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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]

Purpose: Kahalalide F (KF) is a dehydroaminobutyric acid-containing peptide from marine origin with activity against several human malignant cell lines. This dose-escalating phase I clinical trial evaluated the maximum tolerated dose (MTD), and the recommended dose for further phase II studies (RD) of weekly KF given as a prolonged (3- to 24-h) intravenous (i.v.) infusion. Methods: Eligible patients with advanced solid tumors and adequate performance status, hematologic, renal, and hepatic function were recruited into this study. Results: A total of 106 patients were treated with KF at four different weekly schedules: 3-h ( n = 40), 24-h ( n = 59), and two transitional schedules [6-h ( n = 4) and 12-h ( n = 3)]. For the 3-h weekly schedule, the MTD was 1,200 μg/m and the RD was 1,000 μg/m. For the 24-h weekly schedule, the MTD was reached (6,650 μg/m), but the RD could not be confirmed. Asymptomatic and reversible grade 3/4 transaminase increase was the most common dose-limiting toxicity in both schedules. Fatigue, paresthesia, pruritus, nausea, vomiting, and rash were the most common KF-related adverse events. No major deviations from linearity were detected in the pharmacokinetic (PK) profiles of both schedules, which showed a narrow distribution and short body residence. Prolonged disease stabilization (≥3 months) occurred in eight patients: two with the 3-h schedule and six with the 24-h schedule. Conclusions: Administration of KF as prolonged weekly infusion appears feasible, with 3-h and 24-h infusion times having an acceptable safety profile. [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]