Serlopitant is a small molecule, highly selective NK1-R antagonist. Two critical mediators of the urge to scratch and the urge to cough are Substance P, or SP, and its receptor, the neurokinin-1 receptor, or NK1-R. SP is a naturally occurring peptide in the tachykinin neuropeptide family. Tachykinins have a broad range of functions in the nervous and immune systems. SP binding of NK1-R has been shown to be a key mediator of sensory nerve signaling, including the itch-scratch reflex, the cough reflex and the vomiting reflex. Accordingly, the biological bases of our pruritus and cough programs are similar and have been shown to involve SP and NK1-R in the signaling process. The following figure illustrates the role of NK1-R in itch and cough signaling: