Fragment-Based Drug Design, 2D-QSAR and DFT Calculation: Scaffolds of 1, 2, 4, triazolo [1, 5-a] pyrimidin-7-amines as Potential Inhibitors of Plasmodium falciparum Dihydroorotate Dehydrogenase

Background: Plasmodium falciparum dihydroorotate dehydrogenase (PfDODH) is one of the enzymes currently explored in the treatment of malaria. Although there is currently no clinically approved drug targeting PfDODH, many of the compounds in clinical trials have [1, 2, 4,] triazolo [1, 5-a] pyrimidin- 7-amine backbone structure. Objective: This study sought to design new compounds from the fragments of known experimental inhibitors of PfDODH. Methods: Nine experimental compounds retrieved from Drug Bank online were downloaded and broken into fragments using the Schrodinger power shell; the fragments were recombined to generate new ligand structures using the BREED algorithm. The new compounds were docked with PfDODH crystal structure, after which the compounds were filtered with extensive drug-likeness and toxicity parameters. A 2D-QSAR model was built using the multiple linear regression method and externally validated. The electronic properties of the compounds were calculated using the density functional theory method. Results: Structural investigation of the six designed compounds, which had superior binding energies than the standard inhibitors, showed that five of them had [1, 2, 4,] triazolo [1, 5-a] pyrimidin-7-amine moieties and interacted with essential residues at the PfDODH binding site. In addition to their drug-like and pharmacokinetic properties, they also showed minimal toxicities. The externally validated 2D-QSAR model with R² and Q² values of 0.6852 and 0.6691 confirmed the inhibitory prowess of these compounds against PfDODH. The DFT calculations showed regions of the molecules prone to electrophilic and nucleophilic attacks. Conclusion: The current study thus provides insight into the development of a new set of potent PfDODH inhibitors.