PD 184161 is primarily used in research settings as a selective inhibitor of MEK1 and MEK2, which are key components of the MAPK/ERK signaling pathway. This pathway is crucial for cell proliferation, differentiation, and survival, making PD 184161 a valuable tool for studying cancer biology and other diseases where this pathway is dysregulated. By inhibiting MEK1/2, it helps researchers understand the role of these kinases in tumor growth and progression, aiding in the development of targeted cancer therapies. Additionally, it is used in cellular and molecular biology experiments to explore signaling mechanisms and validate the involvement of the MAPK/ERK pathway in various physiological and pathological processes.