Inhibitory Effect of Crizotinib on Creatinine Uptake by Renal Secretory Transporter OCT2

Acute Kidney Injury Associated with Anticancer Therapies: Small Molecules and Targeted Therapies

Molecular targeted therapy has revolutionized cancer treatment by significantly improving patient survival compared with standard conventional chemotherapies. The use of these drugs targets specific molecules or targets, which block growth and spread of cancer cells. Many of these therapies have been approved for use with remarkable success in breast, blood, colorectal, lung, and ovarian cancers. The advantage over conventional chemotherapy is its ability to deliver drugs effectively with high specificity while being less toxic. Although known as "targeted," many of these agents lack specificity and selectivity, and they tend to inhibit multiple targets, including those in the kidneys. The side effects usually arise because of dysregulation of targets of the inhibited molecule in normal tissue. The off-target effects are caused by drug binding to unintended targets. The on-target effects are associated with inhibition toward the pathway reflecting inappropriate inhibition or activation of the intended drug target. Early detection and correct management of kidney toxicities is crucial to preserve kidney functions. The knowledge of these toxicities helps guide optimal and continued utilization of these potent therapies. This review summarizes the different types of molecular targeted therapies used in the treatment of cancer and the incidence, severity, and pattern of nephrotoxicity caused by them, with their plausible mechanism and proposed treatment recommendations.

Application of transporter assays for drug discovery and development: an update of the literature

INTRODUCTION

Determining whether a new drug is a substrate, inhibitor or inducer of efflux or uptake membrane transporters has become a routine process during drug discovery and development. In vitro assays are utilized to establish whether a new drug has the potential to be an object (substrate) or precipitant (inhibitor, inducer) in transporter-mediated clinical drug-drug interactions. The findings from these in vitro experiments are then used to determine whether further in vivo drug interaction studies are necessary for a new drug.

AREAS COVERED

This article provides an update on in vitro transporter assays, focusing on new uses of transfected cells, time-dependent inhibition, transporter induction, and complex model systems.

EXPERT OPINION

The newer in vitro assays add to the toolbox in defining new drugs as transporter substrates, inhibitors, or inducers. Complex models such as spheroids, organoids, and microphysiological systems require standardization and further research with model transporter substrates and inhibitors. In drug discovery, the more traditional transporter assays may be employed as substrate and inhibitor screening assays. In drug development, more complex cell models can be employed in later drug development to better understand how transporter(s) are involved in the absorption, distribution, and excretion of new drugs.

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.

Pharmacokinetic interactions of niclosamide in rats: Involvement of organic anion transporters 1 and 3 and organic cation transporter 2

Niclosamide is an anthelmintic drug with a long history of use and is generally safe and well tolerated in humans. As the conventional dose of niclosamide results in a low but certain level in systemic circulation, drug interactions with concomitant drugs should be considered. We aimed to investigate the interaction between niclosamide and drug transporters, as such information is currently limited. Niclosamide inhibited the transport activity of OATP1B1, OATP1B3, OAT1, OAT3, and OCT2 in vitro. Among them, the inhibitory effects on OAT1, OAT3, and OCT2 were strong, with IC50 values of less than 1 μM. When 3 mg/kg of niclosamide was co-administered to rats, systemic exposure to furosemide (a substrate of OAT1/3) and metformin (a substrate of OCT2) increased, and the renal clearance (CLr) of the drugs significantly decreased. These results suggest that niclosamide inhibits renal transporters, OAT1/3 and OCT2, not only in vitro but also in vivo, resulting in increased systemic exposure to the substrates of the transporters by strongly blocking the urinary elimination pathway in rats. The findings of this study will support a meticulous understanding of the transporter-mediated drug interactions of niclosamide and consequently aid in effective and safe use of niclosamide.

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.

Quantitative Consideration of Clinical Increases in Serum Creatinine Caused by Renal Transporter Inhibition

Creatinine is a common biomarker of renal function and is secreted in the renal tubular cells via drug transporters, such as organic cation transporter 2 and multidrug and toxin extrusion (MATE) 1/2-K. To differentiate between drug-induced acute kidney injury (AKI) and drug interactions through the renal transporter, it has been examined whether these transporter inhibitions quantitatively explained increases in serum creatinine (SCr) at their clinically relevant concentrations using drugs without any changes in renal function. For such renal transporter inhibitors and recently approved tyrosine kinase inhibitors (TKIs), this mini-review describes clinical increases in SCr and inhibitory potentials against the renal transporters. Most cases of SCr elevations can be explained by considering the renal transporter inhibitions based on unbound maximum plasma concentrations, except for drugs associated with obvious changes in renal function. SCr increases for cobicistat, dolutegravir, and dronedarone, and some TKIs were significantly underestimated, and these underestimations were suggested to be associated with low plasma unbound fractions. Sensitivity analysis of SCr elevations regarding inhibitory potentials of MATE1/2-K demonstrated that typical inhibitors such as cimetidine, DX-619, pyrimethamine, and trimethoprim could give false interpretations of AKI according to the criteria based on relative or absolute levels of SCr elevations. Recent progress and current challenges of physiologically-based pharmacokinetics modeling for creatinine disposition were also summarized. Although it should be noted for the potential impact of in vitro assay designs on clinical translatability of transporter inhibitions data, mechanistic approaches could support decision-making in clinical development to differentiate between AKI and creatinine-drug interactions. SIGNIFICANCE STATEMENT: Serum creatinine (SCr) is widely used as an indicator of kidney function, but it increases due to inhibitions of renal transporters, such as multidrug and toxin extrusion protein 1/2-K despite no functional changes in the kidney. Such SCr elevations were quantitatively explained by renal transporter inhibitions except for some drugs with high protein binding. The present analysis demonstrated that clinically relevant inhibitors of the renal transporters could cause SCr elevations above levels corresponding to acute kidney injury criteria.

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.

Emerging Roles of Uremic Toxins and Inflammatory Cytokines in the Alteration of Hepatic Drug Disposition in Patients with Kidney Dysfunction

Patients with kidney dysfunction exhibit distinct pharmacokinetic profiles compared to those with normal kidney function. Hence, it is desirable to monitor the drug efficacy and toxicity caused by fluctuations in plasma drug concentrations associated with kidney dysfunction. Recently, pharmacokinetic information of drugs excreted mainly through the urine of patients with kidney dysfunction has been reported via drug-labeling information. Pharmacokinetic changes in drugs mainly eliminated by the liver cannot be overlooked as drug metabolism and/or transport activity in the liver may also be altered in patients with kidney dysfunction; however, the underlying mechanisms remain unclear. To plan an appropriate dosage regimen, it is necessary to clarify the underlying processes of functional changes in pharmacokinetic proteins. In recent years, uremic toxins have been shown to reduce the activity and/or expression of renal and hepatic transporters. This inhibitory effect has been reported to be time-dependent. In addition, inflammatory cytokines, such as interleukin-6, released from immune cells activated by uremic toxins and/or kidney injury can reduce the expression levels of drug-metabolizing enzymes and transporters in human hepatocytes. In this mini-review, we have summarized the renal and hepatic pharmacokinetic changes as well as the potential underlying mechanisms in kidney dysfunction, such as the chronic kidney disease and acute kidney injury. SIGNIFICANCE STATEMENT: Patients with kidney dysfunction exhibit distinct pharmacokinetic profiles compared to those with normal kidney function. Increased plasma concentrations of uremic toxins and inflammatory cytokines during kidney disease may potentially affect the activities and/or expression levels of drug-metabolizing enzymes and transporters in the liver and kidneys.

Pseudo-AKI associated with targeted anti-cancer agents-the truth is in the eye of the filtration marker

Besides true acute kidney injury (AKI), the occurrence of pseudo-AKI has been associated with several targeted agents. To improve the management of cancer patients treated with targeted agents, we need to be aware of this and use diagnostic approaches to differentiate between pseudo-AKI and AKI. In an article by Wijtvliet et al. in this issue of CKJ, tepotinib is added to the list of targeted agents associated with pseudo-AKI. In this editorial we discuss the current literature regarding pseudo-AKI and true AKI associated with targeted agents, and subsequently propose a management strategy to monitor kidney function in patients treated with targeted agents.

The Role of Organic Cation Transporters in the Pharmacokinetics, Pharmacodynamics and Drug-Drug Interactions of Tyrosine Kinase Inhibitors

Tyrosine kinase inhibitors (TKIs) decisively contributed in revolutionizing the therapeutic approach to cancer, offering non-invasive, tolerable therapies for a better quality of life. Nonetheless, degree and duration of the response to TKI therapy vary depending on cancer molecular features, the ability of developing resistance to the drug, on pharmacokinetic alterations caused by germline variants and unwanted drug-drug interactions at the level of membrane transporters and metabolizing enzymes. A great deal of approved TKIs are inhibitors of the organic cation transporters (OCTs). A handful are also substrates of them. These transporters are polyspecific and highly expressed in normal epithelia, particularly the intestine, liver and kidney, and are, hence, arguably relevant sites of TKI interactions with other OCT substrates. Moreover, OCTs are often repressed in cancer cells and might contribute to the resistance of cancer cells to TKIs. This article reviews the OCT interactions with approved and in-development TKIs reported in vitro and in vivo and critically discusses the potential clinical ramifications thereof.

Role of Drug Transporters in Elucidating Inter-Individual Variability in Pediatric Chemotherapy-Related Toxicities and Response

Pediatric cancer treatment has evolved significantly in recent decades. The implementation of risk stratification strategies and the selection of evidence-based chemotherapy combinations have improved survival outcomes. However, there is large interindividual variability in terms of chemotherapy-related toxicities and, sometimes, the response among this population. This variability is partly attributed to the functional variability of drug-metabolizing enzymes (DME) and drug transporters (DTS) involved in the process of absorption, distribution, metabolism and excretion (ADME). The DTS, being ubiquitous, affects drug disposition across membranes and has relevance in determining chemotherapy response in pediatric cancer patients. Among the factors affecting DTS function, ontogeny or maturation is important in the pediatric population. In this narrative review, we describe the role of drug uptake/efflux transporters in defining pediatric chemotherapy-treatment-related toxicities and responses. Developmental differences in DTS and the consequent implications are also briefly discussed for the most commonly used chemotherapeutic drugs in the pediatric population.

Targeted Cancer Therapies Causing Elevations in Serum Creatinine Through Tubular Secretion Inhibition: A Case Report and Review of the Literature

Rationale

Targeted cancer therapies have revolutionized the field of oncology by selecting for specific molecular pathways, thus improving overall clinical prognosis. However, many of these targeted treatments have been reported to have adverse kidney effects, including acute kidney injury, interstitial nephritis, and glomerular disease. Furthermore, some of these targeted therapies have also been found to cause an asymptomatic rise in serum creatinine levels through inhibition of active tubular secretion.

Presenting concerns

A 79-year-old woman was being followed for stage 4 A2 chronic kidney disease secondary to type 2 diabetes and longstanding hypertension. She was diagnosed with invasive mammary carcinoma and was initiated on letrozole, an aromatase inhibitor, and palbociclib, a selective cyclin-dependent kinase inhibitor, was subsequently added. Prior to the initiation of her treatments, her baseline estimated glomerular filtration rate (eGFR) fluctuated between 25 and 28 mL/min/1.73 m2 over the previous year. After initiating palbociclib, her serum creatinine progressively increased, despite having well-controlled blood pressure and diabetes. In addition, there was no history of pre-renal events nor any sonographic evidence of obstruction. Within 7 months, her eGFR based on serum creatinine had decreased down to 12 mL/min/1.73 m2.

Interventions

Given that there were no clinical or other biochemical changes suggestive of worsening renal function, a serum cystatin C was measured using an immunoturbidimetric assay, which was 1.71 mg/L and correlated with an eGFR of 33 mL/min/1.73 m2 based on the chronic kidney disease epidemiology collaboration (CKD-EPI) cystatin C equation (2012). This value was consistent with her previous baseline. Based on these findings, the significant decrease in eGFR measured by serum creatinine was attributed to the inhibitory effects of palbociclib on tubular creatinine secretion, rather than representing true kidney damage. Thus, a kidney biopsy was not performed in this context.

Outcomes

Seven months later, a repeat serum cystatin C was repeated to assess for any worsening of the patient's kidney function and revealed an eGFR of 35 mL/min/1.73 m2 based on the CKD-EPI cystatin C equation (2012), thus revealing stable kidney function and reinforcing the inhibitory effects of palbociclib on tubular creatinine secretion through its direct effects on kidney transporters.

Teaching points

This case report and literature review acknowledges the importance of using alternative methods of assessing kidney function when patients are undergoing targeted cancer therapies known to affect tubular creatinine secretion, which include cyclin-dependent kinase 4/6 inhibitors, poly(adenosine diphosphate-ribose) polymerase inhibitors, tyrosine kinase inhibitors, and mesenchymal-epithelial transition inhibitors. The use of non-creatinine-based markers of glomerular filtration rate (GFR), such as cystatin C and nuclear renal scans, will allow for more accurate estimation of kidney function in the appropriate setting, thus avoiding invasive diagnostic tests and unnecessary adjustments of treatment plans. However, certain targeted cancer therapies have also been proven to cause true kidney injury; therefore, physicians must still maintain a high degree of suspicion and consider invasive investigations and/or cessation or reduction of treatments when alternative measurements of kidney function do not suggest an underestimation of GFR via serum creatinine.

Challenges and Opportunities for Improved Drug-Drug Interaction Predictions for Renal OCT2 and MATE1/2-K Transporters

Transporters contribute to renal elimination of drugs; therefore drug disposition can be impacted if transporters are inhibited by comedicant drugs. Regulatory agencies have provided guidelines to assess potential drug-drug interaction (DDI) risk for renal organic cation transporter 2 (OCT2) and multidrug and toxin extrusion 1 and 2-K (MATE1/2-K) transporters. Despite this, there are challenges with translating in vitro data using currently available tools to obtain a quantitative assessment of DDI risk in the clinic. Given the high number of drugs and new molecular entities showing in vitro inhibition toward OCT2 and/or MATE1/2-K and the lack of translation to clinically significant effects, it is reasonable to question whether the current in vitro assay design and modeling practice has led to unnecessary clinical evaluation. The aim of this review is to assess and discuss available in vitro and clinical data along with prediction models intended to provide clinical context of risk, including static models proposed by regulatory agencies and physiologically-based pharmacokinetic models, in order to identify best practices and areas of future opportunity. This analysis highlights that different in vitro assay designs, including substrate and cell systems used, strongly influence the derived concentration of drug producing 50% inhibition values and contribute to high variability observed across laboratories. Furthermore, the lack of sensitive index substrates coupled with specific inhibitors for individual transporters necessitates the use of complex models to evaluate clinical DDI risk.

Experimental and modeling evidence supporting the trans-inhibition mechanism for preincubation time-dependent, long-lasting inhibition of organic anion transporting polypeptide (OATP) 1B1 by cyclosporine A

Cyclosporine A (CsA) and rifampin are potent inhibitors of organic anion transporting polypeptide (OATP) 1B1 and are widely used to assess the risk for drug-drug interactions. CsA displays preincubation time-dependent, long-lasting inhibition of OATP1B1 in vitro and in rats in vivo, and a proposed mechanism is the trans-inhibition by which CsA inhibits OATP1B1 from the inside of cells. The current study aimed to experimentally validate the proposed mechanism using HEK293 cells stably expressing OATP1B1. The uptake of CsA reached a plateau following around 60-min incubation, with the cell-to-buffer concentration ratio of 3930, reflective of the high-affinity, high-capacity intracellular binding of CsA. The time course of CsA uptake was analyzed to estimate the kinetic parameters for permeability clearance and intracellular binding. When the OATP1B1-mediated uptake of [³H]estradiol-17β-glucuronide was measured following preincubation with CsA for 5 to 120 min, apparent K_i values became lower with longer preincubation. Our kinetic modeling incorporated the two reversible inhibition constants [K_i,trans and K_i,cis for the inhibition from inside (trans-inhibition) and outside (cis-inhibition) of cells, respectively] and estimated K_i,trans value of CsA was smaller by 48-fold than the estimated K_i,cis value. Rifampin also displayed preincubation time-dependent inhibition of OATP1B1, albeit the extent of enhancement was only 2-fold. The current study provides experimental evidence for the preincubation time-dependent shift of apparent K_i values and a mechanistic basis for physiologically based pharmacokinetic modeling that incorporates permeability clearance, extensive intracellular binding, and asymmetry of K_i values between the inside and outside of cells. Significance Statement In vitro data and kinetic modeling support that preincubation time-dependent, long-lasting inhibition of OATP1B1 by CsA can be explained by the extensive intracellular binding and reversible OATP1B1 inhibition intracellularly (trans-inhibition) as well as extracellularly (cis-inhibition). For inhibitors to display time-dependency, the following factors were found important: time to reach a steady-state cellular concentration, trans-inhibition potency relative to cis-inhibition, and the degree of cellular inhibitor accumulation. This study would aid in the accurate prediction of drug-drug interactions mediated by OATP1B1 inhibition.

Evaluation of Platinum Anticancer Drug-Induced Kidney Injury in Primary Culture of Rat Kidney Tissue Slices by Using Gas-Permeable Plates

The type of method adopted for the evaluation of drug-induced kidney injury (DIKI) plays an important role during the drug discovery process. In the present study, the usefulness of cultured rat kidney tissue slices maintained on gas-permeable poly(dimethylsiloxane) (PDMS) plates for DIKI was assessed by monitoring the ATP content as a marker of cell viability. The amount of ATP in the kidney slices cultured on the PDMS plates was higher than that in the slices cultured on gas-impermeable polystyrene plates. The protein expression of organic cation transporter-2 (Oct2) was maintained for 3 d. Cisplatin showed a time- and concentration-dependent reduction in ATP in the slices with a half-effective concentration value of 24 µM, which was alleviated by cimetidine, an Oct2 inhibitor, suggesting that cisplatin-induced kidney injury in the cultured slices was regulated by the basolateral uptake transporter Oct2. Furthermore, the intensity of platinum anticancer drug-induced nephrotoxicity in the cultured slices was consistent with that of the in vivo study. In conclusion, the primary culture of rat kidney tissue slices on gas-permeable plates is expected to aid in the prediction of the extent of nephrotoxicity of drugs, even when transporters are responsible for the accumulation of drugs in kidney tissues.

Tepotinib in patients with NSCLC harbouring MET exon 14 skipping: Japanese subset analysis from the Phase II VISION study

BACKGROUND

MET exon 14 skipping is an oncogenic driver occurring in 3-4% of non-small cell lung cancer (NSCLC). The MET inhibitor tepotinib has demonstrated clinical efficacy in patients with MET exon 14 skipping NSCLC. Here, we present data from Japanese patients in the Phase II VISION study, evaluating the efficacy and safety of tepotinib.

METHODS

In the open-label, single-arm, Phase II VISION study, patients with advanced/metastatic NSCLC with MET exon 14 skipping received oral tepotinib 500 mg once daily. The primary endpoint was objective response by independent review. Subgroup analyses of Japanese patients were preplanned.

RESULTS

As of 1 January 2020, 19 Japanese patients received tepotinib and were evaluated for safety, 15 of whom had ≥9 months' follow-up and were also analysed for efficacy. By independent review, objective response rate (ORR) was 60.0% (95% confidence interval [CI]: 32.3, 83.7), median duration of response was not reached (95% CI: 6.9, not estimable [ne]), and progression-free survival was 11.0 months (95% CI: 1.4, ne). ORR in patients with MET exon 14 skipping identified by liquid biopsy (n = 8) was 87.5% (95% CI: 47.3, 99.7), and by tissue biopsy (n = 12) was 50.0% (95% CI: 21.1, 78.9). Patients' quality of life was maintained with tepotinib treatment. Among patients evaluated for safety, the most common treatment-related adverse events (any grade) were blood creatinine increase and peripheral oedema (12 and nine patients, respectively).

CONCLUSIONS

Tepotinib demonstrated robust and durable clinical efficacy in Japanese patients with advanced NSCLC harbouring MET exon 14 skipping, identified by either liquid or tissue biopsy. The main adverse events, blood creatinine increase and peripheral oedema, were manageable.

Nephrotoxicity of cancer therapeutic drugs: Focusing on novel agents

Kidney injury caused by anticancer agents is a common problem that can interfere with and affect the dose intensity of anticancer therapy, thus restricting patient survival. Recent advances in targeted and immunotherapeutic agents have transformed the landscape of medical oncology, and these agents have been widely employed in clinical practice. While typically associated with favorable toxicity profiles, several novel anticancer drugs present distinctive nephrotoxicities. It remains urgent to closely monitor renal injuries associated with these agents, and medical practitioners should be familiar with general principles for managing nephrotoxicity associated with novel cancer drugs. This review provides an in-depth investigation of the literature and guidelines regarding the prevalence, clinical presentations, mechanisms, and management of nephrotoxicity for each drug.

Effects of SLC22A2 808G>T polymorphism and bosutinib concentrations on serum creatinine in patients with chronic myeloid leukemia receiving bosutinib therapy

The purpose of this study was to investigate the effects of SLC22A2 808G>T polymorphism and trough concentrations (C₀) of bosutinib on serum creatinine in 28 patients taking bosutinib. At 1, 3, 6, 12, 24, and 36 months after administration, analysis of bosutinib C₀ and creatinine was performed at the same time of day. Significant correlations were observed between bosutinib C₀ and the change rate of serum creatinine or the estimated glomerular filtration rate (eGFR; r = 0.328, P < 0.001 and r = − 0.315, P < 0.001, respectively). These correlations were particularly high in patients having the SLC22A2 808G/G genotype (r = 0.345 and r = − 0.329, respectively); however, in patients having the 808T allele, there were no significant differences. In multivariate analyses, the SLC22A2 808G/G genotype, patient age, bosutinib C₀ and second-line or later bosutinib were independent factors influencing the change rate of creatinine. Bosutinib elevated serum creatinine through organic cation transporter 2 (OCT2). We observed a 20% increase in serum creatinine with a median bosutinib C₀ of 63.4–73.2 ng/mL. Periodic measurement of serum creatinine after bosutinib therapy is necessary to avoid progression to severe renal dysfunction from simple elevation of creatinine mediated by OCT2 following bosutinib treatment.

Interactions of janus kinase inhibitors with drug transporters and consequences for pharmacokinetics and toxicity

Introduction: Janus kinase inhibitors (JAKinibs) constitute an emerging and promising pharmacological class of anti-inflammatory or anti-cancer drugs, used notably for the treatment of rheumatoid arthritis and some myeloproliferative neoplasms.Areas covered: This review provides an overview of the interactions between marketed JAKinibs and major uptake and efflux drug transporters. Consequences regarding pharmacokinetics, drug-drug interactions and toxicity are summarized.Expert opinion: JAKinibs interact in vitro with transporters in various ways, as inhibitors or as substrates of transporters or as regulators of transporter expression. This may theoretically result in drug-drug interactions (DDIs), with JAKinibs acting as perpetrators or as victims, or in toxicity, via impairment of thiamine transport. Clinical significance in terms of DDIs for JAKinib-transporter interactions remains however poorly documented. In this context, the in vivo unbound concentration of JAKinibs is likely a key parameter to consider for evaluating the clinical relevance of JAKinibs-mediated transporter inhibition. Additionally, the interplay with drug metabolism as well as possible interactions with transporters of emerging importance and time-dependent inhibition have to be taken into account. The role drug transporters may play in controlling cellular JAKinib concentrations and efficacy in target cells is also an issue of interest.

Repurposing Tyrosine Kinase Inhibitors to Overcome Multidrug Resistance in Cancer: A Focus on Transporters and Lysosomal Sequestration

Tyrosine kinase inhibitors (TKIs) are being increasingly used to treat various malignancies. Although they were designed to target aberrant tyrosine kinases, they are also intimately linked with the mechanisms of multidrug resistance (MDR) in cancer cells. MDR-related solute carrier (SLC) and ATB-binding cassette (ABC) transporters are responsible for TKI uptake and efflux, respectively. However, the role of TKIs appears to be dual because they can act as substrates and/or inhibitors of these transporters. In addition, several TKIs have been identified to be sequestered into lysosomes either due to their physiochemical properties or via ABC transporters expressed on the lysosomal membrane. Since the development of MDR represents a great concern in anticancer treatment, it is important to elucidate the interactions of TKIs with MDR-related transporters as well as to improve the properties that would prevent TKIs from diffusing into lysosomes. These findings not only help to avoid MDR, but also help to define the possible impact of combining TKIs with other anticancer drugs, leading to more efficient therapy and fewer adverse effects in patients.

Elucidation of N 1-methyladenosine as a Potential Surrogate Biomarker for Drug Interaction Studies Involving Renal Organic Cation Transporters

Endogenous substrates are emerging biomarkers for drug transporters, which serve as surrogate probes in drug-drug interaction (DDI) studies. In this study, the results of metabolome analysis using wild-type and Oct1/2 double knockout mice suggested that N ¹-methyladenosine (m¹A) was a novel organic cation transporter (OCT) 2 substrate. An in vitro transport study revealed that m¹A is a substrate of mouse Oct1, Oct2, Mate1, human OCT1, OCT2, and multidrug and toxin exclusion protein (MATE) 2-K, but not human MATE1. Urinary excretion accounted for 77% of the systemic elimination of m¹A in mice. The renal clearance (46.9 ± 4.9 ml/min per kilogram) of exogenously given m¹A was decreased to near the glomerular filtration rates by Oct1/2 double knockout or Mate1 inhibition by pyrimethamine (16.6 ± 2.6 and 24.3 ± 0.6 ml/min per kilogram, respectively), accompanied by significantly higher plasma concentrations. In vivo inhibition of OCT2/MATE2-K by a single dose of 7-[(3R)-3-(1-aminocyclopropyl)pyrrolidin-1-yl]-1-[(1R,2S)-2-fluorocyclopropyl]-8-methoxy-4-oxoquinoline-3-carboxylic acid in cynomolgus monkeys resulted in the elevation of the area under the curve of m¹A (1.72-fold) as well as metformin (2.18-fold). The plasma m¹A concentration profile showed low diurnal and interindividual variation in healthy volunteers. The renal clearance of m¹A in younger (21-45 year old) and older (65-79 year old) volunteers (244 ± 58 and 169 ± 22 ml/min per kilogram, respectively) was about 2-fold higher than the creatinine clearance. The renal clearances of m¹A and creatinine were 31% and 17% smaller in older than in younger volunteers. Thus, m¹A could be a surrogate probe for the evaluation of DDIs involving OCT2/MATE2-K. SIGNIFICANCE STATEMENT: Endogenous substrates can serve as surrogate probes for clinical drug-drug interaction studies involving drug transporters or enzymes. In this study, m¹A was found to be a novel substrate of renal cationic drug transporters OCT2 and MATE2-K. N ¹-methyladenosine was revealed to have some advantages compared to other OCT2/MATE substrates (creatinine and N ¹-methylnicotinamide). The genetic or chemical impairment of OCT2 or MATE2-K caused a significant increase in the plasma m¹A concentration in mice and cynomolgus monkeys due to the high contribution of tubular secretion to the net elimination of m¹A. The plasma m¹A concentration profile showed low diurnal and interindividual variation in healthy volunteers. Thus, m¹A could be a better biomarker of variations in OCT2/MATE2-K activity caused by inhibitory drugs.

Interaction between phytotherapy and oral anticancer agents: prospective study and literature review

Cancer is becoming more prevalent in elderly patient. Due to polypharmacy, older adults with cancer are predisposed to drug-drug interactions. There is also an increasing interest in the use of complementary and alternative medicine (CAM). Thirty to seventy percent of patients with cancer have used CAM. Through pharmaceutical counseling sessions, we can provide advices on herb-drug interactions (HDI). All the patients seen in pharmaceutical counseling sessions were prospectively included. Information was collected during these sessions: prescribed medication (oral anticancer agents (OAA) and other drugs), CAM (phytotherapy especially), and use of over-the-counter (OTC) drugs. If pharmacist considered an interaction or an intervention clinically relevant, the oncologist was notified. Then, a literature review was realized to identify the potential HDI (no interactions, precautions for use, contraindication). Among 201 pharmacist counseling sessions, it resulted in 104 interventions related to 46 HDI, 28 drug-drug interactions and 30 others (wrong dosage, omission…). To determine HDI, we review 73 medicinal plants which are used by our patients with cancer and 31 OAA. A total of 1829 recommendations were formulated about 59 (75%) medical plants and their interaction with an OAA. Herb-drug interactions should not be ignored by healthcare providers in their management of cancer patients in daily practice.

Effect of tyrosine kinase inhibitors on renal handling of creatinine by MATE1

Creatinine is actively secreted across tubular epithelial cells via organic cation transporter 2 (OCT2) and multidrug and toxin extrusion 1 (MATE1). We previously showed that the tyrosine kinase inhibitor (TKI) crizotinib inhibits OCT2-mediated transport of creatinine. In the present work, we examined the inhibitory potency of TKIs, including crizotinib, on MATE1-mediated transport of creatinine. Then, we used the kinetic parameters estimated in this and the previous work to predict the potential impact of TKIs on serum creatinine level (SCr) via reversible inhibition of creatinine transport. Crizotinib inhibited [¹⁴C]creatinine uptake by MATE1-overexpressing cells, and the inhibitory effect increased with incubation time, being greater in the case of pre-incubation or combined pre-incubation/co-incubation (pre/co-incubation) than in the case of co-incubation alone. The inhibition was non-competitive, with K _i values of 2.34 μM, 0.455 μM and 0.342 μM under co-, pre- or pre/co-incubation conditions, respectively. Similar values were obtained for inhibition of [³H]MPP⁺ uptake by MATE1-overexpressing cells. Gefitinib, imatinib, pazopanib, sorafenib, and sunitinib also inhibited MATE1-mediated creatinine uptake. Further, all these TKIs except pazopanib inhibited [¹⁴C]creatinine uptake by OCT2-overexpressing cells. In rat kidney slices, the ratio of unbound tissue accumulation of TKIs to extracellular concentration ranged from 2.05 to 3.93. Prediction of the influence of TKIs on SCr based on the renal creatinine clearance and plasma maximum unbound concentrations of TKIs suggested that crizotinib and imatinib might increase SCr by more than 10% in the clinical context. Accordingly, it is necessary to be cautious in diagnosing TKI-induced renal failure only on the basis of an increase of SCr.

Ceritinib compassionate use for patients with crizotinib-refractory, anaplastic lymphoma kinase-positive advanced non-small-cell lung cancer

Aim: Ceritinib was evaluated within a compassionate use program of Italian patients. Patients & methods: 70 patients with anaplastic lymphoma kinase-positive crizotinib-refractory advanced non-small-cell lung cancer received ceritinib. Results: Overall response was 40.6%, median progression-free survival was 8.2 months and median survival was 15.5 months. Dose reduction due to treatment-related adverse events occurred in 50.8% of patients starting at 750 mg/day. No significantly different progression-free survival was observed between patients who underwent any time dose reduction (n = 38) versus those who remained on the recommended dose of 750 mg/day (n = 32; p = 0.07). Conclusion: The efficacy of ceritinib compassionate use program resembled that of clinical trials. Dose reductions and adjustments did not appear to negatively affect clinical outcome.