title: Unravelling the Secrets of Mycobacterial Cidality through the Lens of Antisense.
abstract: One of the major impediments in anti-tubercular drug discovery is the lack of a robust grammar that governs the in-vitro to the in-vivo translation of efficacy. Mycobacterium tuberculosis (Mtb) is capable of growing both extracellular as well as intracellular; encountering various hostile conditions like acidic milieu, free radicals, starvation, oxygen deprivation, and immune effector mechanisms. Unique survival strategies of Mtb have prompted researchers to develop in-vitro equivalents to simulate in-vivo physiologies and exploited to find efficacious inhibitors against various phenotypes. Conventionally, the inhibitors are screened on Mtb under the conditions that are unrelated to the in-vivo disease environments. The present study was aimed to (1). Investigate cidality of Mtb targets using a non-chemical inhibitor antisense-RNA (AS-RNA) under in-vivo simulated in-vitro conditions.(2). Confirm the cidality of the targets under in-vivo in experimental tuberculosis. (3). Correlate in-vitro vs. in-vivo cidality data to identify the in-vitro condition that best predicts in-vivo cidality potential of the targets. Using cidality as a metric for efficacy, and AS-RNA as a target-specific inhibitor, we delineated the cidality potential of five target genes under six different physiological conditions (replicating, hypoxia, low pH, nutrient starvation, nitrogen depletion, and nitric oxide).In-vitro cidality confirmed in experimental tuberculosis in BALB/c mice using the AS-RNA allowed us to identify cidal targets in the rank order of rpoB>aroK>ppk>rpoC>ilvB. RpoB was used as the cidality control. In-vitro and in-vivo studies feature aroK (encoding shikimate kinase) as an in-vivo mycobactericidal target suitable for anti-TB drug discovery. In-vitro to in-vivo cidality correlations suggested the low pH (R = 0.9856) in-vitro model as best predictor of in-vivo cidality; however, similar correlation studies in pathologically relevant (Kramnik) mice are warranted. In the acute infection phase for the high fidelity translation, the compound efficacy may also be evaluated in the low pH, in addition to the standard replication condition.
authors.affiliation: Research Area, Drug Discovery, AstraZeneca India Private Limited, Bangalore, India.
authors.forename: Parvinder
authors.identifier: 0000-0001-9154-3278
authors.initials: P
authors.lastname: Kaur
authors.affiliation: Drug Discovery, Bugworks, C-CAMP, Bangalore, India.
authors.forename: Santanu
authors.initials: S
authors.lastname: Datta
authors.affiliation: Research Area, Drug Discovery, AstraZeneca India Private Limited, Bangalore, India.
authors.forename: Radha Krishan
authors.initials: RK
authors.lastname: Shandil
authors.affiliation: Research Area, Drug Discovery, AstraZeneca India Private Limited, Bangalore, India.
authors.forename: Naveen
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Research Area, Drug Discovery, AstraZeneca India Private Limited, Bangalore, India.
authors.forename: Nanduri
authors.initials: N
authors.lastname: Robert
authors.affiliation: Arthritis and Tissue Degeneration Program, Hospital for Special Surgery, New York, New York, United States of America.
authors.forename: Upneet K
authors.initials: UK
authors.lastname: Sokhi
authors.affiliation: Research Area, Drug Discovery, AstraZeneca India Private Limited, Bangalore, India.
authors.forename: Supreeth
authors.initials: S
authors.lastname: Guptha
authors.affiliation: Research Area, Drug Discovery, AstraZeneca India Private Limited, Bangalore, India.
authors.forename: Shridhar
authors.initials: S
authors.lastname: Narayanan
authors.affiliation: School of Biosciences and Technology, VIT University, Vellore, India.
authors.forename: Anand
authors.initials: A
authors.lastname: Anbarasu
authors.affiliation: School of Biosciences and Technology, VIT University, Vellore, India.
authors.forename: Sudha
authors.initials: S
authors.lastname: Ramaiah
mesh_terms: D000818:Animals; D000995:Antitubercular Agents / Q000494:pharmacology; D058491:Bacterial Load / Q000187:drug effects; D055808:Drug Discovery; D020868:Gene Silencing; D016680:Genome, Bacterial; D054884:Host-Pathogen Interactions; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D016372:RNA, Antisense / Q000235:genetics / Q000494:pharmacology; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D016372:RNA, Antisense