title: Development of a Pharmacokinetic Model to Describe the Complex Pharmacokinetics of Pazopanib in Cancer Patients.
abstract: Pazopanib is a multi-targeted anticancer tyrosine kinase inhibitor. This study was conducted to develop a population pharmacokinetic (popPK) model describing the complex pharmacokinetics of pazopanib in cancer patients.
  
  
  
  Pharmacokinetic data were available from 96 patients from three clinical studies. A multi-compartment model including (i) a complex absorption profile, (ii) the potential non-linear dose-concentration relationship and (iii) the potential long-term decrease in exposure was developed.
  
  
  
  A two-compartment model best described pazopanib pharmacokinetics. The absorption phase was modelled by two first-order processes: 36 % (relative standard error [RSE] 34 %) of the administered dose was absorbed with a relatively fast rate (0.4 h-1[RSE 31 %]); after a lag time of 1.0 h (RSE 6 %), the remaining dose was absorbed at a slower rate (0.1 h-1[RSE 28 %]). The relative bioavailability (rF) at a dose of 200 mg was fixed to 1. With an increasing dose, the rF was strongly reduced, which was modelled with an Emax(maximum effect) model (Emaxwas fixed to 1, the dose at half of maximum effect was estimated as 480 mg [RSE 23 %]). Interestingly, the plasma exposure to pazopanib also decreased over time, modelled on rF with a maximum magnitude of 50 % (RSE 27 %) and a first-order decay constant of 0.15 day-1(RSE 43 %). The inter-patient and intra-patient variability on rF were estimated as 36 % (RSE 16 %) and 75 % (RSE 22 %), respectively.
  
  
  
  A popPK model for pazopanib was developed that illustrated the complex absorption process, the non-linear dose-concentration relationship, the high inter-patient and intra-patient variability, and the first-order decay of pazopanib concentration over time. The developed popPK model can be used in clinical practice to screen covariates and guide therapeutic drug monitoring.
authors.affiliation: Department of Pharmacy and Pharmacology, Netherlands Cancer Institute-Antoni van Leeuwenhoek and MC Slotervaart, Louwesweg 6, PO Box 90440, 1006 BK, Amsterdam, The Netherlands. h.yu@nki.nl.
authors.forename: Huixin
authors.identifier: 0000-0001-9752-0966
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Clinical Pharmacy, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Nielka
authors.initials: N
authors.lastname: van Erp
authors.affiliation: Department of Medical Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
authors.forename: Sander
authors.initials: S
authors.lastname: Bins
authors.affiliation: Department of Medical Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
authors.forename: Ron H J
authors.initials: RH
authors.lastname: Mathijssen
authors.affiliation: Department of Medical Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek, Amsterdam, The Netherlands.|Department of Clinical Pharmacology, Netherlands Cancer Institute-Antoni van Leeuwenhoek, Amsterdam, The Netherlands.|Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Jan H M
authors.initials: JH
authors.lastname: Schellens
authors.affiliation: Department of Pharmacy and Pharmacology, Netherlands Cancer Institute-Antoni van Leeuwenhoek and MC Slotervaart, Louwesweg 6, PO Box 90440, 1006 BK, Amsterdam, The Netherlands.|Department of Clinical Pharmacology, Netherlands Cancer Institute-Antoni van Leeuwenhoek, Amsterdam, The Netherlands.|Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Jos H
authors.initials: JH
authors.lastname: Beijnen
authors.affiliation: Department of Medical Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek, Amsterdam, The Netherlands.|Department of Clinical Pharmacology, Netherlands Cancer Institute-Antoni van Leeuwenhoek, Amsterdam, The Netherlands.
authors.forename: Neeltje
authors.initials: N
authors.lastname: Steeghs
authors.affiliation: Department of Pharmacy and Pharmacology, Netherlands Cancer Institute-Antoni van Leeuwenhoek and MC Slotervaart, Louwesweg 6, PO Box 90440, 1006 BK, Amsterdam, The Netherlands.|Department of Clinical Pharmacology, Netherlands Cancer Institute-Antoni van Leeuwenhoek, Amsterdam, The Netherlands.
authors.forename: Alwin D R
authors.initials: AD
authors.lastname: Huitema
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007191:Indazoles; D008954:Models, Biological; D009369:Neoplasms / Q000097:blood* / Q000188:drug therapy*; D047428:Protein Kinase Inhibitors / Q000493:pharmacokinetics / Q000627:therapeutic use; D011743:Pyrimidines / Q000493:pharmacokinetics* / Q000627:therapeutic use; D013449:Sulfonamides / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D007191:Indazoles; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D013449:Sulfonamides; C516667:pazopanib