Perspective: Challenges and opportunities in TB drug discovery from phenotypic screening.

Tuberculosis poses a major global health problem and multi-drug resistant strains are increasingly prevalent. Hence there is an urgent need to discover new TB drugs. Cell based phenotypic screening represents a powerful approach to identify anti-mycobacterial compounds and elucidate novel targets. Three high throughput phenotypic screens were performed at NITD against mycobacterium. Hits were identified and chemical series selected for optimisation. This produced compounds with good in vitro anti-mycobacterial activity and pharmacokinetic properties. Some compounds displayed oral activity in mouse efficacy models of TB. Herein, we review the TB discovery efforts at NITD and share experiences in optimisation of phenotypic hits, describing challenges encountered and lessons learned. We also offer perspectives to facilitate future selection and advancement of phenotypic hits.