Cinnamoyl nitrogen mustard derivatives of pyrazole analogues of tallimustine modified at the amidino moiety: design, synthesis, molecular modeling and antitumor activity studies Pier Giovanni Baraldi, a, * Italo Beria, b Paolo Cozzi, b Cristina Geroni, b Antonio Espinosa, c Miguel A. Gallo, c Antonio Entrena, c John P. Bingham, d John A. Hartley d and Romeo Romagnoli a a Dipartimento di Scienze Farmaceutiche, Universit a di Ferrara, 44100 Ferrara, Italy b Pharmacia Italia S.p.A., Discovery Research Oncology, 20014 Nerviano, Milan, Italy c Departamento de Qu  ımica Farmac eutica y Org anica, Facultad de Farmacia, Universidad de Granada, 18071, Spain d Cancer Research UK Drug–DNA Interactions Research Group, Department of Oncology, Royal Free and University College Medical School, UCL, 91 Riding House Street, London W1W 7BS, UK Received 10 March 2004; accepted 30 April 2004 Available online 8 June 2004 Abstract—Thedesign,synthesisandinvitroactivitiesofaseriesofcinnamoylnitrogenmustardpyrazoleanaloguesoftallimustine 8–13, in which the amidino moiety has been replaced by moieties of different physico-chemical features are described, and the structure–activity relationships are discussed. In spite of the relevance of these modifications on the amidino moiety, these deriv- ativesshowedsignificantgrowthinhibitoryactivityagainstmouseleukemiaL1210cells.Aselectedseriesofcompoundshavebeen evaluated for their sequence selective alkylating properties and cytotoxicity against human K562 leukemia cells. Therefore, the presence of the amidino moiety, and in general of a basic moiety, is not an absolute requirement for biological activity. Our pre- liminaryresultsindicatedthatthecompoundsofthisserieshaveapatternofalkylationsimilartothatoftallimustine,buttheyseem to be less reactive overall in alkylating naked DNA. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction DNAminorgroovebinderscanactsassuitablecarriers for alkylating agents, giving rise to compounds with cytotoxic properties. Tallimustine 1 (FCE 24517, PNU- 152241),adistamycinA 1 derivativeinwhichtheformyl grouphasbeenreplacedbyabenzoylnitrogenmustard moiety (BAM), is a potent cytotoxic agent, which exhibits a broad spectrum of antitumor activity in experimental tumor models. 2 Previous studies have indicated that tallimustine retains the AT preference of distamycin A and appears to possess a high preference foralkylationofadenineslocatedinthe5 0 -TTTTG A-3 0 sequence. 3 The mechanism by which the alkylation in- duced by tallimustine leads to cytotoxicity remains un- clear. While the cytotoxicity of BAM is related to the ability to form interstrand cross-links in DNA 4 with consequent inhibition of DNA replication and tran- scription, the mechanism of antitumor action of talli- mustine, although it is not fully elucidated yet, may be due to its ability to inhibit the binding of some tran- scription factors to their consensus sequences in DNA, thereby preventing transcription. 3;5 Tallimustine was selectedasacandidateantineoplasticdruginviewofits strong activity against a series of experimental tumors. Unfortunately, tallimustine showed a severe myelotox- icity that probably impaired the achievement of an effective therapeutic doses and its Phase II clinical development was discontinued. 6 Nevertheless, tallimustine has represented an important model for the design of new cytotoxic minor groove binders derived from distamycin, where the formyl group has been replaced by moieties of mild chemical Keywords:Cinnamoylnitrogenmustardderivatives;Pyrazoleamidino modified moiety; Antitumor activity; Tallimustine. *Corresponding author. Tel.: +39-0532-291293; fax: +39-0532-2912- 96; e-mail: brlpgv@unife.it 0968-0896/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmc.2004.04.045 Bioorganic & Medicinal Chemistry 12 (2004) 3911–3921