Polypharmacological repurposing approach identifies approved drugs as potential inhibitors of Mycobacterium tuberculosis.

Mycobacterium tuberculosis (M. tb), the causative pathogen of tuberculosis (TB) remains the leading cause of death from single infectious agent. Further, its evolution to multi-drug resistant (MDR) and extremely drug-resistant (XDR) strains necessitate de-novo identification of drug- targets/candidates or to repurpose existing drugs against known targets through drug repurposing. Repurposing of drugs has gained traction recently where orphan drugs are exploited for new indications. In the current study, we have combined drug repurposing with polypharmacological targeting approach to modulate structure-function of multiple proteins in M. tb. Based on previously established essentiality of genes in M. tb, four proteins implicated in acceleration of protein folding (PpiB), chaperone assisted protein folding (MoxR1), microbial replication (RipA) and host immune modulation (S-adenosyl dependent methyltransferase, sMTase) were selected. Genetic diversity analyses in target proteins showed accumulation of mutations outside respective substrate/drug binding sites. Using a composite receptor-template based screening method followed by molecular dynamics simulations, we have identified potential candidates from FDA approved drugs database; Anidulafungin (anti-fungal), Azilsartan (anti-hypertensive) and Degarelix (anti-cancer). Isothermal titration calorimetric analyses showed that the drugs can bind with high affinity to target proteins and interfere with known protein-protein interaction of MoxR1 and RipA. Cell based inhibitory assays of these drugs against M. tb (H37Ra) culture indicates their potential to interfere with pathogen growth and replication. Topographic assessment of drug-treated bacteria showed induction of morphological aberrations in M. tb. The approved candidates may also serve as scaffolds for optimization to future anti-mycobacterial agents which can target MDR strains of M. tb.