RT Journal Article SR Electronic T1 Repeated Administration of Vanilloid Receptor TRPV1 Antagonists Attenuates Hyperthermia Elicited by TRPV1 Blockade JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 128 OP 137 DO 10.1124/jpet.107.125674 VO 323 IS 1 A1 Narender R. Gavva A1 Anthony W. Bannon A1 David N. Hovland, Jr. A1 Sonya G. Lehto A1 Lana Klionsky A1 Sekhar Surapaneni A1 David C. Immke A1 Charles Henley A1 Leyla Arik A1 Annette Bak A1 James Davis A1 Nadia Ernst A1 Gal Hever A1 Rongzhen Kuang A1 Licheng Shi A1 Rami Tamir A1 Jue Wang A1 Weiya Wang A1 Gary Zajic A1 Dawn Zhu A1 Mark H. Norman A1 Jean-Claude Louis A1 Ella Magal A1 James J. S. Treanor YR 2007 UL http://jpet.aspetjournals.org/content/323/1/128.abstract AB Capsaicin, the active ingredient in some pain-relieving creams, is an agonist of a nonselective cation channel known as the transient receptor potential vanilloid type 1 (TRPV1). The pain-relieving mechanism of capsaicin includes desensitization of the channel, suggesting that TRPV1 antagonism may be a viable pain therapy approach. In agreement with the above notion, several TRPV1 antagonists have been reported to act as antihyperalgesics. Here, we report the in vitro and in vivo characterization of a novel and selective TRPV1 antagonist, N-(4-[6-(4-trifluoromethyl-phenyl)-pyrimidin-4-yloxy]-benzothiazol-2-yl)-acetamide I (AMG 517), and compare its pharmacology with that of a closely related analog, tert-butyl-2-(6-([2-(acetylamino)-1,3-benzothiazol-4-yl]oxy)pyrimidin-4-yl)-5-(trifluoromethyl)phenylcarbamate (AMG8163). Both AMG 517 and AMG8163 potently and completely antagonized capsaicin, proton, and heat activation of TRPV1 in vitro and blocked capsaicin-induced flinch in rats in vivo. To support initial clinical investigations, AMG 517 was evaluated in a comprehensive panel of toxicology studies that included in vivo assessments in rodents, dogs, and monkeys. The toxicology studies indicated that AMG 517 was generally well tolerated; however, transient increases in body temperature (hyperthermia) were observed in all species after AMG 517 dosing. To further investigate this effect, we tested and showed that the antipyretic, acetaminophen, suppressed the hyperthermia caused by TRPV1 blockade. We also showed that repeated administration of TRPV1 antagonists attenuated the hyperthermia response, whereas the efficacy in capsaicin-induced flinch model was maintained. In conclusion, these studies suggest that the transient hyperthermia elicited by TRPV1 blockade may be manageable in the development of TRPV1 antagonists as therapeutic agents. However, the impact of TRPV1 antagonist-induced hyperthermia on their clinical utility is still unknown. The American Society for Pharmacology and Experimental Therapeutics