Short-lasting inhibition of hepatic uptake transporter OATP1B1 by tyrosine kinase inhibitor pazopanib

Preincubation-dependent inhibition of organic anion transporting polypeptide 2B1

Preincubation with inhibitor in organic anion transporting polypeptide (OATP) in vitro assays may increase the inhibition potency of inhibitors compared to conventional inhibition assays with only short inhibitor coincubation with substrate. The decrease in IC50 may affect prediction of drug-drug interactions (DDI) involving these transporters and inhibitors. Only few drugs, however, have been assessed for the preincubation-dependent inhibition of the OATP2B1 transporter. Therefore, we studied the effect of preincubation on OATP2B1 inhibition with five known OATP2B1 inhibitors (atorvastatin, erlotinib, ezetimibe, ticagrelor and simeprevir) in HEK293 cells transiently overexpressing OATP2B1. IC50 values were determined with and without inhibitor preincubation for 20 min with three different OATP2B1 substrates (dibromofluorescein, DBF; 5-carboxyfluorescein, 5-CF; estrone sulfate). Atorvastatin, ezetimibe, and simeprevir displayed more than 2-fold lower IC50 values after preincubation with at least one of the tested substrates. Altogether, 4 out of 15 inhibitor/substrate combinations exhibited more than 2-fold potentiation of IC50 after inhibitor preincubation. In addition, preincubation by itself, without inhibitor present with the substrate, resulted in more than 50% inhibition of OATP2B1-mediated uptake of DBF and/or 5-CF by atorvastatin, ticagrelor and simeprevir. Thus, erlotinib was the only inhibitor with no indication of potentiation of inhibition by preincubation with any of the tested substrates. In conclusion, preincubation resulted in inhibitor- and substrate-dependent inhibition of OATP2B1. These results support the conclusion that to reduce the risk of false negative DDI prediction, preincubation should be considered also in OATP2B1 inhibition assays.

Therapeutic Drug Monitoring of Pazopanib in Renal Cell Carcinoma and Soft Tissue Sarcoma: A Systematic Review

BACKGROUND

Pazopanib, an anti-angiogenic multitarget tyrosine kinase inhibitor, has been approved for the treatment of metastatic renal cell carcinoma and soft tissue sarcoma. However, its recommended dose does not always produce consistent outcomes, with some patients experiencing adverse effects or toxicity. This variability is due to differences in the systemic exposure to pazopanib. This review aimed to establish whether sufficient evidence exists for the routine or selective therapeutic drug monitoring of pazopanib in adult patients with approved indications.

METHODS

A systematic search of the PubMed and Web of Science databases using search terms related to pazopanib and therapeutic drug monitoring yielded 186 and 275 articles, respectively. Ten articles associated with treatment outcomes or toxicity due to drug exposure were selected for review.

RESULTS

The included studies were evaluated to determine the significance of the relationship between drug exposure/Ctrough and treatment outcomes and between drug exposure and toxicity. A relationship between exposure and treatment outcomes was observed in 5 studies, whereas the trend was nonsignificant in 4 studies. A relationship between exposure and toxicity was observed in 6 studies, whereas 2 studies did not find a significant relationship; significance was not reported in 3 studies.

CONCLUSIONS

Sufficient evidence supports the therapeutic drug monitoring of pazopanib in adult patients to improve its efficacy and/or safety in the approved indications.

Unveiling the therapeutic promise of natural products in alleviating drug-induced liver injury: Present advancements and future prospects

Drug-induced liver injury (DILI) refers to adverse reactions to small chemical compounds, biological agents, and medical products. These reactions can manifest as acute or chronic damage to the liver. From 1997 to 2016, eight drugs, including troglitazone, nefazodone, and lumiracoxib, were removed from the market due to their liver-damaging effects, which can cause diseases. We aimed to review the recent research on natural products and their bioactive components as hepatoprotective agents in mitigating DILI. Recent articles were fetched via searching the PubMed, PMC, Google Scholar, and Web of Science electronic databases from 2010 to January 2023 using relevant keywords such as "natural products," "acetaminophen," "antibiotics," "paracetamol," "DILI," "hepatoprotective," "drug-induced liver injury," "liver failure," and "mitigation." The studies reveal that the antituberculosis drug (acetaminophen) is the most frequent cause of DILI, and natural products have been largely explored in alleviating acetaminophen-induced liver injury. They exert significant hepatoprotective effects by preventing mitochondrial dysfunction and inflammation, inhibiting oxidative/nitrative stress, and macromolecular damage. Due to the bioavailability and dietary nature, using natural products alone or as an adjuvant with existing drugs is promising. To advance DILI management, it is crucial to conduct well-designed randomized clinical trials to evaluate natural products' efficacy and develop new molecules clinically. However, natural products are a promising solution for remedying drug-induced hepatotoxicity and lowering the risk of DILI.

Assessing Trans-Inhibition of OATP1B1 and OATP1B3 by Calcineurin and/or PPIase Inhibitors and Global Identification of OATP1B1/3-Associated Proteins

Organic anion transporting polypeptide (OATP) 1B1 and OATP1B3 are key determinants of drug-drug interactions (DDIs). Various drugs including the calcineurin inhibitor (CNI) cyclosporine A (CsA) exert preincubation-induced trans-inhibitory effects upon OATP1B1 and/or OATP1B3 (abbreviated as OATP1B1/3) by unknown mechanism(s). OATP1B1/3 are phosphoproteins; calcineurin, which dephosphorylates and regulates numerous phosphoproteins, has not previously been investigated in the context of preincubation-induced trans-inhibition of OATP1B1/3. Herein, we compare the trans-inhibitory effects exerted on OATP1B1 and OATP1B3 by CsA, the non-analogous CNI tacrolimus, and the non-CNI CsA analogue SCY-635 in transporter-overexpressing human embryonic kidney (HEK) 293 stable cell lines. Preincubation (10-60 min) with tacrolimus (1-10 µM) rapidly and significantly reduces OATP1B1- and OATP1B3-mediated transport up to 0.18 ± 0.03- and 0.20 ± 0.02-fold compared to the control, respectively. Both CsA and SCY-635 can trans-inhibit OATP1B1, with the inhibitory effects progressively increasing over a 60 min preincubation time. At each equivalent preincubation time, CsA has greater trans-inhibitory effects toward OATP1B1 than SCY-635. Preincubation with SCY-635 for 60 min yielded IC50 of 2.2 ± 1.4 µM against OATP1B1, which is ~18 fold greater than that of CsA (0.12 ± 0.04 µM). Furthermore, a proteomics-based screening for protein interactors was used to examine possible proteins and processes contributing to OATP1B1/3 regulation and preincubation-induced inhibition by CNIs and other drugs. A total of 861 and 357 proteins were identified as specifically associated with OATP1B1 and OATP1B3, respectively, including various protein kinases, ubiquitin-related enzymes, the tacrolimus (FK506)-binding proteins FKBP5 and FKBP8, and several known regulatory targets of calcineurin. The current study reports several novel findings that expand our understanding of impaired OATP1B1/3 function; these include preincubation-induced trans-inhibition of OATP1B1/3 by the CNI tacrolimus, greater preincubation-induced inhibition by CsA compared to its non-CNI analogue SCY-635, and association of OATP1B1/3 with various proteins relevant to established and candidate OATP1B1/3 regulatory processes.

Preincubation Time-Dependent, Long-Lasting Inhibition of Drug Transporters and Impact on the Prediction of Drug-Drug Interactions

Transporter-mediated drug-drug interaction (DDI) is of clinical concern, and the quantitative prediction of DDIs is an indispensable part of drug development. Cell-based inhibition assays, in which a representative probe substrate and a potential inhibitor are coincubated, are routinely performed to assess the inhibitory potential of new molecular entities on drug transporters. However, the inhibitory effect of cyclosporine A (CsA) on organic anion transporting polypeptide (OATP) 1B1 is substantially potentiated with CsA preincubation, and this effect is both long-lasting and dependent on the preincubation time. This phenomenon has also been reported with transporters other than OATP1Bs, but it is considered more prevalent among OATP1Bs and organic cation transporters. Regulatory agencies have also noted this preincubation effect and have recommended that pharmaceutical companies consider inhibitor preincubation when performing in vitro OATP1B1 and OATP1B3 inhibition studies. Although the underlying mechanisms responsible for the preincubation effect are not fully understood, a trans-inhibition mechanism was recently demonstrated for OATP1B1 inhibition by CsA, in which CsA inhibited OATP1B1 not only extracellularly (cis-inhibition) but also intracellularly (trans-inhibition). Furthermore, the trans-inhibition potency of CsA was much greater than that of cis-inhibition, suggesting that trans-inhibition might be a key driver of clinical DDIs of CsA with OATP1B substrate drugs. Although confidence in transporter-mediated DDI prediction is generally considered to be low, the predictability might be further improved by incorporating the trans-inhibition mechanism into static and dynamic models for preincubation-dependent inhibitors of OATP1Bs and perhaps other transporters. SIGNIFICANCE STATEMENT: Preincubation time-dependent, long-lasting inhibition has been observed for OATP1B1 and other solute carrier transporters in vitro. Recently, a trans-inhibition mechanism for the preincubation effect of CsA on OATP1B1 inhibition was identified, with the trans-inhibition potency being greater than that of cis-inhibition. The concept of trans-inhibition may allow us to further understand the mechanism of transporter-mediated DDIs not only for OATP1B1 but also for other transporters and to improve the accuracy and confidence of DDI predictions.

Identification of the Stapled α-Helical Peptide ATSP-7041 as a Substrate and Strong Inhibitor of OATP1B1 In Vitro

ATSP-7041, a stapled α-helical peptide that inhibits murine double minute-2 (MDM2) and MDMX activities, is a promising modality targeting protein-protein interactions. As peptides of molecular weights over 1000 Da are not usually evaluated, data on the drug-drug interaction (DDI) potential of stapled α-helical peptides remain scarce. Here, we evaluate the interaction of ATSP-7041 with hepatic cytochrome P450s (CYPs; CYP1A2, CYP2C9, CYP2C19, CYP3A4, and CYP2D6) and transporters (organic anion transporting polypeptides (OATPs; OATP1B1 and OATP1B3), P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP)). ATSP-7041 demonstrated negligible metabolism in human liver S9 fraction and a limited inhibition of CYP activities in yeast microsomes or S9 fractions. On the contrary, a substantial uptake by OATPs in HEK 293 cells, a strong inhibition of OATP activities in the cells, and an inhibition of P-gp and BCRP activities in reversed membrane vesicles were observed for ATSP-7041. A recent report describes that ALRN-6924, an ATSP-7041 analog, inhibited OATP activities in vivo; therefore, we focused on the interaction between ATSP-7041 and OATP1B1 to demonstrate that ATSP-7041, as a higher molecular weight stapled peptide, is a substrate and strong inhibitor of OATP1B1 activity. Our findings demonstrated the possibility of transporter-mediated DDI potential by high molecular weight stapled peptides and the necessity of their evaluation for drug development.

Studying the right transporter at the right time: an in vitro strategy for assessing drug-drug interaction risk during drug discovery and development

INTRODUCTION

Transporters are significant in dictating drug pharmacokinetics, thus inhibition of transporter function can alter drug concentrations resulting in drug-drug interactions (DDIs). Because they can impact drug toxicity, transporter DDIs are a regulatory concern for which prediction of clinical effect from in vitro data is critical to understanding risk.

AREA COVERED

The authors propose in vitro strategies to assist mitigating/removing transporter DDI risk during development by frontloading specific studies, or managing patient risk in the clinic. An overview of clinically relevant drug transporters and observed DDIs are provided, alongside presentation of key considerations/recommendations for in vitro study design evaluating drugs as inhibitors or substrates. Guidance on identifying critical co-medications, clinically relevant disposition pathways and using mechanistic static equations for quantitative prediction of DDI is compiled.

EXPERT OPINION

The strategies provided will facilitate project teams to study the right transporter at the right time to minimise development risks associated with DDIs. To truly alleviate or manage clinical risk, the industry will benefit from moving away from current qualitative basic static equation approaches to transporter DDI hazard assessment towards adopting the use of mechanistic models to enable quantitative DDI prediction, thereby contextualising risk to ascertain whether a transporter DDI is simply pharmacokinetic or clinically significant requiring intervention.

Identification of Drug Transporter Genomic Variants and Inhibitors That Protect Against Doxorubicin-Induced Cardiotoxicity

BACKGROUND

Multiple pharmacogenomic studies have identified the synonymous genomic variant rs7853758 (G > A, L461L) and the intronic variant rs885004 in SLC28A3 (solute carrier family 28 member 3) as statistically associated with a lower incidence of anthracycline-induced cardiotoxicity. However, the true causal variant(s), the cardioprotective mechanism of this locus, the role of SLC28A3 and other solute carrier (SLC) transporters in anthracycline-induced cardiotoxicity, and the suitability of SLC transporters as targets for cardioprotective drugs has not been investigated.

METHODS

Six well-phenotyped, doxorubicin-treated pediatric patients from the original association study cohort were recruited again, and human induced pluripotent stem cell-derived cardiomyocytes were generated. Patient-specific doxorubicin-induced cardiotoxicity (DIC) was then characterized using assays of cell viability, activated caspase 3/7, and doxorubicin uptake. The role of SLC28A3 in DIC was then queried using overexpression and knockout of SLC28A3 in isogenic human-induced pluripotent stem cell-derived cardiomyocytes using a CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated protein 9). Fine-mapping of the SLC28A3 locus was then completed after SLC28A3 resequencing and an extended in silico haplotype and functional analysis. Genome editing of the potential causal variant was done using cytosine base editor. SLC28A3-AS1 overexpression was done using a lentiviral plasmid-based transduction and was validated using stranded RNA-sequencing after ribosomal RNA depletion. Drug screening was done using the Prestwick Chemical Library (n = 1200), followed by in vivo validation in mice. The effect of desipramine on doxorubicin cytotoxicity was also investigated in 8 cancer cell lines.

RESULTS

Here, using the most commonly used anthracycline, doxorubicin, we demonstrate that patient-derived cardiomyocytes recapitulate the cardioprotective effect of the SLC28A3 locus and that SLC28A3 expression influences the severity of DIC. Using Nanopore-based fine-mapping and base editing, we identify a novel cardioprotective single nucleotide polymorphism, rs11140490, in the SLC28A3 locus; its effect is exerted via regulation of an antisense long noncoding RNA (SLC28A3-AS1) that overlaps with SLC28A3. Using high-throughput drug screening in patient-derived cardiomyocytes and whole organism validation in mice, we identify the SLC competitive inhibitor desipramine as protective against DIC.

CONCLUSIONS

This work demonstrates the power of the human induced pluripotent stem cell model to take a single nucleotide polymorphism from a statistical association through to drug discovery, providing human cell-tested data for clinical trials to attenuate DIC.

Regulation of OATP1B1 Function by Tyrosine Kinase-mediated Phosphorylation

PURPOSE

OATP1B1 (SLCO1B1) is the most abundant and pharmacologically relevant uptake transporter in the liver and a key mediator of xenobiotic clearance. However, the regulatory mechanisms that determine OATP1B1 activity remain uncertain, and as a result, unexpected drug-drug interactions involving OATP1B1 substrates continue to be reported, including several involving tyrosine kinase inhibitors (TKI).

EXPERIMENTAL DESIGN

OATP1B1-mediated activity in overexpressing HEK293 cells and hepatocytes was assessed in the presence of FDA-approved TKIs, while rosuvastatin pharmacokinetics in the presence of an OATP1B1 inhibiting TKI were measured in vivo. Tyrosine phosphorylation of OATP1B1 was determined by LC/MS-MS-based proteomics and transport function was measured following exposure to siRNAs targeting 779 different kinases.

RESULTS

Twenty-nine of 46 FDA-approved TKIs studied significantly inhibit OATP1B1 function. Inhibition of OATP1B1 by TKIs, such as nilotinib, is predominantly noncompetitive, can increase systemic concentrations of rosuvastatin in vivo, and is associated with reduced phosphorylation of OATP1B1 at tyrosine residue 645. Using genetic screens and functional validation studies, the Src kinase LYN was identified as a potential regulator of OATP1B1 activity that is highly sensitive to inhibition by various TKIs at clinically relevant concentrations.

CONCLUSIONS

A novel kinase-dependent posttranslational mechanism of OATP1B1 activation was identified and interference with this process by TKIs can influence the elimination of a broad range of xenobiotic substrates.

6-Hydroxyindole is an endogenous long-lasting OATP1B1 inhibitor elevated in renal failure patients

The hepatic uptake transporter organic anion transporting polypeptide (OATP) 1B1 is inhibited by some uremic toxins; however, direct inhibition can only partially explain the delayed systemic elimination of substrate drugs in renal failure patients. This study aimed to examine the long-lasting inhibition of OATP1B1 by uremic toxins and their metabolites. Preincubation of HEK293/OATP1B1 cells with 21 uremic toxins resulted in almost no change in the uptake of a typical substrate [³H]estrone-3-sulfate (E₁S), although some directly inhibited [³H]E₁S uptake. In contrast, preincubation with an indole metabolite, 6-hydroxyindole, reduced [³H]E₁S uptake, even after the inhibitor was washed out before [³H]E₁S incubation. Such long-lasting inhibition by 6-hydroxyindole was time-dependent and recovered after a 3-h incubation without 6-hydroxyindole. Preincubation with 6-hydroxyindole increased the Km for [³H]E₁S uptake with minimal change in Vmax. This was compatible with no change in the cell-surface expression of OATP1B1, as assessed by a biotinylation assay. Preincubation with 6-hydroxyindole reduced [³H]E₁S uptake in human hepatocytes without changes in OATP1B1 mRNA. Plasma concentration of 6-hydroxyindole in renal failure patients increased as renal function decreased, but might be insufficient to exhibit potent OATP1B1 inhibition. In conclusion, 6-hydroxyindole is an endogenous long-lasting OATP1B1 inhibitor with elevated plasma concentrations in renal failure patients.

Role of OATP1B1 and OATP1B3 in Drug-Drug Interactions Mediated by Tyrosine Kinase Inhibitors

Failure to recognize important features of a drug's pharmacokinetic characteristics is a key cause of inappropriate dose and schedule selection, and can lead to reduced efficacy and increased rate of adverse drug reactions requiring medical intervention. As oral chemotherapeutic agents, tyrosine kinase inhibitors (TKIs) are particularly prone to cause drug-drug interactions as many drugs in this class are known or suspected to potently inhibit the hepatic uptake transporters OATP1B1 and OATP1B3. In this article, we provide a comprehensive overview of the published literature and publicly-available regulatory documents in this rapidly emerging field. Our findings indicate that, while many TKIs can potentially inhibit the function of OATP1B1 and/or OATP1B3 and cause clinically-relevant drug-drug interactions, there are many inconsistencies between regulatory documents and the published literature. Potential explanations for these discrepant observations are provided in order to assist prescribing clinicians in designing safe and effective polypharmacy regimens, and to provide researchers with insights into refining experimental strategies to further predict and define the translational significance of TKI-mediated drug-drug interactions.

Static Model-Based Assessment of OATP1B1-Mediated Drug Interactions with Preincubation-Dependent Inhibitors Based on Inactivation and Recovery Kinetics

Quantitative assessment of drug-drug interactions (DDIs) via organic anion transporting polypeptide (OATP) 1B1 is one of the key issues in drug development. Although OATP1B1 inhibition exhibits unique characteristics, including preincubation dependence for some inhibitors, a limited approach has been attempted based on the static model that considers such preincubation dependence in the prediction of DDIs via OATP1B1. The present study aimed to establish the prediction of DDIs via OATP1B1 using preincubation-dependent inhibitors based on the static model and incorporating both inactivation and recovery of OATP1B1 activity. Cyclosporine A was selected as a preincubation-dependent inhibitor, as well as five substrates that include probes and pharmaceuticals. The inhibition ratio (R value) calculated on the basis of a conventional static model, considering inhibition of OATP1B1 and contribution ratio of OATP1B1 to the overall hepatic uptake, was much lower than the reported AUC ratio, even when IC₅₀ values were estimated after preincubation conditions. Conversely, the R value that was estimated by considering inactivation and recovery parameters was closer to the AUC ratio. The R value that was calculated assuming the complete contribution of OATP1B1 was much higher than the AUC ratio, avoiding false-negative prediction. The R value estimated by considering inactivation and recovery for another combination of a preincubation-dependent inhibitor, asunaprevir, and substrate drug, rosuvastatin, was also closer to the AUC ratio. Thus, R values calculated based on such OATP1B1 kinetics would be potential alternative indexes for the quantitative prediction of OATP1B1-mediated DDIs using preincubation-dependent inhibitors, although this prediction is affected by estimation of the contribution ratio of substrates. SIGNIFICANCE STATEMENT: Static model-based quantitative prediction of organic anion transporting polypeptide 1B1-mediated drug-drug interactions induced by preincubation-dependent inhibitors was newly proposed to avoid false-negative prediction.