Background & Aims

Voltage-gated sodium channels, or NaV channels, control the excitability of neurons in the peripheral and central nervous systems. NaV1.8 is specifically expressed in DRG neurons in the peripheral nervous system. NaV1.8 is both a genetically and pharmacologically validated pain target in humans. Herein, we describe the pharmacology, interaction site and mechanism of action of LTGO-33, a new small molecule inhibitor of NaV1.8.

Methods

Human NaV1.8 was transiently or stably expressed in ND7/23 or HEK293 cells respectively and currents measured using whole-cell patch clamp electrophysiology. Native NaV1.8 currents were recorded in mouse, rat, dog, cyno and human DRG neurons and neuronal excitability was evaluated in human DRG neurons using current clamp recordings. Molecular biology techniques including site-directed mutagenesis were employed to generate human-rat NaV1.8 chimeras and to map domains and specific residues required for LTGO-33 inhibition.

Results

LTGO-33 potently inhibited NaV1.8 with greater than 600-fold selectivity over NaV1.1-NaV1.7 and NaV1.9. LTGO-33 exhibited state independent inhibition with similar potencies on closed/resting channels and inactivated channels. LTGO-33 inhibited native NaV1.8 currents in both cyno and human DRG neurons, where it reduced action potential firing, with reduced potency on rodent and dog DRG neurons. The compound inhibited NaV1.8 through interaction with a novel site involving the extracellular region of VSDII to stabilize the deactivated state. LTGO-33 inhibited NaV1.8 variants associated with diverse human pain disorders with comparable potency to wild-type NaV1.8.

Conclusions

LTGO-33 inhibited NaV1.8 through unique a mechanism of action and novel interaction site previously undescribed in NaV1.8 small molecule pharmacologic space.

References

None

Presenting Author

Bryan D. Moyer

Poster Authors

Bryan Moyer

PhD

Latigo Biotherapeutics

Lead Author

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Topics

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