Antiprotozoal activity and DNA binding of N-substituted N-phenylbenzamide and 1,3-diphenylurea bisguanidines

Two series of N-alkyl, N-alkoxy, and N-hydroxy bisguanidines derived from the N-phenylbenzamide and 1,3-diphenylurea scaffolds were synthesised in three steps from the corresponding 4-amino-N-(4-aminophenyl)benzamide and 1,3-bis(4-aminophenyl)urea, respectively. All of the new compounds were evaluated in vitro against T. b. rhodesiense (STIB900) trypomastigotes and Plasmodium falciparum NF54 parasites (erythrocytic stage). N-alkoxy and N-hydroxy derivatives showed weak micromolar range IC50 values against T. b. rhodesiense and P. falciparum whereas the N-alkyl analogues displayed submicromolar and low nanomolar IC50 values against P. falciparum and Trypanosoma brucei, respectively. Two compounds, 4-(2-ethylguanidino)-N-(4-(2-ethylguanidino)phenyl)benzamide dihydrochloride (7b) and 4-(2-isopropylguanidino)-N-(4-(2-isopropylguanidino)phenyl)benzamide dihydrochloride (7c), which showed favourable drug-like properties and in vivo efficacy (100% cures) in the STIB900 mouse model of acute human African trypanosomiasis represent interesting leads for further in vivo studies. The binding of these compounds to AT-rich DNA was confirmed by surface plasmon resonance (SPR) biosensor experiments.