Pharmacology of Tyrosine Kinase Inhibitors: Implications for Patients with Kidney Diseases

Tyrosine kinase inhibitors (TKI) have introduced a significant advancement in cancer management. These compounds are administered orally, and their absorption holds a pivotal role in determining their variable efficacy. They exhibit extensive distribution within the body, binding strongly to both plasma and tissue proteins. Often reliant on efflux and influx transporters, TKI undergo primary metabolism by intestinal and hepatic cytochrome P450 enzymes, with nonkidney clearance being predominant. Owing to their limited therapeutic window, many TKI display considerable intraindividual and interindividual variability. This review offers a comprehensive analysis of the clinical pharmacokinetics of TKI, detailing their interactions with drug transporters and metabolic enzymes, while discussing potential clinical implications. The prevalence of kidney conditions, such as AKI and CKD, among patients with cancer is explored in their effect on TKI pharmacokinetics. Finally, the potential nephrotoxicity associated with TKI is also examined.

Tyrosine Kinase Inhibitors-Induced Arrhythmias: From Molecular Mechanisms, Pharmacokinetics to Therapeutic Strategies

With the development of anti-tumor drugs, tyrosine kinase inhibitors (TKIs) are an indispensable part of targeted therapy. They can be superior to traditional chemotherapeutic drugs in selectivity, safety, and efficacy. However, they have been found to be associated with serious adverse effects in use, such as myocardial infarction, fluid retention, hypertension, and rash. Although TKIs induced arrhythmia with a lower incidence than other cardiovascular diseases, much clinical evidence indicated that adequate attention and management should be provided to patients. This review focuses on QT interval prolongation and atrial fibrillation (AF) which are conveniently monitored in clinical practice. We collected data about TKIs, and analyzed the molecule mechanism, discussed the actual clinical evidence and drug-drug interaction, and provided countermeasures to QT interval prolongation and AF. We also pooled data to show that both QT prolongation and AF are related to their multi-target effects. Furthermore, more than 30 TKIs were approved by the FDA, but most of the novel drugs had a small sample size in the preclinical trial and risk/benefit assessments were not perfect, which led to a suspension after listing, like nilotinib. Similarly, vandetanib exhibits the most significant QT prolongation and ibrutinib exhibits the highest incidence in AF, but does not receive enough attention during treatment.

Decreased Disposition of Anticancer Drugs Predominantly Eliminated via the Liver in Patients with Renal Failure

Background:

Evidence has revealed that renal impairment can affect the systemic exposure of drugs which are predominantly eliminated via the liver. The modulation of drug-metabolizing enzymes and transporters expressed in the liver and/or small intestine by diverse entities, including uremic toxins, in systemic circulation of patients with severe renal failure is considered as the cause of atypical pharmacokinetics, which sometimes induce undesirable adverse events that are especially critical for drugs with narrow therapeutic window such as anticancer drugs. A dosing strategy for anticancer drugs in these patients needs to be established.

Methods:

The effects of renal impairment on the systemic exposure and safety of anticancer drugs were summarized. The proposed mechanisms for the alterations in the pharmacokinetics of these anticancer drugs were also discussed.

Results:

Changes in pharmacokinetics and clinical response were reported in 9 out of 10 cytotoxic anticancer drugs investigated, although available information was limited and sometimes controversial. Systemic exposure of 3 out of 16 tyrosine kinase inhibitors was higher in patients with severe renal failure than that in patients with normal kidney function. An increase in systemic exposure of anticancer drugs in patients with renal impairment is likely to be observed for substrates of OATP1B1, despite the limited evidence.

Conclusion:

The molecular basis for the effect of uremia on non-renal drug elimination still needed to be clarified with further studies to generate generalizable concepts, which may provide insights into establishing better clinical usage of anticancer drugs, i.e. identifying patients at risk and dose adjustment.

Recent advances in the biology and therapy of medullary thyroid carcinoma

Medullary thyroid cancer (MTC) is a relatively uncommon yet prognostically significant thyroid cancer. Several recent advances in the biology and current or potential treatment of MTC are notable. These include a new understanding of the developmental biology of the thyroid C cell, which heretofore was thought to develop from the neural crest. RET, encoded by the most common driver gene in MTC, has been shown to be a dual function kinase, thus expanding its potential substrate repertoire. Promising new therapeutic developments are occurring; many have recently progressed to clinical development. There are new insights into RET inhibitor therapy for MTC. New strategies are being developed to inhibit the RAS proteins, which are potential therapeutic targets in MTC. Potential emerging immunotherapies for MTC are discussed. However, gaps in our knowledge of the basic biology of the C cell, its transformation to MTC, and the mechanisms of resistance to therapy impede progress; further research in these areas would have a substantial impact on the field.

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

Crizotinib, a tyrosine kinase inhibitor, exhibits some cases of an increase in serum creatinine levels. Creatinine is excreted by not only glomerular filtration but also active secretion by organic cation transporters such as organic cation transporter 2 (OCT2). In the present study, we evaluated in vitro inhibitory effect of crizotinib on OCT2 by directly measuring creatinine uptake by OCT2. Coincubation of crizotinib reduced uptake of [¹⁴C]creatinine by cultured HEK293 cells expressing OCT2 (HEK293/OCT2) in a concentration-dependent manner with IC₅₀ values of 1.58 ± 0.24 μM. Preincubation or both preincubation and coincubation (preincubation/coincubation) with crizotinib showed stronger inhibitory effect on [¹⁴C]creatinine uptake compared with that in coincubation alone with IC₅₀ values of 0.499 ± 0.076 and 0.347 ± 0.040 μM, respectively. These IC₅₀ values of crizotinib on [³H]N-methyl-4-phenylpyridinium acetate uptake by OCT2 were 10-20 times higher than those of [¹⁴C]creatinine uptake. Furthermore, preincubation of crizotinib inhibited creatinine uptake by OCT2 in an apparently competitive manner. In conclusion, crizotinib at a clinically relevant concentration has the potential to inhibit creatinine transport by OCT2, suggesting an increase of serum creatinine levels in clinical use.

Pharmacokinetic/pharmacodynamic considerations for cancer patients undergoing hemodialysis

INTRODUCTION

The increased incidence of cancer in hemodialysis patients has been discussed since the mid-70s. Today, physicians regularly encounter situations where they must manage the prescription of anticancer drugs in hemodialysis patients. Areas covered: Hemodialysis patients are at risk of dose-related toxicities due to pharmacokinetic modifications. Hemodialysis patients are at risk of therapeutic drug removal during their hemodialysis session, which may result in a loss of efficacy. In the advent of novel immunotherapies, particularly tumor vaccines, there is an increased theoretical risk of pharmacodynamic modification. Indeed, pharmacodynamic modifications have already been reported for viral vaccines. Expert opinion: It is important to consider all of the potential pharmacokinetic/pharmacodynamic modifications before prescribing anticancer drugs in hemodialysis patients. However, pharmacokinetic/pharmacodynamic modification should not be considered a contraindication for anticancer drug use in hemodialysis patients, rather, clinicians should be aware of the need individualize treatment according to available recommendations.

Effect of Renal and Hepatic Impairment on the Pharmacokinetics of Cabozantinib

Cabozantinib is a tyrosine kinase inhibitor approved for the treatment of patients with progressive, metastatic medullary thyroid cancer. Two clinical pharmacology studies were conducted to characterize single-dose pharmacokinetics (PK) of cabozantinib in renally or hepatically impaired subjects. Study 1 enrolled 10 subjects, each with mild or moderate impairment of renal function; 12 healthy subjects were matched to the moderate group for age, sex, and body mass index (BMI). Study 2 enrolled 8 males each with mild or moderate hepatic impairment; 10 healthy males were matched to the moderate group for age, BMI, and ethnicity. All subjects received one 60 mg cabozantinib oral capsule dose followed by PK sampling over 21 days. Plasma concentration and protein binding were determined by liquid chromatography tandem mass spectrometry and equilibrium dialysis, respectively. PK parameters were computed using noncompartmental methods. Geometric least squared mean (LSM) ratios for plasma cabozantinib AUC0-∞ for impaired to normal organ function cohorts were (1) approximately 30% and 6% higher in subjects with mild and moderate renal impairment, respectively, and (2) approximately 81% and 63% higher in subjects with mild and moderate hepatic impairment, respectively. The percentage of unbound drug was slightly higher in both moderately impaired cohorts. No deaths or discontinuations due to adverse events occurred in either study. Cabozantinib should be used with caution in subjects with mild or moderate renal impairment. Subjects with mild or moderate hepatic impairment administered cabozantinib should be monitored closely for potential treatment-emergent drug toxicity that may necessitate a dose hold or reduction.

Pharmacokinetic evaluations of the co-administrations of vandetanib and metformin, digoxin, midazolam, omeprazole or ranitidine

BACKGROUND AND OBJECTIVE

Vandetanib is a selective inhibitor of vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR) and rearranged during transfection (RET) signalling, indicated for the treatment of medullary thyroid cancer. We investigated potential drug-drug interactions between vandetanib and metformin [organic cation transporter 2 (OCT2) substrate; NCT01551615]; digoxin [P-glycoprotein (P-gp) substrate; NCT01561781]; midazolam [cytochrome P450 (CYP) 3A4 substrate; NCT01544140]; omeprazole (proton pump inhibitor) or ranitidine (histamine H2-receptor antagonist; both NCT01539655).

METHODS

Four open-label, phase I studies were conducted in healthy volunteers: n = 14 (metformin), n = 14 (digoxin), n = 17 (midazolam), n = 16 (omeprazole), n = 18 (ranitidine). Three of these comprised the following regimens: metformin 1000 mg ± vandetanib 800 mg, midazolam 7.5 mg ± vandetanib 800 mg, or digoxin 0.25 mg ± vandetanib 300 mg. The randomized study comprised vandetanib 300 mg alone and then either (i) omeprazole 40 mg (days 1-4), and omeprazole + vandetanib (day 5); or (ii) ranitidine 150 mg (day 1), and ranitidine + vandetanib (day 2). The primary objective assessed metformin, digoxin, midazolam and vandetanib pharmacokinetics.

RESULTS

Vandetanib + metformin increased metformin area under the plasma concentration-time curve from zero to infinity (AUC0-∞) and maximum observed plasma concentration (Cmax) by 74 and 50 %, respectively, and decreased the geometric mean metformin renal clearance (CLR) by 52 % versus metformin alone. Vandetanib + digoxin increased digoxin area under the concentration-time curve from zero to the last quantifiable concentration (AUC0-last) and Cmax by 23 and 29 %, respectively, versus digoxin alone, with only a 9 % decrease in CLR. Vandetanib had no effect on midazolam exposure. Vandetanib exposure was unchanged during co-administration with omeprazole/ranitidine. Treatment combinations were generally well tolerated.

CONCLUSION

Patients receiving vandetanib with metformin/digoxin may require additional monitoring of metformin/digoxin, with dose adjustments where necessary. Vandetanib with CYP3A4 substrates or omeprazole/ranitidine is unlikely to result in clinically relevant drug-drug interactions.

Anticancer Drugs in End-Stage Kidney Disease Patients

The increased incidence of malignancies in patients with chronic kidney patients and especially in end-stage kidney disease (ESKD) patients has been discussed since the mid-1970s. Consequently, oncologists, nephrologists, and pharmacists are increasingly facing challenging situations of cytotoxic drug handling in dialysis patients because of pharmacokinetic modifications. In these patients, two main issues must be considered. First, the absence of renal function in hemodialysis (HD) patients may necessitate drug dosage reduction. Therefore, drug prescription must be cautiously checked before administration with appropriate dosage adjustment whenever necessary to ensure efficacy while avoiding overdosage and related side effects. Second, drug clearance by dialysis session must be taken into account for appropriate chemotherapy timing administration to avoid drug removal, which may result in a loss of efficacy. These two main considerations must not be considered as a contra-indication to chemotherapy in ESKD patients, but more as a need for an individualized prescription according to available recommendations.

Renal effects of targeted anticancer therapies

The use of novel targeted anticancer agents has led to overall improvement in the prognosis of many patients affected by various malignancies, but has also been associated with an increased risk of poorly characterized toxic effects to different organs, including the kidneys. The high prevalence of kidney impairment in the general population complicates the issue further. Nephrologists most frequently work with patients with cancer when they are asked to investigate kidney function to assess the need for dose adjustments in anticancer therapy. A thorough knowledge of the renal safety profile of novel life-prolonging anticancer therapies, specific features of their metabolism, and pharmacokinetic and pharmacodynamic properties (under normal circumstances as well as in the setting of renal replacement therapy) is, therefore, necessary to preserve kidney function as far as possible and to ensure optimum treatment. In this Review we summarize the present knowledge of renal toxic effects from novel targeted anticancer agents and discuss whether the management of patients' treatment needs to be modified. We also advocate the development of a new onconephrology subspeciality.

Drug disposition alterations in liver disease: extrahepatic effects in cholestasis and nonalcoholic steatohepatitis

INTRODUCTION

The pharmacokinetics (PK) of drugs and xenobiotics, namely pharmaceuticals, is influenced by a host of factors that include genetics, physiological factors and environmental stressors. The importance of disease on the disposition of xenobiotics has been increasingly recognized among medical professionals for alterations in key enzymes and membrane transporters that influence drug disposition and contribute to the development of adverse drug reactions.

AREAS COVERED

This review will survey pertinent literature of how liver disease alters the PKs of drugs and other xenobiotics. The focus will be on nonalcoholic steatohepatitis as well as cholestatic liver diseases. A review of basic pharmacokinetic principles, with a special emphasis on xenobiotic metabolizing enzymes and membrane transporters, will be provided. Specifically, examples of how genetic alterations affect metabolism and excretion, respectively, will be highlighted. Lastly, the idea of 'extrahepatic' regulation will be explored, citing examples of how disease manifestation in the liver may affect drug disposition in distal sites, such as the kidney.

EXPERT OPINION

An expert opinion will be provided highlighting the definite need for data in understanding extrahepatic regulation of membrane transporters in the presence of liver disease and its potential to dramatically alter the PK and toxicokinetic profile of numerous drugs and xenobiotics.

Clinical pharmacokinetics of tyrosine kinase inhibitors: implications for therapeutic drug monitoring

The treatment of many malignancies has been improved in recent years by the introduction of molecular targeted therapies. These drugs interact preferentially with specific targets that are mutated and/or overexpressed in malignant cells. A group of such targets are the tyrosine kinases, against which a number of inhibitors (tyrosine kinase inhibitors, TKIs) have been developed. Imatinib, a TKI with targets that include the breakpoint cluster region-Abelson (bcr-abl) fusion protein kinase and mast/stem cell growth factor receptor kinase (c-Kit), was the first clinically successful drug of this type and revolutionized the treatment and prognosis of chronic myeloid leukemia and gastrointestinal stromal tumors. This success paved the way for the development of other TKIs for the treatment of a range of hematological malignancies and solid tumors. To date, 14 TKIs have been approved for clinical use and many more are under investigation. All these agents are given orally and are substrates of a range of drug transporters and metabolizing enzymes. In addition, some TKIs are capable of inhibiting their own transporters and metabolizing enzymes, making their disposition and metabolism at steady-state unpredictable. A given dose can therefore give rise to markedly different plasma concentrations in different patients, favoring the selection of resistant clones in the case of subtherapeutic exposure, and increasing the risk of toxicity if dosage is excessive. The aim of this review was to summarize current knowledge of the clinical pharmacokinetics and known adverse effects of the TKIs that are available for clinical use and to provide practical guidance on the implications of these data in patient management, in particular with respect to therapeutic drug monitoring.

Vandetanib for the Treatment of Medullary Thyroid Carcinoma

Objective: To review the place in therapy of vandetanib for medullary thyroid carcinoma (MTC). Data Sources: Literature searches were performed in Ovid MEDLINE, EMBASE, and Google Scholar using the search terms ZD6474 OR vandetanib OR Caprelsa combined with medullary thyroid carcinoma. Study Selection and Data Extraction: Two phase 2 trials and 1 phase 3 trial were identified. Data Synthesis: Vandetanib is approved for the treatment of unresectable, locally advanced or metastatic MTC in patients with symptomatic or progressive disease. In the phase 3 randomized, double-blind, placebo-controlled trial, vandetanib 300 mg daily (n = 231) was compared with placebo (n = 100). Vandetanib-treated patients experienced a significant improvement in progression-free survival (PFS; hazard ratio [HR] = 0.46; 95% CI = 0.31-0.69; P < .001). No difference in overall survival (OS) was seen at the time of publication. Most adverse effects were grade 1 or 2 and managed by dose interruptions or reductions. The most common grade 3/4 adverse effects were diarrhea, hypertension, QT prolongation, fatigue, and rash. Because of the potential for QT prolongation, torsades de pointes, and sudden death, vandetanib is restricted via a Risk Evaluations and Mitigation Strategy program. Conclusions: Vandetanib prolongs PFS but has not been shown to improve OS. Vandetanib can be considered for patients with unresectable locoregional disease. It is a first-line option for patients with unresectable symptomatic distant metastases as well as an option for advanced disseminated symptomatic metastatic disease. Vandetanib is expected to be an important addition to the formulary of health plans that provide prescription drug benefits.

Efficacy and tolerability of pharmacotherapy options for the treatment of medullary thyroid cancer

Metastatic and unresectable medullary thyroid carcinoma (MTC) is often difficult to treat as it is relatively unresponsive to radiation and conventional chemotherapy. This emphasizes the importance of the development of targeted therapies for advanced MTC. Vandetanib was approved by the US Food and Drug Administration for the treatment of symptomatic or progressive MTC in patients with advanced disease in April 2011. This therapy proved to be a breakthrough in the management of MTC. We review the efficacy and safety of this novel treatment and other treatments that are being evaluated in this disease.

Vandetanib for the treatment of metastatic medullary thyroid cancer

Medullary thyroid cancer (MTC) represents an aggressive form of thyroid malignancy. Some may occur spontaneously or can be associated with Multiple Endocrine Neoplasia syndromes, or Familial Medullary Thyroid Cancer syndrome. In these patients, the protooncogene RET (rearranged during transfection) is mutated. In patients who have unresectable or metastatic disease, the long term prognosis is poor. New treatments for this disease have focused on the use of targeted agents that inhibit the receptor tyrosine kinase of RET. One of these treatments, Vandetanib (Caprelsa, Astra Zeneca), recently has received approval from the Food and Drug Administration for the treatment of patients with progressive locally advanced and/or metastatic disease. This review highlights the studies that led to the drug's approval, and discusses on the potential financial costs of treatment and side effects of this therapy. The main clinical studies evaluating Vandetanib for the treatment of other solid tumors will also be reviewed.

Pharmacokinetics of the novel PAR-1 antagonist vorapaxar in patients with hepatic impairment

PURPOSE

To determine whether hepatic impairment has an effect on the pharmacokinetics (PK) of vorapaxar or M20, its main pharmacologically active metabolite.

METHODS

This was an open-label study in which a single 40-mg oral dose of vorapaxar was administered to patients with mild (n = 6), moderate (n = 6), and severe (n = 4) hepatic impairment and healthy controls (n = 16) matched for age, gender, weight, and height. Blood samples for vorapaxar and M20 assay were collected predose and at frequent intervals up to 8 weeks postdose.

RESULTS

Plasma vorapaxar and M20 PK profiles were similar between patients with impaired liver function and healthy controls. Group mean values for vorapaxar C(max) and AUC(tf) were 206-279 ng/mL and 14,200-18,200 ng·h/mL, respectively, with the lowest values observed in patients with severe impairment. Vorapaxar median T(max) and mean t(1/2) values were 1.00-1.75 h and 298-366 h, respectively. There was no apparent correlation between vorapaxar or M20 exposure or t(1/2) values and disease severity. Vorapaxar was generally well tolerated; one serious adverse event (gastrointestinal bleeding secondary to ruptured esophageal varices) was reported in a patient with severe hepatic impairment.

CONCLUSIONS

Hepatic impairment had no clinically relevant effect on the PK of vorapaxar and M20. No dose or dosage adjustment of vorapaxar will be required in patients with mild to moderate hepatic impairment. Although systemic exposure to vorapaxar does not appear to increase in patients with severe hepatic impairment, administration of vorapaxar to such patients is not recommended given their bleeding diathesis.