Purpose: To identify an improved lead molecule for the human dihydrofolate reductase (DHFR) inhibition that ‘sits’ in the same binding cavity as methotrexate by high throughput computationalscreening.Methods: The 3-D structure of the DHFR binding site was examined using ‘CASTp3.0’. Structure based in silico screening of about 5 million drug candidates housed in the MCULE database was performed. The obtained molecule-hits were ranked in accordance with their VINA scores, made to pass through drug-likeness filters, ΔG cut-off criterion, toxicity-checker and finally ‘zero RO5 criterion’.Results: The ‘top molecule’, namely, 4-amino-N'-(benzoyloxy)-N-(2,4-dimethylphenyl)-1,2,5-oxadiazole- 3-carboximidamide, displayed robust binding with human DHFR through 21 amino acid residues (ΔG = - 9.6 kcal/mol) while 10 of these residues were the same as those displayed by ‘methotrexate binding interactions’. It passed through relevant drug screening filters including the ‘Toxicity Checker’.Conclusion: This research work describes the molecular interaction of human DHFR with an improved lead molecule named, 4-amino- N’-(benzoyloxy)-N-(2,4-dimethylphenyl)-1,2,5-oxadiazole-3- carboximidamide, with a ΔG of -9.6 kcal/mol, thus satisfying adequate ADME features for further in vitro and in vivo validation in the context of rheumatoid arthritis.
Keywords: Dihydrofolate reductase, In silico screening, Methotrexate, Rheumatoid arthritis, DHFR
In silico screening of drug candidates for thermoresponsive liposome formulations