RT Journal Article
SR Electronic
T1 Variability in P-Glycoprotein Inhibitory Potency (IC<sub>50</sub>) Using Various in Vitro Experimental Systems: Implications for Universal Digoxin Drug-Drug Interaction Risk Assessment Decision Criteria
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1347
OP 1366
DO 10.1124/dmd.112.050500
VO 41
IS 7
A1 Joe Bentz
A1 Michael P. O’Connor
A1 Dallas Bednarczyk
A1 JoAnn Coleman
A1 Caroline Lee
A1 Johan Palm
A1 Y. Anne Pak
A1 Elke S. Perloff
A1 Eric Reyner
A1 Praveen Balimane
A1 Marie Brännström
A1 Xiaoyan Chu
A1 Christoph Funk
A1 Ailan Guo
A1 Imad Hanna
A1 Krisztina Herédi-Szabó
A1 Kate Hillgren
A1 Libin Li
A1 Evelyn Hollnack-Pusch
A1 Masoud Jamei
A1 Xuena Lin
A1 Andrew K. Mason
A1 Sibylle Neuhoff
A1 Aarti Patel
A1 Lalitha Podila
A1 Emile Plise
A1 Ganesh Rajaraman
A1 Laurent Salphati
A1 Eric Sands
A1 Mitchell E. Taub
A1 Jan-Shiang Taur
A1 Dietmar Weitz
A1 Heleen M. Wortelboer
A1 Cindy Q. Xia
A1 Guangqing Xiao
A1 Jocelyn Yabut
A1 Tetsuo Yamagata
A1 Lei Zhang
A1 Harma Ellens
YR 2013
UL http://dmd.aspetjournals.org/content/41/7/1347.abstract
AB A P-glycoprotein (P-gp) IC50 working group was established with 23 participating pharmaceutical and contract research laboratories and one academic institution to assess interlaboratory variability in P-gp IC50 determinations. Each laboratory followed its in-house protocol to determine in vitro IC50 values for 16 inhibitors using four different test systems: human colon adenocarcinoma cells (Caco-2; eleven laboratories), Madin-Darby canine kidney cells transfected with MDR1 cDNA (MDCKII-MDR1; six laboratories), and Lilly Laboratories Cells—Porcine Kidney Nr. 1 cells transfected with MDR1 cDNA (LLC-PK1-MDR1; four laboratories), and membrane vesicles containing human P-glycoprotein (P-gp; five laboratories). For cell models, various equations to calculate remaining transport activity (e.g., efflux ratio, unidirectional flux, net-secretory-flux) were also evaluated. The difference in IC50 values for each of the inhibitors across all test systems and equations ranged from a minimum of 20- and 24-fold between lowest and highest IC50 values for sertraline and isradipine, to a maximum of 407- and 796-fold for telmisartan and verapamil, respectively. For telmisartan and verapamil, variability was greatly influenced by data from one laboratory in each case. Excluding these two data sets brings the range in IC50 values for telmisartan and verapamil down to 69- and 159-fold. The efflux ratio-based equation generally resulted in severalfold lower IC50 values compared with unidirectional or net-secretory-flux equations. Statistical analysis indicated that variability in IC50 values was mainly due to interlaboratory variability, rather than an implicit systematic difference between test systems. Potential reasons for variability are discussed and the simplest, most robust experimental design for P-gp IC50 determination proposed. The impact of these findings on drug-drug interaction risk assessment is discussed in the companion article (Ellens et al., 2013) and recommendations are provided.