KPR-5714, a selective transient receptor potential melastatin 8 antagonist, improves voiding dysfunction in rats with bladder overactivity but does not affect voiding behavior in normal rats.

AIMS: Transient receptor potential melastatin 8 (TRPM8) has a role in the abnormal sensory transduction of the bladder and is involved in the pathophysiology of hyperactivity bladder disorders. The aim of this study is to examine the effects of KPR-5714, a novel and selective TRPM8 antagonist, on voiding dysfunction induced by bladder afferent hyperactivity via mechanosensitive C-fibers in rats. METHODS: The effects of intragastric administration of KPR-5714 on bladder overactivity induced by intravesical instillation of 10 mM ATP were investigated using cystometry in conscious female rats. We examined the effects of oral administration of KPR-5714 on voiding behavior using a metabolic cage in normal male rats and rats with an intratesticular injection of 3% acetic acid. RESULTS: In cystometry measurements, the intercontraction interval was decreased by intravesical ATP instillation. KPR-5714 (0.1, 0.3, and 1 mg/kg) dose-dependently prolonged the shortened intercontraction interval provoked by ATP. In voiding behavior measurements, intratesticular injection of acetic acid decreased the mean voided volume and increased voiding frequency. KPR-5714 (0.1 and 0.3 mg/kg) dose-dependently increased the mean voided volume and decreased voiding frequency without affecting the total voided volume in these rats. However, KPR-5714 (1 and 10 mg/kg) did not influence the voiding behavior in normal rats. CONCLUSION: The present results suggest that KPR-5714 improves voiding dysfunction by inhibiting the enhanced activity of mechanosensitive bladder C-fibers in rats with bladder overactivity and shows no significant change in voiding behavior in normal rats.

Identification of N-acyl-N-indanyl-α-phenylglycinamides as selective TRPM8 antagonists designed to mitigate the risk of adverse effects.

Transient receptor potential melastatin 8 (TRPM8), a temperature-sensitive ion channel responsible for detecting cold, is an attractive molecular target for the treatment of pain and other disorders. We have previously discovered a selective TRPM8 antagonist, KPR-2579, which inhibited bladder afferent hyperactivity induced by acetic acid instillation into the bladder. However, additional studies have revealed potential adverse effects with KPR-2579, such as the formation of a reactive metabolite, CYP3A4 induction, and convulsions. In this report, we describe the optimization of α-phenylglycinamide derivatives to mitigate the risk of these adverse effects. The optimal compound 13x exhibited potent inhibition against icilin-induced wet-dog shakes and cold-induced frequent voiding in rats, with a wide safety margin against the potential side effects.

KPR-5714, a Novel Transient Receptor Potential Melastatin 8 Antagonist, Improves Overactive Bladder via Inhibition of Bladder Afferent Hyperactivity in Rats.

Transient receptor potential (TRP) melastatin 8 (TRPM8) is a temperature-sensing ion channel mainly expressed in primary sensory neurons (Aδ-fibers and C-fibers in the dorsal root ganglion). In this report, we characterized KPR-5714 (N-[(R)-3,3-difluoro-4-hydroxy-1-(2H-1,2,3-triazol-2-yl)butan-2-yl]-3-fluoro-2-[5-(4-fluorophenyl)-1H-pyrazol-3-yl]benzamide), a novel and selective TRPM8 antagonist, to assess its therapeutic potential against frequent urination in rat models with overactive bladder (OAB). In calcium influx assays with HEK293T cells transiently expressing various TRP channels, KPR-5714 showed a potent TRPM8 antagonistic effect and high selectivity against other TRP channels. Intravenously administered KPR-5714 inhibited the hyperactivity of mechanosensitive C-fibers of bladder afferents and dose-dependently increased the intercontraction interval shortened by intravesical instillation of acetic acid in anesthetized rats. Furthermore, we examined the effects of KPR-5714 on voiding behavior in conscious rats with cerebral infarction and in those exposed to cold in metabolic cage experiments. Cerebral infarction and cold exposure induced a significant decrease in the mean voided volume and increase in voiding frequency in rats. Orally administered KPR-5714 dose-dependently increased the mean voided volume and decreased voiding frequency without affecting total voided volume in these models. This study demonstrates that KPR-5714 improves OAB in three different models by inhibiting exaggerated activity of mechanosensitive bladder C-fibers and suggests that KPR-5714 may provide a new and useful approach to the treatment of OAB. SIGNIFICANCE STATEMENT: TRPM8 is involved in bladder sensory transduction and plays a role in the abnormal activation in hypersensitive bladder disorders. KPR-5714, as a novel and selective TRPM8 antagonist, may provide a useful treatment for the disorders related to the hyperactivity of bladder afferent nerves, particularly in overactive bladder.

KPR-2579, a novel TRPM8 antagonist, inhibits acetic acid-induced bladder afferent hyperactivity in rats.

AIMS: Transient receptor potential melastatin 8 (TRPM8) is proposed to be a promising therapeutic target for hypersensitive bladder disorders. We examined the effects of KPR-2579, a novel selective TRPM8 antagonist, on body temperature and on mechanosensitive bladder single-unit afferent activities (SAAs) provoked by intravesical acetic acid (AA) instillation in rats. METHODS: Female Sprague-Dawley rats were used. Effects of cumulative intravenous (i.v.) administrations of KPR-2579 (0.03-1 mg/kg) on deep body temperature were investigated (N = 18). In separate animals, effects of bolus administration of KPR-2579 (0.03 or 0.3 mg/kg, i.v.) on bladder hyperactivity induced by intravesical instillation of 0.1% AA were investigated using cystometry (N = 57) in a conscious free-moving condition or urethane-anesthetized condition, and SAA measurements (N = 41) were performed in a urethane-anesthetized condition. RESULTS: KPR-2579 at any doses tested did not affect body temperature. In cystometry measurements, a high dose (0.3 mg/kg) of KPR-2579 counteracted the shortened intercontraction interval provoked by AA instillation. In SAA measurements, 48 single afferent fibers (n = 24 in each fiber) were isolated. AA instillations significantly increased the SAAs of C fibers, but not of Aδ fibers, in the presence of KPR-2579's vehicle and a low dose (0.03 mg/kg) of KPR-2579. Pretreatment with a high dose (0.3 mg/kg) of KPR-2579 significantly inhibited the AA-induced activation of C-fiber SAAs. CONCLUSION: The present results suggest that TRPM8 channels play a role in the AA-induced pathological activation of mechanosensitive bladder C fibers in rats. KRP-2579 may be a promising drug for hypersensitive bladder disorders.

Synthesis and optimization of novel α-phenylglycinamides as selective TRPM8 antagonists.

Transient receptor potential melastatin 8 (TRPM8) is activated by innocuous cold and chemical substances, and antagonists of this channel have been considered to be effective for pain and urinary diseases. N-(3-aminopropyl)-2-{[(3-methylphenyl)methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride (AMTB), a TRPM8 antagonist, was proposed to be effective for overactive bladder and painful bladder syndrome; however, there is a potential risk of low blood pressure. We report herein the synthesis and structure-activity relationships of novel phenylglycine derivatives that led to the identification of KPR-2579 (20l), a TRPM8 selective antagonist. KPR-2579 reduced the number of icilin-induced wet-dog shakes and rhythmic bladder contraction in rats, with no negative cardiovascular effects at the effective dose.