Identification of Novel Leads as Antitubercular Agents that Target Mtb-DHFR by using Virtual Screening

Drug-resistant tuberculosis (TB) is a global health concern, necessitating novel therapeutics. Dihydrofolate reductase (DHFR) from Mycobacterium tuberculosis (Mtb-DHFR) is a promising target due to differences from human DHFR (h- DHFR), despite 26% structural similarity.

Virtual screening of in-house and SPECS libraries identified Hit-02. Based on docking results, five derivatives (Ansh-01 to Ansh-05) were synthesized and confirmed via spectroscopic techniques. Compounds were evaluated against H37Rv strain using MABA and DHFR inhibition assays. ADMET profiles and sub-acute toxicity were also assessed.

Ansh-04 showed potent activity by inhibiting Mtb-DHFR (IC50 = 99 μM) and h-DHFR (IC50 = 526 μM), yielding a selectivity index of 5.90, higher than Methotrexate. All synthesized compounds were found active against H37Rv strain in ranges (61-180 μM). Docking studies confirmed favorable binding to Mtb-DHFR. ADMET and toxicity data supported its drug-likeness and safety.

The observed potency and selectivity of Ansh-04 highlight its potential as a lead molecule targeting Mtb-DHFR. Its superior selectivity index compared to Methotrexate reduces concerns of off-target effects on human DHFR. The SAR trends observed across the Ansh-series could guide future optimization for increased efficacy and bioavailability.

On the basis of cell-based and enzymatic results, we concluded that Ansh- 04 is a promising, selective Mtb-DHFR inhibitor with potential as an anti-TB lead candidate.