A Bioinorganic Approach to Anthrax Lethal Factor Inhibitors

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DESCRIPTION (provided by applicant): The major objective of this proposal is to develop novel inhibitors of anthrax lethal factor (LF) by using a comprehensive bioinorganic approach that allows for the mechanistic elucidation of inhibitor-metalloprotein interaction. LF is a hydrolytic zinc-dependent metalloenzyme that is known to play a prominent role in the pathogenesis of Bacillus anthracis. Strains of B. anthracis that are deficient in LF have reduced pathogenicity, making this protein a candidate as the lead virulence factor of anthrax. Anti-toxin therapies are essential to compliment antibiotic treatments, the latter of which are often administered too late due to the asymptomatic nature of anthrax. Several groups have begun to investigate small molecule inhibitors of LF as a route to therapeutics for treating anthrax breakouts. A resurgence in this area has occurred due to international concerns over biowarfare and bioterrorism. Among the most promising inhibitors for LF are previously devised matrix metalloproteinase (MMP) inhibitors, because both MMPs and LF contain a catalytic zinc(II) ion at the active site, which can be directly bound by these inhibitors, thereby suppressing catalytic activity. This common motif has led to the use of MMP inhibitors as inhibitors of LF with encouraging results. Hydroxamic acid-based MMP inhibitors, which make up the vast majority of currently available compounds, have been unsuccessful in clinical trials due to low oral availability, poor pharmacokinetics, and side effects such as musculoskeletal pain. This failure has been due in large part to the low selectivity and affinity of the hydroxamic acid for zinc and the poor chemical stability of the hydroxamic acid group in vivo. Although MMP inhibitors show great promise as LF inhibitors, there remains a need for new compounds, particularly those that provide alternatives to the hydroxamic acid metal chelator. The utilization of a new model-based mechanistic approach that employs synthetic, biochemical, and computational methods to reveal drug-metalloprotein interactions is the focus of the following proposal. Several compounds are proposed as alternatives to hydroxamic acids and have been shown to display improved potency against anthrax LF. Preliminary results show that a LF inhibitor based on our design strategy is potent, soluble, selective, and capable of protecting macrophage cells from anthrax lethal toxin. Further refinement of this approach is expected to yield even more effective LF inhibitors. The proposed project involves the discovery of new compounds to address the threat of anthrax. Molecules will be designed and synthesized to attack a key toxin produced by the anthrax bacteria. In this way, innovative therapeutics for treating anthrax outbreaks will be developed.