Inhibitors of Leishmania GDP-mannose pyrophosphorylase identified by high-throughput screening of small-molecule chemical library.
The current treatment for leishmaniasis is based on chemotherapy, which relies on a handful of drugs with serious limitations, such as high cost, toxicity, and a lack of efficacy in regions of endemicity. Therefore, the development of new, effective, and affordable antileishmanial drugs is a global health priority. Leishmania synthesizes a range of mannose-rich glycoconjugates that are essential for parasite virulence and survival. A prerequisite for glycoconjugate biosynthesis is the conversion of monosaccharides to the activated mannose donor, GDP-mannose, the product of a reaction catalyzed by GDP-mannose pyrophosphorylase (GDP-MP). The deletion of the gene encoding GDP-MP in Leishmania led to a total loss of virulence, indicating that the enzyme is an ideal drug target. We developed a phosphate sensor-based high-throughput screening assay to quantify the activity of GDP-MP and screened a library containing approximately 80,000 lead-like compounds for GDP-MP inhibitors. On the basis of their GDP-MP inhibitory properties and chemical structures, the activities of 20 compounds which were not toxic to mammalian cells were tested against ex vivo amastigotes and in macrophage amastigote assays. The most potent compound identified in the primary screen (compound 3), a quinoline derivative, demonstrated dose-dependent activity in both assays (50% inhibitory concentration = 21.9 microM in the macrophage assay) and was shown to be nontoxic to human fibroblasts. In order to elucidate signs of an early structure-activity relationship (SAR) for this class of compounds, we obtained and tested analogues of compound 3 and undertook limited medicinal chemistry optimization, which included the use of a number of SAR probes of the piperazinyl aryl substituent of compound 3. We have identified novel candidate compounds for the design and synthesis of antileishmanial therapeutics.
High-Throughput Chemical Screening Facility, Structural Biology Division, Walter+Eliza Hall Institute of Medical Research, Melbourne, Australia.
Kurt
K
Lackovic
John P
JP
Parisot
Nerida
N
Sleebs
Jonathan B
JB
Baell
Laurent
L
Debien
Keith G
KG
Watson
Joan M
JM
Curtis
Emanuela
E
Handman
Ian P
IP
Street
Lukasz
L
Kedzierski
D000981:Antiprotozoal Agents / Q000737:chemistry / Q000494:pharmacology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000469:parasitology; D006801:Humans; D018320:Leishmania major / Q000187:drug effects* / Q000201:enzymology; D016773:Leishmaniasis, Cutaneous / Q000188:drug therapy* / Q000469:parasitology; D009713:Nucleotidyltransferases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D054852:Small Molecule Libraries; D013830:Thiadiazoles / Q000494:pharmacology
D000981:Antiprotozoal Agents; D004791:Enzyme Inhibitors; D011720:Pyrazoles; D011804:Quinolines; D054852:Small Molecule Libraries; D013830:Thiadiazoles; C443742:pyrazolidine-3,5-dione; D009713:Nucleotidyltransferases; C026917:mannose 1-phosphate guanylyltransferase