New Prodrugs of the Antiprotozoal Drug Pentamidine

Pharmaceutical Institute, Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, Gutenbergstrasse 76-78, 24118 Kiel, Germany.
ChemMedChem (Impact Factor: 2.97). 12/2011; 6(12):2233-42. DOI: 10.1002/cmdc.201100422
Source: PubMed


Pentamidine is an effective antimicrobial agent that is approved for the treatment of African trypanosomiasis but suffers from poor oral bioavailability and central nervous system (CNS) penetration. This work deals with the development and systematic characterisation of new prodrugs of pentamidine. For this reason, numerous prodrugs that use different prodrug principles were synthesised and examined in vitro and in vivo. Another objective of the study was the determination of permeability of the different pentamidine prodrugs. While some of the prodrug principles applied in this study are known, such as the conversion of the amidine functions into amidoximes or the O-alkylation of amidoximes with a carboxymethyl residue, others were developed more recently and are described here for the first time. These newly developed methods aim to increase the affinity of the prodrug for the transporters and mediate an active uptake via carrier systems by conjugation of amidoximes with compounds that improve the overall solubility of the prodrug. The different principles chosen resulted in several pentamidine prodrugs with various advantages. The objective of this investigation was the systematic characterisation and evaluation of eight pentamidine prodrugs in order to identify the most appropriate strategy to improve the properties of the parent drug. For this reason, all prodrugs were examined with respect to their solubility, stability, enzymatic activation, distribution, CNS delivery, and oral bioavailability. The results of this work have allowed reliable conclusions to be drawn regarding the best prodrug principle for the antiprotozoal drug pentamidine.

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    • "furamidine, DB820 and DB829, Figs 1 and 3) replacing the alkyl chain in the pentamidine. As discussed in the section 'Design and synthesis', various pro-drugs of diamidines have been designed to improve oral bioavailability, by masking the positive charge of the amidine moiety using hydroxy, alkyloxy, acetoxy and amino acids (Clement and Raether, 1985; Boykin et al. 1996; Ismail et al. 2003; Kotthaus et al. 2011). Biotransformation of pafuramidine (Fig. 3), the methoxy pro-drug of furamidine, to the active furamidine is complex, involving multiple steps of sequential oxidative O-demethylation and reductive N-dehydroxylation reactions that are catalysed by cytochrome P450 enzymes and the cytochrome b5/NADH b5 reductase system, respectively (Saulter et al. 2005; Wang et al. 2006, 2007). "
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