4 research outputs found
Role of Hepatic Organic Anion Transporter 2 in the Pharmacokinetics of <i>R</i>- and <i>S</i>āWarfarin: In Vitro Studies and Mechanistic Evaluation
Interindividual
variability in warfarin dose requirement demands personalized medicine
approaches to balance its therapeutic benefits (anticoagulation) and
bleeding risk. Cytochrome P450 2C9 (<i>CYP2C9</i>) genotype-guided
warfarin dosing is recommended in the clinic, given the more potent <i>S</i>-warfarin is primarily metabolized by CYP2C9. However,
only about 20ā30% of interpatient variability in <i>S</i>-warfarin clearance is associated with <i>CYP2C9</i> genotype.
We evaluated the role of hepatic uptake in the clearance of <i>R</i>- and <i>S</i>-warfarin. Using stably transfected
HEK293 cells, both enantiomers were found to be substrates of organic
anion transporter (OAT)Ā2 with a MichaelisāMenten constant (<i>K</i><sub>m</sub>) of ā¼7ā12 Ī¼M but did not
show substrate affinity for other major hepatic uptake transporters.
Uptake of both enantiomers by primary human hepatocytes was saturable
(<i>K</i><sub>m</sub> ā 7ā10 Ī¼M) and
inhibitable by OAT2 inhibitors (e.g., ketoprofen) but not by OATP1B1/1B3
inhibitors (e.g., cyclosporine). To further evaluate the potential
role of hepatic uptake in <i>R</i>- and <i>S</i>-warfarin pharmacokinetics, mechanistic modeling and simulations
were conducted. A ābottom-upā PBPK model, developed
assuming that OAT2āCYPs interplay, well recovered clinical
pharmacokinetics, drugādrug interactions, and <i>CYP2C9</i> pharmacogenomics of <i>R</i>- and <i>S</i>-warfarin.
Clinical data were not available to directly verify the impact of
OAT2 modulation on warfarin pharmacokinetics; however, the bottom-up
PBPK model simulations suggested a proportional change in clearance
of both warfarin enantiomers with inhibition of OAT2 activity. These
results suggest that variable hepatic OAT2 function, in conjunction
with CYP2C, may contribute to the high population variability in warfarin
pharmacokinetics and possibly anticoagulation end points and thus
warrant further clinical investigation
<i>In vitro</i> studies with two human organic anion transporters: OAT2 and OAT7
<p>1.Penciclovir, ganciclovir, creatinine, <i>para</i>-aminohippuric acid (PAH), ketoprofen, estrone 3-O-sulfate (E3S), dehydroepiandrosterone 3-O-sulfate (DHEAS) and cyclic guanosine monophosphate (cGMP) were screened as substrates of human liver organic anion transporters OAT2 and OAT7.</p> <p>2.For OAT7, high uptake ratios (versus mock transfected HEK293 cells) of 29.6 and 15.3 were obtained with E3S and DHEAS. Less robust uptake ratios (ā¤3.6) were evident with the other substrates. OAT2 (transcript variant 1, OAT2-tv1) presented high uptake ratios of 30, 13, ā¼35, ā¼25, 8.5 and 9 with cGMP, PAH, penciclovir, ganciclovir, creatinine and E3S, respectively. No uptake was observed with DHEAS.</p> <p>3.Although not a substrate of either transporter, ketoprofen did inhibit transfected OAT2-tv1 (IC<sub>50</sub> of 17, 22, 23, 24, 35 and 586āĪ¼M; creatinine, ganciclovir, penciclovir, cGMP, E3S and prostaglandin F2Ī±, respectively) and penciclovir uptake (IC<sub>50</sub>ā=ā27āĀµM; >90% inhibition) by plated human hepatocytes (PHH).</p> <p>4.It is concluded that penciclovir and ketoprofen may serve as useful tools for the assessment of OAT2 activity in PHH. However, measurement of OAT7 activity therein will prove more challenging, as high uptake rates are evident with E3S and DHEAS only and both sulfoconjugates are known to be substrates of organic anion transporting polypeptides.</p
Optimization of Metabolic and Renal Clearance in a Series of Indole Acid Direct Activators of 5ā²-Adenosine Monophosphate-Activated Protein Kinase (AMPK)
Optimization
of the pharmacokinetic (PK) properties of a series
of activators of adenosine monophosphate-activated protein kinase
(AMPK) is described. Derivatives of the previously described 5-aryl-indole-3-carboxylic
acid clinical candidate (<b>1</b>) were examined with the goal
of reducing glucuronidation rate and minimizing renal excretion. Compounds <b>10</b> (PF-06679142) and <b>14</b> (PF-06685249) exhibited
robust activation of AMPK in rat kidneys as well as desirable oral
absorption, low plasma clearance, and negligible renal clearance in
preclinical species. A correlation of in vivo renal clearance in rats
with in vitro uptake by human and rat renal organic anion transporters
(human OAT/rat Oat) was identified. Variation of polar functional
groups was critical to mitigate active renal clearance mediated by
the Oat3 transporter. Modification of either the 6-chloroindole core
to a 4,6-difluoroindole or the 5-phenyl substituent to a substituted
5-(3-pyridyl) group provided improved metabolic stability while minimizing
propensity for active transport by OAT3
Optimization of Metabolic and Renal Clearance in a Series of Indole Acid Direct Activators of 5ā²-Adenosine Monophosphate-Activated Protein Kinase (AMPK)
Optimization
of the pharmacokinetic (PK) properties of a series
of activators of adenosine monophosphate-activated protein kinase
(AMPK) is described. Derivatives of the previously described 5-aryl-indole-3-carboxylic
acid clinical candidate (<b>1</b>) were examined with the goal
of reducing glucuronidation rate and minimizing renal excretion. Compounds <b>10</b> (PF-06679142) and <b>14</b> (PF-06685249) exhibited
robust activation of AMPK in rat kidneys as well as desirable oral
absorption, low plasma clearance, and negligible renal clearance in
preclinical species. A correlation of in vivo renal clearance in rats
with in vitro uptake by human and rat renal organic anion transporters
(human OAT/rat Oat) was identified. Variation of polar functional
groups was critical to mitigate active renal clearance mediated by
the Oat3 transporter. Modification of either the 6-chloroindole core
to a 4,6-difluoroindole or the 5-phenyl substituent to a substituted
5-(3-pyridyl) group provided improved metabolic stability while minimizing
propensity for active transport by OAT3