PGP and cancer: We investigated the potential chemosensitizing effect of branebrutinib on P-gp-mediated resistance to known P-gp drug substrates (Kartner et al., 1983) such as vincristine, paclitaxel and colchicine in P-gp-overexpressing multidrug-resistant human epidermal KB-V-1 cancer cells, human ovarian NCI-ADR-RES cancer cells, and P-gp-transfected MDR19-HEK293 cells.