Parasites of the Plasmodium genus are unable to produce purine nucleotides de novo and depend completely on the salvage pathway. This fact makes plasmodial hypoxanthine-guanine-(xanthine) phosphoribosyltransferase [HG(X)PRT] a valuable target for development of antimalarial agents. A series of nucleotide analogues was designed, synthesized and evaluated as potential inhibitors of Plasmodium falciparum HGXPRT, P. vivax HGPRT and human HGPRT. These novel nucleoside phosphonates have a pyrrolidine, piperidine or piperazine ring incorporated into the linker connecting the purine base to a phosphonate group(s) and exhibited a broad range of Ki values between 0.15 and 72 μM. The corresponding phosphoramidate prodrugs, able to cross cell membranes, have been synthesized and evaluated in a P. falciparum infected human erythrocyte assay. Of the eight prodrugs evaluated seven exhibited in vitro antimalarial activity with IC50 values within the range of 2.5-12.1 μM. The bis-phosphoramidate prodrug 13a with a mean (SD) IC50 of 2.5 ± 0.7 μM against the chloroquine-resistant P. falciparum W2 strain exhibited low cytotoxicity in the human hepatocellular liver carcinoma (HepG2) and normal human dermal fibroblasts (NHDF) cell lines at a concentration of 100 μM suggesting good selectivity for further structure-activity relationship investigations.
- MeSH
- antimalarika chemická syntéza metabolismus farmakologie MeSH
- buněčné linie MeSH
- erytrocyty cytologie metabolismus parazitologie MeSH
- inhibitory enzymů chemie metabolismus MeSH
- léková rezistence účinky léků MeSH
- lidé MeSH
- nukleotidy chemie metabolismus MeSH
- pentosyltransferasy antagonisté a inhibitory metabolismus MeSH
- piperazin chemie MeSH
- piperidiny chemie MeSH
- Plasmodium falciparum účinky léků enzymologie MeSH
- Plasmodium vivax enzymologie MeSH
- preklinické hodnocení léčiv MeSH
- prekurzory léčiv chemická syntéza chemie metabolismus farmakologie MeSH
- protozoální proteiny antagonisté a inhibitory metabolismus MeSH
- pyrrolidiny chemie MeSH
- viabilita buněk účinky léků MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) are the foremost causative agents of malaria. Due to the development of resistance to current antimalarial medications, new drugs for this parasitic disease need to be discovered. The activity of hypoxanthine-guanine-[xanthine]-phosphoribosyltransferase, HG[X]PRT, is reported to be essential for the growth of both of these parasites, making it an excellent target for antimalarial drug discovery. Here, we have used rational structure-based methods to design an inhibitor, [3R,4R]-4-guanin-9-yl-3-((S)-2-hydroxy-2-phosphonoethyl)oxy-1-N-(phosphonopropionyl)pyrrolidine, of PvHGPRT and PfHGXPRT that has Ki values of 8 and 7 nM, respectively, for these two enzymes. The crystal structure of PvHGPRT in complex with this compound has been determined to 2.85 Å resolution. The corresponding complex with human HGPRT was also obtained to allow a direct comparison of the binding modes of this compound with the two enzymes. The tetra-(ethyl l-phenylalanine) tetraamide prodrug of this compound was synthesized, and it has an IC50 of 11.7 ± 3.2 μM against Pf lines grown in culture and a CC50 in human A549 cell lines of 102 ± 11 μM, thus giving it a ∼10-fold selectivity index.
- MeSH
- antimalarika chemie farmakologie MeSH
- bisfosfonáty chemie farmakologie MeSH
- hypoxanthinfosforibosyltransferasa antagonisté a inhibitory chemie metabolismus MeSH
- katalytická doména MeSH
- konformace proteinů MeSH
- krystalografie rentgenová MeSH
- lidé MeSH
- molekulární modely MeSH
- pentosyltransferasy antagonisté a inhibitory chemie metabolismus MeSH
- Plasmodium vivax enzymologie MeSH
- proteiny z Escherichia coli chemie MeSH
- racionální návrh léčiv MeSH
- techniky syntetické chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Acyclic nucleoside phosphonates (ANPs) are an important class of therapeutic drugs that act as antiviral agents by inhibiting viral DNA polymerases and reverse transcriptases. ANPs containing a 6-oxopurine unit instead of a 6-aminopurine or pyrimidine base are inhibitors of the purine salvage enzyme, hypoxanthine-guanine-[xanthine] phosphoribosyltransferase (HG[X]PRT). Such compounds, and their prodrugs, are able to arrest the growth of Plasmodium falciparum (Pf) in cell culture. A new series of ANPs were synthesized and tested as inhibitors of human HGPRT, PfHGXPRT, and Plasmodium vivax (Pv) HGPRT. The novelty of these compounds is that they contain a five-membered heterocycle (imidazoline, imidazole, or triazole) inserted between the acyclic linker(s) and the nucleobase, namely, 9-deazahypoxanthine. Five of the compounds were found to be micromolar inhibitors of PfHGXPRT and PvHGPRT, but no inhibition of human HGPRT was observed under the same assay conditions. This demonstrates selectivity of these types of compounds for the two parasitic enzymes compared to the human counterpart and confirms the importance of the chemical nature of the acyclic moiety in conferring affinity/selectivity for these three enzymes.
- MeSH
- antimalarika chemická syntéza chemie MeSH
- hypoxanthinfosforibosyltransferasa antagonisté a inhibitory MeSH
- hypoxanthiny chemie MeSH
- lidé MeSH
- molekulární modely MeSH
- nukleosidy chemická syntéza chemie MeSH
- organofosfonáty chemická syntéza chemie MeSH
- pentosyltransferasy antagonisté a inhibitory MeSH
- Plasmodium falciparum enzymologie MeSH
- Plasmodium vivax enzymologie MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
6-Oxopurine acyclic nucleoside phosphonates (ANPs) have been shown to be potent inhibitors of hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRT), a key enzyme of the purine salvage pathway in human malarial parasites. These compounds also exhibit antimalarial activity against parasites grown in culture. Here, a new series of ANPs, hypoxanthine and guanine 9-[2-hydroxy-3-(phosphonomethoxy)propyl] derivatives with different chemical substitutions in the 2'-position of the aliphatic chain were prepared and tested as inhibitors of Plasmodium falciparum (Pf) HGXPRT, Plasmodium vivax (Pv) HGPRT and human HGPRT. The attachment of an hydroxyl group to this position and the movement of the oxygen by one atom distal from N(9) in the purine ring compared with 2-(phosphonoethoxy)ethyl hypoxanthine (PEEHx) and 2-(phosphonoethoxy)ethyl guanine (PEEG) changes the affinity and selectivity for human HGPRT, PfHGXPRT and PvHGPRT. This is attributed to the differences in the three-dimensional structure of these inhibitors which affects their mode of binding. A novel observation is that these molecules are not always strictly competitive with 5-phospho-α-d-ribosyl-1-pyrophosphate. 9-[2-Hydroxy-3-(phosphonomethoxy)propyl]hypoxanthine (iso-HPMP-Hx) is a very weak inhibitor of human HGPRT but remains a good inhibitor of both the parasite enzymes with K(i) values of 2μM and 5μM for PfHGXPRT and PvHGPRT, respectively. The addition of pyrophosphate to the assay decreased the K(i) values for the parasite enzymes by sixfold. This suggests that the covalent attachment of a second group to the ANPs mimicking pyrophosphate and occupying its binding pocket could increase the affinity for these enzymes.
- MeSH
- antimalarika chemická syntéza chemie farmakologie MeSH
- hypoxanthinfosforibosyltransferasa antagonisté a inhibitory metabolismus MeSH
- inhibitory enzymů chemická syntéza chemie farmakologie MeSH
- lidé MeSH
- malárie farmakoterapie enzymologie MeSH
- molekulární modely MeSH
- pentosyltransferasy antagonisté a inhibitory metabolismus MeSH
- Plasmodium falciparum účinky léků enzymologie MeSH
- Plasmodium vivax účinky léků enzymologie MeSH
- puriny chemická syntéza chemie farmakologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The purine salvage enzyme, hypoxanthine-guanine-(xanthine) phosphoribosyltransferase [HG(X)PRT], catalyses the synthesis of the purine nucleoside monophosphates, IMP, GMP or XMP essential for DNA/RNA production. In protozoan parasites, such as Plasmodium, this is the only route available for their synthesis as they lack the de novo pathway which is present in human cells. Acyclic nucleoside phosphonates (ANPs), analogs of the purine nucleoside monophosphates, have been found to inhibit Plasmodium falciparum (Pf) HGXPRT and Plasmodium vivax (Pv) HGPRT with K(i) values as low as 100 nM. They arrest parasitemia in cell based assays with IC(50) values of the order of 1-10 μM. ANPs with phosphonoalkyl and phosphonoalkoxyalkyl moieties linking the purine base and phosphonate group were designed and synthesised to evaluate the influence of this linker on the potency and/or selectivity of the ANPs for the human and malarial enzymes. This data shows that variability in the linker, as well as the positioning of the oxygen in this linker, influences binding. The human enzyme binds the ANPs with K(i) values of 0.5 μM when the number of atoms in the linker was 5 or 6 atoms. However, the parasite enzymes have little affinity for such long chains unless oxygen is included in the three-position. In comparison, all three enzymes have little affinity for ANPs where the number of atoms linking the base and the phosphonate group is of the order of 2-3 atoms. The chemical nature of the purine base also effects the K(i) values. This data shows that both the linker and the purine base play an important role in the binding of the ANPs to these three enzymes.
- MeSH
- aktivace enzymů účinky léků MeSH
- antimalarika chemická syntéza chemie farmakologie MeSH
- kinetika MeSH
- lidé MeSH
- pentosyltransferasy antagonisté a inhibitory genetika metabolismus MeSH
- Plasmodium falciparum účinky léků enzymologie MeSH
- Plasmodium vivax účinky léků enzymologie MeSH
- protozoální proteiny antagonisté a inhibitory genetika metabolismus MeSH
- puriny chemická syntéza chemie farmakologie MeSH
- rekombinantní proteiny antagonisté a inhibitory genetika metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Hypoxanthine-guanine-(xanthine) phosphoribosyltransferase (HG(X)PRT) is crucial for the survival of malarial parasites Plasmodium falciparum (Pf) and Plasmodium vivax (Pv). Acyclic nucleoside phosphonates (ANPs) are inhibitors of HG(X)PRT and arrest the growth of Pf in cell culture. Here, a novel class of ANPs containing trisubstituted nitrogen (aza-ANPs) has been synthesized. These compounds have a wide range of K(i) values and selectivity for human HGPRT, PfHGXPRT, and PvHGPRT. The most selective and potent inhibitor of PfHGXPRT is 9-[N-(3-methoxy-3-oxopropyl)-N-(2-phosphonoethyl)-2-aminoethyl]hypoxanthine (K(i) = 100 nM): no inhibition could be detected against the human enzyme. This compound exhibits the highest ever reported selectivity for PfHGXPRT compared to human HGPRT. For PvHGPRT, 9-[N-(2-carboxyethyl)-N-(2-phosphonoethyl)-2-aminoethyl]guanine has a K(i) of 50 nM, the best inhibitor discovered for this enzyme to date. Docking of these compounds into the known structures of human HGPRT in complex with ANP-based inhibitors suggests reasons for the variations in affinity, providing insights for the design of antimalarial drug candidates.
- MeSH
- antimalarika chemická syntéza chemie farmakologie MeSH
- hypoxanthinfosforibosyltransferasa antagonisté a inhibitory MeSH
- inhibitory enzymů chemická syntéza chemie farmakologie MeSH
- lidé MeSH
- malárie farmakoterapie MeSH
- molekulární konformace MeSH
- molekulární modely MeSH
- nukleosidy chemická syntéza chemie farmakologie MeSH
- organofosfonáty farmakologie chemická syntéza chemie MeSH
- pentosyltransferasy antagonisté a inhibitory MeSH
- Plasmodium falciparum účinky léků enzymologie MeSH
- Plasmodium vivax účinky léků enzymologie MeSH
- racionální návrh léčiv MeSH
- substrátová specifita MeSH
- vazba proteinů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
