Repeated administration of vanilloid receptor TRPV1 antagonists attenuates hyperthermia elicited by TRPV1 blockade.
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.
Gavva
Narender R
NR
Department of Neuroscience, MS-29-2-B, One Amgen Center Dr., Thousand Oaks, CA 91320-1799, USA. ngavva@amgen.com
Bannon
Anthony W
AW
Hovland
David N
DN
Lehto
Sonya G
SG
Klionsky
Lana
L
Surapaneni
Sekhar
S
Immke
David C
DC
Henley
Charles
C
Arik
Leyla
L
Bak
Annette
A
Davis
James
J
Ernst
Nadia
N
Hever
Gal
G
Kuang
Rongzhen
R
Shi
Licheng
L
Tamir
Rami
R
Wang
Jue
J
Wang
Weiya
W
Zajic
Gary
G
Zhu
Dawn
D
Norman
Mark H
MH
Louis
Jean-Claude
JC
Magal
Ella
E
Treanor
James J S
JJ
D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D052160:Benzothiazoles / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D001831:Body Temperature / Q000187:drug effects; D016466:CHO Cells; D002211:Capsaicin / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D015195:Drug Design; D005260:Female; D005334:Fever / Q000188:drug therapy* / Q000378:metabolism; D005620:Freund's Adjuvant / Q000494:pharmacology; D008252:Macaca fascicularis; D008297:Male; D015394:Molecular Structure; D010146:Pain / Q000188:drug therapy* / Q000378:metabolism; D011743:Pyrimidines / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors*; D013686:Telemetry
D018712:Analgesics, Non-Narcotic; D052160:Benzothiazoles; C523409:N-(4-(6-(4-trifluoromethylphenyl)pyrimidin-4-yloxy)benzothiazol-2-yl)acetamide; D011743:Pyrimidines; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; C519014:tert-butyl-2-(6-((2-(acetylamino)-1,3-benzothiazol-4-yl)oxy)pyrimidin-4-yl)-5-(trifluoromethyl)phenylcarbamate; D005620:Freund's Adjuvant; D002211:Capsaicin