Microtubule Dynamics Inhibitor Research Articles

Crocin, a carotenoid, suppresses spindle microtubule dynamics and activates the mitotic checkpoint by binding to tubulin

Crocin, a constituent of the saffron spice, exhibits promising antitumor activity in animal models and also inhibits the proliferation of several types of cancer cells in culture. Recently, we have shown that crocin binds to purified tubulin at the vinblastine site, depolymerizes microtubules and induces a mitotic block in cultured cells. Here, we extend our previous suggestion and explore the cellular effects of crocin to further understand its mechanism of action. In a kinetic study, we observed that the crocin-induced depolymerization of microtubules preceded both DNA damage and reactive oxygen species generation indicating that depolymerizing microtubules is the primary action of crocin. Crocin also inhibited the growth of cold-depolymerized microtubules in HeLa cells indicating that it can inhibit microtubule dynamics. Using fluorescence recovery after photobleaching, crocin was found to suppress the spindle microtubule dynamics in live HeLa cells. Further, crocin treatment resulted in activation of spindle assembly checkpoint proteins, BubR1 and Mad2. Similar to other microtubule-targeting agents, crocin also perturbed the localization of end-binding protein EB1 from the growing microtubule ends and enhanced the acetylation of remaining microtubules. Further, crocin was found to bind to purified tubulin with a dissociation constant of 12 ± 1.5 μM. The results suggested that crocin exerted its antiproliferative effect primarily by inhibiting the assembly and dynamics of microtubules. Importantly, the combination of crocin with known anticancer agents like combretastatin A-4, cisplatin, doxorubicin or sorafenib, exerted a strong synergistic cytotoxic effect in HeLa cells indicating that crocin may enhance the effectiveness of other anticancer agents.

Biomimetic Shells Endow Sub-50 nm Nanoparticles with Ultrahigh Paclitaxel Payloads for Specific and Robust Chemotherapy.

Poor loading capacity and nonspecific tumor accumulation of current drug delivery system remain the critical challenges that prevent nanomedicine from maximizing therapeutic efficacy in cancer treatment. Herein, poly(ester amide) polymers composed of cationic and hydrophobic segments were formulated with a paclitaxel/human serum albumin (PTX/HSA) complex, as well as free PTX, to construct a core-shell nanoparticle (NP) platform with the interior simultaneously reserving PTX and PTX/HSA complex, while the exterior absorbing the PTX/HSA complex. Following systematic screening, the optimized NPs, namely, APP1i@e NPs, exhibited small particle size (43.95 nm), maximal PTX loading (42.23%), excellent dynamic stability (at least 1 week), and acid-triggered release. In vitro results showed that after being trafficked through caveolae-mediated endocytosis, APP1i@e NPs successfully escaped from endo-/lysosomes and then rapidly released cargos in the acidic cytosol, which continued to enhance cytotoxicity by mitochondrial control of apoptosis and suppression of microtubule dynamics. Longer circulation time and superior targeting efficiency post-intravenous injection confirmed that surface PEGylation imparted APP1i@e NPs with the ability to control their pharmacokinetics and biodistribution. The biomimetic shell design with HSA, which enlarged PTX stock and improved biosafety, made APP1i@e NPs more suitable for in vivo applications. Furthermore, in vivo safety and efficacy demonstrated that APP1i@e NPs effectively inhibited the growth of ovarian xenograft tumors, whereas significantly avoiding toxic issues associated with PTX. APP1i@e NPs with surface PEG coating and biomimetic HSA design, therefore, may provide a remarkable improvement in the therapeutic index of taxanes used in the clinic.

Low-dose eribulin mesylate exerts antitumor effects in gastric cancer by inhibiting fibrosis via the suppression of epithelial–mesenchymal transition and acts synergistically with 5-fluorouracil

BackgroundCharacterized by aggressive proliferation, extensive stromal fibrosis, and resulting drug resistance, peritoneal dissemination in gastric cancer remains associated with poor prognosis. Interaction between cancer and stromal cells accelerates tumor progression via epithelial–mesenchymal transition (EMT), which is one of the major causes of tissue fibrosis, and human peritoneal mesothelial cells (HPMCs) play important roles as cancer stroma in peritoneal dissemination. Transforming growth factor-β (TGF-β) has a pivotal function in the progression of EMT, and Smad proteins play an important role in the TGF-β signaling pathway. Eribulin mesylate (eribulin), a nontaxane microtubule dynamics inhibitor used for the treatment of advanced breast cancer, inhibits EMT changes in triple-negative breast cancer cells. We examined its ability to inhibit tumor progression and EMT changes resulting from the interaction between gastric cancer cells and HPMCs and to act synergistically with 5-fluorouracil (5-FU), a key drug for gastric cancer.Materials and methodsProliferation of gastric cancer cells and HPMCs isolated from healthy omentum was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Following gastric cancer cell/HPMC coculture, EMT markers were detected by immunofluorescence, immunohistochemistry, and Western blotting; invasion assays were performed; and TGF-β and Smad phosphorylation were assessed by Western blotting and enzyme-linked immunosorbent assay. A mouse fibrotic tumor xenograft model was established using gastric cancer cell/HPMC cocultures. The effect of eribulin and/or 5-FU was tested in each case.ResultsEribulin significantly suppressed gastric cancer cell proliferation and EMT changes in MKN-45 gastric cancer cells and HPMCs induced by their interaction in vitro. Eribulin inhibited EMT at much lower concentrations (≥0.5 nM for MKN-45 and ≥0.1 nM for HPMCs) than its half maximal inhibitory concentrations (2.2 nM for MKN-45 and 8.1 nM for HPMCs), and this resulted, at least partly, from the downregulation of TGF-β/Smad signaling. Eribulin administration of ≥0.1 mg/kg suppressed tumor progression (0.1 mg/kg, p=0.02), and fibrosis was inhibited by lower dose (0.05 mg/kg, p=0.008) in the xenograft model. Furthermore, 0.05 mg/kg administration with 5-FU brought about synergistic antitumor effects (p=0.006).ConclusionLow-dose eribulin combined with 5-FU might be a promising therapy for peritoneal dissemination in gastric cancer.

Abstract 2924: Preclinical analysis of synergistic antitumor effect of eribulin and HDAC inhibitor for triple-negative breast cancer cells

Abstract Eribulin (ERI), an inhibitor of microtubule dynamics, is a key drug for metastatic breast cancer. While HDAC inhibitors have been shown to presents antitumor effect for various malignancies. Among HDAC family, HDAC6 is known as a deacetylase of tubulin. To develop a novel therapeutic strategy for triple negative breast cancer (TNBC), we tested the combinational effect of ERI and HDAC inhibitor for TNBC cells in vitro. Two TNBC cell lines (MDA-MB-231, Hs578T) and their ERI-resistant cells (MDA-MB-231/E, Hs578T/E) established in our laboratory were used in the study. Vorinostat (VOR), a pan-HDAC inhibitor, and ricolinostat (RICO), a selective HDAC6 inhibitor were used. The sensitivity to VOR or RICO was not different between the parental and the ERI-resistant cells. In the protein expression analysis, HDAC6 expression was not altered between parental and ERI-resistant cells. Prior treatment with VOR or RICO increased the expression of acetylatedα-tubulin in both parental and ERI-resistant TNBC cell lines. When low concentration of VOR (0.5 μM) or RICO (0.5 μM) was added simultaneously with ERI, the sensitivity to ERI was enhanced significantly in both parental MDA-MB-231 and Hs578T cell lines. Furthermore, when both parental cell lines were treated with VOR (5 μM) or RICO (5 μM) for 48 hrs prior to addition of ERI, the sensitivity to ERI was significantly enhanced. The enhancement of sensitivity to ERI both by the simultaneous addition with low concentration of VOR or RICO and by the prior treatment with VOR or RICO was observed in the ERI-resistant cells as well. Moreover, inhibition of HDAC6 by small interfering RNA partially enhanced the sensitivity to ERI in the both parental cell lines. Our study demonstrated the possibility that the combination of ERI with HDAC inhibitor might enhance the antitumor effect of ERI and overcome ERI resistance through acetylation of α-tubulin by HDAC6 inhibition in TNBC cells. Citation Format: Takaaki Oba, Hiroto Izumi, Ken-ichi Ito. Preclinical analysis of synergistic antitumor effect of eribulin and HDAC inhibitor for triple-negative breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2924.

Microtubule-Targeting Agents: Strategies To Hijack the Cytoskeleton.

Microtubule-targeting agents (MTAs) such as paclitaxel and the vinca alkaloids are among the most important medical weapons available to combat cancer. MTAs interfere with intracellular transport, inhibit eukaryotic cell proliferation, and promote cell death by suppressing microtubule dynamics. Recent advances in the structural analysis of MTAs have enabled the extensive characterization of their interactions with microtubules and their building block tubulin. We review here our current knowledge on the molecular mechanisms used by MTAs to hijack the microtubule cytoskeleton, and discuss dual inhibitors that target both kinases and microtubules. We further formulate some outstanding questions related to MTA structural biology and present possible routes for future investigations of this fascinating class of antimitotic agents.

Estradiol dimer inhibits tubulin polymerization and microtubule dynamics

Microtubule dynamics is one of the major targets for new chemotherapeutic agents. This communication presents the synthesis and biological profiling of steroidal dimers based on estradiol, testosterone and pregnenolone bridged by 2,6-bis(azidomethyl)pyridine between D rings. The biological profiling revealed unique properties of the estradiol dimer including cytotoxic activities on a panel of 11 human cell lines, ability to arrest in the G2/M phase of the cell cycle accompanied with the attenuation of DNA/RNA synthesis. Thorough investigation precluded a genomic mechanism of action and revealed that the estradiol dimer acts at the cytoskeletal level by inhibiting tubulin polymerization. Further studies showed that estradiol dimer, but none of the other structurally related dimeric steroids, inhibited assembly of purified tubulin (IC50, 3.6 μM). The estradiol dimer was more potent than 2-methoxyestradiol, an endogenous metabolite of 17β-estradiol and well-studied microtubule polymerization inhibitor with antitumor effects that was evaluated in clinical trials. Further, it was equipotent to nocodazole (IC50, 1.5 μM), an antimitotic small molecule of natural origin. Both estradiol dimer and nocodazole completely and reversibly depolymerized microtubules in interphase U2OS cells at 2.5 μM concentration. At lower concentrations (50 nM), estradiol dimer decreased the microtubule dynamics and growth life-time and produced comparable effect to nocodazole on the microtubule dynamicity. In silico modeling predicted that estradiol dimer binds to the colchicine-binding site in the tubulin dimer. Finally, dimerization of the steroids abolished their ability to induce transactivation by estrogen receptor α and androgen receptors. Although other steroids were reported to interact with microtubules, the estradiol dimer represents a new structural type of steroid inhibitor of tubulin polymerization and microtubule dynamics, bearing antimitotic and cytotoxic activity in cancer cell lines.

Long-term responders with metastatic breast cancer (MBC) receiving eribulin: Real life experience.

e13065Background: Recently developed microtubule dynamics inhibitor eribulin mesylate (eribulin) differs from taxanes and vinca alkaloids by another mechanism of action. Here, we describe eribulin-...

Plocabulin, a novel tubulin-binding agent, inhibits angiogenesis by modulation of microtubule dynamics in endothelial cells

BackgroundVascular supply of tumors is one of the main targets for cancer therapy. Here, we investigated if plocabulin (PM060184), a novel marine-derived microtubule-binding agent, presents antiangiogenic and vascular-disrupting activities.MethodsThe effects of plocabulin on microtubule network and dynamics were studied on HUVEC endothelial cells. We have also studied its effects on capillary tube structures formation or destabilization in three-dimensional collagen matrices. In vivo experiments were performed on different tumor cell lines.ResultsIn vitro studies show that, at picomolar concentrations, plocabulin inhibits microtubule dynamics in endothelial cells. This subsequently disturbs the microtubule network inducing changes in endothelial cell morphology and causing the collapse of angiogenic vessels, or the suppression of the angiogenic process by inhibiting the migration and invasion abilities of endothelial cells. This rapid collapse of the endothelial tubular network in vitro occurs in a concentration-dependent manner and is observed at concentrations lower than that affecting cell survival. The in vitro findings were confirmed in tumor xenografts where plocabulin treatment induced a large reduction in vascular volume and induction of extensive necrosis in tumors, consistent with antivascular effects.ConclusionsAltogether, these data suggest that an antivascular mechanism is contributing to the antitumor activities of plocabulin.

Unusual zinc-binding mode of HDAC6-selective hydroxamate inhibitors

Histone deacetylases (HDACs) regulate myriad cellular processes by catalyzing the hydrolysis of acetyl-l-lysine residues in histone and nonhistone proteins. The Zn2+-dependent class IIb enzyme HDAC6 regulates microtubule function by deacetylating α-tubulin, which suppresses microtubule dynamics and leads to cell cycle arrest and apoptosis. Accordingly, HDAC6 is a target for the development of selective inhibitors that might be useful in new therapeutic approaches for the treatment of cancer, neurodegenerative diseases, and other disorders. Here, we present high-resolution structures of catalytic domain 2 from Danio rerio HDAC6 (henceforth simply "HDAC6") complexed with compounds that selectively inhibit HDAC6 while maintaining nanomolar inhibitory potency: N-hydroxy-4-[(N(2-hydroxyethyl)-2-phenylacetamido)methyl)-benzamide)] (HPB), ACY-1215 (Ricolinostat), and ACY-1083. These structures reveal that an unusual monodentate Zn2+ coordination mode is exploited by sterically bulky HDAC6-selective phenylhydroxamate inhibitors. We additionally report the ultrahigh-resolution structure of the HDAC6-trichostatin A complex, which reveals two Zn2+-binding conformers for the inhibitor: a major conformer (70%) with canonical bidentate hydroxamate-Zn2+ coordination geometry and a minor conformer (30%) with monodentate hydroxamate-Zn2+ coordination geometry, reflecting a free energy difference of only 0.5 kcal/mol. The minor conformer is not visible in lower resolution structure determinations. Structural comparisons of HDAC6-inhibitor complexes with class I HDACs suggest active site features that contribute to the isozyme selectivity observed in biochemical assays.

Toxoplasma gondii reorganizes the host cell architecture during spontaneous cyst formation in vitro.

Toxoplasma gondii is an intracellular protozoan parasite that causes toxoplasmosis, a prevalent infection related to abortion, ocular diseases and encephalitis in immuno-compromised individuals. In the untreatable (and life-long) chronic stage of toxoplasmosis, parasitophorous vacuoles (PVs, containing T. gondii tachyzoites) transform into tissue cysts, containing slow-dividing bradyzoite forms. While acute-stage infection with tachyzoites involves global rearrangement of the host cell cytoplasm, focused on favouring tachyzoite replication, the cytoplasmic architecture of cells infected with cysts had not been described. Here, we characterized (by fluorescence and electron microscopy) the redistribution of host cell structures around T. gondii cysts, using a T. gondii strain (EGS) with high rates of spontaneous cystogenesis in vitro. Microtubules and intermediate filaments (but not actin microfilaments) formed a 'cage' around the cyst, and treatment with taxol (to inhibit microtubule dynamics) favoured cystogenesis. Mitochondria, which appeared adhered to the PV membrane, were less closely associated with the cyst wall. Endoplasmic reticulum (ER) profiles were intimately associated with folds in the cyst wall membrane. However, the Golgi complex was not preferentially localized relative to the cyst, and treatment with tunicamycin or brefeldin A (to disrupt Golgi or ER function, respectively) had no significant effect on cystogenesis. Lysosomes accumulated around cysts, while early and late endosomes were more evenly distributed in the cytoplasm. The endocytosis tracer HRP (but not BSA or transferrin) reached bradyzoites after uptake by infected host cells. These results suggest that T. gondii cysts reorganize the host cell cytoplasm, which may fulfil specific requirements of the chronic stage of infection.

Phase II, multicentre, randomised trial of eribulin plus gemcitabine versus paclitaxel plus gemcitabine as first-line chemotherapy in patients with HER2-negative metastatic breast cancer

BackgroundPaclitaxel plus gemcitabine (PG) combination chemotherapy is a preferred chemotherapeutic regimen for patients with metastatic breast cancer (MBC). Eribulin mesylate is a halichondrin non-taxane inhibitor of microtubule dynamics. A recent pooled analysis with eribulin showed improved overall survival (OS) in various MBC patient subgroups pretreated with anthracycline and taxane. Furthermore, eribulin may have less neurotoxicity than paclitaxel. Patients and methodsThis study was a prospective randomised phase II, open-label, two-arm, multicentre study comparing eribulin plus gemcitabine (EG) with PG chemotherapy as a first-line treatment for patients with human epidermal growth factor receptor 2-negative MBC. We hypothesised that EG chemotherapy would not be inferior to PG chemotherapy. The primary end-point was progression-free survival (PFS), which was estimated to be 70% at 6 months for each arm. The secondary end-points were as follows: OS, neuropathic scale, toxicity and clinical benefit rate. ResultsA total of 118 patients (median age: 50, 24–66) were enrolled between March 2015 and March 2016 and were randomly assigned to PG (n = 59) or EG (n = 59) chemotherapy. The mean number of metastatic sites was 3 (range 1–8). The 6-month PFS rates for both arms were 72% for EG and 73% for PG (P = 0.457). There was no significant difference in OS between the two groups (not reached versus 21.2 months, P = 0.2234). The median number of chemotherapy cycles for both groups was 10 for EG and 8 for PG (range 2–32). Clinical benefit rates were 44% for EG and 49% for PG. Major toxicities were neutropenia and neurotoxicity. Grade II or above neurotoxicity was more common with PG than with EG (13.6% for EG versus 45.8% for PG, P < 0.0001). ConclusionEG chemotherapy had similar clinical benefits to PG chemotherapy in terms of PFS but less neurotoxicity. Trial registrationKCSG BR13-11; ClinicalTrials.gov, NCT02263495.

97P - Phase II trial of eribulin and S-1 combination therapy for advanced or recurrent breast cancer

Background: Eribulin is a non-taxane microtubule dynamics inhibitor that has been proven to prolong overall survival in patients with breast cancer. S-1, an oral anticancer drug, has demonstrated non-inferiority in overall survival (OS) to taxane as first-line chemotherapy for metastatic breast cancer (MBC). We previouly reported phase I trial results for the combination of these drugs with an overall response rate of 41.7% and median progression free survival (PFS) of 7.6 months. George W et.al (J Clin Oncol 2003) suggested that estrogen receptor negativity, the presence of three or more sites of disease, a short disease-free interval (1 to 24 months), and prior systemic therapy all predicted for impaired overall survival in their multivariate analysis. Considering these factors, we conducted a multicenter phase II study of this combination to further evaluate its safety and efficacy. Methods: Recurrent or advanced breast cancer patients previously treated with anthracycline or taxanes were enrolled from September 2014 to May 2016. Patients received Eribulin 1.4 mg/m2 day1 and day8 intravenously and S-1 50 mg/m2 from day1 to day14 orally. Primary objective was to investigate safety and efficacy. Secondary objectives were to evaluate PFS, OS and clinical benefit rate (CBR) using Response Criteria in Solid Tumors (RECIST). Results: Thirty-two patients were enrolled this trial and 30 patients were evaluable. Objective response rate was 36.7%. There were 3 [10%] complete responses, 8 [26.7%] partial responses and 11 [36.7%] stable diseases. This combination therapy had a manageable safety profiles consistent with the known adverse effects of both drugs. The most common grade3-4 adverse events were neutropenia (22 [73.3%] of 32 patients), leukopenia (13 [43.3%] of 32 patients), febrile neutropenia (3 [9.4%] of 32 patients) and peripheral neuropathy (4 [12.5%] of 32 patients). CBR was 46.7%. The median overall survival and the median PFS was not reached. Conclusions: We showed tolerability and clinical activity in this combination therapy in a subset of patients with poor prognosis. Eribulin in combination with S-1 may represent a promising treatment option for advanced or recurrent breast cancer patients. Legal entity responsible for the study: Eisai Funding: Eisai Disclosure: All authors have declared no conflicts of interest.

A randomized, open-label, multicenter, phase 3 study to compare the efficacy and safety of eribulin to treatment of physician’s choice in patients with advanced non-small cell lung cancer

BackgroundEribulin is a microtubule dynamics inhibitor with a novel mechanism of action. This phase 3 study aimed to compare overall survival (OS) in patients with heavily pretreated non-small cell lung cancer (NSCLC) receiving eribulin to treatment of physician’s choice (TPC).Patients and methodsPatients with advanced NSCLC who had received ≥2 prior therapies, including platinum-based doublet and epidermal growth factor receptor tyrosine kinase inhibitor, were randomly assigned to receive eribulin or TPC (gemcitabine, pemetrexed, vinorelbine, docetaxel). The primary endpoint was OS. Secondary endpoints were progression-free survival and objective response rate.ResultsFive hundred and forty patients were randomized to either eribulin (n = 270) or TPC (n = 270). Median OS for eribulin and TPC was the same: 9.5 months [hazard ratio (HR): 1.16; 95% confidence interval: 0.95–1.41; P = 0.13]. Progression-free survival for eribulin and TPC was 3.0 and 2.8 months, respectively (HR: 1.09; 95% confidence interval: 0.90–1.32; P = 0.39). The objective response rate was 12% for eribulin and 15% for TPC. Clinical benefit rate (eribulin, 57%; TPC, 55%) and disease control rate (eribulin, 63%; TPC, 58%) were similar between treatment arms. The most common adverse event was neutropenia, which occurred in 57% of eribulin patients and 49% of TPC patients at all grades. Other non-hematologic side-effects were manageable and similar in both groups except for peripheral sensory neuropathy (all grades; eribulin, 16%; TPC, 9%).ConclusionThis phase 3 study did not demonstrate superiority of eribulin over TPC with regard to overall survival. However, eribulin does show activity in the third-line setting for NSCLC.Trial registration ID www.ClinicalTrials.gov; NCT01454934.

Identification of predictive markers of the therapeutic effect of eribulin chemotherapy for locally advanced or metastatic breast cancer

BackgroundThe recently developed reagent, eribulin mesylate (eribulin), is a microtubule dynamics inhibitor with a mechanism of action that differs from those of taxanes and vinca alkaloids. This drug is considered to be a promising chemotherapeutic agent for the treatment of locally advanced or metastatic breast cancer (MBC). In this study, we investigated if variables such as tumor expression of β-tubulin class III, glutathione S-transferase pi (GSTP) 1 or transducin-like enhancer of split (TLE) 3 might act as predictive factors on the therapeutic effect of eribulin chemotherapy.MethodsThe subjects included 52 patients with MBC who underwent chemotherapy with eribulin. The expression levels of Estrogen receptor (ER), progesterone receptor (PgR), human epidermal growth factor receptor (HER) 2, Ki67, β-tubulin class III, GSTP-1 and TLE-3 were evaluated using immunostaining employing needle biopsy specimens.ResultsPatients with TLE3-negative tumors displayed significantly poorer outcomes regarding progression-free survival than patients with TLE3-positive tumors when prognosis within the group of patients with triple-negative breast cancer (TNBC) lesions was analyzed (p = 0.011, log-rank). In contrast, no such difference in prognosis was found in a comparison of TLE-3 positive/negative patients in the group of all patients (p = 0.433, log-rank) or of patients with non-TNBC lesions (p = 0.659, log-rank). Based on a univariate analysis of 22 TNBC cases, a better progression-free survival correlated significantly with a positive TLE3 expression in the tumor (p = 0.025). A multivariate logistic regression analysis including 22 patients with TNBC also showed that a positive TLE3 expression significantly correlated with a better progression-free survival (p = 0.037).ConclusionsOur findings suggest that TLE3 is a useful marker for predicting the therapeutic effect of eribulin chemotherapy for TNBC.

Dynein efficiently navigates the dendritic cytoskeleton to drive the retrograde trafficking of BDNF/TrkB signaling endosomes.

The efficient transport of cargoes within axons and dendrites is critical for neuronal function. Although we have a basic understanding of axonal transport, much less is known about transport in dendrites. We used an optogenetic approach to recruit motor proteins to cargo in real time within axons or dendrites in hippocampal neurons. Kinesin-1, a robust axonal motor, moves cargo less efficiently in dendrites. In contrast, cytoplasmic dynein efficiently navigates both axons and dendrites; in both compartments, dynamic microtubule plus ends enhance dynein-dependent transport. To test the predictions of the optogenetic assay, we examined the contribution of dynein to the motility of an endogenous dendritic cargo and found that dynein inhibition eliminates the retrograde bias of BDNF/TrkB trafficking. However, inhibition of microtubule dynamics has no effect on BDNF/TrkB motility, suggesting that dendritic kinesin motors may cooperate with dynein to drive the transport of signaling endosomes into the soma. Collectively our data highlight compartment-specific differences in kinesin activity that likely reflect specialized tuning for localized cytoskeletal determinants, whereas dynein activity is less compartment specific but is more responsive to changes in microtubule dynamics.

Abstract 5927: Eribulin modulates tumor microenvironment through vascular remodeling for antitumor effect in multiple mouse xenograft models

Abstract Eribulin mesilate (Eribulin), a first-in-class halichondrin B-based microtubule dynamics inhibitor, has been reported to remodel tumor vasculature (i.e., improvement of tumor vessels and perfusion) in human breast cancer xenograft models; however, the role of this vascular remodeling in anti-tumor effects is not fully understood. Here, we investigated the effects of eribulin-induced vascular remodeling on anti-tumor activities in multiple human cancer xenograft models. Microvessel densities (MVDs) were evaluated by immunohistochemistry (CD31 staining), and anti-tumor effects were examined in 10 human cancer xenograft models treated with eribulin. Eribulin treatment significantly increased MVDs compared to the corresponding control groups in 7 out of 10 models with a correlation between enhanced MVD levels and anti-tumor effects (R2=0.55). Because of observed increases in MVDs, we next utilized 111In-labeled PEGylated liposomes to examine if eribulin treatment would result in increased tumoral accumulation levels of such liposomes, and indeed, we found that eribulin, unlike vinorelbine another tubulin inhibitor, enhanced them. Since eribulin treatment increased accumulation of 111In-labeled PEGylated liposomes, we postulated that this treatment might enhance anti-tumor effect of Doxil (a liposomal anti-cancer agent). As expected, eribulin enhanced anti-tumor activity of Doxil in the PE-H1650 xenograft model. Then, we evaluated whether eribulin facilitated the recruitment of immune cells into the tumor. Infiltrating CD11b-positive immune cells were significantly increased in the multiple eribulin-treated xenografted tumors, and natural killer (NK) cell depletion reduced anti-tumor effects of eribulin. Collectively, these findings suggested a contribution of the immune cells for anti-tumor activities of eribulin. Taken together, our results obtained from multiple human cancer xenograft models suggested that vascular remodeling induced by eribulin therapy would act as a microenvironment modulator, and contributed to show anti-tumor effects of eribulin. Citation Format: Ken Ito, Shusei Hamamichi, Takanori Abe, Tsuyoshi Akagi, Hiroshi Shirota, Satoshi Kawano, Makoto Asano, Osamu Asano, Akira Yokoi, Junji Matsui, Izumi O. Umeda, Hirofumi Fujii. Eribulin modulates tumor microenvironment through vascular remodeling for antitumor effect in multiple mouse xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5927. doi:10.1158/1538-7445.AM2017-5927

Eribulin shows high concentration and long retention in xenograft tumor tissues

PurposeEribulin, a synthetic analog of the natural product halichondrin B, is a microtubule dynamics inhibitor. In this study, we report the pharmacokinetic profiles of eribulin in mice, rats, and dogs following intravenous administrations with optimized and validated bio-analytical methods.MethodsEribulin was administered at 0.5 and 2 mg/kg in mice, 0.5 and 1 mg/kg in rats, and 0.08 mg/kg in dogs. Tumor and brain penetration of eribulin was also evaluated in LOX human melanoma xenograft models. Concentrations in plasma, tumor, and brain were measured by the LC–MS/MS method.ResultsThe profiles of eribulin were characterized by extensive distribution, moderate clearance, and slow elimination in the three species. The pharmacokinetics are linear in mice and rats. In xenograft mice, the penetration into the brain was low, as expected, since eribulin is a P-glycoprotein substrate. In contrast to disposition in brain, the exposure of eribulin was approximately 20–30 times higher in tumor than that in plasma and half-lives were 17.8–35.9 h after both single and multiple dose regimens.ConclusionsEribulin was distributed rapidly and eliminated slowly in mice, rats, and dogs. The exposure of eribulin was approximately 20–30 times higher in tumor than in plasma in xenograft mice. These results might be caused by eribulin’s mechanism of action including increased perfusion in tumor by vascular remodeling effect.

Clinical efficacy of eribulin mesylate for the treatment of metastatic soft tissue sarcoma

ABSTRACTIntroduction: Metastatic soft tissue sarcoma, a devastating disease, has a median overall survival of only 12–18 months. Treatment options remain scarce. However, eribulin mesylate, a first-in-class halichondrin B-based microtubule dynamics inhibitor, has recently been approved for the management of patients with advanced liposarcoma.Areas covered: Based on a review of the literature between 2005 and 2017, we present a summary of eribulin mesylate’s mechanism of action and the studies showing its clinical efficacy in locally advanced or metastatic sarcomas.Expert commentary: Future development includes the definition of a biomarker signature related to patient outcome with eribulin. Further investigation via controlled clinical trials is needed to identify combination regimens that can optimize the efficacy of eribulin while providing an acceptable safety profile in sarcoma patients.

A phase II, multicenter, randomized trial of eribulin plus gemcitabine (EG) vs. paclitaxel plus gemcitabine (PG) in patients with HER2-negative metastatic breast cancer (MBC) as first-line chemotherapy (KCSG BR13-11, NCT02263495).

1082 Background: PG chemotherapy is one of the preferred chemotherapeutic regimens for patients with MBC. Eribulin mesylate is a non-taxane inhibitor of microtubule dynamics of the halichondrin class. A recent pooled analysis with eribulin showed improved overall survival (OS) in various patient subgroups. Furthermore, eribulin may have rational benefit compared with paclitaxel in terms of neurotoxicity. Methods: This study was a prospective randomized phase 2, open-label, two-arm, multi-center study comparing EG with PG chemotherapy for patients with HER-2 negative MBC as first-line treatment. Histologically confirmed breast cancer patients, at least 19 years of age, with no prior history of chemotherapy for MBC with evaluable lesions were included. Prior hormonal therapy as a treatment of Hormone Receptor (HR)-positive MBC was allowed. This design was hypothesized that EG chemotherapy would not be inferior to PG chemotherapy. The primary endpoint was Progression-Free Survival (PFS). Estimated 6 mo. PFS rate for each arm was 70%. The secondary endpoints were: Time to Treatment Failure (TTF); OS; neuropathic scale; toxicity; clinical benefit rate. Results: A total of 118 patients (median age: 50, 24-66) were enrolled between 2015 and 2016, and were randomly assigned to PG (n = 59) or EG (n = 59) chemotherapy. Mean number of metastatic sites was 3 (1-8). Six month PFS rates for both arms were 72% for EG and 73% for PG arm (p = 0.457). PFS in PG arm tends to be longer than in EG group (median PFS 12.6 for PG vs. 9.6 months for EG) without statistical significance. In addition, there was no significant difference in OS between the two groups (not reached vs. 21.2 months, p = 0.223). The median numbers of chemotherapy cycles of both groups were 8 for EG and 10 for PG (range 2-32). CBRs were 44% for EG and 45% for PG arm. Major toxicities were neutropenia and neurotoxicity. Grade II or more neurotoxicity was more common in PG than in EG group (40% vs.25%). Conclusions: EG chemotherapy showed similar clinical benefit with PG chemotherapy in terms of PFS but, more favorable neurotoxicity than PG chemotherapy. Clinical trial information: NCT02263495.

Multicenter study of the evaluation of eribulin (E) use in Sicily in metastatic breast cancer (MBC): A prospective registry (VESPRY trial).

e12565 Background: Eribulin Mesylate is a non taxane microtubule dynamics inhibitor, approved for heavily-pretreated MBC patients (pts). Methods: This is a multicenter, prospective, single arm study for E-treatment of third line in pretreated MBC pts, conducted in 14 oncology centers in Sicily. All pts had received two previous chemotherapy regimens for MBC. Pts received E at 1.23 mg/m2 on days 1,8 every 3 weeks until progression. Primary Endpoints: overall response rate (ORR) according to the site of metastases and safety. Secondary objectives: Progression-free survival (PFS) and ORR according to different subtypes. PFS curve was estimated using the Kaplan-Meier method. Multivariable logistic regression model were used to evaluate the associations of each variables with tumor response. ORR was assessed according to RECIST 1.1 and safety with CTCAE v4.0. Results: 122 pts were enrolled and received at least 1 dose of E. Median age was 58 (range 29-79). All received previously anthracycline and taxane based-therapies. Subtypes: Luminal A 69%, Luminal B 7%, HER2 enriched 4% and Triple Negative 20%. The most common metastatic sites were bone and liver; 67% had metastatic disease involving two or more organs. A median of 5 cycles of E (range 1-26) was administrated. 106/122 pts were evaluable for efficacy, all for safety. ORR was 48%. Exploratory subset analysis showed significantly higher ORR in the lung, liver and bone lesions compared to other site of metastases and in HER2 negative pts. Multivariable regression model showed that HER2 positive subtype was correlated with a poor response (odd ratio 6.7, 95% CI 1.2-36.5). The median PFS was 14.7 months (mos) (95% CI 7.2–25.7). Among pts with &lt; 65 and ≥ 65 years, the median PFS was 14.7 and 25.7 mos, respectively. Most common toxicities: G2 diarrhea 1%, asthenia G1 4%, G2 neutropenia 6%, G1 neurotoxicity 5%, QT prolongation 1%, G4 mucositis in only one case. Conclusions: This study showed a significant improved of PFS with E in third line setting and a favorable safety profile compared with results reported in the pivotal trial. Our findings suggest that E has substantial antitumor activity when used early for the treatment for MBC with acceptable safety.