Drugs repurposing: An approach to identify new hits against anticancer drug target TFIIH subunit p8

Drug repositioning is one of the most effective approaches towards drug discovery and development. It involves the identification of new therapeutic indications of existing drugs. The present study evaluated several drugs for their ability to modulate activity of the p8 subunit of TFIIH complex. Negative modulation of p8 subunit activity disrupts protein-protein interactions (PPIs) among the subunits of TFIIH complex, and thereby the TFIIH-associated functions. TFIIH complex has key role in the transcription and nucleotide excision repair activity in cancerous cells. TFIIH complex has emerged as a privileged drug target in anticancer research. Out of 60 drugs, amlopipine (13), diltiazem (16), gemfibrozil (19), levocitrizine dihydrochloride (20), losartan potassium (22), clorthalidone (24), and escitalopram (28) showed interactions with subunit p8 in the ligand-protein binding and chemical shift perturbation studies. The K_d values were found to be between 0.25 and 1 mM. These drugs also caused thermal destabilization of the subunit p8 by negatively shifting the melting temperature by ≥ 2 °C. Molecular docking studies indicated the interaction of these drugs with important residues of p8-p52 complex, such as Glu48, Lys51, Glu496, and Glu455 via non-covalent interactions. This study has thereby identified 7 drugs that can be investigated further as potential anticancer drugs.