Interaction of sorafenib and cytochrome P450 isoenzymes in patients with advanced melanoma: a phase I/II pharmacokinetic interaction study

Anti-Melanoma Effects of Miconazole: Investigating the Mitochondria Involvement

Miconazole is an antimycotic drug showing anti-cancer effects in several cancers. However, little is known on its effects in melanoma. A375 and SK-MEL-28 human melanoma cell lines were exposed to miconazole and clotrimazole (up to 100 mM). Proliferation, viability with MTT assay and vascular mimicry were assayed at 24 h treatment. Molecular effects were measured at 6 h, namely, ATP-, ROS-release and mitochondria-related cytofluorescence. A metabolomic profile was also investigated at 6 h treatment. Carnitine was one of the most affected metabolites; therefore, the expression of 29 genes involved in carnitine metabolism was investigated in the public platform GEPIA2 on 461 melanoma patients and 558 controls. After 24 h treatments, miconazole and clotrimazole strongly and significantly inhibited proliferation in the presence of 10% serum on either melanoma cell lines; they also strongly reduced viability and vascular mimicry. After 6 h treatment, ATP reduction and ROS increase were observed, as well as a significant reduction in mitochondria-related fluorescence. Further, in A375, miconazole strongly and significantly altered expression of several metabolites including carnitines, phosphatidyl-cholines, all amino acids and several other small molecules, mostly metabolized in mitochondria. The expression of 12 genes involved in carnitine metabolism was found significantly modified in melanoma patients, 6 showing a significant impact on patients' survival. Finally, miconazole antiproliferation activity on A375 was found completely abrogated in the presence of carnitine, supporting a specific role of carnitine in melanoma protection toward miconazole effect, and was significantly reversed in the presence of caspases inhibitors such as ZVAD-FMK and Ac-DEVD-CHO, and a clear pro-apoptotic effect was observed in miconazole-treated cells, by FACS analysis of Annexin V-FITC stained cells. Miconazole strongly affects proliferation and other biological features in two human melanoma cell lines, as well as mitochondria-related functions such as ATP- and ROS-release, and the expression of several metabolites is largely dependent on mitochondria function. Miconazole, likely acting via carnitine and mitochondria-dependent apoptosis, is therefore suggested as a candidate for further investigations in melanoma treatments.

FLT3 inhibitors and novel therapeutic strategies to reverse AML resistance: An updated comprehensive review

FMS-like tyrosine kinase 3 (FLT3) mutations occur in almost 30% of acute myeloid leukemia (AML) patients. Despite the initial clinical efficacy of FLT3 inhibitors, many treated AML patients with mutated FLT3 eventually relapse. This review critically discusses the opportunities and challenges of FLT3-targeted therapies and sheds light on their drug interactions as well as potential biomarkers. Furthermore, we focus on the molecular mechanisms underlying the resistance of FLT3 internal tandem duplication (FLT3-ITD) AMLs to FLT3 inhibitors alongside novel therapeutic strategies to reverse resistance. Notably, dynamic heterogeneous patterns of clonal selection and evolution contribute to the resistance of FLT3-ITD AMLs to FLT3 inhibitors. Ongoing preclinical research and clinical trials are actively directed towards devising rational "personalized" or "patient-tailored" combinatorial therapeutic regimens to effectively treat patients with FLT3 mutated AML.

Phase I Targeted Combination Trial of Sorafenib and GW5074 in Patients with Advanced Refractory Solid Tumors

Background: Combination therapy with the administration of GW5074 and sorafenib significantly induced necrotic death in various cancer cells in vivo, as well as prolonging the survival of an animal disease model due to significant suppression of the primary and metastatic lesions. We sought to determine the safety, tolerability, pharmacokinetics, and anti-tumor activity of this co-administration therapy in patients with refractory advanced solid cancers. Methods: Twelve patients were enrolled. Eligible subjects received different dosages of GW5074 in one of the three dose cohorts (Cohort 1: 750 mg daily, Cohort 2: 1500 mg daily, Cohort 3: 750 mg twice daily) plus 200 mg of sorafenib daily to determine the maximum tolerated dose (MTD) and dose limiting toxicities (DLT) at phase 1. Furthermore, the expression level of phosphorylated DAPK^S308 in primary tumor, metastatic tumor, and circulating tumor cells (CTC) were evaluated to investigate the relationship between biomarker and the efficacy profile. Results: Among the 12 enrolled patients in this phase 1 trial, most adverse effects (AE) were grade 1, with two being grade 3. The most frequent AE of all grades were weight loss and hypertension, occurring in 16.7% of participants. Eight patients (66.7%) had the disease controlled by receiving co-administration therapy of GW5074 and sorafenib. GW5074 was found to have poor absorption, as increasing the dosage did not result in a significant increase in the bioavailability of GW5074 in subjects. Furthermore, the expression level of phosphorylated DAPK^S308 in tumor and CTCs were correlated with the disease control rate (DCR) and duration of response (DOR). Conclusions: Co-administration therapy of GW5074 and sorafenib demonstrated a favorable safety profile and showed anti-tumor activity in a variety of tumor types. However, the solubility of GW5074 is not satisfactory. A future phase 2a trial will be carried out using the new salted form that has been proven to be more effective.

Cytochrome P450 3A Time-Dependent Inhibition Assays Are Too Sensitive for Identification of Drugs Causing Clinically Significant Drug-Drug Interactions: A Comparison of Human Liver Microsomes and Hepatocytes and Definition of Boundaries for Inactivation Rate Constants

Time-dependent inhibition (TDI) of CYP3A is an important mechanism underlying numerous drug-drug interactions (DDIs), and assays to measure this are done to support early drug research efforts. However, measuring TDI of CYP3A in human liver microsomes (HLMs) frequently yields overestimations of clinical DDIs and thus can lead to the erroneous elimination of many viable drug candidates from further development. In this investigation, 50 drugs were evaluated for TDI in HLMs and suspended human hepatocytes (HHEPs) to define appropriate boundary lines for the TDI parameter rate constant for inhibition (k_obs) at a concentration of 30 µM. In HLMs, a k_obs value of 0.002 minute^-1 was statistically distinguishable from control; however, many drugs show k_obs greater than this but do not cause DDI. A boundary line defined by the drug with the lowest k_obs that causes a DDI (diltiazem) was established at 0.01 minute^-1 Even with this boundary, of the 33 drugs above this value, only 61% cause a DDI (true positive rate). A corresponding analysis was done using HHEPs; k_obs of 0.0015 minute^-1 was statistically distinguishable from control, and the boundary was established at 0.006 minute^-1 Values of k_obs in HHEPs were almost always lower than those in HLMs. These findings offer a practical guide to the use of TDI data for CYP3A in early drug-discovery research. SIGNIFICANCE STATEMENT: Time-dependent inhibition of CYP3A is responsible for many drug interactions. In vitro assays are employed in early drug research to identify and remove CYP3A time-dependent inhibitors from further consideration. This analysis demonstrates suitable boundaries for inactivation rates to better delineate drug candidates for their potential to cause clinically significant drug interactions.

Differential inhibition of human CYP2C8 and molecular docking interactions elicited by sorafenib and its major N-oxide metabolite

The tyrosine kinase inhibitor sorafenib (SOR) is being used increasingly in combination with other anticancer agents like paclitaxel, but this increases the potential for drug toxicity. SOR inhibits several human CYPs, including CYP2C8, which is a major enzyme in the elimination of oncology drugs like paclitaxel and imatinib. It has been reported that CYP2C8 inhibition by SOR in human liver microsomes is potentiated by NADPH-dependent biotransformation. This implicates a SOR metabolite in enhanced inhibition, although the identity of that metabolite is presently unclear. The present study evaluated the capacity of the major N-oxide metabolite of SOR (SNO) to inhibit CYP2C8-dependent paclitaxel 6α-hydroxylation. The IC₅₀ of SNO against CYP2C8 activity was found to be 3.7-fold lower than that for the parent drug (14 μM versus 51 μM). In molecular docking studies, both SOR and SNO interacted with active site residues in CYP2C8, but four additional major hydrogen and halogen bonding interactions were identified between SNO and amino acids in the B-B' loop region and helixes F' and I that comprise the catalytic region of the enzyme. In contrast, the binding of both SOR and SNO to active site residues in the closely related human CYP2C9 enzyme was similar, as were the IC₅₀s determined against CYP2C9-mediated losartan oxidation. These findings suggest that the active metabolite SNO could impair the elimination of coadministered drugs that are substrates for CYP2C8, and mediate toxic adverse events, perhaps in those individuals in whom SNO is formed extensively.

Association of Gastric Acid Suppression and Sorafenib Efficacy in Advanced Hepatocellular Carcinoma

BACKGROUND

Recent studies have revealed that coadministration of gastric acid suppressants reduces the efficacy of the tyrosine kinase inhibitors erlotinib and sunitinib in patients with non-small cell lung cancer and renal cell carcinoma, respectively. The authors have therefore assessed if the concurrent use of gastric acid suppressants and sorafenib impairs outcomes in patients with advanced hepatocellular carcinoma (HCC).

METHODS

A retrospective analysis was conducted on all patients treated with sorafenib for advanced HCC at a single tertiary referral unit in the United Kingdom, between January 2008 and January 2014. A multivariate Cox proportional hazard model was used to assess the effect of the concomitant use of gastric acid suppression and sorafenib on progression-free survival (PFS) and overall survival (OS).

RESULTS

Data were collected from 197 patients, of which 182 could be assessed for this study; 77 (42%) were on concurrent gastric acid suppression therapy. After adjusting for imbalances between the groups, a Cox regression analysis gave an adjusted hazard ratio for the concurrent acid suppression group compared with the no acid suppression group of 5.4 (95% confidence interval, 3.6-7.9) for PFS and 1.85 (95% confidence interval, 1.3-2.6) for OS.

CONCLUSIONS

This single-center experience shows that patients with advanced HCC taking sorafenib and concomitant gastric acid suppression therapy have significantly inferior PFS and OS. This is the first time that this negative interaction has been reported and further prospective validation is warranted.

Inhibition and induction of CYP enzymes in humans: an update

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug–drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug–drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

Clinical Pharmacokinetics and Pharmacodynamics of Transarterial Chemoembolization and Targeted Therapies in Hepatocellular Carcinoma

The management of hepatocellular carcinoma (HCC) is based on a multidisciplinary decision tree. Treatment includes loco-regional therapy, mainly transarterial chemoembolization, for intermediate-stage HCC and systemic therapy with oral tyrosine kinase inhibitors (TKIs) for advanced HCC. Transarterial chemoembolization involves hepatic intra-arterial infusion with either conventional procedure or drug-eluting-beads. The aim of the loco-regional procedure is to deliver treatment as close as possible to the tumor both to embolize the tumor area and to enhance efficacy and minimize systemic toxicity of the anticancer drug. Pharmacokinetic studies applied to transarterial chemoembolization are rare and pharmacodynamic studies even rarer. However, all available studies lead to the same conclusions: use of the transarterial route lowers systemic exposure to the cytotoxic drug and leads to much higher tumor drug concentrations than does a similar dose via the intravenous route. However, reproducibility of the procedure remains a major problem, and no consensus exists regarding the choice of anticancer drug and its dosage. Systemic therapy with TKIs is based on sorafenib and lenvatinib as first-line treatment and regorafenib and cabozantinib as second-line treatment. Clinical use of TKIs is challenging because of their complex pharmacokinetics, with high liver metabolism yielding both active metabolites and their common toxicities. Changes in liver function over time with the progression of HCC adds further complexity to the use of TKIs. The challenges posed by TKIs and the HCC disease process means monitoring of TKIs is required to improve clinical management. To date, only partial data supporting sorafenib monitoring is available. Results from further pharmacokinetic/pharmacodynamic studies of these four TKIs are eagerly awaited and are expected to permit such monitoring and the development of consensus guidelines.

Assessment of the Effect of Sorafenib on Omega-6 and Omega-3 Epoxyeicosanoid Formation in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer death. The multikinase inhibitor sorafenib is widely used for systemic therapy in advanced HCC. Sorafenib might affect epoxyeicosanoids, as it is also a potent inhibitor of the soluble epoxide hydrolase (sEH), which catalyzes the conversion of epoxides derived from long-chain polyunsaturated fatty acids (PUFAs), such as arachidonic acid (AA) and omega-3 docosahexaenoic acid (DHA), into their corresponding diols. Experimental studies with AA-derived epoxyeicosatrienoic acids (EETs) showed that they can promote tumor growth and metastasis, while DHA-derived 19,20-epoxydocosapentaenoic acid (19,20-EDP) was shown to have anti-tumor activity in mice. In this pilot study, we assessed the effect of sorafenib treatment on the presence of lipid mediators, such as EETs, in blood of the patients with HCC using the lipidomics technology. We found a significant increase in 11,12-EET and 14,15-EET levels in HCC patients treated with sorafenib. Furthermore, while not significant in this small sample set, the data presented indicate that sorafenib can also increase the level of omega-3 DHA-derived 19,20-EDP. While the effect on EETs might hamper the anti-tumor effect of sorafenib, we hypothesize that supplementation of DHA in sorafenib-treated HCC patients could increase the level of 19,20-EDP and thereby enhance its anti-tumor effect.

The Role of CYP450 Drug Metabolism in Precision Cardio-Oncology

As many novel cancer therapies continue to emerge, the field of Cardio-Oncology (or onco-cardiology) has become crucial to prevent, monitor and treat cancer therapy-related cardiovascular toxicity. Furthermore, given the narrow therapeutic window of most cancer therapies, drug-drug interactions are prevalent in the cancer population. Consequently, there is an increased risk of affecting drug efficacy or predisposing individual patients to adverse side effects. Here we review the role of cytochrome P450 (CYP450) enzymes in the field of Cardio-Oncology. We highlight the importance of cardiac medications in preventive Cardio-Oncology for high-risk patients or in the management of cardiotoxicities during or following cancer treatment. Common interactions between Oncology and Cardiology drugs are catalogued, emphasizing the impact of differential metabolism of each substrate drug on unpredictable drug bioavailability and consequent inter-individual variability in treatment response or development of cardiovascular toxicity. This inter-individual variability in bioavailability and subsequent response can be further enhanced by genomic variants in CYP450, or by modifications of CYP450 gene, RNA or protein expression or function in various 'omics' related to precision medicine. Thus, we advocate for an individualized approach to each patient by a multidisciplinary team with clinical pharmacists evaluating a treatment plan tailored to a practice of precision Cardio-Oncology. This review may increase awareness of these key concepts in the rapidly evolving field of Cardio-Oncology.

Inhibition of Hepatic CYP2D6 by the Active N-Oxide Metabolite of Sorafenib

The multikinase inhibitor sorafenib (SOR) is used to treat patients with hepatocellular and renal carcinomas. SOR undergoes CYP-mediated biotransformation to a pharmacologically active N-oxide metabolite (SNO) that has been shown to accumulate to varying extents in individuals. Kinase inhibitors like SOR are frequently coadministered with a range of other drugs to improve the efficacy of anticancer drug therapy and to treat comorbidities. Recent evidence has suggested that SNO is more effective than SOR as an inhibitor of CYP3A4-mediated midazolam 1'-hydroxylation. CYP2D6 is also reportedly inhibited by SOR. The present study assessed the possibility that SNO might contribute to CYP2D6 inhibition. The inhibition kinetics of CYP2D6-mediated dextromethorphan O-demethylation were analyzed in human hepatic microsomes, with SNO found to be ~ 19-fold more active than SOR (K_is 1.8 ± 0.3 μM and 34 ± 11 μM, respectively). Molecular docking studies of SOR and SNO were undertaken using multiple crystal structures of CYP2D6. Both molecules mediated interactions with key amino acid residues in putative substrate recognition sites of CYP2D6. However, a larger number of H-bonding interactions was noted between the N-oxide moiety of SNO and active site residues that account for its greater inhibition potency. These findings suggest that SNO has the potential to contribute to pharmacokinetic interactions involving SOR, perhaps in those individuals in whom SNO accumulates.

Sorafenib

Sorafenib (BAY-43-9006), marketed by Bayer as Nexavar® (USA), is anticancer drug approved by US-FDA for the treatment of unresectable hepatocellular carcinoma and advanced renal cell carcinoma. Sorafenib inhibited tumor growth and angiogenesis through targeting both the RAF/MEK/ERK pathway and receptor tyrosine kinases. This study presents a comprehensive profile of sorafenib, including detailed nomenclature, formula, elemental analysis, methods of preparation, physico-chemical characteristics, and methods of analysis (including spectroscopic, electrochemical, and chromatographic methods of analysis). Spectroscopic and spectrometric analyses include UV/vis spectroscopy, vibrational spectroscopy, nuclear magnetic resonance spectrometry ((1)H and (13)C NMR), and mass spectrometry. Chromatographic methods of analyses include thin layer chromatography and high-performance liquid chromatography. Only few stability indicating methods were found for quantification of sorafenib after exposing tablet dosage form to various stress conditions such as hydrolysis, oxidation, thermal stress, photo and UV light. However, none of these described methods were made to separate and quantify the degradation products. Pharmacology studies including pharmacodynamics, mechanism of action, pharmacokinetics and drug-drug interactions were also presented. An appropriate table and figures were attached to each of the above mentioned sections along with total of 55 references.

Evaluation of the pharmacokinetic drug interaction potential of tivantinib (ARQ 197) using cocktail probes in patients with advanced solid tumours

AIMS

This phase 1, open-label, crossover study sought to evaluate drug-drug interactions between tivantinib and cytochrome P450 (CYP) substrates and tivantinib and P-glycoprotein.

METHODS

The effect of tivantinib doses on the pharmacokinetics of the probe drugs for CYP1A2 (caffeine), CYP2C9 (S-warfarin), CYP2C19 (omeprazole), and CYP3A4 (midazolam), and for P-glycoprotein (digoxin) was investigated in 28 patients with advanced cancer using a cocktail probe approach. Patients received single doses of probe drugs alone and, after 5 days of treatment, with tivantinib 360 mg twice daily.

RESULTS

The ratios of geometric least squares mean (90% confidence interval) for the area under the concentration-time curve from time zero to the last quantifiable concentration in the presence/absence of tivantinib were 0.97 (0.89-1.05) for caffeine, 0.88 (0.76-1.02) for S-warfarin, 0.89 (0.60-1.31) for omeprazole, 0.83 (0.67-1.02) for midazolam, and 0.69 (0.51-0.94) for digoxin. Similar effects were observed for maximum plasma concentrations; the ratio for digoxin in the presence/absence of tivantinib was 0.75 (0.60-0.95).

CONCLUSIONS

The data suggest that tivantinib 360 mg twice daily has either a minimal or no effect on the pharmacokinetics of probe drugs for CYP1A2, CYP2C9, CYP2C19 and CYP3A4 substrates, and decreases the systemic exposure of P-glycoprotein substrates when administered with tivantinib.

Inefficiencies and Patient Burdens in the Development of the Targeted Cancer Drug Sorafenib: A Systematic Review

Failure in cancer drug development exacts heavy burdens on patients and research systems. To investigate inefficiencies and burdens in targeted drug development in cancer, we conducted a systematic review of all prelicensure trials for the anticancer drug, sorafenib (Bayer/Onyx Pharmaceuticals). We searched Embase and MEDLINE databases on October 14, 2014, for prelicensure clinical trials testing sorafenib against cancers. We measured risk by serious adverse event rates, benefit by objective response rates and survival, and trial success by prespecified primary endpoint attainment with acceptable toxicity. The first two clinically useful applications of sorafenib were discovered in the first 2 efficacy trials, after five drug-related deaths (4.6% of 108 total) and 93 total patient-years of involvement (2.4% of 3,928 total). Thereafter, sorafenib was tested in 26 indications and 67 drug combinations, leading to one additional licensure. Drug developers tested 5 indications in over 5 trials each, comprising 56 drug-related deaths (51.8% of 108 total) and 1,155 patient-years (29.4% of 3,928 total) of burden in unsuccessful attempts to discover utility against these malignancies. Overall, 32 Phase II trials (26% of Phase II activity) were duplicative, lacked appropriate follow-up, or were uninformative because of accrual failure, constituting 1,773 patients (15.6% of 11,355 total) participating in prelicensure sorafenib trials. The clinical utility of sorafenib was established early in development, with low burden on patients and resources. However, these early successes were followed by rapid and exhaustive testing against various malignancies and combination regimens, leading to excess patient burden. Our evaluation of sorafenib development suggests many opportunities for reducing costs and unnecessary patient burden in cancer drug development.

Pharmacokinetic Aspects of Vascular Endothelial Growth Factor Tyrosine Kinase Inhibitors

Scientists have identified the impact of angiogenesis on tumor growth and survival. Among other efficient drugs, several small-molecule tyrosine kinase inhibitors (TKIs) targeting the vascular endothelial growth factor receptor (VEGFR) have been developed and have already been integrated into the treatment of various advanced malignancies. This review provides a compilation of current knowledge on the pharmacokinetic aspects of all VEGFR-TKIs already approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) and of those still under investigation. Additional information on substance metabolism, potential for drug-drug interactions (DDIs), and the need for dose adaptation in patients with predominant renal and/or hepatic impairment has been included. All TKIs introduced in this review were administered orally, allowing for easy drug handling for healthcare professionals and patients. For almost all substances, the maximum plasma concentrations were reached within a short period of time. The majority of the substances showed a high plasma protein binding and their excretion occurred via the feces and, to a lesser extent, via the urine. In most cases, dose adaptation in patients with mild to moderate renal or hepatic impairment is not recommended. Cytochrome P450 (CYP) 3A4 was found to play a crucial role in the drug metabolic processes of many compounds. In order to prevent unwanted DDIs, co-administration of VEGFR TKIs together with CYP3A4 inhibitors or inducers should be avoided. Throughout all TKIs, the data indicate high inter-individual variability. The causes of this are still unclear and require further research to allow for individualization of treatment regimens.

Role of Cytochrome P450 2C8 in Drug Metabolism and Interactions

During the last 10-15 years, cytochrome P450 (CYP) 2C8 has emerged as an important drug-metabolizing enzyme. CYP2C8 is highly expressed in human liver and is known to metabolize more than 100 drugs. CYP2C8 substrate drugs include amodiaquine, cerivastatin, dasabuvir, enzalutamide, imatinib, loperamide, montelukast, paclitaxel, pioglitazone, repaglinide, and rosiglitazone, and the number is increasing. Similarly, many drugs have been identified as CYP2C8 inhibitors or inducers. In vivo, already a small dose of gemfibrozil, i.e., 10% of its therapeutic dose, is a strong, irreversible inhibitor of CYP2C8. Interestingly, recent findings indicate that the acyl-β-glucuronides of gemfibrozil and clopidogrel cause metabolism-dependent inactivation of CYP2C8, leading to a strong potential for drug interactions. Also several other glucuronide metabolites interact with CYP2C8 as substrates or inhibitors, suggesting that an interplay between CYP2C8 and glucuronides is common. Lack of fully selective and safe probe substrates, inhibitors, and inducers challenges execution and interpretation of drug-drug interaction studies in humans. Apart from drug-drug interactions, some CYP2C8 genetic variants are associated with altered CYP2C8 activity and exhibit significant interethnic frequency differences. Herein, we review the current knowledge on substrates, inhibitors, inducers, and pharmacogenetics of CYP2C8, as well as its role in clinically relevant drug interactions. In addition, implications for selection of CYP2C8 marker and perpetrator drugs to investigate CYP2C8-mediated drug metabolism and interactions in preclinical and clinical studies are discussed.

Therapeutic protein-drug interaction assessment for daclizumab high-yield process in patients with multiple sclerosis using a cocktail approach

AIMS

To characterize the potential effect of daclizumab high-yield process (DAC HYP), a monoclonal antibody that blocks the high-affinity interleukin-2 receptors for treatment of multiple sclerosis, on activity of cytochrome P450 (CYP) enzymes.

METHODS

Twenty patients with multiple sclerosis received an oral cocktail of probe substrates of CYP1A2 (caffeine 200 mg), CYP2C9 (warfarin 10 mg/vitamin K 10 mg), CYP2C19 (omeprazole 40 mg), CYP2D6 (dextromethorphan 30 mg) and CYP3A (midazolam 5 mg) on two sequential occasions: 7 days before and 7 days after subcutaneous administration of DAC HYP 150 mg every 4 weeks for three doses. Serial pharmacokinetic blood samples up to 96 h post dose and 12-h urine samples were collected on both occasions. Area under the curve (AUC) for caffeine, S-warfarin, omeprazole and midazolam, and urine dextromethorphan to dextrorphan ratio were calculated. Statistical analyses were conducted on log-transformed parameters using a linear mixed-effects model.

RESULTS

The 90% confidence intervals (CIs) for the geometric mean ratio (probe substrate with DAC HYP/probe substrate alone) for caffeine AUC from 0-12 h (0.93-1.15), S-warfarin AUC from 0 to infinity (AUC[0-inf]) (0.95-1.06), omeprazole AUC(0-inf) (0.88-1.13) and midazolam AUC(0-inf) (0.89-1.15) were within the no-effect boundary of 0.80-1.25. The geometric mean ratio for urine dextromethorphan to dextrorphan ratio was 1.01, with the 90% CI (0.76-1.34) extending slightly outside the no-effect boundary, likely due to high variability with urine collections and CYP2D6 activity.

CONCLUSIONS

DAC HYP treatment in patients with multiple sclerosis had no effect on CYP 1A2, 2C9, 2C19, 2D6 and 3A activity.

Microarray Analysis of Differentially-Expressed Genes Encoding CYP450 and Phase II Drug Metabolizing Enzymes in Psoriasis and Melanoma

Cytochrome P450 drug metabolizing enzymes are implicated in personalized medicine for two main reasons. First, inter-individual variability in CYP3A4 expression is a confounding factor during cancer treatment. Second, inhibition or induction of CYP3A4 can trigger adverse drug–drug interactions. However, inflammation can downregulate CYP3A4 and other drug metabolizing enzymes and lead to altered metabolism of drugs and essential vitamins and lipids. Little is known about effects of inflammation on expression of CYP450 genes controlling drug metabolism in the skin. Therefore, we analyzed seven published microarray datasets, and identified differentially-expressed genes in two inflammatory skin diseases (melanoma and psoriasis). We observed opposite patterns of expression of genes regulating metabolism of specific vitamins and lipids in psoriasis and melanoma samples. Thus, genes controlling the turnover of vitamin D (CYP27B1, CYP24A1), vitamin A (ALDH1A3, AKR1B10), and cholesterol (CYP7B1), were up-regulated in psoriasis, whereas melanomas showed downregulation of genes regulating turnover of vitamin A (AKR1C3), and cholesterol (CYP39A1). Genes controlling abnormal keratinocyte differentiation and epidermal barrier function (CYP4F22, SULT2B1) were up-regulated in psoriasis. The up-regulated CYP24A1, CYP4F22, SULT2B1, and CYP7B1 genes are potential drug targets in psoriatic skin. Both disease samples showed diminished drug metabolizing capacity due to downregulation of the CYP1B1 and CYP3A5 genes. However, melanomas showed greater loss of drug metabolizing capacity due to downregulation of the CYP3A4 gene.

Seizures and cancer: drug interactions of anticonvulsants with chemotherapeutic agents, tyrosine kinase inhibitors and glucocorticoids

Patients with cancer commonly experience seizures. Combined therapy with anticonvulsant drugs (AEDs) and chemotherapeutic drugs or tyrosine kinase inhibitors carries inherent risks on drug-drug interactions (DDIs). In this review, pharmacokinetic studies of AEDs with chemotherapeutic drugs, tyrosine kinase inhibitors, and glucocorticoids are discussed, including data on maximum tolerated dose, drug clearance, elimination half-life, and organ exposure. Enzyme-inducing AEDs (EIAEDs) cause about a 2-fold to 3-fold faster clearance of concurrent chemotherapeutic drugs metabolized along the same pathway, including cyclophosphamide, irinotecan, paclitaxel, and teniposide, and up to 4-fold faster clearance with the tyrosine kinase inhibitors crizotinib, dasatinib, imatinib, and lapatinib. The use of tyrosine kinase inhibitors, particularly imatinib and crizotinib, may lead to enzyme inhibition of concurrent therapy. Many of the newer generation AEDs do not induce or inhibit drug metabolism, but they can alter enzyme activity by other drugs including AEDs, chemotherapeutics and tyrosine kinase inhibitors. Glucocorticoids can both induce and undergo metabolic change. Quantitative data on changes in drug metabolism help to apply the appropriate dose regimens. Because the large individual variability in metabolic activity increases the risks for undertreatment and/or toxicity, we advocate routine plasma drug monitoring. There are insufficient data available on the effects of tyrosine kinase inhibitors on AED metabolism.

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.

Effects of Sorafenib Dose on Acquired Reversible Resistance and Toxicity in Hepatocellular Carcinoma

Acquired evasive resistance is a major limitation of hepatocellular carcinoma (HCC) treatment with the tyrosine kinase inhibitor (TKI) sorafenib. Recent findings suggest that resistance to sorafenib may have a reversible phenotype. In addition, loss of responsiveness has been proposed to be due to a gradual decrease in sorafenib plasma levels in patients. Here, the possible mechanisms underlying reversible sorafenib resistance were investigated using a Hep3B-hCG orthotopic human xenograft model of locally advanced HCC. Tissue and plasma sorafenib and metabolite levels, downstream antitumor targets, and toxicity were assessed during standard and dose-escalated sorafenib treatment. Drug levels were found to decline significantly over time in mice treated with 30 mg/kg sorafenib, coinciding with the onset of resistance but a greater magnitude of change was observed in tissues compared with plasma. Skin rash also correlated with drug levels and tended to decrease in severity over time. Drug level changes appeared to be partially tumor dependent involving induction of tumoral CYP3A4 metabolism, with host pretreatment alone unable to generate resistance. Escalation from 30 to 60 mg/kg sorafenib improved antitumor efficacy but worsened survival due to excessive body weight loss. Microvessel density was inhibited by sorafenib treatment but remained suppressed over time and dose increase. In conclusion, tumor CYP3A4 induction by sorafenib is a novel mechanism to account for variability in systemic drug levels; however, declining systemic sorafenib levels may only be a minor resistance mechanism. Escalating the dose may be an effective treatment strategy, provided toxicity can be controlled.

Drug-drug interactions with tyrosine-kinase inhibitors: a clinical perspective

In the past decade, many tyrosine-kinase inhibitors have been introduced in oncology and haemato-oncology. Because this new class of drugs is extensively used, serious drug-drug interactions are an increasing risk. In this Review, we give a comprehensive overview of known or suspected drug-drug interactions between tyrosine-kinase inhibitors and other drugs. We discuss all haemato-oncological and oncological tyrosine-kinase inhibitors that had been approved by Aug 1, 2013, by the US Food and Drug Administration or the European Medicines Agency. Various clinically relevant drug interactions with tyrosine-kinase inhibitors have been identified. Most interactions concern altered bioavailability due to altered stomach pH, metabolism by cytochrome P450 isoenzymes, and prolongation of the QTc interval. To guarantee the safe use of tyrosine-kinase inhibitors, a drugs review for each patient is needed. This Review provides specific recommendations to guide haemato-oncologists, oncologists, and clinical pharmacists, through the process of managing drug-drug interactions during treatment with tyrosine-kinase inhibitors in daily clinical practice.

Psychotic disorder induced by a combination of sorafenib and BAY86-9766

The Ras-Raf-mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK cascade is important in the intra-cellular transduction of neurotransmitters, such as dopamine and glutamate. Sorafenib (Nexavar), a multi-kinase inhibitor targeting Raf kinase, vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor, has shown promising results in the treatment of malignancies. BAY86-9766, a novel selective MEK 1/2 inhibitor, is being evaluated in clinical trials as an anticancer drug. We describe herein a hepatocellular carcinoma patient presenting with recurrent psychotic symptoms in the course of the BASIL trial (assessing BAY86-9766 plus sorafenib for the treatment of liver cancer). In this case, VEGFR inhibition caused by sorafenib alone may have contributed to the development of psychosis. A change in ERK activity might also have been involved. However, whether single or combination use of the two drugs is responsible for inducing the psychotic symptoms remains unclear. In summary, the role of the ERK pathway in psychosis is still vague. Further investigation of the ERK activity in patients with psychotic disorders may disclose its role in the pathophysiology of psychosis.

Drug safety evaluation of sorafenib for treatment of solid tumors: consequences for the risk assessment and management of cancer patients

INTRODUCTION

Sorafenib is a multi-tyrosine kinase inhibitor (TKI). Considerable clinical experience has been accumulated since its first Phase III clinical trial in metastatic renal cancer patients in 2007. The management of its early acute toxicity in fit patients is well known. The management of prolonged treatment becomes the new challenge.

AREAS COVERED

Using sorafenib as a key word for PubMed search, we review preclinical and clinical data and discuss the pharmacokinetics and pharmacodynamics of sorafenib, its acute and cumulative toxicities and their consequences for patient management.

EXPERT OPINION

The systematic multi-disciplinary risk assessment of cancer patients prior to TKI initiation reduces the risks of acute and late toxicity, especially drug-drug interactions and arterial risks. Sarcopenia is now identified as a major risk of severe toxicity. The very diverse clinical pictures of cumulative toxicity must be known. The monitoring of sorafenib systemic exposure is helpful especially in elderly patients. Moreover, at disease progression, it allows distinguishing between underexposure to sorafenib and truly acquired resistance to the drug. The optimal use of sorafenib should allow improving the reported results of flat-dose. Finally, most of this knowledge could be used for the development and optimal use of the other TKIs.

Management of common adverse events in patients treated with sorafenib: nurse and pharmacist perspective

Sorafenib, a tyrosine kinase inhibitor, is indicated for the treatment of patients with unresectable hepatocellular carcinoma (HCC) and advanced renal cell carcinoma (RCC). Sorafenib is currently being evaluated in phase II and III trials in various malignancies as a single agent (locally advanced/metastatic radioactive iodine-refractory differentiated thyroid cancer [DTC]), as part of multimodality care (HCC), and in combination with chemotherapies (metastatic breast cancer). Grade 1 and 2 adverse events (AEs) that commonly occur during treatment (ie, dermatologic manifestations, diarrhea, fatigue, and hypertension) should be proactively managed. The goal is to allow patients to remain on their full dose of sorafenib for as long as their treatment is indicated. A combination of early recognition of and intervention for AEs, patient education, and an open dialogue between patients and their multidisciplinary healthcare team, with timely reporting of AEs, will allow for effective management of AEs and minimize the need for sorafenib dose reduction or discontinuation.

Inhibition of OATP1B1 by tyrosine kinase inhibitors: in vitro-in vivo correlations

BACKGROUND

Several tyrosine kinase inhibitors (TKIs) can decrease docetaxel clearance in patients by an unknown mechanism. We hypothesised that these interactions are mediated by the hepatic uptake transporter OATP1B1.

METHODS

The influence of 16 approved TKIs on transport was studied in vitro using HEK293 cells expressing OATP1B1 or its mouse equivalent Oatp1b2. Pharmacokinetic studies were performed with Oatp1b2-knockout and OATP1B1-transgenic mice.

RESULTS

All docetaxel-interacting TKIs, including sorafenib, were identified as potent inhibitors of OATP1B1 in vitro. Although Oatp1b2 deficiency in vivo was associated with increased docetaxel exposure, single- or multiple-dose sorafenib did not influence docetaxel pharmacokinetics.

CONCLUSION

These findings highlight the importance of identifying proper preclinical models for verifying and predicting TKI-chemotherapy interactions involving transporters.

Drug interactions with solid tumour-targeted therapies

Drug interactions are an on-going concern in the treatment of cancer, especially when targeted therapies, such as tyrosine kinase inhibitors (TKI) or mammalian target of rapamycin (mTOR) inhibitors, are being used. The emergence of elderly patients and/or patients with both cancer and other chronic co-morbidities leads to polypharmacy. Therefore, the risk of drug-drug interactions (DDI) becomes a clinically relevant issue, all the more so as TKIs and mTOR inhibitors are essentially metabolised by cytochrome P450 enzymes. These DDIs can result in variability in anticancer drug exposure, thus favouring the selection of resistant cellular clones or the occurrence of toxicity. This review provides a comprehensive overview of DDIs that involve targeted therapies approved by the FDA for the treatment of solid tumours for more than 3 years (sorafenib, sunitinib, erlotinib, gefitinib, imatinib, lapatinib, everolimus, temsirolimus) and medicinal herb or drugs. This review also provides some guidelines to help oncologists and pharmacists in their clinical practice.

Interactions between oral antineoplastic agents and concomitant medication: a systematic review

INTRODUCTION

In recent years, the number of oral antitumoral agents has considerably increased. Oral administration increases the risk of interactions, because most oral anticancer drugs are taken on a daily basis. Interactions can increase exposure to antitumoral agents or cause treatment failure. Many antitumoral drugs undergo enzymatic metabolism by cytochrome P450. As some act as inducers or inhibitors of one or more isoenzymes, they can lead to decreases or increases in plasma concentrations of concomitant drugs. Hence, cytostatic drugs can act not only as victims but also as perpetrators. P-glycoprotein, an efflux transporter, can also be involved in pharmacokinetic interactions.

AREAS COVERED

A Medline search was performed to summarize the available evidence of the most clinically relevant interactions between oral chemotherapy agents and other drugs. The search covered the period from 1966 until August 2012 for each antitumoral drug using the medical subject headings 'Drug Interactions' OR 'Pharmacokinetics'. While the present review is not exhaustive, it aims to increase clinicians' awareness of potential drug-drug interactions.

EXPERT OPINION

As cancer patients are often polymedicated and treated by different physicians, the risk of drug interactions between antitumoral agents and other medications is high. More clinical interaction studies are encouraged to ensure appropriate antineoplastic pharmacokinetics in clinical practice.

Sucralose, a synthetic organochlorine sweetener: overview of biological issues

Sucralose is a synthetic organochlorine sweetener (OC) that is a common ingredient in the world's food supply. Sucralose interacts with chemosensors in the alimentary tract that play a role in sweet taste sensation and hormone secretion. In rats, sucralose ingestion was shown to increase the expression of the efflux transporter P-glycoprotein (P-gp) and two cytochrome P-450 (CYP) isozymes in the intestine. P-gp and CYP are key components of the presystemic detoxification system involved in first-pass drug metabolism. The effect of sucralose on first-pass drug metabolism in humans, however, has not yet been determined. In rats, sucralose alters the microbial composition in the gastrointestinal tract (GIT), with relatively greater reduction in beneficial bacteria. Although early studies asserted that sucralose passes through the GIT unchanged, subsequent analysis suggested that some of the ingested sweetener is metabolized in the GIT, as indicated by multiple peaks found in thin-layer radiochromatographic profiles of methanolic fecal extracts after oral sucralose administration. The identity and safety profile of these putative sucralose metabolites are not known at this time. Sucralose and one of its hydrolysis products were found to be mutagenic at elevated concentrations in several testing methods. Cooking with sucralose at high temperatures was reported to generate chloropropanols, a potentially toxic class of compounds. Both human and rodent studies demonstrated that sucralose may alter glucose, insulin, and glucagon-like peptide 1 (GLP-1) levels. Taken together, these findings indicate that sucralose is not a biologically inert compound.

Safety and Efficacy of Sorafenib in Renal Cell Carcinoma

This article reviews data on sorafenib use in renal cell carcinoma. Mechanisms of actions and pharmacokinetics are briefly described. Major clinical trials are presented, summarizing efficacy and safety of sorafenib. Its place in current treatment of renal cell carcinoma is discussed. Sorafenib is likely to remain one of the mainstays of RCC treatment in coming years.

Contribution of tumoral and host solute carriers to clinical drug response

Members of the solute carrier family of transporters are responsible for the cellular uptake of a broad range of endogenous compounds and xenobiotics in multiple tissues. Several of these solute carriers are known to be expressed in cancer cells or cancer cell lines, and decreased cellular uptake of drugs potentially contributes to the development of resistance. As result, the expression levels of these proteins in humans have important consequences for an individual's susceptibility to certain drug-induced side effects, interactions, and treatment efficacy. In this review article, we provide an update of this rapidly emerging field, with specific emphasis on the direct contribution of solute carriers to anticancer drug uptake in tumors, the role of these carriers in regulation of anticancer drug disposition, and recent advances in attempts to evaluate these proteins as therapeutic targets.