Bisamidate Prodrugs of 2‐Substituted 9‐[2‐(Phosphonomethoxy)ethyl]adenine (PMEA, adefovir) as Selective Inhibitors of Adenylate Cyclase Toxin from Bordetella pertussis

Abstract

Novel small-molecule agents to treat Bordetella pertussis infections are highly desirable, as pertussis (whooping cough) remains a serious health threat worldwide. In this study, a series of 2-substituted derivatives of 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA, adefovir), in their isopropyl ester bis(L-phenylalanine) prodrug form, were designed and synthesized as potent inhibitors of adenylate cyclase toxin (ACT) isolated from B. pertussis. The series consists of PMEA analogues bearing either a linear or branched aliphatic chain or a heteroatom at the C2 position of the purine moiety. Compounds with a small C2 substituent showed high potency against ACT without cytotoxic effects as well as good selectivity over human adenylate cyclase isoforms AC1, AC2, and AC5. The most potent ACT inhibitor was found to be the bisamidate prodrug of the 2-fluoro PMEA derivative (IC50 =0.145 μM). Although the bisamidate prodrugs reported herein exhibit overall lower activity than the bis(pivaloyloxymethyl) prodrug (adefovir dipivoxil), their toxicity and plasma stability profiles are superior. Furthermore, the bisamidate prodrug was shown to be more stable in plasma than in macrophage homogenate, indicating that the free phosphonate can be effectively distributed to target tissues, such as the lungs. Thus, ACT inhibitors based on acyclic nucleoside phosphonates may represent a new strategy to treat whooping cough.

Novel nucleotide analogues bearing (1 H -1,2,3-triazol-4-yl)phosphonic acid moiety as inhibitors of Plasmodium and human 6-oxopurine phosphoribosyltransferases

“…Analytical TLC was performed on plates of Kieselgel 60 F 254 from Merck. NMR spectra were recorded on Bruker Avance 400 spectrometer ( 1 H at 400 MHz, 13 C at 100.6 MHz, 31 P at 161.9 MHz) with TMS or dioxane (3.75 ppm for 1 H, 67.19…”

“…10 ppm for 13 C NMR) as internal standard or referenced to the residual solvent signal. Mass spectra were measured on UPLC-MS (Waters SQD-2).…”

“…Several different chemical types of ANPs, including modified PMEA analogues, have also been studied as potent inhibitors of bacterial adenylate cyclases, namely adenylate cyclase toxin from Bordetella pertussis and edema factor from Bacillus anthracis. [12][13][14] Such analogues may have potential for treatment or prevention of toxaemia caused by the invasion of these bacteria into the human host. Inhibition of plasmodial hypoxanthine-guanine-(xanthine) phosphoribosyltransferases (HG(X)PRTs) by the ANPs is well-correlated with their antimalarial activity.…”

Synthesis and evaluation of symmetric acyclic nucleoside bisphosphonates as inhibitors of the Plasmodium falciparum, Plasmodium vivax and human 6-oxopurine phosphoribosyltransferases and the antimalarial activity of their prodrugs

“…33,34,35 In our SAR-study, the ethyl ester of the natural amino acid, L-phenylalanine, was selected to mask both phosphonate groups of our inhibitors. 36,37 This type of prodrug is more stable than ester prodrugs. In solution no hydrolysis was observed at pH 7.…”

Design and Synthesis of Fluorescent Acyclic Nucleoside Phosphonates as Potent Inhibitors of Bacterial Adenylate Cyclases

“…[19] Furthermore, 2-substituted PMEA derivatives proved to inhibit B. pertussis ACT, with promising selectivity for ACT over mammalian ACs and no cytotoxicity. [20] It was also shown that cell-permeable bisamidate prodrugs of PMEA bearing bis( l -phenylalanine isopropyl ester) moiety and its 2-substituted derivatives inhibited ACT effectively in cellular models. Although these bisamidate prodrugs did not inhibit ACT in vitro as effectively as bis(POM)PMEA, they were significantly less cytotoxic and showed better plasma stability profiles.…”