Recent findings have shown that KCC2, a neuronal-specific potassium-chloride (K-Cl) Cotransporter, modulates inhibitory neurotransmission in the CNS and spinal cord. Loss of function of this cotransporter within selective regions of the nervous system has been linked to the potential development of neuropathic pain. This project proposed to identify small molecule ligands (both agonists and antagonists) of the neuronal KCC2 Cotransporter that are cell permeable, exhibit submicromolar potency, and show greater than 10-fold selectivity over other closely related NKCC transporters. This probe report describes ML077 (CID-25067404), a highly selective, potent, saline soluble, "best in class" KCC2 antagonist for high fidelity in vitro studies on KCC2 function.