High-affinity ligands of the colchicine domain in tubulin based on a structure-guided design

Abstract

Microtubule-targeting agents that bind at the colchicine-site of tubulin are of particular interest in antitumoral therapy due to their dual mechanism of action as antimitotics and vascular disrupting agents. Cyclohexanediones derivatives have been described as a new family of colchicine-domain binders with an association constant to tubulin similar to that of colchicine. Here, the high-resolution structures of tubulin in complex with cyclohexanediones TUB015 and TUB075 were solved by X-ray crystallography. A detailed analysis of the tubulin-TUB075 interaction by means of computational affinity maps allowed the identification of two additional regions at the binding site that were addressed with the design and synthesis of a new series of cyclohexanediones with a distal 2-substituted benzofurane. These new compounds showed potent antiproliferative activity with IC50 values in the nM range, arrested cell cycle progression at the G2/M phase and induced apoptosis at sub μM concentrations. Moreover, they caused the destruction of a preformed vascular network in vitro and inhibited the migration of endothelial cells at non-toxic concentrations. Finally, these compounds displayed high affinity for tubulin as substantiated by a Kb value of 2.87 × 108 M−1 which, to the best of our knowledge, represents the highest binding constant measured to date for a colchicine-domain ligand.

Disruption of microtubule function in cultured human cells by a cytotoxic ruthenium(ii) polypyridyl complex

“…As seen from Table 2, RPC2 binds to preformed MTs tightly, with a K of 4.9 Â 10 6 M À1 which is nearly the same as that obtained for DTX binding the preformed MTs (K ¼ 5.5 Â 10 6 M À1 ) for DTX binding to preformed MTs. Reported association constants PTX and DTX with MTs are 10.7 Â 10 6 M À1 and 30.9 Â 10 6 M À1 , respectively, 54,55 which is in excellent agreement with our data given that different techniques were used (ITC vs. competitive binding titrations). 56 A binding stoichiometry of one ligand per tubulin dimer is known for DTX and colchicine, which was also supported for RPC2 from the inection point of the isotherms at a 1 : 1 mole ratio.…”

Antitubulin sulfonamides: The successful combination of an established drug class and a multifaceted target

“…ABT‐751 was the pioneer compound of the class but has unfortunately shown low efficacy, probably associated with insufficient potency. More recently, two pentafluorophenylsulfonamides (T138067 and T900607), which are putative covalent modifiers and therefore less likely to suffer from lack of efficacy, have entered clinical trials …”

Design and Synthesis of New Tubulin Polymerization Inhibitors Inspired from Combretastatin A‐4: An Anticancer Agent

“…Different aryl aldoximes [(1-5) a] were synthesized in the first step by treating aryl aldehydes with electron releasing as well as electron-withdrawing substituents with hydroxylamine hydrochloride and sodium bicarbonate in quantitative yield. These aryl aldoximes later were reacted with a dipolarophile, 'an activated alkene' that is ethyl acrylate in the presence of iodobenzene diacetate (DIB) and catalytic trifluoroacetic acid to afford 2-isoxazoline intermediate [ (1)(2)(3)(4)(5) b] via 1, 3-dipolar cycloaddition reaction. [53,54] The resulting aryl isoxazoline ester [(1-5) b] was successfully reduced to aryl dihydro-isoxazolyl alcohols [(1-5) c] using sodium borohydride in methanol at the cold condition with 100 % reduction.…”

“…Subsequently, the tosylate intermediates [(1-5) d] were allowed to react with sodium azide at 70°C temperature for two hours to generate substitution product, azide derivatives [(1-5) e]. [56] Treatment of azide derivatives [(1-5) e] with different substituted aryl alkynes & aliphatic alkynes (1)(2)(3)(4)(5)(6) in the presence of copper iodide and N, N-diisopropylethylamine at room temperature for 2 to 3 h afforded the click chemistry products-1, 2, 3 -triazole substituted final compounds [(1-5) f-(1-6)]. [57,58]…”

“…[1,2] Molecules like Combretastatin A-4 (CA-4) (1), Combretastatin A-4 Phosphate (CA-4P) (2), Podophyllotoxin (3), TN-16 (4), Colchicine (5) (Figure 1) all bind at Colchicine binding site (CBS) and inhibit cell mitosis. [3][4][5] The major challenge faced by drugs implemented clinically in chemotherapy have limitations related to bioavailability, multi-drug resistance (MDR), and reduced drug-molecule interactions to mutated forms of proteins. [6][7][8] Various synthetic derivatives have been reported based on Colchicine, and CA-4 with structural modifications following the structure-activity relations (SAR) studies to analyse the target specificity, the binding mode of molecules, and explore more information on their mechanism of action.…”