A 841720

A 841720 is a novel non-competitive antagonist of metabotropic glutamate receptor 1 (mGluR1), with an IC50 value of 10.7 nM to 10 µM L-glutamate-induced calcium release at human mGluR1 receptors [1].

Glutamate as the major excitatory neurotransmitter in the central nervous system functions through two types of receptors, ionotropic glutamate receptors and metabotropic glutamate receptors (mGluRs). MGluRs includes group I mGluRs (mGluR1 and mGluR5 receptors), group II (mGluR2 and mGluR3 receptors) and group III (mGluR4, 6, 7, 8 receptors) [1].

In cells, agonist-induced calcium release was concentration-dependently inhibited by A 841720 in a human mGluR5 receptor FLIPR functional assay. But the IC50 value was just 343 nM. In cells expressing recombinant mGluR5 receptors, A 841720 did not block agonist-induced response. In the human mGluR1 receptor FLIPR assay, the log concentration-response curve was shifted by A 841720 at 10 nM to the right. A 841720 at increasing concentrations profoundly reduced the amplitude of L-quisqualate-evoked calcium release. A 841720 at 30 nM reduced the maximal agonist-induced response by 38%. L-quisqualate-induced response was completely abolished by A 841720 at 100 nM [1].

In a water maze test, all rats gradually learned to locate the submerged platform. Treatment with A 841720 significantly slowered rats to find the platform than vehicle control rats. Rats treated with A 841720 at both 30 and 100 µmol/kg doses not only significantly traveled longer distance to find the hidden platform, but also significantly spent longer time to reach the platform [1].

Reference:
[1].  El-Kouhen O, Lehto SG, Pan JB, et al. Blockade of mGluR1 receptor results in analgesia and disruption of motor and cognitive performances: effects of A-841720, a novel non-competitive mGluR1 receptor antagonist. British journal of pharmacology, 2006, 149(6): 761-774.

Comparison of the mGluR1 antagonist A-841720 in rat models of pain and cognition.[Pubmed:17551319]

Behav Pharmacol. 2007 Jul;18(4):273-81.

In the current study we compared the potency of the selective metabotropic glutamate receptor (mGluR1) antagonist A-841720 (7-Azepan-1-yl-4-dimethylamino-7H-9-thia-1,5,7-triaza-fluoren-8-one) in rodent models of pain with its effects in models of learning and memory, to obtain information regarding the therapeutic window of this compound. A-841720 significantly reduced formalin-induced behaviours and complete Freund's adjuvant (CFA)-induced tactile allodynia, starting at doses of 1 and 10 mg/kg, respectively. At the dose of 3 mg/kg, however, A-841720 significantly reduced the percentage of spontaneous alternations in a radial-maze task. In contextual-fear conditioning, A-841720, given at the dose of 10 mg/kg before acquisition, significantly reduced freezing behaviour tested 24 h later. In the same task, repeated treatment for 5 days did not reduce the impairing effect of the challenge dose, indicating a lack of tolerance development. In a passive-avoidance task, A-841720 at 10 mg/kg administered before acquisition, significantly reduced the latency to enter the dark box on the retention test. Given that complete Freund's adjuvant is a better measure of analgesia, these results indicate that the selective mGluR1 antagonist A-841720 has analgesic potential in a dose range at which it also produces memory impairments. This diminishes its therapeutic potential for the treatment of chronic pain.

Blockade of mGluR1 receptor results in analgesia and disruption of motor and cognitive performances: effects of A-841720, a novel non-competitive mGluR1 receptor antagonist.[Pubmed:17016515]

Br J Pharmacol. 2006 Nov;149(6):761-74.

BACKGROUND AND PURPOSE: To further assess the clinical potential of the blockade of metabotropic glutamate receptors (mGluR1) for the treatment of pain. EXPERIMENTAL APPROACH: We characterized the effects of A-841720, a novel, potent and non-competitive mGluR1 antagonist in models of pain and of motor and cognitive function. KEY RESULTS: At recombinant human and native rat mGluR1 receptors, A-841720 inhibited agonist-induced calcium mobilization, with IC50 values of 10.7+/-3.9 and 1.0 +/- 0.2 nM, respectively, while showing selectivity over other mGluR receptors, in addition to other neurotransmitter receptors, ion channels, and transporters. Intraperitoneal injection of A-841720 potently reduced complete Freund's adjuvant-induced inflammatory pain (ED50 = 23 micromol kg(-1)) and monoiodoacetate-induced joint pain (ED50 = 43 micromol kg(-1)). A-841720 also decreased mechanical allodynia observed in both the sciatic nerve chronic constriction injury and L5-L6 spinal nerve ligation (SNL) models of neuropathic pain (ED50 = 28 and 27 micromol kg(-1), respectively). Electrophysiological studies demonstrated that systemic administration of A-841720 in SNL animals significantly reduced evoked firing in spinal wide dynamic range neurons. Significant motor side effects were observed at analgesic doses and A-841720 also impaired cognitive function in the Y-maze and the Water Maze tests. CONCLUSIONS AND IMPLICATIONS: The analgesic effects of a selective mGluR1 receptor antagonist are associated with motor and cognitive side effects. The lack of separation between efficacy and side effects in pre-clinical models indicates that mGluR1 antagonism may not provide an adequate therapeutic window for the development of such antagonists as novel analgesic agents in humans.

Structure-activity relationship of triazafluorenone derivatives as potent and selective mGluR1 antagonists.[Pubmed:16279797]

J Med Chem. 2005 Nov 17;48(23):7374-88.

SAR (structure-activity relationship) studies of triazafluorenone derivatives as potent mGluR1 antagonists are described. The triazafluorenone derivatives are non-amino acid derivatives and noncompetitive mGluR1 antagonists that bind at a putative allosteric recognition site located within the seven-transmembrane domain of the receptor. These triazafluorenone derivatives are potent, selective, and systemically active mGluR1 antagonists. Compound 1n, for example, was a very potent mGluR1 antagonist (IC50 = 3 nM) and demonstrated full efficacy in various in vivo animal pain models.