Discovery of Small Molecule Inhibitors of Neutral Sphingomyelinase 2 (nSMase2) for the Treatment of Neurodegenerative Diseases

Unmet Need
In the brain, neutral sphingomyelinase 2 (nSMase2) is expressed in neurons and increased activity and expression of this enzyme has been associated with pro-inflammatory conditions observed in Alzheimer’s disease, multiple sclerosis and human immunodeficiency virus (HIV-1) patients. Inhibition of human nSMase2 may preserve neuronal function by preventing increases in ceramide, and/or blocking exosome production and as a consequence decreasing cell death.  A number of nSMase inhibitors have been identified, but these compounds have molecular characteristics that make them poor drug candidates including a lack of specificity, low potency, and undesirable physicochemical properties that reduce drug-likeness and blood brain barrier penetration.  However, there are no soluble, specific and potent small molecule inhibitor tool compounds for in vivo studies or as a starting point for medicinal chemistry optimization.
 
Technology Overview
JHU researchers developed and optimized two activity assays using a recombinant human nSmase2 protein to identify more drug-like nSMase2 inhibitors.  Their research identified Cambinol and eight cambinol analogues.  Cambinol is a novel uncompetitive inhibitor of human nSMase2 and when compared to GW4869, the most extensively used prototype, it has similar potency but exhibits significantly higher aqueous solubility and lower molecular weight (MW). When compared to inhibitors with similar MW (e.g. altenusin, C11AG or macquarimicin A), cambinol is a more potent inhibitor. Cambinol’s mode of inhibition and the lack of time-dependence of its IC50 value indicate that cambinol does not bind to the substrate binding site of the enzyme but rather to an alternative site blocking activity and it does so reversibly.  Furthermore, in vivo studies revealed cambinol decreased ceramide levels and protected neurons from cell death and dendritic damage. 
 
Stage of Development
Pharmacologically active compounds and approved drugs were screened using this strategy which led to the identification of cambinol as a novel uncompetitive nSMase2 inhibitor (Ki = 7 μM). The inhibitory activity of cambinol for nSMase2 was approximately 10-fold more potent than for its previously known target. Cambinol decreased tumor necrosis factor-α or interleukin-1 β-induced increases of ceramide and cell death in primary neurons.  A preliminary study of cambinol structure and activity allowed the identification of the main structural features required for nSMase2 inhibition. Cambinol and its analogs may be useful as nSMase2 inhibitor tool compounds to prevent ceramide-dependent neurodegeneration.

Publications
PLoS ONE 10(5): e0124481
 

Category(s):