Phase I and Pharmacokinetic Study of Aplidine, a New Marine Cyclodepsipeptide in Patients With Advanced Malignancies

Didemnins as marine-derived anticancer agents: mechanistic insights and clinical potential

Didemnins, a class of cyclic depsipeptides derived from marine organisms exhibit notable anticancer properties. Among them, Didemnin B has been extensively researched for its strong antitumor activity and progression to clinical trials. Nonetheless, its clinical application has been impeded by challenges like poor bioavailability and dose-limiting toxicity. This review aims to provide a comprehensive analysis of the anticancer mechanisms of Didemnins, particularly Didemnin B, by examining studies that investigate their anticancer properties, mechanisms of action, pharmacokinetics, and clinical outcomes, while exploring their potential as therapeutic agents in cancer treatment. A comprehensive review of the literature was conducted using scientific databases, including PubMed, Google Scholar and ScienceDirect. Didemnin B has been shown to exert its anticancer effects primarily through the inhibition of protein synthesis, induction of apoptosis, and disruption of cell-cycle progression. Despite promising preclinical results, clinical trials have revealed substantial toxicity, particularly neuromuscular and hepatic, which significantly constrains its therapeutic potential. Recent progress in developing semisynthetic derivatives, including Dehydrodidemnin B (Plitidepsin, Aplidin), have led to improved efficacy and reduced toxicity. Didemnins, especially Didemnin B, hold promise as anticancer agents. However, future research should focus on optimizing delivery methods, reducing toxicity, and exploring combination therapies to enhance their therapeutic potential in oncology.

Recent progress of protein kinase inhibitors derived from marine peptides for developing anticancer agents

Protein kinases, mediating their biological function via their catalytic activity, play important role in cell development, including cell proliferation, migration, angiogenesis and survival. Over the years, protein kinase inhibitors have been developed as an important class of anticancer agents clinically. However, the off-targeting and drug resistance of protein kinase inhibitors limit their efficiency. Anticancer peptides derived from marine organisms represent a novel class of bioactive substances, and some of the peptides exhibit anticancer effect via inhibiting protein kinases. In this mini review, the recent progress of anticancer peptides targeting protein kinases from marine sources are presented. Marine peptides inhibiting resistant cancer cells by targeting novel domains of protein kinases are highlighted. The challenges and prospects of developing marine peptides as anticancer agents are also discussed.

Marine-Derived Anticancer Agents Targeting Apoptotic Pathways: Exploring the Depths for Novel Cancer Therapies

Extensive research has been conducted on the isolation and study of bioactive compounds derived from marine sources. Several natural products have demonstrated potential as inducers of apoptosis and are currently under investigation in clinical trials. These marine-derived compounds selectively interact with extrinsic and intrinsic apoptotic pathways using a variety of molecular mechanisms, resulting in cell shrinkage, chromatin condensation, cytoplasmic blebs, apoptotic bodies, and phagocytosis by adjacent parenchymal cells, neoplastic cells, or macrophages. Numerous marine-derived compounds are currently undergoing rigorous examination for their potential application in cancer therapy. This review examines a total of 21 marine-derived compounds, along with their synthetic derivatives, sourced from marine organisms such as sponges, corals, tunicates, mollusks, ascidians, algae, cyanobacteria, fungi, and actinobacteria. These compounds are currently undergoing preclinical and clinical trials to evaluate their potential as apoptosis inducers for the treatment of different types of cancer. This review further examined the compound's properties and mode of action, preclinical investigations, clinical trial studies on single or combination therapy, and the prospective development of marine-derived anticancer therapies.

Update on Autophagy Inhibitors in Cancer: Opening up to a Therapeutic Combination with Immune Checkpoint Inhibitors

Autophagy is a highly conserved and natural degradation process that helps maintain cell homeostasis through the elimination of old, worn, and defective cellular components, ensuring proper cell energy intake. The degradative pathway constitutes a protective barrier against diverse human diseases including cancer. Autophagy basal level has been reported to be completely dysregulated during the entire oncogenic process. Autophagy influences not only cancer initiation, development, and maintenance but also regulates cancer response to therapy. Currently, autophagy inhibitor candidates mainly target the early autophagy process without any successful preclinical/clinical development. Lessons learned from autophagy pharmaceutical manipulation as a curative option progressively help to improve drug design and to encounter new targets of interest. Combinatorial strategies with autophagy modulators are supported by abundant evidence, especially dealing with immune checkpoint inhibitors, for which encouraging preclinical results have been recently published. GNS561, a PPT1 inhibitor, is a promising autophagy modulator as it has started a phase 2 clinical trial in liver cancer indication, combined with atezolizumab and bevacizumab, an assessment without precedent in the field. This approach paves a new road, leading to the resurgence of anticancer autophagy inhibitors as an attractive therapeutic target in cancer.

Marine Compounds, Mitochondria, and Malignancy: A Therapeutic Nexus

The marine environment is important yet generally underexplored. It contains new sources of functional constituents that can affect various pathways in food processing, storage, and fortification. Bioactive secondary metabolites produced by marine microorganisms may have significant potential applications for humans. Various components isolated from disparate marine microorganisms, including fungi, microalgae, bacteria, and myxomycetes, showed considerable biological effects, such as anticancer, antioxidant, antiviral, antibacterial, and neuroprotective activities. Growing studies are revealing that potential anticancer effects of marine agents could be achieved through the modulation of several organelles. Mitochondria are known organelles that influence growth, differentiation, and death of cells via influencing the biosynthetic, bioenergetic, and various signaling pathways related to oxidative stress and cellular metabolism. Consequently, mitochondria play an essential role in tumorigenesis and cancer treatments by adapting to alterations in environmental and cellular conditions. The growing interest in marine-derived anticancer agents, combined with the development and progression of novel technology in the extraction and cultures of marine life, led to revelations of new compounds with meaningful pharmacological applications. This is the first critical review on marine-derived anticancer agents that have the potential for targeting mitochondrial function during tumorigenesis. This study aims to provide promising strategies in cancer prevention and treatment.

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.

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.

Can be marine bioactive peptides (MBAs) lead the future of foodomics for human health?

Marine organisms are considered a cache of biologically active metabolites with pharmaceutical, functional, and nutraceutical properties. Among these, marine bioactive peptides (MBAs) present in diverse marine species (fish, sponges, cyanobacteria, fungi, ascidians, seaweeds, & mollusks) have acquired attention owing to their broad-spectrum health-promoting benefits. Nowadays, scientists are keener exploring marine bioactive peptides precisely due to their unique structural and biological properties. These MBAs have reported ameliorating potential against different diseases like hypertension, diabetes, obesity, HIV, cancer, oxidation, and inflammation. Furthermore, MBAs isolated from various marine organisms may also have a beneficial role in the cosmetic, nutraceutical, and food industries. Few marine peptides and their derivative are approved for commercial use, while many MBAs are in various pre-clinical and clinical trials. This review mainly focuses on the diversity of marine bioactive peptides in marine organisms and their production procedures, such as chemical and enzymatic hydrolysis. Moreover, MBAs' therapeutic and biological potential has also been critically discussed herein, along with their status in drug discovery, pre-clinical and clinical trials.

Use of anticancer peptides as an alternative approach for targeted therapy in breast cancer: a review

Breast cancer is the most common cancer in women worldwide. Traditional therapies are expensive and cause severe side effects. Targeted therapy is a powerful method to circumvent the problems of other therapies. It also allows drugs to localize at predefined targets in a selective manner. Currently, there are several monoclonal antibodies which target breast cancer cell surface markers. However, using antibodies has some limitations. In the last two decades, many investigators have discovered peptides that may be useful to target breast cancer cells. In this article, we provide an overview on anti-breast cancer peptides, their sources and biological activities. We further discuss the pros and cons of using anticancer peptides with further emphasis on how to improve their effectiveness in cancer therapy.

Inhibitors of Eukaryotic Translational Machinery as Therapeutic Agents

Inhibiting eukaryotic protein translation with small molecules is emerging as a powerful therapeutic strategy. The advantage of targeting cellular translational machinery is that it is required for the highly proliferative state of many neoplastic cells, replication of certain viruses, and ultimately the expression of a wide variety of protein targets. Although, this approach has been exploited to develop clinical agents, such as homoharringtonine (HHT, 1), used to treat chronic myeloid leukemia (CML), inhibiting components of the translational machinery is often associated with cytotoxic phenotypes. However, recent studies have demonstrated that certain small molecules can inhibit the translation of specific subsets of proteins, leading to lower cytotoxicity, and opening-up therapeutic opportunities for translation inhibitors to be deployed in indications beyond oncology and infectious disease. This review summarizes efforts to develop inhibitors of the eukaryotic translational machinery as therapeutic agents and highlights emerging opportunities for translation inhibitors in the future.

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.

Plitidepsin: a potential new treatment for relapsed/refractory multiple myeloma

Plitidepsin is a marine-derived anticancer compound isolated from the Mediterranean tunicate Applidium albicans. It exerts pleiotropic effects on cancer cells, most likely by binding to the eukaryotic translation eEF1A2. This ultimately leads to cell-cycle arrest, growth inhibition and induction of apoptosis via multiple pathway alterations. Recently, a Phase III randomized trial in patients with relapsed/refractory multiple myeloma reported outcomes for plitidepsin plus dexamethasone compared with dexamethasone. Median progression-free survival was 3.8 months in the plitidepsin arm and 1.9 months in the dexamethasone arm (HR: 0.611; p = 0.0048). Here, we review preclinical data regarding plitidepsins mechanism of action, give an overview of clinical trial results across different tumor types as well as the latest results in multiple myeloma.

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.

Starvation tactics using natural compounds for advanced cancers: pharmacodynamics, clinical efficacy, and predictive biomarkers

The high mortality associated with oncological diseases is mostly due to tumors in advanced stages, and their management is a major challenge in modern oncology. Angiogenesis is a defined hallmark of cancer and predisposes to metastatic invasion and dissemination and is therefore an important druggable target for cancer drug discovery. Recently, because of drug resistance and poor prognosis, new anticancer drugs from natural sources targeting tumor vessels have attracted more attention and have been used in several randomized and controlled clinical trials as therapeutic options. Here, we outline and discuss potential natural compounds as salvage treatment for advanced cancers from recent and ongoing clinical trials and real-world studies. We also discuss predictive biomarkers for patients' selection to optimize the use of these potential anticancer drugs.

Antitumour bioactive peptides isolated from marine organisms

Marine organisms are an important source of antitumour active substances. Thus, pharmaceutical research in recent years has focused on exploring new antitumour drugs derived from marine organisms, and, many peptide drugs with strong antitumour activities have been successfully extracted. Based on different mechanisms, this paper reviews the research on several typical antitumour bioactive peptides in marine drugs and the latest progress therein. Additionally, the development prospects for these antitumour bioactive peptide-based drugs are discussed so as to provide a reference for future research in this field.

Therapeutic Properties and Biological Benefits of Marine-Derived Anticancer Peptides

Various organisms exist in the oceanic environment. These marine organisms provide an abundant source of potential medicines. Many marine peptides possess anticancer properties, some of which have been evaluated for treatment of human cancer in clinical trials. Marine anticancer peptides kill cancer cells through different mechanisms, such as apoptosis, disruption of the tubulin-microtubule balance, and inhibition of angiogenesis. Traditional chemotherapeutic agents have side effects and depress immune responses. Thus, the research and development of novel anticancer peptides with low toxicity to normal human cells and mechanisms of action capable of avoiding multi-drug resistance may provide a new method for anticancer treatment. This review provides useful information on the potential of marine anticancer peptides for human therapy.

Anticancer potential of bioactive peptides from animal sources (Review)

Cancer is the most common cause of human death worldwide. Conventional anticancer therapies, including chemotherapy and radiation, are associated with severe side effects and toxicities as well as low specificity. Peptides are rapidly being developed as potential anticancer agents that specifically target cancer cells and are less toxic to normal tissues, thus making them a better alternative for the prevention and management of cancer. Recent research has focused on anticancer peptides from natural animal sources, such as terrestrial mammals, marine animals, amphibians, and animal venoms. However, the mode of action by which bioactive peptides inhibit the proliferation of cancer cells remains unclear. In this review, we present the animal sources from which bioactive peptides with anticancer activity are derived and discuss multiple proposed mechanisms by which these peptides exert cytotoxic effects against cancer cells.

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.

Metabolite profiling of ascidian Styela plicata using LC-MS with multivariate statistical analysis and their antitumor activity

To identify the metabolite distribution in ascidian, we have applied an integrated liquid chromatography- tandem mass spectrometry (LC-MS) metabolomics approach to explore and identify patterns in chemical diversity of invasive ascidian Styela plicata. A total of 71 metabolites were reported among these alkaloids, fatty acids and lipids are the most dominant chemical group. Multivariate statistical analysis, principal component analysis (PCA) showed a clear separation according to chemical diversity and taxonomic groups. PCA and partial least square discriminant analysis were applied to discriminate the chemical group of S. plicata crude compounds and classify the compounds with unknown biological activities. In this study, we reported for the first time that a partially purified methanol extract prepared from the ascidian S. plicata and Ascidia mentula possess antitumor activity against four tumor cell lines with different tumor histotype, such as HeLa (cervical carcinoma), HT29 (colon carcinoma), MCF-7 (breast carcinoma) and M14 (melanoma). S. plicata fraction SP-50 showed strong inhibition of cell proliferation and induced apoptosis in HeLa and HT29 cells, thus indicating S. plicata fraction SP-50 a potential lead compound for anticancer therapy. The molecular mechanism of action and chemotherapeutic potential of these ascidian unknown biomolecules need further research.

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.

Cyclic depsipeptides as potential cancer therapeutics

Cyclic depsipeptides are polypeptides in which one or more amino acid is replaced by a hydroxy acid, resulting in the formation of at least one ester bond in the core ring structure. Many natural cyclic depsipeptides possessing intriguing structural and biological properties, including antitumor, antifungal, antiviral, antibacterial, anthelmintic, and anti-inflammatory activities, have been identified from fungi, plants, and marine organisms. In particular, the potent effects of cyclic depsipeptides on tumor cells have led to a number of clinical trials evaluating their potential as chemotherapeutic agents. Although many of the trials have not achieved the desired results, romidepsin (FK228), a bicyclic depsipeptide that inhibits histone deacetylase, has been shown to have clinical efficacy in patients with refractory cutaneous T-cell lymphoma and has received Food and Drug Administration approval for use in treatment. In this review, we discuss antitumor cyclic depsipeptides that have undergone clinical trials and focus on their structural features, mechanisms, potential applications in chemotherapy, and pharmacokinetic and toxicity data. The results of this study indicate that cyclic depsipeptides could be a rich source of new cancer therapeutics.

Aplidin in patients with advanced dedifferentiated liposarcomas: a French Sarcoma Group Single-Arm Phase II study

BACKGROUND

Preclinical data have suggested a therapeutic role of JUN pathway activation in dedifferentiated liposarcoma (DDLPS) tumorigenesis. Aplidin is a drug inducing apoptosis through a strong, sustained activation of c-Jun NH2-terminal kinase.

METHODS

This phase II trial included patients with progressive advanced DDLPS. They received Aplidin 5 mg/m(2) days 1-15, 28-day cycle until disease progression or unacceptable toxicity. The primary end point was the 3-month nonprogression rate (PFS3) defined as the proportion of patients with nonprogressive disease at 3 months. A PFS3 of 40% considered as a reasonable objective to claim drug efficacy.

RESULTS

Between August 2012 and May 2013, 24 patients were included. Sixteen had received prior chemotherapy. Twenty-two were assessable for efficacy. The PFS3 was 9.1% [95% confidence interval (CI) 1.1-29.2]. Median progression-free and overall survivals were 1.6 months (95% CI 1.4-2.6) and 9.2 months (95% CI 6.6-). The most frequent adverse events of any grade were nausea, fatigue, anorexia, vomiting and diarrhea.

CONCLUSION

Aplidin did not meet the primary end point of this trial and do not deserve further investigation in DDLPS.

CLINICALTRIALSGOV IDENTIFIER

NCT01876043.

Antiproliferative effect of Dendrobium catenatum Lindley polypeptides against human liver, gastric and breast cancer cell lines

Ten sub-peptides from Dendrobium catenatum Lindley contained in fraction A3 were separated. Fraction A3 exhibited anti-proliferative activity against cancer cells.

Nano-encapsulation of plitidepsin: in vivo pharmacokinetics, biodistribution, and efficacy in a renal xenograft tumor model

PURPOSE

Plitidepsin is an antineoplasic currently in clinical evaluation in a phase III trial in multiple myeloma (ADMYRE). Presently, the hydrophobic drug plitidepsin is formulated using Cremophor®, an adjuvant associated with unwanted hypersensitivity reactions. In search of alternatives, we developed and tested two nanoparticle-based formulations of plitidepsin, aiming to modify/improve drug biodistribution and efficacy.

METHODS

Using nanoprecipitation, plitidepsin was loaded in polymer nanoparticles made of amphiphilic block copolymers (i.e. PEG-b-PBLG or PTMC-b-PGA). The pharmacokinetics, biodistribution and therapeutic efficacy was assessed using a xenograft renal cancer mouse model (MRI-H-121 xenograft) upon administration of the different plitidepsin formulations at maximum tolerated multiple doses (0.20 and 0.25 mg/kg for Cremophor® and copolymer formulations, respectively).

RESULTS

High plitidepsin loading efficiencies were obtained for both copolymer formulations. Considering pharmacokinetics, PEG-b-PBLG formulation showed lower plasma clearance, associated with higher AUC and Cmax than Cremophor® or PTMC-b-PGA formulations. Additionally, the PEG-b-PBLG formulation presented lower liver and kidney accumulation compared with the other two formulations, associated with an equivalent tumor distribution. Regarding the anticancer activity, all formulations elicited similar efficacy profiles, as compared to the Cremophor® formulation, successfully reducing tumor growth rate.

CONCLUSIONS

Although the nanoparticle formulations present equivalent anticancer activity, compared to the Cremophor® formulation, they show improved biodistribution profiles, presenting novel tools for future plitidepsin-based therapies.

Current scenario of peptide-based drugs: the key roles of cationic antitumor and antiviral peptides

Cationic antimicrobial peptides (AMPs) and host defense peptides (HDPs) show vast potential as peptide-based drugs. Great effort has been made in order to exploit their mechanisms of action, aiming to identify their targets as well as to enhance their activity and bioavailability. In this review, we will focus on both naturally occurring and designed antiviral and antitumor cationic peptides, including those here called promiscuous, in which multiple targets are associated with a single peptide structure. Emphasis will be given to their biochemical features, selectivity against extra targets, and molecular mechanisms. Peptides which possess antitumor activity against different cancer cell lines will be discussed, as well as peptides which inhibit virus replication, focusing on their applications for human health, animal health and agriculture, and their potential as new therapeutic drugs. Moreover, the current scenario for production and the use of nanotechnology as delivery tool for both classes of cationic peptides, as well as the perspectives on improving them is considered.

Phase I-II study of plitidepsin and dacarbazine as first-line therapy for advanced melanoma

BACKGROUND

This phase I-II trial compared plitidepsin 1-h infusion alone or combined with dacarbazine (DTIC) 1-h infusion as front-line therapy for advanced melanoma.

METHODS

The recommended dose (RD) for plitidepsin/DTIC was defined in the first stage. In the second stage, patients were randomised to receive single-agent plitidepsin 3.2 mg m(-2) (n = 20) on days 1, 8 and 15 every 4 weeks (q4wk) or plitidepsin 2.4 mg m(-2) on days 1, 8 and 15 q4wk combined with DTIC 800 mg m(-2) q4wk (n = 38).

RESULTS

The overall response rate with plitidepsin/DTIC was 21.4%; all responders had normal serum lactate dehydrogenase (LDH) levels and performance status ≤ 1 at baseline. Median progression-free survival (PFS) with plitidepsin/DTIC was 3.3 months in all patients, and 4.3 months in those with baseline normal LDH. No responses occurred with single-agent plitidepsin and median PFS was 1.5 months. Both regimens were well tolerated. Haematological abnormalities were more common and transaminase increases more severe with plitidepsin/DTIC. Treatment-related transaminase increases leading to infusion omission on day 8 were relatively common. No drug-drug pharmacokinetic interactions were found.

CONCLUSION

This plitidepsin/DTIC schedule has antitumour activity and manageable toxicity in advanced melanoma. Further evaluation of plitidepsin 2.4 mg m(-2) fortnightly and DTIC 800 mg m(-2) q4wk is recommended.

c-Jun N-terminal kinase phosphorylation is a biomarker of plitidepsin activity

Plitidepsin is an antitumor drug of marine origin currently in Phase III clinical trials in multiple myeloma. In cultured cells, plitidepsin induces cell cycle arrest or an acute apoptotic process in which sustained activation of c-Jun N-terminal kinase (JNK) plays a crucial role. With a view to optimizing clinical use of plitidepsin, we have therefore evaluated the possibility of using JNK activation as an in vivo biomarker of response. In this study, we show that administration of a single plitidepsin dose to mice xenografted with human cancer cells does indeed lead to increased phosphorylation of JNK in tumors at 4 to 12 h. By contrast, no changes were found in other in vitro plitidepsin targets such as the levels of phosphorylated-ERK, -p38MAPK or the protein p27^KIP1. Interestingly, plitidepsin also increased JNK phosphorylation in spleens from xenografted mice showing similar kinetics to those seen in tumors, thereby suggesting that normal tissues might be useful for predicting drug activity. Furthermore, plitidepsin administration to rats at plasma concentrations comparable to those achievable in patients also increased JNK phosphorylation in peripheral mononuclear blood cells. These findings suggest that changes in JNK activity provide a reliable biomarker for plitidepsin activity and this could be useful for designing clinical trials and maximizing the efficacy of plitidepsin.

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.

Solid phase versus solution phase synthesis of heterocyclic macrocycles

Comparing a solution phase route to a solid phase route in the synthesis of the cytotoxic natural product urukthapelstatin A (Ustat A) confirmed that a solid phase method is superior. The solution phase approach was tedious and involved cyclization of a ridged heterocyclic precursor, while solid phase allowed the rapid generation of a flexible linear peptide. Cyclization of the linear peptide was facile and subsequent generation of three oxazoles located within the structure of Ustat A proved relatively straightforward. Given the ease with which the oxazole Ustat A precursor is formed via our solid phase approach, this route is amenable to rapid analog synthesis.

Plitidepsin (Aplidin) is a potent inhibitor of diffuse large cell and Burkitt lymphoma and is synergistic with rituximab

Plitidepsin (Aplidin), an antitumor agent of marine origin, presently is undergoing phase II/III clinical trials, and has shown promise for the treatment of lymphoma. Here, we describe the antitumor effects of plitidepsin alone and in combination with rituximab and investigated the effects of each drug and the combination on the cell cycle and mechanism of cell death. Several Diffuse Large Cell Lymphoma (DLCL) lines and Burkitt cell lines were tested for sensitivity to plitidepsin and rituximab. All DLCL and Burkitt lymphoma cell lines were inhibited by plitidepsin in nanomolar concentrations, while rituximab sensitivity varied among different cell lines. Ramos and the RL cell lines proved sensitive to rituximab and were used to test the effects of each of the two drugs. The two agents exhibited synergism at all tested concentrations. For in vivo studies, irradiated athymic nude mice were engrafted with the Ramos lymphoma. Treatment was initiated when the tumors were ~0.5 cm in diameter, and toxic and therapeutic effects were monitored. In the in vivo study, additive effects of the combined two drugs, was demonstrated without an increase in host toxicity. The in vitro synergy and the in vivo additive antitumor effects without an increase in host toxicity with two relatively non-marrow suppressive agents encourages further development of this combination for treatment of aggressive B-cell lymphomas.

Bioactive peptides and depsipeptides with anticancer potential: sources from marine animals

Biologically active compounds with different modes of action, such as, antiproliferative, antioxidant, antimicrotubule, have been isolated from marine sources, specifically algae and cyanobacteria. Recently research has been focused on peptides from marine animal sources, since they have been found as secondary metabolites from sponges, ascidians, tunicates, and mollusks. The structural characteristics of these peptides include various unusual amino acid residues which may be responsible for their bioactivity. Moreover, protein hydrolysates formed by the enzymatic digestion of aquatic and marine by-products are an important source of bioactive peptides. Purified peptides from these sources have been shown to have antioxidant activity and cytotoxic effect on several human cancer cell lines such as HeLa, AGS, and DLD-1. These characteristics imply that the use of peptides from marine sources has potential for the prevention and treatment of cancer, and that they might also be useful as molecular models in anticancer drug research. This review focuses on the latest studies and critical research in this field, and evidences the immense potential of marine animals as bioactive peptide sources.

Didemnins, tamandarins and related natural products

Since the discovery and isolation of the didemnin family of marine depsipeptides in 1981, the synthesis and biological activity of its congeners have been of great interest to the scientific community. The didemnins have demonstrated antitumor, antiviral, and immunosuppressive activity at low nano- and femtomolar levels. Of the congeners, didemnin B was the first marine natural product to reach phase II clinical trials in the United States, stimulating many analogue syntheses to date. About two decades later, tamandarins A and B were isolated, and were found to possess very similar structure and biological activity to that of the didemnin B. These compounds have shown impressive biological activity and some progress has been made in establishing structure-activity relationships. However, their molecular mechanism of action still remains unclear. This review highlights the long-standing study of didemnins and its critical application towards the understanding of the molecular mechanism of action of tamandarins and their potential use as therapeutic agents.

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.

Design and synthesis of Hsp90 inhibitors: exploring the SAR of Sansalvamide A derivatives

Utilizing the structure-activity relationship we have developed during the synthesis of the first two generations and mechanism of action studies that point to the interaction of these molecules with the key oncogenic protein Hsp90, we report here the design of 32 new Sansalvamide A derivatives and their synthesis. Our new structures, designed from previously reported potent compounds, were tested for cytotoxicity on the HCT116 colon cancer cell line, and their binding to the biological target was analyzed using computational studies involving blind docking of derivatives using Autodock. Further, we show new evidence that our molecules bind directly to Hsp90 and modulate Hsp90's binding with client proteins. Finally, we demonstrate that we have integrated good ADME properties into a new derivative.

Molecular and other novel advances in treatment of metastatic epithelial and medullary thyroid cancers

An understanding of the mutations of the proto-oncogenes and tumor suppressor genes that occur in thyroid cancers should eventually explain the diverse clinical characteristics of these tumors and also direct therapy. Some insights have already emerged in the last decade; some abnormalities in tumor genes are consistently associated with specific clinical and pathologic findings. These genetic abnormalities usually represent somatic mutations in tumors of follicular epithelial origin, as opposed to inherited mutations in medullary thyroid cancers of parafollicular C cells origin because most thyroid tumors are sporadic and not familial. This is different from the multiple endocrine neoplasia syndromes in which the primary tumorigenic gene mutations are inherited. This improved understanding of the molecular basis of these diseases has led to the development of novel targeted therapeutic approaches which will be discussed in this paper.

Phase I study of weekly plitidepsin as 1-hour infusion combined with carboplatin in patients with advanced solid tumors or lymphomas

This dose-escalating phase I clinical trial was designed to determine the recommended dose (RD) and to assess the safety and feasibility of weekly plitidepsin (1-hour i.v. infusion, Days 1, 8 and 15) combined with carboplatin (1-hour i.v. infusion, Day 1, after plitidepsin) in 4-week (q4wk) cycles given to patients with advanced solid tumors or lymphomas. Twenty patients were enrolled and evaluable for both safety and efficacy. The starting dose was plitidepsin 1.8 mg/m(2) and carboplatin area under the curve (AUC) = 5 min*mg/ml; dose escalation proceeded based on worst toxicity in the previous cohort. The maximum tolerated dose (MTD) was plitidepsin 3.0 mg/m(2) and carboplatin AUC = 5 min*mg/ml, with grade 3 transaminase increases as the most common dose-limiting toxicities (DLTs). The RD for phase II studies was plitidepsin 2.4 mg/m(2) and carboplatin AUC = 5 min*mg/ml, with fatigue, myalgia and nausea as the most common drug-related adverse events (AEs). No unexpected toxicity was seen. Twelve patients (60%), ten of whom were heavily pretreated (≥2 previous chemotherapy lines) showed stable disease (SD), with a median time to progression (TTP) of 4.4 months. In conclusion, plitidepsin 2.4 mg/m(2) and carboplatin AUC = 5 min*mg/ml is a safe dose for future phase II studies evaluating the use of this combination in cancer patients potentially sensitive to platinum-based therapy.

Synthetic studies of tamandarin B side chain analogues

The syntheses of three tamandarin B analogues are described. The goal of these studies was to prepare material to determine their relative therapeutic index and to gain an oversight as to their potential for clinical applications.

Reports of clinical benefit of plitidepsin (Aplidine), a new marine-derived anticancer agent, in patients with advanced medullary thyroid carcinoma

OBJECTIVES

To assess clinical benefit of plitidepsin (Aplidine) in patients with advanced medullary thyroid carcinoma (MTC).

MATERIALS AND METHODS

We retrospectively reported the outcome of 10 patients with advanced MTC among 215 patients who have entered the phase I program with plitidepsin.

RESULTS

Median number of cycles was 5. Using World Health Organization criteria, 1 among 5 patients with measurable disease displayed a confirmed partial response, whereas 8 patients experienced a stable disease, and 1 patient had a progressive disease, corresponding to a disease control rate of 90%. Two patients treated at the maximum tolerated dose experienced muscular dose-limiting toxicity possibly related to palmitoyl transferase inhibition. One of these 2 patients was able to continue therapy with no dose reduction with the prophylactic addition of l-carnitine, which is used in the treatment of the carnitine palmitoyl transferase deficiency type 2.

DISCUSSION

Plitidepsin seems to be able to induce clinical benefit in patients with pretreated MTC, and its toxicity has been manageable at the recommended dose.

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.

Phase II study of plitidepsin 3-hour infusion every 2 weeks in patients with unresectable advanced medullary thyroid carcinoma

OBJECTIVES

To evaluate the antitumor response, time-to-event efficacy endpoints and toxicity of plitidepsin (Aplidin) 5 mg/m as a 3-hour intravenous (i.v.) infusion every 2 weeks in patients with unresectable advanced medullary thyroid carcinoma (MTC).

METHODS

Sixteen patients with MTC and disease progression or large tumor burden received plitidepsin. Tumor response and time-related parameters were evaluated according to Response Evaluation Criteria in Solid Tumors. Secondary efficacy endpoints were marker response (calcitonin and carcinoembryonic antigen), clinical benefit and quality of life. Safety was assessed using the National Cancer Institute Common Toxicity Criteria.

RESULTS

A total of 141 cycles (median, 9 per patient; range, 1-24) were administered. No complete responses or partial responses (PR) were found, and 12 patients had stable disease for >8 weeks. Median follow-up was 15.0 months. Median time to progression was 5.3 months. Median overall survival could not be calculated, but 86.7% and 66.0% of patients were alive at 6 and 12 months. Marker response included 1 unconfirmed PR and 2 stabilizations for calcitonin, and 1 unconfirmed PR and 4 stabilizations for calcitonin and carcinoembryonic antigen. One patient showed clinical benefit. Quality of life scores generally decreased during the study. Most treatment-related adverse events were mild or moderate. Grade 3 lymphopenia was the only severe hematological toxicity found (2 patients). Severe nonhematological toxicities were grade 3 creatine phosphokinase increase (2 patients, with no myalgia or muscular weakness) and transient grade 3 alanine aminotransferase increase (5 patients).

CONCLUSIONS

Single-agent plitidepsin given as 3-hour i.v. infusions every 2 weeks was generally well tolerated but showed limited clinical activity in patients with unresectable advanced MTC.