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Plitidepsin (Aplidin®) is a marine-derived anticancer compound currently investigated in phase III clinical trials. This article describes the distribution, metabolism and excretion of this novel agent and it mainly aims to identify the major routes of elimination. Six subjects were enrolled in a mass balance study during which radiolabelled plitidepsin was administered as a 3-h intravenous infusion. Blood samples were taken and urine and faeces were collected. Total radioactivity (TRA) analysis using Liquid Scintillation Counting (LSC) was done to determine the amount of radioactivity excreted from the body and plitidepsin concentrations in whole blood, plasma and urine were determined by validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays. In total, a mean of 77.4% of the administered radioactivity was excreted over a time period of 20 days, of which 71.3% was recovered in faeces and 6.1% was found in urine. The majority excreted in urine was accounted for by unchanged plitidepsin, with only 1.5% of the total administered dose explained by metabolites in urine. Faeces, on the other hand contained low levels of parent compound, which means that most of the TRA excreted in faeces was accounted for by metabolites. TRA levels were 3.7 times higher in whole blood compared to plasma. Plitidepsin was widely distributed and plasma clearance was low. This study shows that red blood cells are a major distribution compartment and that the biliary route is the main route of total radioactivity excretion. [ABSTRACT FROM AUTHOR]

Background and Objective: PM00104 (Zalypsis(®)) is a novel marine-derived compound that has shown antineoplastic activity against a number of human tumour cell lines. Myelosuppression was found to be a PM00104 dose-limiting toxicity during phase I studies. The objective of this study was to characterize the time course of neutropenia after intravenous PM00104 administration in cancer patients.Methods: Absolute neutrophil counts (ANCs) and pharmacokinetic data from 144 patients receiving PM00104 doses ranging from 0.053 to 5 mg/m(2) were used to estimate the system-related (baseline ANC [Circ(0)], mean transit time [MTT], feedback on proliferation [γ] and maturation [δ]) and drug-specific (first-order elimination rate constant from effect compartment [k(e0)] [α and β]) parameters of a modified Friberg's model. The concentrations in the effect compartment (C(e)) were assumed to reduce the proliferation rate of the progenitor cells according to the function [Formula: see text] Model evaluation and simulations were undertaken to evaluate the effect of dose intensity, dose density and the intravenous infusion duration on severe neutropenia incidence.Results: The typical values (between-subject variability [%]) of the Circ(0), MTT, γ, δ, k(e0), α and β were estimated to be 5.66 × 10(9) cells/L (13 %), 149 h (29 %), 0.136, 0.191, 0.00639 h(-1) (32 %), 0.332 L/µg (24 %) and 1.47, respectively. Age, bodyweight, sex, serum albumin, total protein, liver metastases, number of previous chemotherapy lines and performance status were not associated with model parameters. The model evaluation evidenced an accurate prediction of the neutropenia grade 3 and/or 4 incidence. Simulations indicated that PM00104 dose and dosing interval, but not infusion duration, were the main determinants of the neutropenia severity and duration.Conclusions: The time course of neutropenia following PM00104 was well characterized by the model developed. The model-predicted time course of the ANCs and its variability confirmed that neutropenia is reversible, of short duration and non-cumulative. [ABSTRACT FROM AUTHOR]

Objective: To characterize the population pharmacokinetics of plitidepsin (Aplidin) in cancer patients.Methods: A total of 283 patients (552 cycles) receiving intravenous plitidepsin as monotherapy at doses ranging from 0.13 to 8.0 mg/m(2) and given as 1- or 24-h infusions every week; 3- or 24-h infusion biweekly; or 1-h infusion daily for 5 consecutive days every 21 days were included in the analysis. An open three-compartment pharmacokinetic model and a nonlinear binding to red blood cells model were used to describe the plitidepsin pharmacokinetics in plasma and blood, respectively, using NONMEM V software. The effect of selected covariates on plitidepsin pharmacokinetics was investigated. Model evaluation was performed using goodness-of-fit plots, posterior predictive check and bootstrap.Results: Plasma clearance and its between subject variability (%) was 13.6 l/h (71). Volume of distribution at steady-state was calculated to be 4791 l (59). The parameters B (max) and C (50) of the non-linear blood distribution were 471 microg/l (56) and 41.6 microg/l, respectively. Within the range of covariates studied, age, sex, body size variables, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total bilirubin, creatinine clearance, albumin, total protein, performance status, co-administration of inhibitors or inducers of CYP3A4 and presence of liver metastases were not statistically related to plitidepsin pharmacokinetic parameters. Bootstrap and posterior predictive check evidenced the model was deemed appropriate to describe the time course of plitidepsin blood and plasma concentrations in cancer patients.Conclusions: The integration of phase I/II pharmacokinetic data demonstrated plitidepsin linear elimination from plasma, dose-proportionality up to 8.0 mg/m(2), and time-independent pharmacokinetics. The distribution to red blood cells can be considered linear at doses lower than 5 mg/m(2) administered as 3-h or longer infusion. No clinically relevant covariates were identified as predictors of plitidepsin pharmacokinetics. [ABSTRACT FROM AUTHOR]

Purpose: The main objective was to quantify any potential differences in pharmacokinetic (PK) parameters (AUC and C max ) between RTXM83, a proposed rituximab biosimilar, and its reference product, using a population PK model approach., Methods: Rituximab PK and PD data were obtained from a randomized, double-blind, phase III clinical study (RTXM83-AC-01-11) in patients with diffuse large B-cell lymphoma (DLBCL) that received 375 mg/m 2 intravenous RTXM83 or its reference product with CHOP regimen, every 3 weeks, for six cycles. Rituximab levels were quantified by Meso Scale Discovery assay. PK analysis was performed using NONMEM 7.3.0. The effect of disease and patient covariates on RXTM83 PK was investigated. Model was evaluated using visual predictive check and non-parametric bootstrap., Results: In total, 251 DLBCL patients (127 and 124 in RXTM83-CHOP and rituximab-CHOP arms, respectively) and 5341 serum concentrations (2703 for RXTM83 and 2638 for rituximab, respectively) were available for the population PK analysis. The volume of distribution of the central compartment (V 1 ) and clearance of RXTM83 were estimated at 3.19 L and 12.5 mL/h, respectively. Body surface area allowed to explain the interindividual variability for V 1 . A statistical analysis showed that systemic exposure (AUC and C max ) of RTXM83 was similar to rituximab. The 90% confidence intervals for all pairwise comparisons were within the predefined bioequivalence interval of 0.80-1.25. PD similarity of B-cell depletion and recovery was also observed., Conclusions: The time course of RTXM83 was well characterized by the model developed. The systemic exposure of RTXM83 and its associated variability were similar to those for rituximab reference in DLBCL patients, demonstrating PK similarity. The PD similarity of RTXM83 and rituximab reference product was also demonstrated.

Purpose: To determine the recommended dose and antitumor activity of single-agent elisidepsin as a 24-h intravenous (i.v.) infusion fortnightly [biweekly, d1 and 15 every 4 weeks (q4wk); Arm A, dose-intensity strategy] or as a 3-h i.v. infusion weekly (d1, 8, 15 and 22 q4wk; Arm B, dose-density strategy) in adult patients with unresectable, locally advanced or metastatic pretreated esophageal, gastroesophageal junction and gastric cancer., Methods: Patients were randomized to one of two elisidepsin dosing schedules. Phase Ib starting doses were 8.0 mg flat dose (FD) in Arm A and 3.0 mg FD in Arm B. Phase II subsequently explored antitumor activity of both dosing schedules at the respective recommended doses., Results: Forty-four patients received elisidepsin: 12 in stage Ib and 32 in stage II. The recommended doses were defined as 10 mg FD (Arm A) and 3.75 mg FD (Arm B). Both schedules were well tolerated. Most adverse events were mild or moderate, reversible and predictable with no meaningful differences between schedules. The pharmacokinetic profiles of both schedules were similar to those reported previously in patients with solid tumors treated with a comparable dose. An interim analysis found tumor control in one patient receiving elisidepsin fortnightly, and in none given elisidepsin weekly; patient accrual was therefore discontinued due to lack of efficacy., Conclusions: Both schedules at the recommended doses presented an acceptable safety profile, but lack of response means that we do not recommend further evaluation of single-agent elisidepsin as chemotherapy for unresectable, locally advanced or metastatic gastroesophageal cancer.

Objective: To determine the recommended dose for phase II trials of elisidepsin (PM02734, Irvalec®) in combination with erlotinib in patients with advanced malignant solid tumors., Methods: Open-label, dose-escalating, phase I study of intravenous elisidepsin administered weekly (days 1, 8 and 15) over 3 h as a flat dose (FD) and daily oral erlotinib, every 3 weeks. A pharmacokinetic analysis was done on blood samples collected around the first elisidepsin infusion., Results: Thirty patients were treated across six different dose levels (DLs) ranging from elisidepsin 0.33-2.25 mg/erlotinib 100-150 mg. Two patients had dose-limiting toxicities: grade 3 bilirubin increase (DL3: 0.75 mg/150 mg) and a dose omission for > 2 weeks due to grade 3 alanine aminotransferase increase (DL6: 2.25 mg/100 mg). The daily erlotinib dose was escalated to 150 mg at DL2-DL5, but decreased to 100 mg at DL6, as most grade 3 toxicities were related to this agent only. The most frequent toxicities were transaminase increases (related to elisidepsin), and rash, pruritus and diarrhea (related to erlotinib). No objective responses were observed. Despite no overlapping toxicities, the combination was declared unfeasible due to frequent elisidepsin dose delays. The pharmacokinetics of elisidepsin/erlotinib was not significantly different from that of each agent alone., Conclusion: The difficulty in combining elisidepsin with the standard dose of erlotinib (150 mg), together with the lack of antitumor activity, made the combination unattractive for further development. The trial was closed without having determined a recommended dose.

Purpose: In this study, we characterize the population pharmacokinetics of kahalalide F (KF), a novel marine anticancer drug, after intravenous (i.v.) administration in advanced cancer patients., Methods: Data from 240 patients included in three Phase I and three Phase II trials receiving i.v. weekly and every 3 weeks infusions of KF, at doses ranging 266-6650 µg/m(2), were analyzed using NONMEM™ VII. The effect of demographics and/or pathophysiologically relevant factors on KF pharmacokinetic parameters was evaluated. Model evaluation was conducted using nonparametric bootstrap and visual predictive check (in both internal and external datasets)., Results: An open two-compartment model with linear distribution and elimination from central compartment was suitable to describe the data. Volume of distribution at steady state and its between-subject variability (CV%) was estimated to be 6.56 L (28 %). Plasma clearance was estimated to be 6.25 L/h (43 %). Within the range of covariates evaluated, age, weight, body surface area, gender, ECOG performance status, presence of liver metastases, creatinine clearance, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, total bilirubin, total protein and serum albumin did not contribute to explain KF pharmacokinetic variability to a significant extent. The developed model was deemed appropriate to describe the time course of KF plasma concentrations and its variability in advanced cancer patients., Conclusion: The integration of pharmacokinetic data from six clinical studies demonstrated KF linear elimination from plasma, dose-proportional exposure and time-independent pharmacokinetics. Based on analyzed data, no clinically relevant covariates were identified as predictors of KF pharmacokinetics.

This first-in-human, phase I clinical trial was designed to determine the dose-limiting toxicities (DLTs) and the dose for phase II trials (P2D) of elisidepsin (PM02734) administered as a 30-min or as a 3-h intravenous infusion every 3 weeks (q3wk). Between March 2006 and April 2011, 53 patients with advanced malignant solid tumors were enrolled and treated with elisidepsin on the two different q3wk infusion schedules: 22 (30-min) and 31 (3-h), respectively. Doses evaluated ranged from 0.1 to 1.6 mg/m(2) (30-min q3wk) and from 2.0 to 11.0 mg flat dose (FD) (3-h q3wk). In the 30-min q3wk schedule, transient grade 3/4 increases in hepatic transaminases were the DLT, which appeared at the highest doses tested (from 1.1 to 1.6 mg/m(2)). No DLTs were observed on the 3-h schedule at doses up to 11.0 mg q3wk. Common adverse events were grade 1/2 pruritus, nausea, fatigue and hypersensitivity. Of note, myelotoxicity was not observed. Plasma maximum concentration and total drug exposure increased linearly with dose. Prolonged (≥3 months) disease stabilization was observed in pretreated patients with pleural mesothelioma (n = 1) in the 30-min q3wk arm, and with colorectal adenocarcinoma (n = 3), esophagus adenocarcinoma, endometrium adenocarcinoma, pleural mesothelioma, and head and neck carcinoma (n = 1 each) in the 3-h q3wk arm. In conclusion, elisidepsin doses of 1.1 mg/m(2) (equivalent to a FD of 2.0 mg) and 11.0 mg FD are the dose levels achieved for further phase II trials testing the 30-min q3wk and 3-h q3wk schedules, respectively.

Objective: To determine the maximum tolerated dose and the recommended dose (RD) for phase II trials of elisidepsin (Irvalec®) in combination with carboplatin or gemcitabine., Methods: Open-label, dose-escalating, two-arm, uncontrolled, phase I study. Patients received carboplatin on Day (D) 1, followed by elisidepsin on D1 and D8, every 3 weeks, or gemcitabine on D1 and D15, followed by elisidepsin on D1 and D15, every 4 weeks. A pharmacokinetic analysis was done from blood samples collected during the first treatment infusion., Results: Fifteen patients were treated with carboplatin/elisidepsin at doses from 4 AUC/1.0 mg flat dose (FD) to 5 AUC/2.5 mg FD. Two patients had dose-limiting toxicities (DLTs) at 5 AUC/2.0 mg, a dose delay >2 weeks due to grade-2 ALT increase and grade-3 thrombocytopenia, and a D8 infusion omission due to grade-3 ALT increase. The RD was established at 4 AUC/1.0 mg. Toxicity consisted mainly of mild-moderate anorexia, fatigue, and nausea. Twenty-two patients were treated with gemcitabine/elisidepsin at doses from 1,000 mg*m(2)/1.0 mg FD to 1,250 mg*m(2)/7.5 mg FD. Two patients had DLTs at 1,250 mg*m(2)/7.5 mg, both a D15 dose omission due to grade-2 ALT increase. The RD was defined at 1,250 mg*m(2)/5.0 mg. Toxicity consisted mainly of mild-moderate fatigue, pruritus, erythema, and myalgia. No objective response was observed. No relevant pharmacokinetic interaction was detected., Conclusion: Infra-optimal doses of elisidepsin and carboplatin and a lack of antitumor activity despite using active drug concentrations in combination with gemcitabine do not warrant further clinical development for these two combinations.

Plitidepsin is a cyclic depsipeptide of marine origin in clinical development in cancer patients. Previously, some depsipeptides have been linked to increased cardiac toxicity. Clinical databases were searched for cardiac adverse events (CAEs) that occurred in clinical trials with the single-agent plitidepsin. Demographic, clinical and pharmacological variables were explored by univariate and multivariate logistic regression analysis. Forty-six of 578 treated patients (8.0%) had at least one CAE (11 patients (1.9%) with plitidepsin-related CAEs), none with fatal outcome as a direct consequence. The more frequent CAEs were rhythm abnormalities (n = 31; 5.4%), mostly atrial fibrillation/flutter (n = 15; 2.6%). Of note, life-threatening ventricular arrhythmias did not occur. Myocardial injury events (n = 17; 3.0%) included possible ischemic-related and non-ischemic events. Other events (miscellaneous, n = 6; 1.0%) were not related to plitidepsin. Significant associations were found with prostate or pancreas cancer primary diagnosis (p = 0.0017), known baseline cardiac risk factors (p = 0.0072), myalgia present at baseline (p = 0.0140), hemoglobin levels lower than 10 g/dL (p = 0.0208) and grade ≥2 hypokalemia (p = 0.0095). Treatment-related variables (plitidepsin dose, number of cycles, schedule and/or total cumulative dose) were not associated. Electrocardiograms performed before and after plitidepsin administration (n = 136) detected no relevant effect on QTc interval. None of the pharmacokinetic parameters analyzed had a significant impact on the probability of developing a CAE. In conclusion, the most frequent CAE type was atrial fibrillation/atrial flutter, although its frequency was not different to that reported in the age-matched healthy population, while other CAEs types were rare. No dose-cumulative pattern was observed, and no treatment-related variables were associated with CAEs. Relevant risk factors identified were related to the patient's condition and/or to disease-related characteristics rather than to drug exposure. Therefore, the current analysis supports a safe cardiac risk profile for single-agent plitidepsin in cancer patients.