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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; 18(15); 4104-13. Ó2012 AACR.

By incorporating histone deacetylase (HDAC) inhibitory functionality into the pharmacophore of the epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) inhibitors, we synthesized a novel series of compounds with potent, multiacting HDAC, EGFR, and HER2 inhibition and identified 7-(4-(3-ethynylphenylamino)-7-methoxyquinazolin-6-yloxy)-N-hydroxyheptanamide 8 (CUDC-101) as a drug candidate, which is now in clinical development. 8 displays potent in vitro inhibitory activity against HDAC, EGFR, and HER2 with an IC(50) of 4.4, 2.4, and 15.7 nM, respectively. In most tumor cell lines tested, 8 exhibits efficient antiproliferative activity with greater potency than vorinostat (SAHA), erlotinib, lapatinib, and combinations of vorinostat/erlotinib and vorinostat/lapatinib. In vivo, 8 promotes tumor regression or inhibition in various cancer xenograft models including nonsmall cell lung cancer (NSCLC), liver, breast, head and neck, colon, and pancreatic cancers. These results suggest that a single compound that simultaneously inhibits HDAC, EGFR, and HER2 may offer greater therapeutic benefits in cancer over single-acting agents through the interference with multiple pathways and potential synergy among HDAC and EGFR/HER2 inhibitors.

Receptor tyrosine kinase inhibitors have recently become important therapeutics for a variety of cancers. However, due to the heterogeneous and dynamic nature of tumors, the effectiveness of these agents is often hindered by poor response rates and acquired drug resistance. To overcome these limitations, we created a novel small molecule, CUDC-101, which simultaneously inhibits histone deacetylase and the receptor kinases epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) in cancer cells. Because of its integrated histone deacetylase inhibition, CUDC-101 synergistically blocked key regulators of EGFR/HER2 signaling pathways, also attenuating multiple compensatory pathways, such as AKT, HER3, and MET, which enable cancer cells to escape the effects of conventional EGFR/HER2 inhibitors. CUDC-101 displayed potent antiproliferative and proapoptotic activities against cultured and implanted tumor cells that are sensitive or resistant to several approved single-targeted drugs. Our results show that CUDC-101 has the potential to dramatically improve the treatment of heterogeneous and drug-resistant tumors that cannot be controlled with single-target agents. Further, they provide a framework to create individual small molecules that simultaneously antagonize multiple biochemically distinct oncogenic targets, suggesting a general paradigm to surpass conventional, single-target cancer therapeutics. Cancer Res; 70(9); 3647-56. ©2010 AACR.

Purpose: We designed and synthesized CUDC-305, an HSP90 inhibitor of the novel imidazopyridine class. Here, we report its unique pharmacologic properties and antitumor activities in a variety of tumor types. Experimental Design: The potency of the compound was analyzed by fluorescence polarization competition binding assay. Its antiproliferative activities were assessed in 40 human cancer cell lines. Its pharmacologic properties and antitumor activities were evaluated in a variety of tumor xenograft models.Results: CUDC-305 shows high affinity for HSP90α/β (IC 50 , ∼100 nmol/L) and HSP90 complex derived from cancer cells (IC 50 , 48.8 nmol/L). It displays potent antiproliferative activity against a broad range of cancer cell lines (mean IC 50 , 220 nmol/L). CUDC-305 exhibits high oral bioavailability (96.0%) and selective retention in tumor (half-life, 20.4 hours) compared with normal tissues. Furthermore, CUDC-305 can cross bloodbrain barrier and reach therapeutic levels in brain tissue. CUDC-305 exhibits dosedependent antitumor activity in an s.c. xenograft model of U87MG glioblastoma and significantly prolongs animal survival in U87MG orthotopic model. CUDC-305 also displays potent antitumor activity in animal models of erlotinib-resistant non-small cell lung cancer and induces tumor regression in animal models of MDA-MB-468 breast cancer and MV4-11 acute myelogenous leukemia. Correlating with its efficacy in these various tumor models, CUDC-305 robustly inhibits multiple signaling pathways, including PI3K/AKT and RAF/MEK/ERK, and induces apoptosis. In combination studies, CUDC-305 enhances the antitumor activity of standard-of-care agents in breast and colorectal tumor models. Conclusion: CUDC-305 is a promising drug candidate for the treatment of a variety of cancers, including brain malignancies.

The hedgehog (Hh) family of intercellular signaling proteins is intricately linked to the development and patterning of almost every major vertebrate organ system. In the skin, sonic hedgehog (Shh) is required for hair follicle morphogenesis during embryogenesis and for regulating follicular growth and cycling in the adult. We recently described the identification and characterization of synthetic, non-peptidyl small molecule agonists of the Hh pathway. In this study, we examined the ability of a topically applied Hh-agonist to modulate follicular cycling in adult mouse skin. We report that the Hh-agonist can stimulate the transition from the resting (telogen) to the growth (anagen) stage of the hair cycle in adult mouse skin. Hh-agonist-induced hair growth caused no detectable differences in epidermal proliferation, differentiation, or in the endogenous Hh-signaling pathway as measured by Gli1, Shh, Ptc1, and Gli2 gene expression when compared with a normal hair cycle. In addition, we demonstrate that Hh-agonist is active in human scalp in vitro as measured by Gli1 gene expression. These results suggest that the topical application of Hh-agonist could be effective in treating conditions of decreased proliferation and aberrant follicular cycling in the scalp including androgenetic alopecia (pattern hair loss).

The capacity of targeted anticancer agents to exert immunomodulatory effects provides a strong rationale to develop novel agents suitable for combinatorial regimens with immunotherapy to improve clinical outcomes. In this study, we developed a dual-targeting PI3K and HDAC inhibitor BEBT-908 that potently inhibits tumor cell growth and potentiates anti-PD1 therapy in mice by inducing immunogenic ferroptosis in cancer cells. Treatment with BEBT-908 promoted ferroptotic cell death of cancer cells by hyperacetylating p53 and facilitating the expression of ferroptotic signaling. Furthermore, BEBT-908 promoted a proinflammatory tumor microenvironment that activated host antitumor immune responses and potentiated immune checkpoint blockade therapy. Mechanistically, BEBT-908–induced ferroptosis led to upregulation of MHC class I and activation of endogenous IFNγ signaling in cancer cells via the STAT1 signaling pathway. The dual PI3K/HDAC inhibitor BEBT-908 is a promising targeted therapeutic agent against multiple cancer types that promotes immunogenic ferroptosis and enhances the efficacy of immunotherapy. Significance: The dual PI3K/HDAC inhibitor BEBT-908 elicits potent antitumor responses, effectively inducing immunogenic ferroptosis of tumor cells and potentiating cancer immunotherapy.

CUDC-305 is a heat shock protein 90 (HSP90) inhibitor of the novel imidazopyridine class. Here, we report its activities in non-small cell lung cancer (NSCLC) cell lines with gene deregulations conferring primary or secondary resistance to epidermal growth factor receptor (EGFR) inhibitors. We show that CUDC-305 binds strongly to HSP90 extracted from erlotinib-resistant NSCLC cells (IC 50 70 nmol/L). This result correlates well with the potent antiproliferative activity in erlotinib-resistant NSCLC cell lines (IC 50 120-700 nmol/L) reported previously. Furthermore, it exhibits durable inhibition of multiple oncoproteins and induction of apoptosis in erlotinib-resistant NSCLC cells. CUDC-305 potently inhibits tumor growth in subcutaneous xenograft models of H1975 and A549, which harbor EGFR T790M mutation or K-ras mutations conferring acquired and primary erlotinib resistance, respectively. In addition, CUDC-305 significantly prolongs animal survival in orthotopic lung tumor models of H1975 and A549, which may be partially attributed to its preferential exposure in lung tissue. Furthermore, CUDC-305 is able to extend animal survival in a brain metastatic model of H1975, further confirming its ability to cross the blood-brain barrier. Correlating with its effects in various tumor models, CUDC-305 induces degradation of receptor tyrosine kinases and downstream signaling molecules of the PI3K/AKT and RAF/MEK/ERK pathways simultaneously, with concurrent induction of apoptosis in vivo. In a combination study, CUDC-305 enhanced the antitumor activity of a standard-of-care agent in the H1975 tumor model. These results suggest that CUDC-305 holds promise for the treatment of NSCLC with primary or acquired resistance to EGFR inhibitor therapy.