Publication Details

McArthur, J. R., Motin, L., Gleeson, E. C., Spiller, S., Lewis, R. J., Duggan, P. J., Tuck, K. L. & Adams, D. J. (2018). Inhibition of human N- and T-type calcium channels by an ortho-phenoxyanilide derivative, MONIRO-1. British Journal of Pharmacology, 175 (12), 2284-2295.


Background and Purpose: Voltage-gated calcium channels are involved in nociception in the CNS and in the periphery. N-type (Cav2.2) and T-type (Cav3.1, Cav3.2 and Cav3.3) voltage-gated calcium channels are particularly important in studying and treating pain and epilepsy. Experimental Approach: In this study, whole-cell patch clamp electrophysiology was used to assess the potency and mechanism of action of a novel ortho-phenoxylanilide derivative, MONIRO-1, against a panel of voltage-gated calcium channels including Cav1.2, Cav1.3, Cav2.1, Cav2.2, Cav2.3, Cav3.1, Cav3.2 and Cav3.3. Key Results: MONIRO-1 was 5- to 20-fold more potent at inhibiting human T-type calcium channels, hCav3.1, hCav3.2 and hCav3.3 (IC50 : 3.3 ± 0.3, 1.7 ± 0.1 and 7.2 ± 0.3 μM, respectively) than N-type calcium channel, hCav2.2 (IC50 : 34.0 ± 3.6 μM). It interacted with L-type calcium channels Cav1.2 and Cav1.3 with significantly lower potency (IC50 > 100 μM) and did not inhibit hCav2.1 or hCav2.3 channels at concentrations as high as 100 μM. State- and use-dependent inhibition of hCav2.2 channels was observed, whereas stronger inhibition occurred at high stimulation frequencies for hCav3.1 channels suggesting a different mode of action between these two channels. Conclusions and Implications: Selectivity, potency, reversibility and multi-modal effects distinguish MONIRO-1 from other low MW inhibitors acting on Ca v channels involved in pain and/or epilepsy pathways. High-frequency firing increased the affinity for MONIRO-1 for both hCav2.2 and hCav3.1 channels. Such Cav channel modulators have potential clinical use in the treatment of epilepsies, neuropathic pain and other nociceptive pathophysiologies.

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