Theme 1: Bacterial Target Discovery
The research of Theme 1 is focused on delivering drugable in vitro and in vivo validated targets with bactericidal potential against dormant mycobacteria. It uses genetic and chemical approaches in TB persistence models to determine the molecular mechanism of dormancy in mycobacteria and to identify new bacterial targets that are essential for the survival of growing and dormant mycobacteria.
The theme also evaluates existing candidate targets and develops target-based whole cell, as well as biochemical assays that enable lead finding and optimization carried out under Theme 2.
Theme 1 also furthers understanding of the biology of mycobacteria and the host response to infection.
Theme 1 Lead: A/Prof. Thomas Dick
Department of Microbiology, National University of Singapore (NUS), Singapore
Whole Cell Screen
Project lead: Dr. Yoshiyuki Yamada
The major barrier to developing new drugs for TB is the lack of attractive targets with their associated, whole cell-active lead compounds for target-based lead optimization campaigns. The goal of this projects is to identify such target-lead couples for the development of new clinical TB drug candidates.
Project lead: Carolyn Mulu Wu
Mycobacteria are able to survive starvation by shifting to a non-replicating state of low metabolism. Different starvation conditions may result in different cellular differentiation responses.
Depending on the specific starvation conditions, mycobacteria undergo either incomplete or complete reductive cell division to produce ‘normal-sized’ septated multi- or small mono-nucloided resting cells, respectively, and thus support the morphological plasticity in mycobacteria. The project aims to determine the key regulators in this adaptation process to nutrient-starvation induced dormancy.
Project lead: Devika Mukherjee
The Beuerman lab (Singapore Eye Research Institute) identified a new class of compounds based on alpha-mangosteen with excellent potency against Staphylococcus aureus. The mechanism of action involves cell envelope disruption. Theme 1 tested the lead compound AM0016 in M.bovis BCG and M.smegmatis and will test in Mtb H37Rv and drug resistant clinical isolates. The mechanism of action of this novel compound against mycobacteria is unknown and characterization studies are in progress. In contrast to most TB drugs, AM0016 shows rapid cidal activity and is active against phenotypically drug resistant dormant bacteria.
Pyrazinoic Acid and Pyrazinamide
Project lead: Pooja Gopal
Pyrazinamide (PZA) is a critical component of the first line TB combination therapy in shortening the duration of treatment from 9-12 months to 6 months. Although discovered due to its activity against TB in mice, PZA is known to possess no activity against growing bacilli in vitro under physiological pH (6.5). The current paradigm is that it is active in vitro only at an acidic pH (5.5) and that it needs to be converted into pyrazinoic acid (POA), which is the active compound. This project re-evaluates the dependence of pH on the potency of both PZA and POA in susceptible mycobacteria.
Project lead: Pooja Gopal
Perchlozone is a new (2012) thiosemicarbazone developed by JSC Pharmasyntez with demonstrated efficacy in clinical trials with MDR-TB patients. A well-studied thiosemicarbazone is the old tuberculosis drug thiacetazone, which is involved in cell wall biosynthesis in Mtb. The project has demonstrated that the two compounds have an identical spectrum of activity, and mutants showed cross-resistance, which was mapped to HadABC and EthA. These results suggest that Perchlozone, like Thiacetazone, is a prodrug and that both drugs share EthA as activating enzyme and HadABC as their principal target.
Fragments Screen 2
Project lead: Dereje Abate Negatu
The aim of the project is to identify novel fragments with activity against actively growing and dormant mycobacteria. Fragment-based whole cell screening approach is applied, and for identified hits that have acceptable potency and toxicity profile, target identification will be elucidated by generating spontaneous resistance mutants of the compound followed by whole genome sequencing.
Theme 1 Collaborators
Experimental Therapeutics Centre, A*STAR, Singapore)
Department of Pharmacy, National University of Singapore, Singapore
Singapore Eye Research Institute, Singapore
Genome Institute of Singapore, A*STAR, Singapore
School of Biological Sciences, Nanyang Technological University, Singapore
National University Hospital, Singapore
Harvard University, MA, USA
Public Health Research Institute, NJ, USA
Research projects in Theme 1 are conducted in collaboration with Singapore’s largest research BSL-3 Core Facility at National University of Singapore. It houses a TB Research Laboratory, which is licensed for usage of various mycobacterial strains and animal models.