title: Analysis of the pharmacokinetic/pharmacodynamic relationship of a small molecule CXCR3 antagonist, NBI-74330, using a murine CXCR3 internalization assay.
abstract: OBJECTIVE
  Pharmacokinetic/pharmacodynamic (PK/PD) models are necessary to relate the degree of drug exposure in vivo to target blockade and pharmacological efficacy. This manuscript describes a murine agonist-induced CXCR3 receptor internalization assay and demonstrates its utility for PK/PD analyses.
  
  
  METHODS
  Activated murine DO11.10 cells were incubated with agonist in the presence or absence of a CXCR3 antagonist and changes in surface CXCR3 expression were detected by flow cytometry. For PK/PD analysis, mice were dosed with a small molecule CXCR3 antagonist, NBI-74330, (100 mg kg(-1)) orally or subcutaneously and plasma samples taken at specified timepoints for the CXCR3 internalization assay.
  
  
  RESULTS
  Surface CXCR3 expression was specifically decreased in response to CXCL9, CXCL10 and CXCL11. CXCL11 was the most potent CXCR3 agonist in buffer (pA50=9.23+/-0.26) and the pA50 for CXCL11 was unaltered in murine plasma (pA50=9.17+/-0.15). The affinity of a small molecule CXCR3 antagonist, NBI-74330, was obtained in the absence or presence of plasma (buffer pA2 value: 7.84+/-0.14; plasma pKB) value 6.36+/-0.01). Administration of NBI-74330 to mice resulted in the formation of an N-oxide metabolite, also an antagonist of CXCR3. Both antagonists were detectable up to 7 h post oral dose and 24 h post subcutaneous dose. Measurement of CXCR3 internalization demonstrated significant antagonism of this response ex vivo, 24 h following subcutaneous administration of NBI-74330.
  
  
  CONCLUSIONS
  The CXCR3 receptor internalization assay provides a robust method for determining agonist potency orders, antagonist affinity estimates and PK/PD analyses, which discriminate between dosing regimens for the CXCR3 antagonist NBI-74330.
authors.affiliation: Department of Pharmacology, UCB Inflammation Discovery, Granta Park, Great Abington, Cambridgeshire, UK. louise.jopling@ucb-group.com
authors.forename: L A
authors.initials: LA
authors.lastname: Jopling
authors.forename: G F
authors.initials: GF
authors.lastname: Watt
authors.forename: S
authors.initials: S
authors.lastname: Fisher
authors.forename: H
authors.initials: H
authors.lastname: Birch
authors.forename: S
authors.initials: S
authors.lastname: Coggon
authors.forename: M I
authors.initials: MI
authors.lastname: Christie
mesh_terms: D000081:Acetamides / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D000284:Administration, Oral; D000818:Animals; D054357:Chemokine CXCL10 / Q000494:pharmacology; D054371:Chemokine CXCL11 / Q000494:pharmacology; D054370:Chemokine CXCL9 / Q000494:pharmacology; D016503:Drug Delivery Systems; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000187:drug effects*; D007279:Injections, Subcutaneous; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D011743:Pyrimidines / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D054367:Receptors, CXCR3 / Q000819:agonists / Q000037:antagonists & inhibitors*; D013997:Time Factors
chemical_list: D000081:Acetamides; D054357:Chemokine CXCL10; D054371:Chemokine CXCL11; D054370:Chemokine CXCL9; C501976:NBI-74330; D011743:Pyrimidines; D054367:Receptors, CXCR3