Cancer Therapy: Preclinical Cancer Network Disruption by a Single Molecule Inhibitor Targeting Both Histone Deacetylase Activity and Phosphatidylinositol 3-Kinase Signaling

Purpose: Given that histone deacetylase (HDAC) inhibitors are known to induce multiple epigenetic modifications affecting signaling networks and act synergistically with phosphatidylinositol 3-kinase (PI3K) inhibitors, we developed a strategy to simultaneously inhibit HDACs and PI3K in cancer cells. Experimental Design: We constructed dual-acting inhibitors by incorporating HDAC inhibitory functionality into a PI3K inhibitor pharmacophore. CUDC-907, a development candidate selected from these dual inhibitors, was evaluated in vitro and in vivo to determine its pharmacologic properties, anticancer activity, and mechanism of action. Results: CUDC-907 potently inhibits class I PI3Ks as well as classes I and II HDAC enzymes. Through its integrated HDAC inhibitory activity, CUDC-907 durably inhibits the PI3K-AKT-mTOR pathway and compensatory signaling molecules such as RAF, MEK, MAPK, and STAT-3, as well as upstream receptor tyrosine kinases. CUDC-907 shows greater growth inhibition and proapoptotic activity than single-target PI3K or HDAC inhibitors in both cultured and implanted cancer cells. Conclusions: CUDC-907 may offer improved therapeutic benefits through simultaneous, sustained disruption of multiple oncogenic signaling networks. Clin Cancer Res; 1–10. 2012 AACR. Introduction The phosphatidylinositol 3-kinase (PI3K) pathway plays an important role in cancer cell initiation, growth, proliferation, and survival. The PI3 kinases are frequently activated through mutation or receptor tyrosine kinases in many cancers (1, 2). More than 20 agents targeting the PI3K/AKT pathway are currently being evaluated in clinical trials and several of these agents have shown single-agent activity in cancers with phosphatidyl inositol 3-kinase catalytic subunit (PIK3CA)mutations or PTEN deletion/mutations (3–6). However, the efficacy of PI3K inhibitors is limited by concurrent activation of other survivaland growth-related pathways (5, 7–9). A potential strategy to overcome these limitations is to combine PI3K and MEK inhibitors to achieve synergistic antitumor activity. Preclinical studies have showed that this combination significantly improves efficacy in xenograft tumor models that carry various genetic alterations, such as KRASmutations,HER2 amplification, or PTEN deletion/ mutations (9–12). Of note, several phase I clinical trials testing combinations of PI3K and MEK pathway inhibitors are in progress (13). Another promising strategy to overcome potential limitations of targeting the PI3K pathway is to disrupt multiple pathways through histone deacetylase (HDAC) inhibition (14, 15). By regulating both histone and nonhistone substrates, HDAC inhibitors can affect a variety of cell functions and synergize with PI3K inhibitors (16, 17). In this report, we synthesized a novel series of dual-acting PI3K and HDAC inhibitors by incorporating HDAC inhibitory functionality into a PI3K inhibitor pharmacophore. We show the unique pharmacologic properties of one of the best of the series, CUDC-907, and its potent anticancer activity through oncogenic signaling network disruption. Materials and Methods Reagents CUDC-907, vorinostat [suberoylanilide hydroxamic acid (SAHA)], panobinostat (LBH-589), GDC-0941, and BEZ235 were synthesized in-house. CAL-101 was purchased from Active Biochem (Maplewood, NJ). For in vitro assays, compoundsweredissolved indimethyl sulfoxide (DMSO)as stockandstoredat 80 C.For in vivo studies,CUDC-907was formulated in 30% Captisol (Cydex Pharmaceuticals, Inc.). Authors' Affiliation: Curis, Inc., Lexington, Massachusetts Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/). Corresponding Author: Rudi Bao, Curis, Inc., 4 Maguire Road, Lexington, MA 02421. Phone: 617-503-6500; Fax: 617-503-6501; E-mail: [email protected] doi: 10.1158/1078-0432.CCR-12-0055 2012 American Association for Cancer Research. Clinical Cancer Research www.aacrjournals.org OF1 Research. on April 13, 2017. © 2012 American Association for Cancer clincancerres.aacrjournals.org Downloaded from Published OnlineFirst June 12, 2012; DOI: 10.1158/1078-0432.CCR-12-0055