Targeting inactive enzyme conformation: aryl diketoacid derivatives as a new class of PTP1B inhibitors

There has been considerable interest in protein tyrosine phosphatase 1B (PTP1B) as a therapeutic target for diabetes, obesity, as well as cancer. Identifying inhibitory compounds with good bioavailability is a major challenge of drug discovery programs targeted toward PTPs. Most current PTP active site-directed pharmacophores are negatively charged pTyr mimetics which cannot readily enter the cell. This lack of cell permeability limits the utility of such compounds in signaling studies and further therapeutic development. We identify aryl diketoacids as novel pTyr surrogates and show that neutral amide-linked aryl diketoacid dimers also exhibit excellent PTP inhibitory activity. Kinetic studies establish that these aryl diketoacid derivatives act as noncompetitive inhibitors of PTP1B. Crystal structures of ligand-bound PTP1B reveal that both the aryl diketoacid and its dimeric derivative bind PTP1B at the active site, albeit with distinct modes of interaction, in the catalytically inactive, WPD loop open conformation. Furthermore, dimeric aryl diketoacids are cell permeable and enhance insulin signaling in hepatoma cells, suggesting that targeting the inactive conformation may provide a unique opportunity for creating active site-directed PTP1B inhibitors with improved pharmacological properties.

Novel dimeric aryldiketo containing inhibitors of HIV-1 integrase: effects of the phenyl substituent and the linker orientation

Aryl diketoacids (ADK) and their bioisosteres are among the most promising HIV-1 integrase (IN) inhibitors. Previously, we designed a series of ADK dimers as a new class of IN inhibitors that were hypothesized to target two divalent metal ions on the active site of IN. Herein we present a further structure-activity relationship (SAR) study with respect to the substituent effect of the ADK and the dimerization with conformationally constrained linkers such as piperazine, 4-amino-piperidine, piperidin-4-ol, and trans-cyclohexan-1,4-diamine. The substituents on the phenyl ring as well as the spatial orientation of the two diketo units were observed to play important roles in the IN inhibitory potency. The hydrophobic group was an optimal substitution at the 3-position of the aryl ring. The piperazine and 4-amino-piperidine linkers brought about the most potent analogs among the hydrophobic group or halogen substituted ADK dimers. The docking studies suggested that the bulky hydrophobic substitution at 3-phenyl ring and the linker of 4-amino-piperidine were beneficial for adopting an active conformation to achieve strong interactions with the active site Mg(2+) and the key residue E152 within the catalytic core domain. This study is a significant extension of our previous report on the dimeric ADK-containing IN inhibitors, providing a new promising template for further lead optimization.