Discovery of a Highly Selective PLD2 Inhibitor (ML395): A New Probe with Improved Physiochemical Properties and Broad‐Spectrum Antiviral Activity against Influenza Strains

Abstract

Further chemical optimization of the halopemide-derived family of dual PLD1/2 inhibitors afforded ML395 (VU0468809), a potent, >80-fold PLD2 selective allosteric inhibitor (cellular PLD1, IC50 >30,000 nM, cellular PLD2, IC50 = 360 nM). Moreover, ML395 possesses an attractive in vitro DMPK profile, improved physiochemical properties, ancillary pharmacology (Eurofins Panel) cleaner than any other reported PLD inhibitor, and has been found to possess interesting activity as an antiviral agent in cellular assays against a range of influenza strains (H1, H3, H5 and H7).

Targeting phospholipase D in cancer, infection and neurodegenerative disorders

“…However, halopemide was not a panacea. Many laboratories began to use both halopemide and FIPI as key proof-of-concept tools for PLD1 and PLD2 target validation, which led to potentially flawed conclusions, as both compounds display a considerable amount of ancillary pharmacology at a multitude of biogenic amine receptors, as expected for atypical antipsychotics that have GPCR-privileged structures as a core motif 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 .…”

“…Within the piperidine benzimidazolone core analogues, preference for PLD2 was elusive; thus, a number of bioisosteres of the piperidine benzimidazolone, as well as alternative GPCR-privileged structures, were surveyed 26 , 27 , 28 , 29 , 30 . The structure–activity relationship (SARs) of these compounds were shallow, and more than 99% of the variants studied were devoid of PLD-inhibitory activity; however, an N -phenyl triazaspirone congener ( Fig.…”

“…Initial studies with halopemide and FIPI in assays using a PLD1.d311 truncation construct (which lacked a portion of the pleckstrin homology domain) showed a slight reduction of PLD activity 16 ; however, both VU0359595 and VU0364739 significantly reduced PLD activity (by more than tenfold), which suggests that the pleckstrin homology domain (a domain that is far away from the HKD catalytic active site) is key for the binding of these molecules. Additional enzyme kinetic studies further increased our confidence that these compounds were allosteric 16 , 25 , 26 , 27 , 28 , 29 , 30 . Using a backscattering interferometry technique 33 , it was found that VU0359595 binds to two sites on the PLD1 protein (one with high affinity and the other with low affinity) 34 , which further supports an allosteric mode of inhibition akin to that of allosteric AKT inhibitors 31 , 32 .…”

Progress of small molecular inhibitors in the development of anti-influenza virus agents

“…Phospholipase inhibitors: Phospholipase D (PLD) is one kind of phospholipase that catalyzes the formation of phosphatidic acid, an important messenger in signaling and metabolic pathways (289). Recent studies show that human PLD2 inhibitor such as ML395 (Figure 20) possess a broad-spectrum inhibitory against influenza strains (290).…”

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

“…1,2,5,6 This series was plagued with ancillary pharmacology, due to the GPCR privileged structure, and poor metaboic stability (MET ID indicated oxidative metabolism on the central piperidine ring). 5,6,9 In an attempt to address these issues, we elected to install a methyl group α to the piperidine nitrogen to block oxidative metabolism (as in 9 and 10 ), as well as a β-fluorine atom (as in 11 ) to modulate pK a and potentially improve ancillary pharmacology at biogenic amine targets. The requisite functionalized piperidine benzimidazolones were prepared as previously described following literature routes 5,6,14 and then elaborated via a reported variation on Scheme 1.…”