Evaluation of potential inductive effects of aprepitant on cytochrome P450 3A4 and 2C9 activity

Mechanism Underlying Conflicting Drug-Drug Interaction Between Aprepitant and Voriconazole via Cytochrome P450 3A4-Mediated Metabolism

Background

Voriconazole is an antifungal drug for which therapeutic monitoring is recommended to prevent side effects. Temporary administration of the antiemetic drug fosaprepitant remarkably decreases the plasma concentration of voriconazole from the therapeutic range. The ratio of the major metabolite voriconazole N-oxide to voriconazole exceeded that at any other time for a patient who started chemotherapy during voriconazole therapy. We attributed this unpredictable result to cytochrome P450 3A4 induced by aprepitant that was converted from fosaprepitant in vivo.

Methods

Concentrations of voriconazole and voriconazole N-oxide were measured using liquid chromatography-mass spectrometry/mass spectrometry in primary human hepatocytes after incubation with aprepitant. Aprepitant suppressed voriconazole N-oxide formation within 24 h, followed by a continuous increase. Levels of drug-metabolizing cytochrome P450 mRNA were measured using real-time PCR in primary human hepatocytes incubated with aprepitant.

Results

Cytochrome P450 3A4 and 2C9 mRNA levels increased ~4- and 2-fold, respectively, over time. Cytochrome P450 3A4 induction was confirmed using reporter assays. We also assessed L-755446, a major metabolite of aprepitant that lacks a triazole ring. Both compounds dose-dependently increased reporter activity; however, induction by L-755446 was stronger than that by aprepitant.

Conclusion

These results indicate that aprepitant initially inhibited voriconazole metabolism via its triazole ring and increased cytochrome P450 3A4 induction following L-755446 formation. The decrease in plasma voriconazole concentration 7 days after fosaprepitant administration was mainly attributed to cytochrome P450 3A4 induction by L-755446.

Effect of Aprepitant on Etoposide Pharmacokinetics in Patients with Testicular Cancer: A Pharmacokinetic Study to Determine the Absence of a Clinically Relevant Interaction

All patients treated with anticancer agents should receive the most effective anti-emetic regimen. Anti-emetic guidelines provide recommendations but do not take into account possible drug-drug interactions between anti-emetics and anticancer drugs. This study determines the clinical relevance of the potential drug-drug interaction of the neurokinin-1 receptor antagonist, aprepitant, on the pharmacokinetics of etoposide. Aprepitant is a moderate CYP3A4 inhibitor and may increase the systemic exposure of etoposide which is partly metabolized by cytochrome P450 enzyme 3A4 (CYP3A4). In this prospective observational study, the pharmacokinetics of etoposide with and without concomitant use of aprepitant was determined in 12 patients receiving first-line chemotherapy for testicular cancer. The geometric mean (95% confidence interval (CI)) area under the plasma concentration-time curve 0-24 hour (AUC0-24h ) of etoposide with aprepitant was 86.2 (79.7-93.2) mg/L*hour vs. 83.7 (75.8-92.4) mg/L*hour without aprepitant. Geometric mean ratios (90% CIs) of AUC0-24h and maximum plasma concentration (Cmax ) for etoposide with and without aprepitant were 1.03 (0.96-1.10) and 0.96 (0.89-1.03), respectively. This study confirms the absence of a clinically relevant interaction between etoposide and aprepitant. Both drugs can be safely combined without affecting etoposide exposure.

Induction of CYP3A activity by dexamethasone may not be strong, even at high doses: insights from a case of tacrolimus co-administration

BACKGROUND

Dexamethasone (DEX) induces CYP3A activity in a concentration-dependent manner. However, no study has examined changes in the blood concentration of CYP3A substrate drugs when DEX is administered at high doses. Herein, we present a case in which tacrolimus (TAC), a typical CYP3A substrate drug, was co-administered with a chemotherapy regimen that included high-dose DEX.

CASE PRESENTATION

A 71-year-old woman underwent liver transplantation for hepatocellular carcinoma 18 years prior to her inclusion in this case study. She was receiving TAC orally at 2 mg/day and had a stable trough blood concentration of approximately 4 ng/mL and a trough blood concentration/dose (C/D) ratio of approximately 2. The patient was diagnosed with post-transplant lymphoproliferative disease (histological type: Burkitt's lymphoma) after admission. Thereafter, the patient received cyclophosphamide-prednisolone (CP), followed by two courses of R-HyperCVAD (rituximab, cyclophosphamide, doxorubicin, vincristine, and DEX) and R-MA (rituximab, methotrexate, and cytarabine) replacement therapy. DEX (33 mg/day) was administered intravenously on days 1-4 and days 11-14 of R-HyperCVAD treatment, and aprepitant (APR) was administered on days 1-5 in both courses. The TAC C/D ratio decreased to approximately 1 on day 11 during both courses, and then increased. Furthermore, a decreasing trend in the TAC C/D ratio was observed after R-MA therapy. The decrease in the TAC C/D ratio was attributed to APR administration rather than to DEX.

CONCLUSION

The induction of CYP3A activity by a high dose of DEX may not be strong. The pharmacokinetic information on DEX and in vitro enzyme activity induction studies also suggested that CYP3A activity induction is not prominent under high-dose DEX treatment.

Chronic pruritus: from pathophysiology to drug design

Pruritus, the most common symptom in dermatology, is an innate response capable of protecting skin against irritants. Nonetheless, when it lasts more than six weeks it is assumed to be a chronic pathology having a negative impact on people's lives. Chronic pruritus (CP) can occur in common and rare skin diseases, having a high prevalence in global population. The existing therapies are unable to counteract CP or are associated with adverse effects, so the development of effective treatments is a pressing issue. The pathophysiological mechanisms underlying CP are not yet completely dissected but, based on current knowledge, involve a wide range of receptors, namely neurokinin 1 receptor (NK1R), Janus kinase (JAK), and transient receptor potential (TRP) ion channels, especially transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1). This review will address the relevance of these molecular targets for the treatment of CP and molecules capable of modulating these receptors that have already been studied clinically or have the potential to possibly alleviate this pathology. According to scientific and clinical literature, there is an increase in the expression of these molecular targets in the lesioned skin of patients experiencing CP when compared with non-lesioned skin, highlighting their importance for the development of potential efficacious drugs through the design of antagonists/inhibitors.

Population pharmacokinetic analysis reveals no impact of aprepitant on the pharmacokinetics of ifosfamide, 2-dechloroifosfamide, and 3-dechloroifosfamide

PURPOSE

Several case reports and retrospective series have clearly pointed to the role of aprepitant, an antiemetic drug, in the development of encephalopathy when used with ifosfamide. Described as an inhibitor of several CYP metabolic pathways, aprepitant is suspected of drug-drug-interaction on ifosfamide pharmacokinetics. The pharmacokinetics of ifosfamide and two of its metabolites (2-dechloroifosfamide and 3-dechloroifosfamide) was studied in patients with soft tissue sarcomas to evaluate the impact of aprepitant administration.

METHODS

A population pharmacokinetic approach was applied to analyze data obtained in 42 patients at cycle 1 (without aprepitant) and cycle 2 (with aprepitant for 34 of them).

RESULTS

A previously published pharmacokinetic model including a time-dependency process well fit the data. Aprepitant had no impact on ifosfamide or its two metabolite pharmacokinetic parameters.

CONCLUSION

This study suggests that aprepitant does not lead to a significant modification of ifosfamide metabolization, even though other metabolites such as 4 hydroxyifosfamide and chloroacetaldehyde were not monitored in this study.

Evaluation of hepatic CYP3A enzyme activity using endogenous markers in lung cancer patients treated with cisplatin, dexamethasone, and aprepitant

PURPOSE

Aprepitant is used with dexamethasone and 5-HT₃ receptor antagonists as an antiemetic treatment for chemotherapy, including cisplatin. Aprepitant is a substrate of cytochrome P450 (CYP) 3A4 and is known to cause its inhibition and induction. In addition, dexamethasone is a CYP3A4 substrate that induces CYP3A4 and CYP3A5 expression. In this study, we aimed to quantitatively evaluate the profile of CYP3A activity using its endogenous markers in non-small cell lung cancer patients receiving a standard cisplatin regimen with antiemetics, including aprepitant.

METHODS

Urinary 11β-hydroxytestosterone (11β-OHT)/testosterone concentration ratio and plasma 4β-hydroxycholesterol (4β-OHC) concentrations were measured before and after cisplatin treatment (days 1, 4, and 8). CYP3A5 was genotyped, and plasma aprepitant concentrations were measured on day 4 to examine its influence on CYP3A endogenous markers.

RESULTS

The urinary 11β-OHT/testosterone concentration ratio in the 35 patients included in this study increased by 2.65-fold and 1.21-fold on days 4 and 8 compared with day 1, respectively. Their plasma 4β-OHC concentration increased by 1.46-fold and 1.66-fold, respectively. The mean plasma aprepitant concentration on day 4 was 1,451 ng/mL, which is far lower than its inhibitory constant. The allele frequencies of CYP3A5*1 and CYP3A5*3 were 0.229 and 0.771, respectively. In patients with the CYP3A5*1 allele, the plasma 4β-OHC concentration was significantly lower at baseline but more potently increased with chemotherapy.

CONCLUSION

CYP3A activity was significantly induced from day 4 to day 8 in patients receiving cisplatin and three antiemetic drugs.

Chemotherapy-Induced Nausea and Vomiting: Pathogenesis, Recommendations, and New Trends

The significant physical and emotional effects of chemotherapy-induced nausea and vomiting (CINV) are experienced by cancer patients. Severe symptoms decrease the patient's quality of life and potentially deters further treatment. The five main forms of CINV (i.e., acute, delayed, anticipatory, breakthrough, and refractory) require different treatment regimens, which often include 5-HT3 receptor antagonists, NK1 receptor antagonists, and corticosteroids. Despite a significant amount of research and development of antiemetic agents, management of CINV remains a great challenge with many needs waiting to be adequately addressed, such as controlling non-acute CINV, developing appropriate CINV treatment protocols for multiple-day chemotherapy patients, and providing options for those prone to CINV despite treatment. Further research is required to optimize CINV management for these patients.

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.

Results from Drug-Drug Interaction Studies In Vitro and In Vivo Investigating the Effect of Finerenone on the Pharmacokinetics of Comedications

BACKGROUND AND OBJECTIVES

In vivo studies were performed with the novel, selective, non-steroidal mineralocorticoid receptor antagonist finerenone to assess the relevance of inductive and/or inhibitory effects on cytochrome P450 (CYP) enzymes observed in vitro.

METHODS

CYP isoenzyme-specific substrates were incubated in vitro with finerenone or its metabolites to investigate reversible and irreversible inhibitory as well as inductive potential. Three crossover studies in healthy male volunteers investigated the effects of finerenone (20 mg orally) on the pharmacokinetics of the index substrates midazolam (CYP3A4, n = 30), repaglinide (CYP2C8, n = 28) and warfarin (CYP2C9, n = 24).

RESULTS

Finerenone caused direct inhibitory effects on CYP activities in vitro in the rank order CYP2C8, CYP1A1 > CYP3A4 > CYP2C9 and CYP2C19, but not on other major CYP isoforms. Moreover, irreversible inhibition of CYP3A4 was observed. The major metabolites of finerenone demonstrated minor reversible inhibition of CYP1A1, CYP2C9 and CYP3A4 with no hint of time-dependent inhibition of any CYP isoform. Calculations from in vitro data according to regulatory guidelines suggested likely inhibition of CYP2C8 and CYP3A4 in vivo, whereas this was not the case for CYP1A1, CYP2C9 and CYP2C19. Furthermore, finerenone and three of its metabolites were inducers of CYP3A4 in vitro with predicted weak-to-moderate in vivo relevance. Studies in healthy volunteers, prompted by these results, demonstrated no effect of finerenone on CYP isoenzymes for which in vitro data had indicated potential inhibition or induction.

CONCLUSION

Administration of finerenone 20 mg once daily confers no risk of clinically relevant drug-drug interactions with substrates of cytochrome P450 enzymes.

Perspectives from the Innovation and Quality Consortium Induction Working Group on Factors Impacting Clinical Drug-Drug Interactions Resulting from Induction: Focus on Cytochrome 3A Substrates

A recent publication from the Innovation and Quality Consortium Induction Working Group collated a large clinical data set with the goal of evaluating the accuracy of drug-drug interaction (DDI) prediction from in vitro data. Somewhat surprisingly, comparison across studies of the mean- or median-reported area under the curve ratio showed appreciable variability in the magnitude of outcome. This commentary explores the possible drivers of this range of outcomes observed in clinical induction studies. While recommendations on clinical study design are not being proposed, some key observations were informative during the aggregate analysis of clinical data. Although DDI data are often presented using median data, individual data would enable evaluation of how differences in study design, baseline expression, and the number of subjects contribute. Since variability in perpetrator pharmacokinetics (PK) could impact the overall DDI interpretation, should this be routinely captured? Maximal induction was typically observed after 5-7 days of dosing. Thus, when the half-life of the inducer is less than 30 hours, are there benefits to a more standardized study design? A large proportion of CYP3A4 inducers were also CYP3A4 inhibitors and/or inactivators based on in vitro data. In these cases, using CYP3A selective substrates has limitations. More intensive monitoring of changes in area under the curve over time is warranted. With selective CYP3A substrates, the net effect was often inhibition, whereas less selective substrates could discern induction through mechanisms not susceptible to inhibition. The latter included oral contraceptives, which raise concerns of reduced efficacy following induction. Alternative approaches for modeling induction, such as applying biomarkers and physiologically based pharmacokinetic modeling (PBPK), are also considered. SIGNIFICANCE STATEMENT: The goal of this commentary is to stimulate discussion on whether there are opportunities to optimize clinical drug-drug interaction study design. The overall aim is to reduce, understand and contextualize the variability observed in the magnitude of induction across reported clinical studies. A large clinical CYP3A induction dataset was collected and further analyzed to identify trends and gaps. Reporting individual victim PK data, characterizing perpetrator PK and including additional PK assessments for mixed-mechanism perpetrators may provide insights into how these factors impact differences observed in clinical outcomes. The potential utility of biomarkers and PBPK modeling are discussed in considering future directions.

High-content analysis of constitutive androstane receptor (CAR) translocation identifies mosapride citrate as a CAR agonist that represses gluconeogenesis

The constitutive androstane receptor (CAR) plays an important role in hepatic drug metabolism and detoxification but has recently been projected as a potential drug target for metabolic disorders due to its repression of lipogenesis and gluconeogenesis. Thus, identification of physiologically-relevant CAR modulators has garnered significant interest. Here, we adapted the previously characterized human CAR (hCAR) nuclear translocation assay in human primary hepatocytes (HPH) to a high-content format and screened an FDA-approved drug library containing 978 compounds. Comparison of hCAR nuclear translocation results with the Tox21 hCAR luciferase reporter assay database in 643 shared compounds revealed significant overlap between these two assays, with approximately half of hCAR agonists also mediating nuclear translocation. Further validation of these compounds in HPH and/or using published data from literature demonstrated that hCAR translocation exhibits a higher correlation with the induction of hCAR target genes, such as CYP2B6, than the luciferase assay. In addition, some CAR antagonists which repress CYP2B6 mRNA expression in HPH, such as sorafenib, rimonabant, and CINPA1, were found to translocate hCAR to the nucleus of HPH. Notably, both the translocation assay and the luciferase assay identified mosapride citrate (MOS), a gastroprokinetic agent that is known to reduce fasting blood glucose levels in humans, as a novel hCAR activator. Further studies with MOS in HPH uncovered that MOS can repress the expression of gluconeogenic genes and decrease glucose output from hepatocytes, providing a previously unidentified liver-specific mechanism by which MOS modulates blood glucose levels.

Neurokinin-1 receptor antagonists: review of their role for the prevention of chemotherapy-induced nausea and vomiting in adults

Introduction: The addition of neurokinin-1 receptor antagonists (NK₁RAs) to standard prophylaxis of 5-hydroxytryptamine-3 RA (5-HT₃RA) plus dexamethasone more effectively prevents chemotherapy-induced nausea and vomiting (CINV) associated with highly and moderately emetogenic chemotherapy. Areas covered: This review presents the evidence base for the use of oral and intravenous (IV) NK₁RAs, focusing on the pharmacologic and clinical properties as a class, and highlighting differences between agents. A PubMed literature search was conducted from 2000 to 2018. Expert opinion: Adherence to international antiemetic guidelines remains a clinical challenge. Strategies to simplify antiemetic regimens and facilitate their administration may improve compliance and treatment outcomes. The use of fixed-combination antiemetics offers clinical utility, in combining an NK₁RA with a 5-HT₃RA in a single oral dose. The use of long-lasting NK₁RAs and administering CINV prophylaxis closer to the time of chemotherapy may also assist with guideline and treatment compliance, diminishing the need for home-based administration, and potentially reducing resource utilization. The availability of IV and oral formulations of NK₁RAs and NK₁RA-5-HT₃RA fixed combinations offers further utility, particularly for those patients unsuited for oral administration. However, safety considerations with respect to injection site toxicity and hypersensitivity reactions of the new NK₁RA IV formulations deserve close attention.

Efficacy, Tolerability and Pharmacokinetic Impact of Aprepitant in Sarcoma Patients Receiving Ifosfamide and Doxorubicin Chemotherapy: A Randomized Controlled Trial

INTRODUCTION

Aprepitant, a selective neurokinin-1 receptor antagonist approved for prevention of chemotherapy-induced nausea and vomiting (CINV), is an inhibitor of the cytochrome P450 3A4 (CYP3A4) enzyme, which is involved in the clearance of several chemotherapeutic agents. Here we evaluated the efficacy and toxicity of a combination of aprepitant, palonosetron, and dexamethasone as antiemetic prophylaxis in sarcoma patients receiving ifosfamide and doxorubicin chemotherapy, and examined the potential of aprepitant to affect the pharmacokinetics of ifosfamide, which is primarily metabolized by CYP3A4.

METHODS

A total of 108 sarcoma patients were randomly assigned to either the aprepitant group (antiemetic regimen: aprepitant, palonosetron, and dexamethasone) or the control group (antiemetic regimen: palonosetron and dexamethasone). Data on nausea, vomiting, and use of rescue medication were collected, and the primary efficacy end point was the proportion of patients with complete response (CR), defined as no vomiting and no use of rescue therapy during 120 h after initiation of chemotherapy. Tolerability was evaluated on the basis of reported adverse events and laboratory assessments. Blood samples for ifosfamide pharmacokinetic analysis were collected in ten patients.

RESULTS

The percentage of patients achieving CR was significantly higher in the aprepitant group compared with that in the control group in the acute, delay, and overall phase (78.4% vs. 59.3%, 74.5% vs. 48.1%, and 68.6% vs. 37.0%, p < 0.05, respectively). No significant differences of adverse events or hematological toxicity were detected between the two groups. Concomitant administration of aprepitant did not cause any statistically significant changes in ifosfamide pharmacokinetics. Values for aprepitant group vs. control group were as follows: geometric mean of C_max was 119 vs. 120 ng/mL, AUC_0-last was 648 vs. 635 ng h/mL, AUC_0-inf was 681 vs. 668 ng h/mL, plasma clearance was 4.40 vs. 4.49 (L/h/m²), respectively; harmonic means of t_1/2 was 2.11 vs. 2.25 h.

CONCLUSIONS

This study showed that aprepitant in combination with palonosetron and dexamethasone was safe and effectively controlled CINV in sarcoma patients receiving ifosfamide and doxorubicin chemotherapy. Aprepitant may have a low potential to affect the pharmacokinetics of chemotherapeutic agents metabolized by CYP3A4.

Nightmares and hallucinations with aprepitant and opium powder: a suspected drug-drug interaction

Polypharmacy of elderly oncology patients and fragmented medication management are well-known risk factors for drug-drug interactions (DDIs). These interactions can occur among antineoplastic, ongoing chronic treatment(s) and chemotherapy-associated treatments, like antiemetics. Clinically relevant interactions based on enzyme- or transporter-inhibition phenomena of active drugs can increase the frequency of their DDIs. We describe a strongly suspected elderly cancer patient's DDI between aprepitant and opium powder in the context of an irinotecan-based regimen manifested by nightmares and visual hallucinations. We discuss this DDI's hypothetical pharmacological mechanisms and management.

Pharmacokinetic Interactions of Rolapitant With Cytochrome P450 3A Substrates in Healthy Subjects

Rolapitant (Varubi) is a neurokinin-1 receptor antagonist approved for the prevention of chemotherapy-induced nausea and vomiting. Rolapitant is primarily metabolized by the cytochrome P450 3A4 (CYP3A4) enzyme. Unlike other neurokinin-1 receptor antagonists, rolapitant is neither an inhibitor nor an inducer of CYP3A4 in vitro. The objective of this analysis was to examine the pharmacokinetics of rolapitant in healthy subjects and assess drug-drug interactions between rolapitant and midazolam (a CYP3A substrate), ketoconazole (a CYP3A inhibitor), or rifampin (a CYP3A4 inducer). Three phase 1, open-label, drug-drug interaction studies were conducted to examine the pharmacokinetic interactions of orally administered rolapitant with midazolam, rolapitant with ketoconazole, and rolapitant with rifampin. The pharmacokinetic profiles of midazolam and 1-hydroxy midazolam metabolites were essentially unchanged when coadministered with rolapitant, indicating the lack of a clinically relevant inhibition or induction of CYP3A by rolapitant. Coadministration of ketoconazole with rolapitant had no effects on rolapitant maximum concentration and resulted in an approximately 20% increase in the area under the concentration-time curve of rolapitant, suggesting that strong CYP3A inhibitors have minimal inhibitory effects on rolapitant exposure. Repeated administrations of rifampin appeared to reduce rolapitant exposure, resulting in a 33% decrease in maximum concentration and 87% decrease in area under the concentration-time curve from time zero to infinity. Coadministration of rolapitant did not affect the exposure of midazolam. Rifampin coadministration resulted in lower concentrations of rolapitant, and ketoconazole coadministration had no or minimal effects on rolapitant exposure. Rolapitant was safe and well tolerated when coadministered with ketoconazole, rifampin, or midazolam. No new safety signals were reported compared with previous studies of rolapitant.

Influence of aprepitant on the pharmacodynamics and pharmacokinetics of gliclazide in rats and rabbits

Background

Concomitant drug administration is a general phenomenon in patients with chronic diseases such as diabetes mellitus. Among the currently available oral antidiabetic drugs, gliclazide is a commonly prescribed drug considering its multiple benefits in diabetic patients. Aprepitant is a commonly prescribed antiemetic drug which is mainly metabolized by CYP3A4, reported to have modest inductive and inhibitory effects on CYP2C9 and CYP3A4, respectively. Since gliclazide is metabolized by CYP2C9 (major) and CYP3A4 (minor), it is very difficult to predict the influence of aprepitant and its metabolic interaction with gliclazide. Considering the complexity associated with the combination of aprepitant and gliclazide, this study was designed to evaluate the influence of aprepitant on the pharmacodynamics (PD) and pharmacokinetics (PK) of gliclazide in animal models.

Methods

The PD interaction studies were conducted in both rodent (normal and alloxan-induced diabetic rats) and non-rodent (rabbits) animal models (n = 6) while the PK interaction study was conducted in normal rabbits (n = 6). An extrapolated human therapeutic oral dose of gliclazide, aprepitant and their combination were administered to rats and rabbits with 7 days washout between each treatment. For the multiple-dose interaction study, the same groups were administered with an interacting drug (aprepitant) for 7 days and then the combination of aprepitant and gliclazide on the 8th day. From the collected animal blood samples, blood glucose (by Glucose-Oxidase/Peroxidase method), insulin (by ELISA method) and gliclazide concentration levels (by HPLC method) were determined. Non-compartmental PK analysis was conducted by Phoenix WinNonlin software to determine the PK parameters of gliclazide. Statistical analysis was performed by student’s paired t-test.

Results

The pharmacodynamic activity (blood glucose reduction and insulin levels) of gliclazide was significantly (p < 0.05) influenced by aprepitant in normal and diabetic condition without any convulsions in animals. There was a significant (p < 0.05) increase in concentration levels and Area Under the Curve of gliclazide while significant (p < 0.05) decrease in clearance levels of gliclazide in rabbits. The PK interaction with gliclazide is relatively more with the multiple dose treatment of aprepitant over single dose treatment.

Conclusion

In combination, aprepitant significantly influenced the pharmacodynamic activity of gliclazide in animal models. Considering this, care should be taken when this combination is prescribed for the clinical benefit in diabetic patients.

[Chemotherapy-induced nausea and vomiting : Current recommendations for prophylaxis]

The chemotherapy-induced nausea and vomiting (CINV) is one of the most frequent side effects in cytostatic therapy and a profound challenge during the therapy of cancer patients. Therefore, standardized guideline-orientated prophylaxis is essential and a fundamental contribution for the success of treatment. This review summarizes the current recommendations for CINV of the Multinational Association of Supportive Care in Cancer (MASCC) and European Society of Medical Oncology (ESMO), the American Society for Clinical Oncology (ASCO), the National Comprehensive Cancer Network (NCCN) and the S3-guideline Supportive Therapie of the Leitlinienprogramm Onkologie and shall facilitate its use in the daily routine.

NK1 receptor antagonists for depression: Why a validated concept was abandoned

BACKGROUND

NK1 receptor antagonists were abandoned despite antidepressant efficacy in five randomized clinical trials. The loss of confidence may be attributed to the failure of a Phase III clinical program with the NK1 receptor antagonist aprepitant in Major Depression. This review examines how PET receptor occupancy was used to select doses for aprepitant and that these may not have achieved adequate exposure.

METHODS

PubMed, Google Scholar, and FDA databases were searched for articles concerning NK1 receptor antagonists, human PET receptor occupancy and clinical trials in Major Depression.

RESULTS

Antidepressant efficacy was initially demonstrated with three NK1 receptor antagonists, including aprepitant. A nanoparticle formulation of aprepitant was then developed to improve oral bioavailability. In PET studies, doses of 80 and 160mg achieved a high level (~ 90%) of occupancy of NK1 receptors in the human brain and were selected for Phase III. The efficacy of these doses of the nanoparticle formulation may not have been established in depressed patients prior to Phase III, and previous formulations required a dose of 300mg of aprepitant for efficacy. No antidepressant effect of 80 or 160mg of aprepitant was found, and it was concluded that the NK1 antagonist concept was flawed. However, subsequent studies with other compounds showed that a higher level of NK1 receptor occupancy (100%) was required for antidepressant efficacy.

LIMITATIONS

Key data concerning the bioequivalence of different formulations of aprepitant have not been published. The importance of NK1 antagonists for pharmacotherapy of depression and other psychiatric disorders has not been established in clinical practice.

CONCLUSION

Aprepitant may have failed in Phase III because of an inadequate understanding of the relationship between brain NK1 receptor occupancy and clinical response. A validated and novel mechanistic approach to treat depression has been misperceived as ineffective and abandoned. Caution should be exercised in the appropriate use of PET occupancy data to select doses for drug development programs in neuropsychiatry. The relationship between exposure, receptor occupancy and clinical response should be established. A crisis of confidence has followed the failure of this and other programs in neuropsychiatry, with a far reaching and detrimental impact on pharmaceutical research.

Aprepitant and fosaprepitant drug interactions: a systematic review

AIMS

Aprepitant and fosaprepitant, commonly used for the prevention of chemotherapy-induced nausea and vomiting, alter cytochrome P450 activity. This systematic review evaluates clinically significant pharmacokinetic drug interactions with aprepitant and fosaprepitant and describes adverse events ascribed to drug interactions with aprepitant or fosaprepitant.

METHODS

We systematically reviewed the literature to September 11, 2016, to identify articles evaluating drug interactions involving aprepitant/fosaprepitant. The clinical significance of each reported pharmacokinetic drug interaction was evaluated based on the United States Food and Drug Administration guidance document on conducting drug interaction studies. The probability of an adverse event reported in case reports being due to a drug interaction with aprepitant/fosaprepitant was determined using the Drug Interaction Probability Scale.

RESULTS

A total of 4377 publications were identified. Of these, 64 met inclusion eligibility criteria: 34 described pharmacokinetic drug interactions and 30 described adverse events ascribed to a drug interaction. Clinically significant pharmacokinetic interactions between aprepitant/fosaprepitant and bosutinib PO, cabazitaxel IV, cyclophosphamide IV, dexamethasone PO, methylprednisolone IV, midazolam PO/IV, oxycodone PO and tolbutamide PO were identified, as were adverse events resulting from an interaction between aprepitant/fosaprepitant and alcohol, anthracyclines, ifosfamide, oxycodone, quetiapine, selective serotonin reuptake inhibitors/serotonin-norepinephrine reuptake inhibitors and warfarin.

CONCLUSIONS

The potential for a drug interaction with aprepitant and fosaprepitant should be considered when selecting antiemetic therapy.

Recent developments in the clinical pharmacology of rolapitant: subanalyses in specific populations

Knowledge of the involvement of the neurokinin substance P in emesis has led to the development of the neurokinin-1 receptor antagonists (NK-1 RAs) for control of chemotherapy-induced nausea and vomiting (CINV), in combination with serotonin type 3 receptor antagonists and corticosteroids. The NK-1 RA rolapitant, recently approved in oral formulation, has nanomolar affinity for the NK-1 receptor, as do the other commercially available NK-1 RAs, aprepitant and netupitant. Rolapitant is rapidly absorbed and has a long half-life in comparison to aprepitant and netupitant. All three NK-1 RAs undergo metabolism by cytochrome P450 (CYP) 3A4, necessitating caution with the concomitant use of CYP3A4 inhibitors, but in contrast to aprepitant and netupitant, rolapitant does not inhibit or induce CYP3A4. However, rolapitant is a moderate inhibitor of CYP2D6, and concomitant use with CYP2D6 substrates with narrow therapeutic indices should be avoided. Aprepitant, netupitant, and rolapitant have all demonstrated efficacy in the control of delayed CINV in patients receiving moderately and highly emetogenic chemotherapy in randomized controlled trials, including over multiple cycles of chemotherapy. We reviewed recent post hoc analyses of clinical trial data demonstrating that rolapitant is efficacious in the control of CINV in patient populations with specific tumor types, namely, breast cancers, gastrointestinal/colorectal cancers, and lung cancers. In addition, we show that rolapitant has efficacy in the control of CINV in specific age groups of patients receiving chemotherapy (<65 and ≥65 years of age). Overall, the safety profile of rolapitant in these specific patient populations was consistent with that observed in primary analyses of phase 3 trials.

Considerations from the IQ Induction Working Group in Response to Drug-Drug Interaction Guidance from Regulatory Agencies: Focus on Downregulation, CYP2C Induction, and CYP2B6 Positive Control

The European Medicines Agency (EMA), the Pharmaceutical and Medical Devices Agency (PMDA), and the Food and Drug Administration (FDA) have issued guidelines for the conduct of drug-drug interaction studies. To examine the applicability of these regulatory recommendations specifically for induction, a group of scientists, under the auspices of the Drug Metabolism Leadership Group of the Innovation and Quality (IQ) Consortium, formed the Induction Working Group (IWG). A team of 19 scientists, from 16 of the 39 pharmaceutical companies that are members of the IQ Consortium and two Contract Research Organizations reviewed the recommendations, focusing initially on the current EMA guidelines. Questions were collated from IQ member companies as to which aspects of the guidelines require further evaluation. The EMA was then approached to provide insights into their recommendations on the following: 1) evaluation of downregulation, 2) in vitro assessment of CYP2C induction, 3) the use of CITCO as the positive control for CYP2B6 induction by CAR, 4) data interpretation (a 2-fold increase in mRNA as evidence of induction), and 5) the duration of incubation of hepatocytes with test article. The IWG conducted an anonymous survey among IQ member companies to query current practices, focusing specifically on the aforementioned key points. Responses were received from 19 companies. All data and information were blinded before being shared with the IWG. The results of the survey are presented, together with consensus recommendations on downregulation, CYP2C induction, and CYP2B6 positive control. Results and recommendations related to data interpretation and induction time course will be reported in subsequent articles.

Emesis and nausea related to single agent trabectedin in ovarian cancer patients: a sub-study of the MITO15 project

The MITO 15 was a prospective, single-arm trial, evaluating trabectedin monotherapy in patients with recurrent ovarian cancer (OC) who were BRCA mutation-carriers or had a BRCAness phenotype. It is largely reported that trabectedin may induce nausea and vomiting but the real emetogenic potential of the drug, in the different schedules, has never been fully described; furthermore, OC patients are known to have an enhanced risk of developing nausea and vomiting due to female gender, abdominal spreading of the disease, and major surgery experienced by most of them. We thought to carry on a sub-study in the MITO 15 context focused on chemotherapy-induced nausea and vomiting (CINV) associated with trabectedin single agent. For all patients enrolled in the trial, we evaluated the antiemetic regimen at the first cycle, acute and delayed CINV, any rescue therapy, any change in the prophylactic antiemetic regimen, and the potential relationship between dexamethasone dosage and incidence of CINV. Overall, our findings were consistent with literature and confirmed that trabectedin can be classified as moderately emetogenic. We observed slightly higher rates of both nausea and vomiting compared to previous experiences with trabectedin monotherapy, probably due to intrinsic features of our population: all females and suffering from ovarian cancer. It seems that in preventing acute CINV, the combination of three drugs was more effective than the doublet; however, the difference did not reach statistical significance; further studies are required to verify such hypothesis. Given the extreme heterogeneity of the antiemetic regimens used, it appears that a standard antiemetic protocol does not exist and more specific guidelines for clinicians are needed.

A Model for Predicting the Interindividual Variability of Drug-Drug Interactions

Pharmacokinetic drug-drug interactions are frequently characterized and quantified by an AUC ratio (Rauc). The typical value of the AUC ratio in case of cytochrome-mediated interactions may be predicted by several approaches, based on in vitro or in vivo data. Prediction of the interindividual variability of Rauc would help to anticipate more completely the consequences of a drug-drug interaction. We propose and evaluate a simple approach for predicting the standard deviation (sd) of Ln(Rauc), a metric close to the interindividual coefficient of variation of Rauc. First, a model was derived to link sd(Ln Rauc) with the substrate fraction metabolized by each cytochrome and the potency of the interactors, in case of induction or inhibition. Second, the parameters involved in these equations were estimated by a Bayesian hierarchical model, using the data from 56 interaction studies retrieved from the literature. Third, the model was evaluated by several metrics based on the fold prediction error (PE) of sd(Ln Rauc). The median PE was 0.998 (the ideal value is 1) and the interquartile range was 0.96-1.03. The PE was in the acceptable interval (0.5 to 2) in 52 cases out of 56. Fourth, a surface plot of sd(Ln Rauc) as a function of the characteristics of the substrate and the interactor has been built. The minimal value of sd(Ln Rauc) was about 0.08 (obtained for Rauc = 1) while the maximal value, 0.7, was obtained for interactions involving highly metabolized substrates with strong interactors.

Corticosteroids, the oldest agent in the prevention of chemotherapy-induced nausea and vomiting: What about the guidelines?

Chemotherapy-induced nausea and vomiting (CINV) remains one of the most disturbing side effects of cancer treatment. Research in antiemetic therapy has progressed gradually since the early eighties, and the development of antiemetic agents continues. This review focuses on the current management of CINV based on the most recent guidelines, and adherence to the latter is examined more carefully. Setrons (5HT3 receptor antagonists), corticosteroids, and NK-1 receptor antagonists are the cornerstones of antiemetic therapy. Corticosteroids are one of the oldest agents in the prevention of CINV. They are highly effective, increase the effect of other antiemetic agents, and are cost-effective. The latest developed 5HT3 receptor antagonist palonosetron led to an update of the guidelines of CINV. Other types include benzodiazepines, cannabinoids, and olanzapine. Various factors contribute to the overall risk of developing CINV, such as patient characteristics, emetogenic potency of the chemotherapeutic agents, and correct prevention of CINV. Current guidelines determine which is the right preventive regimen for each cancer patient at risk for experiencing CINV. Adherence to these guidelines and implementation in daily practice seem to be below the optimal level. In Belgium, authorities use the guidelines as a base for reimbursement and this has increased the level of implementation.

Assessment of Drug-Drug Interaction between Warfarin and Aprepitant and Its Effects on PT-INR of Patients Receiving Anticancer Chemotherapy

Aprepitant is a known inducer of CYP2C9, the main warfarin-metabolizing enzyme. Consequently, co-administration of these two drugs may result in reduction of the anticoagulation activity of warfarin. However, the nature and degree of time-dependent changes in prothrombin time international normalized ratio (PT-INR) after aprepitant and warfarin co-treatment in patients receiving anticancer chemotherapy has not been elucidated. We retrospectively examined the changes in warfarin dose, PT-INR, and warfarin sensitivity index (WSI; average of PT-INR value/average of daily warfarin dose) during four weeks, i.e., one week before and three weeks after aprepitant administration. The mean and standard deviation values of WSI for one week before and one, two, and three weeks after the beginning of aprepitant administration were 0.51±0.22 (1.00, n=34), 0.74±0.30 (1.53±0.59, n=30), 0.38±0.15 (0.82±0.22, n=28), and 0.46±0.29 (0.87±0.23, n=24), respectively. Values in parentheses represent relative changes versus WSI of one week before and number of subjects. Although the mean value of WSI significantly increased one week after aprepitant administration compared to that at one week before the administration, it in turn significantly decreased two weeks after compared to one week before (paired t-test, p<0.05 after Bonferoni correction). In patients taking warfarin, PT-INR should be carefully monitored for at least two weeks after the beginning of aprepitant administration because it may fluctuate with both aprepitant and chemotherapy during this period.

Drug interactions with aprepitant or fosaprepitant: Review of literature and implications for clinical practice

Purpose Aprepitant and its parenteral formulation fosaprepitant are widely used for the prevention of chemotherapy-induced nausea and vomiting. Aprepitant exerts modest inhibitory effect on CYP3A4 and modest inductive effect on CYP2C9 substrates such as some antineoplastics and multiple other medications. This article is aimed to provide pharmacists and other healthcare professionals with an updated summary of drug-drug interactions of aprepitant/fosaprepitant and implications for clinical practice. Method We reviewed publications reporting drug-drug interactions between aprepitant/fosaprepitant and other medications. Results Coadministration of aprepitant with antineoplastics or opiods may result in significant elevations in the serum levels of the agents metabolized via CYP3A4, with the best documentation for cyclophosphamide, ifosfamide, erlotinib and oxycodone. These alterations did not translate into adverse outcomes and/or necessitate dosing adjustments. The levels of warfarin were significantly decreased by aprepitant requiring prolonged monitoring after discontinuation of aprepitant. Among direct oral anticoagulants, a theoretical interaction between aprepitant and rivaroxaban or apixaban exists. Interactions between aprepitant and quetiapine or diltiazem or sirolimus required dose reductions to avoid adverse outcomes. The intravenous route had a weaker inhibitory effect on CYP3A4 than the oral pathway. Conclusion The evidence on drug interactions of aprepitant with other medications is limited, and the impact on therapeutic outcomes remains to be determined. The intravenous regimen may be a preferred option. As utilization of aprepitant is expanding, practitioners and patients need to be educated about the potential for drug interactions and a need for careful monitoring of patients concurrently receiving aprepitant and CYP2C9 or CYP3A4 substrates, especially those with a narrow therapeutic window.

Pharmacokinetic interaction between pazopanib and cisplatin regimen

PURPOSE

A phase I study combining daily oral pazopanib and cisplatin (given iv every 3 weeks) was performed in order to determine the maximum tolerated dose of both drugs in combination. Pharmacokinetic interactions were evaluated.

METHODS

Plasma pazopanib and ultrafilterable cisplatin concentrations were obtained in 32 patients treated according to four levels of dose corresponding to 200, 400 or 600 mg daily dose of pazopanib and 60 or 75 mg/m(2) of cisplatin. Two sequences of treatment were performed in order to explore any interaction of cisplatin on pazopanib pharmacokinetics and inversely. Data were analyzed using the NONMEM program.

RESULTS

Maximum tolerated dose was 400 mg of pazopanib and 75 mg/m(2) of cisplatin. Mean (CV % for inter-individual variability) cisplatin clearance was 10.3 L/h (33.2 %) and appeared not to be influenced by pazopanib. However, pazopanib pharmacokinetics was significantly modified by the cisplatin regimen. Mean (CV %) of oral pazopanib clearance was 0.66 L/h (55 %) at Day 0 (before cisplatin administration), 24.8 % lower at Day 1 and 32.9 % lower at Day 2. The interaction is less likely to be due to cisplatin than to a competitive inhibition of pazopanib metabolism and efflux by aprepitant, an antiemetic drug systematically administered with cisplatin. The plasma pazopanib exposures observed at Day 0 with a 400 mg dose were similar to those observed at the recommended dose of pazopanib in monochemotherapy (800 mg) during the first-in-man phase 1 study.

CONCLUSION

The observed pazopanib plasma overexposure probably contributed to the poor tolerance encountered during this phase 1 study.

Vatalanib population pharmacokinetics in patients with myelodysplastic syndrome: CALGB 10105 (Alliance)

AIMS

Vatalanib is an oral anti-angiogenesis agent that inhibits vascular endothelial growth factor receptor tyrosine kinases, which in patients showed auto induction of metabolism and variability in pharmacokinetic (PK) disposition. The objective was to characterize the population PK and time-dependent change in vatalanib clearance and assess exposure-toxicity relationship in patients with myelodysplastic syndrome (MDS).

METHODS

This was an open-label phase II study of vatalanib in MDS patients receiving 750-1250 mg once daily in 28-day cycles. Serial blood samples were obtained and plasma vatalanib concentrations measured by HPLC. Population PK analysis was performed using nonmem 7.2 with FO estimation since FOCE failed. The final model was evaluated using goodness-of-fit plots, bootstrap analysis, and visual predictive check.

RESULTS

Pharmacokinetic data were complete for 137 patients (86 M, 51 F), of median age 70 years (range 20-91). A one-compartment model with lagged first-order absorption and time-dependent change in oral clearance was fitted to the vatalanib plasma concentration versus time data. The population means for pre-induction and post-induction oral clearance were 24.1 l h(-1) (range: 9.6-45.5) and 54.9 l h(-1) (range: 39.8-75.6), respectively. The apparent oral clearance increased 2.3-fold, (range: 1.7-4.1-fold) from first dose to steady state. Our data did not identify a significant relationship of the predefined covariates with vatalanib pharmacokinetics, although power to detect such a relationship was limited.

CONCLUSIONS

Vatalanib pharmacokinetics were highly variable and the extent of auto induction was not determined to correlate with any of the pre-defined covariates.

In vitro glucuronidation of aprepitant: a moderate inhibitor of UGT2B7

1. Aprepitant, an oral antiemetic, commonly used in the prevention of chemotherapy-induced nausea and vomiting, is primarily metabolized by CYP3A4. Aprepitant glucuronidation has yet to be evaluated in humans. The contribution of human UDP-glucuronosyltransferase (UGT) isoforms to the metabolism of aprepitant was investigated by performing kinetic studies, inhibition studies and correlation analyses. In addition, aprepitant was evaluated as an inhibitor of UGTs. 2. Glucuronidation of aprepitant was catalyzed by UGT1A4 (82%), UGT1A3 (12%) and UGT1A8 (6%) and Kms were 161.6 ± 15.6, 69.4 ± 1.9 and 197.1 ± 28.2 µM, respectively. Aprepitant glucuronidation was significantly correlated with both UGT1A4 substrates anastrazole and imipramine (rs = 0.77, p < 0.0001 for both substrates; n = 44), and with the UGT1A3 substrate thyroxine (rs = 0.58, p < 0.0001; n = 44). 3. We found aprepitant to be a moderate inhibitor of UGT2B7 with a Ki of ∼10 µM for 4-MU, morphine and zidovudine. Our results suggest that aprepitant can alter clearance of drugs primarily eliminated by UGT2B7. Given the likelihood for first-pass metabolism by intestinal UGT2B7, this is of particular concern for oral aprepitant co-administered with oral substrates of UGT2B7, such as zidovudine and morphine.

Drug-drug interaction profile of components of a fixed combination of netupitant and palonosetron: Review of clinical data

Neurokinin-1 (NK₁) receptor antagonists (RAs) are commonly coadministered with serotonin (5-HT₃) RAs (e.g. palonosetron (PALO)) to prevent chemotherapy-induced nausea/vomiting. Netupitant/palonosetron (NEPA), an oral fixed combination of netupitant (NETU)—a new NK₁ RA—and PALO, is currently under development. In vitro data suggest that NETU inhibits CYP3A4 and is a substrate for and weak inhibitor of P-glycoprotein (P-gp). This review evaluates potential drug–drug interactions between NETU or NEPA and CYP3A4 substrates/inducers/inhibitors or P-gp substrates in healthy subjects. Pharmacokinetic (PK) parameters were evaluated for each drug when NETU was coadministered with PALO (single doses) and when single doses of NETU or NEPA were coadministered with CYP3A4 substrates (erythromycin (ERY), midazolam (MID), dexamethasone (DEX), or oral contraceptives), inhibitors (ketoconazole (KETO)), or inducers (rifampicin (RIF)), or a P-gp substrate (digoxin (DIG)). Results showed no relevant PK interactions between NETU and PALO. Coadministration of NETU increased MID and ERY exposure and significantly increased DEX exposure in a dose-dependent manner; NETU exposure was unaffected. NEPA coadministration had no clinically significant effect on oral contraception, although levonorgestrel exposure increased. NETU exposure increased after coadministration of NEPA with KETO and decreased after coadministration with RIF; PALO exposure was unaffected. NETU coadministration did not influence DIG exposure. In conclusion, there were no clinically relevant interactions between NETU and PALO, or NEPA and oral contraceptives (based on levonorgestrel and ethinylestradiol exposure). Coadministration of NETU or NEPA with CYP3A4 inducers/inhibitors/substrates should be done with caution. Dose reduction is recommended for DEX. Dose adjustments are not needed for NETU coadministration with P-gp substrates.

Inter-patient variability in docetaxel pharmacokinetics: A review

Docetaxel is a frequently used chemotherapeutic agent in the treatment of solid cancers. Because of the large inter-individual variability (IIV) in the pharmacokinetics (PK) of docetaxel, it is challenging to determine the optimal dose in individual patients in order to achieve optimal efficacy and acceptable toxicity. Despite the established correlation between systemic docetaxel exposure and efficacy, the precise factors influencing docetaxel PK are not yet completely understood. This review article highlights currently known factors that influence docetaxel PK, and focusses on those that are clinically relevant. For example, liver impairment should be taken into account when calculating docetaxel dosages as this may decrease docetaxel clearance. In addition, drug-drug interactions may be of distinct clinical importance when using docetaxel. Particularly, drugs strongly inhibiting CYP3A4 such as ketoconazole should not be concurrently administered without dose modification, as they may decrease the clearance of docetaxel. Gender, castration status, and menopausal status might be of importance as potential factors influencing docetaxel PK. The role of pharmacogenetics in predicting docetaxel PK is still limited, since no polymorphisms of clinical importance have yet been established.

Trabectedin: Supportive care strategies and safety profile

Trabectedin is an approved antineoplastic agent for the treatment of adult patients with advanced soft tissue sarcomas or in combination with pegylated liposomal doxorubicin (PLD) in patients with relapsed platinum sensitive ovarian cancer. The mechanism of action is still not fully understood but many typical side effects seen with other chemotherapy drugs are less common, mild or unreported. Although this apparent favorable safety profile suggests a well-tolerated and manageable therapeutic option in the palliative care setting, trabectedin does have specific adverse side effects which can be hazardous for individual patients. The most commonly observed toxicities with trabectedin include neutropenia, nausea, vomiting, and increases in liver transaminases, anemia, fatigue, thrombocytopenia, anorexia and diarrhea. However, for most patients the appropriate use of supportive care strategies can reduce or overcome these side effects. We present a concise review of the safety data of trabectedin with the corresponding overview of the supportive care strategies.

Angiotensin Converting Enzyme Inhibitors (ACEI) and doxorubicin pharmacokinetics in women receiving adjuvant breast cancer treatment

Purpose

Doxorubicin (DOX) chemotherapy can cause cardiac complications. Angiotensin converting enzyme inhibitors (ACEI) may protect against these complications. We performed a pharmacokinetics (PK) study to determine whether DOX levels are altered in the presence of ACEI.

Methods

In this randomized, cross-over, single-blinded drug-drug interaction study, 19 women with breast cancer prescribed DOX and cyclophosphamide every 14 days received one cycle of DOX chemotherapy with ACEI enalapril 10 mg daily and another cycle of DOX with placebo. Blood samples for DOX and doxorubicinol were drawn at baseline, 0.5, 1.0, 2.0, 4.0, 24.0 and 48.0 hours after infusion with and without ACEI enalapril. Correlative laboratories were also obtained. PK data was analyzed using non compartmental methods and DOX and doxorubicinol area under the curve (AUC) 0 to infinity, Cmax and half-life were estimated. Paired t-tests were used to determine whether DOX and its metabolite were altered with the use of enalapril (P < 0.05).

Results

17 women (median age 45 years) received 60 mg/m2 DOX every two weeks for four cycles. Mean (SD) AUC0- ∞ for DOX and doxorubicinol with enalapril exposure was 1185.56 (44.64) hr*ng/ml and 1040 (80.6) hr*ng/ml, respectively. AUC0- ∞ for DOX and doxobubicinol without enalapril was 1167.73 (45.26) hr*ng/ml and 1056.32 (92.03) hr*ng/ml, respectively. There is no interaction between DOX and enalapril. Enalapril was tolerated (33% grade 1 dizziness).

Conclusion

ACEI, enalapril, does not appear to alter the PK of DOX. Ongoing efforts to determine the effectiveness of ACEI as a cardioprotective agent in women receiving DOX chemotherapy should be continued.

NK-1 Antagonists and Itch

Substance P (SP) is an important mediator of pro-inflammatory mechanisms in the skin. It targets multiple cells such as keratinocytes, mast cells, and fibroblasts which are involved in the cutaneous generation of pruritus. This suggests that SP is an interesting target for therapy. In fact, in recent case reports and case series, SP antagonists demonstrated a significant antipruritic effect in acute and chronic pruritus such as drug-induced pruritus, paraneoplastic pruritus, prurigo nodularis, cutaneous T-cell lymphoma, and brachioradial pruritus.

Two cases of fatal encephalopathy related to Ifosfamide: an adverse role of aprepitant?

Ifosfamide is used in the treatment of sarcomas and other tumors. It sometimes provokes encephalopathy, which is a serious complication even if it is usually reversible within 48-72 h after drug cessation. Ifosfamide is required to be activated by hepatic cytochrome P450 (CYP), especially the 3A4 subtype, leading to 4-hydroxy-ifosfamide. Ifosfamide is also converted by CYP3A4 to inactive but neurotoxic metabolites. Aprepitant is a neurokinin-1 receptor antagonist that is a potent antiemetic used in combination with 5-HT3 antagonists and corticosteroids. Aprepitant has an inhibitory effect, as well as a possible inductive effect, on CYP3A4. Since ifosfamide and aprepitant are both substrates of CYP3A4, a pharmacokinetic interaction could result in secondary effects such as the potentialization of neurological side effects. In this report, we describe 2 cases of fatal encephalopathy in patients who have received both ifosfamide and aprepitant, and we discuss the mechanisms that could be involved. Our observations draw attention to the fact that aprepitant must be avoided, or at least used with caution, in patients who are receiving ifosfamide due to the risk of severe neurological side effects.

Aprepitant for the prevention of nausea and vomiting associated with chemotherapy and postoperative recovery

Chemotherapy-induced nausea and vomiting (CINV) and postoperative nausea and vomiting (PONV) can negatively impact patient quality of life, functional performance and activities of daily living. Although the development of serotonin receptor antagonists has greatly improved the control of acute emesis, delayed CINV remains a significant clinical issue. Aprepitant (Emend(®)) is the first commercially available drug from a new class of agents, the neurokinin-1 receptor antagonists. Elucidation of its mechanism of action has produced a greater understanding of the pathophysiology of nausea and vomiting. Oral aprepitant, in combination with a selective serotonin (5-HT3) receptor antagonist and corticosteroids, is indicated for the prevention of acute and delayed nausea and vomiting associated with highly and moderately emetogenic chemotherapy in adults. Aprepitant alone or in combination only with dexamethasone does not optimally control acute emesis compared with triple combination therapy. By contrast, aprepitant as monotherapy is indicated for the prevention of PONV. Aprepitant represents an emerging class of agents and its addition to standard therapy provides an advanced benefit in the prevention and treatment of CINV and PONV. Investigations of aprepitant for other indications are ongoing.

Novel continuous flow technology for the development of a nanostructured aprepitant formulation with improved pharmacokinetic properties

The oral bioavailability of Aprepitant is limited by poor dissolution of the compound in the gastrointestinal tract which is more prominent in the fasted state resulting in significant positive food effect. Due to the low aqueous solubility of the active substance the product development has been focused on decreasing the particle size of the active compound down to the submicron range in order to overcome this disadvantageous pharmacokinetic property. The marketed drug consisting of wet-milled nanocrystals exhibits significantly higher oral bioavailability in the fasted state and reduced food effect when compared to the unformulated compound. We have developed a novel process for the production of a nanostructured Aprepitant formulation in which the generation of the nanosized particles takes place at molecular level. The process relies on controlled continuous flow precipitation of the compound from its solution in the presence of stabilizers. The precise control of the production parameters (mixing geometry, flow rates, temperature, etc.) allows to tailor the physicochemical properties and biological performance of the active compound. We have prepared a novel nanostructured Aprepitant formulation using this method and compared its physicochemical and pharmacokinetic properties with the reference compound and the marketed nanoformula. We found that our method produces a stable amorphous solid form comprising novel nanostructured particles having a particle size of less than 100 nm with instantaneous redispersibility characteristics and improved apparent solubility and permeability. In vivo beagle dog pharmacokinetic studies showed that the novel formula exhibited greatly improved pharmacokinetic characteristics when compared to the reference compound, while serum blood concentrations for the nanostructured formula and the wet-milled formula were similar. The marked food effect observed for the reference compound was practically eliminated by our formulation method. These results indicate that the novel continuous flow precipitation technology is a suitable tool to prepare nanostructured formulations with similar, or even superior in vitro and in vivo characteristics when compared to the industrial standard milling technology.

International antiemetic guidelines on chemotherapy induced nausea and vomiting (CINV): content and implementation in daily routine practice

Over the past decades major improvements in the management of chemotherapy induced nausea and vomiting (CINV) were obtained. With the correct use of antiemetic drugs, CINV can be prevented in almost 70%, and even up to, 80% of patients. Treatment guidelines enable physicians to integrate the latest clinical research into their daily practice. The large volume of rapidly evolving clinical data has been summarised and incorporated into treatment recommendations by well-known and reliable institutions. These organisations include the Multinational Association of Supportive Care in Cancer (MASCC), the European Society of Medical Oncology (ESMO), the American Society for Clinical Oncology (ASCO), and National Comprehensive Cancer Network (NCCN). However, despite the availability of these guidelines, there is an emerging evidence that adherence to, and implementation of, treatment recommendations is less than optimal. This review will especially focus on the content of the current antiemetic guidelines and will address the important question of how these guidelines are implemented in routine practice.

2-[(3aR,4R,5S,7aS)-5-{(1S)-1-[3,5-bis(trifluoromethyl)phenyl]-2-hydroxyethoxy}-4-(2-methylphenyl)octahydro-2H-isoindol-2-yl]-1,3-oxazol-4(5H)-one: a potent human NK1 receptor antagonist with multiple clearance pathways

Hydroisoindoline 2 has been previously identified as a potent, brain-penetrant NK1 receptor antagonist with a long duration of action and improved profile of CYP3A4 inhibition and induction compared to aprepitant. However, compound 2 is predicted, based on data in preclinical species, to have a human half-life longer than 40 h and likely to have drug-drug-interactions (DDI), as 2 is a victim of CYP3A4 inhibition caused by its exclusive clearance pathway via CYP3A4 oxidation in humans. We now report 2-[(3aR,4R,5S,7aS)-5-{(1S)-1-[3,5-bis(trifluoromethyl)phenyl]-2-hydroxyethoxy}-4-(2-methylphenyl)octahydro-2H-isoindol-2-yl]-1,3-oxazol-4(5H)-one (3) as a next generation NK1 antagonist that possesses an additional clearance pathway through glucuronidation in addition to that via CYP3A4 oxidation. Compound 3 has a much lower propensity for drug-drug interactions and a reduced estimated human half-life consistent with once daily dosing. In preclinical species, compound 3 has demonstrated potency, brain penetration, and a safety profile similar to 2, as well as excellent pharmacokinetics.

Treatment of chemotherapy-induced nausea and vomiting

BACKGROUND

Recent improvements in medical oncology include both development of anticancer and supportive therapy. Serotonin receptor antagonists were introduced in clinical practice 20 years ago. Since then, the prevention and treatment of chemotherapy-induced nausea and vomiting allows continuing efficacious chemotherapy that earlier had to be stopped sometimes for intolerance.

AIM

This anniversary review summarises the current antiemetic arsenal focussing on the most potent antiemetic drugs such as serotonin and substance P receptor antagonists.

RESULT

Antiemetic treatment improves quality of life under chemotherapy and contributes to the survival benefit as well. In spite of the use of these new drugs, a significant number of patients still experience nausea and vomiting. Special complications like delayed emesis can be alleviated by combination therapies.

CONCLUSION

Prevention and optimal management of chemotherapy-induced nausea and vomiting should be a goal for most patients receiving emetogenic chemotherapy.

Effect of netupitant, a highly selective NK₁ receptor antagonist, on the pharmacokinetics of midazolam, erythromycin, and dexamethasone

PURPOSE

Netupitant is a new highly selective neurokinin-1 receptor antagonist being studied for the prevention of nausea and vomiting in patients undergoing chemotherapy. In vitro studies suggest that netupitant inhibits the cytochrome P-450 isoenzyme 3A4 (CYP3A4). Because netupitant may be used with a variety of drugs, which may be substrates of CYP3A4, two studies were designed to establish the potential risk for drug-drug interaction with three different CYP3A4 substrates: midazolam, erythromycin, and dexamethasone.

METHODS

Both trials were three-period crossover studies performed in healthy subjects. In the first study, 20 subjects received netupitant and either midazolam or erythromycin. In the second study, 25 subjects received netupitant and dexamethasone. Serial blood samples were collected over the course of the two studies and pharmacokinetic parameters were determined for all analytes.

RESULTS

Netupitant, by inhibiting the CYP3A4, increased the C max and AUCinf of midazolam by 40 and 144 %, respectively, and the C max and AUCinf of erythromycin by 30 %. Netupitant was shown to increase the exposure to dexamethasone in a dose-dependent manner with the mean increase in AUC and C max by 72 and 11 %, respectively, on day 1 and by 138 and 75 %, respectively, on day 4 when co-administered with 300 mg of netupitant.

CONCLUSIONS

The results of these studies suggest that netupitant is a moderate inhibitor of CYP3A4 and therefore, co-administration with drugs that are substrates of CYP3A4 may require dose adjustments. Treatments were well tolerated in both studies.

Effect of a Triphasic Oral Contraceptive on Drug-Metabolizing Enzyme Activity as Measured by the Validated Cooperstown 5+1 Cocktail

The effects of a common oral contraceptive preparation on the activity of 7 drug-metabolizing enzymes were investigated using the validated Cooperstown 5+1 Cocktail. In a randomized crossover fashion, 10 premenopausal women received caffeine, dextromethorphan, omeprazole, intravenous midazolam, and warfarin + vitamin K with and without a triphasic oral contraceptive (ethinyl estradiol 35 microg) and varying doses of daily norgestimate (0.18, 0.215, and 0.25 mg). Bioequivalence testing showed nonequivalence in drug versus no-drug treatment on the activity of drug-metabolizing enzymes (as reflected by metabolite ratios following probe drug administration); the activity of CYP1A2, CYP2C19, and NAT-2 decreased following the oral contraceptive, whereas the activity of CYP2C9 and CYP2D6 increased. No effects on xanthine oxidase or hepatic CYP3A were seen. Application of a non-parametric statistical testing approach revealed a significant difference only for CYP1A2 and CYP2C19. This triphasic oral contraceptive may have a clinically significant effect on the activity of some drug-metabolizing enzymes.

Use of high-dose cisplatin with aprepitant in an outpatient setting

Chemotherapy-induced nausea and vomiting (CINV) and nephrotoxicity are adverse events induced by cisplatin administration. These effects can be reduced by treatment regimens with low-dose cisplatin, but high-dose cisplatin is still used. In Japan, high-dose cisplatin is usually administered in an inpatient setting to permit management of CINV. However, with use of new-generation antiemetic agents such as aprepitant, CINV and nephrotoxicity are controllable in an outpatient setting. Here, we discuss issues related to the management of high-dose cisplatin administration in outpatients. Grade 2 or worse CINV induced by high-dose cisplatin occurs in more than 40% of patients without treatment with aprepitant, but is controllable by administration of a 5-HT3 receptor antagonist, steroids and aprepitant. Moreover, prevention of CINV using these drugs is cost-effective, since outpatient settings have advantages with regard to health economics and patient quality of life. These findings suggest that shifting high-dose cisplatin administration to the outpatient setting may be achieved with co-administration of aprepitant. Available facilities and the status of the patient should be considered when selecting whether an outpatient setting is suitable for administration of cisplatin, but the use of aprepitant and adequate oral hydration should allow use of cisplatin in this setting.