Transporters Breast Cancer Resistance Protein Research Articles

Evaluation of the Clinical Drug-Drug Interaction Potential of Pritelivir on Transporters and CYP450 Enzymes Using a Cocktail Approach.

Pritelivir is a novel viral helicase-primase inhibitor active against herpes simplex virus. In vitro drug-drug interaction studies indicated that pritelivir has the potential for clinically relevant interactions on the cytochrome P450 (CYP) enzymes 2C8, 2C9, 3A4, and 2B6, and intestinal uptake transporter organic anion transporting polypeptide (OATP) 2B1 and efflux transporter breast cancer resistance protein (BCRP). This was evaluated in 2 clinical trials. In 1 trial the substrates flurbiprofen (CYP2C9), bupropion (CYP2B6), and midazolam (CYP3A4) were administered simultaneously as part of the Geneva cocktail, while the substrate celiprolol (OAPT2B1) was administered separately. In another trial, the substrates repaglinide (CYP2C8) and rosuvastatin (BCRP) were administered separately. Exposure parameters of the substrates and their metabolites (flurbiprofen and bupropion only) were compared after administration with or without pritelivir under therapeutic concentrations. The results of these trials indicated that pritelivir has no clinically relevant effect on the exposure of substrates for the intestinal uptake transporter OATP2B1 and the CYP enzymes 3A4, 2B6, 2C9, and 2C8, and has a weak inhibitory effect on the intestinal efflux transporter BCRP. In summary, the results suggest that pritelivir has a low drug-drug interaction potential.

BCRP drives intrinsic chemoresistance in chemotherapy-naïve breast cancer brain metastasis.

Although initially successful, treatments with chemotherapy often fail because of the recurrence of chemoresistant metastases. Since these tumors develop after treatment, resistance is generally thought to occur in response to chemotherapy. However, alternative mechanisms of intrinsic chemoresistance in the chemotherapy-naïve setting may exist but remain poorly understood. Here, we study drug-naïve murine breast cancer brain metastases (BCBMs) to identify how cancer cells growing in a secondary site can acquire intrinsic chemoresistance without cytotoxic agent exposure. We demonstrate that drug-naïve murine breast cancer cells that form cancer lesions in the brain undergo vascular mimicry and concomitantly express the adenosine 5'-triphosphate-binding cassette transporter breast cancer resistance protein (BCRP), a common marker of brain endothelial cells. We reveal that expression of BCRP by the BCBM tumor cells protects them against doxorubicin and topotecan. We conclude that BCRP overexpression can cause intrinsic chemoresistance in cancer cells growing in metastatic sites without prior chemotherapy exposure.

Ensemble Machine Learning Approaches Based on Molecular Descriptors and Graph Convolutional Networks for Predicting the Efflux Activities of MDR1 and BCRP Transporters

Multidrug resistance (MDR1) and breast cancer resistance protein (BCRP) play important roles in drug absorption and distribution. Computational prediction of substrates for both transporters can help reduce time in drug discovery. This study aimed to predict the efflux activity of MDR1 and BCRP using multiple machine learning approaches with molecular descriptors and graph convolutional networks (GCNs). In vitro efflux activity was determined using MDR1- and BCRP-expressing cells. Predictive performance was assessed using an in-house dataset with a chronological split and an external dataset. CatBoost and support vector regression showed the best predictive performance for MDR1 and BCRP efflux activities, respectively, of the 25 descriptor-based machine learning methods based on the coefficient of determination (R2). The single-task GCN showed a slightly lower performance than descriptor-based prediction in the in-house dataset. In both approaches, the percentage of compounds predicted within twofold of the observed values in the external dataset was lower than that in the in-house dataset. Multi-task GCN did not show any improvements, whereas multimodal GCN increased the predictive performance of BCRP efflux activity compared with single-task GCN. Furthermore, the ensemble approach of descriptor-based machine learning and GCN achieved the highest predictive performance with R2 values of 0.706 and 0.587 in MDR1 and BCRP, respectively, in time-split test sets. This result suggests that two different approaches to represent molecular structures complement each other in terms of molecular characteristics. Our study demonstrated that predictive models using advanced machine learning approaches are beneficial for identifying potential substrate liability of both MDR1 and BCRP.Graphical

Utilization of Rosuvastatin and Endogenous Biomarkers in Evaluating the Impact of Ritlecitinib on BCRP, OATP1B1, and OAT3 Transporter Activity

PurposeRitlecitinib, an inhibitor of Janus kinase 3 and tyrosine kinase expressed in hepatocellular carcinoma family kinases, is in development for inflammatory diseases. This study assessed the impact of ritlecitinib on drug transporters using a probe drug and endogenous biomarkers.MethodsIn vitro transporter-mediated substrate uptake and inhibition by ritlecitinib and its major metabolite were evaluated. Subsequently, a clinical drug interaction study was conducted in 12 healthy adult participants to assess the effect of ritlecitinib on pharmacokinetics of rosuvastatin, a substrate of breast cancer resistance protein (BCRP), organic anion transporting polypeptide 1B1 (OATP1B1), and organic anion transporter 3 (OAT3). Plasma concentrations of coproporphyrin I (CP-I) and pyridoxic acid (PDA) were assessed as endogenous biomarkers for OATP1B1 and OAT1/3 function, respectively.ResultsIn vitro studies suggested that ritlecitinib can potentially inhibit BCRP, OATP1B1 and OAT1/3 based on regulatory cutoffs. In the subsequent clinical study, coadministration of ritlecitinib decreased rosuvastatin plasma exposure area under the curve from time 0 to infinity (AUCinf) by ~ 13% and maximum concentration (Cmax) by ~ 27% relative to rosuvastatin administered alone. Renal clearance was comparable in the absence and presence of ritlecitinib coadministration. PK parameters of AUCinf and Cmax for CP-I and PDA were also similar regardless of ritlecitinib coadministration.ConclusionRitlecitinib does not inhibit BCRP, OATP1B1, and OAT3 and is unlikely to cause a clinically relevant interaction through these transporters. Furthermore, our findings add to the body of evidence supporting the utility of CP-I and PDA as endogenous biomarkers for assessment of OATP1B1 and OAT1/3 transporter activity.

A pharmacokinetic drug-drug interaction study between rosuvastatin and emvododstat, a potent anti-SARS-CoV-2 (COVID-19) DHODH (dihydroorotate dehydrogenase) inhibitor.

A therapeutic agent that targets both viral replication and the hyper-reactive immune response would offer a highly desirable treatment for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; COVID-19) management. Emvododstat (PTC299) was found to be a potent inhibitor of immunomodulatory and inflammation-related processes by the inhibition of dihydroorotate dehydrogenase (DHODH) to reduce SARS-CoV-2 replication. DHODH is the rate-limiting enzyme of the de novo pyrimidine nucleotide biosynthesis pathway. This drug interaction study was performed to determine whether emvododstat was an inhibitor of breast cancer resistance protein (BCRP) transporters in humans. Potential drug-drug interactions (DDIs) between emvododstat and a BCRP transporter substrate (rosuvastatin) were investigated by measuring plasma rosuvastatin concentrations before and after emvododstat administration. There was no apparent difference in rosuvastatin plasma exposure. The geometric means of maximum plasma rosuvastatin concentrations (Cmax ) were 4369 (rosuvastatin) and 5141 pg/mL (rosuvastatin + emvododstat) at 4 h postdose. Geometric mean rosuvastatin area under the concentration-time curve (AUC) from time 0 to the last measurable plasma concentration was 45 616 and 48975 h·pg/mL when administered alone and after 7 days of b.i.d. emvododstat dosing, respectively. Geometric least squares mean ratios for Cmax and AUC were approximately equal to 1. Overall, administration of multiple doses of 100 mg emvododstat b.i.d. for 7 days in combination with a single dose of rosuvastatin was safe and well tolerated. Emvododstat can be safely administered with other BCRP substrate drugs. Hence, pharmacokinetic DDI mediated via BCRP inhibition is not expected when emvododstat and BCRP substrates are coadministered.

Recent advances in the in vitro and in vivo methods to assess impact of P-glycoprotein and breast cancer resistance protein transporters in central nervous system drug disposition.

One challenge in central nervous system (CNS) drug discovery has been ensuring the blood-brain barrier (BBB) penetration of compounds at an efficacious concentration that provides suitable safety margins for clinical investigation. Research providing for the accurate prediction of brain penetration of compounds during preclinical discovery is important to a CNS program. In the BBB, P-glycoprotein (P-gp) (ABCB1) and breast cancer resistance protein (BCRP) (ABCG2) transporters have been demonstrated to play a major role in the active efflux of endogenous compounds and xenobiotics out of the brain microvessel cells and back to the systemic circulation. In the past 10years, there has been significant technological improvement in the sensitivity of quantitative proteomics methods, in vivo imaging, in vitro methods of organoid and microphysiological systems, as well as in silico quantitative physiological based pharmacokinetic and systems pharmacology models. Scientists continually leverage these advancements to interrogate the distribution of compounds in the CNS which may also show signals of substrate specificity of P-gp and/or BCRP. These methods have shown promise toward predicting and quantifying the unbound concentration(s) within the brain relevant for efficacy or safety. In this review, the authors have summarized the in vivo, in vitro, and proteomics advancements toward understanding the contribution of P-gp and/or BCRP in restricting the entry of compounds to the CNS of either healthy or special populations. Special emphasis has been provided on recent investigations on the application of a proteomics-informed approach to predict steady-state drug concentrations in the brain. Moreover, future perspectives regarding the role of these transporters in newer modalities are discussed.

Design, Synthesis and Biological Evaluation of Quinazolinamine Derivatives as Breast Cancer Resistance Protein and P-Glycoprotein Inhibitors with Improved Metabolic Stability.

A series of twenty-two quinazolinamine derivatives showing potent inhibitory activities on breast cancer resistance protein (BCRP) and p-glycoprotein (P-gp) were synthesized. A cyclopropyl-containing quinazolinamine 22 was identified as a dual BCRP and P-gp inhibitor, while azide-containing quinazolinamine 33 showed BCRP inhibitory activity. These lead compounds were further investigated in a battery of mechanistic experiments. Compound 22 changed the localization of BCRP and P-gp in cells, thus inhibiting the efflux of anticancer drugs by the two ATP-binding cassette (ABC) transporters. In addition, both 22 and 33 significantly stimulated the ATP hydrolysis of the BCRP transporter, indicating that they can be competitive substrates of the BCRP transporter, and thereby increase the accumulation of mitoxantrone in BCRP-overexpressing H460/MX20 cells. Azide derivative 33, exhibited a greater inhibitory effect on BCRP after UV activation and can serve as a valuable probe for investigating the interactions of quinazolinamine derivatives with BCRP. Notably, the dual BCRP and P-gp inhibitors 4-5, 22-24, 27, and BCRP inhibitor 33 showed improved metabolic stability compared to Ko143.

Loss of Function ABCG2 c.421C>A (rs2231142) Polymorphism Increases Steady-State Exposure to Mycophenolic Acid in Stable Renal Transplant Recipients: An Exploratory Matched Cohort Study.

Polymorphism ABCG2 c.421C>A (rs2231142) results in reduced activity of the important drug efflux transporter breast cancer-resistance protein (BCRP/ABCG2). One study has suggested that it may affect enterohepatic recirculation of mycophenolic acid (MPA). We evaluated the effect of rs2231142 on steady-state exposure to MPA in renal transplant recipients. Consecutive, stable adult (age ≥ 16years) renal transplant recipients on standard MPA-based immunosuppressant protocols (N = 68; 43 co-treated with cyclosporine, 25 with tacrolimus) underwent routine therapeutic drug monitoring after a week of initial treatment, and were genotyped for ABCG2 c.421C>A and 11 polymorphisms in genes encoding enzymes and transporters implicated in MPA pharmacokinetics. ABCG2 c.421C>A variant versus wild-type (wt) patients were matched with respect to demographic, biopharmaceutic, and genetic variables (full optimal combined with exact matching) and compared for dose-adjusted steady-state MPA pharmacokinetics [frequentist and Bayes (skeptical neutral prior) estimates of geometric means ratios, GMR]. Raw data (12 variant versus 56 wt patients) indicated around 40% higher total exposure (frequentist GMR = 1.45, 95% CI 1.10-1.91; Bayes = 1.38, 95% CrI 1.07-1.81) and around 30% lower total body clearance (frequentist GMR = 0.66, 0.58-0.90; Bayes = 0.71, 0.53-0.95) in variant carriers than in wt controls. The estimates were similar in matched data (11 variant versus 43 wt patients): exposure GMR = 1.41 (1.11-1.79) frequentist, 1.39 (1.15-1.81) Bayes, with 90.7% and 85.5% probability of GMR >1.20, respectively; clearance GMR = 0.73 (0.58-0.93) frequentist, 0.71 (0.54-0.95) Bayes. Sensitivity analysis indicated low susceptibility of the estimates to unmeasured confounding. Loss-off-function polymorphism ABCG2 c.421C>A increases steady-state exposure to MPA in stable renal transplant patients.

Impact of organic anion transporting polypeptide, P-glycoprotein, and breast cancer resistance protein transporters on observed tamoxifen and endoxifen concentration and adverse effects.

Drug transporters are important determinants of drug disposition and response. Tamoxifen is an antiestrogen for breast cancer therapy known for adverse drug reactions (ADRs). In this study, the involvement of OATP transporters in tamoxifen and endoxifen transport was studied in vitro while the impact of single nucleotide variation (SNV) in OATP and efflux transporters P-glycoprotein ( ABCB1 ) and Breast Cancer Resistance Protein ( ABCG2 ) on ADRs during tamoxifen therapy were assessed. Patients receiving tamoxifen for breast cancer, who were CYP2D6 normal metabolizers were enrolled ( n = 296). Patients completed a survey that captured ADRs and a blood sample was collected. Tamoxifen and endoxifen plasma concentration were measured, while DNA was genotyped for SNVs in ABCB1, ABCG2, SLCO1A2, SLCO1B1 , and SLCO2B1 . HEK293T cells were used to determine the extent of OATP-mediated transport of tamoxifen and endoxifen. Common SNVs of ABCB1, ABCG2, SLCO1A2 , and SLCO1B1 were not associated with tamoxifen or endoxifen concentration. However, tamoxifen concentration was significantly higher in carriers of SLCO2B1 c.935G>A (129.8 ng/mL) compared to wildtype (114.9 ng/mL; P = 0.036). Interestingly, subjects who carried SLCO1A2 c.38A>G reported significantly less dizziness ( P = 0.016). In-vitro analysis demonstrated increased cellular accumulation of tamoxifen in cells overexpressing OATP1A2 and 1B1, but endoxifen uptake was not effected in OATP overexpressing cells. We showed that OATP1A2 , a transporter known to be expressed at the blood-brain barrier, is capable of tamoxifen transport. Additionally, OATP1A2 c.38A>G was associated with reduced ADRs. Taken together, our findings suggest genetic variation in OATP transporters may be an important predictor of tamoxifen ADRs.

Chicken xenobiotic receptor upregulates the BCRP/ABCG2 transporter

The transporter breast cancer resistance protein (BCRP, encoded by ABCG2) influences the bioavailability and elimination of numerous substrate drugs during clinical therapy. The xenobiotic-sensing nuclear receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR) reportedly regulate functional expression of BCRP in mammalian species. However, it is unknown whether chicken xenobiotic receptor (CXR) regulates the expression and activity of BCRP. This study aimed to investigate the role of CXR in regulation of BCRP in chicken using in vitro and in vivo models. CXR was expressed in the main drug-metabolizing tissues of chickens, and its expression correlated well with that of the prototypical target genes CYP2H1 and ABCG2. BCRP expression was upregulated, and transporter activity was increased, in chicken primary hepatocytes exposed to the CXR agonist metyrapone. Using RNA interference and ectopic expression techniques to manipulate the cellular CXR status, we confirmed that ABCG2 gene regulation depended on CXR. In vivo experiments showed that metyrapone induced BCRP in the liver, kidney, duodenum, and jejunum of chickens. Coadministration of metyrapone significantly changed the pharmacokinetic behavior of orally administered florfenicol (substrate of chicken BCRP), with a lower Cmax (4.62 vs. 7.35 µg/mL, P < 0.01) and AUC0-t (15.83 vs. 24.18 h·mg/L, P < 0.01) as well as a higher Tmax (0.96 vs. 0.79 h, P < 0.05) and Cl/F (0.13 vs. 0.08 L/h/kg, P < 0.05). Together, our data suggest that CXR is involved in regulation of BCRP, and consequently, coadministration of a CXR agonist can affect the pharmacokinetic behavior of an orally administered BCRP substrate.

Kaempferol suppression of acute colitis is regulated by the efflux transporters BCRP and MRP2

The bioavailability of most flavonoids is low but effective in vivo; however, the mechanism of the efficacy of flavonoids has not been elucidated. Kaempferol is typical flavonoids., preliminary research indicates that kaempferol has a significant anti-colon cancer and anti-inflammatory effect. We reported previously that the triple recycling pathways significantly increase the local bioavailability of flavonoids and prolong the residence time of flavonoids in the liver and intestines, which is likely the mode by which flavonoids exert local efficacy. Notably, Efflux transporters (ETs), such as Breast cancer resistance protein (BCRP) and Multi drug resistance-associated protein 2 (MRP2), are the main regulatory molecules of the enterohepatic triple recycling pathways. Thus, our current study explored the regulation of kaempferol by BCRP and MRP2 and the role of BCRP and MRP2 in the suppression of Dextran sulfate sodium (DSS)-induced colitis by kaempferol. Herein, four mouse model was constructed, and the Ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS) method was established to simultaneously quantify kaempferol and its 3 metabolites and investigate the oral pharmacokinetic characteristics and tissue distribution of these compounds. In Bcrp−/−-Mrp2−/− mice, the movement of kaempferol via the enterohepatic triple recycling was blocked, and the preventative and therapeutic effects of this compound on acute colitis were inhibited. BCRP and MRP2 defects hindered the efflux of kaempferol and its phase II metabolites and increased the plasma levels. Our study revealed that the disposal of kaempferol was regulated by the ETs BCRP and MRP2, and most importantly, the results will help elucidate the mechanism by which kaempferol suppresses the transformation of colitis into colon cancer.

Co-administration of MDR1 and BCRP or EGFR/PI3K inhibitors overcomes lenvatinib resistance in hepatocellular carcinoma.

Lenvatinib is the first-line treatment for hepatocellular carcinoma (HCC), the most common type of primary liver cancer; however, some patients become refractory to lenvatinib. The underlying mechanism of lenvatinib resistance (LR) in patients with advanced HCC remains unclear. We focused on exploring the potential mechanism of LR and novel treatments of lenvatinib-resistant HCC. In particular, we established a Huh7 LR cell line and performed in vitro, bioinformatic, and biochemical assays. Additionally, we used a Huh7-LR cell-derived xenograft mouse model to confirm the results in vivo. Following LR induction, multidrug resistance protein 1 (MDR1) and breast cancer resistance protein (BCRP) transporters were markedly upregulated, and the epidermal growth factor receptor (EGFR), MEK/ERK, and PI3K/AKT pathways were activated. In vitro, the co-administration of elacridar, a dual MDR1 and BCRP inhibitor, with lenvatinib inhibited proliferation and induced apoptosis of LR cells. These effects might be due to inhibiting cancer stem-like cells (CSCs) properties, by decreasing colony formation and downregulating CD133, EpCAM, SOX-9, and c-Myc expression. Moreover, the co-administration of gefitinib, an EGFR inhibitor, with lenvatinib retarded proliferation and induced apoptosis of LR cells. These similar effects might be caused by the inhibition of EGFR-mediated MEK/ERK and PI3K/AKT pathway activation. In vivo, co-administration of lenvatinib with elacridar or gefitinib suppressed tumour growth and angiogenesis. Therefore, inhibiting MDR1 and BCRP transporters or targeting the EGFR/PI3K pathway might overcome LR in HCC. Notably, lenvatinib should be used to treat HCC after LR induction owing to its role in inhibiting tumour proliferation and angiogenesis. Our findings could help develop novel and effective treatment strategies for HCC.

Results From Drug-Drug Interaction Studies In Vitro and In Vivo Investigating the Inhibitory Effect of Finerenone on the Drug Transporters BCRP, OATP1B1, and OATP1B3.

Background and ObjectivesIn vitro and in vivo studies were performed with the novel, selective, nonsteroidal mineralocorticoid receptor antagonist finerenone to assess the relevance of inhibitory effects on the transporters breast cancer resistance protein (BCRP), organic anion transporting polypeptide 1B1 (OATP1B1), and OATP1B3. These transporters are involved in the disposition of a number of drugs, including statins. Statins are also a frequent comedication in patients receiving finerenone. Therefore, inhibitory effects on BCRP and OATPs are of potential clinical relevance.MethodsThe effect on the transport of specific substrates of BCRP and OATP1B1/1B3 was assessed in cell-based in vitro assays with finerenone or its metabolites. A fixed-sequence crossover study in 14 healthy male volunteers investigated the effects of finerenone (40 mg once daily) on the pharmacokinetics of the index substrate rosuvastatin (5 mg) administered alone, simultaneously with, or approximately 4 h before finerenone. The effect of finerenone on the endogenous OATP substrates coproporphyrin I and III was also assessed.ResultsBased on in vitro findings and threshold values proposed in regulatory guidelines, finerenone appeared to be a potentially relevant inhibitor of all three transporters. Relevant inhibition could also not be ruled out for the finerenone metabolites M1a (OATP1B1) and M3a (OATP1B1 and OAT1B3), which prompted an investigation into the relevance of these findings in vivo. After administration on a background of finerenone 40 mg, all point estimates of area under the curve ratios (114.47% [rosuvastatin], 99.62% [coproporphyrin I; simultaneous], and 105.28% [rosuvastatin; 4 h separation]) and maximum concentration ratios (111.24% [rosuvastatin], 101.22% [coproporphyrin I], 89.14% [coproporphyrin III; simultaneous], and 96.84% [rosuvastatin; 4 h separation]) of the investigated substrates were within 80.0–125%. In addition, the 90% confidence intervals of the ratios were within the conventional no-effect boundaries of 80.0% and 125% for rosuvastatin after temporally separated administration, and for coproporphyrin I and III.ConclusionAdministration of finerenone 40 mg once daily confers no risk of clinically relevant drug–drug interactions with substrates of BCRP, OATP1B1, or OATP1B3. The potential for relevant inhibition of these transporters suggested by in vitro findings was not confirmed in vivo.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13318-022-00794-5.

P-Glycoprotein and Breast Cancer Resistance Protein Transporter Inhibition by Cyclosporine and Quinidine on the Pharmacokinetics of Oral Rimegepant in Healthy Subjects.

Rimegepant (Nurtec ODT)—an orally administered, small‐molecule calcitonin gene–related peptide receptor antagonist indicated for the acute and preventive treatment of migraine—is a substrate for both the P‐glycoprotein and breast cancer resistance protein transporters in vitro. We evaluated the effects of concomitant administration of strong inhibitors of these transporters on the pharmacokinetics of rimegepant in healthy subjects. This single‐center, open‐label, randomized study was conducted in 2 parts, both of which were 2‐period, 2‐sequence, crossover studies. Part 1 (n = 15) evaluated the effect of a single oral dose of 200‐mg cyclosporine, a strong inhibitor of the P‐glycoprotein and breast cancer resistance protein transporters, on the pharmacokinetics of rimegepant 75 mg. Part 2 (n = 12) evaluated the effect of a single oral dose of 600‐mg quinidine, a strong selective P‐glycoprotein transporter, on the pharmacokinetics of rimegepant 75 mg. Coadministration with cyclosporine showed an increase in rimegepant area under the plasma concentration–time curve from time 0 to infinity and maximum observed concentration based on geometric mean ratios (90% confidence intervals [CIs]) of 1.6 (1.49‐1.72) and 1.41 (1.27‐1.57), respectively, versus rimegepant alone. Coadministration with quinidine showed an increase in rimegepant area under the plasma concentration–time curve from time 0 to infinity and maximum observed concentration geometric mean ratios (90% CIs) of 1.55 (1.40‐1.72) and 1.67 (1.46‐1.91), respectively, versus rimegepant alone. Strong P‐glycoprotein inhibitors (cyclosporine, quinidine) increased rimegepant exposures (>50%, <2‐fold). In parts 1 and 2, rimegepant coadministration was well tolerated and safe. The similar effect of cyclosporine and quinidine coadministration on rimegepant exposure suggests that inhibition of breast cancer resistance protein inhibition may have less influence on rimegepant exposure.

Drug-Drug Interaction of Letermovir and Atorvastatin in Healthy Participants.

Letermovir (MK-8228/AIC246) is a cytomegalovirus (CMV) DNA terminase complex inhibitor for CMV prophylaxis in adult patients undergoing hematopoietic stem cell transplant. It is cytochrome P450 (CYP) 3A inhibitor and inhibits organic anion transporting polypeptide 1B1/3 and breast cancer resistance protein transporters. Atorvastatin (ATV), a commonly used treatment for hypercholesterolemia, is a substrate of organic anion transporting polypeptide 1B1, potentially breast cancer resistance protein, and CYP3A. As letermovir may be coadministered with ATV, the effect of multiple-dose letermovir 480mg once daily on the pharmacokinetics of single-dose ATV 20mg and its metabolites (ortho-hydroxyatorvastatin [o-OH-ATV] and para-hydroxyatorvastatin [p-OH-ATV]) was evaluated in an open-label trial in healthy female adults (N = 14). ATV area under the plasma concentration-time curve from time 0 to infinity and maximum plasma concentration (Cmax ) increased ≈3-fold with letermovir coadministration. The time to ATV Cmax also increased, while apparent clearance decreased. The exposures of o-OH-ATV and p-OH-ATV were comparable in the presence versus absence of letermovir; however, o-OH-ATV Cmax decreased by 60% with coadministration, while p-OH-ATV Cmax was similar. Due to the increase in ATV exposure with letermovir coadministration, statin-associated adverse events such as myopathy should be closely monitored following coadministration. The dose of ATV should not exceed 20mg daily when coadministered with letermovir.

Cannabis constituents interact at the drug efflux pump BCRP to markedly increase plasma cannabidiolic acid concentrations

Cannabis is a complex mixture of hundreds of bioactive molecules. This provides the potential for pharmacological interactions between cannabis constituents, a phenomenon referred to as “the entourage effect” by the medicinal cannabis community. We hypothesize that pharmacokinetic interactions between cannabis constituents could substantially alter systemic cannabinoid concentrations. To address this hypothesis we compared pharmacokinetic parameters of cannabinoids administered orally in a cannabis extract to those administered as individual cannabinoids at equivalent doses in mice. Astonishingly, plasma cannabidiolic acid (CBDA) concentrations were 14-times higher following administration in the cannabis extract than when administered as a single molecule. In vitro transwell assays identified CBDA as a substrate of the drug efflux transporter breast cancer resistance protein (BCRP), and that cannabigerol and Δ9-tetrahydrocannabinol inhibited the BCRP-mediated transport of CBDA. Such a cannabinoid-cannabinoid interaction at BCRP transporters located in the intestine would inhibit efflux of CBDA, thus resulting in increased plasma concentrations. Our results suggest that cannabis extracts provide a natural vehicle to substantially enhance plasma CBDA concentrations. Moreover, CBDA might have a more significant contribution to the pharmacological effects of orally administered cannabis extracts than previously thought.

ABCB1 and ABCG2 Together Limit the Distribution of ABCB1/ABCG2 Substrates to the Human Retina and the ABCG2 Single Nucleotide Polymorphism Q141K (c.421C> A) May Lead to Increased Drug Exposure.

The widely expressed and poly-specific ABC transporters breast cancer resistance protein (ABCG2) and P-glycoprotein (ABCB1) are co-localized at the blood-brain barrier (BBB) and have shown to limit the brain distribution of several clinically used ABCB1/ABCG2 substrate drugs. It is currently not known to which extent these transporters, which are also expressed at the blood-retinal barrier (BRB), may limit drug distribution to the human eye and whether the ABCG2 reduced-function single-nucleotide polymorphism (SNP) Q141K (c.421C > A) has an impact on retinal drug distribution. Ten healthy male volunteers (five subjects with the c.421CC and c.421CA genotype, respectively) underwent two consecutive positron emission tomography (PET) scans after intravenous injection of the model ABCB1/ABCG2 substrate [11C]tariquidar. The second PET scan was performed with concurrent intravenous infusion of unlabelled tariquidar to inhibit ABCB1 in order to specifically reveal ABCG2 function.In response to ABCB1 inhibition with unlabelled tariquidar, ABCG2 c.421C > A genotype carriers showed significant increases (as compared to the baseline scan) in retinal radiotracer influx K 1 (+62 ± 57%, p = 0.043) and volume of distribution V T (+86 ± 131%, p = 0.043), but no significant changes were observed in subjects with the c.421C > C genotype. Our results provide the first evidence that ABCB1 and ABCG2 may together limit the distribution of systemically administered ABCB1/ABCG2 substrate drugs to the human retina. Functional redundancy between ABCB1 and ABCG2 appears to be compromised in carriers of the c.421C > A SNP who may therefore be more susceptible to transporter-mediated drug-drug interactions at the BRB than non-carriers.

BCRP/ABCG2 Transporter Regulates Accumulation of Cadmium in Kidney Cells: Role of the Q141K Variant in Modulating Nephrotoxicity.

Exposure to the environmental pollutant cadmium is ubiquitous, as it is present in cigarette smoke and the food supply. Over time, cadmium enters and accumulates in the kidneys, where it causes tubular injury. The breast cancer resistance protein (BCRP, ATP-Binding Cassette G2 ABCG2) is an efflux transporter that mediates the urinary secretion of pharmaceuticals and toxins. The ABCG2 genetic variant Q141K exhibits altered membrane trafficking that results in reduced efflux of BCRP substrates. Here, we sought to 1) evaluate the in vitro and in vivo ability of BCRP to transport cadmium and protect kidney cells from toxicity and 2) determine whether this protection is impaired by the Q141K variant. Cadmium concentrations, cellular stress, and toxicity were quantified in human embryonic kidney 293 cells expressing an empty vector (EV), BCRP wild-type (WT), or variant (Q141K) gene. Treatment with CdCl2 resulted in greater accumulation of cadmium and apoptosis in EV cells relative to WT cells. Exposure to CdCl2 induced expression of stress-related genes and proteins including MT-1A/MT-2A, NAD(P)H quinone dehydrogenase 1, and heme oxygenase-1 to a higher extent in EV cells compared with WT cells. Notably, the Q141K variant protected against CdCl2-induced activation of stress genes and cytotoxicity, but this protection was to a lesser magnitude than observed with WT BCRP. Lastly, concentrations of cadmium in the kidneys of Bcrp knockout mice were 40% higher than in WT mice, confirming that cadmium is an in vivo substrate of BCRP. In conclusion, BCRP prevents the accumulation of cadmium and protects against toxicity, a response that is impaired by the Q141K variant. SIGNIFICANCE STATEMENT: The breast cancer resistance protein transporter lowers cellular accumulation of the toxic heavy metal cadmium. This protective function is partially attenuated by the Q141K genetic variant in the ABCG2 gene.

Bisphenol A Inhibits the Transporter Function of the Blood-Brain Barrier by Directly Interacting with the ABC Transporter Breast Cancer Resistance Protein (BCRP).

The breast cancer resistance protein (BCRP) is an important efflux transporter in the blood-brain barrier (BBB), protecting the brain from a wide range of substances. In this study, we investigated if BCRP function is affected by bisphenol A (BPA), a high production volume chemical used in common consumer products, as well as by bisphenol F (BPF) and bisphenol S (BPS), which are used to substitute BPA. We employed a transwell-based in vitro cell model of iPSC-derived brain microvascular endothelial cells, where BCRP function was assessed by measuring the intracellular accumulation of its substrate Hoechst 33342. Additionally, we used in silico modelling to predict if the bisphenols could directly interact with BCRP. Our results showed that BPA significantly inhibits the transport function of BCRP. Additionally, BPA was predicted to bind to the cavity that is targeted by known BCRP inhibitors. Taken together, our findings demonstrate that BPA inhibits BCRP function in vitro, probably by direct interaction with the transporter. This effect might contribute to BPA’s known impact on neurodevelopment.

Influence of ABC transporters on the excretion of ciprofloxacin assessed with PET imaging in mice

Ciprofloxacin is a commonly prescribed fluoroquinolone antibiotic which is cleared by active tubular secretion and intestinal excretion. Ciprofloxacin is a known substrate of the ATP-binding cassette (ABC) transporters breast cancer resistance protein (BCRP) and multidrug resistance-associated protein 4 (MRP4). In this work, we used positron emission tomography (PET) imaging to investigate the influence of BCRP, MRP4, MRP2 and P-glycoprotein (P-gp) on the excretion of [18F]ciprofloxacin in mice. Dynamic 90-min PET scans were performed after intravenous injection of [18F]ciprofloxacin in wild-type mice without and with pre-treatment with the broad-spectrum MRP inhibitor MK571. Moreover, [18F]ciprofloxacin PET scans were performed in Abcc4(-/-), Abcc2(-/-), Abcc4(-/-)Abcg2(-/-) and Abcb1a/b(-/-)Abcg2(-/-) mice. In addition to non-compartmental pharmacokinetic (PK) analysis, a novel three-compartment PK model was developed for a detailed assessment of the renal disposition of [18F]ciprofloxacin. In MK571 pre-treated mice, a significant increase in the blood exposure to [18F]ciprofloxacin was observed along with a significant reduction in the renal and intestinal clearances. PK modelling revealed a significant reduction in renal radioactivity uptake (CL1) and in the rate constants for transfer of radioactivity from the corticomedullary renal region into blood (k2) and urine (k3), respectively, after MK571 administration. No changes in the renal clearance or in the estimated kidney PK model parameters were observed in any of the studied knockout models, while a significant reduction in the intestinal clearance was observed in Abcc2(-/-) and Abcc4(-/-)Abcg2(-/-) mice. Our data failed to reveal a role of any of the studied ABC transporters in the tubular secretion of ciprofloxacin. This may indicate that ciprofloxacin is handled in the kidneys by more than one transporter family, most likely with a great degree of mutual functional redundancy. Our study highlights the potential of PET imaging for an assessment of transporter-mediated renal excretion of radiolabelled drugs.