Nucleobase Modified Adefovir (PMEA) Analogues as Potent and Selective Inhibitors of Adenylate Cyclases from Bordetella pertussis and Bacillus anthracis

Abstract

A series of 13 acyclic nucleoside phosphonates (ANPs) as bisamidate prodrugs was prepared. Five compounds were found to be non-cytotoxic and selective inhibitors of Bordetella pertussis adenylate cyclase toxin (ACT) in J774A.1 macrophage cell-based assays. The 8-aza-7-deazapurine derivative of adefovir (PMEA) was found to be the most potent ACT inhibitor in the series (IC =16 nm) with substantial selectivity over mammalian adenylate cyclases (mACs). AC inhibitory properties of the most potent analogues were confirmed by direct evaluation of the corresponding phosphonodiphosphates in cell-free assays and were found to be potent inhibitors of both ACT and edema factor (EF) from Bacillus anthracis (IC values ranging from 0.5 to 21 nm). Moreover, 7-halo-7-deazapurine analogues of PMEA were discovered to be potent and selective mammalian AC1 inhibitors (no inhibition of AC2 and AC5) with IC values ranging from 4.1 to 5.6 μm in HEK293 cell-based assays.

Halogen‐Dance‐Based Synthesis of Phosphonomethoxyethyl (PME) Substituted 2‐Aminothiazoles as Potent Inhibitors of Bacterial Adenylate Cyclases

“…Treatment of AC2 with 9 d resulted in a moderate increase in activity, reaching 150 % activity compared to FSK-stimulated control, a phenomenon that has previously been noted with some AC inhibitors. [14,36] Only two compounds inhibited AC5 activity more than 20 %: 9 a and 9 f inhibited this isoform to 79 % and 73 % activity, respectively. Previously described isoform selective inhibitors of AC1 and AC2 were also included as controls and performed as expected: [36,37] the AC1-specific ST034307 reduced activity by over 99 %, and SKF83566, an AC2selective inhibitor, resulted in 85 % inhibition of AC2.…”

“…The best ACT inhibitor from the series proved to be compound 9 d with IC 50 = 490 nM, which was only about three times less potent than phosphonodiamidate prodrug of adefovir I (IC 50 = 147 nM, Table 2). [14] In general, the novel 4-aryl-5-PME-2-aminothiazole analogues 9 a-9 i exhibited somewhat lower potency to inhibit ACT in the cell-based assay compared to previously published regioisomeric 5-aryl-4-PME-2-aminothiazoles (Table 2), [17] with the exception of compound 9 d, (4isopropoxyphenyl)thiazole derivative (IC 50 = 490 nM), which is slightly (1.4 fold) more potent compared to its corresponding regioisomer II (IC 50 = 680 nM). On the other hand, the most potent inhibitor from the previous series was 5-[3-(benzyloxy) phenyl]thiazole derivative (IC 50 = 260 nM, Table 2), [17] while the 4-[3-(benzyloxy)phenyl]thiazole regioisomer 9 c from the current study was inactive (IC 50 > 10 μM, Table 2).…”

“…[11] Furthermore PMEApp and its mimics were shown to inhibit ACs derived from rat brain. [12] Subsequently, an extensive structure-activity relationship study was performed with structurally modified adefovir (PMEA) analogues as inhibitors of bacterial adenylate cyclase toxins: the SAR study covered adefovir derivatives modified either at the nucleobase [13,14] or at the aliphatic moiety. [15,16] Some of the compounds also exhibited an ability to selectively modulate mammalian ACs (especially AC1), with an anticipated potential for development of non-opioid alternatives for the treatment of inflammatory and neuropathic pain.…”

“…[15,16] Some of the compounds also exhibited an ability to selectively modulate mammalian ACs (especially AC1), with an anticipated potential for development of non-opioid alternatives for the treatment of inflammatory and neuropathic pain. [14] It has been recently reported, [17] that the adenine moiety in adefovir could be replaced by another heterocycle that is able to mimic the adenine nucleobase, namely 2-aminothiazole, leading to compounds II (Figure 2). The design of such compounds was based on compound MB05032 (Figure 2), [18][19][20][21] a potent and selective inhibitor of fructose 1,6-bisphosphatase (FBPase).…”

Structural Biology and Molecular Modeling to Analyze the Entry of Bacterial Toxins and Virulence Factors into Host Cells

“…Search for inhibitors of edema factor have been also performed [102,107,108,109,110,111,112,113,114] and are reviewed in [113]. Some compounds are active against both CyaA and EF [115,116]. Monoclonal antibodies were raised against EF [117].…”