Guang-Xin Xu

CUDC-101, a Multitargeted Inhibitor of Histone Deacetylase, Epidermal Growth Factor Receptor, and Human Epidermal Growth Factor Receptor 2, Exerts Potent Anticancer Activity

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. (c)2010 AACR.

CUDC-305, a novel synthetic HSP90 inhibitor with unique pharmacologic properties for cancer therapy.

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 (IC50, ∼100 nmol/L) and HSP90 complex derived from cancer cells (IC50, 48.8 nmol/L). It displays potent antiproliferative activity against a broad range of cancer cell lines (mean IC50, 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 blood-brain barrier and reach therapeutic levels in brain tissue. CUDC-305 exhibits dose-dependent 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.

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; 18(15); 4104–13. ©2012 AACR.

Targeting heat shock protein 90 with CUDC-305 overcomes erlotinib resistance in non–small cell lung cancer

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 (IC50 70 nmol/L). This result correlates well with the potent antiproliferative activity in erlotinib-resistant NSCLC cell lines (IC50 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. [Mol Cancer Ther 2009;8(12):3296–306]

Dual HDAC and PI3K Inhibitor CUDC-907 Downregulates MYC and Suppresses Growth of MYC-dependent Cancers.

Upregulation of MYC is a common driver event in human cancers, and some tumors depend on MYC to maintain transcriptional programs that promote cell growth and proliferation. Preclinical studies have suggested that individually targeting upstream regulators of MYC, such as histone deacetylases (HDAC) and phosphoinositide 3-kinases (PI3K), can reduce MYC protein levels and suppress the growth of MYC-driven cancers. Synergy between HDAC and PI3K inhibition in inducing cancer cell death has also been reported, but the involvement of MYC regulation is unclear. In this study, we demonstrated that HDAC and PI3K inhibition synergistically downregulates MYC protein levels and induces apoptosis in “double-hit” (DH) diffuse large B-cell lymphoma (DLBCL) cells. Furthermore, CUDC-907, a small-molecule dual-acting inhibitor of both class I and II HDACs and class I PI3Ks, effectively suppresses the growth and survival of MYC-altered or MYC-dependent cancer cells, such as DH DLBCL and BRD–NUT fusion-positive NUT midline carcinoma (NMC) cells, and MYC protein downregulation is an early event induced by CUDC-907 treatment. Consistently, the antitumor activity of CUDC-907 against multiple MYC-driven cancer types was also demonstrated in animal models, including DLBCL and NMC xenograft models, Myc transgenic tumor syngeneic models, and MYC-amplified solid tumor patient-derived xenograft (PDX) models. Our findings suggest that dual function HDAC and PI3K inhibitor CUDC-907 is an effective agent targeting MYC and thus may be developed as potential therapy for MYC-dependent cancers. Mol Cancer Ther; 16(2); 285–99. ©2016 AACR.

Abstract 3744: Antitumor activity of CUDC-907, a dual PI3K and HDAC inhibitor, in hematological cancer models

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-Hodgkin9s 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

Abstract 1879: Dual function HDAC and PI3K inhibitor, CUDC-907 affects cancer cells and the tumor microenvironment in hematological malignancies

Histone deacetylases (HDACs) and the phosphatidylinositol 3-kinase (PI3K)/AKT pathway are promising therapeutic targets in hematologic cancers and evidence of synergistic anti-cancer activity has recently emerged. CUDC-907, a small molecule drug candidate that is designed to target HDACs and PI3Ks in a single chemical entity, is currently in Phase 1 clinical testing for the treatment of patients with lymphoma or multiple myeloma. Preclinically, CUDC-907 has been shown to inhibit activation of PI3K/AKT, JAK/STAT and MAPK pathways in hematologic cancer cell lines such as Hodgkin9s lymphoma, diffuse large B-cell lymphoma, and multiple myeloma. In this study, we report that in the setting of hematological malignancies, CUDC-907 targets not only the cancer cells but also the tumor microenvironment. Cytotoxicity against primary CLL cells was independent of the protective effects provided by stromal cells when primary CLL cells were co-cultured with nurse-like cells. CUDC-907 was shown in vitro to impair cytokine and chemokine production by immune cells in the tumor microenvironment and by Hodgkin9s lymphoma cells. The ongoing first-in-human Phase 1 clinical study of CUDC-907 has yielded preliminary evidence of anti-cancer activity and impact on the tumor microenvironment as measured by cytokine and chemokine levels (e.g., thymus and activation regulated chemokine [TARC]). Ongoing analyses are probing the potential utility of selected cytokine and chemokine as predictive markers of CUDC-907 activity. Citation Format: Anna W. Ma, Ruzanna Atoyan, Anas Younes, Ian W. Flinn, Yasuhiro Oki, Amanda Copeland, Jesus G. Berdeja, Robert Laliberte, Jaye Viner, Maria Elena S. Samson, Steven Dellarocca, Ling Yi, Mylissa Borek, Brian Zifcak, Guangxin Xu, Jing Wang. Dual function HDAC and PI3K inhibitor, CUDC-907 affects cancer cells and the tumor microenvironment in hematological malignancies. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1879. doi:10.1158/1538-7445.AM2014-1879

Abstract 1168: Efficacy of the IRAK4 inhibitor CA-4948 in patient-derived xenograft models of diffuse large B cell lymphoma

IRAK4 kinase activity is required for toll-like receptor (TLR) and interleukin-1 receptor (IL-1R) signaling in a variety of myeloid and lymphoid cell types. Recruitment of IRAK4 to these receptors and its subsequent activation is facilitated by the MYD88 adaptor protein, which is mutated in ~22% of DLBCL cases. The MYD88 L265P activating mutation is found in ~30% of the activated B-cell (ABC) and ~6% of germinal center B-cell (GCB) subtypes of DLBCL and leads to constitutive activation of NF-κB signaling that is associated with worse prognosis. Thus, the development of small molecule inhibitors targeting IRAK4 is an attractive anticancer strategy for MYD88 mutation-containing cancers such as DLBCL. We are developing an IRAK4 inhibitor, CA-4948, as a therapeutic agent for hematological cancers with dysregulated TLR/MYD88/IRAK4 signaling. CA-4948 (previously AU-4948) is a selective and potent IRAK4 kinase inhibitor with in vivo activity in a TLR4-induced cytokine release model. CA-4948 exhibits favorable DMPK properties, oral bioavailability, and is well tolerated in mice. Furthermore, CA-4948 was previously shown to exhibit dose-dependent efficacy in ABC-DLBCL MYD88-L265P xenograft tumor models using cell lines OCI-LY3 and OCI-LY10. Here, we report the efficacy results from testing CA-4948 in a panel of well characterized, patient-derived DLBCL tumor xenograft (PDX) mouse models. CA-4948 exhibited the greatest efficacy in four of the five ABC-DLBCL PDX models tested as compared to GBC-DLBCL and ABC/GCB DLBCL PDX models. Furthermore, CA-4948 was efficacious in ABC-DLBCL PDX tumors containing activating mutations in both TLR/IL-1R and BCR signaling pathways (MYD88 and CD79B double mutants). Interestingly, the one ABC-DLBCL PDX model that failed to respond to CA-4948 treatment contained a MYD88 L265P mutation as well as a BCL6 translocation. While this particular PDX model was resistant to CA-4948, and showed a weak anti-tumor response to single-agent ibrutinib, the combination treatment of ibrutinib and CA-4948 exhibited a synergistic tumor growth inhibition effect. In summary, CA-4948 exhibited anti-tumor activity in ABC-type DLCBL PDX tumor models including those containing combinations of activating mutations in the TLR/IL-1R and BCR signaling pathways. These results underscore the therapeutic potential of IRAK4 kinase inhibition by CA-4948, as a single-agent or in combination with BCR inhibitors, for the treatment of DLBCL. Citation Format: Robert N. Booher, Maria Elena Samson, Guang-Xin Xu, Hongsheng Cheng, David P. Tuck. Efficacy of the IRAK4 inhibitor CA-4948 in patient-derived xenograft models of diffuse large B cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1168. doi:10.1158/1538-7445.AM2017-1168

Abstract 4634: Novel dual HDAC & PI3K inhibitor, CUDC-907, for MYC-driven malignancies

MYC family genes are among the most frequently deregulated oncogenic drivers in human cancer. Pharmacologic inhibition of HDAC activity and blockade of the PI3K pathway have both been shown to suppress MYC-induced transcription. HDAC activity is critical for MYC gene regulation, as MYC represses transcription of target genes through recruitment of HDACs. HDAC inhibitors have been shown to restore expression of genes suppressed by MYC family members and to induce rapid downregulation of expression of MYC itself. The PI3K pathway plays a central role in regulating MYC at the post-transcriptional level. Activation of PI3K signaling leads to activation of AKT, which phosphorylates and inhibits GSK3β. As GSK3β normally phosphorylates MYC which facilitates the degradation of MYC, activation of PI3K signaling leads to increased stability of MYC, whereas PI3K inhibitors decrease MYC stability. A recent study has demonstrated addiction to MYC signaling and hypersensitivity to PI3K inhibition in PTEN-deficient diffuse large B-cell (DLBCL) cell lines, suggesting that MYC-driven cancers may be particularly sensitive to PI3K inhibition. As HDACs and PI3K regulate MYC protein levels and functions through nonoverlapping mechanisms, simultaneous HDAC and PI3K inhibition may further enhance MYC suppression. CUDC-907 is an orally bioavailable, small-molecule dual HDAC and PI3K inhibitor that primarily inhibits class I and II HDACs and the PI3Kα, β, and δ isoforms. CUDC-907 shows greater anti-tumor activity in vitro than single-target HDAC or PI3K inhibitors, especially in MYC-dependent cell types, such as DLBCL and NUT midline carcinoma (NMC). In preclinical testing, CUDC-907 treatment leads to a dose-dependent decrease in MYC protein levels, and is also more potent in decreasing MYC than the HDAC inhibitor panobinostat and the pan-PI3K inhibitor pictilisib alone or in combination. Significant antitumor effects have been consistently observed in MYC-driven DLBCL xenograft and genetically engineered mouse models exposed to CUDC907. In particular, certain MYC translocation (Daudi), double-hit (concurrent MYC and BLC2 translocation, WSUDLCL2 and DOHH2), double-expresser (expression of MYC and BCL2 proteins, U2932) xenograft models, and the Eμ-Myc transgenic mouse model achieve tumor growth inhibition of 100%, 69%, 56%, 97% and 72%, respectively. These findings raise the possibility that hematologic and solid tumors driven by aberrant overexpression of MYC family genes (e.g., MYC-altered DLBCL and NMC) might be more responsive to simultaneous HDAC and PI3K inhibition with CUDC-907 than they are to single-target therapy. Clinical Phase 1 studies are currently testing CUDC-907 in patients with relapsed/refractory (R/R) DLBCL and advanced MYC-aberrant solid tumors. Preliminary data are encouraging and support the planned Phase 2 study in R/R MYC-altered DLBCL, as well as further testing in other MYC-driven malignancies. Citation Format: Kaiming Sun, Ruzanna Atoyan, Mylissa A. Borek, Steven Dellarocca, Maria E. Samson, Anna W. Ma, Guangxin Xu, Troy Patterson, David P. Tuck, Jaye L. Viner, Ali Fattaey, Jing Wang. Novel dual HDAC & PI3K inhibitor, CUDC-907, for MYC-driven malignancies. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4634.

Abstract 4324: Predictive biomarker signatures for IAP inhibitor CUDC-427

The Inhibitors of Apoptosis (IAP) are a family of functionally related proteins that serve as endogenous regulators of apoptosis. The frequent overexpression of IAP proteins allows cancer cells to evade apoptosis and develop drug resistance, making them attractive targets for cancer therapies. CUDC-427 is a potent small molecule IAP antagonist currently tested in a Phase 1 clinical trial for solid tumors and lymphomas. Although only 10% of the cancer cell lines are sensitive to single-agent CUDC-427 in vitro, significant anti-tumor activity has been observed in xenograft models. These observations highlight the importance of identifying patients with sensitive tumors to better target CUDC-427 for specific patient populations. Previously, we have reported TNF family ligand induction and decrease in XIAP levels as potential predictive biomarkers for response to CUDC-427. However, this prediction method requires the detection of biomarker levels in post-treatment samples, which may not always be feasible in clinical setting. Therefore, we sought to assess predictive genetic markers of response to CUDC-427 treatment for patient stratification. Using an in vitro cell viability assay, single-agent activity of CUDC-427 was assessed against a panel of 90 hematological and solid tumor cell lines from the Cancer Cell Line Encyclopedia (CCLE) collection. These results and genomic data available from the CCLE database including gene expression, DNA copy number and mutation status were used in the elastic net analysis to identify predictors associated with drug response. A set of gene signatures containing about 10 significant predictors identified by this approach was further validated and refined in an independent set of 61 CCLE cell lines. The clinical relevance of these gene signatures was validated by searching the cBioPortal Cancer Genomics database. The results indicate that these signatures frequently occur in several solid and hematologic cancers. To further validate this set of gene signatures, single-agent activity of CUDC-427 was evaluated in 30 patient-derived xenograft tumor models and 12 cell-line-derived xenograft models including breast and ovarian cancers as well as lymphomas. Daily treatment with CUDC-427 induced 60% or greater tumor growth inhibition in 20 of the 42 models tested, including 4 highly sensitive models that demonstrated tumor regression. Whole genome data including mutation status, DNA copy number and mRNA expression profiles of these xenograft tumors were assessed to provide independent in vivo validation and to further refine the gene signatures generated in vitro. In conclusion, a set of gene signatures identified through this work can potentially be used as biomarkers to predict in vivo activity of CUDC-427 across multiple tumor types. These results will provide a basis for the development of predictive assays to aid selection of patients whose tumors may be sensitive to CUDC-427 treatment. Citation Format: Kaiming Sun, Ze Tian, Qi Zhang, Maria Samson, Ruzanna Atoyan, Mylissa Borek, Steven Dellarocca, Brian Zifcak, Troy Patterson, Anna W. Ma, Guangxin Xu, Michael J. Wick, Richard Rickles, Jing Wang. Predictive biomarker signatures for IAP inhibitor CUDC-427. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4324. doi:10.1158/1538-7445.AM2015-4324