GDC-0449

GDC-0449 targets the Hedgehog signaling pathway, blocking the activities of the Hedgehog-ligand cell surface receptors PTCH and/or SMO and suppressing Hedgehog signaling. GDC-0449 prevents multiple ATP-binding cassette (ABC) transporters. GDC-0449 also blocks ABCG2, Pgp, and MRP1-important ABC transporters associated with MDR. GDC-0449 is a potent inhibitor of ABC transporters, ABCG2/BCRP and ABCB1/Pgp, and is a mild inhibitor of ABCC1/MRP1. In ABCG2-overexpressing HEK293 cells, GDC-0449 increases retention of the fluorescent ABCG2 substrate BODIPY-prazosin and resensitizes these cells to mitoxantrone. In Madin-Darby canine kidney II cells engineered to overexpress Pgp or MRP1, GDC-0449 increases the retention of calcein-AM and resensitizes them to colchicine. GDC-0449 also resensitizes human non-small cell lung carcinoma cells NCI-H460/par and NCI-H460/MX20, which overexpress ABCG2 in response to mitoxantrone, to mitoxantrone, and to topotecan or SN-38. The IC50 values of GDC-0449 for prevention of ABCG2 and Pgp are about 1.4 μM and 3.0 μM, respectively. ^[2] GDC-0449 alters intracellular Ca²⁺ homeostasis and inhibits cell growth in cisplatin-resistant lung cancer cells. ^[3]