Characterization of Novel Cannabinoid Based T-Type Calcium Channel Blockers with Analgesic Effects

Abstract

Low-voltage-activated (T-type) calcium channels are important regulators of the transmission of nociceptive information in the primary afferent pathway and finding ligands that modulate these channels is a key focus of the drug discovery field. Recently, we characterized a set of novel compounds with mixed cannabinoid receptor/T-type channel blocking activity and examined their analgesic effects in animal models of pain. Here, we have built on these previous findings and synthesized a new series of small organic compounds. We then screened them using whole-cell voltage clamp techniques to identify the most potent T-type calcium channel inhibitors. The two most potent blockers (compounds 9 and 10) were then characterized using radioligand binding assays to determine their affinity for CB1 and CB2 receptors. The structure–activity relationship and optimization studies have led to the discovery of a new T-type calcium channel blocker, compound 9. Compound 9 was efficacious in mediating analgesia in mouse models of acute inflammatory pain and in reducing tactile allodynia in the partial nerve ligation model. This compound was shown to be ineffective in Cav3.2 T-type calcium channel null mice at therapeutically relevant concentrations, and it caused no significant motor deficits in open field tests. Taken together, our data reveal a novel class of compounds whose physiological and therapeutic actions are mediated through block of Cav3.2 calcium channels.

Effect of the T-type channel blocker KYS-05090S in mouse models of acute and neuropathic pain

“…Cav3.2 null mice display a lower nociceptive response compared to wild-type mice in both phases of the formalin test [2,7,12] (Fig. 4).…”

“…On the other hand, Cav3.2 knockout mice have reduced pain responses [7] and knockdown of Cav3.2 channels with antisense oligonucleotides by intrathecal injection mediated potent analgesia in different models of chronic pain [3]. Therefore, various blockers of Cav3.2 channels have been shown to mediate analgesia in models of inflammatory and neuropathic pain [1,2,11]. Some of the known T-type calcium channel inhibitors with analgesic actions have been shown to also block other types of ion channels, such as N-type calcium channels [13] and voltage-gated sodium channels [18] that are also important for the transmission of pain-related information.…”

The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

“…This compound has completed phase1b clinical trials for pain and is being advanced into phase 2 trials. A series of compounds that combine the carbazole core of NMP-7 and features of Z944 also mediate potent Ca V 3 channel inhibition without off-target effects on cannabinoid receptors and with efficacy in several in vivo models of pain (Bladen et al, 2015). Another series of compounds that incorporates features of Z944 includes TTA-A2 [(R)-2-(4-cyclopropylphenyl)-N-(1-(5-(2,2,2-trifluoroethoxy) pyridin-2-yl)ethyl) acetamide] and TTA-P2 [3,5-dichloro-N-[1-(2,2-dimethyl-tetrahydro-pyran-4-ylmethyl)-4-fluoro-piperidin-4-ylmethyl]-benzamide] (Choe et al, 2011;Francois et al, 2013), both of which mediate state-dependent inhibition of T-type currents with a preference for Ca V 3.2.…”

Etiology and Pharmacology of Neuropathic Pain

“…Some of these substances have not yet been tested in the clinic, whereas others have yielded Gagnon et al, 2013 KYS05090S or ABT-639. . Small-molecule T-channel blockers Jarvis et al, 2014;Zhang et al, 2015a;M'Dahoma et al, 2016 N-((1-(2-(tertbutylamino)-2-oxoethyl)piperidin-4-yl)methyl)-9-pentyl-9Hcarbazole-3-carboxamide CB2 agonist that targets Ca v 3.2 T-type channels Berger et al, 2014;Bladen et al, 2015;Snutch and Zamponi, 2017 A-1264087 State-dependent Ca v 2 blockers Oral administration of all of these drugs displays antiallodynic efficacy in rodent models (Patel et al, 2017) Under development Zamponi et al, 2015 Coull et al (2003) showed that a decrease in transmembrane chloride gradient occurred in rat dorsal horn lamina I neurons following peripheral nerve injury as a result of a reduction in expression of the potassium-chloride exporter, potassium-chloride exporter 2 (KCC2). The resulting accumulation of intracellular Cl 2 can cause normally inhibitory GABAergic, anionic, outward synaptic currents to become inward excitatory currents (Coull et al, 2003;Prescott et al, 2006).…”