Epothilone A

Epothilone A (Epo A) is a naturally occurring microtubule-stabilizing macrolide that was first isolated from the myxobacterium Sorangium cellulosum. The IC50 value of Epothilone A in HCT-116 cell line is 4.4 nM [1].

It has been found that the SKOV-3 human ovarian cancer cells were susceptible to Epothilone A with IC50 value of 20.4 ± 1.4 nM [2]. The antiproliferative capacity of Epothilone A in SKOV-3 cell line (measured as IC50 after 72 h continuous treatment) was six times greater than that of PTX’s. Besides, Epothilone A induced time coursedependent apoptosis and necrosis [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, Marczak A, Gajek A, Szwed M, Śliwińska A, Drzewoski J, Jóźwiak Z. Induction of apoptosis in human ovarian cancer cells by new anticancer compounds, epothilone A and B. Toxicol In Vitro. 2013 Feb;27(1):239-49.

Stabilized Polymer Micelles for the Development of IT-147, an Epothilone D Drug-Loaded Formulation.[Pubmed:28044108]

J Drug Deliv. 2016;2016:8046739.

Epothilones have demonstrated promising potential for oncology applications but suffer from a narrow therapeutic window. Epothilone D stabilizes microtubules leading to apoptosis, is active against multidrug-resistant cells, and is efficacious in animal tumor models despite lack of stability in rodent plasma. Clinical development was terminated in phase II due to dose limiting toxicities near the efficacious dose. Taken together, this made epothilone D attractive for encapsulation in a stabilized polymer micelle for improved safety and efficacy. We have designed a library of triblock copolymers to develop IT-147, a lead formulation of epothilone D that extends plasma circulation for accumulation in the tumor environment, and potentially decrease systemic exposure to reduce dose limiting toxicities. The drug loading efficiency for IT-147 exceeds 90%, is 75 nm in diameter, and demonstrates pH-dependent release of epothilone D without chemical conjugation or enzymatic activation. Administration of IT-147 at 20 mg/kg increases exposure of epothilone D to the plasma compartment over 6-fold compared to free drug. At the same dose, 20 mg/kg epothilone D from IT-147 is considered the no observed adverse effect level (NOAEL) but is the maximum tolerated dose for free drug. Consequently, IT-147 is positioned to be a safer, more effective means to deliver epothilone D.

Effects of Microtubule Stabilization by Epothilone B Depend on the Type and Age of Neurons.[Pubmed:27872763]

Neural Plast. 2016;2016:5056418.

Several studies have demonstrated the therapeutic potential of applying microtubule- (MT-) stabilizing agents (MSAs) that cross the blood-brain barrier to promote axon regeneration and prevent axonal dystrophy in rodent models of spinal cord injury and neurodegenerative diseases. Paradoxically, administration of MSAs, which have been widely prescribed to treat malignancies, is well known to cause debilitating peripheral neuropathy and axon degeneration. Despite the growing interest of applying MSAs to treat the injured or degenerating central nervous system (CNS), consequences of MSA exposure to neurons in the central and peripheral nervous system (PNS) have not been thoroughly investigated. Here, we have examined and compared the effects of a brain-penetrant MSA, epothilone B, on cortical and sensory neurons in culture and show that epothilone B exhibits both beneficial and detrimental effects, depending on not only the concentration of drug but also the type and age of a neuron, as seen in clinical settings. Therefore, to exploit MSAs to their full benefit and minimize unwanted side effects, it is important to understand the properties of neuronal MTs and strategies should be devised to deliver minimal effective concentration directly to the site where needed.

Synthesis and Biological Evaluation of 7-Deoxy-Epothilone Analogues.[Pubmed:28304361]

Int J Mol Sci. 2017 Mar 17;18(3). pii: ijms18030648.

The synthesis of two deoxygenated analogues of potent epothilones is reported in an effort to analyze the relative importance of molecular conformation and ligand-target interactions to biological activity. 7-deoxy-epothilone D and 7-deoxy-(S)-14-methoxy-epothilone D were prepared through total synthesis and shown to maintain the conformational preferences of their biologically active parent congeners through computer modeling and nuclear magnetic resonance (NMR) studies. The significant decrease in observed potency for each compound suggests that a hydrogen bond between the C7-hydroxyl group and the tubulin binding site plays a critical role in the energetics of binding in the epothilone class of polyketides.

Epothilone B-based 3-in-1 polymeric micelle for anticancer drug therapy.[Pubmed:28062368]

Int J Pharm. 2017 Feb 25;518(1-2):307-311.

Epothilones are microtubule inhibitors that are promising alternatives to paclitaxel due to enhanced anticancer efficacy. While epothilones are slightly more water soluble than paclitaxel and more active against paclitaxel-resistant cells, they still require formulation with Cremophor EL and/or cosolvents and drug resistance still limits therapeutic efficacy. In this report, we showed that the combinational treatment of epothilone B (EpoB), 17-N-allylamino-17-demethoxygeldanamycin (17-AAG, Hsp90 inhibitor), and rapamycin (mTOR inhibitor) displays strong anticancer activity in vitro and in vivo. To address the poor water solubility of this 3 drug-combination, they were co-loaded into poly(ethylene glycol)-block-poly(d,l-lactic acid) (PEG-b-PLA) micelles, and the 3-in-1 loaded PEG-b-PLA micelle (m-EAR) was characterized in terms of drug loading efficiency, particle size, release kinetics. The m-EAR achieved high levels of all three drugs in water; formed micelles with hydrodynamic diameters at ca. 30nm and released the drugs in a sustained manner in vitro at rates slower than individually loaded PEG-b-PLA micelles. In A549-derived xenograft mice, m-EAR (2.0, 15.0, and 7.5mg/kg) caused tumor regression after four weekly injections, whereas EpoB alone (2.0mg/kg) was the same as control. No severe changes in body weight relative to PBS control were observed, attesting to the safety of m-EAR. Collectively, these results suggest that m-EAR provides a simple, but effective and safe EpoB-based combination nanomedicine for cancer therapy.