Identification of Morpholino Thiophenes as Novel Mycobacterium tuberculosis Inhibitors, Targeting QcrB

With the emergence of multidrug-resistant strains of <i>Mycobacterium tuberculosis</i> there is a pressing need for new oral drugs with novel mechanisms of action. Herein, we describe the identification of a novel morpholino–thiophenes (MOT) series following phenotypic screening of the Eli Lilly corporate library against <i>M. tuberculosis</i> strain H37Rv. The design, synthesis, and structure–activity relationships of a range of analogues around the confirmed actives are described. Optimized leads with potent whole cell activity against H37Rv, no cytotoxicity flags, and in vivo efficacy in an acute murine model of infection are described. Mode-of-action studies suggest that the novel scaffold targets QcrB, a subunit of the menaquinol cytochrome <i>c</i> oxidoreductase, part of the bc1-aa3-type cytochrome <i>c</i> oxidase complex that is responsible for driving oxygen-dependent respiration

Engineering yeast cytosine deaminase for improved efficacy in cancer gene directed enzyme prodrug therapy

Thesis (Ph. D.)--University of Washington, 2007.Conventional treatment of cancer typically involves some combination of surgery coupled with radio- or chemotherapy. Prognosis in cases of tumor metastasis or inoperable solid-tumors remains grim as cancer cells are often refractory to the DNA damage caused by these treatments due to the loss of cell cycle regulatory proteins during oncogenesis. Higher dosages of either radiation or chemotherapeutic agents can compensate, however, lack of cancer cell specificity and low therapeutic index put strict limitations on dosages that can be administered safely.Growing understanding of oncogenesis and molecular biology has lead to the development of vectors capable of targeting and transducing tumors with high specificity. One of the most successful applications of this technology has been a form of targeted chemotherapy called gene-directed enzyme/prodrug therapy (GDEPT), in which tumor cells are transduced with a suicide gene encoding a non-endogenous enzyme that later metabolically converts a systemically administered prodrug into a potent cytotoxin locally within the tumor. These enzymes are often non-ideal due to both lack of stability and low catalytic efficiency. Protein engineering methods could be used in order to tailor the pharmacokinetic profiles of these enzymes for improved therapeutic use.Our work focused on the re-engineering the enzyme yeast cytosine deaminase for improved efficacy in GDEPT. Two distinct enzyme engineering strategies were employed: regiospecific random mutagenesis was used in order to select for mutants with increased sensitization to the prodrug 5-fluorocytosine while computational design was used to select thermostabilizing mutations. Both approaches lead to independent mutations that conferred improved pharmacokinetics in in vivo mouse tumor xenograph models. Additional study revealed that in both cases the biochemical cause of improvement appeared to be thermostabilization of the enzyme and not an improvement in catalytic efficiency

Identification of cyclic hexapeptides natural products with inhibitory potency against Mycobacterium tuberculosis

Abstract Objective Our aim was to identify natural products with anti-tubercular activity. Results A set of ~ 500 purified natural product compounds was screened for inhibition against the human pathogen Mycobacterium tuberculosis. A series of cyclic hexapeptides with anti-tubercular activity was identified. Five analogs from a set of sixteen closely related compounds were active, with minimum inhibitory concentrations ranging from 2.3 to 8.9 μM. Eleven structural analogs had no significant activity (MIC > 20 μM) demonstrating structure activity relationship. Sequencing of resistant mutant isolates failed to identify changes accounting for the resistance phenotype