A thalidomide analogue with in vitro antiproliferative, antimitotic, and microtubule-stabilizing activities

Pharmacological Potential of Small Molecules for Treating Corneal Neovascularization

Under healthy conditions, the cornea is an avascular structure which allows for transparency and optimal visual acuity. Its avascular nature is maintained by a balance of proangiogenic and antiangiogenic factors. An imbalance of these factors can result in abnormal blood vessel proliferation into the cornea. This corneal neovascularization (CoNV) can stem from a variety of insults including hypoxia and ocular surface inflammation caused by trauma, infection, chemical burns, and immunological diseases. CoNV threatens corneal transparency, resulting in permanent vision loss. Mainstay treatments of CoNV have partial efficacy and associated side effects, revealing the need for novel treatments. Numerous natural products and synthetic small molecules have shown potential in preclinical studies in vivo as antiangiogenic therapies for CoNV. Such small molecules include synthetic inhibitors of the vascular endothelial growth factor (VEGF) receptor and other tyrosine kinases, plus repurposed antimicrobials, as well as natural source-derived flavonoid and non-flavonoid phytochemicals, immunosuppressants, vitamins, and histone deacetylase inhibitors. They induce antiangiogenic and anti-inflammatory effects through inhibition of VEGF, NF-κB, and other growth factor receptor pathways. Here, we review the potential of small molecules, both synthetics and natural products, targeting these and other molecular mechanisms, as antiangiogenic agents in the treatment of CoNV.

Therapeutic Effects of a Novel Phenylphthalimide Analog for Corneal Neovascularization and Retinal Vascular Leakage

Purpose

Neovascularization (NV) and retinal vascular leakage are major causes of impaired vision in ocular diseases. The purpose of this study was to identify novel phenylphthalimide analogs with therapeutic effects on NV and vascular leakage and to explore the mechanism of action.

Methods

Antiangiogenic activities of novel phenylphthalimide analogs were assessed in vitro by using VEGF ELISA and endothelial cell proliferation assay. Their efficacies on retinal vascular leakage were evaluated using rat models of oxygen-induced retinopathy (OIR) and streptozotocin (STZ)-induced diabetes. The in vivo antiangiogenic activity was evaluated using topical administration in the alkali burn-induced corneal NV model. The expression of VEGF and intercellular adhesion molecule-1 (ICAM-1) were measured using ELISA.

Results

Thalidomide and three novel analogs all showed inhibitory effects on endothelial cell proliferation and VEGF expression in vitro. Through intravitreal injection, all of the compounds reduced retinal vascular leakage in the OIR and STZ-induced diabetic models. Among these compounds, (2,6-diisopropylphenyl)-5-amino-1H-isoindole-1,3-dione (DAID) displayed the most potent efficacy and reduced retinal vascular leakage in a dose-dependent manner in both the OIR and STZ-diabetes models. Topical administration of DAID also inhibited alkali burn-induced corneal NV. Furthermore, DAID attenuated the overexpression of VEGF and ICAM-1 in the retina of the OIR model. Intravitreal injection of DAID did not result in any detectable side effects, as shown by electroretinogram and retinal histological analysis.

Conclusions

DAID is a novel phenylphthalimide analog with potent effects on NV and retinal vascular leakage through downregulation of VEGF and inflammatory factors and has therapeutic potential.

Structure-Based Discovery of a Selective KDM5A Inhibitor that Exhibits Anti-Cancer Activity via Inducing Cell Cycle Arrest and Senescence in Breast Cancer Cell Lines

Breast cancer is the one of the most frequent causes of female cancer mortality. KDM5A, a histone demethylase, can increase the proliferation, metastasis, and drug resistance of cancers, including breast cancer, and is thus an important therapeutic target. In the present work, we performed hierarchical virtual screening towards the KDM5A catalytic pocket from a chemical library containing 90,000 compounds. Using multiple biochemical methods, the cyclopenta[c]chromen derivative 1 was identified as the top candidate for KDM5A demethylase inhibitory activity. Compared with the well-known KDM5 inhibitor CPI-455 (18), 1 exhibited higher potency against KDM5A and much higher selectivity for KDM5A over both KDM4A and other KDM5 family members (KDM5B and KDM5C). Additionally, compound 1 repressed the proliferation of various KDM5A-overexpressing breast cancer cell lines. Mechanistically, 1 promoted accumulation of p16 and p27 by blocking KDM5A-mediated H3K4me3 demethylation, leading to cell cycle arrest and senescence. To date, compound 1 is the first cyclopenta[c]chromen-based KDM5A inhibitor reported, and may serve as a novel motif for developing more selective and efficacious pharmacological molecules targeting KDM5A. In addition, our research provides a possible anti-cancer mechanism of KDM5A inhibitors and highlights the feasibility and significance of KDM5A as a therapeutic target for KDM5A-overexpressing breast cancer.

Recent advances in discovery and development of natural products as source for anti-Parkinson's disease lead compounds

Parkinson's disease (PD) is a common chronic degenerative disease of the central nervous system. Although the cause remains unknown, several pathological processes and central factors such as oxidative stress, mitochondrial injury, inflammatory reactions, abnormal deposition of α-synuclein, and cell apoptosis have been reported. Currently, anti-PD drugs are classified into two major groups: drugs that affect dopaminergic neurons and anti-cholinergic drugs. Unfortunately, the existing conventional strategies against PD are with numerous side effects, and cannot fundamentally improve the degenerative process of dopaminergic neurons. Therefore, novel therapeutic approaches which have a novel structure, high efficiency, and fewer side effects are needed. For many years, natural products have provided an efficient resource for the discovery of potential therapeutic agents. Among them, many natural products possess anti-PD properties as a result of not only their wellrecognized anti-oxidative and anti-inflammatory activities but also their inhibitory roles regarding protein misfolding and the regulatory effects of PD related pathways. Indeed, with the steady improvement in the technologies for the isolation and purification of natural products and the in-depth studies on the pathogenic mechanisms of PD, many monomer components of natural products that have anti-PD effects have been gradually discovered. In this article, we reviewed the research status of 37 natural products that have been discovered to have significant anti-PD effects as well as their mode of action. Overall, this review may guide the design of novel therapeutic drugs in PD.

Embryonic vascular disruption adverse outcomes: Linking high throughput signaling signatures with functional consequences

Embryonic vascular disruption is an important adverse outcome pathway (AOP) as chemical disruption of cardiovascular development induces broad prenatal defects. High throughput screening (HTS) assays aid AOP development although linking in vitro data to in vivo apical endpoints remains challenging. This study evaluated two anti-angiogenic agents, 5HPP-33 and TNP-470, across the ToxCastDB HTS assay platform and anchored the results to complex in vitro functional assays: the rat aortic explant assay (AEA), rat whole embryo culture (WEC), and the zebrafish embryotoxicity (ZET) assay. Both were identified as putative vascular disruptive compounds (pVDCs) in ToxCastDB and disrupted angiogenesis and embryogenesis in the functional assays. Differences were observed in potency and adverse effects: 5HPP-33 was embryolethal (WEC and ZET); TNP-470 produced caudal defects at lower concentrations. This study demonstrates how a tiered approach using HTS signatures and complex functional in vitro assays might be used to prioritize further in vivo developmental toxicity testing.

Thalidomide (5HPP-33) suppresses microtubule dynamics and depolymerizes the microtubule network by binding at the vinblastine binding site on tubulin

Thalidomides were initially thought to be broad-range drugs specifically for curing insomnia and relieving morning sickness in pregnant women. However, its use was discontinued because of a major drawback of causing teratogenicity. In this study, we found that a thalidomide derivative, 5-hydroxy-2-(2,6-diisopropylphenyl)-1H-isoindole-1,3-dione (5HPP-33), inhibited the proliferation of MCF-7 with a half-maximal inhibitory concentration of 4.5 ± 0.4 μM. 5HPP-33 depolymerized microtubules and inhibited the reassembly of cold-depolymerized microtubules in MCF-7 cells. Using time-lapse imaging, the effect of 5HPP-33 on the dynamics of individual microtubules in live MCF-7 cells was analyzed. 5HPP-33 (5 μM) decreased the rates of growth and shortening excursions by 34 and 33%, respectively, and increased the time microtubules spent in the pause state by 92% as compared to that of the vehicle-treated MCF-7 cells. 5HPP-33 (5 μM) reduced the dynamicity of microtubules by 62% compared to the control. 5HPP-33 treatment reduced the distance between the two poles of a bipolar spindle, induced multipolarity in some of the treated cells, and blocked cells at mitosis. In vitro, 5HPP-33 bound to tubulin with a weak affinity. Vinblastine inhibited the binding of 5HPP-33 to tubulin, and 5HPP-33 inhibited the binding of BODIPY FL-vinblastine to tubulin. Further, a molecular docking analysis suggested that 5HPP-33 shares its binding site on tubulin with vinblastine. The results provided significant insight into the antimitotic mechanism of action of 5HPP-33 and also suggest a possible mechanism for the teratogenicity of thalidomides.

Microtubule-targeting agents augment the toxicity of DNA-damaging agents by disrupting intracellular trafficking of DNA repair proteins

The paradigm that microtubule-targeting agents (MTAs) cause cell death via mitotic arrest applies to rapidly dividing cells but cannot explain MTA activity in slowly growing human cancers. Many preferred cancer regimens combine a MTA with a DNA-damaging agent (DDA). We hypothesized that MTAs synergize with DDAs by interfering with trafficking of DNA repair proteins on interphase microtubules. We investigated nine proteins involved in DNA repair: ATM, ATR, DNA-PK, Rad50, Mre11, p95/NBS1, p53, 53BP1, and p63. The proteins were sequestered in the cytoplasm by vincristine and paclitaxel but not by an aurora kinase inhibitor, colocalized with tubulin by confocal microscopy and coimmunoprecipitated with the microtubule motor dynein. Furthermore, adding MTAs to radiation, doxorubicin, or etoposide led to more sustained γ-H2AX levels. We conclude DNA damage-repair proteins traffic on microtubules and addition of MTAs sequesters them in the cytoplasm, explaining why MTA/DDA combinations are common anticancer regimens.

Microtubule-stabilizing agents as potential therapeutics for neurodegenerative disease

Microtubules (MTs), cytoskeletal elements found in all mammalian cells, play a significant role in cell structure and in cell division. They are especially critical in the proper functioning of post-mitotic central nervous system neurons, where MTs serve as the structures on which key cellular constituents are trafficked in axonal projections. MTs are stabilized in axons by the MT-associated protein tau, and in several neurodegenerative diseases, including Alzheimer's disease, frontotemporal lobar degeneration, and Parkinson's disease, tau function appears to be compromised due to the protein dissociating from MTs and depositing into insoluble inclusions referred to as neurofibrillary tangles. This loss of tau function is believed to result in alterations of MT structure and function, resulting in aberrant axonal transport that likely contributes to the neurodegenerative process. There is also evidence of axonal transport deficiencies in other neurodegenerative diseases, including amyotrophic lateral sclerosis and Huntington's disease, which may result, at least in part, from MT alterations. Accordingly, a possible therapeutic strategy for such neurodegenerative conditions is to treat with MT-stabilizing agents, such as those that have been used in the treatment of cancer. Here, we review evidence of axonal transport and MT deficiencies in a number of neurodegenerative diseases, and summarize the various classes of known MT-stabilizing agents. Finally, we highlight the growing evidence that small molecule MT-stabilizing agents provide benefit in animal models of neurodegenerative disease and discuss the desired features of such molecules for the treatment of these central nervous system disorders.

Brain-penetrant, orally bioavailable microtubule-stabilizing small molecules are potential candidate therapeutics for Alzheimer's disease and related tauopathies

Microtubule (MT) stabilizing drugs hold promise as potential treatments for Alzheimer’s disease (AD) and related tauopathies. However, thus far epothilone D has been the only brain-penetrant MT-stabilizer to be evaluated in tau transgenic mice and in AD patients. Furthermore, this natural product exhibits potential deficiencies as a drug candidate, including an intravenous route of administration and the inhibition of the P-glycoprotein (Pgp) transporter. Thus, the identification of alternative CNS-active MT-stabilizing agents that lack these potential limitations is of interest. Toward this objective, we have evaluated representative compounds from known classes of non-naturally occurring MT-stabilizing small molecules. This led to the identification of selected triazolopyrimidines and phenylpyrimidines that are orally bioavailable and brain-penetrant without disruption of Pgp function. Pharmacodynamic studies confirmed that representative compounds from these series enhance MT-stabilization in the brains of wild-type mice. Thus, these classes of MT-stabilizers hold promise for the development of orally active, CNS-directed MT-stabilizing therapies.

Activities of 2-phthalimidethanol and 2-phthalimidethyl nitrate, phthalimide analogs devoid of the glutarimide moiety, in experimental models of inflammatory pain and edema

The reintroduction of thalidomide in the pharmacotherapy greatly stimulated the interest in the synthesis and pharmacological evaluation of phthalimide analogs with new and improved activities and also greater safety. In the present study, we evaluated the activities of two phthalimide analogs devoid of the glutarimide ring, namely 2-phthalimidethanol (PTD-OH) and 2-phthalimidethyl nitrate (PTD-NO), in experimental models of inflammatory pain and edema in male C57BL/6J mice. Intraplantar (i.pl.) injection of carrageenan (300 μg) induced mechanical allodynia and this response was inhibited by previous per os (p.o.) administration of PTD-OH and PTD-NO (750 mg/kg) and also by thalidomide (500 or 750 mg/kg). The edema induced by carrageenan was also inhibited by previous p.o. administration of PTD-OH (500 and 750 mg/kg) and PTD-NO (125, 250, 500 or 750 mg/kg), but not by thalidomide. Carrageenan increased tumor necrosis factor (TNF)-α and CXCL1 concentrations and also the number of neutrophils in the paw tissue. Previous p.o. administration of PTD-NO (500 mg/kg) reduced all the parameters, while PTD-OH (500 mg/kg) reduced only the accumulation of neutrophils. Thalidomide, on the other hand, was devoid of effect on these biochemical parameters. Plasma concentrations of nitrite were increased after p.o. administration of the phthalimide analog coupled to a NO donor, PTD-NO (500 mg/kg), but not after administration of PTD-OH or thalidomide. In conclusion, our results show that small molecules, structurally much simpler than thalidomide or many of its analogs under investigation, exhibit similar activities in experimental models of pain and inflammation. Finally, as there is evidence that the glutarimide moiety contributes to the teratogenic effect of many thalidomide analogs, our results indicate that phthalimide analogs devoid of this functional group could represent a new class of analgesic and anti-inflammatory candidates with potential greater safety.

Mechanism of immunomodulatory drugs' action in the treatment of multiple myeloma

Although immunomodulatory drugs (IMiDs), such as thalidomide, lenalidomide, and pomalidomide, are widely used in the treatment of multiple myeloma (MM), the molecular mechanism of IMiDs' action is largely unknown. In this review, we will summarize recent advances in the application of IMiDs in MM cancer treatment as well as their effects on immunomodulatory activities, anti-angiogenic activities, intervention of cell surface adhesion molecules between myeloma cells and bone marrow stromal cells, anti-inflammatory activities, anti-proliferation, pro-apoptotic effects, cell cycle arrest, and inhibition of cell migration and metastasis. In addition, the potential IMiDs' target protein, IMiDs' target protein's functional role, and the potential molecular mechanisms of IMiDs resistance will be discussed. We wish, by presentation of our naive discussion, that this review article will facilitate further investigation in these fields.

Optimization of 4-(N-cycloamino)phenylquinazolines as a novel class of tubulin-polymerization inhibitors targeting the colchicine site

The 6-methoxy-1,2,3,4-tetrahydroquinoline moiety in prior leads 2-chloro- and 2-methyl-4-(6-methoxy-3,4-dihydroquinolin-1(2H)-yl)quinazoline (1a and 1b) was modified to produce 4-(N-cycloamino)quinazolines (4a-c and 5a-m). The new compounds were evaluated in cytotoxicity and tubulin inhibition assays, resulting in the discovery of new tubulin-polymerization inhibitors. 7-Methoxy-4-(2-methylquinazolin-4-yl)-3,4-dihydroquinoxalin- 2(1H)-one (5f), the most potent compound, exhibited high in vitro cytotoxic activity (GI50 1.9-3.2 nM), significant potency against tubulin assembly (IC50 0.77 μM), and substantial inhibition of colchicine binding (99% at 5 μM). In mechanism studies, 5f caused cell arrest in G2/M phase, disrupted microtubule formation, and competed mostly at the colchicine site on tubulin. Compound 5f and N-methylated analogue 5g were evaluated in nude mouse MCF7 xenograft models to validate their antitumor activity. Compound 5g displayed significant in vivo activity (tumor inhibitory rate 51%) at a dose of 4 mg/kg without obvious toxicity, whereas 5f unexpectedly resulted in toxicity and death at the same dose.

Structure-activity relationship studies of thalidomide analogs with a taxol-like mode of action

Anti-microtubule agents such as paclitaxel and docetaxel have played an important role in the treatment of cancer for many years. Recently, a small molecule that has a taxol-like mode of action (5HPP-33) was reported. Herein, the detailed structure-activity relationship (SAR) studies of 5HPP-33 analogs that are substituted at the isoindole and phenyl rings are described. Bulky substitutions (such as di-isopropyl groups) on the phenyl ring result in the isoindole and phenyl rings being perpendicular to each other. It was found that this conformation is critical for anti-microtubule activity. These studies have provided valuable information, which will be helpful in the design of more potent analogs.

A computational model predicting disruption of blood vessel development

Vascular development is a complex process regulated by dynamic biological networks that vary in topology and state across different tissues and developmental stages. Signals regulating de novo blood vessel formation (vasculogenesis) and remodeling (angiogenesis) come from a variety of biological pathways linked to endothelial cell (EC) behavior, extracellular matrix (ECM) remodeling and the local generation of chemokines and growth factors. Simulating these interactions at a systems level requires sufficient biological detail about the relevant molecular pathways and associated cellular behaviors, and tractable computational models that offset mathematical and biological complexity. Here, we describe a novel multicellular agent-based model of vasculogenesis using the CompuCell3D (http://www.compucell3d.org/) modeling environment supplemented with semi-automatic knowledgebase creation. The model incorporates vascular endothelial growth factor signals, pro- and anti-angiogenic inflammatory chemokine signals, and the plasminogen activating system of enzymes and proteases linked to ECM interactions, to simulate nascent EC organization, growth and remodeling. The model was shown to recapitulate stereotypical capillary plexus formation and structural emergence of non-coded cellular behaviors, such as a heterologous bridging phenomenon linking endothelial tip cells together during formation of polygonal endothelial cords. Molecular targets in the computational model were mapped to signatures of vascular disruption derived from in vitro chemical profiling using the EPA's ToxCast high-throughput screening (HTS) dataset. Simulating the HTS data with the cell-agent based model of vascular development predicted adverse effects of a reference anti-angiogenic thalidomide analog, 5HPP-33, on in vitro angiogenesis with respect to both concentration-response and morphological consequences. These findings support the utility of cell agent-based models for simulating a morphogenetic series of events and for the first time demonstrate the applicability of these models for predictive toxicology.

Microtubule stabilizing agents as potential treatment for Alzheimer's disease and related neurodegenerative tauopathies

The microtubule (MT) associated protein tau, which is highly expressed in the axons of neurons, is an endogenous MT-stabilizing agent that plays an important role in axonal transport. Loss of MT-stabilizing tau function, caused by misfolding, hyperphosphorylation, and sequestration of tau into insoluble aggregates, leads to axonal transport deficits with neuropathological consequences. Several in vitro and preclinical in vivo studies have shown that MT-stabilizing drugs can be utilized to compensate for the loss of tau function and to maintain/restore effective axonal transport. These findings indicate that MT-stabilizing compounds hold considerable promise for the treatment of Alzheimer disease and related tauopathies. The present article provides a synopsis of the key findings demonstrating the therapeutic potential of MT-stabilizing drugs in the context of neurodegenerative tauopathies, as well as an overview of the different classes of MT-stabilizing compounds.

Evaluation of antiproliferative effect of N-(alkyladamantyl)phthalimides in vitro

A series of (1-adamantyl)phthalimides, 1-4, and (2-adamantyl)phthalimides, 5-8, characterized by different chain length between the adamantyl and the phthalimide moiety were synthesized, as well as 1- and 2-adamantylphthalimides substituted by nitro 9, 10, and amino group 11, 12, and phthalimides bearing homoadamantyl 13 and protoadamantyl substituent 14 and 15. The compounds were tested for antiproliferative activity in vitro on a series of five human cancer lines: MCF-7 (breast carcinoma), SW 620 (colon carcinoma), HCT 116 (colon carcinoma), MOLT-4 (acute lymphoblastic leukemia), H 460 (lung carcinoma), and a non-tumor cell line HaCaT (human keratinocytes). All compounds except nitro derivatives 9 and 10 exhibited antiproliferative activity. The activity was generally better in the 2-adamantyl series 5-8 and in the compounds having the longest alkyl spacers as in 4 and 8, or with an amino group as in 9 and 10. The most active compounds with the propylene spacer 4 and 8 showed the highest selectivity toward tumor cells. The activity was found to be due to a delay in the progress through the cell cycle at G1/S phase.

Identification of Simple Compounds with Microtubule-Binding Activity That Inhibit Cancer Cell Growth with High Potency

We analyzed more than 1 million small molecules with the goal of finding simple synthetic compounds that potently inhibit cancer cell growth. We identified three such compounds with unknown mechanisms of action. Subsequent studies revealed that all three of these small molecules target microtubules. These three scaffolds can serve as templates for developing new microtubule-targeted agents, overcoming the limits of existing microtubule-inhibiting drugs derived from complex natural products.

What tubulin drugs tell us about microtubule structure and dynamics

A wide range of small molecules, including alkaloids, macrolides and peptides, bind to tubulin and disturb microtubule assembly dynamics. Some agents inhibit assembly, others inhibit disassembly. The binding sites of drugs that stabilize microtubules are discussed in relation to the properties of microtubule associated proteins. The activities of assembly inhibitors are discussed in relation to different nucleotide states of tubulin family protein structures.

Polyunsaturated fatty acids synergize with lipid droplet binding thalidomide analogs to induce oxidative stress in cancer cells

Background

Cytoplasmic lipid-droplets are common inclusions of eukaryotic cells. Lipid-droplet binding thalidomide analogs (2,6-dialkylphenyl-4/5-amino-substituted-5,6,7-trifluorophthalimides) with potent anticancer activities were synthesized.

Results

Cytotoxicity was detected in different cell lines including melanoma, leukemia, hepatocellular carcinoma, glioblastoma at micromolar concentrations. The synthesized analogs are non-toxic to adult animals up to 1 g/kg but are teratogenic to zebrafish embryos at micromolar concentrations with defects in the developing muscle. Treatment of tumor cells resulted in calcium release from the endoplasmic reticulum (ER), induction of reactive oxygen species (ROS), ER stress and cell death. Antioxidants could partially, while an intracellular calcium chelator almost completely diminish ROS production. Exogenous docosahexaenoic acid or eicosapentaenoic acid induced calcium release and ROS generation, and synergized with the analogs in vitro, while oleic acid had no such an effect. Gene expression analysis confirmed the induction of ER stress-mediated apoptosis pathway components, such as GADD153, ATF3, Luman/CREB3 and the ER-associated degradation-related HERPUD1 genes. Tumor suppressors, P53, LATS2 and ING3 were also up-regulated in various cell lines after drug treatment. Amino-phthalimides down-regulated the expression of CCL2, which is implicated in tumor metastasis and angiogenesis.

Conclusions

Because of the anticancer, anti-angiogenic action and the wide range of applicability of the immunomodulatory drugs, including thalidomide analogs, lipid droplet-binding members of this family could represent a new class of agents by affecting ER-membrane integrity and perturbations of ER homeostasis.

TTI-237: a novel microtubule-active compound with in vivo antitumor activity

5-Chloro-6-[2,6-difluoro-4-[3-(methylamino)propoxy]phenyl]-N-[(1S)-2,2,2-trifluoro-1-methylethyl]-[1,2,4]triazolo[1,5-a]pyrimidin-7-amine butanedioate (TTI-237) is a microtubule-active compound of novel structure and function. Structurally, it is one of a class of compounds, triazolo[1,5a]pyrimidines, previously not known to bind to tubulin. Functionally, TTI-237 inhibited the binding of [(3)H]vinblastine to tubulin, but it caused a marked increase in turbidity development that more closely resembled the effect observed with docetaxel than that observed with vincristine. The morphologic character of the presumptive polymer is unknown at present. When applied to cultured human tumor cells at concentrations near its IC(50) value for cytotoxicity (34 nmol/L), TTI-237 induced multiple spindle poles and multinuclear cells, as did paclitaxel, but not vincristine or colchicine. Flow cytometry experiments revealed that, at low concentrations (20-40 nmol/L), TTI-237 produced sub-G(1) nuclei and, at concentrations above 50 nmol/L, it caused a strong G(2)-M block. The compound was a weak substrate of multidrug resistance 1 (multidrug resistance transporter or P-glycoprotein). In a cell line expressing a high level of P-glycoprotein, the IC(50) of TTI-237 increased 25-fold whereas those of paclitaxel and vincristine increased 806-fold and 925-fold, respectively. TTI-237 was not recognized by the MRP or MXR transporters. TTI-237 was active in vivo in several nude mouse xenograft models of human cancer, including LoVo human colon carcinoma and U87-MG human glioblastoma, when dosed i.v. or p.o. Thus, TTI-237 has a set of properties that distinguish it from other classes of microtubule-active compounds.

Inhibitors of NF-κB derived from thalidomide

A series of compounds originally derived from thalidomide were synthesized and evaluated. The most potent compounds in this series, 5HPP-33 and compound 20, inhibited NF-kappaB activation in HeLa cells. Preliminary study indicated that the mechanism of inhibition of NF-kappaB activation is through inhibition of its translocation from the cytoplasm to the nucleus.

Development of Tubulin-Polymerization Inhibitors Based on the Thalidomide Skeleton

We synthesized a series of compounds based on the potent tubulin-polymerization inhibitor 5-hydroxy-2-(2,6-diisopropylphenyl)-1H-isoindole-1,3-dione [5HPP-33 (3)], which is structurally derived from thalidomide (1), and investigated their inhibitory effects on tubulin polymerization. Direct interaction between 5HPP-33 (3) and alpha,beta-tubulin heterodimer protein was demonstrated by means of a surface plasmon resonance study.