Scott VE, Vortherms TA, Niforatos W, Swensen AM, Neelands T, Milicic I, Banfor PN, King A, Zhong C, Simler G, Zhan C, Bratcher N, Boyce-Rustay JM, Zhu CZ, Bhatia P, Doherty G, Mack H, Stewart AO, Jarvis MF. A-1048400 is a novel, orally active, state-dependent neuronal calcium channel blocker that produces dose-dependent antinociception without altering hemodynamic function in rats.
Biochem Pharmacol 2012;
83:406-18. [PMID:
22153861 DOI:
10.1016/j.bcp.2011.10.019]
[Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 10/31/2011] [Accepted: 10/31/2011] [Indexed: 11/21/2022]
Abstract
Blockade of voltage-gated Ca²⁺ channels on sensory nerves attenuates neurotransmitter release and membrane hyperexcitability associated with chronic pain states. Identification of small molecule Ca²⁺ channel blockers that produce significant antinociception in the absence of deleterious hemodynamic effects has been challenging. In this report, two novel structurally related compounds, A-686085 and A-1048400, were identified that potently block N-type (IC₅₀=0.8 μM and 1.4 μM, respectively) and T-type (IC₅₀=4.6 μM and 1.2 μM, respectively) Ca²⁺ channels in FLIPR based Ca²⁺ flux assays. A-686085 also potently blocked L-type Ca²⁺ channels (EC₅₀=0.6 μM), however, A-1048400 was much less active in blocking this channel (EC₅₀=28 μM). Both compounds dose-dependently reversed tactile allodynia in a model of capsaicin-induced secondary hypersensitivity with similar potencies (EC₅₀=300-365 ng/ml). However, A-686085 produced dose-related decreases in mean arterial pressure at antinociceptive plasma concentrations in the rat, while A-1048400 did not significantly alter hemodynamic function at supra-efficacious plasma concentrations. Electrophysiological studies demonstrated that A-1048400 blocks native N- and T-type Ca²⁺ currents in rat dorsal root ganglion neurons (IC₅₀=3.0 μM and 1.6 μM, respectively) in a voltage-dependent fashion. In other experimental pain models, A-1048400 dose-dependently attenuated nociceptive, neuropathic and inflammatory pain at doses that did not alter psychomotor or hemodynamic function. The identification of A-1048400 provides further evidence that voltage-dependent inhibition of neuronal Ca²⁺ channels coupled with pharmacological selectivity vs. L-type Ca²⁺ channels can provide robust antinociception in the absence of deleterious effects on hemodynamic or psychomotor function.
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