Recent evidence indicates that both PI3K-Akt-mTOR signaling pathway and HDAC are validated targets in hematological cancers. In order to overcome primary resistance and prevent secondary resistance resulting from compensatory/feedback mechanisms in cancer cells, CUDC-907 was designed to inhibit all isoforms of Class I PI3K and Class I and II HDAC, based on previous observations that synergistic effects can be achieved by inhibition of both HDAC and PI3K in cancer cells. In cell proliferation assays, this compound displays potent anti-proliferation activity in hematological cancer cell lines including non-Hodgkin's lymphoma (NHL), and multiple myeloma (MM). Mechanistically, CUDC-907 is able to simultaneously suppress PI3K-Akt-mTOR as well as other essential signaling pathways due to epigenetic modifications via HDAC inhibition. CUDC-907 is orally bio-available in dogs, has a long half-life in murine tumors, induces apoptosis and inhibits cancer cell proliferation in xenograft tumors. In efficacy studies in NHL and MM models, CUDC-907 is more efficacious than either a single-agent PI3K or HDAC inhibitor reference compound or a combination of the two agents given at maximally tolerated doses (MTD). Furthermore, CUDC-907 is more efficacious than the PI3Kα-selective inhibitor CAL-101 when dosed at MTD doses. These observations are related to our findings that, all isoforms of PI3K are expressed in most hematological cancer models. Therefore, the efficacy of isoform selective PI3K inhibitors may be limited only to those cancers driven by a specific PI3K subtype. In addition, a synergistic antitumor effect can be achieved in efficacy studies when CUDC-907 is combined with standard of care agents in both NHL and MM models. In conclusion, through broad network disruption, CUDC-907 may offer a greater therapeutic benefit than isoform-specific PI3K inhibitors as a novel anti-cancer treatment of hematological malignancies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3744. doi:1538-7445.AM2012-3744