title: Intracellular accumulation of atazanavir/ritonavir according to plasma concentrations and OATP1B1, ABCB1 and PXR genetic polymorphisms.
abstract: OBJECTIVE
  The rate of accumulation of atazanavir and ritonavir within cells is still debated due to methodological limitations. Our aim was to measure peripheral blood mononuclear cell (PBMC) concentrations of atazanavir and ritonavir and investigate whether single-nucleotide polymorphisms of OATP, ABCB1, CYP3A4 and PXR genes are involved in intracellular drug penetration.
  
  
  METHODS
  HIV-positive patients administered 300 mg of atazanavir/100 mg of ritonavir were enrolled. Blood sampling was performed at the end of the dosing interval (Ctrough). PBMC-associated and plasma atazanavir and ritonavir concentrations were measured by validated HPLC coupled with a single mass detector (HPLC-MS) and HPLC-photodiode array (PDA) methods, respectively. Cell count and mean cellular volume were determined using a Coulter counter. Genotyping was conducted using real-time PCR.
  
  
  RESULTS
  Thirty-five patients were enrolled. Median atazanavir and ritonavir intracellular concentrations were 1844 and 716 ng/mL, respectively. Median plasma concentrations were 645 ng/mL for atazanavir and 75 ng/mL for ritonavir, while median intracellular/plasma concentration ratios were 2.4 and 9.2, respectively. Median ritonavir intracellular concentrations were higher for OATP1B1 521 T→C TC or CC carriers and for PXR 44477 A→G AG or GG carriers. Atazanavir intracellular/plasma concentration ratios were higher in patients GG for the ABCB1 2677 G→T single-nucleotide polymorphism (SNP) compared with GT and TT groups.
  
  
  CONCLUSIONS
  Our study showed a higher intracellular ritonavir accumulation than previously reported. Ritonavir intracellular concentrations were associated with OATP1B1 521 and PXR 44477 SNPs while intracellular atazanavir exposure was associated with the ABCB1 2677 SNP. Further clinical studies are necessary in order to confirm these data.
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy antonio.davolio@unito.it.
authors.forename: Antonio
authors.initials: A
authors.lastname: D'Avolio
authors.affiliation: Pharmacy Department, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Carcieri
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Jessica
authors.initials: J
authors.lastname: Cusato
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Simiele
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Calcagno
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Sarah
authors.initials: S
authors.lastname: Allegra
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Sciandra
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Trentini
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Perri
authors.affiliation: Unit of Infectious Diseases, University of Turin, Department of Medical Sciences, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Bonora
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D000328:Adult; D000069446:Atazanavir Sulfate; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D027381:Liver-Specific Organic Anion Transporter 1; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides / Q000097:blood*; D027361:Organic Anion Transporters / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D000077297:Pregnane X Receptor; D011725:Pyridines / Q000097:blood*; D011987:Receptors, Steroid / Q000235:genetics*; D019438:Ritonavir / Q000097:blood*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D015415:Biomarkers; D027381:Liver-Specific Organic Anion Transporter 1; D009842:Oligopeptides; D027361:Organic Anion Transporters; D000077297:Pregnane X Receptor; D011725:Pyridines; D011987:Receptors, Steroid; C503999:SLCO1B1 protein, human; D000069446:Atazanavir Sulfate; D019438:Ritonavir
keywords: HIV antiviral therapy; intracellular concentrations; pharmacogenetics; pharmacokinetics; protease inhibitors; therapeutic drug monitoring