title: A weighted method for estimation of receptor occupancy for pharmacodynamic measurements in drug development.
abstract: BACKGROUND
  Flow cytometry-based receptor occupancy (RO) assessments for pharmacodynamic (PD) response measurements along with drug pharmacokinetic (PK) measurements represent a cornerstone in mechanism based PK/PD modeling of drugs against cell surface targets. This report describes the utility of using a "Free" and a "Bound" assay in combination to derive RO estimations through a weighted calculation method.
  
  
  METHODS
  Data from a RO assay validation study in human samples was used to explore the performance of various RO data calculation methods. The calculation methods were subsequently applied to investigate the best method to generate RO data in a first in human phase 1 clinical trial. Finally, the outcome of the analysis was used for PK/PD modeling of a prospective phase 2a trial.
  
  
  RESULTS
  The validation data assessment demonstrated that a weighted RO calculation method had a better performance in terms of precision, accuracy and dynamic range. In the phase 1 clinical trial data analysis the weighted method again demonstrated a better performance resulting in a more robust RO estimation, and subsequently also generating a more reliable PK/PD simulation for the phase 2a trial.
  
  
  CONCLUSIONS
  This report demonstrated the utility of using a combined "Free" and "Bound" RO assessment together with a weighted calculation method to better support mechanism-based PK/PD modeling activities.
authors.affiliation: Department of Development DMPK, Novo Nordisk A/S, DK-2760, Maaloev, Denmark.
authors.forename: Ola
authors.initials: O
authors.lastname: Sternebring
authors.affiliation: Department of Development DMPK, Novo Nordisk A/S, DK-2760, Maaloev, Denmark.
authors.forename: Lene
authors.initials: L
authors.lastname: Alifrangis
authors.affiliation: Department of Quantitative Clinical Pharmacology, Novo Nordisk A/S, DK-2860, Soeborg, Denmark.
authors.forename: Toke Folke
authors.initials: TF
authors.lastname: Christensen
authors.affiliation: Department of Pharmacodynamics, Novo Nordisk A/S, DK-2760, Maaloev, Denmark.
authors.forename: Hong
authors.initials: H
authors.lastname: Ji
authors.affiliation: Department of Development Bioanalysis, Novo Nordisk A/S, DK-2760, Maaloev, Denmark.
authors.forename: Anne Charlotte
authors.initials: AC
authors.lastname: Hegelund
authors.affiliation: Department of Pharmacodynamics, Novo Nordisk A/S, DK-2760, Maaloev, Denmark.
authors.forename: Carl-Magnus
authors.initials: CM
authors.lastname: Högerkorp
mesh_terms: D055808:Drug Discovery; D004353:Drug Evaluation, Preclinical / Q000379:methods*; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D010599:Pharmacokinetics
keywords: biomarker; clinical trial; drug development; flow cytometry; pharmacodynamics; receptor occupancy