Bacillus anthracis ("anthrax") is a proven agent of biological terrorism. Pulmonary anthrax, in which spores of the anthrax bacteria are inhaled, is typically fatal unless diagnosis is made at an early stage of infection, when antibiotics such as Ciprofloxacin can provide a complete cure. At late stages in the disease, antibiotics can kill the anthrax bacteria, but do not affect LF secreted by the bacteria, which is sufficiently concentrated in the bloodstream. LF enters cells and inactivates a human protein called "mitogen-activated protein kinase", or "MAPKK", disrupting the normal signaling pathways of the cell and inducing cell-death.
Using a fragment-based approach based on assays conducted with highly sensitive nuclear magnetic resonance ("NMR") techniques developed in Dr. Pellecchia's laboratory, the scientists were able to identify a scaffold that served as a template for designing a preferred structure for small-molecule inhibitors of LF. Lead compounds were synthesized and validated as highly potent and selective against LF in vitro. In in vitro assays, the compounds did not affect prototype human metalloproteinase enzymes that are structurally similar to LF. This is very important as selectivity is a fundamental prerequisite for a drug to be safe for use in humans.
Three lead compounds where tested in mice infected with anthrax spores, in combination with the antibiotic Ciprofloxacin. The survival rate for mice treated with each of the compounds tested in the combination therapy was two-fold over mice treated with Ciprofloxacin a