Identification of a New Class of Inhibitors of the Voltage-Gated Potassium Channel, Kv1.3, with Immunosuppressant Properties

The voltage-gated potassium channel, Kv1.3, is a novel target for development of immunosuppressants. Using a functional 86Rb+ efflux assay, a new class of high-affinity Kv1.3 inhibitors has been identified. The initial active in this series, 4-phenyl-4-[3-(2-methoxyphenyl)-3-oxo-2-azaprop-1-yl]cyclohexanone (PAC), which is representative of a disubstituted cyclohexyl (DSC) template, displays a K i of ca. 300 nM and a Hill coefficient near 2 in the flux assay and in voltage clamp recordings of Kv1.3 channels in human T-lymphocytes. PAC displays excellent specificity as it only blocks members of the Kv1 family of potassium channels but does not affect many other types of ion channels, receptors, or enzyme systems. Block of Kv1.3 by DSC analogues occurs with a well-defined structure−activity relationship. Substitution at the C-1 ketone of PAC generates trans (down) and cis (up) isomer pairs. Whereas many DSC derivatives do not display selectivity in their interaction with different Kv1.x channels, trans DSC derivatives distinguish between Kv1.x channels based on their rates of C-type inactivation. DSC analogues reversibly inhibit the Ca2+-dependent pathway of T cell activation in in vitro assays. Together, these data suggest that DSC derivatives represent a new class of immunosuppressant agents and that specific interactions of trans DSC analogues with channel conformations related to C-type inactivation may permit development of selective Kv1.3 channel inhibitors useful for the safe treatment of autoimmune diseases.