Epothilone B (EPO906, Patupilone)

Epothilone B (EPO906, Patupilone) is a naturally occurring microtubule-stabilizing macrolide that was first isolated from the myxobacterium Sorangium cellulosum. The EC0.01 value of Epothilone B is 1.8 nM [1].

Epothilone B exhibits the same mechanism of action as paclitaxel. More importantly, in cell culture, Epothilone B is active against paclitaxel-resistant cell lines that express P-glycoprotein. Furthermore, Epothilone B has better solubility in water than paclitaxel [1].

Epothilone B induced an increase in the level of the intracellular free calcium only during the longer times following the treatment in SKOV-3 cells. Besides, the ovarian cancer cells treated with Epothilone B showed a time course dependent increase in the cytosolic fraction of cytochrome c [2].

References:
[1] Regueiro-Ren A1, Borzilleri RM, Zheng X, Kim SH, Johnson JA, Fairchild CR, Lee FY, Long BH, Vite GD. Synthesis and biological activity of novel epothilone aziridines. Org Lett. 2001 Aug 23;3(17):2693-6.
[2] Rogalska A1, Gajek A2, Marczak A2. Epothilone B induces extrinsic pathway of apoptosis in human SKOV-3 ovarian cancer cells. Toxicol In Vitro. 2014 Jun;28(4):675-83.

Patupilone (epothilone B, EPO906) and imatinib (STI571, Glivec) in combination display enhanced antitumour activity in vivo against experimental rat C6 glioma.[Pubmed:15723258]

Cancer Chemother Pharmacol. 2005 Apr;55(4):307-317.

PURPOSE: The microtubule-stabilizing agent patupilone (epothilone B, EPO906) and the tyrosine kinase inhibitor imatinib (STI571, Glivec) which primarily inhibits Bcr-Abl, PDGF and c-Kit tyrosine kinase receptors, were combined in vivo to determine if any interaction would occur with respect to antitumour effect and tolerability using rat C6 glioma xenografted into nude mice. METHODS: Patupilone and imatinib were administered alone or in combination at suboptimal doses. Imatinib treatment (orally once daily) was initiated 4 days after s.c. injection of rat C6 glioma cells into athymic nude mice and patupilone administration (i.v. once per week) was started 3 or 4 days after imatinib treatment. RESULTS: As a single agent, imatinib was inactive in the regimens selected (100 mg/kg: T/C 86% and 116%; 200 mg/kg: T/C 68% and 84%; two independent experiments), but well tolerated (gain in body weight and no mortalities). Patupilone weekly monotherapy demonstrated dose-dependent antitumour effects (1 mg/kg: T/C 67% and 70%; 2 mg/kg: T/C 32% and 63%; 4 mg/kg: T/C 3% and 46%). As expected, dose-dependent body weight losses occurred (final body weight changes at 1 mg/kg were -7% and -3%; at 2 mg/kg were -23% and -13%; and at 4 mg/kg were -33% and -15%). Combining 2 mg/kg patupilone and 200 mg/kg per day imatinib in one experiment produced a non-statistically significant trend for an improved antitumour effect over patupilone alone (combination, T/C 9%), while in the second experiment, enhancement was seen with the combination and reached statistical significance versus patupilone alone (combination, T/C 22%; P=0.008). Reduction of the imatinib dose to 100 mg/kg per day resulted in no enhancement of antitumour activity in combination with 2 mg/kg patupilone. Reduction of the patupilone dose to 1 mg/kg resulted in a reduced antitumour effect, and only a trend for synergy with either imatinib dose (combination, T/C 46% and 40%). Pooling the data from the two experiments confirmed a significant synergy for the combination of 2 mg/kg patupilone and 200 mg/kg per day imatinib (P=0.032), and a trend for synergy at the 1 mg/kg patupilone dose. Reduction in the imatinib dose to 100 mg/kg per day resulted only in additivity with either dose of patupilone. Body weight losses were dominated by the effect of patupilone, since no greater body weight loss was observed in the combination groups. CONCLUSION: Combining patupilone with high-dose imatinib produced an increased antitumour effect without affecting the tolerability of treatment in a relatively chemoresistant rat C6 glioma model. Such results indicate that further evaluation is warranted, in particular to elucidate possible mechanisms of combined action.

Effects of patupilone (epothilone B; EPO906), a novel chemotherapeutic agent, in hepatocellular carcinoma: an in vitro study.[Pubmed:17657173]

Oncology. 2006;71(3-4):292-6.

PURPOSE: In this study, the cytotoxic effects of patupilone (epothilone B; EPO906) were assessed in a panel of hepatocellular carcinoma (HCC) cell lines, and were compared with doxorubicin and the microtubule-stabilizing taxanes. METHODS: The following HCC cell lines were used: PLC/PRF/5, HepG2, Hep3B, SNU-387, SNU-398, SNU-423, SNU-449, and SNU-475. Cells were treated with various concentrations of patupilone, paclitaxel, docetaxel, or doxorubicin for 72 h; 50% inhibitory concentrations (IC(50)) were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. P-glycoprotein expression was assessed using standard Western blotting techniques. RESULTS: Patupilone was found to be the most potent drug in all 8 HCC cell lines. All cell lines except SNU-449 were 4- to19-fold more sensitive to patupilone than to paclitaxel and docetaxel, and 59- to 208-fold more sensitive than to doxorubicin. SNU-449, the most resistant cell line and the only one overexpressing P-glycoprotein, was 3- to 39-fold more resistant to paclitaxel, docetaxel, and doxorubicin than were other cell lines. The IC(50) of patupilone in SNU-449 was 1.14 nmol, which was 108- to 529-fold lower than those of the other agents. CONCLUSION: Patupilone was more potent than taxanes and doxorubicin in HCC cell lines and may result in reduced clinical resistance by overcoming P-glycoprotein overexpression. A clinical study in HCC is warranted.

Altered TUBB3 expression contributes to the epothilone response of mitotic cells.[Pubmed:23321512]

Br J Cancer. 2013 Jan 15;108(1):82-90.

BACKGROUND: Epothilones are a novel group of microtubule (mt) targeting cancer drugs that bind to the beta-subunit of the alphabeta-tubulin dimer. Epothilones inhibit cell proliferation and induce cell death by interfering with the normal mt function. In this study, we examined the consequences of altered expression of human beta-tubulin isotypes in terms of the epothilone drug response in human lung and breast cancer cell lines. METHODS: The beta-tubulin isotypes TUBB2A-C, TUBB3 and TUBB were silenced or overexpressed in A549, A549EpoB40 and MCF7 cell lines in the presence or absence of epothilones. The drug effects on cell proliferation, mitosis and mt dynamics were determined using live cell microscopy and immunofluorescence assays. RESULTS: Loss of TUBB3 enhanced the action of epothilones. TUBB3 knockdown increased the severity of drug-induced mitotic defects and resulted in stabilisation of the mt dynamics in cells. Moreover, exogenous expression of TUBB3 in the epothilone resistant cell line conferred the response to drug treatments. In contrast, reduced levels of TUBB2A-C or TUBB had not apparent effect on the cells' response to epothilones. CONCLUSION: Our results show that the expression of TUBB3 contributes to the cellular response to epothilones, putatively by having an impact on the mt dynamics.

Pharmacokinetic profile of the microtubule stabilizer patupilone in tumor-bearing rodents and comparison of anti-cancer activity with other MTS in vitro and in vivo.[Pubmed:18301895]

Cancer Chemother Pharmacol. 2008 Nov;62(6):1045-54.

INTRODUCTION: Patupilone is a microtubule stabilizer (MTS) currently in clinical development. Here, we evaluate the anti-cancer activity in vitro and in vivo in comparison to paclitaxel and describe the pharmacokinetics (PK) of patupilone in tumor-bearing nude mice and rats. METHODS: The potency in vitro of patupilone and two other MTS, paclitaxel and ixabepilone, was determined using human colon carcinoma cell lines with low (HCT-116, HT-29, RKO) and high (HCT-15) P-glycoprotein expression (P-gp), as well as two multi-drug resistance (MDR) model cell pairs, MCF7/ADR and KB-8511 cells and their respective drug-sensitive parental counterparts. The PK of patupilone was investigated in nude mice bearing HCT-15 or HT-29 xenografts and in rats bearing s.c. pancreatic CA20498 tumors or A15 glioma tumors. Anti-cancer activity in vivo was compared to that of paclitaxel using three different human tumor colon models. The retention and efficacy of patupilone was compared in small and large HT-29 xenografts whose vascularity was determined by non-invasive magnetic resonance imaging. RESULTS: Patupilone was highly potent in vitro against four different colon carcinoma cell lines including those showing multi-drug-resistance. In contrast, paclitaxel and ixabepilone displayed significantly reduced activity with markedly increased resistance factors. In both rats and mice, a single i.v. bolus injection of patupilone (1.5-4 mg/kg) rapidly distributed from plasma to all tissues and was slowly eliminated from muscle, liver and small intestine, but showed longer retention in tumor and brain with no apparent elimination over 24 h. Patupilone showed significant activity against three human colon tumor models in vivo, unlike paclitaxel, which only had activity against low P-gp expressing tumors. In HT-29 tumors, patupilone activity and retention were independent of tumor size, blood volume and flow. CONCLUSIONS: The high potency of patupilone, which is not affected by P-gp expression either in vitro or in vivo, and favorable PK, independent of tumor vascularity, suggest that it should show significant activity in colorectal cancer and in other indications where high P-gp expression may compromise taxane activity.

Epothilone B is a microtubule stabilizer with a Ki of 0.71μM. It acts by binding to the αβ-tubulin heterodimer subunit which causes decreasing of αβ-tubulin dissociation.

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