RO9021 is primarily used in research settings as a potent and selective inhibitor of protein kinase C (PKC) isoforms. Its main application lies in studying signal transduction pathways involved in cellular proliferation, differentiation, and apoptosis. Due to its ability to modulate PKC activity, it has been utilized in investigations related to cancer biology, particularly in assessing tumor growth and resistance mechanisms. It also serves as a tool compound in neuroscience research, where PKC signaling plays a role in synaptic plasticity and neurodegenerative conditions. RO9021's selectivity makes it valuable for dissecting the specific roles of PKC subtypes without broad off-target effects, supporting its use in mechanistic studies and early-stage drug discovery.