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. 2022 Dec;16(1):230-243.
doi: 10.1080/19336950.2022.2122309.

Association of respiratory failure with inhibition of NaV1.6 in the phrenic nerve

Rebecca M Klein  1 , Mark E Layton, Hillary Regan, Christopher P Regan, Yuxing Li, Tracey Filzen, Matt Cato, Michelle K Clements, Jixin Wang, Raul Sanoja, Thomas J Greshock, Anthony J Roecker, Joseph E Pero, Ron Kim, Christopher Burgey, Christopher T John, Ying-Hong Wang, Neetesh Bhandari, Arie Struyk, Richard L Kraus, Darrell A Henze, Andrea K Houghton
Affiliations

Association of respiratory failure with inhibition of NaV1.6 in the phrenic nerve

Rebecca M Klein et al. Channels (Austin). 2022 Dec.

Abstract

As part of a drug discovery effort to identify potent inhibitors of NaV1.7 for the treatment of pain, we observed that inhibitors produced unexpected cardiovascular and respiratory effects in vivo. Specifically, inhibitors administered to rodents produced changes in cardiovascular parameters and respiratory cessation. We sought to determine the mechanism of the in vivo adverse effects by studying the selectivity of the compounds on NaV1.5, NaV1.4, and NaV1.6 in in vitro and ex vivo assays. Inhibitors lacking sufficient NaV1.7 selectivity over NaV1.6 were associated with respiratory cessation after in vivo administration to rodents. Effects on respiratory rate in rats were consistent with effects in an ex vivo hemisected rat diaphragm model and in vitro NaV1.6 potency. Furthermore, direct blockade of the phrenic nerve signaling was observed at exposures known to cause respiratory cessation in rats. Collectively, these results support a significant role for NaV1.6 in phrenic nerve signaling and respiratory function.

Keywords: Sodium channel inhibitor; phrenic nerve; respiration; selectivity.

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Conflict of interest statement

At the time this research was conducted, all authors were employees of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA the sponsor of the research.

Figures

Figure 1.
Figure 1.
Structures of NaV1.7 inhibitors.
Figure 2.
Figure 2.
Inhibition of NaV1.6 currents in HEK-293 cells. (a). Representative manual electrophysiology traces for SSCI-4 applied to HEK-293 cells stably expressing human NaV1.6 as described in the Methods. Five concentrations of SSCI-4 are shown (100, 300, 1000, 3000, and 30,000 nM, blue traces) and a vehicle trace (black trace) obtained prior to compound application. (b). In vitro potencies were measured as described in the Methods. For each SSCI, then percent inhibition is plotted as a function of log concentration, then fit with the Hill Equation to determine the IC50 value for that compound.
Figure 3.
Figure 3.
Respiratory effects of SSCI-4 and SSCI-5 in anesthetized rats.
Figure 4.
Figure 4.
Dose Response Data for NaV1.7 Inhibitors in Rat HMD Assay.
Figure 5.
Figure 5.
Effects of NaV1.6 Inhibitors on Rat Phrenic Nerve Activity.
Figure 6.
Figure 6.
Effect of NaV1.7 Inhibitors on Rat Respiratory Rate (blue = human NaV1.6 IC50; red = rat NaV1.6 IC50, green = HMD IC50).
See this image and copyright information in PMC

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