Identification of Novel NaV1.7 Antagonists Using High Throughput Screening Platforms

Goran      Klement; Olga      Babich; Olof      Larsson; Per-Eric      Lund; Asa      Malmberg; Lars      Sandberg; Zara      A. Sands; Michael      Dabrowski

doi:10.2174/138620712803519680

Abstract

Congenital Insensitivity to Pain (CIP) is a loss of function mutation resulting in a truncated NaV1.7 protein, suggesting a pivotal role in pain signaling and rendering it an important pharmaceutical target for multiple pain conditions. The structural homology in the NaV-channel family makes it challenging to design effective analgesic compounds without inducing for example cardiotoxicity or seizure liabilities. An additional approach to structural isoform selectivity is to identify compounds with use- or state-dependent profiles, i.e. inhibition efficacy based on the gating of the ion channel. In general nerve cells in damaged or inflamed tissue are more depolarized and electrically active compared to healthy nerve cells in for instance the heart. This observation has led to the design of two types of screening protocols emulating the voltage condition of peripheral neurons or cardiac tissue. The two voltage protocols have been developed to identify both use- and state-dependent antagonists. In this paper we describe an attempt to merge the two different protocols into one to increase screening efficacy, while retaining relevant state- and use-dependent pharmacology. The new protocol is constructed of two stimulation pulses and a slow voltage ramp for simultaneous assessment of resting and state-dependent block. By comparing all protocols we show that the new protocol indeed filter compounds for statedependence and increase the prediction power of selecting use-dependent compounds.

Keywords: Analgesic, antagonist, IonWorks, screening protocol, sodium ion channel, state-dependence, use-dependence, NaV1.7 Antagonists, voltage condition, nerve cells