CP-100356 hydrochloride is primarily used in research settings to study the function and inhibition of multidrug resistance proteins, particularly P-glycoprotein. It serves as a potent inhibitor, helping scientists understand the mechanisms by which cancer cells develop resistance to chemotherapy drugs. This compound is valuable in preclinical studies aimed at enhancing the efficacy of anticancer treatments by preventing the efflux of therapeutic agents from cancer cells. Additionally, it is utilized in pharmacological experiments to explore drug transport across biological barriers, such as the blood-brain barrier, which is critical for developing treatments for neurological disorders. Its role in modulating drug distribution and resistance makes it a significant tool in advancing drug development and therapeutic strategies.