P-gp Inhibitor 22 effectively inhibits P-glycoprotein (P-gp) and its efflux function, promoting apoptosis and the accumulation of MCF-7/ADR cells in the S phase [1].

P-gp inhibitor 22 (compound 4b; 6.25-100 μM; 24 hours) exhibits significant activity against MCF-7/ADR cells as demonstrated by its ability to induce apoptosis and cause cell cycle arrest at the S phase at a concentration of 5 μM over a 24-hour period [1]. This compound effectively inhibits several cell lines, including PC-3, SKOV-3, HeLa, MCF-7/ADR, HFL-1, and WI-38, with IC 50 values of 3.3 μM, 0.7 μM, 2.4 μM, 5.0 μM, 72.0 μM, and 61.1 μM, respectively [1]. Additionally, cytotoxicity assays performed on MCF-7/ADR cells show dose-dependent toxicity, with cell cycle analysis confirming cell cycle blockade and induction of apoptosis at 5 μM concentration within the S phase [1].