Preclinical Mouse Models To Study Human OATP1B1- and OATP1B3

Publication Date (Web): October 16, 2015. Copyright © 2015 American Chemical Society. *The Netherlands Cancer Institute, Division of Molecular Oncolo...
2 downloads 4 Views 1MB Size
Subscriber access provided by FLORIDA STATE UNIV

Article

Preclinical mouse models to study human OATP1B1and OATP1B3-mediated drug-drug interactions in vivo Selvi Durmus, Gloria Lozano-Mena, Anita van Esch, Els Wagenaar, Olaf van Tellingen, and Alfred H. Schinkel Mol. Pharmaceutics, Just Accepted Manuscript • DOI: 10.1021/acs.molpharmaceut.5b00453 • Publication Date (Web): 16 Oct 2015 Downloaded from http://pubs.acs.org on October 27, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Molecular Pharmaceutics is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Molecular Pharmaceutics

1

Preclinical mouse models to study human OATP1B1- and OATP1B3-mediated

2

drug-drug interactions in vivo

3

Authors: Selvi Durmus1, Gloria Lozano-Mena1, 2, Anita van Esch1, Els Wagenaar1, Olaf van Tellingen3,

4

Alfred H. Schinkel

5

1

6

2

7

of Barcelona, Barcelona, Spain

8

3

1

Division of Molecular Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands, Department of Physiology and Nutrition and Institute of Food Safety Research (INSA-UB), University

Department of Clinical Chemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands

9 10

Corresponding author:

11

Dr. Alfred H. Schinkel,

12

The Netherlands Cancer Institute,

13

Division of Molecular Oncology,

14

Plesmanlaan 121, 1066 CX

15

Amsterdam, The Netherlands,

16

E-mail: [email protected],

17

Phone: +31 20 5122046,

18

Fax: +31 20 669 1383

19 20

Running title: Human OATP1B-mediated drug-drug interactions

21

Article category: Research article

22

To be submitted to: Molecular Pharmaceutics

23

Statement of conflict of interest:

24

The research group of A.H. Schinkel receives revenue from commercial distribution of some of the

25

mouse strains used in this study. No other conflicts of interest are declared.

26 1 ACS Paragon Plus Environment

Molecular Pharmaceutics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 31

27

Abstract

28

The impact of OATP drug uptake transporters in drug-drug interactions (DDIs) is increasingly

29

recognized. OATP1B1 and OATP1B3 are human hepatic uptake transporters that can mediate liver

30

uptake of a wide variety of drugs. Recently, we generated transgenic mice with liver-specific

31

expression of human OATP1B1 or OATP1B3 in a mouse Oatp1a/1b knockout background. Here, we

32

investigated the applicability of these mice in OATP-mediated drug-drug interaction studies using the

33

prototypic OATP inhibitor rifampicin and a good OATP substrate, the anticancer drug methotrexate

34

(MTX). We next assessed the possibility of OATP-mediated interactions between telmisartan and

35

MTX, a clinically relevant drug combination. Using HEK293 cells overexpressing OATP1B1 or

36

OATP1B3, we estimated IC50 values for both rifampicin (0.9 or 0.3 µM) and telmisartan (6.7 or 7.9

37

µM) in inhibiting OATP-mediated MTX uptake in vitro. Using wild-type, Oatp1a/1b-/- and OATP1B1- or

38

OATP1B3-humanized transgenic mice, we found that rifampicin inhibits hepatic uptake of MTX

39

mediated by the mouse Oatp1a/1b and human OATP1B1 and OATP1B3 transporters at clinically

40

relevant concentrations. This highlights the applicability of these mouse models for DDI studies and

41

may be exploited in the clinic to reduce the dose and thus methotrexate-mediated toxicity. On the

42

other hand, telmisartan inhibited only human OATP1B1-mediated hepatic uptake of MTX at

43

concentrations higher than those used in the clinic; therefore risks for OATP-mediated clinical DDIs for

44

this drug combination are likely to be low. Overall, we show here that OATP1B1 and OATP1B3-

45

humanized mice can be used as in vivo tools to assess and possibly predict clinically relevant DDIs.

46 47

Keywords: drug-drug interactions, DDI, OATP1B1, OATP1B3, methotrexate, rifampicin, telmisartan,

48

hepatic uptake, plasma disposition

49 OATP;

Organic anion-transporting polypeptide, SLCO/Slco; Organic

anion-

50

Abbreviations:

51

transporting polypeptide encoding gene name, WT; wild-type, HEK; human embryonic kidney, IC50;

52

the half maximal inhibitory concentration required for inhibiting biological or biochemical function, DDI;

53

drug-drug interaction, MTX; methotrexate

54 55 56

2 ACS Paragon Plus Environment

Page 3 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Molecular Pharmaceutics

57

Introduction

58

Organic anion-transporting polypeptides (OATP/Oatp) are sodium-independent transmembrane

59

uptake transporters encoded by SLCO/Slco genes. OATPs are expressed in several organs including

60

liver, kidney and small intestine, where they mediate the tissue uptake of substrate compounds . More

61

and more studies show that OATPs are important players in disposition of a wide range of drugs

62

including statins, cardiac glycosides, antibiotics, and chemotherapeutics . Of the OATP1 family,

63

OATP1B1 and -1B3 are highly expressed in the sinusoidal membrane of hepatocytes3, where they

64

have key roles in hepatic uptake and/or plasma clearance of many structurally diverse drugs (e.g.

65

methotrexate (MTX), paclitaxel, docetaxel, pravastatin, fexofenadine and doxorubicin)4-8. Therefore,

66

alterations in OATP1B activity or drug-drug interactions (DDIs) mediated by inhibition of OATP1B

67

transporters might have important clinical consequences for the pharmacokinetics, efficacy and toxicity

68

of transported therapeutics

69

significant changes in the disposition and toxicity of pravastatin, valsartan, MTX and SN-3810, 12, 13. Full

70

deficiency of OATP1B1 and -1B3 results in the disruption of hepatic re-uptake and hence increased

71

plasma levels of conjugated bilirubin, causing a syndrome called Rotor-type hyperbilirubinemia14.

72

Our knowledge of the involvement of OATPs in DDIs is growing rapidly, and the clinical importance of

73

such interactions is becoming more and more evident15. FDA and EMA strongly recommend

74

investigation of DDIs mediated by OATP1B1 and -1B3 for new molecular entities during drug

75

development since 201216. Recently, Shitara et al.2 reported examples of DDIs that are caused by

76

inhibition of OATP1B transporters via potent inhibitors, and which affected the pharmacokinetics of

77

victim drugs. The inhibitor drugs tested were antibiotics, antiviral drugs and the immunosuppressant

78

cyclosporine A, and victim drugs were widely used statins, antidiabetic and hypertension drugs.

79

Among the inhibitors, cyclosporine A and rifampicin appeared to be particularly strong inhibitors of

80

OATP1B1, which caused increases in the plasma levels of several statins of 2.2- to 23-fold as a result

81

of DDIs2. There are only a few recent studies on OATP-mediated DDIs with anticancer drugs, although

82

these are widely used and often substrates or inhibitors of OATPs. Hu et al.

83

whether inhibition of OATP1B1 by tyrosine kinase inhibitors could explain a decreased docetaxel

84

clearance. Sorafenib was selected as a potent inhibitor of OATP1B1 based on in vitro assays, but

85

single or multiple doses of sorafenib did not affect docetaxel plasma levels in vivo using Oatp1b2

86

knockout and hOATP1B1-expressing transgenic mice . Nieuweboer et al.

1

2

2, 9-11

. For example, genetic variants of OATP1B1 are associated with

17

17

18

recently investigated

recently showed that

3 ACS Paragon Plus Environment

Molecular Pharmaceutics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 31

87

polysorbate 80 or Kolliphor (Cremophor) EL in the drug formulation can inhibit (mouse) OATP1B2-

88

mediated hepatic elimination of paclitaxel. Clearly, DDI studies involving OATP-dependent interactions

89

between widely used medicines and anticancer drugs are urgently needed, as such interactions may

90

lead to unexpected toxicities and altered efficacy in the treatment of cancers, and anticancer drugs are

91

usually administered at high dosages and have a narrow therapeutic window. The antifolate MTX is a

92

widely used anticancer and antirheumatic drug that is a good substrate of mouse Oatp1a/1b and

93

human OATP1B1 and -1B3 transporters in vivo4. The likelihood of undesired DDIs and thus altered

94

pharmacokinetics of MTX might be substantial, when prescribed with other commonly used drugs

95

such as antibiotics, hypertension drugs and antidiabetics that are inhibitors/substrates of OATPs.

96

Thus, MTX is of great interest for assessment of such interactions and prediction of clinical outcomes.

97

To predict clinical DDIs, many studies utilize in vitro cellular uptake assays and in silico11,

98

preclinical models

99

situation and use of preclinical wild-type and knockout animal models does not necessarily result in

19-22

and

2, 23

. However, it remains challenging to translate in vitro data to the human in vivo

24, 25

100

optimal prediction due to species differences

. Accordingly, we have generated humanized

101

Oatp1a/1b knockout mouse models with liver-specific expression of human OATP1B1 or -1B3, with

102

transgenic protein levels roughly comparable to those seen in pooled human liver samples

103

study, we investigated whether these mouse models could be used to assess short-term, acute human

104

OATP1B1 and -1B3-mediated DDIs in vivo. For this aim, we used the antibiotic rifampicin as a model

105

inhibitor of OATP1B transporters and MTX as a victim drug. Secondly, we tested OATP1B-mediated

106

DDIs between the antihypertensive drug telmisartan and MTX, which have a higher chance for co-

107

prescription in the clinic.

4, 13

. In this

108

4 ACS Paragon Plus Environment

Page 5 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Molecular Pharmaceutics

109

Materials and Methods

110

Chemicals

111

Methotrexate (100 mg/ml, Pharmachemie, The Netherlands) and cyclosporine A (CsA, 50 mg/ml,

112

Novartis, Switzerland) were obtained as parenteral formulations from the pharmacy department of the

113

Antonie van Leeuwenhoek Hospital (The Netherlands). Rifampicin was purchased from Sigma-Aldrich

114

(USA) and telmisartan was purchased from Sequoia Research Chemicals (UK), both in powder forms.

115

7-OH-MTX, rifampicin-d3 and telmisartan-d7 were purchased from Toronto Research Chemicals

116

(Canada). All of the chemicals used for HPLC-UV and HPLC-MS/MS analysis were from Sigma-

117

Aldrich (USA) or Merck (Germany).

118

Drug solutions

119

In vitro experiments

120

MTX stock solution (100 mg/ml = 220.1 mM) and CsA (50 mg/ml = 41.6 mM) were diluted in Krebs-

121

Henseleit buffer to yield 50 µM MTX and 0.5 µM CsA solution, respectively. Rifampicin (50 mM) and

122

telmisartan (10 mM) were prepared in DMSO and dimethylformamide (DMF), respectively, and were

123

further diluted in Krebs-Henseleit buffer to yield the desired concentrations.

124

In vivo experiments

125

MTX stock solution (100 mg/ml) was diluted 50 or 250-fold with 0.9% NaCl to yield a concentration of

126

2 or 0.4 mg/ml. Rifampicin was dissolved in DMSO (at 80 mg/ml) and further diluted in 0.9% NaCl to

127

yield a concentration of 4 mg/ml. Telmisartan was dissolved in DMF (7 mg/ml, maximum solubility) and

128

further diluted in PBS to yield a concentration of 1.4 mg/ml. All drugs were administered intravenously

129

(i.v.), using a volume of 5 µl/g body weight. All working solutions were prepared on the day of

130

experiment.

131

Cell culture

132

HEK293 cells transduced with vector control, hSLCO1B1 and hSLCO1B3 cDNAs were a kind gift from

133

Prof. Werner Siegmund and Dr. Markus Keiser (University of Greifswald, Greifswald, Germany)26. All

134

cells were grown in Dulbecco's modified Eagle's medium high glucose (Gibco) supplemented with

135

10% fetal bovine serum (Sigma), 100 U/ml penicillin, 100 µg/ml streptomycin and 0.25 µg/ml

136

amphotericin B at 37°C with 5% CO2 and 95% humidity. All of these cell lines were authenticated and

137

found to be identical to the original cell lines.

138

5 ACS Paragon Plus Environment

Molecular Pharmaceutics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 31

139

Cellular uptake experiments

140

Cellular uptake experiments were performed according to previously described methods

141

modified as required. Krebs-Henseleit buffer at pH 7.4, which was adjusted before the experiment was

142

started, was used in all the steps of the experiment including dilutions of the drug stock solutions.

143

Briefly, cells were preincubated with 1 ml of pre-warmed buffer for 15 min at 37°C. Uptake

144

experiments were started by aspirating the preincubation buffer and adding 600 µl of pre-warmed

145

buffer containing (inhibitor) drugs; MTX (50 µM) alone or together with rifampicin (0, 1, 2.5, 5, 15, 25,

146

50 or 100 µM) or telmisartan (0, 1, 2.5, 5, 25, 50, 100 or 250 µM) or CsA (0.5 µM). CsA was used as a

147

positive control for the uptake inhibition; therefore it was also added in the pre-incubation buffer as an

148

OATP inhibitor. At designated time points (2.5, 5, 10, 15, 30, 60 or 120 min) experiments were

149

terminated by removing the incubation buffer and immediately adding 1 ml of ice-cold buffer. After

150

washing twice with ice-cold buffer, cells were lysed with 150 µl of 0.2 N NaOH for a minimum of 15

151

min. 10 µl of the cell lysate was used to determine the cellular protein amount by the Bradford method

152

using bovine serum albumin as a standard. 60 µl of the cell lysates were used to determine MTX

153

levels by HPLC-UV. These were readily detectable when 50 µM MTX was applied. Percentage of

154

OATP-mediated uptake of MTX was calculated using the uptake without inhibitor as 100%.

155

Animals

156

Mice were housed and handled according to institutional guidelines complying with Dutch legislation.

157

Male WT, Oatp1a/1b-/-, Oatp1a/1b-/-;1B1tg and Oatp1a/1b-/-;1B3tg with liver-specific expression of

158

human SLCO genes, all of a >99% FVB genetic background, were used between 8 and 14 weeks of

159

age. Animals were kept in a temperature-controlled environment with a 12 hr light/12 hr dark cycle and

160

received a standard diet (AM-II, Hope Farms) and acidified water ad libitum.

161

Plasma and liver pharmacokinetic experiments

162

Dosages of MTX were 10 and 2 mg/kg body weight, that of rifampicin was 20 mg/kg and that of

163

telmisartan was 7 mg/kg body weight. Rifampicin, telmisartan or vehicles (0.9% NaCl or PBS) were

164

injected into the tail vein of mice 3 minutes before MTX administration. For all experiments, mice were

165

sacrificed at 5 or 15 min after MTX administration by terminal bleeding through cardiac puncture under

166

isoflurane anesthesia and organs were rapidly removed. Plasma was isolated from blood samples

167

after centrifugation at 2,100 g for 6 min at 4°C, livers were homogenized in 1% bovine serum albumin

168

and all the samples were stored at −30°C until analysis.

8, 27

and

6 ACS Paragon Plus Environment

Page 7 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Molecular Pharmaceutics

169

After drug analysis, results were presented as concentrations in the organs (nmol/g), % of the total

170

dose (dose corrected for the body weight of each individual mouse being equivalent to 100%) and/or

171

organ-to-plasma ratios. Organ-to-plasma ratios were calculated by dividing organ concentration

172

expressed as nmol/g by plasma concentration expressed as nmol/ml, assuming 1 ml of plasma is

173

roughly equivalent to 1 g of tissue.

174

Drug Analyses

175

Determination of MTX and 7-OH-MTX

176

Levels of MTX and 7-OH-MTX in plasma and liver homogenates were determined by HPLC-UV

177

detection as described previously28. For the in vitro experiments, cell lysates in 0.2 N NaOH were

178

pretreated with 1.5 M HClO4 in a ratio of 1:1.6 v/v. After vortexing 5 s and centrifugation at 16,873 g

179

for 5 min at 4°C, supernatants were injected into the HPLC system directly. Standard curve (4.4 - 2201

180

nM) and quality control (22.01, 220.1 and 2201 nM) samples were prepared using blank cell lysates as

181

matrix.

182

Sample pre-treatment for rifampicin and telmisartan

183

Plasma and liver homogenates were thawed at room temperature and diluted 1:50 or 1:100 (for

184

rifampicin or telmisartan determinations, respectively) in blank human plasma. A volume of 100 µl of

185

plasma or liver homogenate was pipetted into 2 ml polypropylene vials (Eppendorf, Hamburg,

186

Germany). Next, volumes of 50 µl of IS working solution (rifampicin-d3 or telmisartan-d3; 1 µg/ml in

187

acetonitrile: water 30:70; v/v) and 1000 µl of ethyl acetate were added. After automatic shaking for 15

188

min at 480 rpm, the samples were centrifuged for 1 min at 20,000 g. The aqueous layer was snap

189

frozen in dry ice/ethanol and the upper organic layer was decanted into a 1.5 ml vial (Brand,

190

Wertheim, Germany). The solvent was evaporated to dryness in Speed-Vac SC210A (Savant,

191

Farmingdale, NY, USA) and the residue was reconstituted with 100 µl of acetonitrile: water (30:70, v/v)

192

by sonicating for 5 min and vortex-mixing for 5 s. Finally, samples were centrifuged for 5 min at 20,000

193

g prior to analysis.

194

Quantification of rifampicin and telmisartan

195

The levels of rifampicin and telmisartan in plasma and liver homogenates were quantified by HPLC

196

coupled to tandem mass spectrometry (HPLC-MS/MS). Details of the instrumentation are explained in

197

supplemental text.

7 ACS Paragon Plus Environment

Molecular Pharmaceutics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 31

198

The concentrations of rifampicin and telmisartan in plasma and liver homogenates were determined by

199

means of the internal standard (I.S.) method, employing the corresponding stable isotope labeled

200

drugs (rifampicin-d3 and telmisartan-d3).

201

Stock solutions of rifampicin and telmisartan were prepared in DMSO at 10 mM and stored at ‒20ºC.

202

For each analytical run, these solutions were diluted in DMSO to obtain working solutions ranging from

203

100 nM to 100 µM for the preparation of the above-mentioned calibration standards. A set of

204

calibration standards in either blank plasma or liver homogenate was prepared using 100-fold dilution

205

of the DMSO stock in blank biological matrix. Final calibration samples contained 1, 3, 10, 30, 100,

206

300 and 1000 nM.

207

Statistical analysis

208

IC50 values for rifampicin and telmisartan for inhibition of MTX uptake were determined using non-

209

linear regression (curve fit) analysis in GraphPad Prism 6.01 software after correction for the

210

background uptake in control cells. The 2-sided Student's t-test or one-way analysis of variance

211

(ANOVA) with post-hoc tests employing Tukey's corrections were used to determine statistical

212

significance either between two or multiple groups, respectively. Results were presented as the mean

213

± standard deviation (SD). Differences were considered to be statistically significant when P ≤ 0.05.

214 215 216

8 ACS Paragon Plus Environment

Page 9 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Molecular Pharmaceutics

217

Results

218

In vitro MTX uptake by OATP1B transporters

219

To establish time-dependent uptake of MTX by OATPs, we performed cellular uptake experiments

220

with MTX (50 µM) using control and OATP1B1- or OATP1B3-expressing HEK293 cells for various

221

time periods between 2.5 and 30 min. 50 µM MTX was used since shortly after i.v. administration (5-

222

15 min) of 10 mg/kg MTX in the planned in vivo DDI studies, plasma concentrations of that order are

223

achieved (see below). MTX uptake by OATP1B1 or -1B3 was significantly greater compared to control

224

cells at all-time points (Figure 1A-B). MTX uptake by OATP1B3 was slightly saturated after 5 min and

225

more strongly after 15 min. In subsequent studies we used 15 min uptake, as a clear differential was

226

seen at this time point between both the transporter-expressing cells and their controls. The increased

227

uptake of MTX in both OATP-expressing cells was inhibited completely by 0.5 µM CsA, which is

228

known to inhibit OATPs (Figure 1C); further corroborating that MTX uptake in these cells was OATP-

229

mediated. Studies with these cells were performed to estimate the IC50 values of candidate inhibitors

230

for subsequent in vivo DDI studies.

231

Effect of rifampicin on OATP-mediated MTX uptake in vitro

232

To determine whether OATP-mediated MTX uptake could be inhibited by the OATP inhibitor

233

rifampicin, we estimated the IC50 of rifampicin for each OATP-expressing cell type. IC50

234

concentrations of rifampicin were 0.88 ± 0.18 or 0.31 ± 0.12 µM for OATP1B1- or OATP1B3-mediated

235

MTX uptake, respectively (Figure 2). This suggests that rifampicin is a fairly strong inhibitor (low µM

236

range) of MTX uptake mediated by these OATPs.

237

Effect of rifampicin on OATP-mediated MTX and 7-OH-MTX disposition in vivo

238

To investigate whether rifampicin can also inhibit OATP-mediated MTX transport in vivo, we

239

administered 20 mg/kg rifampicin or vehicle (i.v.) 3 min before 10 mg/kg MTX dosing (i.v.) to wild-type

240

(WT), Oatp1a/1b knockout and transgenic mice with liver-specific expression of OATP1B1 and

241

OATP1B3, considering their relevance to human drug disposition.

242

In groups receiving vehicle, MTX disposition results were similar to those described previously by van

243

de Steeg et al.4. Plasma MTX levels were increased in Oatp1a/1b-/-, Oatp1a/1b-/-;1B1tg and

244

Oatp1a/1b-/-;1B3tg mice compared to WT strains, both at 5 and 15 min after MTX administration

245

(Figure 3A and B). Liver levels of MTX and liver-to-plasma ratios were profoundly decreased by

246

removal of the Oatp1a/1b transporters, and expression of human OATP1B1 or -1B3 in these livers led

9 ACS Paragon Plus Environment

Molecular Pharmaceutics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 31

247

to significant, albeit not complete, rescue of the impaired liver uptake of MTX (Figure 3), suggesting

248

human OATP-mediated transport. Considering the presence of only one of each of the human OATPs

249

in the transgenic strains instead of both together as in humans, the extent of liver uptake rescue by

250

each transporter seems to be substantial. Therefore, these findings suggest that MTX hepatic uptake

251

is primarily mediated by OATPs.

252

In rifampicin pretreated groups, plasma levels of MTX were significantly increased by 4.2-, 1.5- and

253

1.9-fold in WT, Oatp1a/1b-/- and Oatp1a/1b-/-;1B3tg mice 5 min after MTX administration (Figure 3A).

254

Rifampicin pretreatment significantly increased the plasma levels of MTX in WT and Oatp1a/1b-/-

255

;1B3tg mice to similar concentrations as found in Oatp1a/1b-/- mice. This suggests that with the 20

256

mg/kg i.v. rifampicin dose, we could strongly inhibit the OATP-mediated MTX uptake. Indeed,

257

rifampicin treatment led to significant decreases in liver MTX levels in the wild-type and both

258

OATP1B1- and OATP1B3-transgenic strains, but not the Oatp1a/1b-/- mice (Figure 3C and

259

Supplementary Figure 1A), indicating that rifampicin specifically inhibits OATP-mediated uptake of

260

MTX. When corrected for plasma levels, substantial decreases were observed in liver-to-plasma ratios

261

after rifampicin treatment. Although not reaching the level of knockout mice, WT mice showed a highly

262

significant decrease by a factor of 8 in liver-to-plasma ratios of MTX (P < 0.001, Figure 3E),

263

suggesting a very strong inhibition of Oatp1a/1b-mediated hepatic uptake of MTX in this strain. Liver-

264

to-plasma ratios of MTX in Oatp1a/1b-/-;1B1tg and Oatp1a/1b-/-;1B3tg mice were also decreased by a

265

factor of 3.5 and 11.4, respectively, and more or less back to the levels in knockout mice (Figure 3E).

266

Furthermore, Oatp1a/1b-/- mice did not show any significant difference in liver-to-plasma ratios of MTX

267

upon rifampicin treatment, indicating that the hepatic uptake of MTX that was inhibited by rifampicin

268

was OATP-specific.

269

To assess whether the rifampicin effect also applied at a later time point, we tested the disposition of

270

MTX at 15 min. The disposition of MTX between the strains and conditions followed the same trend as

271

observed at 5 min. At 15 min, plasma levels of MTX were increased in WT (4.7-fold, P < 0.01) and

272

Oatp1a/1b-/-;1B3tg (2.2-fold, P < 0.05) mice by rifampicin treatment but not in Oatp1a/1b-/- and

273

Oatp1a/1b-/-;1B1tg mice (Figure 3B). Decreases in liver MTX levels were significant in Oatp1a/1b-/-

274

;1B1tg (~3.5-fold, P < 0.01) and Oatp1a/1b-/-;1B3tg (~7.6-fold, P < 0.01) mice (Figure 3D and

275

Supplementary Figure 1B). Liver-to-plasma ratios clearly showed that hepatic uptake of MTX was

276

substantially decreased by rifampicin in WT (5.8-fold, P < 0.001) and Oatp1a/1b-/-;1B1tg (3.7-fold, P