Design, Synthesis, and Biological Evaluation of Halogenated N-(2-(4-Oxo-1-phenyl-1,3,8-triazaspiro[4.5]decan-8-yl)ethyl)benzamides: Discovery of an Isoform-Selective Small Molecule Phospholipase D2 Inhibitor

Abstract

Phospholipase D (PLD) catalyzes the conversion of phosphatidylcholine to the lipid second messenger phosphatidic acid. Two mammalian isoforms of PLD have been identified, PLD1 and PLD2, which share 53% sequence identity and are subject to different regulatory mechanisms. Inhibition of PLD enzymatic activity leads to increased cancer cell apoptosis, decreased cancer cell invasion and decreased metastasis of cancer cells; therefore, the development of isoform-specific, PLD inhibitors is a novel approach for the treatment of cancer. Previously, we developed potent dual PLD1/PLD2, PLD1-specific (>1,700-fold selective) and moderately PLD2 preferring (>10-fold preferring) inhibitors. Here, we describe a matrix library strategy that afforded the most potent (PLD2 IC50 = 20 nM) and selective (75-fold selective versus PLD1) PLD2 inhibitor to date, N-(2(1-(3-fluorophenyl)-4-oxo-1,3,8-triazaspiro[4.5]decan-8-yl)ethyl)-2-naphthamide (22a), with an acceptable DMPK profile. Thus, these new isoform-selective PLD inhibitors will enable researchers to dissect the signaling roles and therapeutic potential of individual PLD isoforms to an unprecedented degree.

Further evaluation of novel structural modifications to scaffolds that engender PLD isoform selective inhibition

“…7,8 This was a general finding within this series, and the magnitude of the impact of PLD1 activity exceeded 230-fold ( Fig. 2 ) within the ML298 ( 4 ) molecule, ( S )- 5 .…”

Drugs for Allosteric Sites on Receptors

“…The benzimidazolone core favored PLD1 inhibition, and a chiral ( S )-methyl group on the ethylene diamine linkers further enhanced PLD1 inhibition. Preferential PLD2 inhibition could be achieved with a bioisoteric triazaspirone scaffold, leading to the compound VU0364739 ( 17 , Figure 5 c ), which displays a 75-fold preference for inhibition of PLD2 over PLD1 (55, 56). Both VU0359595 and VU0364739 ( 16 and 17 , Figure 5 c ), as well as more advanced PLD inhibitors in these series (57), displayed significantly improved drug metabolism and pharmacokinetic properties while eliminating biogenic amine activity.…”

Chemical modulation of glycerolipid signaling and metabolic pathways

“…Lavieri et al reported the most potent and selective PLD2-preferring compound, VU0364739, which displays 75-fold selectivity for PLD2 over PLD1 with nanomolar potency (PLD2 IC 50 of 20 nM)(Fig. 2B) [86]. Since this study, we identified PLD2-preferring compounds with lower PLD2 potency and minimal PLD1 activity; these compounds also have improved overall ancillary pharmacology (VU0285655 and ML298) [87, 88].…”