Design of Aminobenzothiazole Inhibitors of Rho Kinases 1 and 2 by Using Protein Kinase A as a Structure Surrogate.

We describe the design, synthesis, and structure-activity relationships (SARs) of a series of 2-aminobenzothiazole inhibitors of Rho kinases (ROCKs) 1 and 2, which were optimized to low nanomolar potencies by use of protein kinase A (PKA) as a structure surrogate to guide compound design. A subset of these molecules also showed robust activity in a cell-based myosin phosphatase assay and in a mechanical hyperalgesia in vivo pain model.

Synthesis and Pharmacology of (Pyridin-2-yl)methanol Derivatives as Novel and Selective Transient Receptor Potential Vanilloid 3 Antagonists.

Transient receptor potential vanilloid 3 (TRPV3) is a Ca(2+)- and Na(+)-permeable channel with a unique expression pattern. TRPV3 is found in both neuronal and non-neuronal tissues, including dorsal root ganglia, spinal cord, and keratinocytes. Recent studies suggest that TRPV3 may play a role in inflammation, pain sensation, and skin disorders.

Discovery of (R)-1-(7-chloro-2,2-bis(fluoromethyl)chroman-4-yl)-3-(3-methylisoquinolin-5-yl)urea (A-1165442): a temperature-neutral transient receptor potential vanilloid-1 (TRPV1) antagonist with analgesic efficacy.

The synthesis and characterization of a series of selective, orally bioavailable 1-(chroman-4-yl)urea TRPV1 antagonists is described. Whereas first-generation antagonists that inhibit all modes of TRPV1 activation can elicit hyperthermia, the compounds disclosed herein do not elevate core body temperature in preclinical models and only partially block acid activation of TRPV1. Advancing the SAR of this series led to the eventual identification of (R)-1-(7-chloro-2,2-bis(fluoromethyl)chroman-4-yl)-3-(3-methylisoquinolin-5-yl)urea (A-1165442, 52), an analogue that possesses excellent pharmacological selectivity, has a favorable pharmacokinetic profile, and demonstrates good efficacy against osteoarthritis pain in rodents.

Quantification of TRPV1 protein levels in rat tissues to understand its physiological roles.

Transient receptor potential subfamily V, member 1 (TRPV1) is a nonselective cation channel expressed in both the peripheral and central nervous systems (CNS). TRPV1 protein levels in rat tissues were determined under normal and pain states using enzyme-linked immunosorbent assay. In naive rats, brain TRPV1 protein concentrations ranged from 1.

An oral TRPV1 antagonist attenuates laser radiant-heat-evoked potentials and pain ratings from UV(B)-inflamed and normal skin.

Aims: Laser (radiant-heat) evoked potentials (LEPs) from vertex-EEG peak-to-peak (PtP) amplitude were used to determine acute antinociceptive/antihyperalgesic efficacy of ABT-102, a novel TRPV1 antagonist efficacious in preclinical pain models, compared with active controls and placebo in normal and UV(B)-inflamed skin.

Methods: This was a randomized, placebo- and active-controlled, double-blind, intra-individual, crossover trial. Twenty-four healthy subjects received six sequences of single doses of ABT-102 (0.

Pharmacology of modality-specific transient receptor potential vanilloid-1 antagonists that do not alter body temperature.

The transient receptor potential vanilloid-1 (TRPV1) channel is involved in the development and maintenance of pain and participates in the regulation of temperature. The channel is activated by diverse agents, including capsaicin, noxious heat (≥ 43°C), acidic pH (< 6), and endogenous lipids including N-arachidonoyl dopamine (NADA). Antagonists that block all modes of TRPV1 activation elicit hyperthermia.

Synthesis and in vitro activity of N-benzyl-1-(2,3-dichlorophenyl)-1H-tetrazol-5-amine P2X(7) antagonists.

Synthesis and biological evaluation of a novel class of substituted N-benzyl-1-(2,3-dichlorophenyl)-1H-tetrazol-5-amine derivatives resulted in the identification of potent P2X(7) antagonists. These compounds were assayed for activity at both the human and rat P2X(7) receptors. On the benzyl moiety, a variety of functional groups were tolerated, including both electron-withdrawing and electron-donating substituents.

Selective blockade of TRPA1 channel attenuates pathological pain without altering noxious cold sensation or body temperature regulation.

Despite the increasing interest in TRPA1 channel as a pain target, its role in cold sensation and body temperature regulation is not clear; the efficacy and particularly side effects resulting from channel blockade remain poorly understood. Here we use a potent, selective, and bioavailable antagonist to address these issues. A-967079 potently blocks human (IC(50): 51 nmol/L, electrophysiology, 67 nmol/L, Ca(2+) assay) and rat TRPA1 (IC(50): 101 nmol/L, electrophysiology, 289 nmol/L, Ca(2+) assay).

Chroman and tetrahydroquinoline ureas as potent TRPV1 antagonists.

Novel chroman and tetrahydroquinoline ureas were synthesized and evaluated for their activity as TRPV1 antagonists. It was found that aryl substituents on the 7- or 8-position of both bicyclic scaffolds imparted the best in vitro potency at TRPV1. The most potent chroman ureas were assessed in chronic and acute pain models, and compounds with the ability to cross the blood-brain barrier were shown to be highly efficacious.

Discovery and biological evaluation of potent, selective, orally bioavailable, pyrazine-based blockers of the Na(v)1.8 sodium channel with efficacy in a model of neuropathic pain.

Na(v)1.8 (also known as PN3) is a tetrodotoxin-resistant (TTx-r) voltage-gated sodium channel (VGSC) that is highly expressed on small diameter sensory neurons. It has been implicated in the pathophysiology of inflammatory and neuropathic pain, and we envisioned that selective blockade of Na(v)1.

Subtype-selective Na(v)1.8 sodium channel blockers: identification of potent, orally active nicotinamide derivatives.

A series of aryl-substituted nicotinamide derivatives with selective inhibitory activity against the Na(v)1.8 sodium channel is reported. Replacement of the furan nucleus and homologation of the anilide linker in subtype-selective blocker A-803467 (1) provided potent, selective derivatives with improved aqueous solubility and oral bioavailability.

A-995662 [(R)-8-(4-methyl-5-(4-(trifluoromethyl)phenyl)oxazol-2-ylamino)-1,2,3,4-tetrahydronaphthalen-2-ol], a novel, selective TRPV1 receptor antagonist, reduces spinal release of glutamate and CGRP in a rat knee joint pain model.

The TRPV1 antagonist A-995662 demonstrates analgesic efficacy in monoiodoacetate-induced osteoarthritic (OA) pain in rat, and repeated dosing results in increased in vivo potency and a prolonged duration of action. To identify possible mechanism(s) underlying these observations, release of neuropeptides and the neurotransmitter glutamate from isolated spinal cord was measured. In OA rats, basal release of glutamate, bradykinin and calcitonin gene-related peptide (CGRP) was significantly elevated compared to naïve levels, whereas substance P (SP) levels were not changed.

A-887826 is a structurally novel, potent and voltage-dependent Na(v)1.8 sodium channel blocker that attenuates neuropathic tactile allodynia in rats.

Activation of sodium channels is essential to action potential generation and propagation. Recent genetic and pharmacological evidence indicates that activation of Na(v)1.8 channels contributes to chronic pain.

Discovery of TRPV1 antagonist ABT-116.

The synthesis and SAR of a series of indazole TRPV1 antagonists leading to the discovery of 21 (ABT-116) is described. Biological studies demonstrated potent in vitro and in vivo activity for 21, as well as suitable physicochemical and pharmacokinetic properties for advancement to clinical development for pain management.

Discovery and biological evaluation of novel cyanoguanidine P2X(7) antagonists with analgesic activity in a rat model of neuropathic pain.

We disclose the design of a novel series of cyanoguanidines that are potent (IC(50) approximately 10-100 nM) and selective (> or = 100-fold) P2X(7) receptor antagonists against the other P2 receptor subtypes such as the P2Y(2), P2X(4), and P2X(3). We also found that these P2X(7) antagonists effectively reduced nociception in a rat model of neuropathic pain (Chung model). Particularly, analogue 53 proved to be effective in the Chung model, with an ED(50) of 38 micromol/kg after intraperitoneal administration.

Antagonism of TRPV1 receptors indirectly modulates activity of thermoregulatory neurons in the medial preoptic area of rats.

In order to enhance understanding of TRPV1 contributions to thermoregulation, we measured the effects of a TRPV1 receptor antagonist, A-889425, on thermoregulatory neurons in the medial preoptic area of the hypothalamus (mPOA) of rats while simultaneously monitoring rectal temperature (T(r)). Administration of A-889425 (4 micromol/kg, i.v.

Pore dilation occurs in TRPA1 but not in TRPM8 channels.

Abundantly expressed in pain-sensing neurons, TRPV1, TRPA1 and TRPM8 are major cellular sensors of thermal, chemical and mechanical stimuli. The function of these ion channels has been attributed to their selective permeation of small cations (e.g.

Repeated dosing of ABT-102, a potent and selective TRPV1 antagonist, enhances TRPV1-mediated analgesic activity in rodents, but attenuates antagonist-induced hyperthermia.

Transient receptor potential vanilloid type 1 (TRPV1) is a ligand-gated ion channel that functions as an integrator of multiple pain stimuli including heat, acid, capsaicin and a variety of putative endogenous lipid ligands. TRPV1 antagonists have been shown to decrease inflammatory pain in animal models and to produce limited hyperthermia at analgesic doses. Here, we report that ABT-102, which is a potent and selective TRPV1 antagonist, is effective in blocking nociception in rodent models of inflammatory, post-operative, osteoarthritic, and bone cancer pain.

Contributions of central and peripheral TRPV1 receptors to mechanically evoked and spontaneous firing of spinal neurons in inflamed rats.

TRPV1 receptors are activated and/or modulated by noxious heat, capsaicin, protons and other endogenous agents released following tissue injury. There is a growing appreciation that this molecular integrator may also have a role in mechanosensation. To further understand this role, we investigated the systemic and site-specific effects of a selective TRPV1 receptor antagonist, A-889425, on low-intensity mechanical stimulation in inflamed rats.

Characterization of A-425619 at native TRPV1 receptors: a comparison between dorsal root ganglia and trigeminal ganglia.

1-isoquinolin-5-yl-3-(4-trifluoromethyl-benzyl)-urea (A-425619), a novel, potent, and selective transient receptor potential type V1 (TRPV1) antagonist, attenuates pain associated with inflammation and tissue injury in rats. The purpose of this study was to extend the in vitro characterization of A-425619 to native TRPV1 receptors and to compare the pharmacological properties of TRPV1 receptors in the dorsal root ganglion with trigeminal ganglion neurons. A robust increase in intracellular Ca(2+) was elicited by a variety of TRPV1 agonists with similar rank order of potency between both cultures: resiniferatoxin>tinyatoxin>capsaicin>N-arachidonoyl-dopamine (NADA).

Tetrahydropyridine-4-carboxamides as novel, potent transient receptor potential vanilloid 1 (TRPV1) antagonists.

A series of 1,2,3,6-tetrahydropyridyl-4-carboxamides, exemplified by 6, have been synthesized and evaluated for in vitro TRPV1 antagonist activity, and in vivo analgesic activity in animal pain models. The tetrahydropyridine 6 is a novel TRPV1 receptor antagonist that potently inhibits receptor-mediated Ca2+ influx in vitro induced by several agonists, including capsaicin, N-arachidonoyldopamine (NADA), and low pH. This compound penetrates the CNS and shows potent anti-nociceptive effects in a broad range of animal pain models upon oral dosing due in part to its ability to antagonize both central and peripheral TRPV1 receptors.

(R)-(5-tert-butyl-2,3-dihydro-1H-inden-1-yl)-3-(1H-indazol-4-yl)-urea (ABT-102) blocks polymodal activation of transient receptor potential vanilloid 1 receptors in vitro and heat-evoked firing of spinal dorsal horn neurons in vivo.

The transient receptor potential vanilloid (TRPV) 1 receptor, a nonselective cation channel expressed on peripheral sensory neurons and in the central nervous system, plays a key role in pain. TRPV1 receptor antagonism is a promising approach for pain management. In this report, we describe the pharmacological and functional characteristics of a structurally novel TRPV1 antagonist, (R)-(5-tert-butyl-2,3-dihydro-1H-inden-1-yl)-3-(1H-indazol-4-yl)-urea (ABT-102), which has entered clinical trials.

Discovery of potent furan piperazine sodium channel blockers for treatment of neuropathic pain.

The synthesis and pharmacological characterization of a novel furan-based class of voltage-gated sodium channel blockers is reported. Compounds were evaluated for their ability to block the tetrodotoxin-resistant sodium channel Na(v)1.8 (PN3) as well as the Na(v)1.

Molecular determinants of species-specific activation or blockade of TRPA1 channels.

TRPA1 is an excitatory, nonselective cation channel implicated in somatosensory function, pain, and neurogenic inflammation. Through covalent modification of cysteine and lysine residues, TRPA1 can be activated by electrophilic compounds, including active ingredients of pungent natural products (e.g.