Background & Aims
Histamine-independent itching accompanies various disorders and is often resistant to existing treatments. Slack (also termed KNa1.1, Kcnt1, or Slo2.2), a potassium channel highly expressed in itch-sensitive sensory neurons, has been considered as a potential target for antipruritic therapies (Lu et al. 2015; Martinez-Epinosa et al. 2015). This study aimed to develop of a series of new Slack activators based on the Slack-activating antipsychotic drug, loxapine (Biton et al. 2012), with improved pharmacodynamic and pharmacokinetic profiles. Using these new compounds, we aimed to validate Slack as a novel target for itch treatment.
Methods
The Slack-activating properties of novel compounds were tested in HEK-293 cells stably expressing human Slack (HEK-Slack) using the FluxOR potassium ion channel assay and patch-clamp recordings. Receptor binding assays were performed to evaluate potential off-target effects. Pharmacokinetic properties of the most promising candidates were assessed in mice. The antipruritic efficacy of the most promising candidate, compound 6, was investigated in various mouse models of histamine-independent and chronic itch. Patch-clamp recordings in sensitized murine DRG neurons were performed to analyze how neuronal excitability is affected by compound 6.
Results
In the present study, a series of novel Slack activators were developed, of which 8 compounds were considered to be the most interesting candidates. Among these Slack activators, compound 6 exhibited neglible binding to dopamine D2 and D3 receptors, in contrast to loxapine, and showed excellent pharmacokinetic properties. Of note, compound 6 significantly reduced the scratching behavior in various mouse models of histamine-independent and chronic itch without motor side effects. Patch-clamp recordings confirmed that compound 6 inhibited the excitability of itch-sensitive DRG neurons ex vivo.
Conclusions
These results suggest that compound 6 could be a promising lead molecule for developing an antipruritic therapy targeting Slack channels (Balzulat et al. 2024).
References
Balzulat, A., Zhu, W.F., Flauaus, C., Hernandez-Olmos, V., Heering, J., Sethumadhavan, S., Dubiel, M., et al. (2024). Discovery of A Small Molecule Activator of Slack (Kcnt1) Potassium Channels That Significantly Reduces Scratching in Mouse Models of Histamine-Independent and Chronic Itch. Advanced Science. In press. DOI: https://doi.org/10.1002/advs.202307237.
Biton, B., Sethuramanujam, S., Picchione, K.E., Bhattacharjee, A., Khessibi, N., Chesney, F., Lanneau, C., et al. (2012). The antipsychotic drug loxapine is an opener of the sodium-activated potassium channel slack (Slo2.2). The Journal of pharmacology and experimental therapeutics 340, 706-715. DOI: https://doi.org/10.1124/jpet.111.184622.
Lu, R., Bausch, A.E., Kallenborn-Gerhardt, W., Stoetzer, C., Debruin, N., Ruth, P., Geisslinger, G., et al. (2015). Slack channels expressed in sensory neurons control neuropathic pain in mice. J. Neurosci. 35, 1125-1135. DOI: https://doi.org/10.1523/JNEUROSCI.2423-14.2015.
Martinez-Epinosa, P.L., Wu, J., Yang, C., Gonzalez-perez, V., Zhou, H., Liang, H., Xia, X.-m., et al. (2015). Knockout of Slo2.2 enhances itch, abolishes KNa current, and increases action potential firing frequency in DRG neurons. eLife Sciences Publications, Ltd. DOI: https://doi.org/10.7554/eLife.10013.
Presenting Author
Annika Balzulat
Poster Authors
Annika Balzulat
PhD
Goethe university
Lead Author
Topics
- Treatment/Management: Pharmacology: Novel Targets