Eribulin: rediscovering tubulin as an anticancer target

Eribulin Efficacy on Brain Metastases in Heavily Pretreated Patients with Metastatic Breast Cancer

The onset of brain metastases (BM) is a major turning point during advanced breast cancer (ABC) evolution, with only few treatment options when local therapies have failed. The therapeutic effect of eribulin, a wildly used drug in the treatment of ABC, remains unclear in this setting. Patients and Methods: We performed a retrospective observational study to assess eribulin efficacy in patients with ABC who displayed BM at time of eribulin initiation. We collected data from the medical files of all ABC patients who received eribulin at our institution from 2012 until 2020. Our main endpoint was the central nervous system (CNS) progression-free survival. (CNS-PFS). Other evaluation criteria were extra-cranial progression free survival (PFS) and overall survival (OS). Results: Twenty patients with BM monitoring data available were selected out of the 549 who received eribulin during the inclusion period. Fifteen patients (75%) had BM progressive as the best response, three patients (15%) had disease stabilization for more than 6 months and only one patient had a partial response according to RECIST 1.1 criteria. Median CNS-PFS was 3.39 months (95CI (3.02–3.76)). Cox univariate analysis identified molecular subtype as the only prognostic parameter in our cohort, with patients with hormone-receptor positive tumors less likely to experience CNS progression than those with triple-negative MBC (HR = 0.23 (95CI = 0.07–0.80), p = 0.021). Median extra-cranial PFS was 2.67 months (95CI (2.33–3.01)). Median OS was 7.68 months (95CI (0–17.41)). Conclusion: Eribulin seems to have only a limited impact on BM evolution. Hormone receptors expression may identify a subset of patients with better BM control.

Safety Results and Analysis of Eribulin Efficacy according to Previous Microtubules-Inhibitors Sensitivity in the French Prospective Expanded Access Program for Heavily Pre-treated Metastatic Breast Cancer

Purpose

Eribulin is approved for advanced breast cancers refractory to anthracyclines and taxanes. Efficacy according to sensitivity to previous therapies has been poorly explored.

Materials and Methods

Safety data were collected prospectively and we retrospectively collected efficacy data from the five French centres that participated in the Eribulin E7389-G000-398 expanded access program. Our main objectives were exploration of safety and analysis of eribulin efficacy (progression-free survival [PFS] and overall survival [OS]) according to sensitivity to the last microtubule-inhibiting agent administered.

Results

Median eribulin treatment duration was 3.3 months for the 250 patients included in this prospective single-arm study. Two hundreds and thirty-nine patients (95.6%) experienced an adverse event (AE) related to treatment including 129 (51.6%) with grade ≥ 3 AEs. The most frequently observed toxicities were cytopenias (59.6% of included patients), gastro-intestinal disorders (59.2%), and asthenia (56.4%). The most frequent grade 3-4 AE was neutropenia (37.2% with 4.8% febrile neutropenia). Median PFS and OS were 4.6 and 11.8 months, respectively. Patients classified as responders to the last microtubule-inhibiting therapy had a longer OS (hazard ratio [HR], 0.69; 95% confidence interval [CI], 0.51 to 0.94; p=0.017), and tended to display a better PFS (HR, 0.78; 95% CI, 0.58 to 1.04; p=0.086). OS improvement was still significant in multivariate analysis (adjusted HR, 0.53; 95% CI, 0.35 to 0.79; p=0.002).

Conclusion

This work based on a prospective study suggests that identification of patients likely to be more sensitive to eribulin could be based on their previous response to microtubules inhibitors.

Structure-based drug discovery for combating influenza virus by targeting the PA-PB1 interaction

Influenza virus infections are serious public health concerns throughout the world. The development of compounds with novel mechanisms of action is urgently required due to the emergence of viruses with resistance to the currently-approved anti-influenza viral drugs. We performed in silico screening using a structure-based drug discovery algorithm called Nagasaki University Docking Engine (NUDE), which is optimised for a GPU-based supercomputer (DEstination for Gpu Intensive MAchine; DEGIMA), by targeting influenza viral PA protein. The compounds selected by NUDE were tested for anti-influenza virus activity using a cell-based assay. The most potent compound, designated as PA-49, is a medium-sized quinolinone derivative bearing a tetrazole moiety, and it inhibited the replication of influenza virus A/WSN/33 at a half maximal inhibitory concentration of 0.47 μM. PA-49 has the ability to bind PA and its anti-influenza activity was promising against various influenza strains, including a clinical isolate of A(H1N1)pdm09 and type B viruses. The docking simulation suggested that PA-49 interrupts the PA–PB1 interface where important amino acids are mostly conserved in the virus strains tested, suggesting the strain independent utility. Because our NUDE/DEGIMA system is rapid and efficient, it may help effective drug discovery against the influenza virus and other emerging viruses.

Treatment of advanced, metastatic soft tissue sarcoma: latest evidence and clinical considerations

Soft tissue sarcoma (STS) is a biologically heterogeneous malignancy with over 50 subtypes. Historically, there have been few systemic treatment options for this relatively rare disease. Traditional cytotoxic agents, such as anthracyclines, alkylating agents, and taxanes have limited clinical benefit beyond the first-line setting; across all high-grade STS subtypes, median overall survival remains approximately 12-18 months for advanced metastatic disease. The development of targeted therapies has led to recent US Food and Drug Administration approval of four new treatments for high-grade STS in the advanced metastatic setting. Among these, olaratumab is most notable for its improvement in overall survival for patients with anthracycline-naïve disease. Further progress in STS management will rely on novel trial design, subtype-specific therapies and validation of biomarkers to tailor therapy. Immunotherapy has shown promise as a new, but yet undiscovered frontier in the management of STS.

Examination of the clinical efficacy of eribulin and trastuzumab in HER2-positive recurrent breast cancer

There are limited studies reported that describe the efficacy of eribulin and trastuzumab in the treatment of recurrent breast cancer. The present study examined the therapeutic efficacy of eribulin and trastuzumab in the treatment of recurrent breast cancer. Between October 2011 and August 2013, 5 recurrent breast cancer patients who were treated with eribulin and trastuzumab were included in the study. The cancer stages in the 5 women who received this regimen were stage IIIB in 1 (20%) and stage IV in 4 (80%). The sites of recurrence were the lung in 3 patients, liver in 2, bone in 1, brain in 1, supraclavicular lymph nodes in 1, infraclavicular lymph nodes in 1 and mediastinal lymph nodes in 1. The median number of prior treatment regimens was 5 (range, 5-11). Complete response was achieved in 0 patients, 1 achieved partial response, 3 had stable disease, and 1 had progressive disease. The overall response rate was 20%, and the clinical benefit rate was 80%. Patients also reported grade 3/4 neutropenia (80.0%). However, hematological toxicity was reversible and manageable. The most common grade 3/4 nonhematological toxicities were fatigue (20.0%), peripheral neuropathy (20.0%) and appetite loss (20.0%). No patients withdrew from treatment, and favorable compliance was achieved in the study. The results indicated that eribulin and trastuzumab have the potential to be one of the drugs for treatment of recurrent breast cancer.

Tumour biology, metastatic sites and taxanes sensitivity as determinants of eribulin mesylate efficacy in breast cancer: results from the ERIBEX retrospective, international, multicenter study

BACKGROUND

Our retrospective, international study aimed at evaluating the activity and safety of eribulin mesylate (EM) in pretreated metastatic breast cancer (MBC) in a routine clinical setting.

METHODS

Patients treated with EM for a locally advanced or MBC between March 2011 and January 2014 were included in the study. Clinical and biological assessment of toxicity was performed at each visit. Tumour response was assessed every 3 cycles of treatment. A database was created to collect clinical, pathological and treatment data.

RESULTS

Two hundred and fifty-eight patients were included in the study. Median age was 59 years old. Tumours were Hormone Receptor (HR)-positive (73.3 %) HER2-positive (10.2 %), and triple negative (TN, 22.5 %). 86.4 % of the patients presented with visceral metastases, mainly in the liver (67.4 %). Median previous metastatic chemotherapies number was 4 [1-9]. Previous treatments included anthracyclines and/or taxanes (100 %) and capecitabine (90.7 %). Median number of EM cycles was 5 [1-19]. The relative dose intensity was 0.917. At the time of analysis (median follow-up of 13.9 months), 42.3 % of the patients were still alive. The objective response rate was 25.2 % (95 %CI: 20-31) with a 36.1 % clinical benefit rate (CBR). Median time to progression (TTP) and overall survival were 3.97 (95 %CI: 3.25-4.3) and 11.2 (95 %CI: 9.3-12.1) months, respectively. One- and 2-year survival rates were 45.5 and 8.5 %, respectively. In multivariate analysis, HER2 positivity (HR = 0.29), the presence of lung metastases (HR = 2.49) and primary taxanes resistance (HR = 2.36) were the only three independent CBR predictive factors, while HR positivity (HR = 0.67), the presence of lung metastases (HR = 1.52) and primary taxanes resistance (HR = 1.50) were the only three TTP independent prognostic factors. Treatment was globally well tolerated. Most common grade 3-4 toxicities were neutropenia (20.9 %), peripheral neuropathy (3.9 %), anaemia (1.6 %), liver dysfunction (0.8 %) and thrombocytopenia (0.4 %). Thirteen patients (5 %) developed febrile neutropenia.

CONCLUSION

EM is an effective new option in heavily pretreated MBC, with a favourable efficacy/safety ratio in a clinical practice setting. Our results comfort the use of this new molecule and pledge for the evaluation of EM-trastuzumab combination in this setting. Tumour biology, primary taxanes sensitivity and metastatic sites could represent useful predictive and prognostic factors.

Pharmacodynamics (PD) and pharmacokinetics (PK) of E7389 (eribulin, halichondrin B analog) during a phase I trial in patients with advanced solid tumors: a California Cancer Consortium trial

BACKGROUND

The California Cancer Consortium completed a phase I trial of E7389 (eribulin mesylate), an analog of the marine natural product halichondrin B. This trial was to determine the pharmacodynamics, pharmacokinetics, and MTD of E7389 administered by bolus injection weekly for 3 weeks out of four.

METHODS

This trial included a rapid titration design. Real-time pharmacokinetics were utilized to guide dose escalation. Initially, single-patient cohorts were enrolled with intra- and inter-patient dose doubling. The second phase was a standard 3 + 3 dose escalation schedule. At the MTD, a cohort of patients was enrolled for target validation studies (separate manuscript). The starting dose was 0.125 mg/m(2), and doses were doubled within and between patients in the first phase. Blood and urine sampling for E7389 pharmacokinetics was performed on doses 1 and 3 of cycle 1. Levels were determined using a LC/MS/MS assay.

RESULTS

Forty patients were entered. Thirty-eight were evaluable for toxicity and 35 for response. The rapid escalation ended with a grade 3 elevation of alkaline phosphatase at 0.5 mg/m(2)/week. The second phase ended at 2.0 mg/m(2)/week with dose-limiting toxicities of grades 3 and 4 febrile neutropenia. Other toxicities included hypoglycemia, hypophosphatemia, and fatigue. The MTD was 1.4 mg/m(2)/week. Responses included four partial responses (lung cancer [2], urothelial [1], and melanoma [1]).

CONCLUSIONS

E7389 was well tolerated in this trial with the major toxicity being myelosuppression. PD shows that E7389 induces significant morphologic changes (bundle formation) in the microtubules of peripheral blood mononuclear cells and tumor cells in vivo. The data suggest that lower intra-tumoral levels of β-tubulin III or higher intra-tumoral levels of MAP4 may correlate with response to E7389, while lower intra-tumoral levels of stathmin may be associated with progression. PK data reveal that E7389 exhibits a tri-exponential elimination from the plasma of patients receiving a rapid i.v. infusion. At sub-toxic doses, plasma concentrations of E7389 are maintained well above the levels required for activity in vitro for >72 h.

Practical stereoselective synthesis of eribulin fragment toward building a hybrid macrocyclic toolbox

A practical stereoselective synthesis to obtain the substituted furan ring as the substructure of eribulin is developed. An asymmetric syn-aldol and intramolecular oxy-Michael were two key steps in our approach. The functionalized furan derivatives were then utilized further to build the 14- and 12-membered macrocyclic diversity as trans- and cis-fused (C-29 and C-30) compounds. This is the first report of building a chemical toolbox with macrocyclic small molecules having trans- or cis-fused 14- or 12-membered rings containing the substructure of eribulin and its diastereomer.

Eribulin mesylate in breast cancer

Eribulin mesylate is a synthetic analog of halichondrin B (a polyether macrolide isolated from a marine sponge). It is a nontaxane microtubule dynamics inhibitor with a novel mechanism of action. It is the first drug that has demonstrated an improvement in overall survival as a single agent compared with the physician's choice of currently available treatments in locally advanced or metastatic breast cancer, previously treated with anthracyclines and taxanes. It has shown a good manageable tolerability profile. This drug has been approved by the US FDA and by the EMA for patients with locally advanced or metastatic breast cancer who have received at least two chemotherapeutic regimens for advanced/metastatic disease. Prior therapy should have included an anthracycline and a taxane in either the adjuvant or metastatic setting unless patients were not suitable for these treatments. The aim of this article is to describe the mechanism of action, pharmacokinetics, pharmacodynamics and the most relevant clinical trials in the development of this drug.

Marine invertebrate natural products for anti-inflammatory and chronic diseases

The marine environment represents a relatively available source of functional ingredients that can be applied to various aspects of food processing, storage, and fortification. Moreover, numerous marine invertebrates based compounds have biological activities and also interfere with the pathogenesis of diseases. Isolated compounds from marine invertebrates have been shown to pharmacological activities and are helpful for the invention and discovery of bioactive compounds, primarily for deadly diseases like cancer, acquired immunodeficiency syndrome (AIDS), osteoporosis, and so forth. Extensive research within the last decade has revealed that most chronic illnesses such as cancer, neurological diseases, diabetes, and autoimmune diseases exhibit dysregulation of multiple cell signaling pathways that have been linked to inflammation. On the basis of their bioactive properties, this review focuses on the potential use of marine invertebrate derived compounds on anti-inflammatory and some chronic diseases such as cardiovascular disease, osteoporosis, diabetes, HIV, and cancer.

Eribulin

Eribulin (eribulin mesylate) is a non-taxane microtubule dynamics inhibitor with tubulin-based antimitotic activity and chemotherapeutic effects. Eribulin is used in the treatment of patients with locally advanced or metastatic breast cancer who have previously been treated with at least two chemotherapeutic regimens, including an anthracycline and a taxane. In in vitro studies, eribulin displayed antiproliferative activity against human breast cancer cell lines. Regression and elimination of breast tumours were observed in human tumour xenograft models. In the randomized, open-label, multinational, phase III EMBRACE trial in patients with locally recurrent or metastatic breast cancer, median overall survival was significantly longer in patients who received intravenous eribulin (n = 508) [13.1 months] compared with that in patients who received a treatment of physician's choice (n = 254) [10.6 months; hazard ratio 0.81; 95% CI 0.66, 0.99; p = 0.041]. Prior to enrolment, study participants had received between two and five chemotherapeutic regimens, including an anthracycline and a taxane. Consistent with the findings of earlier phase I and II trials, eribulin was reported to have a manageable tolerability profile in the EMBRACE trial. Peripheral neuropathy (incidence 5%) was the most common adverse event resulting in the discontinuation of eribulin treatment. The most common grade 3/4 adverse events in the eribulin group were neutropenia, leukopenia and asthenia or fatigue.

Eribulin mesylate as a microtubule inhibitor for treatment of patients with metastatic breast cancer

Metastatic breast cancer (MBC) remains an incurable disease, with the goals of care aimed at maximizing the patient's duration and quality of life. Treatment options for MBC have become more efficacious and numerous. In addition to endocrine and chemotherapy agents, a number of targeted agents, including trastuzumab and bevacizumab, have further enhanced the landscape of therapeutic options. Eribulin mesylate (E7389) is a nontaxane microtubule dynamics inhibitor, and a structurally simplified synthetic analog of the natural marine product, halichondrin B, with a novel mechanism of action that has shown antitumor activity in pretreated MBC. Eribulin has shown a manageable tolerability profile in Phase I-II clinical trials and an improvement in overall survival compared with treatment of physician's choice, without relevant toxicities in a recently published Phase III trial. This review will focus on eribulin as a new active agent for MBC and its role in the management of breast disease.

Combining emerging agents in advanced breast cancer

Newer treatments have improved survival for patients with metastatic breast cancer over the last two decades, and a battery of new cytotoxic and targeted therapies is continuing to enhance this trend. This review outlines recent data and ongoing research in this area, by highlighting new developments (regarding approved but relatively new classes of cytotoxic and targeted agents) and also new classes of targeted therapy that are undergoing clinical evaluation. Mechanisms for synergy between agents are discussed where data are available, as is information on the rationale behind the development of agents that inhibit angiogenesis, DNA repair, histone deacetylases, heat shock proteins, or various signaling pathways in tumor proliferation. The abundance of clinical research surrounding anticancer agents, together with ongoing cancer biology research, is expected to further increase the available pool of therapeutic options for metastatic breast cancer. Concomitantly, in the absence of an effective targeted monotherapy, a better understanding of the interplay between biologic and cytotoxic anticancer agents will improve our ability to rationally design combination regimens with better efficacy and tolerability.

Comparison of neuropathy-inducing effects of eribulin mesylate, paclitaxel, and ixabepilone in mice

Chemotherapy-induced neurotoxicity is a significant problem associated with successful treatment of many cancers. Tubulin is a well-established target of antineoplastic therapy; however, tubulin-targeting agents, such as paclitaxel and the newer epothilones, induce significant neurotoxicity. Eribulin mesylate, a novel microtubule-targeting analogue of the marine natural product halichondrin B, has recently shown antineoplastic activity, with relatively low incidence and severity of neuropathy, in metastatic breast cancer patients. The mechanism of chemotherapy-induced neuropathy is not well understood. One of the main underlying reasons is incomplete characterization of pathology of peripheral nerves from treated subjects, either from patients or preclinically from animals. The current study was conducted to directly compare, in mice, the neuropathy-inducing propensity of three drugs: paclitaxel, ixabepilone, and eribulin mesylate. Because these drugs have different potencies and pharmacokinetics, we compared them on the basis of a maximum tolerated dose (MTD). Effects of each drug on caudal and digital nerve conduction velocity, nerve amplitude, and sciatic nerve and dorsal root ganglion morphology at 0.25 × MTD, 0.5 × MTD, 0.75 × MTD, and MTD were compared. Paclitaxel and ixabepilone, at their respective MTDs, produced significant deficits in caudal nerve conduction velocity, caudal amplitude and digital nerve amplitudes, as well as moderate to severe degenerative pathologic changes in dorsal root ganglia and sciatic nerve. In contrast, eribulin mesylate produced no significant deleterious effects on any nerve conduction parameter measured and caused milder, less frequent effects on morphology. Overall, our findings indicate that eribulin mesylate induces less neuropathy in mice than paclitaxel or ixabepilone at equivalent MTD-based doses.

Advances in therapy: eribulin improves survival for metastatic breast cancer

Despite advances in cancer biology, chemotherapy remains the backbone of treatment approaches for many patients with metastatic breast cancer (MBC). Halichondrins, derived from marine sponges, have significant potential as potent antimicrotubule agents. Eribulin, with proven preclinical activity, is a synthetic halichondrin analog with novel actions on tubulin including suppression of microtubule polymerization. Phase I and II studies in MBC identified neutropenia as the dose-limiting toxicity and a maximum tolerated dose of 1.4 mg/m2 on days 1 and 8 of a 21-day cycle. An encouraging response rate of 11.5% in refractory MBC led to the launch of the phase III Eisai Metastatic Breast Cancer Study Assessing Physician's Choice versus Eribulin trial, in which heavily pretreated patients with MBC were randomized 2 : 1 to intravenous eribulin or monotherapy of the investigator's choice. Recently, it was reported that this important study of 762 patients met its primary endpoint of overall survival: eribulin was associated with an improvement in median overall survival from 10.65 months to 13.12 months (hazard ratio 0.8; 95% confidence interval 0.66-0.99) and a response rate of 12.2%. In general, the side effect profile of eribulin seems to be acceptable, as although neutropenia occurred in 45% of the patients, febrile neutropenia was rare and the incidence of neuropathy was low. These findings show that eribulin is potentially a new active agent for MBC, although results of ongoing studies are awaited to confirm the reported benefit. Future studies will investigate the potential role of eribulin in other settings, including for early breast cancer, to ascertain how to optimally incorporate this new agent into current treatment paradigms.

Novel strategies for treating relapsed/refractory urothelial carcinoma

Advanced urothelial cancer is associated with a poor prognosis and there has been no substantial progress over the past three decades since the development of platinum-based multiagent chemotherapy. Clinical trials evaluating novel agents and combinations including chemotherapeutic drugs, as well as targeted inhibitors, are desperately needed. With a better understanding of the complex molecular alterations that drive urothelial tumorigenesis, new targets for novel therapeutics are being defined. This article will describe the current state of advanced urothelial cancer treatment and provide a comprehensive discussion of novel agents in development.

Macromolecular interaction of halichondrin B analogues eribulin (E7389) and ER-076349 with tubulin by analytical ultracentrifugation

Halichondrin B is an antimitotic drug that inhibits microtubule assembly. To understand the molecular details of its interaction with tubulin, we investigated the binding of two halichondrin B analogues, eribulin (previously, ER-086526, E7389) and ER-076349, to tubulin by quantitative analytical ultracentrifugation. Eribulin is currently undergoing phase III clinical trials for cancer; ER-076349 is a closely related analogue with C.35 hydroxyl instead of C.35 primary amine [Towle, M. J., et al. (2001) Cancer Res. 61, 1013]. Below the critical concentration for microtubule assembly and in the presence of GDP, tubulin undergoes weak self-association into short curved oligomers. Eribulin inhibits this oligomer formation 4-6-fold, while ER-076349 slightly stimulates oligomer formation by 2-fold. This is in contrast to vinblastine which strongly stimulates large spiral polymers by 1000-fold under these same conditions. Vinblastine-induced spiral formation is strongly inhibited by both eribulin and ER-076349. Colchicine binding to the intradimer interface has no significant effect on small oligomer formation or the inhibitory activity of eribulin on this process. These results suggest that halichondrin B analogues bind to the interdimer interface or to the beta-subunit alone, disrupt polymer stability, and compete with vinblastine-induced spiral formation. Stathmin is known to form a tight 1:2 complex with tubulin. Eribulin strongly inhibits formation of the 1:2 stathmin-tubulin complex (>3.3 kcal/mol), while ER-076349 weakens formation of the 1:2 complex by approximately 1.9 kcal/mol. These results suggest that eribulin is a global inhibitor of tubulin polymer formation, disrupting tubulin-tubulin contacts at the interdimer interface. ER-076349 also perturbs tubulin-tubulin contacts, but in a more polymer specific manner, reflecting adaptability of the interdimer interface to drug and polymer polymorphism. These results suggest halichondrin B analogues exhibit unique tubulin-based activities that may underlie the clinical utility of these compounds.