PT  - JOURNAL ARTICLE
AU  - Narender R. Gavva
AU  - Anthony W. Bannon
AU  - David N. Hovland, Jr.
AU  - Sonya G. Lehto
AU  - Lana Klionsky
AU  - Sekhar Surapaneni
AU  - David C. Immke
AU  - Charles Henley
AU  - Leyla Arik
AU  - Annette Bak
AU  - James Davis
AU  - Nadia Ernst
AU  - Gal Hever
AU  - Rongzhen Kuang
AU  - Licheng Shi
AU  - Rami Tamir
AU  - Jue Wang
AU  - Weiya Wang
AU  - Gary Zajic
AU  - Dawn Zhu
AU  - Mark H. Norman
AU  - Jean-Claude Louis
AU  - Ella Magal
AU  - James J. S. Treanor
TI  - Repeated Administration of Vanilloid Receptor TRPV1 Antagonists Attenuates Hyperthermia Elicited by TRPV1 Blockade
AID  - 10.1124/jpet.107.125674
DP  - 2007 Oct 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 128--137
VI  - 323
IP  - 1
4099  - http://jpet.aspetjournals.org/content/323/1/128.short
4100  - http://jpet.aspetjournals.org/content/323/1/128.full
SO  - J Pharmacol Exp Ther2007 Oct 01; 323
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