Anthrax Lethal Factor Protease Inhibitors:  Synthesis, SAR, and Structure-Based 3D QSAR Studies

Abstract

We have recently identified a series of compounds which efficiently inhibit Anthrax lethal factor (LF) metallo-protease. Here we present further structure activity relationship and CoMFA (Comparative Molecular Field Analysis) studies on newly derived inhibitors. The obtained 3D QSAR model was subsequently compared with the X-ray structure of the complex between LF and a representative compound. Our studies form the basis for the rational design of additional compounds with improved activity and selectivity.Anthrax is an infectious disease caused by the bacterium Bacillus anthracis. 1 This rod shaped bacterium infects humans through the respiratory system, skin, or digestive tract. Dependent upon the entry route into the human body, Anthrax can be highly lethal. Although cutaneous Anthrax is rarely lethal, inhalation Anthrax is dangerous and usually fatal. 2 Upon inhalation, the Anthrax spores adhere to the alveolar macrophages and germinate. Bacteria migrate to the lymph node, in which they rapidly multiply and excrete a tripartite exotoxin comprised of protective antigen (PA, 83 kDa), lethal factor (LF, Zn 2+ -metalloproteinase, 90 kDa) and calmodulin-activated edema factor adenylate cyclase (EF, 89 kDa). 3,4 The combined actions of these proteins constitute the Anthrax toxins (AT) which induce cell death. Unless properly and promptly treated, inhalation anthrax will lead to the death of the host organism. 5 Initially, PA binds to an AT receptor on the host cell surface, where it is cleaved by a furinlike protease to produce a 20 kDa N-terminal fragment (PA 20 ) and a 63 kDa C-terminal fragment (PA 63 ). 6 PA 63 , which remains bound to the membrane, oligomerizes into a heptameric prepore capable of binding LF and EF. 7 Upon binding of LF and EF, the complex undergoes receptor mediated endocytosis and the PA 63 conformational change allows the two enzymatic moieties LF and EF to translocate into the cell cytosol. Once in the cytosol, LF is then able to cleave several members of the MAPKK family near the Nterminus. [8][9][10] This cleavage prevents interaction with, and phosphorylation of, downstream MAPK, thereby inhibiting one or more signaling pathways through a mechanism not yet understood. 11 * To Whom Correspondence should be addressed. With the long term goal of developing novel potential treatments for Anthrax disease, we previously identified several small molecule inhibitors that inhibit Anthrax LF protease activity with IC 50 's in sub-micromolar range. 12 Cell based and peptide cleavage assays were subsequently used to confirm the potency of the iterate leads. The most potent compounds were subsequently tested in mice models of the diseases showing a protection against Bacillus anthracis spores, when used in combination with the antibiotic ciproflaxin. 12 Initial structure activity relationship (SAR) data suggested that the presence of multiple substitutions on the phenyl ring significantly increases the inhibitory activity. 12 Furthermore, details of the 3D structure of the complex between ...

Notice of Retraction: Homology Modeling and Expression Analysis of Sterol 14alpha-Demethylase from Ustilago maydis

“…As part of our research project, the 3D model of UmCYP51 was built based on the structure template of 1e9x.pdb (http://oca.ebi.ac.uk/ oca-bin/ocashort) using the FUGUE module of SYBYL7.0 program( Figure 1A) [14]. The identity was 28% between sequences of UmCYP51 and MtCYP51 after sequence alignment using Clustal W (http://www2.ebi.ac.uk/ CLUSTALW) with a gap penalty of 10 and BLOSUM series weight matrix.…”

Recent advances in MMP inhibitor design

“…The Bristol-Myers dioxothiadiazine is a second example of the structural transformation of an MMP to TACE-selective inhibitor [99,100]. Clearly, while building upon the substantial medicinal chemistry knowledge that has accrued for MMP design (as is also evident in the synthesis of anthrax lethal factor inhibitors [101][102][103][104]), the therapeutic objectives for these inhibitors is not cancer.…”

Discovery and Development of Anthrax Lethal Factor Metalloproteinase Inhibitors

“…Interestingly, the sulfur atom of the thiazolidine ring coordinates the active site zinc ion. A QSAR model based on the crystal structure and a number of analogs tested suggested substitution of larger and less electronegative groups to the phenyl ring would be expected to improve potency [103]. Low concentrations of 16 and its analogs could block LeTx-mediated cytolysis of cultured macrophages.…”