Pharmacokinetics of Prenylflavonoids following Oral Ingestion of Standardized Epimedium Extract in Humans.

Leaves of the Epimedium plant are traditionally consumed for bone health and other indications. The aim of this study was to establish the safety and pharmacokinetics of the metabolites of prenylflavonoids (icariin, icariside I, icariside II, icaritin, and desmethylicaritin) following single doses of a defined Epimedium prenylflavonoid extract in humans. A single oral dose of 370, 740, or 1110 mg of a standardized Epimedium prenylflavonoid extract was administered to 30 healthy male subjects in a randomized, placebo-controlled trial. Serum samples were collected over a 48-h period and analyzed by liquid chromatography-tandem mass spectrometry and non-compartmental pharmacokinetic modelling. Epimedium prenylflavonoid extracts were well tolerated and no adverse effects were observed. The principle metabolites detected in the serum were icariside II and desmethylicaritin. Icariside II had a T max of between 4.1 - 4.3 h, reaching a maximum AUC0→∞ of 23.0 (17.5, 29.9) h×ng/mL (median [IQR: interquartile range]) with the highest dose of the Epimedium prenylflavonoid. On the other hand, desmethylicaritin had a delayed T max of 24.1 - 24.4 h and reached a maximum AUC0→∞ of 126.1 (62.4, 202.9) h×ng/mL. The median maximum plasma concentration and AUC0→∞ of desmethyliciaritin showed an increase with higher doses of the Epimedium prenylflavonoid (p < 0.05). Icariin, icariside I, and icaritin levels were below detection limits. Levels of Epimedium prenylflavonoid metabolites observed in this study were consistent with levels demonstrated to have anti-osteoporotic effects in cellular and animal studies. Coupled with the favorable safety profile of the extract observed, further studies are required to explore the utility of Epimedium prenylflavonoid extracts to prevent osteoporosis in postmenopausal women.

BSA and ABCB1 polymorphism affect the pharmacokinetics of sunitinib and its active metabolite in Asian mRCC patients receiving an attenuated sunitinib dosing regimen.

PURPOSE: An attenuated dosing (AD) sunitinib regimen of 37.5 mg daily has been suggested to reduce the toxicity reported with the standard dosing regimen to metastatic renal cell carcinoma (mRCC) patients. The aim of this study was to characterize the population pharmacokinetic (PK) properties of sunitinib and SU12662, the active metabolite, in patients receiving the AD regimen and to ascertain significant covariates influencing PK parameters. METHODS: Thirty-one mRCC patients receiving AD sunitinib regimen were included. Plasma samples were collected on day 29 of each treatment cycle after the start of the therapy. Nonlinear mixed-effects modeling was applied to estimate the population PK properties of sunitinib and SU12662 as well as the effect of covariates on PK parameters. Monte Carlo simulation was also performed to predict the total trough level (TTL) of sunitinib and SU12662. RESULTS: Sunitinib population means for CL/F and V d /F central were 13.8 L/h and 1720 L, respectively. SU12662 population means for CL/F and V d /F were 42.1 L/h and 1410 L, respectively. Body surface area (BSA) and ABCB1 polymorphism significantly influenced the CL/F variability of sunitinib: CL/F parent = 13.8 × exp((BSA - 1.75) × 2.08 + (ABCB1 genotype - 0.67) × 0.61), ABCB1-0: wild genotype, 1: mutant genotype. The effect size of ABCB1 mutant genotype and BSA greater than 1.75 m(2) in relation to sunitinib clearance was 31.14 % (p = 0.006) and 22.11 % (p = 0.011), respectively, relative to the reference group. CONCLUSIONS: Adjusting doses of sunitinib according to BSA and ABCB1 polymorphism in Asian mRCC patients may be recommended for sufficient attainment of a target TTL of sunitinib and its metabolite.

A systematic review of patient-reported outcome instruments of dermatologic adverse events associated with targeted cancer therapies.

PURPOSE: Dermatologic adverse events (dAEs) in cancer treatment are frequent with the use of targeted therapies. These dAEs have been shown to have significant impact on health-related quality of life (HRQoL). While standardized assessment tools have been developed for physicians to assess severity of dAEs, there is a discord between objective and subjective measures. The identification of patient-reported outcome (PRO) instruments useful in the context of targeted cancer therapies is therefore important in both the clinical and research settings for the overall evaluation of dAEs and their impact on HRQoL. METHODS: A comprehensive, systematic literature search of published articles was conducted by two independent reviewers in order to identify PRO instruments previously utilized in patient populations with dAEs from targeted cancer therapies. The identified PRO instruments were studied to determine which HRQoL issues relevant to dAEs were addressed, as well as the process of development and validation of these instruments. RESULTS: Thirteen articles identifying six PRO instruments met the inclusion criteria. Four instruments were general dermatology (Skindex-16©, Skindex-29©, Dermatology Life Quality Index (DLQI), and DIELH-24) and two were symptom-specific (functional assessment of cancer therapy-epidermal growth factor receptor inhibitor-18 (FACT-EGFRI-18) and hand-foot syndrome 14 (HFS-14)). CONCLUSIONS: While there are several PRO instruments that have been tested in the context of targeted cancer therapy, additional work is needed to develop new instruments and to further validate the instruments identified in this study in patients receiving targeted therapies.

Association of drug exposure with toxicity and clinical response in metastatic renal cell carcinoma patients receiving an attenuated dosing regimen of sunitinib.

An attenuated dosing (AD) regimen of 37.5 mg daily in repeated 4 week on, 2 week off cycles has been proposed to ameliorate frequent dose modifications caused by the toxicity observed with the approved dosing regimen of sunitinib for metastatic renal cell carcinoma (mRCC). This study aimed to determine the effect of drug exposure on toxicity and clinical response in patients receiving this regimen. All mRCC patients receiving AD sunitinib were invited to participate. In week 4 of each cycle, toxicity and plasma levels were assessed. Clinical responses were assessed after two cycles. A total of 36 patients were recruited. Patients who manifested ≥grade 2 mucositis (126.46 vs 84.81 ng/mL, p = 0.04) and altered taste (159.91 vs 105.22 ng/mL, p = 0.05) had higher total exposure than those who had grade 1 or no toxicity. Twenty-six patients completed two treatment cycles; four (15%) had partial responses, 15 (58%) had a stable disease and 7 (27%) had progressive disease. No difference in the exposure levels was found among the patients with different clinical outcomes. The AD regimen of sunitinib in Asian mRCC patients provided sufficient drug exposure with a lower incidence of toxicity, with higher drug exposure being observed in patients who experienced toxicity.

Formation of reactive metabolites and management of tyrosine kinase inhibitor-induced hepatotoxicity: a literature review.

INTRODUCTION: Existing clinical evidence indicates that many tyrosine kinase inhibitors (TKIs) are associated with idiosyncratic hepatotoxicity. TKIs possess risk factors for developing drug-induced liver injury such as their high daily dose, being substrates of P450 enzyme and being involved in significant hepatic metabolism. Several successful strategies to overcome TKI-induced hepatotoxicity include: switching to an alternative TKI with a similar mechanism of action, using an alternative dose and introduction of corticosteroids for treatment and prevention of hepatotoxicity. AREAS COVERED: This review highlights the formation of reactive metabolites and how this leads to toxicity, as well as the current clinical management of TKI-induced hepatotoxicity. EXPERT OPINION: Numerous events need to occur in an individual patient before converging into an idiosyncratic hepatotoxicity episode. Of these, the formation of a reactive intermediate through metabolism appears to be the prerequisite. This critical event involves an intricate chemico-biological interaction where, on one hand, drug-specific characteristics create the propensity for occurrence and, on the other hand, patient risk factors determine the individuality of response. With improved understanding of the mechanisms leading to adverse events, several strategies are being adopted to prevent and treat TKI-induced hepatotoxicity. However, further evidence is required before they can be recommended to larger populations.

Metabolism-related pharmacokinetic drug-drug interactions with tyrosine kinase inhibitors: current understanding, challenges and recommendations.

Drug-drug interactions (DDIs) occur when a patient's response to the drug is modified by administration or co-exposure to another drug. The main cytochrome P450 (CYP) enzyme, CYP3A4, is implicated in the metabolism of almost all of the tyrosine kinase inhibitors (TKIs). Therefore, there is a substantial potential for interaction between TKIs and other drugs that modulate the activity of this metabolic pathway. Cancer patients are susceptible to DDIs as they receive many medications, either for supportive care or for treatment of toxicity. Differences in DDI outcomes are generally negligible because of the wide therapeutic window of common drugs. However for anticancer agents, serious clinical consequences may occur from small changes in drug metabolism and pharmacokinetics. Therefore, the objective of this review is to highlight the current understanding of DDIs among TKIs, with a focus on metabolism, as well as to identify challenges in the prediction of DDIs and provide recommendations.

Molecular profiling reveals a tumor-promoting phenotype of monocytes and macrophages in human cancer progression.

Monocytes and macrophages are major components of the tumor microenvironment, but their contributions to human cancer are poorly understood. We used molecular profiling combined with functional assays to investigate the role of these cells in human renal cell carcinoma (RCC). Blood monocytes from RCC patients displayed a tumor-promoting transcriptional profile that supported functions like angiogenesis and invasion. Induction of this protumor phenotype required an interleukin-1 receptor (IL-1R)-dependent mechanism. Indeed, targeting of IL-1-IL-1R axis in a human RCC xenograft model abrogated the protumor phenotype of tumor-associated macrophages (TAMs) and reduced tumor growth in vivo. Supporting this, meta-analysis of gene expression from human RCC tumors showed IL1B expression to correlate with myelomonocytic markers, protumor genes, and tumor staging. Analyzing RCC patient tumors confirmed the protumor phenotype of TAMs. These data provide direct evidence for a tumor-promoting role of monocytes and macrophages in human cancer and indicate IL-1-IL-1R as a possible therapeutic target.

Role of sunitinib and SU12662 on dermatological toxicities in metastatic renal cell carcinoma patients: in vitro, in vivo, and outcomes investigation.

PURPOSE: Sunitinib commonly exhibits dose-limiting dermatological toxicities (DTs) that adversely affect health-related quality of life (HRQoL). Pharmacological activity of sunitinib is attributed to sunitinib and an equipotent, active metabolite, SU12662. The objective of this study is to compare the dermatotoxic potential of sunitinib and SU12662, and changes in HRQoL due to DTs. METHODS: A prospective cohort study was conducted on metastatic renal cell carcinoma patients. Plasma drug concentrations were determined by high-performance liquid chromatography. DTs were graded by Common Terminology Criteria for Adverse Events. HRQoL of patients with hand-foot skin reaction (HFSR) was assessed by the hand-foot syndrome-specific quality-of-life questionnaire (HFS-14). In addition, the IC50s of both compounds were determined with HaCaT keratinocytes. RESULTS: Sunitinib was more dermatotoxic in vitro, with a lower IC50 than SU12662 (23.33 vs. 35.32 µM, p = 0.02). Similar results were observed in vivo, with higher sunitinib-to-SU12662 ratio in patients with pruritus, than patients without pruritus (p = 0.04). Higher HFS-14 scores were observed in patients with higher HFSR grade and in those with both hands and feet affected, indicating poorer HRQoL. CONCLUSIONS: Sunitinib may be more dermatotoxic than SU12662 from both in vivo and in vitro evidences. Therefore, appropriate management of DTs may be essential, especially in patients with a reduced sunitinib metabolising ability.

Risk of tyrosine kinase inhibitors-induced hepatotoxicity in cancer patients: a meta-analysis.

INTRODUCTION: Although existing evidence from clinical trials has demonstrated manifestation of hepatic adverse events (AEs) with the use of tyrosine kinase inhibitors (TKIs), overall risks have yet to be reported. Thus we conducted a meta-analysis to determine the risk of hepatotoxicity associated with the use of TKIs, by comparing the occurrence of hepatotoxicity of the TKI arms against that of comparison arms. METHODS: A comprehensive literature search of randomized control trials involving TKIs was performed. Only randomized, double-blind and placebo-controlled phase 2 or phase 3 human trials were included. The included studies must involve the comparison of a TKI against placebo, or the comparison of TKI with chemotherapy agent against placebo with the same chemotherapy agent. RESULTS: Twelve articles were included in the analysis. There was a significant overall increase in the odds of developing high-grade (grade 3 or above) hepatotoxicity with the use of TKIs compared to the control arms (Pooled OR 4.35, 95% CI 2.96-6.39). The odds of developing all-types all-grades (Pooled OR 2.42, 95% CI 1.52-3.85) and high-grade hepatotoxicity due to elevation in alanine transaminase (Pooled OR 5.22, 95% CI 2.88-9.46), aspartate transaminase (Pooled OR 6.15, 95% CI 3.09-12.25) and total bilirubin (Pooled OR 1.76, 95% CI 0.59-5.24) was higher with the use of TKI than compared to the controls. DISCUSSION: This is the first meta-analysis to demonstrate a significantly increased risk of hepatic AEs associated with TKIs use. Clinicians should be aware of this risk and provide close monitoring in patients receiving these therapies.

Effect of CYP3A4 inducer dexamethasone on hepatotoxicity of lapatinib: clinical and in vitro evidence.

Concomitant usage of lapatinib, a cytochrome P450 (CYP) 3A4 substrate and dexamethasone, a CYP3A4 inducer, is a pharmacokinetic drug-drug interaction. This combination may increase the formation of reactive lapatinib metabolites, which is potentially hepatotoxic. This study aims to evaluate the clinical effect of dexamethasone on incidence of hepatotoxicity and to ascertain its in vitro role using a parallel cell culture model experimental setup. Clinical effects of dexamethasone on lapatinib-induced hepatotoxicity were evaluated in a nested case-control study based on 120 patient data obtained from our records. For the in vitro experiment, metabolically competent transforming growth factor α mouse hepatocytes (TAMH) were treated with lapatinib and viabilities were compared in the presence or absence of dexamethasone. After adjusting for confounders, patients receiving the combination were 4.57 times (95% CI 1.23-16.88, p = 0.02) more likely to develop hepatotoxicity and 3.48 times (95% CI 1.24-9.80, p = 0.02) more likely to develop a clinically important change in alanine aminotransferase than compared to the other group. Treatment of TAMH cells with lapatinib and dexamethasone caused a further reduction in viability, as compared to treatment with lapatinib alone. At 5 µM lapatinib, the introduction of dexamethasone 20 µM produced a 59% decline in viability. This is the first study to document a clinically important interaction between lapatinib and dexamethasone, which associates with an increased occurrence of hepatotoxicity. The in vitro findings have provided substantiating evidence and insights on the role of dexamethasone in lapatinib-induced hepatotoxicity.

Cardiovascular changes during maturation and ageing in male and female spontaneously hypertensive rats.

BACKGROUND: Cardiovascular remodeling leading to heart failure is common in the elderly. Testing effective pharmacological treatment of human heart failure requires a suitable animal model that adequately mimics the human disease state. METHODS: This study has characterized the structural, functional, and electrical characteristics of the cardiovascular system throughout the lifespan in male and female spontaneously hypertensive rats (SHRs), a genetic model of chronic hypertension-induced cardiovascular remodeling, and age- and gender-matched normotensive controls, to determine whether ageing SHRs mimic the changes seen in ageing humans. RESULTS: Both the ageing male and female SHRs developed progressive hypertension, ventricular hypertrophy, left ventricular fibrosis, action potential prolongation without impaired glucose tolerance. Male SHRs from 15 months of age exhibited left ventricular wall thinning and chamber dilation, together with systolic and diastolic dysfunction and increased cardiac stiffness and increased erythrocyte superoxide production, which were not present in the female SHRs. CONCLUSION: Ageing male SHRs in contrast to the female SHRs, better mimic the chronic heart failure in humans produced by chronic hypertension. Ageing male SHRs could then be used to investigate proposed therapeutic interventions for chronic congestive heart failure in humans.