Original article Multidrug resistance (MDR) reversers: High activity and efficacy in a series of asymmetrical N,N-bis(alkanol)amine aryl esters Silvia Dei a, * , Marcella Coronnello b , Elisa Floriddia a , Gianluca Bartolucci a , Cristina Bellucci a , Luca Guandalini a , Dina Manetti a , Maria Novella Romanelli a , Milena Salerno c , Ivan Bello c , Enrico Mini b , Elisabetta Teodori a a Dipartimento NEUROFARBA-Sezione di Farmaceutica e Nutraceutica, Universit a di Firenze, Via Ugo Schiff 6, 50019 Sesto Fiorentino, FI, Italy b Dipartimento di Scienze della Salute, Universit a di Firenze, Viale Pieraccini 6, 50139 Firenze, Italy c Universit e Paris 13, Sorbonne Paris Cit e, Laboratoire CSPBAT, CNRS (UMR 7244), UFR-SMBH, 74 Rue Marcel Cachin, 93017 Bobigny, France article info Article history: Received 6 June 2014 Received in revised form 12 September 2014 Accepted 26 September 2014 Available online 30 September 2014 Dedicated to the memory of our colleague and friend Professor Serena Scapecchi pre- maturely deceased. Keywords: MDR reversers P-gp inhibitors N,N-bis(alkanol)amine aryl esters Chemosensitizers Doxorubicin-resistant erythroleukemia K562 cells (K562/DOX) Pirarubicin uptake abstract As a continuation of our research on potent and efficacious P-gp-dependent multidrug resistance (MDR) reversers, several new N,N-bis(alkanol)amine aryl esters were designed and synthesized, varying the aromatic moieties or the length of the methylenic chain. The new compounds were tested on doxorubicin-resistant erythroleukemia K562 cells (K562/DOX) in the pirarubicin uptake assay, where most of the new compounds were shown to be active. In particular the asymmetrical compounds, characterized by two linkers of different length, generally showed fairly high activities as MDR reversers. Some selected compounds (isomers 15e17) were further studied by evaluating their doxorubicin cyto- toxicity enhancement (reversal fold, RF) on the K562/DOX cell line. The results of both pharmacological assays indicate that compounds 16 (GDE6) and 17 (GDE19) could be interesting leads for the develop- ment of new P-gp dependent MDR modulators. © 2014 Elsevier Masson SAS. All rights reserved. 1. Introduction Multidrug resistance (MDR) occurs when cancer cells become resistant to chemotherapeutic drugs of different structure and mechanism of action, resulting in the failure of cancer treatment [1]. This kind of resistance is associated with the over-expression of a family of ATP-dependent transporter proteins that extrude the chemotherapeutic drug from the cells, lowering its concentration below that necessary for anticancer action. This hypothesis was first formulated 40 years ago [2] and confirmed when P-glycopro- tein (P-gp) was identified and studied [3]. Further studies have shown that P-gp (ABCB1) is the most important member of a super family of ATP-dependent transporter proteins that includes BCRP (ABCG2) and MRP1 (ABCC1) as other representative players. P-gp, the best studied member of the family, is a highly permissive protein which transports a wide diversity of substrates. Intensive work on this family of transporters has shown that multidrug transporters are present in almost every cell where their physio- logical role seems to be that of controlling the traffic of lipophilic molecules and protecting the cell from toxic xenobiotics by extruding them from the cell [4,5]. ABC proteins and especially P-gp are expressed in many tissues, mostly in membrane barriers such as BBB (bloodebrain barrier) [6]. Although a high resolution crystal structure of human P-gp is still lacking, fundamental information on its structure and mechanism of action has been collected from the resolution of the 3D-structures of the bacterial homolog Sav1866 [7] and murine P-gp (having 87% of homology with human List of abbreviations: P-gp, P-glycoprotein; BCRP, breast cancer resistance pro- tein; MRP1, multidrug resistance-associated protein 1; ABCB1, ATP binding cassette protein B1; ABCG2, ATP binding cassette protein G2; ABCC1, ATP binding cassette protein C1; DOX, doxorubicin; EDCl, 1-(3-dimethylaminopropyl)-3- ethylcarbodiimmide hydrochloride; MTT, 3-(4,5-dimethylthiazolyl-2)-2,5- diphenyltetrazolium bromide. * Corresponding author. E-mail address: silvia.dei@unifi.it (S. Dei). Contents lists available at ScienceDirect European Journal of Medicinal Chemistry journal homepage: http://www.elsevier.com/locate/ejmech http://dx.doi.org/10.1016/j.ejmech.2014.09.084 0223-5234/© 2014 Elsevier Masson SAS. All rights reserved. European Journal of Medicinal Chemistry 87 (2014) 398e412