Action of MK-7264 (gefapixant) at human P2X3 and P2X2/3 receptors and in vivo efficacy in models of sensitisation.
Br J Pharmacol
; 176(13): 2279-2291, 2019 07.
Article
in En
| MEDLINE
| ID: mdl-30927255
ABSTRACT
BACKGROUND AND PURPOSE:
The P2X3 receptor is an ATP-gated ion channel expressed by sensory afferent neurons and is used as a target to treat chronic sensitisation conditions. The first-in-class, selective P2X3 and P2X2/3 receptor antagonist, the diaminopyrimidine MK-7264 (gefapixant), has progressed to Phase III trials for refractory or unexplained chronic cough. We used patch clamp to elucidate the pharmacology and kinetics of MK-7264 and rat models of hypersensitivity and hyperalgesia to test its efficacy on these conditions. EXPERIMENTALAPPROACH:
Whole-cell patch clamp of 1321N1 cells expressing human P2X3 and P2X2/3 receptors was used to determine mode of MK-7264 action, potency, and kinetics. The analgesic efficacy was assessed using paw withdrawal threshold and limb weight distribution in rat models of inflammatory, osteoarthritic, and neuropathic sensitisation. KEYRESULTS:
MK-7264 is a reversible allosteric antagonist at human P2X3 and P2X2/3 receptors. Experiments with the slowly desensitising P2X2/3 heteromer revealed concentration- and state-dependency to wash-on, with faster rates and greater inhibition when applied before agonist compared to during agonist application. The wash-on rate (τ value) for MK-7264 at maximal concentrations was much lower when applied before compared to during agonist application. In vivo, MK-7264 displayed efficacy comparable to naproxen in inflammatory and osteoarthritic sensitisation models and gabapentin in neuropathic sensitisation models, increasing paw withdrawal threshold and decreasing weight-bearing discomfort. CONCLUSIONS AND IMPLICATIONS MK-7264 is a reversible and selective P2X3 and P2X2/3 antagonist, exerting allosteric antagonism via preferential activity at closed channels. Its efficacy in rat models supports its clinical investigation for chronic sensitisation conditions.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Osteoarthritis
/
Carbolines
/
Receptors, Purinergic P2X2
/
Receptors, Purinergic P2X3
/
Purinergic P2X Receptor Antagonists
/
Hyperalgesia
/
Neuralgia
Limits:
Animals
/
Female
/
Humans
Language:
En
Journal:
Br J Pharmacol
Year:
2019
Document type:
Article
Affiliation country: