Uncharged isocoumarin-based inhibitors of urokinase-type plasminogen activator

BACKGROUND: Urokinase-type plasminogen activator (uPA) plays a major role in extracellular proteolytic events associated with tumor cell growth, migration and angiogenesis. Consequently, uPA is an attractive target for the development of small molecule active site inhibitors. Most of the recent drug development programs aimed at nonpeptidic inhibitors targeted at uPA have focused on arginino mimetics containing amidine or guanidine functional groups attached to aromatic or heterocyclic scaffolds. There is a general problem of limited bioavailability of these charged inhibitors. In the present study, uPA inhibitors were designed on an isocoumarin scaffold containing uncharged substituents. RESULTS: 4-Chloro-3-alkoxyisocoumarins were synthesized in which the 3-alkoxy group contained a terminal bromine; these were compared with similar inhibitors that contained a charged terminal functional group. Additional variations included functional groups attached to the seven position of the isocoumarin scaffold. N- [3-(3-Bromopropoxy)-4-chloro-1-oxo-1H-isochromen-7-yl]benzamide was identified as an uncharged lead inhibitor of uPA, K(i )= 0.034 μM. Molecular modeling of human uPA with these uncharged inhibitors suggests that the bromine occupies the same position as positively charged arginino mimetic groups. CONCLUSION: This study demonstrates that potent uncharged inhibitors of uPA can be developed based upon the isocoumarin scaffold. A tethered bromine in the three position and an aromatic group in the seven position are important contributors to binding. Although the aim was to develop compounds that act as mechanism-based inactivators, these inhibitors are competitive reversible inhibitors

Inhibition of pancreatic cholesterol esterase reduces cholesterol absorption in the hamster

BACKGROUND: Pancreatic cholesterol esterase has three proposed functions in the intestine: 1) to control the bioavailability of cholesterol from dietary cholesterol esters; 2) to contribute to incorporation of cholesterol into mixed micelles; and 3) to aid in transport of free cholesterol to the enterocyte. Inhibitors of cholesterol esterase are anticipated to limit the absorption of dietary cholesterol. RESULTS: The selective and potent cholesterol esterase inhibitor 6-chloro-3-(1-ethyl-2-cyclohexyl)-2-pyrone (figure 1, structure 1) was administered to hamsters fed a high cholesterol diet supplemented with radiolabeled cholesterol ester. Hamsters were gavage fed (3)H-labeled cholesteryl oleate along with inhibitor 1, 0–200 micromoles. Twenty-four hours later, hepatic and serum radioactive cholesterol levels were determined. The ED(50 )of inhibitor 1 for prevention of the uptake of labeled cholesterol derived from hydrolysis of labeled cholesteryl oleate was 100 micromoles. The toxicity of inhibitor 1 was investigated in a 30 day feeding trial. Inhibitor 1, 100 micromoles or 200 micromoles per day, was added to chow supplemented with 1% cholesterol and 0.5% cholic acid. Clinical chemistry urinalysis and tissue histopathology were obtained. No toxicity differences were noted between control and inhibitor supplemented groups. CONCLUSIONS: Inhibitors of cholesterol esterase may be useful therapeutics for limiting cholesterol absorption

A Chemical Analog of Curcumin as an Improved Inhibitor of Amyloid Abeta Oligomerization

Amyloid-like plaques are characteristic lesions defining the neuropathology of Alzheimer's disease (AD). The size and density of these plaques are closely associated with cognitive decline. To combat this disease, the few therapies that are available rely on drugs that increase neurotransmission; however, this approach has had limited success as it has simply slowed an imminent decline and failed to target the root cause of AD. Amyloid-like deposits result from aggregation of the Aβ peptide, and thus, reducing amyloid burden by preventing Aβ aggregation represents an attractive approach to improve the therapeutic arsenal for AD. Recent studies have shown that the natural product curcumin is capable of crossing the blood-brain barrier in the CNS in sufficient quantities so as to reduce amyloid plaque burden. Based upon this bioactivity, we hypothesized that curcumin presents molecular features that make it an excellent lead compound for the development of more effective inhibitors of Aβ aggregation. To explore this hypothesis, we screened a library of curcumin analogs and identified structural features that contribute to the anti-oligomerization activity of curcumin and its analogs. First, at least one enone group in the spacer between aryl rings is necessary for measureable anti-Aβ aggregation activity. Second, an unsaturated carbon spacer between aryl rings is essential for inhibitory activity, as none of the saturated carbon spacers showed any margin of improvement over that of native curcumin. Third, methoxyl and hydroxyl substitutions in the meta- and para-positions on the aryl rings appear necessary for some measure of improved inhibitory activity. The best lead inhibitors have either their meta- and para-substituted methoxyl and hydroxyl groups reversed from that of curcumin or methoxyl or hydroxyl groups placed in both positions. The simple substitution of the para-hydroxy group on curcumin with a methoxy substitution improved inhibitor function by 6-7-fold over that measured for curcumin