Phase II study of weekly plitidepsin as second-line therapy for small cell lung cancer

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.

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.

Phase I dose-escalation study of plitidepsin in combination with sorafenib or gemcitabine in patients with refractory solid tumors or lymphomas

This phase I trial evaluated the combination of the marine-derived cyclodepsipeptide plitidepsin (trade name Aplidin) with sorafenib or gemcitabine in advanced cancer and lymphoma patients. The study included two treatment arms: a sorafenib/plitidepsin (S/P) and a gemcitabine/plitidepsin (G/P) arm. In the S/P arm, patients were treated orally with sorafenib continuous dosing at two dose levels (DL1: 200 mg twice daily and DL2: 400 mg twice daily) combined with plitidepsin (1.8 mg/m, day 1, day 8, day 15, and, q4wk, intravenously). In the G/P arm, patients with solid tumors or lymphoma were treated at four different DLs with a combination of gemcitabine (DL1: 750 mg/m, DL2-DL4: 1000 mg/m) and plitidepsin (DL1-DL2: 1.8 mg/m; DL3: 2.4 mg/m; DL4: 3 mg/m). Both agents were administered intravenously on day 1, day 8, day 15, and, q4wk. Forty-four patients were evaluable for safety and toxicity. The safety of the combination of plitidepsin with sorafenib or gemcitabine was manageable. Most adverse events (AEs) were mild; no grade 4 treatment-related AEs were reported in any of the groups (except for one grade 4 thrombocytopenia in the gemcitabine arm). The most frequently reported study drug-related (or of unknown relationship) AEs were palmar-plantar erythrodysesthesia, erythema, nausea, vomiting, and fatigue in the S/P arm and nausea, fatigue, and vomiting in the G/P arm. In the S/P arm, one dose-limiting toxicity occurred in two out of six patients treated at the maximum dose tested (DL2): palmar-plantar erythrodysesthesia and grade 2 aspartate aminotransferase/alanine aminotransferase increase that resulted in omission of days 8 and 15 plitidepsin infusions. In the G/P arm, one dose-limiting toxicity occurred in two out of six patients at DL4: grade 2 alanine aminotransferase increase resulted in omission of days 8 and 15 plitidepsin infusions and grade 4 thrombocytopenia. The recommended dose for the combination of plitidepsin with sorafenib was not defined because of a sponsor decision (no expansion cohort to confirm) and for plitidepsin with gemcitabine, it was 2.4 mg/m plitidepsin with 1000 mg/m gemcitabine. In the S/P group, objective disease responses were not observed; however, disease stabilization (≥3months) was observed in four patients. In the gemcitabine group, two lymphoma patients showed an objective response (partial response and complete response) and nine patients showed disease stabilization (≥3months). Combining plitidepsin with gemcitabine and sorafenib is feasible for advanced cancer patients; some objective responses were observed in heavily pretreated lymphoma patients.

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.

Marine Antibody-Drug Conjugates: Design Strategies and Research Progress

Antibody-drug conjugates (ADCs), constructed with monoclonal antibodies (mAbs), linkers, and natural cytotoxins, are innovative drugs developed for oncotherapy. Owing to the distinctive advantages of both chemotherapy drugs and antibody drugs, ADCs have obtained enormous success during the past several years. The development of highly specific antibodies, novel marine toxins' applications, and innovative linker technologies all accelerate the rapid R&D of ADCs. Meanwhile, some challenges remain to be solved for future ADCs. For instance, varieties of site-specific conjugation have been proposed for solving the inhomogeneity of DARs (Drug Antibody Ratios). In this review, the usages of various natural toxins, especially marine cytotoxins, and the development strategies for ADCs in the past decade are summarized. Representative ADCs with marine cytotoxins in the pipeline are introduced and characterized with their new features, while perspective comments for future ADCs are proposed.

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.

Evaluation of plitidepsin in patients with primary myelofibrosis and post polycythemia vera/essential thrombocythemia myelofibrosis: results of preclinical studies and a phase II clinical trial

Previous data established that plitidepsin, a cyclic depsipeptide, exerted activity in a mouse model of myelofibrosis (MF). New preclinical experiments reported herein found that low nanomolar plitidepsin concentrations potently inhibited the proliferation of JAK2V617F-mutated cell lines and reduced colony formation by CD34+ cells of individuals with MF, at least in part through modulation of p27 levels. Cells of MF patients had significantly reduced p27 content, that were modestly increased upon plitidepsin exposure. On these premise, an exploratory phase II trial evaluated plitidepsin 5 mg/m(2) 3-h intravenous infusion administered on days 1 and 15 every 4 weeks (q4wk). Response rate (RR) according to the International Working Group for Myelofibrosis Research and Treatment consensus criteria was 9.1% (95% CI, 0.2-41.3%) in 11 evaluable patients during the first trial stage. The single responder achieved a red cell transfusion independence and stable disease was reported in nine additional patients (81.8%). Eight patients underwent a short-lasting improvement of splenomegaly. In conclusion, plitidepsin 5 mg/m(2) 3-h infusion q4wk was well tolerated but had a modest activity in patients with primary, post-polycythaemia vera or post-essential thrombocythaemia MF. Therefore, this trial was prematurely terminated and we concluded that further clinical trials with plitidepsin as single agent in MF are not warranted.

Relapsed small cell lung cancer: treatment options and latest developments

According to recent analyses, there was a modest yet significant improvement in median survival time and 5-year survival rate of limited stage small cell lung cancer (SCLC) in North America, Europe, Japan and other countries over the last 30 years. The median survival time of limited stage SCLC is 15-20 months and 5-year survival rate is 15% or less. In terms of extensive stage SCLC, a median survival time of 9.4-12.8 months and 2-year survival of 5.2-19.5% are still disappointing. Despite being highly sensitive to first-line chemotherapy and radiotherapy treatments, most patients with SCLC experience relapse within 2 years and die from systemic metastasis. While several clinical trials of cytotoxic chemotherapies and molecular targeting agents have been investigated in the treatment of relapsed SCLC, none showed a significant clinical activity to be able to exceed topotecan as second-line chemotherapy. There are problematic issues to address for relapsed SCLC, such as standardizing the treatment for third-line chemotherapy. Topotecan alone was the first approved therapy for second-line treatment for relapsed SCLC. Amrubicin is a promising drug and a variety of trials evaluating its efficacy have been carried out. Amrubicin has shown superiority to topotecan in a Japanese population, but was not superior in a study of western patients. There are some controversial issues for relapsed SCLC, such as treatment for older patients, third-line chemotherapy and efficacy of molecular targeting therapy. This article reviews current standard treatment, recent clinical trials and other topics on relapsed SCLC.

Ectopic activation of germline and placental genes identifies aggressive metastasis-prone lung cancers

Activation of normally silent tissue-specific genes and the resulting cell "identity crisis" are the unexplored consequences of malignant epigenetic reprogramming. We designed a strategy for investigating this reprogramming, which consisted of identifying a large number of tissue-restricted genes that are epigenetically silenced in normal somatic cells and then detecting their expression in cancer. This approach led to the demonstration that large-scale "off-context" gene activations systematically occur in a variety of cancer types. In our series of 293 lung tumors, we identified an ectopic gene expression signature associated with a subset of highly aggressive tumors, which predicted poor prognosis independently of the TNM (tumor size, node positivity, and metastasis) stage or histological subtype. The ability to isolate these tumors allowed us to reveal their common molecular features characterized by the acquisition of embryonic stem cell/germ cell gene expression profiles and the down-regulation of immune response genes. The methodical recognition of ectopic gene activations in cancer cells could serve as a basis for gene signature-guided tumor stratification, as well as for the discovery of oncogenic mechanisms, and expand the understanding of the biology of very aggressive tumors.

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.

Marine-derived angiogenesis inhibitors for cancer therapy

Angiogenesis inhibitors have been successfully used for cancer therapy in the clinic. Many marine-derived natural products and their analogues have been reported to show antiangiogenic activities. Compared with the drugs in the clinic, these agents display interesting characteristics, including diverse sources, unique chemical structures, special modes of action, and distinct activity and toxicity profiles. This review will first provide an overview of the current marine-derived angiogenesis inhibitors based on their primary targets and/or mechanisms of action. Then, the marine-derived antiangiogenic protein kinase inhibitors will be focused on. And finally, the clinical trials of the marine-derived antiangiogenic agents will be discussed, with special emphasis on their application potentials, problems and possible coping strategies in their future development as anticancer drugs.

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.

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.

[Molecular targeted therapies in small-cell lung cancer]

Small-cell lung cancers (SCLC) are aggressive malignancies, however, characterized by high primary chemosensitivity. Unfortunately, for the vast majority of patients, relapse is the rule with emergence of secondary resistance mechanisms. In the era of molecular targeted therapies, characterization of a number of molecular abnormalities has encouraged implementation of several clinical trials. This literature review summarizes the various pharmacological approaches used in SCLC to improve survival in localized and extensive forms of the disease. Initial trials with molecular targeted therapies have not been able to improve clinical outcome compared to the standard etoposide-cisplatin chemotherapy regimen in extensive forms. However, new targets continue to be identified and many treatments are currently being assessed, including blockade of angiogenesis, signal transduction, cell cycle or induction of apoptosis.

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.