Bioorganic Medicinal Chemistry 20(2012)4489-4494 Contents lists available at SciVerse Science Direct Bioorganic Medicinal Chemistry ELSEVIER journalhomepagewww.elsevier.com/locate/bmc Antitumor agents 294. Novel E-ring- modified camptothecin -4B-anilino O-demethyl-epipodophyllotoxin conjugates as DNa topoisomerase I inhibitors and cytotoxic agents Deyong Ye a, Qian Shia, * Chung-Hang Leung b . Seung-Whan Kim b, Shin-Young Park b, Elizabeth A. Gullen Zao Li Jiang Hao Zhu, Susan L. Morris-Natschke Yung-Chi Cheng b, * f Kuo-Hsiung Lee,,* tural Products Research Laboratories, UNC Eshelman School of pharmacy, University of North Carolina at Chapel Hill, Chapel Hill NC 27599-7568, epartment of pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA Department of chemistry, The Rutgers Center for Computational and integrative Biology, Rutgers University. 315 Penn St, Camden, N 08102, USA Chinese Medicine Research and Development Center, China Medical University and Hospital, Taichung Taiwan ARTICLE INFO ABSTRACT Two conjugates (I and 2)of camptothecin(CPT)and 4B-anilino-4'-0-demethylepipodophyllotoxin were eceived 3 February 2012 previously shown to exert antitumor activity through inhibition of topoisomerase I (topo I). In this cur rent study, two novel conjugates(lE and 2E) with an open E-ring in the CPr moiety were first synthe- Available online 19 May 2012 sized and evaluated for biological activity in comparison with their intact E-ring congeners. This novel class of CPT-derivatives exhibits its antitumor effect against CPT-sensitive and -resistant cells, in part, by inhibiting topo l-linked DNA(TLD) religation. An intact E-ring was not essential for the inhibition of TLD religation, although conjugates with an open E-ring were less potent than the closed ring analog his lower religation potency resulted in decreased formation of protein-linked DNa breaks(PLDBs nd hence, less cell growth inhibition. In addition to their impact on topo l, conjugates 1E, 2, and 2E exhibited a minor inhibitory effect on topo Il-induced DNA cleavage. The novel structures of 1E and 2E pharmacological profiles and physicoche p ment of dual function topo I and ll inhibitors with improved may present scaffolds for further devel 2012 Elsevier Ltd. All rights reserved. 1 Introduction CPT-resistance can result from various cellular events, including inadequate accumulation of the drug, alteration of topo I resulting Camptothecin(CPT), an alkaloid isolated from the Chinese bush in decreased formation of protein-linked DNa breaks(PLDB), and Camptotheca acuminata(Nyssaceae) by Wall and co-workers in alterations in the cellular response to the topo l-CPT interaction. 1966, was the first identified specific inhibitor of DNa topoisc merase 1.2 Topoisomerase I(Topo I)cuts one strand of double- ten accompanied by a concomitant rise in the level of topo ll stranded DNA, relaxes the strands, and then re-anneals the expression and vice versa, which leads to the failure of clinical strands. CPT exhibits its cytotoxic activity by stabilizing the to therapies. I-DNA complex, which prevents religation and causes single Topoisomerase inhibitors with dual target specificity could pos- stranded breaks, a process that eventually leads to cell death. Sev- sibly overcome CPT-resistance. Dual target inhibitors would likely cral CPT-derivatives including topotecan and irinotecan( CPt- retain cytotoxic activity when resistance was acquired due to alter 11).5.6 have been used clinically for the treatment of colorectal, ation of only one drug target. However, the physical combination of ovarian and small cell lung cancers. However, the development CPT with drugs such as amsacrine and doxorubicin, which also of resistance to these compounds is still a critical clinical problem. interfere with DNA topoisomerases, often caused antagonistic cyto- toxic effects rather than synergistic activity -In this regards, single compound able to inhibit both topo I and topo ll may present ng authors.Te:+19198436325(Qs.J.tel+19199620066 he advantage of improving anti-topoisomerase activity with re- fax:+19199663893(KHL): tel:+12037857118: fax: +1 203 7129 (Y C C.). duced or avoiding adversities respect to the combination of two E-mail addresses: qshil@emailuncedu(Q Shi) yacheng@yale.edu(Y-C. Cheng lee@unc.edu(K-H. Lee). nhibitors. Many efforts have been made to discover and develop Leung, CH and Kim, S.w. contributed equally to this wor a powerful'magic bullet targeted to both enzymes, such as f Fellow of the National Foundation for Cancer Research. Tafluposide, Batracylin, 5 and other synthetic or natural products -0896/s- see front matter o 2012 Elsevier Ltd. All right l/dx doiorg/10. 1016 j. bmc. 2012.05.03Antitumor agents 294. Novel E-ring-modified camptothecin–4b-anilino-40 - O-demethyl-epipodophyllotoxin conjugates as DNA topoisomerase I inhibitors and cytotoxic agents Deyong Ye a , Qian Shi a,⇑ , Chung-Hang Leung b, , Seung-Whan Kim b, , Shin-Young Park b , Elizabeth A. Gullen b , Zao Li Jiang b , Hao Zhu c , Susan L. Morris-Natschke a , Yung-Chi Cheng b,⇑, , Kuo-Hsiung Lee a,d,⇑ aNatural Products Research Laboratories, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7568, USA bDepartment of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA cDepartment of Chemistry, The Rutgers Center for Computational and Integrative Biology, Rutgers University, 315 Penn St., Camden, NJ 08102, USA d Chinese Medicine Research and Development Center, China Medical University and Hospital, Taichung, Taiwan article info Article history: Received 3 February 2012 Revised 4 May 2012 Accepted 12 May 2012 Available online 19 May 2012 Keywords: Topoisomerase Cytotoxicity Camptothecin (CPT) Etoposide (VP-16) Epipodophyllotoxin Conjugates abstract Two conjugates (1 and 2) of camptothecin (CPT) and 4b-anilino-40 -O-demethylepipodophyllotoxin were previously shown to exert antitumor activity through inhibition of topoisomerase I (topo I). In this cur￾rent study, two novel conjugates (1E and 2E) with an open E-ring in the CPT moiety were first synthe￾sized and evaluated for biological activity in comparison with their intact E-ring congeners. This novel class of CPT-derivatives exhibits its antitumor effect against CPT-sensitive and -resistant cells, in part, by inhibiting topo I-linked DNA (TLD) religation. An intact E-ring was not essential for the inhibition of TLD religation, although conjugates with an open E-ring were less potent than the closed ring analogs. This lower religation potency resulted in decreased formation of protein-linked DNA breaks (PLDBs), and hence, less cell growth inhibition. In addition to their impact on topo I, conjugates 1E, 2, and 2E exhibited a minor inhibitory effect on topo II-induced DNA cleavage. The novel structures of 1E and 2E may present scaffolds for further development of dual function topo I and II inhibitors with improved pharmacological profiles and physicochemical properties. 2012 Elsevier Ltd. All rights reserved. 1. Introduction Camptothecin (CPT), an alkaloid isolated from the Chinese bush Camptotheca acuminata (Nyssaceae) by Wall and co-workers in 1966,1 was the first identified specific inhibitor of DNA topoiso￾merase I.2 Topoisomerase I (Topo I) cuts one strand of double￾stranded DNA, relaxes the strands, and then re-anneals the strands.3 CPT exhibits its cytotoxic activity by stabilizing the topo I-DNA complex, which prevents religation and causes single stranded breaks, a process that eventually leads to cell death.4 Sev￾eral CPT-derivatives, including topotecan and irinotecan (CPT- 11),5,6 have been used clinically for the treatment of colorectal, ovarian and small cell lung cancers. However, the development of resistance to these compounds is still a critical clinical problem. CPT-resistance can result from various cellular events, including inadequate accumulation of the drug, alteration of topo I resulting in decreased formation of protein-linked DNA breaks (PLDB), and alterations in the cellular response to the topo I-CPT interaction.7 Furthermore, the acquisition of resistance to topo I inhibitors is of￾ten accompanied by a concomitant rise in the level of topo II expression and vice versa, which leads to the failure of clinical therapies. Topoisomerase inhibitors with dual target specificity could pos￾sibly overcome CPT-resistance. Dual target inhibitors would likely retain cytotoxic activity when resistance was acquired due to alter￾ation of only one drug target. However, the physical combination of CPT with drugs such as amsacrine and doxorubicin, which also interfere with DNA topoisomerases, often caused antagonistic cyto￾toxic effects rather than synergistic activity.8–11 In this regards, a single compound able to inhibit both topo I and topo II may present the advantage of improving anti-topoisomerase activity, with re￾duced or avoiding adversities respect to the combination of two inhibitors. Many efforts have been made to discover and develop a powerful ‘magic bullet’ targeted to both enzymes,12,13 such as Tafluposide,14 Batracylin,15 and other synthetic or natural products. 0968-0896/$ - see front matter 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.bmc.2012.05.030 ⇑ Corresponding authors. Tel.: +1 919 843 6325 (Q.S.); tel.: +1 919 962 0066; fax: +1 919 966 3893 (K.H.L.); tel.: +1 203 785 7118; fax: +1 203 785 7129 (Y.C.C.). E-mail addresses: qshi1@email.unc.edu (Q. Shi), yccheng@yale.edu (Y.-C. Cheng), khlee@unc.edu (K.-H. Lee). Leung, C.H. and Kim, S.W. contributed equally to this work. Fellow of the National Foundation for Cancer Research. Bioorganic & Medicinal Chemistry 20 (2012) 4489–4494 Contents lists available at SciVerse ScienceDirect Bioorganic & Medicinal Chemistry journal homepage: www.elsevier.com/locate/bmc