Background Dengue fever, dengue hemorrhagic fever, and dengue shock syndrome are caused by infections with any of the four serotypes of the dengue virus (DENV) and are an increasing global health risk. The related West Nile Virus (WNV) causes significant morbidity and mortality as well and continues to be a threat in endemic areas. Currently no FDA approved vaccines or therapeutics are available to prevent or treat any of these infections. Like the other members of the Flaviviridae family, DENV and WNV encode a protease (NS3) which is essential for viral replication and therefore is a promising target for developing therapies to treat dengue and West Nile infections. Methods Flaviviral protease inhibitors were identified and biologically characterized for mechanism of inhibition and DENV anti-viral activity. Results A guanidinylated 2, 5-dideoxystreptamine class of compounds was identified that competitively inhibited the NS3 protease from DENV(1-4) and WNV with IC50 values in the 1-70 μM range. Cytotoxicity was low; however, antiviral activity versus DENV-2 on VERO cells was not detectable. Conclusions This class of compounds is the first to demonstrate competitive pan-dengue and WNV NS3 protease inhibition and, given the sequence conservation among flavivirus NS3 proteins, suggests that developing a pan-dengue or possibly pan-flavivirus therapeutic is feasible.

Neurotoxins synthesized by Clostridium botulinum bacteria (BoNT), the etiological agent of human botulism, are extremely toxic proteins making them high-risk agents for bioterrorism. Small molecule inhibitor development has been focused on the light chain zinc-dependent metalloprotease domain of the neurotoxin, an effort that has been hampered by its relatively flexible active site. Developed in concert with structure-activity relationship studies, the X-ray crystal structures of the complex of BoNT serotype A light chain (BoNT/A LC) with three different micromolar potency hydroxamate-based inhibitors are reported here. Comparison with an unliganded BoNT/A LC structure reveals significant changes in the active site as a result of binding by the unique inhibitor scaffolds. The 60/70 loop at the opening of the active site pocket undergoes the largest conformational change, presumably through an induced-fit mechanism, resulting in the most compact catalytic pocket observed in all known BoNT/A LC structures.

Four core structures capable of providing sub-nanomolar inhibitors of anthrax lethal factor (LF) were evaluated by comparing the potential for toxicity, physicochemical properties, in vitro ADME profiles, and relative efficacy in a rat lethal toxin (LT) model of LF intoxication. Poor efficacy in the rat LT model exhibited by the phenoxyacetic acid series (3) correlated with low rat microsome and plasma stability. Specific molecular interactions contributing to the high affinity of inhibitors with a secondary amine in the C2-side chain were revealed by x-ray crystallography.