ETP-46464

ETP-46464 is an effective mTOR and ATR inhibitor with IC₅₀s of 0.6 and 14 nM, respectively. IC50 & Target:IC50: 0.6 nM (mTOR), 14 nM (ATR), 36 nM (DNA-PK), 170 nM (PI3Kα), 545 nM (ATM)^[1] In Vitro:ETP-46464 (ATRi) also inhibits DNA-PK, PI3Kα and ATM with IC₅₀s of 36 nM, 170 nM and 545 nM, respectively^[1]. Platinum-sensitive and -resistant ovarian, endometrial and cervical cancer cell lines are treated with varying levels of Cisplatin (0-50 µM) with or without the ETP-46464 (5.0 µM) and/or the KU55933 (10.0 µM) for 72 h. Single-agent dose response analyses of ETP-46464 and KU55933 in a subset of cell lines reveal a wide LD₅₀ range of 10.0±8.7 and 38.3±7.6 µM respectively. Co-treatment doses are chosen based on these studies and previously published evidence of phospho-Chk1 (Ser345) and phospho-ATM (Ser1981) inhibition following ionizing radiation exposure and dose response treatments with ETP-46464 and KU55933. Treatment with ETP-46464 significantly increases the response of Cisplatin in all cell lines tested, resulting in 52-89% enhancement in activity and are synergistic. The combined inhibition of ATR and ATM enhances the response of Cisplatin to a level equivalent to that observed using ETP-46464 alone. These effects are independent of p53 status, and are observed in all gynecologic (GYN) cancer cells tested. Treatment with ETP-46464, but not KU55933, not only sensitizes these GYN cancer cell lines to Cisplatin, but also enhances the response of Carboplatin^[2].