1,3-disubstituted-4-aminopyrazolo [3, 4-d] pyrimidines, a new class of potent inhibitors for phospholipase D

Phospholipase D enzymes cleave lipid substrates to produce phosphatidic acid, an important precursor for many essential cellular molecules. Phospholipase D is a target to modulate cancer-cell invasiveness. This study reports synthesis of a new class of phospholipase D inhibitors based on 1,3-disubstituted-4-amino-pyrazolopyrimidine core structure. These molecules were synthesized and used to perform initial screening for the inhibition of purified bacterial phospholipase D, which is highly homologous to the human PLD₁. Initially tested with the bacterial phospholipase D enzyme, then confirmed with the recombinant human PLD₁ and PLD₂ enzymes, the molecules presented here exhibited inhibition of phospholipase D activity (IC₅₀) in the low-nanomolar to low-micromolar range with both monomeric substrate diC₄PC and phospholipid vesicles and micelles. The data strongly indicate that these inhibitory molecules directly block enzyme/vesicle substrate binding. Preliminary activity studies using recombinant human phospholipase Ds in in vivo cell assays measuring both transphosphatidylation and head-group cleavage indicate inhibition in the mid- to low-nanomolar range for these potent inhibitory novel molecules in a physiological environment. This study reports synthesis of a new class of PLD inhibitors based on 1,3-disubstituted-4-amino-pyrazolopyrimidine core structure. These molecules exhibited inhibition of human recombinant PLD activity (IC ₅₀) in the low-nanomolar to low-micromolar range with monomeric substrate diC4PC and phospholipid vesicles and micelles. Preliminary activity studies using recombinant human PLDs in in vivo cell assays measuring both transphosphatidylation and head-group cleavage indicates inhibition in the mid- to low-nanomolar range for these potent inhibitory novel molecules in a physiological environment.