title: Automated blood sampling to identify pharmacodynamics biomarkers of corticotrophin releasing factor receptor 1 antagonism.
abstract: BACKGROUND
  The aim of this study was to use an automated blood sampling technique to measure soluble hormones following an ovine corticotrophin releasing factor (oCRF) challenge using pharmacological doses that significantly inhibit brain CRF(1) receptors.
  
  
  METHODS
  A high throughput crude homogenate CRF(1) receptor binding assay was used to measure binding affinity, dose and time occupancy and exposure relationships in rat brain. From these studies a 30 mg/kg dose of DMP904 was selected to test in an oCRF challenged hormone release assay using an automated blood sampler.
  
  
  RESULTS
  DMP904 dose-dependently displaced [(125)I]oCRF ex vivo binding in crude rat cortex homogenates with a mean ID(50) of 0.4±0.08 mg/kg (n=4). DMP904 receptor occupancy remained greater than 90% over a 24h time period, despite a decrease in free plasma concentration. A dose of 30 mg/kg completely abolished an oCRF stimulated increase in plasma corticosterone and adrenocorticotropic hormone (ACTH), as measured by an automated blood sampler. There were no significant alterations to either basal or stimulated pituitary derived hormones measured.
  
  
  CONCLUSIONS
  In conclusion, we have shown for the first time, an automated blood sampling technique that can be incorporated to identify pharmacodynamic biomarkers in-vivo. This technology can be used successfully to reduce the number of animals and improve the quality of biomarker measures. Furthermore, at least for DMP904, to elicit a marked inhibition on plasma corticosterone levels, doses that produce greater than 95% brain occupancy are required.
authors: Pfizer Ltd, Sandwich, CT13 9NJ, UK. sidathkatu@hotmail.com
authors: S D
authors: SD
authors: Katugampola
authors: R
authors: R
authors: Fish
authors: C
authors: C
authors: Wood
authors: K
authors: K
authors: Young
authors: C
authors: C
authors: Da Costa Mathews
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001331:Automation; D054316:Biomarkers, Pharmacological / Q000378:metabolism; D001800:Blood Specimen Collection / Q000379:methods*; D001921:Brain / Q000378:metabolism; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage* / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008297:Male; D011485:Protein Binding; D011720:Pyrazoles / Q000008:administration & dosage / Q000494:pharmacology*; D011743:Pyrimidines / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018019:Receptors, Corticotropin-Releasing Hormone / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012756:Sheep; D013997:Time Factors; D000099052:CRF Receptor, Type 1
chemical_list: C417190:4-(3-pentylamino)-2,7-dimethyl-8-(2-methyl-4-methoxyphenyl)pyrazolo(1,5-a)pyrimidine; D054316:Biomarkers, Pharmacological; D011720:Pyrazoles; D011743:Pyrimidines; D018019:Receptors, Corticotropin-Releasing Hormone; D000099052:CRF Receptor, Type 1; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone