Structure-Based Design and Synthesis of N-Substituted 3-Amino-ß-Carboline Derivatives as Potent αß-Tubulin Degradation Agents.

So far, relatively few small molecules have been reported to promote tubulin degradation. Our previous studies have found that compound 2, a noncovalent colchicine-site ligand, was capable of promoting αß-tubulin degradation. To further improve its antiproliferative activity, 66 derivatives or analogues of 2 were designed and synthesized based on 2-tubulin cocrystal structure. Among them, 12b displayed nanomolar potency against a variety of tumor cells, including paclitaxel- and adriamycin-resistant cell lines. 12b binds to the colchicine site and promotes αß-tubulin degradation in a concentration-dependent manner via the ubiquitin-proteasome pathway. The X-ray crystal structure revealed that 12b binds in a similar manner as 2, but there is a slight conformation change of the B ring, which resulted in better interaction of 12b with surrounding residues. 12b effectively suppressed tumor growth at an i.v. dose of 40 mg/kg (3 times a week) on both A2780S (paclitaxel-sensitive) and A2780T (paclitaxel-resistant) ovarian xenograft models, with respective TGIs of 92.42 and 79.75% without obvious side effects, supporting its potential utility as a tumor-therapeutic compound.

3D modelling of drug-coated balloons for the treatment of calcified superficial femoral arteries.

BACKGROUND/OBJECTIVES: Drug-coated balloon therapy for diseased superficial femoral arteries remains controversial. Despite its clinical relevance, only a few computational studies based on simplistic two-dimensional models have been proposed to investigate this endovascular therapy to date. This work addresses the aforementioned limitation by analyzing the drug transport and kinetics occurring during drug-coated balloon deployment in a three-dimensional geometry. METHODS: An idealized three-dimensional model of a superficial femoral artery presenting with a calcific plaque and treated with a drug-coated balloon was created to perform transient mass transport simulations. To account for the transport of drug (i.e. paclitaxel) released by the device, a diffusion-reaction equation was implemented by describing the drug bound to specific intracellular receptors through a non-linear, reversible reaction. The following features concerning procedural aspects, pathologies and modelling assumptions were investigated: (i) balloon application time (60-180 seconds); (ii) vessel wall composition (healthy vs. calcified wall); (iii) sequential balloon application; and (iv) drug wash-out by the blood stream vs. coating retention, modeled as exponential decay. RESULTS: The balloon inflation time impacted both the free and specifically-bound drug concentrations in the vessel wall. The vessel wall composition highly affected the drug concentrations. In particular, the specifically-bound drug concentration was four orders of magnitude lower in the calcific compared with healthy vessel wall portions, primarily as a result of reduced drug diffusion. The sequential application of two drug-coated balloons led to modest differences (~15%) in drug concentration immediately after inflation, which became negligible within 10 minutes. The retention of the balloon coating increased the drug concentration in the vessel wall fourfold. CONCLUSIONS: The overall findings suggest that paclitaxel kinetics may be affected not only by the geometrical and compositional features of the vessel treated with the drug-coated balloon, but also by balloon design characteristics and procedural aspects that should be carefully considered.

Design, Synthesis, and Biological Evaluation of Stable Colchicine-Binding Site Tubulin Inhibitors 6-Aryl-2-benzoyl-pyridines as Potential Anticancer Agents.

We previously reported a potent tubulin inhibitor CH-2-77. In this study, we optimized the structure of CH-2-77 by blocking metabolically labile sites and synthesized a series of CH-2-77 analogues. Two compounds, 40a and 60c, preserved the potency while improving the metabolic stability over CH-2-77 by 3- to 4-fold (46.8 and 29.4 vs 10.8 min in human microsomes). We determined the high-resolution X-ray crystal structures of 40a (resolution 2.3 Å) and 60c (resolution 2.6 Å) in complex with tubulin and confirmed their direct binding at the colchicine-binding site. In vitro, 60c maintained its mode of action by inhibiting tubulin polymerization and was effective against P-glycoprotein-mediated multiple drug resistance and taxol resistance. In vivo, 60c exhibited a strong inhibitory effect on tumor growth and metastasis in a taxol-resistant A375/TxR xenograft model without obvious toxicity. Collectively, this work showed that 60c is a promising lead compound for further development as a potential anticancer agent.

Preclinical and Early Clinical Development of PTC596, a Novel Small-Molecule Tubulin-Binding Agent.

PTC596 is an investigational small-molecule tubulin-binding agent. Unlike other tubulin-binding agents, PTC596 is orally bioavailable and is not a P-glycoprotein substrate. So as to characterize PTC596 to position the molecule for optimal clinical development, the interactions of PTC596 with tubulin using crystallography, its spectrum of preclinical in vitro anticancer activity, and its pharmacokinetic-pharmacodynamic relationship were investigated for efficacy in multiple preclinical mouse models of leiomyosarcomas and glioblastoma. Using X-ray crystallography, it was determined that PTC596 binds to the colchicine site of tubulin with unique key interactions. PTC596 exhibited broad-spectrum anticancer activity. PTC596 showed efficacy as monotherapy and additive or synergistic efficacy in combinations in mouse models of leiomyosarcomas and glioblastoma. PTC596 demonstrated efficacy in an orthotopic model of glioblastoma under conditions where temozolomide was inactive. In a first-in-human phase I clinical trial in patients with cancer, PTC596 monotherapy drug exposures were compared with those predicted to be efficacious based on mouse models. PTC596 is currently being tested in combination with dacarbazine in a clinical trial in adults with leiomyosarcoma and in combination with radiation in a clinical trial in children with diffuse intrinsic pontine glioma.

Design, Synthesis, and Bioactivity Evaluation of Dual-Target Inhibitors of Tubulin and Src Kinase Guided by Crystal Structure.

Klisyri (KX01) is a dual tubulin/Src protein inhibitor that has shown potential therapeutic effects in several tumor models. However, a phase II clinical trial in patients with bone-metastatic castration-resistant prostate cancer was halted because of lack of efficacy. We previously reported that KX01 binds to the colchicine site of ß-tubulin and its morpholine group lies close to α-tubulin's surface. Thus, we hypothesized that enhancing the interaction of KX01 with α-tubulin could increase tubulin inhibition and synthesized a series of KX01 derivatives directed by docking studies. Among these derivatives, 8a exhibited more than 10-fold antiproliferation activity in several tumor cells than KX01 and significantly improved in vivo antitumor effects. The X-ray crystal structure suggested that 8a both bound to the colchicine site and extended into the interior of α-tubulin to form potent interactions, presenting a novel binding mode. A potential clinical candidate for cancer therapy was identified in this study.

Vincristine-Induced Peripheral Neuropathy (VIPN) in Pediatric Tumors: Mechanisms, Risk Factors, Strategies of Prevention and Treatment.

Vincristine-induced peripheral neurotoxicity (VIPN) is a very common side effect of vincristine chemotherapy among pediatric patients with cancer. Neuropathy may be sensory, motor and/or autonomic, with consequent reduction, delay or discontinuation of vincristine-chemotherapy, but also pain, disability, reduced quality of life of patients and an increase in medical costs. Vincristine acts out its antineoplastic function by altering the normal assembly and disassembly of microtubules, with their consequent mitosis block and death. Vincristine leads to VIPN through a complex mechanism of damage, which occurs not only on the microtubules, but also on the endothelium and the mitochondria of nerve cells. Furthermore, both patient-related risk factors (age, race, ethnicity and genetic polymorphisms) and treatment-related risk factors (dose, time of infusion and drug-drug interactions) are involved in the pathogenesis of VIPN. There is a lack of consensus about the prophylaxis and treatment of VIPN among pediatric oncologic patients, despite several molecules (such as gabapentin, pyridoxine and pyridostigmine, glutamic acid and glutamine) having been already investigated in clinical trials. This review describes the molecular mechanisms of VIPN and analyzes the risk factors and the principal drugs adopted for the prophylaxis and treatment of VIPN in pediatric patients with cancer.

High-resolution X-ray structure of three microtubule-stabilizing agents in complex with tubulin provide a rationale for drug design.

Microtubule is a key component of cytoskeleton and has been considered as an important target for the treatment of cancer. In particular, the tubulin taxane-site inhibitors such as taxol analogs and epothilones have achieved great success in clinical trials. However, the structural basis of many taxane-site inhibitors is still lacking in exploring their mechanism of action. We here reported crystal complex structures for three taxane-site inhibitors, Ixabepilone, Epothilone B, and Epothilone D, which were determined to 2.4 Å, 2.4 Å, and 2.85 Å, respectively. The crystal structures revealed that these taxane-site inhibitors possess similar binding modes to that of Epothilone A at the taxane site, e.g. making critical hydrogen-bonding interactions with multiple residues on the M-loop, which facilitating the tubulin polymerization. Furthermore, we summarized the binding modes of almost all taxane-site inhibitors and identified novel taxane-site ligands with simpler chemical structures through virtual screening. On this basis, new derivatives with higher binding affinity to tubulin were designed and developed, which can form additional hydrogen bond interactions with tubulin. Overall, this work determined the mechanism of action of epothilones and provided a structural basis to design reasonably novel taxane-site inhibitors with simpler structure and improved pharmacokinetic properties.

Different pharmaceutical preparations of colchicine for Familial Mediterranean Fever: are they the same?

This study aimed to investigate the benefit of changing the pharmaceutical preparation of colchicine in Turkish Familial Mediterranean Fever (FMF) patients resistant to one preparation in terms of frequency of the attacks. Turkish adult FMF patients under treatment with an imported colchicine preparation-in the form of compressed tablet form-due to resistance to domestic colchicine preparations, which are film- or sugar-coated tablets, and not using anti-interleukin-1 or other biologic agents were included in the study. Baseline disease characteristics along with MEFV mutations were identified. Daily colchicine doses and attack frequencies before and after the pharmaceutical change were compared. Fifty patients resistant to coated tablet preparations of colchicine and under treatment with the compressed tablets were identified. The median duration of disease was 6 (interquartile range 2.7-14) years and duration under treatment with the imported colchicine was 21 (range 8-60) months. Eight (16%), ten (20%), and 32 (64%) patients had 0-3, 4-6, and more than 7 attacks per year, respectively, before the compressed tablets. After treatment with the compressed tablet form of colchicine, 44 (88%), 5 (10%), and 1 (2%) patients had 0-3, 4-6, and more than 7 attacks, respectively (p < 0.0001). Daily colchicine doses were similar before and after the pharmaceutical change (1.85 ± 0.47 vs 1.84 ± 0.37 mg, p = 0.9). Turkish FMF patients with ongoing attacks under domestic coated tablet preparations of colchicine may benefit from the compressed colchicine tablets. This may be explained by the difference in pharmacokinetic properties of different colchicine preparations.

Combination of a novel microtubule inhibitor MBRI-001 and gemcitabine synergistically induces cell apoptosis by increasing DNA damage in pancreatic cancer cell lines.

Pancreatic cancer (PC) is a highly malignant cancer with poor prognosis. Although gemcitabine (GEM; 2',2'-difluoro-deoxycytidine) has been used as the first-line chemotherapeutic agent in PC treatment for decades, its limited efficacy remains a significant clinical issue, which may be resolved by GEM combination therapy. In this study, we aimed to investigate the anti-tumor effects of MBRI-001 in combination with GEM in BxPC-3 and MIA PaCa-2 human PC cell lines. In vitro and in vivo results indicate that MBRI-001 showed synergistic activity with GEM. GEM induced apoptosis by increasing DNA damage (phosphorylated core histone protein H2AX (γ-H2AX)), MBRI-001 activated mitochondrial-apoptotic pathway (cleaved poly-ADP ribose polymerase (PARP)). Thus, the combination of the two intensified both apoptosis and DNA damage and showed significantly superior anti-tumor activity compared to each agent alone. The adoption of combination of MBRI-001 with GEM may be beneficial as they act synergistically and thus, can be a potential therapeutic choice for improving the prognosis of PC patients in the future.

Pharmacokinetic studies of a novel tubulin inhibitor SK1326 in rat plasma by UPLC-MS/MS.

A sensitive method for quantitation of SK1326 in rat plasma has been established using ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI/MS/MS). SK1326 and the internal standard (tramadol) in plasma sample were extracted using acetonitrile. A centrifuged upper layer was then evaporated and reconstituted with a mobile phase of 0.5% formic acid-acetonitrile (35:65, v/v). The reconstituted samples were injected into a C18 reversed-phase column. Using MS/MS in the multiple reaction monitoring mode, SK1326 and tramadol were detected without severe interference from the rat plasma matrix. SK1326 produced a protonated precursor ion ([M + H]+ ) at m/z 432.3 and a corresponding product ion at m/z 114.4. The internal standard produced a protonated precursor ion ([M + H]+ ) at m/z 264.4 and a corresponding product ion at m/z 58.1. Detection of SK1326 in rat plasma by the UPLC-ESI/MS/MS method was accurate and precise with a quantitation limit of 1.0 ng/mL. The validation, reproducibility, stability and recovery of the method were evaluated. The method has been successfully applied to pharmacokinetic studies of SK1326 in rat plasma. The pharmacokinetic parameters of SK1326 were evaluated after intravenous (at a dose of 10 mg/kg) and oral (at a dose of 20 mg/kg) administration of SK1326 in rats. After oral administration (20 mg/kg) of SK1326, the F (fraction absorbed) value was ~77.1%.

Design, synthesis, antitumor activities and biological studies of novel diaryl substituted fused heterocycles as dual ligands targeting tubulin and katanin.

Microtubule is one of the important targets for cancer treatment. A novel class of diaryl substituted imidazo[4,5-c]pyridin-2-ones and imidazo[4,5-c]pyridines were designed based on combination principles by merging the structures of ß-lactams and purine-type compounds known as tubulin polymerization inhibitor and katanin activity up-regulator, respectively. Their antitumor activities were evaluated in vitro and the mechanism was elucidated, leading to the identification of 1,6-diaryl-1H-imidazo[4,5-c]pyridin-2(3H)-one 20b as the first bifunctional agent that can target both tubulin and katanin simultaneously. The in vivo assays verified that compound 20b significantly inhibited xenograft tumor growth with good pharmacokinetic characteristics, demonstrating a promising potential for further development into anti-tumor drug candidates with a unique mechanism of dual-targeting microtubule.

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.

Simplified LC-MS/MS method for quantification of IG-105, a novel tubulin ligand, and its application to the pharmacokinetic study in rats at the anticancer effective dose.

IG-105, N-(2, 6-dimethoxypyridine-3-yl)-9-methylcarbazole-3-sulfonamide, a novel carbazole sulfonamide, shows a potent anticancer activity in a variety of human tumor cells in vitro and in vivo. In the present study, a rapid and convenient liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and applied to the pharmacokinetic study of IG-105 in rats. Chromatographic separation was accomplished on a C18 column using an isocratic mobile phase of acetonitrile-water-acetic acid (56:44:0.2, v/v/v). The ion transitions of IG-105 and combretastatin A4 (internal standard) in selected reaction monitoring mode were m/z 398→154 and m/z 317→286, respectively. The assay exhibited good linearity over the range of 2-512 ng/mL. Intra- and inter-day precisions were within 8.2 %, and the accuracies ranged from -6.0 to 3.7 %. The extraction recoveries were higher than 90 %, and the matrix effects were negligible. All quality control samples were stable at different storage conditions. The validated LC-MS/MS method was successfully applied to a preclinical pharmacokinetic study of IG-105 in rats after a single oral dose of 100, 250, or 1000 mg/kg which showed tumor growth inhibition activity. The absorption of IG-105 was proved to be rapid but saturated to a certain extent into the blood circulation, from where it was distributed and eliminated gradually.

Identification of the Metabolic Profile of the α-Tubulin-Binding Natural Product (-)-Pironetin.

Pironetin, the only crystallographically confirmed natural product to target α-tubulin, displays potent cytotoxic activity against sensitive and resistant A2780 ovarian cancer cell lines but is only marginally active in vivo. We now report that pironetin has a short half-life (<7 min) in human liver microsomes, suggesting that its limited in vivo efficacy is due to rapid metabolism. Further, we describe the discovery of epoxypironetin as pironetin's major metabolite in human liver microsomes.

Synthesis, molecular properties prediction and biological evaluation of indole-vinyl sulfone derivatives as novel tubulin polymerization inhibitors targeting the colchicine binding site.

Twenty-two novel indole-vinyl sulfone derivatives were designed, synthesized and evaluated as tubulin polymerization inhibitors. The physicochemical and drug-likeness properties of all target compounds were predicted by Osiris calculations. All compounds were evaluated for their antiproliferative activities, among them, compound 7f exhibited the most potent activity against a panel of cancer cell lines, which was 2-7 folds more potent than our previously reported compound 4. Especially, 7f displayed about 8-fold improvement of selective index as compared with compound 4, indicating that 7f might have lower toxicity. Besides, 7f inhibited the microtubule polymerization by binding to the colchicine site of tubulin. Further investigations showed that compound 7f effectively disrupted microtubule network, caused cell cycle arrest at G2/M phase and induced cell apoptosis in K562 cells. Moreover, 7f reduced the cell migration and disrupted capillary-like tube formation in HUVEC cells. Importantly, the in vivo anti-tumor activity of 7f was validated in H22 liver cancer xenograft mouse model without apparent toxicity, suggesting that 7f is a promising anti-tubulin agent for cancer therapy.

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.

Preclinical Pharmacokinetics of C118P, a Novel Prodrug of Microtubules Inhibitor and Its Metabolite C118 in Mice, Rats, and Dogs.

C118P, a phosphate prodrug of C118, which is a novel microtubule protein inhibitor, is currently under Phase I clinical development in China for treating ovarian cancer and lung cancer. The preclinical pharmacokinetics of prodrug C118P and its metabolite C118 were extensively characterized in vivo in mice, rats, and dogs and in vitro to support the further development of C118P. The preclinical tissue distribution and excretion were investigated in rats. Plasma protein binding in mice, rat, and human, and hepatic microsomal metabolic stability in mice, rat, dog, monkey, and human, were also evaluated. The (AUC0-inf) and C30s of C118P at 50 mg/kg in rats and 6 mg/kg in dogs, and the C2min of C118 at 6 mg/kg in dogs increased less than the dosage increase, suggested nonlinear pharmacokinetic occurred at high dose. As a prodrug, C118P can be quickly hydrolyzed into C118 after an intravenous administration. The unbound C118 in plasma is slightly higher than C118P. C118P can hardly penetrate the tissue, while C118 can distribute widely into tissues. In tumor-bearing nude mice, the concentration of C118 is high in lung, ovary, and tumor, with an extended half-life in tumor. C118P is a promising candidate prodrug for further clinical development.

(E)-N-Aryl-2-oxo-2-(3,4,5-trimethoxyphenyl)acetohydrazonoyl cyanides as tubulin polymerization inhibitors: Structure-based bioisosterism design, synthesis, biological evaluation, molecular docking and in silico ADME prediction.

A series of (E)-N-Aryl-2-oxo-2-(3,4,5-trimethoxyphenyl)acetohydrazonoyl cyanides have been synthesized and evaluated for their anticancer activity in human hepatocellular liver carcinoma HepG2 and breast adenocarcinoma MCF-7 cell lines. Among all the tested compounds, compound 3a, 3e and 3n displayed more activity than lead compound with IC50 value of 0.26-0.61 µM. Meanwhile, these compounds (3a, 3e and 3n) showed potent antiproliferative activity against a panel of cancer cells and the HCT-8/T multidrug resistant cell line with IC50 values in the range of 0.077- 7.44 µM. Flow cytometric analyses revealed that compound 3n induced cell cycle arrest in G2/M phases in a dose dependent manner. The compound 3n also displayed potent tubulin polymerization inhibition with an IC50 value of 0.9 µM, with ten folds more active than colchicine (IC50 = 9 µM). Molecular docking studies revealed that compound 3n efficiently interacted with the colchicine binding site of tubulin through hydrophobic, cation-π and hydrogen bond interaction. Furthermore, in silico pharmacokinetic prediction shown that these compounds have a good ADME-related physicochemical parameters. These results demonstrate that 3n exhibits potent cytotoxicity in cancer cells by targeting the colchicine binding site of tubulin and potentially acts as a therapeutic lead compound for the development of anticancer drugs.

Design, synthesis and biological evaluation of a novel tubulin inhibitor 7a3 targeting the colchicine binding site.

Tubulin inhibitors that target the colchicine binding site continue to emerge as promising anticancer agents. In this study, based on the anti-proliferative activities, a novel tubulin inhibitor 7a3 targeting the colchicine binding site was designed, synthesized, and optimized from a series of novel cis-restricted pyrazole analogues of combretastatin A-4. The structure-activity relationships (SARs) of these newly synthesized compounds are summarized indicating that the methyl substituent at the N1 position and deamination were significantly important for the anti-proliferative efficacy. The optimized compound 7a3 exhibited the ability to arrest the cell cycle in the G2/M phase, induce cell apoptosis, and inhibit cell migration in tumour cells. The results of the immunofluorescence analysis using confocal microscopy and the tubulin polymerization assay revealed that tubulin assembly was disrupted by 7a3 in vitro. Furthermore, the targeting identification of 7a3 was illuminated by solving the crystal structure of 7a3 in complex with tubulin at a resolution of 3.2 Š(PDB code 5Z4U), which confirmed the result of molecular docking and further demonstrated that 7a3 binds to the site of colchicine. Moreover, the pharmacokinetic analysis in mouse plasma showed that 7a3 rapidly reached a peak concentration at 0.25 h after intraperitoneal administration, and the T1/2, Cmax, and AUC0-inf were 1.67 ±â€¯0.28 h, 882 ±â€¯71 ng mL-1, and 1166 ±â€¯129 h ng·mL-1, respectively, after a single-dose administration analysed by liquid chromatography-tandem mass spectrometry (LC/MS/MS). In addition, the in vivo study indicated that 7a3 significantly inhibited the tumour growth of the SK-OV-3 xenograft in a nude mouse model. In conclusion, our study proved 7a3 to be a potential microtubule-targeting drug for cancer therapy. The SARs and mechanism of action studies of 7a3 based on the X-ray co-crystal structure provided insights into the next-generation tubulin inhibitors for cancer therapy.

Pharmacodynamic and pharmacokinetic characteristics of YMR-65, a tubulin inhibitor, in tumor-bearing mice.

YMR-65​, 5-(5-bromo-1-methyl-1H-indol-3-yl)-3-(3-methoxyphenyl)-4, 5-dihydro-1H-pyrazole-1-carboxamide, is a potential tubulin inhibitor exhibiting good anticancer activity. In our study, we illustrated the biological activities in HepG2 cells and the pharmacodynamic and pharmacokinetic profiles were evaluated in murine H22 hepatoma-bearing mice. Molecular docking assay and colchicine competition assay indicated that YMR-65 could bind tightly to the colchicine binding site of tubulin. Further investigation demonstrated that YMR-65 arrested cells in the G2/M phase of cell cycle and induced apoptosis in HepG2 cells. Compared with control group, the tumor growth inhibition determined by final relative volume of tumor/the initial tumor volume were 32.57%, 24.00% and 34.95%, respectively, for YMR-65 (10 mg/kg), YMR-65 (20 mg/kg) and CA4P (10 m/kg) groups. Besides there were no obvious body change or tissue damage (enhanced by histopathology study). YMR-65 administration at 10 and 20 mg/kg in H22 tumor-bearing mice resulted in 1.87- and 1.80-fold longer half time (t1/2) and 0.36- and 0.78-fold lower area under concentration-time curve (AUC0-∞) in plasma in contrast with normal mice at 10 mg/kg. Furthermore, YMR-65 showed a wide distribution to various tissues or tumor and the highest distribution index (the ratio of AUCtissue or tumor/AUCplasma) was found in tumor, which implied that it might accumulate in tumor after administration. In brief, our results indicated that YMR-65 was a promising candidate with high antitumor efficacy and low tissue damage.