Used in research to study neurokinin-1 (NK1) receptor interactions, particularly in pain signaling and neuroinflammatory pathways. Acts as a selective antagonist or modulator, helping investigate the role of substance P in conditions like chronic pain, migraine, and depression. Commonly applied in in vitro assays and animal models to evaluate receptor binding and functional responses. Also utilized in developing targeted therapies for cancer and neurological disorders due to its ability to cross the blood-brain barrier in some experimental setups.