Simplified Analogues of Immucillin-G Retain Potent Human Purine Nucleoside Phosphorylase Inhibitory Activity

A set of deazaguanine derivatives 1-3 targeting human purine nucleoside phosphorylase (hPNP) have been designed and synthesized. The new compounds are characterized by the presence of a structurally simplified "azasugar" motif to be more easily accessible by chemical synthesis than previous inhibitors. In the enzymatic assays, some of the new derivatives proved to be able to inhibit hPNP at low nanomolar concentration, thereby showing the same inhibitory potency in vitro as immucillin-H (IMH). Molecular docking experiments revealed a binding mode to hPNP essentially identical to that of IMH. As a result, the lower in vivo activity exhibited by 1d, compared with that exhibited by IMH, might be ascribed to differences in the pharmacokinetic, rather than pharmacodynamic, profile between these compounds. Derivatives 1a, 1d, and 2c emerged as the most active compounds within this new set and may represent interesting leads in the search for novel hPNP inhibitors

Studies on the ATP Binding Site of Fyn Kinase for the Identification of New Inhibitors and Their Evaluation as Potential Agents against Tauopathies and Tumors

Fyn is a member of the Src-family of nonreceptor protein-tyrosine kinases. Its abnormal activity has been shown to be related to various human cancers as well as to severe pathologies,; such as Alzheimer's and Parkinson's diseases. Herein, a structure-based drug design protocol was employed aimed at identifying novel Fyn inhibitors. Two hits from commercial sources (1, 2) were found active against Fyn with K-i of about 2 mu M, while derivative 4a, derived from our internal library, showed a K-i of 0.9 mu M. A hit-to-lead optimization effort was then initiated on derivative 4a to improve its potency. Slightly modifications rapidly determine an increase in the binding affinity, with the best inhibitors 4c and 44 having K(i)s of 70 and 95 nM, respectively. Both compounds were found able to inhibit the phosphorylation of : the protein Tau in an Alzheimer's model cell line and showed antiproliferative activities against different cancer cell lines