying brain tumors and central nervous system malignancies. PP121 induces apoptosis and inhibits proliferation in various cancer cell lines, and due to its kinase inhibition profile, it also serves as a tool compound for studying resistance mechanisms to targeted cancer therapies. Researchers use PP121 to explore combination treatments with other anticancer agents to improve therapeutic efficacy and overcome drug resistance.