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An approach to the validation of a linker strategy for the epothilone family of microtubule-stabilizing agents is reported. An analogue of epothilone B in which the C(6) methyl group has been replaced with a 4-azidobutyl group has been prepared by total chemical synthesis, and amides derived from the azido group have been shown to retain the activity of the parent compound. These results set the stage for an evaluation of the potential of the epothilones to serve as the drug component of antibody-drug conjugates and other selective tumor cell-targeting conjugates.

Scar formation after spinal cord injury is regarded as an obstacle to axonal regeneration and functional recovery. Epothilone B provides moderate microtubule stabilization and is mainly used for anti-tumor therapy. It also reduces scar tissue formation and promotes axonal regeneration after spinal cord injury. The aim of the present study was to investigate the effect and mechanism of the microtubule-stabilizing reagent epothilone B in decreasing fibrotic scarring through its action on pericytes after spinal cord injury. A rat model of spinal cord injury was established via dorsal complete transection at the T10 vertebra. The rats received an intraperitoneal injection of epothilone B (0.75 mg/kg) at 1 and 15 days post-injury in the epothilone B group or normal saline in the vehicle group. Neuron-glial antigen 2, platelet-derived growth factor receptor β, and fibronectin protein expression were dramatically lower in the epothilone B group than in the vehicle group, but β-tubulin protein expression was greater. Glial fibrillary acidic protein at the injury site was not affected by epothilone B treatment. The Basso, Beattie, and Bresnahan locomotor scores were significantly higher in the epothilone B group than in the vehicle group. The results of this study demonstrated that epothilone B reduced the number of pericytes, inhibited extracellular matrix formation, and suppressed scar formation after spinal cord injury.

Microtubules play critical roles in regulating the activation of NLRP3 inflammasome and microtubule-destabilizing agents such as colchicine have been shown to suppress the activation of this inflammasome. However, it remains largely unknown whether paclitaxel, a microtubule-stabilizing agent being used in cancer therapy, has any influences on NLRP3 inflammasome activation. Here we showed that paclitaxel pre-treatment greatly enhanced ATP- or nigericin-induced NLRP3 inflammasome activation as indicated by increased release of cleaved caspase-1 and mature IL-1β, enhanced formation of ASC speck, and increased gasdermin D cleavage and pyroptosis. Paclitaxel time- and dose-dependently induced α-tubulin acetylation in LPS-primed murine and human macrophages and further increased ATP- or nigericin-induced α-tubulin acetylation. Such increased α-tubulin acetylation was significantly suppressed either by resveratrol or NAD+ (coenzyme required for deacetylase activity of SIRT2), or by genetic knockdown of MEC-17 (gene encoding α-tubulin acetyltransferase 1). Concurrently, the paclitaxel-mediated enhancement of NLRP3 inflammasome activation was significantly suppressed by resveratrol, NAD+, or MEC-17 knockdown, indicating the involvement of paclitaxel-induced α-tubulin acetylation in the augmentation of NLRP3 inflammasome activation. Similar to paclitaxel, epothilone B that is another microtubule-stabilizing agent also induced α-tubulin acetylation and increased NLRP3 inflammasome activation in macrophages in response to ATP treatment. Consistent with the in vitro results, intraperitoneal administration of paclitaxel significantly increased serum IL-1β levels, reduced bacterial burden, dampened infiltration of inflammatory cells in the liver, and improved animal survival in a mouse model of bacterial infection. Collectively, our data indicate that paclitaxel potentiated NLRP3 inflammasome activation by inducing α-tubulin acetylation and thereby conferred enhanced antibacterial innate responses, suggesting its potential application against pathogenic infections beyond its use as a chemotherapeutic agent.

We showed the use of the experimental chemical hardness in the analysis of the interaction between β-tubulin and epothilone B. The interaction is analyzed by exposing the Epothilone B to a sensor based on an organic self-assembled monolayer functionalized with Beta tubulin. The proposed methodology is nondestructive and label-free. It allows us to compare the interaction between Beta-tubulin and different concentrations of the pharmacological molecule, i.e., epothilone B. The interaction is analyzed by the experimental hardness obtained according to the Miranda-Bueno methodology. We observed a linear behavior between the logarithm of the chemical hardness and the logarithm of epothilone B concentration. The results suggest the experimental chemical hardness can be used to compare the interaction of β-tubulin with epothilone B and with other pharmacological molecules.

Epothilones are a class of 16-membered macrolide compounds targeting microtubules. They have good anticancer activity and their mechanism of action is similar to that of paclitaxel. Epothilones are also highly active against cancer cells that are resistant to paclitaxel and other anticancer drugs. They have good water solubility, simple structure, and are relatively easy to totally synthesize and or semi-synthesize. These results immediately attracted great interest and research enthusiasm from pharmaceutical companies and academia. Herein, the various synthetic methods of epothilone B and its anticancer activity were summarized and analyzed.

Background Many previous clinical studies have demonstrated that the nigrostriatal pathway, which plays a vital role in movement adjustment, is significantly impaired after stroke, according to medical imaging and autopsies. However, the basic pathomorphological changes have been poorly investigated to date. This study was designed to explore the pathomorphological changes, mechanism, and therapeutic method of nigrostriatal impairment after intracerebral hemorrhage ( ICH ). Methods and Results Intrastriatal injection of autologous blood or microtubule depolymerization reagent nocodazole was performed to mimic the pathology of ICH in C57/ BL 6 mice. Immunofluorescence, Western blotting, electron microscopy, functional behavioral tests, and anterograde and retrograde neural circuit tracking techniques were used in these mice. The data showed that the number of dopamine neurons and the dopamine concentration were severely decreased and that fine motor function was impaired after ICH . Microtubule depolymerization was the main contributor to the loss of dopamine neurons and to motor function deficits after ICH , as was also proven by intrastriatal injection of nocodazole. Moreover, administration of the microtubule stabilizer epothilone B (1.5 mg/kg) improved the integrity of the nigrostriatal pathway neural circuit, increased the number of dopamine neurons (4598±896 versus 3125±355; P =0.034) and the dopamine concentration (4.28±0.99 versus 3.08±0.75 ng/mg; P =0.041), and enhanced fine motor functional recovery associated with increased acetylated α‐tubulin expression to maintain microtubule stabilization after ICH . Conclusions Our results clarified the pathomorphological changes of the nigrostriatal pathway after ICH and found that epothilone B helped alleviate nigrostriatal pathway injury after ICH , associated with promoting α‐tubulin acetylation to maintain microtubule stabilization, thus facilitating motor recovery.

The structural information of small therapeutic compounds complexed in biological matrices is important for drug developments. However, structural studies on ligands bound to such a large and dynamic system as microtubules are still challenging. This article reports an application of the solid-state NMR technique to investigating the bioactive conformation of epothilone B, a microtubule stabilizing agent, whose analog ixabepilone was approved by the U.S. Food and Drug Administration (FDA) as an anticancer drug. First, an analog of epothilone B was designed and successfully synthesized with deuterium and fluorine labels while keeping the high potency of the drug; Second, a lyophilization protocol was developed to enhance the low sensitivity of solid-state NMR; Third, molecular dynamics information of microtubule-bound epothilone B was revealed by high-resolution NMR spectra in comparison to the non-bound epothilone B; Last, information for the macrolide conformation of microtubule-bound epothilone B was obtained from rotational-echo double-resonance (REDOR) NMR data, suggesting the X-ray crystal structure of the ligand in the P450epoK complex as a possible candidate for the conformation. Our results are important as the first demonstration of using REDOR for studying epothilones.

The epothilones, including epothilones B and D, are macrocyclic lactones, which have potent cytotoxicities and promote the polymerization of tubulin to mictotubules by binding to and stabilizing the tubulin polymer. They have a very similar mechanism of action to paclitaxel (Taxol®). The determination of the microtubule-binding conformation of the epothilones is an important piece of information in designing improved analogs for possible clinical use, and internuclear distance information that will assist the determination of this conformation can be obtained by rotational echo double resonance (REDOR) NMR studies of microtubule-bound epothilones with appropriate stable isotope labels. Analogs of epothilone B and epothilone D with [(2) H3 ] and [(19) F] labels were prepared from an advanced precursor for potential use in REDOR NMR studies to determine internuclear distances in tubulin-bound ligand.

We describe our successful efforts for the translation of our research strategy that was focused on a broad structural modification of the natural product epothilone B, to the production of the distinct drug candidate sagopilone in a kg scale. By a direct comparison of the research and development procedures we address some important aspects to be considered for an up-scaling process. 1 Introduction and Concept 2 Preparation of Building Block A 2.1 Research Sequence A1––A3–A4–A5–A6–A7–A8–A9– A10–(A12–)A13 2.2 Development Sequence A11–A12–A13 3 Preparation of Building Block B 3.1 Research Sequence B1–B2–B3–B4–(B6–B7)–B9–B10 3.2 Development Sequence B1–B2–B3–B4–B5–B8–B10 4 Preparation of Building Block C 4.1 Research Sequence C1–C2–C3–C4–C6–C7–C9–C10–C11–C12 4.2 Development Sequence C1–C2–C5–C8–C9–C10–C11–C12 5 Preparation of Building Block BC 5.1 Research 5.2 Development 6 Preparation of the Final Sequence ABC 6.1 Research 6.2 Development 7 Summary

The anticancer compound epothilone B is biosynthesized by the myxobacteriumSorangium cellulosum; however, the fermentation characteristics for epothilone production in Sorangium cellulosum have not yet been reported. In this study, medium components for the production of epothilone B in the So0157-2 strain of S. cellulosum were statistically screened and optimized. First, the nutrients in the fermentation medium were optimized in one-factor-at-a-time, Plackett–Burman design, and Box–Behnken design experiments. Afterwards, three nutritional parameters were selected for the optimization of epothilone B production in shaking flask cultures using a central composite response surface methodology design; a polynomial equation model that related the medium components and epothilone B yield was established. The data were further analyzed using response surface plots and canonical mathematical model analyses with the SAS 8.0 software. After optimized, the yield of epothilone B increased to 82.0 ± 3 mg/l, 7.2-fold higher than the initial yield (11.3 ± 0.4 mg/l). Key words: Myxobacterium, Sorangium cellulosum, epothilone B, statistical optimization, response surface methodology.

Solid evidence: Induction of the polymerization of β-tubulin dimers into microtubules by epothilones, such as patupilone, by an as yet unknown mechanism leads to the apoptosis of cancer cells. Solid-state NMR spectroscopy of patupilone bound to microtubules has now enabled the identification of atomic positions of the drug that undergo clear chemical-shift changes upon binding (see correlation spectra of free (black) and complexed patupilone (red)).

Background. The epothilones are a new class of microtubule-stabilizing drugs that exert potent antitumor activity against taxane-resistant and multidrug resistant cell lines. The most clinically advanced member of this class is the semisynthetic epothilone B derivative ixabepilone. Purpose. This article reviews the preclinical and clinical data on ixabepilone in patients with locally advanced and metastatic breast cancer (MBC) and provides guidance for pharmacists on its optimal use. Data sources. PubMed and conference proceedings through August 2008. Results. In preclinical studies, ixabepilone has demonstrated potent antitumor activity and low susceptibility to mechanisms that confer tumor resistance. Clinically meaningful benefits have been achieved with ixabepilone monotherapy in phase 2 trials of patients with MBC who have failed previous chemotherapies (anthracyclines, taxanes, or capecitabine). In a randomized, phase 3 trial, the combination of ixabepilone and capecitabine proved more effective than capecitabine alone after the failure of taxane and anthracycline regimens. At the recommended dose and schedule, the therapeutic ratio of ixabepilone is generally favorable, and its adverse effects (notably neutropenia and peripheral neuropathy) are generally manageable and reversible. Conclusion. Ixabepilone represents an advance in the treatment of anthracycline - and taxane-pretreated MBC. Future studies will define its efficacy in combination with other drugs used in the treatment of MBC, as well as in other types of cancer. J Oncol Pharm Practice (2009) 15: 95—106.

A systematic comparison has been performed of the morphology and stability of microtubules (MTs) induced by the potent microtubule-stabilizing agents (MSAs) taxol, epothilone B (Epo B), and discodermolide (DDM) under GTP-free conditions. DDM-induced tubulin polymerization occurred significantly faster than that induced by taxol and Epo B. At the same time, tubulin polymers assembled from soluble tubulin by DDM were morphologically distinct (shorter and less ordered) from those induced by either taxol or Epo B, as demonstrated by electron microscopy. Exposure of MSA-induced tubulin polymers to ultrasound revealed the DDM-based polymers to be less stable to this type of physical stress than those formed with either Epo B or taxol. Interestingly, MT assembly in the presence of both DDM and taxol appeared to produce a distinct new type of MT polymer with a mixed morphology between those of DDM- and taxol-induced structures. The observed differences in MT morphology and stability might be related, at least partly, to differences in intramicrotubular tubulin isotype distribution, as DDM showed a different pattern of beta-tubulin isotype usage in the assembly process.

A cation exchange resin was added at different stages in the growth of Sorangium cellulosum cultures to remove excess ammonium, which has a negative influence on the production of the anticancer agent, epothilone. When 8 g L −1 of cation exchange resin were added at the mid-death phase, the ammonium removal reached 83% and the maximum production of epothilone was 14.3 mg L −1 , which was 2.6 times greater than that of the control culture.

Sorangium cellulosum is a myxobacteria producing epothilone B. During the development of the process to purify epothilone B from fermentation of Sorangium cellulosum we identified a possible ant trail pheromone. The initial detection, isolation and structure elucidation of S-3,4-dihydro-8-hydroxy-3,5,7-trimethylisocoumarin will be presented as well as literature regarding its biosignificance.

Using molecular modelling we have investigated the structure and dynamic properties of epothilone B-tubulin complexes with wild-type and mutated tubulin, aimed at identifying the molecular factors involved in the emergence of drug resistance induced by four protein mutations at Phe270Val, Thr274Ile, Arg282Gln and Gln292Glu. Our results revealed that tubulin mutations render significant changes in the protein conformation in regions involved either in the binding of the ligand or in interdimer contacts that are relevant to the assembly of stable microtubules. In addition, point mutations induce drastic changes in the binding pose of the ligand and in the interaction networks responsible for the epothilone-tubulin association. Large ligands displacements inside the binding pocket and an overall decrease in the strength of drug-receptor polar contacts suggest a looser binding of the ligand in tubulin mutants. These results explain the loss of activity for epothilone B against cancer cells that contain tubulin mutants and provide valuable information to enhance the understanding of the atomic source of epothilones’ activity, which can be helpful to conduct further research on the rational design of more potent therapeutic tubulin-binding agents.

After central nervous system (CNS) injury, inhibitory factors in the lesion scar and poor axon growth potential prevent axon regeneration. Microtubule stabilization reduces scarring and promotes axon growth. However, the cellular mechanisms of this dual effect remain unclear. Here, delayed systemic administration of a blood-brain barrier-permeable microtubule-stabilizing drug, epothilone B (epoB), decreased scarring after rodent spinal cord injury (SCI) by abrogating polarization and directed migration of scar-forming fibroblasts. Conversely, epothilone B reactivated neuronal polarization by inducing concerted microtubule polymerization into the axon tip, which propelled axon growth through an inhibitory environment. Together, these drug-elicited effects promoted axon regeneration and improved motor function after SCI. With recent clinical approval, epothilones hold promise for clinical use after CNS injury.

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The antimitotic agent paclitaxel continues to play an important role in cancer chemotherapy. However, its inefficacy on certain resistant cells and toxic side effects had led to the search for new drugs with improved biological activity. Here the QSAR models for microtubule stabilizing anticancer agents were performed to correlate their physicochemical properties with biological activity. Single and multiple linear regression models for six cancer cell lines were obtained with R2 ? 0.65 and q2pre ? 0.6. Molecular mechanics energy and log P of the molecules account for the activity of taxanes towards B16 melanoma and breast cancer cells, respectively. The lowest unoccupied molecular orbitals and the number of nitrogen atoms in the structure account for the biological activity of epothilone derivatives and rest of the drugs towards ovarian cells. The relation between the structural properties of microtubule stabilizing antimitotic compounds and their activities on different cell lines are investigated in this paper. � 2006 Wiley-VCH Verlag GmbH & Co. KGaA.

BMS-310705, a novel semisynthetic derivative of epothilone B, is a tubulin-polymerization agent currently in phase I clinical trials for anticancer therapy. The in vitro and in vivo pharmacokinetics and oral bioavailability of BMS-310705 were investigated in mice, rats, and dogs. In addition, comparison of the pharmacokinetics of BMS-310705 using various formulations was conducted in rats.The permeability of BMS-310705 was evaluated in Caco-2 cells, an in vitro model of the human intestinal epithelium. Human liver microsomes were used to determine the cytochrome P450 enzymes involved in the metabolism of BMS-310705. Plasma protein binding of BMS-310705 was determined in mouse, rat, dog, and humans. BMS-310705 was administered to female nude mice as single doses of 5 mg/kg intravenously or 15 mg/kg orally. Male Sprague-Dawley rats were treated with single doses of BMS-310705 either intraarterially (2 mg/kg) or orally (8 mg/kg). The effect of Cremophor on the pharmacokinetics of BMS-310705 was evaluated in rats using various formulations with and without Cremophor. Male dogs were treated with 0.5 mg/kg intravenously or 1 mg/kg orally in a crossover study design.Systemic clearance of BMS-310705 was high in mice (152 ml/min/kg), rats (39 ml/min/kg), and dogs (25.7 ml/min/kg). The volume of distribution (Vss) in mice, rats, and dogs was 38, 54, and 4.7 l/kg, respectively, and greater than total body water. BMS-310705 showed moderate binding to plasma proteins in all four species tested. The clearance in humans may be intermediate to high based on both allometric scaling using parameters obtained from three species, and in vitro human liver microsomal stability data. In rats, the presence of Cremophor in the formulation resulted in a significant increase in exposure compared to buffered vehicles not containing Cremophor. Inhibition of p-glycoprotein and/or CYP3A4 by Cremophor may be responsible for this phenomenon, and studies in Caco-2 cells and human liver microsomes suggested that BMS-310705 may be a substrate for both p-glycoprotein and CYP3A4. The oral bioavailability of BMS-310705 in pH buffered formulations was 21% in mice, 34% in rats and 40% in dogs.In summary, BMS-310705 is cleared rapidly and distributes extensively in mice, rats, and dogs. The presence of Cremophor in the formulation could significantly increase exposure in rats, possibly due to interactions with p-glycoprotein and/or CYP3A4. Oral bioavailability using formulations not containing Cremophor were found to be adequate, suggesting potential for development of BMS-310705 as an oral anticancer drug.

The purpose of this study was to determine activity of temozolomide combined with paclitaxel or epothilone B in vitro, and to investigate the combination of temozolomide with paclitaxel in a Phase I clinical trial. Melanoma cell lines A375P and DX3 were treated with temozolomide and either paclitaxel or epothilone B. Combination indices were determined to assess the degree of synergism. In a clinical study, 21 patients with malignant melanoma were treated with increasing doses of temozolomide (orally, days 1-5), in combination with a fixed dose of paclitaxel (i.v. infusion day 1), followed by dose escalation of the latter drug. Cycles of treatment were repeated every 3 weeks. Pharmacokinetics of both agents were determined on day 1, with temozolomide pharmacokinetics also assessed on day 5. All three compounds were active against the melanoma cell lines, with epothilone B being the most potent. There was a strong degree of synergism between temozolomide and either paclitaxel or epothilone B. In the clinical study, no pharmacokinetic interaction was observed between temozolomide and paclitaxel. Dose escalation of both drugs to clinically active doses was possible, with no dose-limiting toxicities observed at 200 mg m(-2) day(-1) temozolomide and 225 mg m(-2) day(-1) paclitaxel. There were two partial responses out of 15 evaluable patients. One patient remains alive and symptom-free at 4 years after treatment. Temozolomide and paclitaxel may be administered safely at clinically effective doses. Further evaluation of these combinations in melanoma is warranted.

Tubulin-binding agents play a pivotal role in current cancer therapy and there are many efforts in pre-clinical and clinical development of known and novel cytotoxic agents ongoing. In this article a known class, epothilones, as well as a novel class, tubulysins, are presented. © Springer 2005.

Total syntheses of epothilone B and pamamycin 607, which feature reactions between functionalized allylstannanes and aldehydes to introduce a (Z)-trisubstituted double-bond and remote stereocenters stereoselectively, are discussed. Recent work concerned with carrying out this chemistry without the use of allylstannanes as starting materials and progress toward a total synthesis of bryostatins are also presented.

To determine whether inhibitors of microtubule assembly inhibit polymerization induced by discodermolide and epothilone B, as well as paclitaxel, and to quantitatively measure such effects.Inhibition was quantitated by measuring polymer formation either by turbidimetry or by centrifugation, and the amount of inhibitor required to inhibit 50% relative to an appropriate control reaction was determined.The inhibitory drugs evaluated were four colchicine site agents (combretastatin A-4, podophyllotoxin, nocodazole, and N-acetylcolchinol- O-methyl ether), maytansine, which competitively inhibits the binding of Catharanthus alkaloids to tubulin, halichondrin B and phomopsin A, which noncompetitively inhibit the binding of Catharanthus alkaloids to tubulin, and the depsipeptide dolastatin 15. While relative inhibitory effects were highly variable, a few broad generalizations can be made. First, assembly reactions that were either enhanced or dependent upon all three stimulatory drugs were subject to inhibition by all inhibitors. Second, the more readily the tubulin assembled, the greater the concentration of inhibitor required to inhibit polymerization. Drug IC50 values were generally lowest with no stimulatory drug and highest when discodermolide was present; IC50 values were higher as reaction temperature increased; and IC50 values were higher as the tubulin concentration increased. Third, inhibition of assembly by inhibitors of Catharanthus alkaloid binding to tubulin changed much less as a function of changes in reaction conditions than inhibition by inhibitors of colchicine binding.Since there was no apparent quantitative predictability of combined drug interactions with tubulin, any combination of interest must be studied in detail.

An efficient synthesis of the epothilone B derivative 26-fluoroepothilone B (1) was realized by early introduction of the synthetically demanding fluoromethyl epoxide function. The presence of a fluoro substituent resultsin a remarkable increase in the stability of the epoxide, which tolerates the wide range of reaction conditions required for the fragment coupling step and end game transformations.

Starting from the X-ray structure of epothilone B, an original, non macrocyclic, structure has been designed to mimic the key structural features of this potent anticancer agent; the preparation of a key intermediate incorporating four stereogenic centers is described from cyclohexane-1,3-dione.

In this article, the synergistic effects of WP 631 and epothilone B (Epo B) combination in human ovarian cancer cells (SKOV-3) cells are investigated and the reasons for the exact mechanisms of action of both drugs co-administered are explained. Compared with single drugs, the combination treatment significantly enhances apoptosis as confirmed by increases in caspases (-8, -9, -3) activity, ROS level and DNA damage and decreases in mitochondrial membrane potential. The combination of the compounds activated both caspase - 8 and -9, indicates that both pathways of apoptosis, extrinsic (induced by the effect of Epo B) and intrinsic (triggered mainly by WP 631) participate in the proposed treatment. Thus, the results of this study strongly suggest a synergistic action of the combined treatment with WP 631 and Epo B in SKOV-3 cells death induction.

Pazopanib is a tyrosine kinase inhibitor predominantly acting on tumor endothelium, and ixabepilone is a semisynthetic analog of epothilone B that promotes microtubule stabilization inducing tumor and tumor endothelial cell apoptosis. The purpose of this study was to determine the optimal tolerated dose (OTD) of the combination of pazopanib and ixabepilone for the treatment of metastatic previously treated solid tumors.Dose escalation started at 32 mg/m of ixabepilone and increased to 40 mg/m. Pazopanib was administered initially at 400 mg and escalated at 200 mg increments up to 800 mg. Pharmacokinetic analysis assessed effect of ixabepilone on pazopanib metabolism. Correlative studies evaluated changes in angiogenic cytokines.Thirty-one patients (20 male and 11 female; median age, 58 y) with ECOG PS of 0 or 1 were enrolled. Three patients had dose-limiting toxicities (fatigue and neutropenia) at dose level 2 (ixabepilone 40 mg/m and pazopanib 400 mg), and therefore the ixabepilone dose was decreased (32 mg/m) before escalating pazopanib to levels 3 and 4. One patient had a dose-limiting toxicity (thrombocytopenia) at dose level 4 (ixabepilone 32 mg/m and pazopanib 800 mg). Dose level 3 was determined to be the OTD (pazopanib 600 mg and ixabepilone 32 mg/m). The most common toxicities were cytopenias. A significant decrease in the level of sE-selectin was associated with improvement in progression free survival.The OTD for combination of pazopanib and ixabepilone was established. There was no impact of ixabepilone on pazopanib pharmacokinetics. The relationship between sE-selectin and progression free survival warrants further investigation.

Stereoselective syntheses of epothilone B ( 1 ) and its novel derivative 2 are described. Key steps are the formation of intermediate 3 via Sharpless AD-reaction and Davis–Evans-hydroxylation.

The following review covers notable patent disclosures (October 1999 - March 2000) involving agents used as inhibitors of tumour cell growth. The primary focus of the review involves specific mechanism-based therapies such as tyrosine kinase inhibitors, cyclin dependent kinase inhibitors and ras-farnesyl transferase inhibitors. Recent disclosures involving new biotechnology, taxanes and other antiproliferative natural products will also be discussed.

A modified synthesis of the polypropionate portion of epothilone, which utilizes a novel, diastereoselective aldol reaction of ( S )-2-methyl-4-pentenal ( 4 ) and the Z -enolateof the tricarbonyl species ( 3 ) is reported.

An easy access to four out of five naturally occurring epothilones (A-E, 1–5 ) is reported. Key steps are an enantioselective Mukaiyama type aldol reaction, ( E )- and ( Z )-selective olefinations, and a sulfone alkylation.

Spinal cord injury is a debilitating condition. Axons of nerve cells are severed, resulting in a range of deficits, including the loss of voluntary movements and sensation. Failure of axonal regeneration after such an injury may be partly explained by a decreased intrinsic capacity for neuron growth, especially at the lesion site ( 1 ). On page 347 in this issue, Ruschel et al. ( 2 ) show that this inhibition can be overcome with a small molecule that can be injected into the body cavity, cross the bloodbrain barrier, and reach the central nervous system. The drug, epothilone B, stabilizes microtubules in extending axons, thereby promoting spinal cord regeneration.

Only a few months after the disclosure of the absolute configuration of epothilones A (R=H, see picture on the right) and B (R=Me) the first total syntheses of these natural products were reported. Interest intensified with the realization of their potential as anticancer agents with a taxol-like mechanism of action. In addition to describing the most important total syntheses and biological properties of the naturally occurring epothilones A-E, this review also provides a systematic overview of numerous epothilone analogues that have been modified in the A-D regions in order to obtain information about structure-activity relationships.