Research paper Discovery of potent molecular chimera (CM358) to treat human metastatic melanoma Y. Gilad a , H. Tuchinsky b , G. Ben-David c , R. Minnes d , A. Gancz b , H. Senderowitz c , G. Luboshits e , M.A. Firer e , G. Gellerman a, * a Department of Chemical Sciences, Ariel University, Ariel, 40700, Israel b Department of Molecular Biology, Ariel University, Ariel, 40700, Israel c Department of Chemistry, Bar Ilan University, Ramat Gan, 5290002, Israel d Department of Physics, Ariel University, Ariel, 40700, Israel e Department of Chemical Engineering, Ariel University, Ariel, 40700, Israel article info Article history: Received 14 March 2017 Received in revised form 26 June 2017 Accepted 28 June 2017 Available online 29 June 2017 Keywords: Anticancer drugs Drugs combination Chimeric compounds Drug conjugation Human metastatic melanoma Molecular docking abstract The resistance of cancer cells to chemotherapeutic agents, whether through intrinsic mechanisms or developed resistance, motivates the search for new chemotherapeutic strategies. In the present report, we demonstrate a facile synthetic strategy towards the discovery of new anti-cancer substances. This strategy is based on simple covalent coupling between known anti-cancer drugs, which results in novel 'chimeric' small molecules. One of these novel compounds, CM358, is the product of an amide bond formation between the known Topoisomerase II (Topo II) inhibitor amonafide (AM) and the known DNA mustard alkylator chlorambucil (CLB). It demonstrates significant enhanced cytotoxicity over an equi- molar mixture of AM and CLB in various cancer cell lines and in a xenograft model of human metastatic melanoma. Topo II inhibition as well as in silico docking studies suggest that CM358 is a stronger Topo II binder than AM. This may be attributed, at least partially, to the placement of the CLB moiety in a favorable orientation with respect to DNA cross-linking with nearby guanines. In a human metastatic melanoma (WM 266-4) xenograft model, this compound was profoundly superior to a mixture of AM and CLB in reduction of tumor growth, maintenance of body weight and extension of overall survival. © 2017 Elsevier Masson SAS. All rights reserved. 1. Introduction Chemotherapy is a well-established and potent method for cancer treatment. However, chemotherapy has several major pit- falls including lack of effectiveness against drug resistance clones. Administration of drug combinations with differing mechanisms of action is a promising therapeutic strategy to enhance the effec- tiveness of the treatment [1e4]. Yet, to date combination chemo- therapy by simple co-administration of drugs did not profoundly inhibit the development of drug resistance in cancer cells [5,6]. Consequently alternative methods for combination therapies are actively sought [7,8]. One such approach is the use of chemical chimerasin which selected drug building blocks are covalently linked to form a single compound. Chimeras are expected to pro- vide an efficient means to the discovery of novel drug candidates [9e11]. Yet to date there are only limited examples in the literature in which direct fusion of two small molecules resulted in more than an additive effect on anti-cancer activity. Ohsawa et al. synthesized bestrabucil by conjugating estradiol with CLB [12]. Bestrabucil was designed as a payload molecule with estradiol acting as the vehicle, directing the chimera to estrogen receptor positive tumors. This mutual prodrug exhibited an improved pharmacological profile [12,13]. In another study, Yan and coworkers performed direct conjugation between the hydrophilic irinotecan and the hydro- phobic CLB to obtain an amphiphilic drug-drug conjugate which self assembles into nanoparticles [14]. The formulation resulted in both improved blood stability and tumor accumulation properties compared with the free drugs which led to enhanced anti-cancer activity. A somewhat related strategy to direct drug conjugation is the integration of pharmacophore elements from two different active compounds leading to a single entity with enhanced activity. Other examples for this approach were reported with small anti- cancer compounds [15e18] and with antimalarial chemothera- peutics [19e21]. To expend on the development of new chimeric * Corresponding author. E-mail address: garyg@ariel.ac.il (G. Gellerman). 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.2017.06.066 0223-5234/© 2017 Elsevier Masson SAS. All rights reserved. European Journal of Medicinal Chemistry 138 (2017) 602e615