Population pharmacokinetics meta-analysis of plitidepsin (Aplidin) in cancer subjects

Depsipeptides Targeting Tumor Cells: Milestones from In Vitro to Clinical Trials

Cancer is currently considered one of the most threatening diseases worldwide. Diet could be one of the factors that can be enhanced to comprehensively address a cancer patient's condition. Unfortunately, most molecules capable of targeting cancer cells are found in uncommon food sources. Among them, depsipeptides have emerged as one of the most reliable choices for cancer treatment. These cyclic amino acid oligomers, with one or more subunits replaced by a hydroxylated carboxylic acid resulting in one lactone bond in a core ring, have broadly proven their cancer-targeting efficacy, some even reaching clinical trials and being commercialized as "anticancer" drugs. This review aimed to describe these depsipeptides, their reported amino acid sequences, determined structure, and the specific mechanism by which they target tumor cells including apoptosis, oncosis, and elastase inhibition, among others. Furthermore, we have delved into state-of-the-art in vivo and clinical trials, current methods for purification and synthesis, and the recognized disadvantages of these molecules. The information collated in this review can help researchers decide whether these molecules should be incorporated into functional foods in the near future.

Preclinical and randomized phase I studies of plitidepsin in adults hospitalized with COVID-19

Plitidepsin, a marine-derived cyclic-peptide, inhibits SARS-CoV-2 replication at nanomolar concentrations by targeting the host protein eukaryotic translation elongation factor 1A. Here, we show that plitidepsin distributes preferentially to lung over plasma, with similar potency against across several SARS-CoV-2 variants in preclinical studies. Simultaneously, in this randomized, parallel, open-label, proof-of-concept study (NCT04382066) conducted in 10 Spanish hospitals between May and November 2020, 46 adult hospitalized patients with confirmed SARS-CoV-2 infection received either 1.5 mg (n = 15), 2.0 mg (n = 16), or 2.5 mg (n = 15) plitidepsin once daily for 3 d. The primary objective was safety; viral load kinetics, mortality, need for increased respiratory support, and dose selection were secondary end points. One patient withdrew consent before starting procedures; 45 initiated treatment; one withdrew because of hypersensitivity. Two Grade 3 treatment-related adverse events were observed (hypersensitivity and diarrhea). Treatment-related adverse events affecting more than 5% of patients were nausea (42.2%), vomiting (15.6%), and diarrhea (6.7%). Mean viral load reductions from baseline were 1.35, 2.35, 3.25, and 3.85 log10 at days 4, 7, 15, and 31. Nonmechanical invasive ventilation was required in 8 of 44 evaluable patients (16.0%); six patients required intensive care support (13.6%), and three patients (6.7%) died (COVID-19-related). Plitidepsin has a favorable safety profile in patients with COVID-19.

Marine-derived pipeline anticancer natural products: a review of their pharmacotherapeutic potential and molecular mechanisms

Background

Cancer is a complex and most widespread disease and its prevalence is increasing worldwide, more in countries that are witnessing urbanization and rapid industrialization changes. Although tremendous progress has been made, the interest in targeting cancer has grown rapidly every year. This review underscores the importance of preventive and therapeutic strategies.

Main text

Natural products (NPs) from various sources including plants have always played a crucial role in cancer treatment. In this growing list, numerous unique secondary metabolites from marine sources have added and gaining attention and became potential players in drug discovery and development for various biomedical applications. Many NPs found in nature that normally contain both pharmacological and biological activity employed in pharmaceutical industry predominantly in anticancer pharmaceuticals because of their enormous range of structure entities with unique functional groups that attract and inspire for the creation of several new drug leads through synthetic chemistry. Although terrestrial medicinal plants have been the focus for the development of NPs, however, in the last three decades, marine origins that include invertebrates, plants, algae, and bacteria have unearthed numerous novel pharmaceutical compounds, generally referred as marine NPs and are evolving continuously as discipline in the molecular targeted drug discovery with the inclusion of advanced screening tools which revolutionized and became the component of antitumor modern research.

Conclusions

This comprehensive review summarizes some important and interesting pipeline marine NPs such as Salinosporamide A, Dolastatin derivatives, Aplidine/plitidepsin (Aplidin®) and Coibamide A, their anticancer properties and describes their mechanisms of action (MoA) with their efficacy and clinical potential as they have attracted interest for potential use in the treatment of various types of cancers.

Plitidepsin has a positive therapeutic index in adult patients with COVID-19 requiring hospitalization

Plitidepsin is a marine-derived cyclic-peptide that inhibits SARS-CoV-2 replication at low nanomolar concentrations by the targeting of host protein eEF1A (eukaryotic translation-elongation-factor-1A). We evaluated a model of intervention with plitidepsin in hospitalized COVID-19 adult patients where three doses were assessed (1.5, 2 and 2.5 mg/day for 3 days, as a 90-minute intravenous infusion) in 45 patients (15 per dose-cohort). Treatment was well tolerated, with only two Grade 3 treatment-related adverse events observed (hypersensitivity and diarrhea). The discharge rates by Days 8 and 15 were 56.8% and 81.8%, respectively, with data sustaining dose-effect. A mean 4.2 log10 viral load reduction was attained by Day 15. Improvement in inflammation markers was also noted in a seemingly dose-dependent manner. These results suggest that plitidepsin impacts the outcome of patients with COVID-19.

ONE-SENTENCE SUMMARY

Plitidepsin, an inhibitor of SARS-Cov-2 in vitro , is safe and positively influences the outcome of patients hospitalized with COVID-19.

Plitidepsin has potent preclinical efficacy against SARS-CoV-2 by targeting the host protein eEF1A

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral proteins interact with the eukaryotic translation machinery, and inhibitors of translation have potent antiviral effects. We found that the drug plitidepsin (aplidin), which has limited clinical approval, possesses antiviral activity (90% inhibitory concentration = 0.88 nM) that is more potent than remdesivir against SARS-CoV-2 in vitro by a factor of 27.5, with limited toxicity in cell culture. Through the use of a drug-resistant mutant, we show that the antiviral activity of plitidepsin against SARS-CoV-2 is mediated through inhibition of the known target eEF1A (eukaryotic translation elongation factor 1A). We demonstrate the in vivo efficacy of plitidepsin treatment in two mouse models of SARS-CoV-2 infection with a reduction of viral replication in the lungs by two orders of magnitude using prophylactic treatment. Our results indicate that plitidepsin is a promising therapeutic candidate for COVID-19.

Pharmacokinetics of Marine-Derived Drugs

Marine organisms represent an excellent source of innovative compounds that have the potential for the development of new drugs. The pharmacokinetics of marine drugs has attracted increasing interest in recent decades due to its effective and potential contribution to the selection of rational dosage recommendations and the optimal use of the therapeutic arsenal. In general, pharmacokinetics studies how drugs change after administration via the processes of absorption, distribution, metabolism, and excretion (ADME). This review provides a summary of the pharmacokinetics studies of marine-derived active compounds, with a particular focus on their ADME. The pharmacokinetics of compounds derived from algae, crustaceans, sea cucumber, fungus, sea urchins, sponges, mollusks, tunicate, and bryozoan is discussed, and the pharmacokinetics data in human experiments are analyzed. In-depth characterization using pharmacokinetics is useful for obtaining information for understanding the molecular basis of pharmacological activity, for correct doses and treatment schemes selection, and for more effective drug application. Thus, an increase in pharmacokinetic research on marine-derived compounds is expected in the near future.

Enriching cancer pharmacology with drugs of marine origin

Marine natural products have proven, over the last half-century, to be effective biological modulators. These molecules have revealed new targets for cancer therapy as well as dissimilar modes of action within typical classes of drugs. In this scenario, innovation from marine-based pharmaceuticals has helped advance cancer chemotherapy in many aspects, as most of these are designated as first-in-class drugs. Here, by examining the path from discovery to development of clinically approved drugs of marine origin for cancer treatment-cytarabine (Cytosar-U®), trabectedin (Yondelis®), eribulin (Halaven®), brentuximab vedotin (Adcetris®), and plitidepsin (Aplidin®)- together with those in late clinical trial phases-lurbinectedin, plinabulin, marizomib, and plocabulin-the present review offers a critical analysis of the contributions given by these new compounds to cancer pharmacotherapy.

Review of Chromatographic Bioanalytical Assays for the Quantitative Determination of Marine-Derived Drugs for Cancer Treatment

The discovery of marine-derived compounds for the treatment of cancer has seen a vast increase over the last few decades. Bioanalytical assays are pivotal for the quantification of drug levels in various matrices to construct pharmacokinetic profiles and to link drug concentrations to clinical outcomes. This review outlines the different analytical methods that have been described for marine-derived drugs in cancer treatment hitherto. It focuses on the major parts of the bioanalytical technology, including sample type, sample pre-treatment, separation, detection, and quantification.

Metabolite profiling of the novel anti-cancer agent, plitidepsin, in urine and faeces in cancer patients after administration of 14C-plitidepsin

PURPOSE

Plitidepsin absorption, distribution, metabolism and excretion characteristics were investigated in a mass balance study, in which six patients received a 3-h intravenous infusion containing 7 mg ¹⁴C-plitidepsin with a maximum radioactivity of 100 µCi.

METHODS

Blood samples were drawn and excreta were collected until less than 1% of the administered radioactivity was excreted per matrix for two consecutive days. Samples were pooled within-patients and between-patients and samples were screened for metabolites. Afterwards, metabolites were identified and quantified. Analysis was done using Liquid Chromatography linked to an Ion Trap Mass Spectrometer and offline Liquid Scintillation Counting (LC-Ion Trap MS-LSC).

RESULTS

On average 4.5 and 62.4% of the administered dose was excreted via urine over the first 24 h and in faeces over 240 h, respectively. Most metabolites were found in faeces.

CONCLUSION

Plitidepsin is extensively metabolised and it undergoes dealkylation (demethylation), oxidation, carbonyl reduction, and (internal) hydrolysis. The chemical formula of several metabolites was confirmed using high resolution mass data.

Liquid chromatography-tandem mass spectrometry assay to quantify plitidepsin in human plasma, whole blood and urine

Plitidepsin is an anti-cancer drug currently evaluated in phase I/II/III clinical trials. This article describes the development and validation of a bioanalytical assay to quantify plitidepsin in human plasma, urine and whole blood using HPLC-MS/MS. The analyte was extracted from the matrix by liquid-liquid extraction using tert-butyl methyl ether. Final extracts were injected onto a C18 column, gradient elution was applied for chromatographic separation and detection was performed on a triple quadrupole mass spectrometer operating in the positive ion mode. The assay was linear over the range 0.1-100ng/mL, with acceptable accuracy and precision values. This is the first reported bioanalytical assay quantifying plitidepsin using a stable isotopically labelled standard, achieving a lower limit of quantification of 0.1ng/mL in all three matrices, allowing the quantification of trace levels of plitidepsin, and accomplishing this in an analysis time of two minutes only. The presented method was successfully applied in a mass balance study with plitidepsin in patients with advanced cancer.

Pharmacokinetics and excretion of 14C-Plitidepsin in patients with advanced cancer

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.

Plitidepsin: design, development, and potential place in therapy

Plitidepsin is a cyclic depsipeptide that was first isolated from a Mediterranean marine tunicate (Aplidium albicans) and, at present, is manufactured by total synthesis and commercialized as Aplidin®. Its antitumor activity, observed in preclinical in vitro and in vivo studies has prompted numerous clinical trials to be conducted over the last 17 years, alone or in combination with other anticancer agents. Single-agent plitidepsin has shown limited antitumor activity and a tolerable safety profile in several malignancies, such as noncutaneous peripheral T-cell lymphoma, melanoma, and multiple myeloma. In patients with relapsed or refractory multiple myeloma, plitidepsin activity seems to be enhanced after addition of dexamethasone while remaining well tolerated, and a Phase III trial comparing plitidepsin plus dexamethasone vs dexamethasone alone is underway. Additional studies are required to better define the role of plitidepsin in combination with other active agents in these indications. Results of plitidepsin activity in other hematological malignancies or solid tumors have been disappointing so far. Further studies analyzing its mechanisms of action and potential biomarkers will help select patients who may benefit most from this drug. In this review, we critically analyze the published studies on plitidepsin in hematological malignancies and solid tumors and discuss its current role and future perspectives in treating these malignancies. We also review its design, pharmaceutical data, and mechanism of action.

Isolation and characterization of marine Brevibacillus sp. S-1 collected from South China Sea and a novel antitumor peptide produced by the strain

A Gram-positive, rod-shaped bacterium, designated as S-1, was isolated from a marine sediment sample collected from South China Sea. Phylogenetic analysis based on 16S rRNA gene sequence showed that S-1 belongs to the genus Brevibacillus. A novel cytotoxic peptide was isolated from the fermentation broth of the marine-derived bacterium Brevibacillus sp. S-1, using ion-exchange chromatography and reverse-phase HPLC chromatography. The molecular weight of this peptide was determined as 1570 Da by MALDI-TOF mass spectrometry, and its structure was proposed as a cyclic peptide elucidated by MALDI-TOF/TOF mass spectrometry and de novo sequencing. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay showed that this peptide exhibited cytotoxicity against BEL-7402 human hepatocellular carcinoma cells, RKO human colon carcinoma cells, A549 human lung carcinoma cells, U251 human glioma cells and MCF-7 human breast carcinoma cells. Additionally, SBP exhibited low cytotoxicity against HFL1 human normal fibroblast lung cells. The result suggested that the cytotoxic effect of the peptide is specific to tumor cells.

Targeting cellular apoptotic pathway with peptides from marine organisms

Apoptosis is a critical defense mechanism against the formation and progression of cancer and exhibits distinct morphological and biochemical traits. Targeting apoptotic pathways becomes an intriguing strategy for the development of chemotherapeutic agents. Peptides from marine organisms have become important sources in the discovery of antitumor drugs, especially when modern technology makes it more and more feasible to collect organisms from seas. This primer summarizes several marine peptides, based on their effects on apoptotic signaling pathways, although most of these peptides have not yet been studied in depth for their mechanisms of action. Novel peptides that induce an apoptosis signal pathway are presented in association with their pharmacological properties.

Multicenter phase II study of plitidepsin in patients with relapsed/refractory non-Hodgkin's lymphoma

This phase II clinical trial evaluated the efficacy, safety and pharmacokinetics of plitidepsin 3.2 mg/m(2) administered as a 1-hour intravenous infusion weekly on days 1, 8 and 15 every 4 weeks in 67 adult patients with relapsed/refractory aggressive non-Hodgkin's lymphoma. Patients were divided into two cohorts: those with non-cutaneous peripheral T-cell lymphoma (n=34) and those with other lymphomas (n=33). Efficacy was evaluated using the International Working Group criteria (1999). Of the 29 evaluable patients with non-cutaneous peripheral T-cell lymphoma, six had a response (overall response rate 20.7%; 95% confidence interval, 8.0%-39.7%), including two complete responses and four partial responses. No responses occurred in the 30 evaluable patients with other lymphomas (including 27 B-cell lymphomas). The most common plitidepsin-related adverse events were nausea, fatigue and myalgia (grade 3 in <10% of cases). Severe laboratory abnormalities (lymphopenia, anemia, thrombocytopenia, and increased levels of transaminase and creatine phosphokinase) were transient and easily managed by plitidepsin dose adjustments. The pharmacokinetic profile did not differ from that previously reported in patients with solid tumors. In conclusion, plitidepsin monotherapy has clinical activity in relapsed/refractory T-cell lymphomas. Combinations of plitidepsin with other chemotherapeutic drugs deserve further evaluation in patients with non-cutaneous peripheral T-cell lymphoma. (clinicaltrials.gov identifier: NCT00884286).

Antitumor peptides from marine organisms

The biodiversity of the marine environment and the associated chemical diversity constitute a practically unlimited resource of new antitumor agents in the field of the development of marine bioactive substances. In this review, the progress on studies of antitumor peptides from marine sources is provided. The biological properties and mechanisms of action of different marine peptides are described; information about their molecular diversity is also presented. Novel peptides that induce apoptosis signal pathway, affect the tubulin-microtubule equilibrium and inhibit angiogenesis are presented in association with their pharmacological properties. It is intended to provide useful information for further research in the fields of marine antitumor peptides.

Plitidepsin has a safe cardiac profile: a comprehensive analysis

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.

Population pharmacokinetics of PM00104 (Zalypsis(®)) in cancer patients

OBJECTIVE

The aim of this study was to characterize the population pharmacokinetics of PM00104 (Zalypsis(®)) in cancer patients.

METHODS

A total of 135 patients included in four phase I clinical trials who receive intravenous PM00104 at doses ranging from 53 to 5,000 μg/m(2) and administered as 1-, 3-, or 24-h infusion every 3 weeks or as 1-h infusion on days 1, 8, and 15 of a 28-day cycle, or 1-h infusion daily during 5 consecutive days every 3 weeks were included in the analysis. Pharmacokinetic data were analyzed with non-linear mixed effect model using NONMEM VI software. The effect of selected patient covariates on PM00104 pharmacokinetics was investigated. Model evaluation was performed using predictive checks and non-parametric bootstrap.

RESULTS

An open four-compartment catenary linear model with first-order elimination was developed to best describe the data. Plasma clearance and its between-subject variability was 43.7 L/h (34%). Volume of distribution at steady state was 822 L (117%). Within the range of covariates studied, age, sex, body size variables, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total bilirubin, lactate dehydrogenase, creatinine clearance, albumin, total protein, hemoglobin, performance status, liver metastases, dose-limiting toxicity, and stable disease for 3 months were not statistically related to PM00104 pharmacokinetic parameters. Bootstrap and posterior predictive check evidenced the model was deemed appropriate to describe the time course of PM00104 plasma concentrations in cancer patients.

CONCLUSIONS

The integration of phase I pharmacokinetic data demonstrated PM00104 linear elimination from plasma, dose proportionality up to 5,000 μg/m(2), and time-independent pharmacokinetics. No clinically relevant covariates were identified as predictors of PM00104 pharmacokinetics.

Fixed dosing versus body size-based dosing of therapeutic peptides and proteins in adults

Therapeutic biologics are often administered based on body size. A previous study has found that fixed dosing performs similarly to body size-based dosing in reducing intersubject variability in drug exposure across the mAbs studied. This study extended this evaluation to other therapeutic proteins and peptides. Eighteen therapeutic proteins and peptides with published population pharmacokinetic (PK) and/or pharmacodynamic (PD) models were selected for dosing approach evaluation. The relationships between body size and drug exposure (and PD end point when available) were evaluated, and simulation studies were conducted to compare the performance of the 2 dosing approaches. The results showed that fixed dosing performed better for 12 of 18 selected biologics in terms of reducing intersubject variability in exposure at both population and individual levels, whereas body size-based dosing performed better for the other 6 molecules. This result is consistent with the findings for mAbs. Therefore, fixed dosing is recommended for first-in-human studies of proteins and peptides along with mAbs. The final dosing approach for phase 3 studies should be determined based on a full assessment of body size effect on PK/PD when data are available and the therapeutic window of the drug.

Cyclodepsipeptides from marine sponges: natural agents for drug research

A number of natural products from marine sponges, such as cyclodepsipeptides, have been identified. The structural characteristics of this family of cyclic peptides include various unusual amino acid residues and unique N-terminal polyketide-derived moieties. Papuamides are representatives of a class of marine sponge derived cyclic depsipeptides, including callipeltin A, celebesides A and B, homophymine A, mirabamides, microspinosamide, neamphamide A and theopapuamides. They are thought to have cytoprotective activity against HIV-1 in vitro by inhibiting viral entry. Jasplakinolide, a representative member of marine sponge-derived cyclodepsipeptides that include arenastatin A, geodiamolides, homophymines, spongidepsin and theopapuamides, is a potent inducer of actin polymerization in vitro. Although actin dynamics is essential for tumor metasasis, no actin targeting drugs have been used in clinical trials due to their severe cytotoxicity. Nonetheless, the actin cytoskeleton remains a potential target for anti-cancer drug development. These features imply the use of cyclodepsipeptides as molecular models in drug research.