Abstract 1052: In vitro mechanism of action of AZD5363, a novel AKT inhibitor, in breast and prostate cancer cell lines

AKT (protein kinase B) is a key regulator of the phosphoinositide-3-kinase signaling pathway and plays a key role in mediating signals for cell growth, survival and differentiation. This pathway is among the most commonly de-regulated pathways in human cancer and represents a key target for therapeutic intervention. Here, we describe the in-vitro mechanism of action of AZD5363, a potent small molecule inhibitor of AKT1, AKT2 and AKT3. We show that treatment of breast and prostate cancer cell lines with AZD5363 leads to inhibition of phosphorylation of a number of AKT substrates including PRAS40, GSK-3β and the downstream marker, P70S6K. In the BT474c cell line, >90% inhibition of phosphorylation of PRAS40 was observed at 1uM and this effect was sustained for 24 hours. Inhibition of phosphorylation of 4E-BP1, a key regulator of protein translation, was also observed when treating cells with AZD5363. We demonstrate that inhibition of phosphorylation of 4EBP1 (Thr37/46) is associated with an induction of 4E-BP1 binding to the eIF4E-mRNA CAP complex within 1 hour of dosing with AZD5363, consistent with inhibition of CAP-dependent protein translation. Analysis of phenotypic endpoints indicates that AZD5363 is a potent inhibitor of proliferation in the majority of breast and prostate cell lines studied. In addition, in a subset of cell lines, treatment with AZD5363 was shown to induce a cytotoxic phenotype measured by a Sytox Green endpoint. In the BT474c cell line, 1uM AZD5363 inhibited phosphorylation of 4E-BP1 by 50% at 24 hours and induced 11% apoptosis at 72 hours. This data demonstrates that AZD5363 has profound effects on downstream effectors of the PI3K/AKT pathway consistent with that of an Akt inhibitor which results in an anti-proliferative, and in some cases cytotoxic, profile in breast and prostate cell lines. AZD5363 is currently in Phase I clinical trials. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1052. doi:10.1158/1538-7445.AM2011-1052