Pharmacokinetics, metabolism and excretion of intravenous [l4C]-palonosetron in healthy human volunteers

Palonosetron as prophylaxis for post-discharge nausea and vomiting: a prospective, randomised, double-blind, placebo-controlled trial in ambulatory surgery

BACKGROUND

Approximately 25% of ambulatory surgery patients experience post-discharge nausea and vomiting (PDNV). We aimed to investigate whether palonosetron, a long-acting anti-emetic, decreases the incidence of PDNV in high-risk patients.

METHODS

In this prospective, randomised, double-blind, placebo-controlled trial, 170 male and female patients undergoing ambulatory surgery under general anaesthesia, with a high predicted risk for PDNV, were randomised to receive either palonosetron 75 μg i.v. (n=84) or normal saline (n=86) before discharge. During the first 3 postoperative days (PODs), we measured outcomes using a patient questionnaire. The primary outcome was the incidence of a complete response (no nausea, vomiting, or use of rescue medication) until POD 2. Secondary outcomes included the incidence of PDNV each day until POD 3.

RESULTS

The incidence of a complete response until POD 2 was 48% (n=32) in the palonosetron group and 36% (n=25) in the placebo group (odds ratio 1.69 [95% confidence interval: 0.85-3.37]; P=0.131). No significant difference in the incidence of PDNV was observed between the two groups on the day of surgery (47% vs 56%; P=0.31). Significant differences in the incidence of PDNV were found on POD 1 (18% vs 34%; P=0.033) and POD 2 (9% vs 27%; P=0.007). No differences were observed on POD 3 (15% vs 13%; P=0.700).

CONCLUSIONS

Compared with placebo, palonosetron did not reduce the overall incidence of PDNV up to POD 2. The lower incidence of PDNV on POD 1 and POD 2 in the palonosetron group requires further investigation.

CLINICAL TRIAL REGISTRATION

EudraCT 2015-003956-32.

Postoperative Nausea and Vomiting in Female Patients Undergoing Breast and Gynecological Surgery: A Narrative Review of Risk Factors and Prophylaxis

Postoperative nausea and vomiting (PONV) have been widely studied as a multifactorial entity, being of female gender the strongest risk factor. Reported PONV incidence in female surgical populations is extremely variable among randomized clinical trials. In this narrative review, we intend to summarize the incidence, independent predictors, pharmacological and non-pharmacological interventions for PONV reported in recently published clinical trials carried out in female patients undergoing breast and gynecologic surgery, as well as the implications of the anesthetic agents on the incidence of PONV. A literature search of manuscripts describing PONV management in female surgical populations (breast surgery and gynecologic surgery) was carried out in PubMed, MEDLINE, and Embase databases. Postoperative nausea and vomiting incidence were highly variable in patients receiving placebo or no prophylaxis among RCTs whereas consistent results were observed in patients receiving 1 or 2 prophylactic interventions for PONV. Despite efforts made, a considerable number of female patients still experienced significant PONV. It is critical for the anesthesia provider to be aware that the coexistence of independent risk factors such as the level of sex hormones (pre- and postmenopausal), preoperative anxiety or depression, pharmacogenomic pleomorphisms, and ethnicity further enhances the probability of experiencing PONV in female patients. Future RCTs should closely assess the overall risk of PONV in female patients considering patient- and surgery-related factors, and the level of compliance with current guidelines for prevention and management of PONV.

Pharmacokinetic profile and safety of intravenous NEPA, a fixed combination of fosnetupitant and palonosetron, in cancer patients: Prevention of chemotherapy-induced nausea and vomiting associated with highly emetogenic chemotherapy

NEPA is the fixed combination antiemetic composed of the neurokinin-1 receptor antagonist netupitant and the 5-hydroxytryptamine-3 receptor antagonist palonosetron. The intravenous (i.v.) formulation of NEPA (fosnetupitant 235 mg/palonosetron 0.25 mg) was developed to enhance the convenience of NEPA administration. In a phase 3 study, i.v. NEPA showed acceptable safety with low risk for injection-site reactions. This study evaluated the pharmacokinetics and safety of i.v. NEPA in cancer patients. This was a single-center, single-dose phase 1 study in patients receiving highly emetogenic chemotherapy. Patients received a 30-min infusion of i.v. NEPA plus oral dexamethasone (12 mg) prior to chemotherapy, and oral dexamethasone (8 mg/daily) on days 2-4. Twenty-four patients received the complete i.v. NEPA infusion volume. Fosnetupitant maximum plasma concentration (C_max) was reached at the end of infusion and decreased to <1% of C_max 30 min later. Netupitant was rapidly released from its prodrug and C_max of 590 ng/ml was reached at the end of fosnetupitant infusion, with a mean exposure (AUC_∞) of 15,588 h∙ng/ml. Palonosetron C_max was reached at the end of infusion, with a mean AUC_∞ of 36.07 h∙ng/ml. The most common adverse events were constipation (29%), nausea (17%), and vasospasm (8%). No i.v. NEPA-related injection site reactions occurred. Fosnetupitant conversion to netupitant occurred rapidly in cancer patients. Netupitant and palonosetron pharmacokinetic profiles in i.v. NEPA were similar to those reported for oral NEPA. i.v. NEPA was well tolerated with a similar safety profile to oral NEPA. i.v. NEPA provides additional administration convenience. Clinical trial registration number: EudraCT 2015-004750-18.

Complementary Pharmacokinetic Profiles of Netupitant and Palonosetron Support the Rationale for Their Oral Fixed Combination for the Prevention of Chemotherapy-Induced Nausea and Vomiting

NEPA is the first fixed-combination antiemetic composed of the neurokinin-1 receptor antagonist netupitant (netupitant; 300 mg) and the 5-hydroxytryptamine-3 receptor antagonist palonosetron (palonosetron; 0.50 mg). This study evaluated the pharmacokinetic profiles of netupitant and palonosetron. The pharmacokinetic profiles of both drugs were summarized using data from phase 1-3 clinical trials. netupitant and palonosetron have high absolute bioavailability (63%-87% and 97%, respectively). Their overall systemic exposures and maximum plasma concentrations are similar under fed and fasting conditions. netupitant binds to plasma proteins in a high degree (>99%), whereas palonosetron binds to a low extent (62%). Both drugs have large volumes of distribution (cancer patients: 1656-2257 L and 483-679 L, respectively). netupitant is metabolized by cytochrome P450 3A4 to 3 major pharmacologically active metabolites (M1, M2, and M3). palonosetron is metabolized by cytochrome P450 2D6 to 2 major substantially inactive metabolites (M4 and M9). Both drugs have similar intermediate-to-low systemic clearances and long half-lives (cancer patients: netupitant, 19.5-20.8 L/h and 56.0-93.8 hours; palonosetron: 7.0-11.3 L/h and 43.8-65.7 hours, respectively). netupitant and its metabolites are eliminated via the hepatic/biliary route (87% of the administered dose), whereas palonosetron and its metabolites are mainly eliminated via the kidneys (85%-93%). Altogether, these data explain the lack of pharmacokinetic interactions between netupitant and palonosetron at absorption, binding, metabolic, or excretory level, thus highlighting their compatibility as the oral fixed combination NEPA, with administration convenience that may reduce dosing mistakes and increase treatment compliance.

Recent advances in antiemetics: new formulations of 5HT3-receptor antagonists

Purpose

To discuss new therapeutic strategies for chemotherapy-induced nausea and vomiting (CINV) involving 5-hydroxytryptamine type 3 (5HT₃)-receptor antagonists (RAs).

Summary

CINV remains poorly controlled in patients receiving moderately emetogenic chemotherapy (MEC) or highly emetogenic chemotherapy (HEC); nausea and delayed-phase CINV (24-120 hours after chemotherapy) are the most difficult to control. National Comprehensive Cancer Network (NCCN) and American Society of Clinical Oncology (ASCO) antiemesis-guideline recommendations for HEC include a four-drug regimen (5HT₃ RA, neurokinin 1 [NK₁] RA, dexamethasone, and olanzapine). For some MEC regimens, a three-drug regimen (5HT₃ RA, NK₁ RA, and dexamethasone) is recommended. While 5HT₃ RAs have dramatically improved CINV in the acute phase (0-24 hours after chemotherapy), their efficacy declines in the delayed phase. Newer formulations have been developed to extend 5HT₃-RA efficacy into the delayed phase. Granisetron extended-release subcutaneous (GERSC), the most recently approved 5HT₃ RA, provides slow, controlled release of therapeutic granisetron concentrations for ≥5 days. GERSC is included in the NCCN and ASCO guidelines for MEC and HEC, with NCCN-preferred status for MEC in the absence of an NK₁ RA. Efficacy and safety of 5HT₃ RAs in the context of guideline-recommended antiemetic therapy are reviewed.

Conclusion

Recent updates in antiemetic guidelines and the development of newer antiemet-ics should help mitigate CINV, this dreaded side effect of chemotherapy. GERSC, the most recently approved 5HT₃-RA formulation, is indicated for use with other antiemetics to prevent acute and delayed nausea and vomiting associated with initial and repeat courses of MEC and anthracycline-cyclophosphamide combination-chemotherapy regimens.

Guideline for the prevention of acute chemotherapy-induced nausea and vomiting in pediatric cancer patients: A focused update

This update of the 2013 clinical practice guideline provides clinicians with guidance regarding the use of aprepitant and palonosetron for the prevention of acute chemotherapy-induced nausea and vomiting (CINV) in children. The recommendations were based on three systematic reviews. Substantive changes were made to the guideline recommendations including the inclusion of palonosetron to the 5-HT₃ antagonists recommended for children receiving highly emetogenic chemotherapy (HEC) and the recommendation of aprepitant for children 6 months of age or older receiving HEC. To optimize CINV control in children, future work must focus on closing critical research gaps.

Review of oral fixed-dose combination netupitant and palonosetron (NEPA) for the treatment of chemotherapy-induced nausea and vomiting

Current guidelines recommend the combination of a neurokinin-1 (NK1) receptor antagonist (RA) and a 5-hydroxytryptamine-3 (5-HT3) RA, together with corticosteroids, in order to prevent chemotherapy-induced nausea and vomiting with anthracycline-cyclophosphamide and highly emetogenic chemotherapy, and it is to be considered with moderately emetogenic chemotherapy. Netupitant and palonosetron (NEPA) is a fixed-dose combination of netupitant, a novel, highly selective NK1 RA, and palonosetron, a new-generation 5-HT3 RA, targeting two major emetic pathways in a single oral capsule. In clinical trials, NEPA administered on day 1 together with dexamethasone was highly effective and well tolerated in the prevention of chemotherapy-induced nausea and vomiting in patients with solid tumors undergoing moderately emetogenic chemotherapy or highly emetogenic chemotherapy. NEPA offers maximal convenience, and as a simple guideline-based regimen, has the potential to improve adherence to guidelines.

Prolonged inhibition of 5-HT₃ receptors by palonosetron results from surface receptor inhibition rather than inducing receptor internalization

BACKGROUND AND PURPOSE

The 5-HT₃ receptor antagonist palonosetron is an important treatment for emesis and nausea during cancer therapy. Its clinical efficacy may result from its unique binding and clearance characteristics and receptor down-regulation mechanisms. We investigated the mechanisms by which palonosetron exerts its long-term inhibition of 5-HT₃ receptors for a better understanding of its clinical efficacy.

EXPERIMENTAL APPROACH

Cell surface receptors (recombinantly expressed 5HT₃A or 5HT₃AB in COS-7 cells) were monitored using [³H]granisetron binding and ELISA after exposure to palonosetron. Receptor endocytosis was investigated using immunofluorescence microscopy.

KEY RESULTS

Chronic exposure to palonosetron reduced the number of available cell surface [³H]granisetron binding sites. This down-regulation was not sensitive to either low temperature or pharmacological inhibitors of endocytosis (dynasore or nystatin) suggesting that internalization did not play a role. This was corroborated by our observation that there was no change in cell surface 5-HT₃ receptor levels or increase in endocytic rate. Palonosetron exhibited slow dissociation from the receptor over many hours, with a significant proportion of binding sites being occupied for at least 4 days. Furthermore, our observations suggest that chronic receptor down-regulation involved interactions with an allosteric binding site.

CONCLUSIONS AND IMPLICATIONS

Palonosetron acts as a pseudo-irreversible antagonist causing prolonged inhibition of 5-HT₃ receptors due to its very slow dissociation. In addition, an irreversible binding mode persists for at least 4 days. Allosteric receptor interactions appear to play a role in this phenomenon.

Analgesic effects of palonosetron in the intravenous propofol injection

Background

Propofol is a good induction agent, but it has the disadvantage of causing pain on intravenous injection. The incidence of propofol-induced pain is approximately 70%. Palonosetron is a novel second-generation 5-hydroxytryptamine type 3 (5-HT3) receptor antagonist. We presumed that palonosetron would be effective in reducing the occurrence of propofol-induced pain based on similar mechanisms to other 5-HT3 receptor antagonists.

Methods

Eighty patients were randomized to either Group N (0.9% sodium chloride [normal saline] 2 ml, n = 40) or Group P (palonosetron 0.075 mg, 2 ml, n = 40). Patients were intravenously given a 2 ml pretreatment solution, containing either palonosetron 0.075 mg or normal saline. Following pretreatment with 2 ml of palonosetron 0.075 mg or normal saline, we manually occluded venous drainage midarm with the help of an assistant. One minute later, we released the occlusion of venous drainage. This was followed by a 5-second propofol injection at 25% of the total calculated doses. Patients were then interviewed about whether or not they experienced propofol-induced pain.

Results

Overall, the incidence of propofol-induced pain was 60% in the normal saline group and 27.5% in the palonosetron group. No patients in the palonosetron group experienced severe pain. The incidence of propofol-induced pain was significantly lower in the palonosetron group compared to the normal saline group (P < 0.01).

Conclusions

Following pretreatment with palonosetron, 72.5% of patients experienced a decrease in the occurrence of propofol-induced pain.

Randomized pharmacokinetic study comparing subcutaneous and intravenous palonosetron in cancer patients treated with platinum based chemotherapy

BACKGROUND

Palonosetron is a potent second generation 5- hydroxytryptamine-3 selective antagonist which can be administered by either intravenous (IV) or oral routes, but subcutaneous (SC) administration of palonosetron has never been studied, even though it could have useful clinical applications. In this study, we evaluate the bioavailability of SC palonosetron.

PATIENTS AND METHODS

Patients treated with platinum-based chemotherapy were randomized to receive SC or IV palonosetron, followed by the alternative route in a crossover manner, during the first two cycles of chemotherapy. Blood samples were collected at baseline and 10, 15, 30, 45, 60, 90 minutes and 2, 3, 4, 6, 8, 12 and 24 h after palonosetron administration. Urine was collected during 12 hours following palonosetron. We compared pharmacokinetic parameters including AUC0-24h, t1/2, and Cmax observed with each route of administration by analysis of variance (ANOVA).

RESULTS

From October 2009 to July 2010, 25 evaluable patients were included. AUC0-24h for IV and SC palonosetron were respectively 14.1 and 12.7 ng × h/ml (p=0.160). Bioavalability of SC palonosetron was 118% (95% IC: 69-168). Cmax was lower with SC than with IV route and was reached 15 minutes following SC administration.

CONCLUSIONS

Palonosetron bioavailability was similar when administered by either SC or IV route. This new route of administration might be specially useful for outpatient management of emesis and for administration of oral chemotherapy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01046240.

Palonosetron for the prevention of chemotherapy-induced nausea and vomiting

Chemotherapy-induced nausea and vomiting (CINV) remains both a feared side effect of cancer treatment and a focus of many supportive care initiatives/guidelines. The class of medications known as serotonin receptor antagonists (5-HT3RAs) are integral in the prevention of CINV from both moderately and highly emetogenic chemotherapy. Palonosetron (ALOXI(®)), a second-generation 5-HT3RA, has a higher affinity for the 5-HT3 receptor, has a longer half-life and has unique interactions with the 5-HT3 receptor compared with the current first-generation 5-HT3RA such as ondansetron, granisetron, dolasetron and tropisetron. This may allow palonosetron an advantage in control of CINV. This review article examines the available evidence, the pharmacokinetics and the safety and tolerability of palonosetron in the prevention of CINV.

Pharmacokinetic Evaluation and Safety Profile of a 15-Minute Versus 30-Second Infusion of Palonosetron in Healthy Subjects

Palonosetron is a potent, selective 5-HT(3) receptor antagonist effective in the prevention of acute and delayed chemotherapy-induced nausea and vomiting. In practice, 5-HT(3) receptor antagonists, including palonosetron, are often coadministered with dexamethasone over approximately 15 minutes, although the approval of palonosetron was based on administration as a 30-second infusion. This open-label, randomized, 2-way crossover trial compared the pharmacokinetics and safety of palonosetron 0.25 mg administered as a 15-minute 50-mL intravenous infusion with a 30-second 5-mL infusion. Aside from an anticipated 40% decrease in maximum plasma concentration after a 15-minute infusion, the pharmacokinetics of palonosetron (including area under the plasma concentration-time curve [AUC], plasma elimination half-life, total body clearance, and apparent volume of distribution at steady state) were similar for both treatments. Both treatments were well tolerated, with no significant changes in vital signs or electrocardiograms. Palonosetron infused over 15 minutes is well tolerated, with an AUC(0-infinity) equivalent to a 30-second infusion.

An update on palonosetron hydrochloride for the treatment of radio/chemotherapy-induced nausea and vomiting

INTRODUCTION

Nausea and vomiting are well recognized in different clinical situations, suggesting that no single mechanism is likely to be responsible for their production. Chemotherapy-induced nausea and vomiting (CINV) can have a negative impact on quality of life and this may lead to a refusal of curative therapy or to a decline in palliative benefits offered by cytotoxic treatment. Palonosetron is a new agent in the class of 5-HT3 receptor antagonists (5-HT3RAs), and differs from the other agents by its higher receptor-binding affinity and longer half-life. These pharmacological properties have resulted in improved antiemetic activity in clinical trials, particularly in the treatment of delayed CINV following moderate emetogenic chemotherapy (MEC).

AREA COVERED

A systematic review of the medical literature was completed to inform this update. MEDLINE, the Cochrane Collaboration Library and meeting materials from ASCO and MASCC were all searched.

EXPERT OPINION

Palonosetron was the only serotonin receptor antagonist approved for prevention of delayed CINV caused by MEC and its use was incorporated in guideline recommendations. To date, several treatment settings such as multiple day chemotherapy require further studies to improve emesis related to therapy.

A randomized, double-blind trial of palonosetron compared with ondansetron in preventing postoperative nausea and vomiting after gynaecological laparoscopic surgery

This randomized, double-blind study evaluated the relative efficacy of palonosetron (a new, selective 5-hydroxytryptamine type 3 [5-HT(3)] receptor antagonist) and ondansetron in preventing postoperative nausea and vomiting (PONV) in patients undergoing gynaecological laparoscopic surgery. Patients received either palonosetron 0.075 mg (n = 45) or ondansetron 8 mg (n = 45), intravenously, immediately before induction of general anaesthesia. The occurrence of nausea and vomiting and the severity of nausea according to a visual analogue scale were monitored immediately after the end of surgery and during the following 24 h. The incidence of PONV was significantly lower in the palonosetron group compared with the ondansetron group (42.2% vs 66.7%, respectively). There were no significant statistical differences in the visual analogue scale for nausea. In conclusion, palonosetron 0.075 mg was more effective than ondansetron 8 mg in preventing PONV.

Determination of palonosetron in human urine by LC-MS/MS

BACKGROUND

Palonosetron is used for the prevention of chemotherapy-induced nausea and vomiting. However, quantification of this drug in human urine has been rare.

RESULTS

A one-step dilution method for the analysis of palonosetron in human urine using LC coupled to positive MS/MS has been developed and validated according to US FDA guidelines. The method uses 200 µl of urine and covers a working range from 2.5-1000 ng/ml with a LLOQ of 2.5 ng/ml.

CONCLUSION

This new LC-MS/MS assay is sensitive and specific despite using an external standard method. It is suitable for clinical studies of palonosetron.

Review of palonosetron: emerging data distinguishing it as a novel 5-HT(3) receptor antagonist for chemotherapy-induced nausea and vomiting

IMPORTANCE OF THE FIELD

Since the advent of the 5-hydroxytryptamine 3 receptor antagonists (5-HT3RAs) in the 1990s, dramatic improvements have been achieved in the field of antiemetic therapy. The enhanced prevention of delayed and overall chemotherapy-induced nausea and vomiting (CINV) offered by palonosetron, a second-generation 5-HT3RA and aprepitant, the first neurokinin-1 receptor antagonists (NK-1RA) represent the only significant treatment advances in the past decade. While initial trials of single-dose palonosetron indicated a potential benefit over first-generation 5-HT3RAs, only recently have new data become available, increasing the weight of evidence distinguishing it as a new 5-HT3RA in the class.

AREAS COVERED IN THIS REVIEW

History of antiemetics and palonosetron, including clinical trials and pharmacological research, and literature published between 1981 and 2010 are covered.

WHAT THE READER WILL GAIN

Unique pharmacological characteristics of palonosetron exhibiting prolonged half-life, high receptor affinity, allosteric interactions and positive cooperativity with 5-HT3 receptor resulting in long-term alteration and internalization of this receptor may explain the clinical observation of palonosetron.

TAKE HOME MESSAGE

This review of recent progress in antiemetic therapy focuses on the newest data on palonosetron and discusses future trials and implications for clinical practice, with the overall goal of learning from history.

Palonosetron hydrochloride for the prevention of chemotherapy-induced nausea and vomiting

A large number of different 5-hydroxytryptamine (HT)(3) receptor antagonists have been marketed with the indication of preventing nausea and vomiting induced by chemotherapy--palonosetron is the most recently developed of these. Pharmacologic studies have revealed that palonosetron has a long half-life, a high affinity for 5-HT(3) receptors, exhibits allosteric binding to 5-HT(3) receptors and possess positive cooperativity. Although interesting, pharmacologic differences are only useful if they result in clinical advantages, such as an increase in efficacy and/or an improvement in tolerability. We summarize preclinical and clinical studies of palonosetron and compare the efficacy and tolerability with the other 5-HT(3) receptor antagonists, ondansetron, granisetron and dolasetron.

A phase II study of palonosetron combined with dexamethasone to prevent nausea and vomiting induced by highly emetogenic chemotherapy

BACKGROUND

This is a randomized, double-blind, dose-ranging study in patients receiving highly emetogenic chemotherapy (HEC) to evaluate the safety, efficacy, and pharmacokinetics of palonosetron, in combination with dexamethasone.

MATERIALS AND METHODS

We randomized 233 patients to receive palonosetron as a single i.v. bolus dose of 0.075, 0.25, or 0.75 mg before administration of HEC. Dexamethasone (12-16 mg i.v. on day 1, 8 mg i.v. on day 2, and 4-8 mg i.v. on day 3) was administered for prophylactic antiemesis. Pharmacokinetics of palonosetron was analyzed in 24 patients.

RESULTS

In this study, all patients were given > or =50 mg/m(2) cisplatin, which was considered to be HEC. No significant differences in complete response (CR: no emesis and no rescue medication) rates were found in the first 24 h between the 0.075-, 0.25-, and 0.75-mg groups (77.6%, 81.8%, and 79.5%, respectively). In the 120-h period of overall observation, CR rates increased in a dose-dependent manner. In the 0.75-mg group, we observed a significantly longer time to treatment failure than in the 0.075-mg group (median time >120 versus 82.0 h, P = 0.038). Palonosetron was tolerated well and did not show any dose-related increase in adverse effects.

CONCLUSIONS

Palonosetron at doses of 0.25 and 0.75 mg was shown to be effective in preventing chemotherapy-induced nausea and vomiting with high CR rates of patients treated with HEC in Japan. All tested doses of palonosetron were tolerated well.

Prediction of drug distribution within blood

Drug distribution in blood, defined as drug blood-to-plasma concentration ratio (R(b)), is a fundamental pharmacokinetic parameter. It relates the plasma clearance to the blood clearance, enabling the physiological interpretation of this parameter. Although easily experimentally determined, R(b) values are lacking for the vast majority of drugs. We present a systematic approach using mechanistic, partial least squares (PLS) regression and artificial neural network (ANN) models to relate various in vitro and in silico molecular descriptors to a dataset of 93 drug R(b) values collected in the literature. The ANN model resulted in the best overall approach, with r(2)=0.927 and r(2)=0.871 for the train and the test sets, respectively. PLS regression presented r(2)=0.557 for the train and r(2)=0.656 for the test set. The mechanistic model provided the worst results, with r(2)=0.342 and, additionally, is limited to drugs with a basic ionised group with pKa<7. The ANN model for drug distribution in blood can be a valuable tool in clinical pharmacokinetics as well as in new drug design, providing predictions of R(b) with a percentage of correct values within a 1.25-fold error of 86%, 84% and 87% in the train, test and validation set of data.

What is the Objective of the Mass Balance Study? A Retrospective Analysis of Data in Animal and Human Excretion Studies Employing Radiolabeled Drugs

Mass balance excretion studies in laboratory animals and humans using radiolabeled compounds represent a standard part of the development process for new drugs. From these studies, the total fate of drug-related material is obtained: mass balance, routes of excretion, and, with additional analyses, metabolic pathways. However, rarely does the mass balance in radiolabeled excretion studies truly achieve 100% recovery. Many definitions of cutoff criteria for mass balance that identify acceptable versus unacceptable recovery have been presented as ad hoc statements without a strong rationale. To address this, a retrospective analysis was undertaken to explore the overall performance of mass balance studies in both laboratory animal species and humans using data for 27 proprietary compounds within Pfizer and extensive review of published studies. The review has examined variation in recovery and the question of whether low recovery was a cause for concern in terms of drug safety. Overall, mean recovery was greater in rats and dogs than in humans. When the circulating half-life of total radioactivity is greater than 50 h, the recovery tends to be lower. Excretion data from the literature were queried as to whether drugs linked with toxicities associated with sequestration in tissues or covalent binding exhibit low mass balance. This was not the case, unless the sequestration led to a long elimination half-life of drug-related material. In the vast majority of cases, sequestration or concentration of drug-related material in an organ or tissue was without deleterious effect and, in some cases, was related to the pharmacological mechanism of action. Overall, from these data, recovery of radiolabel would normally be equal to or greater than 90%, 85%, and 80% in rat, dog, and human, respectively. Since several technical limitations can underlie a lack of mass balance and since mass balance data are not sensitive indicators of the potential for toxicity arising via tissue sequestration, absolute recovery in humans should not be used as a major decision criteria as to whether a radiolabeled study has met its objectives. Instead, the study should be seen as an integral part of drug development answering four principal questions: 1) Is the proposed clearance mechanism sufficiently supported by the identities of the drug-related materials in excreta, so as to provide a complete understanding of clearance and potential contributors to interpatient variability and drug-drug interactions? 2) What are the drug-related entities present in circulation that are the active principals contributing to primary and secondary pharmacology? 3) Are there findings (low extraction recovery of radiolabel from plasma, metabolite structures indicative of chemically reactive intermediates) that suggest potential safety issues requiring further risk assessment? 4) Do questions 2 and 3 have appropriate preclinical support in terms of pharmacology, safety pharmacology, and toxicology? Only if one or more of these four questions remain unanswered should additional mass balance studies be considered.

Systemic anticancer therapy in gynecological cancer patients with renal dysfunction

Chronic kidney disease is a common occurrence in patients with gynecological cancer. Systemic anticancer treatment in such patients is a challenge for clinicians because of altered drug pharmacokinetics. For those drugs that are excreted mainly by the kidneys, decreased renal function may lead to increased systemic exposure and increased toxicity. Dose adjustment based on pharmacokinetic changes is required in this situation to avoid life-threatening toxicity. In this review, we summarize the nephrotoxicity and pharmacokinetic data of agents commonly used in systemic anticancer treatment of gynecological cancers and dose adjustment guidelines in the presence of impaired renal function. We review 17 medications that need dose adjustment (cisplatin, carboplatin, doxorubicin, epirubicin, cyclophosphamide, ifosfamide, topotecan, irinotecan, etoposide, capecitabine, bleomycin, methotrexate, actinomycin D, granulocyte-macrophage colony-stimulating factor, metoclopramide, cimetidine, and diphenhydramine) as well as 27 drugs that do not (paclitaxel, docetaxel, pegylated liposomal doxorubicin, gemcitabine, oxaliplatin, fluorouracil, vincristine, letrozole, anastrozole, tamoxifen, leuprorelin, megestrol, gefitinib, erlotinib, trastuzumab, leucovorin, granulocyte colony-stimulating factor, erythropoietin, ondansetron, granisetron, palonosetron, tropisetron, dolasetron, aprepitant, dexamethasone, lorazepam, and diazepam). We also review the formulae commonly used to estimate creatinine clearance, including Cockcroft-Gault, Chatelut, Jelliffe, Wright, and the Modification of Diet in Renal Disease study formulae.

New drugs for chemotherapy-induced nausea and vomiting: focus on palonosetron

Significant progress has been made in the development of effective, convenient and well-tolerated means to prevent chemotherapy-induced nausea and vomiting (CINV). Nevertheless, a substantial minority of patients continue to have suboptimal antiemetic control, and additional treatment approaches are needed. One avenue of investigation being pursued involves the evaluation of a new 5-hydroxytryptamine (5-HT(3)) receptor antagonist (palonosetron) that differs from available serotonin antagonists in its markedly longer half-life (40 h) and greater binding affinity for the type-3 serotonin receptor. Analysis of available clinical data demonstrates that palonosetron is an active and well-tolerated new 5-HT(3) antagonist. Moreover, single-dose palonosetron, prior to chemotherapy, has demonstrated improved control of CINV through the full period of emetic risk with a single dose. Palonosetron is recommended as the preferred treatment of acute and delayed emesis prevention with moderate emetic risk chemotherapy in the most recently published evidence-based antiemesis consensus guidelines. Further studies incorporating dexamethasone to 5-HT(3) antagonists will be necessary to determine the relative efficacy of palonosetron compared with available agents. These trials could open a new era in the treatment of CINV.

Evaluation of safety and pharmacokinetics of consecutive multiple-day dosing of palonosetron in healthy subjects

This study evaluated the safety and pharmacokinetics of consecutive multiple-day dosing of palonosetron. Sixteen healthy subjects received an intravenous bolus dose of palonosetron 0.25 mg (n = 12) or placebo (n = 4) daily for 3 consecutive days. Safety was evaluated throughout the study. Serial plasma samples were collected on days 1 and 3 for pharmacokinetic determinations. Three days of dosing with palonosetron 0.25 mg was safe and well tolerated. There were no clinically significant changes from baseline in laboratory values, vital signs, physical examinations, or electrocardiogram intervals. Plasma palonosetron concentrations declined in a biphasic manner, measurable up to 168 hours after dosing on day 3. Mean terminal phase elimination half-life after day 3 dosing was 42.8 hours. The 2.1-fold accumulation of palonosetron in plasma following 3 daily doses was predictable based on elimination half-life of approximately 40 hours, and the maximum plasma concentration remained below the maximum plasma concentration previously observed after a single, well-tolerated 0.75 mg intravenous bolus dose of palonosetron.

Pharmacokinetics of palonosetron in combination with aprepitant in healthy volunteers

BACKGROUND

Palonosetron is a second-generation 5-HT(3) receptor antagonist with a prolonged duration of action and higher receptor binding affinity than first-generation agents (ondansetron, granisetron, and dolasetron). Aprepitant is a selective antagonist of substance P/neurokinin 1 that augments the benefit of 5-HT(3) receptor antagonists in the prevention of chemotherapy-induced nausea and vomiting.

METHODS

This randomized, open-label, two-way, crossover trial was designed to evaluate the effect of oral aprepitant on the pharmacokinetics and safety of a single intravenous (IV) dose of palonosetron in 12 healthy subjects. Treatment A consisted of a single IV bolus dose of palonosetron 0.25mg on day 1. Treatment B added oral aprepitant 125 mg on day 1 (30 minutes prior to palonosetron) and 80 mg on days 2 and 3. Blood for pharmacokinetic evaluations was collected through 168 hours after palonosetron administration on days 1 and 15; safety was monitored through day 22.

RESULTS

Mean plasma concentration-time plots for palonosetron were virtually identical for palonosetron administered alone or with concomitant aprepitant. The ratio of geometric least-square mean values (with:without aprepitant) for C(max) was 98.6% (90% confidence interval [CI]: 61.8-157%), and for AUC(0-infinity) the ratio was 101% (90% CI: 85.6-119%). With and without aprepitant coadministration, respectively, mean plasma elimination half-life was 40 hours and 43 hours (difference: -3.0 hours; p = 0.348), mean total body clearance was 130 mL/min and 136 mL/min (difference: -5.6 mL/min; p = 0.735), and mean volume of distribution at steady-state was 410.9 L and 442.3 L (difference: -31.4 L; p = 0.463). Palonosetron alone and the palonosetron/aprepitant regimen were well tolerated.

CONCLUSION

These results indicate no significant differences in pharmacokinetic parameters for palonosetron between the two treatments, and suggest that palonosetron can be safely coadministered with aprepitant with no alterations in the expected safety profile and no dosage adjustment necessary.