A sensitive LC-MS/MS assay to quantitate free payload Aur0101 from ADC PYX-201 in rat and monkey plasma.

Aim: Aur0101 is a cytotoxic and small-molecule microtubule depolymerizing agent, and is the payload conjugated to antibody-drug conjugate PYX-201. Developing and validating a sensitive bioanalytical method to quantitate Aur0101 was novel and crucial in preclinical PYX-201 studies. Materials & methods: Reference standard Aur0101 and its stable isotope labelled internal standard Aur0101-d8 were used in this LC-MS/MS method. Results: This sensitive assay was validated at a lower limit of quantitation of 15 pg/ml and successfully applied to support preclinical rat and monkey toxicology studies. Preclinical plasma toxicokinetic parameters were presented. Conclusion: A sensitive and robust LC-MS/MS assay was validated for Aur0101 in rat and monkey plasma.

Cabazitaxel's ototoxicity: An animal study and histopathologic research.

Introduction: Chemotherapeutic agents can have both serious side effects and ototoxicity, which can be caused by direct toxic effects or by metabolic derangement by the agents. Cabazitaxel (CBZ) is a next-generation semi-synthetic taxane derivative that is effective in both preclinical models of human tumors that are sensitive or resistant to chemotherapy and in patients suffering from progressive prostate cancer despite docetaxel treatment. The primary aim of this study is to investigate the ototoxicity of CBZ in a rat model. Materials and Methods: : A total of 24 adult male Wistar-Albino rats were equally and randomly divided into four groups. CBZ (Jevtana, Sanofi-Aventis USA) was intraperitoneally administered to Groups 2, 3, and 4 at doses of 0.5, 1.0, and 1.5 mg/kg/week, respectively, for 4 consecutive weeks; Group 1 received only i.p. saline at the same time. At the end of the study, the animals were sacrificed and their cochlea removed for histopathological examination. Results: : Intraperitoneal administration of CBZ exerted an ototoxic effect on rats, and the histopathological results became worse in a dose-dependent manner (P < 0.05). Conclusion: : Our findings suggest that CBZ may be an ototoxic agent and can damage the cochlea. More clinical studies should be conducted to understand its ototoxicity.

Everolimus Acts in Synergy with Vinorelbine to Suppress the Growth of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is a challenging cancer to treat, as traditional chemotherapies have shown limited effectiveness. The mammalian target of rapamycin/sirolimus (mTOR) and microtubules are prominent druggable targets for HCC. In this study, we demonstrated that co-targeting mTOR using mTOR inhibitors (everolimus and sirolimus) along with the microtubule inhibitor vinorelbine yielded results superior to those of the monotherapies in HCC PDX models. Our research showed that the vinorelbine arrests cells at the mitotic phase, induces apoptosis, and normalizes tumor blood vessels but upregulates survivin and activates the mTOR/p70S6K/4EBP1 pathway. The addition of the everolimus significantly improved the tumor response to the vinorelbine, leading to improved overall survival (OS) in most tested orthotopic HCC PDX models. The mechanistic investigation revealed that this marked antitumor effect was accompanied by the downregulations of mTOR targets (p-p70S6K, p-4EBP1, and p-S6K); several key cell-cycle regulators; and the antiapoptotic protein survivin. These effects did not compromise the normalization of the blood vessels observed in response to the vinorelbine in the vinorelbine-sensitive PDX models or to the everolimus in the everolimus-sensitive PDX models. The combination of the everolimus and vinorelbine (everolimus/vinorelbine) also promoted apoptosis with minimal toxicity. Given the cost-effectiveness and established effectiveness of everolimus, and especially sirolimus, this strategy warrants further investigation in early-phase clinical trials.

Design and Synthesis of Novel Phenylahistin Derivatives Based on Co-Crystal Structures as Potent Microtubule Inhibitors for Anti-Cancer Therapy.

Phenylahistin is a naturally occurring marine product with a diketopiperazine structure that can bind to the colchicine site of microtubulin as a possible anticancer agent. To develop more potent microtubule inhibitors, novel phenylahistin derivatives were designed and synthesized based on the co-crystal complexes of phenylahistin derivatives and microtubulin. We established a focused library of imidazole-type molecules for the introduction of different groups to the C-ring and A-ring of phenylahistin. Structure-activity relationship studies indicated that appropriate hydrocarbon substituents and unsaturated alkenyl substituents at the 1-position of the imidazole group are important for improving the activity of such compounds. In addition, this study found that propylamine groups could maintain the activity of these compounds, as exemplified by compound 16d (IC50 = 5.38 nM, NCI-H460). Compound 15p (IC50 = 1.03 nM, NCI-H460) with an allyl group exhibited potent cytotoxic activity at the nanomolar level against human lung cancer cell lines. Immunofluorescence assay indicated that compound 15p could efficiently inhibited microtubule polymerization and induced a high expression of caspase-3. 15p also displayed good pharmacokinetic characteristics in vitro. Additionally, the growth of H22 transplanted tumors was significantly inhibited in BALB/c mice when 15p alone was administered at 4 mg/kg, and the tumor inhibition rate was as much as 65%. Importantly, the continuous administration of 15p resulted in a lower toxicity than that of docetaxel (10 mg/kg) and cyclophosphamide (20 mg/kg). Overall, the novel allyl-imidazole-diketopiperazine-type derivatives could be considered safe and effective potential agents for cancer treatment.

BPR0C261, An Analogous of Microtubule Disrupting Agent D-24851 Enhances the Radiosensitivity of Human Non-Small Cell Lung Cancer Cells via p53-Dependent and p53-Independent Pathways.

(1) Destabilization of microtubule dynamics is a primary strategy to inhibit fast growing tumor cells. The low cytotoxic derivative of microtubule inhibitor D-24851, named BPR0C261 exhibits antitumor activity via oral administration. In this study, we investigated if BPR0C261 could modulate the radiation response of human non-small cell lung cancer (NSCLC) cells with or without p53 expression. (2) Different doses of BPR0C261 was used to treat human NSCLC A549 (p53+/+) cells and H1299 (p53-/-) cells. The cytotoxicity, radiosensitivity, cell cycle distribution, DNA damage, and protein expression were evaluated using an MTT assay, a colony formation assay, flow cytometry, a comet assay, and an immunoblotting analysis, respectively. (3) BPR0C261 showed a dose-dependent cytotoxicity on A549 cells and H1299 cells with IC50 at 0.38 µM and 0.86 µM, respectively. BPR0C261 also induced maximum G2/M phase arrest and apoptosis in both cell lines after 24 h of treatment with a dose-dependent manner. The colony formation analysis demonstrated that a combination of low concentration of BPR0C261 and X-rays caused a synergistic radiosensitizing effect on NSCLC cells. Additionally, we found that a low concentration of BPR0C261 was sufficient to induce DNA damage in these cells, and it increased the level of DNA damage induced by a fractionation radiation dose (2 Gy) of conventional radiotherapy. Furthermore, the p53 protein level of A549 cell line was upregulated by BPR0C261. On the other hand, the expression of PTEN tumor suppressor was found to be upregulated in H1299 cells but not in A549 cells under the same treatment. Although radiation could not induce PTEN in H1299 cells, a combination of low concentration of BPR0C261 and radiation could reverse this situation. (4) BPR0C261 exhibits specific anticancer effects on NSCLC cells by the enhancement of DNA damage and radiosensitivity with p53-dependent and p53-independent/PTEN-dependent manners. The combination of radiation and BPR0C261 may provide an important strategy for the improvement of radiotherapeutic treatment.

pH-sensitive nanomedicine of novel tubulin polymerization inhibitor for lung metastatic melanoma.

Microtubule binding agents such as paclitaxel and vincristine have activity in metastatic melanoma. However, even responsive tumors develop resistance, highlighting the need to investigate new drug molecules. Here, we showed that a new compound, CH-2-102, developed by our group, has high anti-tumor efficacy in human and murine melanoma cells. We confirmed that CH-2-102 robustly suppresses the microtubule polymerization process by directly interacting with the colchicine binding site. Our results unveil that CH-2-102 suppresses microtubule polymerization and subsequently induces G2 phase cell arrest as one of the possible mechanisms. Notably, CH-2-102 maintains its efficacy even in the paclitaxel resistance melanoma cells due to different binding sites and a non-Pgp substrate. We developed a pH-responsive drug-polymer Schiff bases linker for high drug loading into nanoparticles (NPs). Our CH-2-102 conjugated NPs induced tumor regression more effectively than Abraxane® (Nab-paclitaxel, N-PTX), free drug, and non-sensitive NPs in B16-F10 cell-derived lung metastasis mouse model. Furthermore, our results suggest that the formulation has a high impact on the in vivo efficacy of the drug and warrants further investigation in other cancers, particularly taxane resistant. In conclusion, the microtubule polymerization inhibitor CH-2-102 conjugated pH-responsive NPs induce tumor regression in lung metastasis melanoma mice, suggesting it may be an effective strategy for treating metastatic melanoma.

Synergistic inhibition of hepatitis C virus infection by a novel microtubule inhibitor in combination with daclatasvir.

Even though substantial progress has been made in the treatment of hepatitis C virus (HCV) infection, viral resistance and relapse still occur in some patients and additional therapeutic approaches may ultimately be needed should viral resistance become more prevalent. Microtubules play important roles in several HCV life cycle events, including cell attachment, entry, cellular transportation, morphogenesis and progeny secretion steps. Therefore, it was hypothesized that microtubular inhibition might be a novel approach for the treatment of HCV infection. Here, the inhibitory effects of our recently developed microtubule inhibitors were studied in the HCV replicon luciferase reporter system and the infectious system. In addition, the combination responses of microtubule inhibitors with daclatasvir, which is a clinically used HCV NS5A inhibitor, were also evaluated. Our results indicated that microtubule targeting had activity against HCV replication and showed synergistic effect with a current clinical drug.

Antitumoral Effect of Plocabulin in High Grade Serous Ovarian Carcinoma Cell Line Models.

Ovarian cancer (OC) is a life-threatening tumor and the deadliest among gynecological cancers in developed countries. First line treatment with a carboplatin/paclitaxel regime is initially effective in the majority of patients, but most advanced OC will recur and develop drug resistance. Therefore, the identification of alternative therapies is needed. In this study, we employed a panel of high-grade serous ovarian cancer (HGSOC) cell lines, in monolayer and three-dimensional cell cultures. We evaluated the effects of a novel tubulin-binding agent, plocabulin, on proliferation, cell cycle, migration and invasion. We have also tested combinations of plocabulin with several drugs currently used in OC in clinical practice. Our results show a potent antitumor activity of plocabulin, inhibiting proliferation, disrupting microtubule network, and decreasing their migration and invasion capabilities. We did not observe any synergistic combination of plocabulin with cisplatin, doxorubicin, gemcitabine or trabectedin. In conclusion, plocabulin has a potent antitumoral effect in HGSOC cell lines that warrants further clinical investigation.

5-arylalkynyl-2-benzoyl thiophene: a novel microtubule inhibitor exhibits antitumor activity without neurological toxicity.

The composition of microtubules involving several steps, including the polymerization and depolymerization of α-tubulin and ß-tubulin heterodimers. Microtubule-targeting agents can increase or inhibit microtubule polymerization, thereby disrupting the dynamic process and stalling cells in G2/M phase. Microtubule-targeting agents are generally cytotoxic, which neurological toxicity being one of the significant adverse events associated. We recently reported a novel 5-arylalkynyl-2-benzoyl thiophene (PST-3) that exhibited broad-spectrum cellular cytotoxicity and in vivo potency with high safety. PST-3 was a substrate of p-gp, which could not cross the blood-brain barrier and lead to less neurotoxicity. The antitumor activities in vitro demonstrated that PST-3 combined with the colchicine-binding site on microtubule, induces morphological changes, disrupts microtubule networks, inhibits polymerization of tubulin, arrests breast cancer cells in the G2/M phase of the cell cycle and induces apoptosis. Evaluation of the antitumor effect in vivo demonstrated that PST-3 elicited MDA-MB-468 tumor %T/C of 11.75%, whereas elicited MCF7 tumor %T/C of 44.38% in breast cancer xenograft models. Besides, in vivo experiments of a higher dose (60 mg/kg) of PST-3 treatment for 21 days did not produce any significant neurotoxicity. These results provide evidence that PST-3 might possess the potential to be developed into a new microtubule inhibitor without neurological toxicity.

IMB5476, a novel microtubule inhibitor, induces mitotic catastrophe and overcomes multidrug resistance in tumors.

IMB5046 is a nitrobenzoate microtubule inhibitor we reported previously. During screening of its structural analogues, we identified a novel compound IMB5476 with increased aqueous solubility. Here, its antitumor activity and the underlying mechanism were investigated. IMB5476 disrupted microtubule networks in cells and arrested cell cycle at G2/M phase. It inhibited purified tubulin polymerization in vitro. Competition assay indicated that it bound to tubulin at the colchicine pocket. Further experiments proved that it induced cell death by mitotic catastrophe and apoptosis. Notably, it was a poor substrate of P-glycoprotein and exhibited potent cytotoxicity against drug-resistant tumor cells. In addition, IMB5476 could inhibit angiogenesis in vitro. IMB5476 also inhibited the growth of drug-resistant KBV200 xenografts in mice. Conclusively, our data reveal a novel nitrobenzoate microtubule inhibitor with improved aqueous solubility and can overcome multidrug resistance.

Photoswitchable Epothilone-Based Microtubule Stabilisers Allow GFP-Imaging-Compatible, Optical Control over the Microtubule Cytoskeleton.

Optical methods to modulate microtubule dynamics show promise for reaching the micron- and millisecond-scale resolution needed to decrypt the roles of the cytoskeleton in biology. However, optical microtubule stabilisers are under-developed. We introduce "STEpos" as GFP-orthogonal, light-responsive epothilone-based microtubule stabilisers. They use a novel styrylthiazole photoswitch in a design to modulate hydrogen-bonding and steric effects that control epothilone potency. STEpos photocontrol microtubule dynamics and cell division with micron- and second-scale spatiotemporal precision. They substantially improve potency, solubility, and ease-of-use compared to previous optical microtubule stabilisers, and the structure-photoswitching-activity relationship insights in this work will guide future optimisations. The STEpo reagents can contribute greatly to high-precision research in cytoskeleton biophysics, cargo transport, cell motility, cell division, development, and neuroscience.

Eribulin prolongs survival in an orthotopic xenograft mouse model of malignant meningioma.

Meningioma is the most common intracranial tumor, with generally favorable patient prognosis. However, patients with malignant meningioma typically experience recurrence, undergo multiple surgical resections, and ultimately have a poor prognosis. Thus far, effective chemotherapy for malignant meningiomas has not been established. We recently reported the efficacy of eribulin (Halaven) for glioblastoma with a telomerase reverse transcriptase (TERT) promoter mutation. This study investigated the anti-tumor effect of eribulin against TERT promoter mutation-harboring human malignant meningioma cell lines in vitro and in vivo. Two meningioma cell lines, IOMM-Lee and HKBMM, were used in this study. The strong inhibition of cell proliferation by eribulin via cell cycle arrest was demonstrated through viability assay and flow cytometry. Apoptotic cell death in malignant meningioma cell lines was determined through vital dye assay and immunoblotting. Moreover, a wound healing assay revealed the suppression of tumor cell migration after eribulin exposure. Intraperitoneal administration of eribulin significantly prolonged the survival of orthotopic xenograft mouse models of both malignant meningioma cell lines implanted in the subdural space (P < .0001). Immunohistochemistry confirmed apoptosis in brain tumor tissue treated with eribulin. Overall, these results suggest that eribulin is a potential therapeutic agent for malignant meningiomas.

Phase I Dose-Escalation Study of SCB01A, a Microtubule Inhibitor with Vascular Disrupting Activity, in Patients with Advanced Solid Tumors.

LESSONS LEARNED: SCB01A is a novel microtubule inhibitor with vascular disrupting activity. This first-in-human study demonstrated SCB01A safety, pharmacokinetics, and preliminary antitumor activity. SCB01A is safe and well tolerated in patients with advanced solid malignancies with manageable neurotoxicity. BACKGROUND: SCB01A, a novel microtubule inhibitor, has vascular disrupting activity. METHODS: In this phase I dose-escalation and extension study, patients with advanced solid tumors were administered intravenous SCB01A infusions for 3 hours once every 21 days. Rapid titration and a 3 + 3 design escalated the dose from 2 mg/m2 to the maximum tolerated dose (MTD) based on dose-limiting toxicity (DLT). SCB01A-induced cellular neurotoxicity was evaluated in dorsal root ganglion cells. The primary endpoint was MTD. Safety, pharmacokinetics (PK), and tumor response were secondary endpoints. RESULTS: Treatment-related adverse events included anemia, nausea, vomiting, fatigue, fever, and peripheral sensorimotor neuropathy. DLTs included grade 4 elevated creatine phosphokinase (CPK) in the 4 mg/m2 cohort; grade 3 gastric hemorrhage in the 6.5 mg/m2 cohort; grade 2 thromboembolic event in the 24 mg/m2 cohort; and grade 3 peripheral sensorimotor neuropathy, grade 3 elevated aspartate aminotransferase, and grade 3 hypertension in the 32 mg/m2 cohort. The MTD was 24 mg/m2 , and average half-life was ~2.5 hours. The area under the curve-dose response relationship was linear. Nineteen subjects were stable after two cycles. The longest treatment lasted 24 cycles. SCB01A-induced neurotoxicity was reversible in vitro. CONCLUSION: The MTD of SCB01A was 24 mg/m2 every 21 days; it is safe and tolerable in patients with solid tumors.

AMXI-5001, a novel dual parp1/2 and microtubule polymerization inhibitor for the treatment of human cancers.

Poly (ADP-ribose) polymerase (PARP) has recently emerged as a central mediator in cancer resistance against numerous anticancer agents to include chemotherapeutic agents such as microtubule targeting agents and DNA damaging agents. Here, we describe AMXI-5001, a novel, highly potent dual PARP1/2 and microtubule polymerization inhibitor with favorable metabolic stability, oral bioavailability, and pharmacokinetic properties. The potency and selectivity of AMXI-5001 were determined by biochemical assays. Anticancer activity either as a single-agent or in combination with other antitumor agents was evaluated in vitro. In vivo antitumor activity as a single-agent was assessed in a triple-negative breast cancer (TNBC) model. AMXI-5001 demonstrates comparable IC50 inhibition against PARP and microtubule polymerization as clinical PARP inhibitors (Olaparib, Rucaparib, Niraparib, and Talazoparib) and the potent polymerization inhibitor (Vinblastine), respectively. In vitro, AMXI-5001 exhibited selective antitumor cytotoxicity across a wide variety of human cancer cells with much lower IC50s than existing clinical PARP1/2 inhibitors. AMXI-5001 is highly active in both BRCA mutated and wild type cancers. AMXI-5001 is orally bioavailable. AMXI-5001 elicited a remarkable In vivo preclinical anti-tumor activity in a BRCA mutated TNBC model. Oral administration of AMXI-5001 induced complete regression of established tumors, including exceedingly large tumors. AMXI-5001 resulted in superior anti-tumor effects compared to either single agent (PARP or microtubule) inhibitor or combination with both agents. AMXI-5001 will enter clinical trial testing soon and represents a promising, novel first in class dual PARP1/2 and microtubule polymerization inhibitor that delivers continuous and synchronous one-two punch cancer therapy with one molecule.

Upconverting Nanocarriers Enable Triggered Microtubule Inhibition and Concurrent Ferroptosis Induction for Selective Treatment of Triple-Negative Breast Cancer.

Despite the resistance of triple-negative breast cancer (TNBC) to targeted hormone therapy, the discovery of azobenzene combretastatin A4 (Azo-CA4) provides therapeutic opportunities for TNBC. Here, Azo-CA4 was loaded in upconverting nanocarriers that could convert near-infrared (NIR) light to UV light to activate Azo-CA4. Upon irradiation, Azo-CA4-loaded nanocarriers significantly reduced the viability of TNBC cells via both apoptosis and ferroptosis. The former was induced by photoisomerization of Azo-CA4, accompanied by microtubule breakdown and cell cycle arrest at G2/M phase. The latter was caused by the UV light-induced reduction of Fe3+ to Fe2+ that facilitates the peroxidation of tailored lipids. The cooperation between apoptosis and ferroptosis in eliminating TNBC was demonstrated in a xenograft mice model in terms of histological staining, tumor growth inhibition, and animal survival. Since the NIR light is only applied to the tumor site, the adverse effects of such triggered nanocarriers to the healthy organs are negligible.

Structure-based design and synthesis of novel furan-diketopiperazine-type derivatives as potent microtubule inhibitors for treating cancer.

Plinabulin, a synthetic analog of the marine natural product "diketopiperazine phenylahistin," displayed depolymerization effects on microtubules and targeted the colchicine site, which has been moved into phase III clinical trials for the treatment of non-small cell lung cancer (NSCLC) and the prevention of chemotherapy-induced neutropenia (CIN). To develop more potent anti-microtubule and cytotoxic derivatives, the co-crystal complexes of plinabulin derivatives were summarized and analyzed. We performed further modifications of the tert-butyl moiety or C-ring of imidazole-type derivatives to build a library of molecules through the introduction of different groups for novel skeletons. Our structure-activity relationship study indicated that compounds 17o (IC50 = 14.0 nM, NCI-H460) and 17p (IC50 = 2.9 nM, NCI-H460) with furan groups exhibited potent cytotoxic activities at the nanomolar level against various human cancer cell lines. In particular, the 5-methyl or methoxymethyl substituent of furan group could replace the alkyl group of imidazole at the 5-position to maintain cytotoxic activity, contradicting previous reports that the tert-butyl moiety at the 5-position of imidazole was essential for the activity of such compounds. Immunofluorescence assay indicated that compounds 17o and 17p could efficiently inhibit microtubule polymerization. Overall, the novel furan-diketopiperazine-type derivatives could be considered as a potential scaffold for the development of anti-cancer drugs.

Pharmacokinetics of a novel microtubule inhibitor mHA11 in rats.

mHA11, a 2-amino-4-phenyl-4H-chromene-3-carboxylate analog, is a microtubule-targeting agent discovered by our group through the modification of the Bcl-2 inhibitor HA14-1. mHA11 exhibits cytotoxicities against tumor cells with nM IC50 values, whereas it has only a minimal effect on normal cells. We explored the plasma pharmacokinetics, tissue distribution, and excretion of mHA11 in rats using a liquid chromatography/tandem mass spectrometry (LC-MS/MS) method. Next, we identified the metabolites of mHA11 and assessed the influence of cytochrome P450 (CYP) isozymes on mHA11 metabolism. We also examined the in vitro stability in rat plasma and rat liver microsomes (RLMs), the blood-to plasma (B/P) ratio, and the inhibitory effect on CYP isozyme activities. After oral administration at 5, 15, and 45 mg/kg, mHA11 was absorbed and eliminated rapidly. There was a linear correlation between the area under the concentration-time curve (AUC0-∞) and the dose (R2 = 0.983). The bioavailability of mHA11 was 4.1% at the oral dose of 15 mg/kg mHA11 was extensively distributed in various tissues and exhibited a high penetration into the brain. No significant parent drug was detected in urine or bile, and only 0.74% was recovered in feces, whereas two demethylated metabolites, M1 and M2, were found in the urine and feces, and further studies showed that CYP2C19 primarily contributed to metabolites formation. mHA11 was stable in rat plasma but degraded significantly in RLMs; its B/P ratio was 1.05 in rat blood. In addition, mHA11 dose-dependently inhibited the activities of rat CYP isozymes, including CYP1A2, CYP2C6, CYP2C11, CYP2D2, CYP2E1 and CYP3A2. The present study is the first report on the disposition of mHA11 in rats and provides important data for further research and development of this inhibitor.

Perspectives on the mechanism of action and clinical application of eribulin for metastatic breast cancer.

Eribulin is a novel microtubule inhibitor with mitotic and nonmitotic mechanisms of action. Both pooled and subgroup analyses from large-scale Phase III clinical trials demonstrated that eribulin has substantial activity in patients with pretreated (anthracycline and a taxane) advanced or metastatic breast cancer. We review recent pharmacological and clinical findings pertaining to eribulin use in metastatic breast cancer - particularly highlighting eribulin in difficult-to-treat and aggressive disease, and safety data in specific patient populations. Additionally, recent advancements in our understanding of the mechanism of action of eribulin and potential future directions for its clinical development are discussed. Ongoing studies of eribulin in combination with immunotherapies and established cytotoxic agents may help shape the future landscape of breast cancer treatment.

First-in-human phase I study of the microtubule inhibitor plocabulin in patients with advanced solid tumors.

Background Plocabulin (PM060184) is a novel marine-derived microtubule inhibitor that acts as an antitumor agent. This first-in-human study evaluated dose-limiting toxicities (DLT) to define the maximum tolerated dose (MTD) and phase II recommended dose (RD) of plocabulin given as a 10-min infusion on Day (D) 1, D8 and D15 every four weeks. Patients and methods Forty-four patients with advanced solid tumors received plocabulin following an accelerated titration design. Results Plocabulin was escalated from 1.3 mg/m2 to 14.5 mg/m2, which was defined as the MTD. No RD was confirmed, because frequent dose delays and omissions resulted in low relative dose intensity (66%) at the 12.0 mg/m2 expansion cohort. The main DLT was grade 3 peripheral sensory neuropathy (PSN); other DLTs were grade 4 tumor lysis syndrome, grade 4 cardiac failure and grade 3 myalgia. Toxicities were mainly mild to moderate, and included abdominal pain, myalgia, fatigue, nausea, and vomiting. Myelosuppression was transient and manageable. Plocabulin had a half-life of ~4 h and a wide diffusion to peripheral tissues. Antitumor response was observed in cervix carcinoma and heavily pretreated metastatic non-small cell lung cancer patients, and disease stabilization (≥3 months) in patients with colorectal, thymic, gastrointestinal stromal and breast tumors, among others. The clinical benefit rate was 33%. Conclusion The main DLT of plocabulin was PSN, as anticipated for a tubulin-binding agent. Since encouraging antitumor activity was observed, efforts to improve toxicity and to find the RD were planned in other trials evaluating D1&D8 and D1-D3 plus D15-D17 schedules.

Synthesis and anti-angiogenic activity of a novel microtubule inhibitor IMB5046 / 药学学报

IMB5046 is a newly discovered nitrobenzoate functioning as a microtubule inhibitor. Here we report its synthesis and in vitro anti-angiogenic activity. IMB5046 was synthesized by conjugation of 2-morpholin-4-yl-5-nitrobenzoic acid with 4-(methylthio)benzyl alcohol via two-step reactions. The structure of the end product was verified using 1H NMR and HR-MS spectroscopy. The effect of these compounds on cell proliferation was determined using MTT assay, and their impact on cytoskeleton was investigated using fluorescence assay. Flow cytometry was performed to examine the effect of IMB5046 on cell cycle. Cell wound scratch assay and Transwell assay were performed to examine cell migration. Endothelial tube formation assay was used to evaluate the anti-angiogenic activity of IMB5046. The results indicated that IMB5046 induced endothelial cell contraction and microtubule depolymerization, and inhibited the proliferation of endothelial cells and tumor cells, while two raw materials showed no obvious effects. IMB5046 arrested cell cycle at G2/M phase, even at low-cytotoxic concentrations it significantly inhibited the motility of endothelial cells. IMB5046 inhibited the tube formation of endothelial cells according to the number of tubes and junctions. In conclusion, IMB5046 is a promising microtubule-targeting drug with anti-angiogenic activity.