Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

The zinc ionophore PBT2 is tuberculocidal and synergistic with current Mtb therapies (#104)

Emily Strong 1 , Juanelle Furness 1 , Miljan Stupar 1 , Ibrahim M El-Deeb 2 , David MP De Oliveira 1 , Mark von Itzstein 2 , Mark J Walker 1 , Nicholas P West 1
  1. School of Chemistry and Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
  2. Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia

Tuberculosis (TB) is a significant global infectious disease with enormous implications to human health and productivity. Current treatment regimens are lengthy and burdensome on patients, leading to poor compliance. This, together with widespread occurrence of Mycobacterium tuberculosis (Mtb) drug-resistance necessitates the discovery of novel and innovative drugs that improve treatment outcomes and shorten treatment times. Recent advances in drug development against Mtb has been slow with bedaquiline, an atypical ionophore, being approved for drug resistant case use in 2012; the first new drug in 40 years. PBT2, an 8-hydroxyquinoline zinc and copper ionophore has recently been shown to rescue antibiotic resistance in several Gram-positive bacterial species. In this study we investigated PBT2’s potential as an anti-mycobacterial. Using minimum inhibitory concentration microplate assays we found that PBT2 was highly anti-mycobacterial in the presence of zinc but not copper. To examine the potential for PBT2 to re-sensitise drug resistant Mtb we generated a series of mono- drug resistant Mtb mutants. While these mutants were not found to be re-sensitised to current TB treatments, their sensitivity to PBT2 was maintained. We have demonstrated PBT2’s efficacy in-vivo, revealing a significant reduction of the Mtb load in the lungs of mice following treatment. Using an intra-macrophage survival assay, we have also demonstrated that PBT2 is able to kill Mtb in macrophages, independently of zinc accumulation. Excitingly, in both in-vitro culture and in macrophages PBT2 demonstrates synergy with rifampicin, a front-line anti-TB drug. These data present PBT2 as a potential new TB therapy which could work with current therapeutics against both drug-sensitive and drug-resistant Mtb, leading to shortened treatment times and improved patient outcomes.