title: Maraviroc modelling strategy: use of early phase 1 data to support a semi-mechanistic population pharmacokinetic model.
abstract: OBJECTIVE
  To model the basic pharmacokinetic (PK) characteristics of maraviroc to construct an integrated semi-mechanistic PK model for use in later population PK analyses.
  
  
  METHODS
  Three analyses were performed utilizing intravenous, oral and radiolabel data. Firstly, a PK disposition model was developed from data from 20 healthy males who received 3, 10 or 30 mg of intravenous maraviroc. Secondly, a sigmoid E(max)vs dose model of dose-normalized non-compartmental AUC from oral dosing in 134 healthy young males and females across five phase 1 studies was constructed. This described absorption dose non-linearities and tested for the influence of food, formulation and dose frequency on model parameters. The third analysis developed a mass balance model for both absorption and disposition of maraviroc with 300 mg solution and predicted the mass balance after administration of 100 mg tablet formulation.
  
  
  RESULTS
  A four-compartment PK model best described the intravenous data and no influence of dose was found on clearance. Total clearance was 48 l h(-1) (2.2% SE). The main covariate effect in the non-compartmental analysis reproduced the dose-dependency of food through a five-fold increase in the ED(50) of the sigmoid E(max) model. The mass balance models calculated that 33.3% and 22.9% of 300 mg solution and 100 mg tablet doses, respectively, are systemically available, and first-pass metabolism extracts 62% of an absorbed dose, estimating a hepatic blood flow of 101 l h(-1).
  
  
  CONCLUSIONS
  The analysis demonstrates a novel integration approach to build a maraviroc semi-mechanistic population PK model for further use in volunteers and patients.
authors.affiliation: Pharmacometrics, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT139NJ, UK. barry.weatherley@pfizer.com
authors.forename: Barry
authors.initials: B
authors.lastname: Weatherley
authors.forename: Lynn
authors.initials: L
authors.lastname: McFadyen
mesh_terms: D000284:Administration, Oral; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D017321:Clinical Trials, Phase I as Topic; D003510:Cyclohexanes / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005260:Female; D015658:HIV Infections / Q000188:drug therapy; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D000077592:Maraviroc; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D015233:Models, Statistical; D014230:Triazoles / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D019380:Anti-HIV Agents; D003510:Cyclohexanes; D014230:Triazoles; D000077592:Maraviroc