title: Intracellular CD3+ T Lymphocyte Teriflunomide Concentration Is Poorly Correlated with and Has Greater Variability Than Unbound Plasma Teriflunomide Concentration.
abstract: Leflunomide's active metabolite teriflunomide inhibits dihydro-oroate dehydrogenase, an enzyme essential to proliferation of T lymphocytes. As teriflunomide must reach the target site to have this effect, this study assessed the distribution of teriflunomide into T lymphocytes, as intracellular concentrations may be a superior response biomarker to plasma concentrations. CD3 MicroBeads (Miltenyi Biotec, Bergisch Gladbach, Germany) were used to extract CD3+T cells from the peripheral blood of patients with rheumatoid arthritis who were taking a stable dose of leflunomide. Unbound plasma and intra-CD3+T cell teriflunomide concentrations were quantified using liquid chromatography-mass spectrometry. Concentration (log transformed) and partition differences were assessed through paired Student t tests. Sixteen patients provided plasma steady-state teriflunomide samples, and eight provided a sample 6-12 weeks later. At time-point one, the geometric mean teriflunomide concentration (range) in CD3+T cells was 18.12 μg/L (6.15-42.26 μg/L) compared with 69.75 μg/L (32.89-263.1 μg/L) unbound in plasma (P < 0.001). The mean partition coefficient (range) for unbound plasma teriflunomide into CD3+T cells was 0.295 (0.092-0.632), which was significantly different from unity (P < 0.001). The median (range) change in teriflunomide concentration between the two time points was 14% (-10% to 40%) in unbound plasma and -29% (-69 to 138%) for CD3+T cells. Because teriflunomide concentrations in CD3+T cells were lower and displayed a higher intraindividual variability than the unbound plasma concentrations, its applicability as a therapeutic drug-monitoring marker may be limited.
authors.affiliation: University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.) ashley.hopkins@mymail.unisa.edu.au.
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Hopkins
authors.affiliation: University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.).
authors.forename: Mahin
authors.initials: M
authors.lastname: Moghaddami
authors.affiliation: University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.).
authors.forename: David J R
authors.initials: DJ
authors.lastname: Foster
authors.affiliation: University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.).
authors.forename: Susanna M
authors.initials: SM
authors.lastname: Proudman
authors.affiliation: University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.).
authors.forename: Richard N
authors.initials: RN
authors.lastname: Upton
authors.affiliation: University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.).
authors.forename: Michael D
authors.initials: MD
authors.lastname: Wiese
mesh_terms: D000368:Aged; D018501:Antirheumatic Agents / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology*; D002853:Chromatography, Liquid; D003437:Crotonates / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006885:Hydroxybutyrates; D008297:Male; D008875:Middle Aged; D009570:Nitriles; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D014052:Toluidines / Q000097:blood*
chemical_list: D018501:Antirheumatic Agents; D017252:CD3 Complex; D003437:Crotonates; D006885:Hydroxybutyrates; D009570:Nitriles; D014052:Toluidines; C527525:teriflunomide