Innovate to Eradicate
Authors:   , Habjan Eva 
Published: October 2024

Tuberculosis (TB) remains one of the oldest and most persistent infectious diseases, posing a significant global health challenge with over 10 million new infections annually. Despite the availability of treatments, the rise of drug-resistant strains underscores the urgent need for innovative therapeutics and refined drug discovery strategies. This thesis addresses these challenges by presenting new methodologies to enhance early-stage TB drug development. Chapter 1 provides a comprehensive overview of TB, its causative agents, and current drug discovery efforts. A significant challenge in this field is the difficulty of identifying in vitro active compounds that demonstrate efficacy in vivo. To bridge this translational gap, Chapter 2 reviews an in vivo zebrafish embryo infection model designed for the rapid evaluation of compound activity, discussing its advantages and limitations in antimicrobial drug screening. Chapter 3 illustrates the practical application of the zebrafish model in TB drug discovery through medium-throughput screening of 240 in vitro active compounds, of which only 14 exhibited activity in the zebrafish model, highlighting the importance of early in vivo assessment. Further characterization of one promising compound revealed its action on aspartyl tRNA synthetase (AspS) in mycobacteria, suggesting its potential as a novel protein synthesis inhibitor. In TB research, model organisms are often used for initial experiments due to biosafety concerns. Chapter 4 investigates the differential activity of two clinically used TB pro-drugs, ethionamide and isoniazid, in M. tuberculosis and its model organism, M. marinum. By engineering an M. marinum strain to enhance drug-activating enzyme expression, we adapted the susceptibility of M. marinum to be similar to that of M. tuberculosis. This engineered strain was further used for drug screening to identify several pro-drugs that would have been overlooked in traditional screenings with M. marinum. Chapter 5 focuses on identifying novel gyrase inhibitors that are selective for mycobacteria. Through a medicinal chemistry approach and the derivatization of known gyrase B inhibitors, we identified structural features that increase specificity for mycobacteria. Finally, Chapter 6 addresses the challenge of mycobacterial membrane permeability, which often presents a bottleneck for compounds to reach intracellular targets. We identified a compound that increases membrane permeability by targeting a novel drug target, Rv0164 (MMAR_0407). This chapter also emphasizes the significance of combination therapy, demonstrating that our new compounds can synergistically enhance the efficacy of existing antibiotics, thereby improving TB treatment strategies. In conclusion, this thesis presents optimized drug discovery strategies for the early phases of drug development, leading to the identification and validation of several new active compounds with potential for future therapeutic applications. The results are contextualized within existing literature in Chapter 7, illustrating the importance of ongoing research efforts for the global eradication of tuberculosis, as outlined by the WHO.