Paul Gonzales

Synthesis of improved lysomotropic autophagy inhibitors.

Autophagy is a conserved cellular pathway used to recycle nutrients through lysosomal breakdown basally and under times of stress (e.g., nutrient deprivation, chemotherapeutic treatment). Oncogenes are known to induce autophagy, which may be exploited by cancers for cell survival. To identify autophagy inhibitors with potential therapeutic value for cancer, we screened a panel of antimalarial agents and found that quinacrine (QN) had 60-fold higher potency of autophagy inhibition than chloroquine (CQ), a well-known autophagy inhibitor that functions by disrupting lysosomal activity. Despite desirable autophagy inhibiting properties, QN showed considerable cytotoxicity. Therefore, we designed and synthesized a novel series of QN analogs and investigated their effects on autophagy inhibition and cell viability. Notably, we found two compounds (33 and 34), bearing a backbone of 1,2,3,4-tetrahydroacridine, had limited cytotoxicity yet strong autophagy inhibition properties. In conclusion, these improved lysomotropic autophagy inhibitors may have use as anticancer agents in combination with conventional therapies.

Identification of novel HDAC inhibitors through cell based screening and their evaluation as potential anticancer agents

A series of benzimidazole based HDAC inhibitors have been rationally designed, synthesized and screened. The SAR of this new chemotype is described. The lead compound, 11e, showed strong activity in several cellular assays and demonstrated in vivo efficacy in mouse xenograft pancreatic cancer models.

Preclinical investigation of nanoparticle albumin-bound paclitaxel as a potential treatment for adrenocortical cancer.

Background:Traditional drug discovery methods have a limited role in rare cancers. We hypothesized that molecular technology including gene expression profiling could expose novel targets for therapy in adrenocortical carcinoma (ACC), a rare and lethal cancer. SPARC (secreted protein acidic rich in cysteine) is an albumin-binding matrix-associated protein that is proposed to act as a mechanism for the increased efficacy of a nanoparticle albumin-bound preparation of the antimicrotubular drug Paclitaxel (nab-paclitaxel). Methods:The transcriptomes of 19 ACC tumors and 4 normal adrenal glands were profiled on Affymetrix U133 Plus2 expression microarrays to identify genes representing potential therapeutic targets. Immunohistochemical analysis for target proteins was performed on 10 ACC, 6 benign adenomas, and 1 normal adrenal gland. Agents known to inhibit selected targets were tested in comparison with mitotane in the 2 ACC cell lines (H295R and SW-13) in vitro and in mouse xenografts. Results:SPARC expression is increased in ACC samples by 1.56 ± 0.44 (&mgr; ± SD) fold. Paclitaxel and nab-paclitaxel show in vitro inhibition of H295R and SW-13 cells at IC50 concentrations of 0.33 &mgr;M and 0.0078 &mgr;M for paclitaxel and 0.35 &mgr;M and 0.0087 &mgr;M for nab-paclitaxel compared with mitotane concentrations of 15.9 &mgr;M and 46.4 &mgr;M. In vivo nab-paclitaxel treatment shows a greater decrease in tumor weight in both xenograft models than mitotane. Conclusions:Biological insights garnered through expression profiling of ACC tumors suggest further investigation into the use of nab-paclitaxel for the treatment of ACC.

Abstract 3698: ODSH, a heparin derivative, enhances the efficacy of gemcitabine in a refractory human pancreatic tumor xenograft model

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL ODSH, a new chemical entity, is 2-0, 3-0 desulfated heparin, a desulfated heparin analog that has been shown to bind to the receptor for advanced glycation endproducts (RAGE). This interaction prevents RAGE from binding to a principal ligand, HMGB1, as well as to other ligands including S-100 calgranulin, which attenuates the activation of RAGE. RAGE activation is known to induce resistance to chemotherapy and promote pancreatic tumor cell survival. We have shown, in vivo, an increase in response with gemcitabine when combined with ODSH. ODSH was tested alone and in combination with standard of care agent, gemcitabine, against BxPC-3 human pancreatic tumor xenograft model. Single agent ODSH and gemcitabine treatment showed an 18.8% and 16.8% decrease in tumor weight, respectively. The combination regimen of ODSH and gemcitabine increased tumor growth inhibition to 37.9%. This decrease was statistically significant (P<0.05) compared to ODSH and gemcitabine treatments alone according to Students t-test. We believe this is a novel approach to treat metastatic pancreatic cancer. ODSH has already shown a favorable safety profile in Phase I and II studies. A clinical trial with ODSH treatment in combination with gemcitabine+nab-paclitaxel in newly diagnosed patients with metastatic pancreatic cancer is underway. 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 3698. doi:1538-7445.AM2012-3698

Abstract 978: Inhibition of Polo-like kinase 1 as a strategy in the treatment of adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is an aggressive cancer with a 5-year survival rate of 20-30%. Mitotane is the only approved drug for the treatment of patients with ACC. It often carries significant toxicities which result in the discontinuation of treatment. There are no approved second line therapies. The increased incidence of ACC in the cancer predisposition syndrome, Li-Fraumeni, suggests the involvement of the p53 pathway in ACC pathogenesis. Our analysis of the gene expression profiles of 19 ACC samples identified dysregulation of the G2/M transition and the activity of the p53 modulator, MDM2 as important in ACC pathogenesis. Polo-like kinase-1 (PLK1) is involved in the G2/M transition and acts to promote MDM2 activity through its phosphorylation. We observed that PLK1 inhibition by siRNA results in up to a 70% reduction in viability in the ACC cell lines SW-13 and H295R. Therefore, we studied PLK1 inhibition as a potential therapeutic strategy. We used the small molecule inhibitor, BI-2536, to inhibit PLK1 function in SW-13 and H295R. Drug-dose response curves demonstrated that both cell lines are sensitive to pharmacological inhibition of PLK1 (IC50 doses of 0.0094815 μM and 0.062805 μM for SW-13 and H295R, respectively.) Murine xenograft studies demonstrated that BI-2536 resulted in a statistically significant reduction in tumor growth in SW-13 but not H295R. Examination of p53 protein levels in the presence of the drug showed a dose-dependent reduction in p53 levels in SW-13, which carries a homozygous p53 mutation. The same was not true in H295R, which is p53 wild-type. To test the hypothesis that BI-2536 was decreasing mutant p53 levels by promoting its proteasomal degradation, both cell lines were treated with previously determined inhibitory concentrations of BI-2536, either alone or in combination with the proteasome inhibitor, MG132. Western blot analysis showed recovery of p53 protein when cells were concomitantly treated with MG132, supporting a role for BI-2536 as a regulator of proteasomal degradation. Both ACC cell lines are relatively insensitive to MDM2 inhibition by nutlin-3 (NCI60 GI50 values range from ∼4 uM to ∼2 uM versus ACC cell lines @13-15uM), possibly because PLK1 stimulates MDM2 and renders nutlin-3 ineffective. We therefore assessed the ability of BI-2536 to sensitize ACC cell lines to the effects of the MDM2 inhibitor. BI-2636 did show synergy with nutlin-3, shifting the IC50 in SW-13 from 19.78 μM to 6.45 μM and from 12.75 μM to 2.84 μM in H295R. These results demonstrate that inhibition of PLK1 alone or in combination with an MDM2 inhibitor warrants further investigation as a treatment for patients with ACC. Cells with mutant p53 are more sensitive to the growth inhibitory effects of BI-2536. In the context of wild-type p53, the combined inhibition of both PLK1 and MDM2 results in loss of viability. Further clinical development of PLK1 as a target should take p53 mutation status into account. 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 978. doi:1538-7445.AM2012-978

Abstract A184: Activity of plinabulin in tumor models with Kras mutations

Kras mutations, particularly at codons 12 and 13, are reported to occur in up to one-third of human cancer cells and are considered to be undruggable targets (Stoize et al, 2015). These mutations are especially prevalent in NSCLC and CRC. Plinabulin is a new chemical entity in Phase 3, with a multi-faceted mechanism of action, including anti-angiogenesis, inhibition of tubulin polymerization and activation of JNK, which is downstream of the Kras pathway. The combination of these vascular mechanisms together with activity downstream from Kras, suggests that plinabulin could express anti-tumor activity in the presence of Kras mutations. The present report summarizes the findings with plinabulin on tumors with Kras mutations (p.12V, p.12D, p.D153V, p.G12A, p.G12C, p.G12D, p.G12V or p.G13D) in vitro and in vivo. In vitro, plinabulin was very potent (IC50 7-33 nM) as a cytotoxic agent against CRC cell lines containing a Kras mutation at p.G13D (LoVo, HCT-15, HCT116) or a BRAF + P53 mutation (HT-29) and against multiple myeloma cell lines (Singh et al, Blood, 2010) with either Nras or p.G12A mutations (IC50 In vivo, plinabulin was tested as a single agent and in combination with SOC in the CRC Kras mutation murine models LoVo and HCT-15 and the P53/Braf mutant model HT-29, the NSCLC Kras mutation model A549, the multiple myeloma Kras mutation model MM.1S and the breast Kras mutation model MDA-MB-231. As a single agent plinabulin was at most moderately active in these models, with the greatest activity seen in the LoVo, HCT-15, and MDA-MB-231 models (TGI 21-43%); the exception was a marked single agent activity observed in the MM.1S model. However, in all cases plinabulin significantly increased the anti-tumor activity of the standard of care agents (TGI 59-84%, with several CRs and increased tolerability as compared to SOC alone). In summary, plinabulin exhibits a potent anti-tumor activity either in vitro, or in vivo as a single agent or in combination with SOC agents. This activity is observed across several tumor types and mutations, but the spectrum of activity does not extend across all tumor types (e.g. inactive in vivo in Kras mutations for pancreatic cancer or melanoma). These findings are encouraging in terms of clinical studies in Kras mutations in MM, NSCLC, CRC and breast cancers. Citation Format: George Kenneth Lloyd, Lihua Du, Gloria Lee, Jessica Dalsing-Hernandez, Kari Kotlarczyk, Paul Gonzales, Steffan Nawrocki, Jennifer Carew, Lan Huang. Activity of plinabulin in tumor models with Kras mutations. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A184.