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Here we describe a novel class of pan-RAS inhibitor with highly potent and selective anticancer activity by killing cancer cells harboring mutations in RAS or with constitutively activated RAS resulting from mutations in upstream signaling components. A lead compound from this chemical family, ADT-007, binds RAS when in a nucleotide free transitional state to block loading of GTP, thereby interfering with RAS activation and disruption of binding to effectors such as RAF and PI3K to suppress MAPK and AKT signaling. ADT-007 potently inhibits the growth of cultured human and murine cancer cell lines with single-digit nM IC50 values irrespective of specific RAS isozyme or mutational codon. ADT-007 also inhibits tumor growthin vivothrough inhibition of RAS-MAPK signaling in syngeneic, immune competent and xenogeneic, immune deficient mouse models of colon and pancreatic cancer. In RAG 1-/-mice the activity of ADT-007 is partially inhibited indicating a role for the adaptive immune system in ADT-007-mediated tumor growth inhibition.Ex vivoanalyses of tumor infiltrating leukocytes, reveals that ADT-007 enhances T cell functions in the pancreatic and colorectal tumor immune microenvironment.SIGNIFICANCEADT-007 represents a 1st-in-class pan-RAS inhibitor with broad anticancer activity across all RAS driven cancers and unique chemical selectivity to allow normal cells to be spared from pan-RAS inhibition. ADT-007 also has the potential to modulate the adaptive immune response in colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDA). These data support future clinical trials of an orally bioavailable prodrug of ADT-007 as a monotherapy for the treatment of patients with CRC or PDAC regardless of the underlying mutation or in combination with immunotherapy.

PDF file - 981KB, Representative Immunohistochemistry for CHD7 Expression in Primary Tumor Tissue (S1). Network Analysis via MetaCore ExPlain Process Network Analysis for genes involved in CHK1, CDC25A, AURKB, PLK1, HUS1 pathway (S2). CHD7 Knockdown Causes Gemcitabine Sensitization (S3). Mice with Xenograft Tumors Showed No Significant Difference in Body Weight (S4). CHD7 Knockdown Effect on Cell Cycle (S5). Gemcitabine Does Not Significantly Change CHD7 Protein Levels in Cells (S6).

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XLS file - 675KB, Full Results of Primary Gemcitabine Sensitivity Screen (S1). Known DNA Damage Response Genes Identified as Hits in Gemcitabine Sensitivity Screen (S2). Dysregulation, Differential Expression, and Literature RNAi Cross-Reference for Known DDR Genes and Select Hits (S3). Selected Top 15% of Gemcitabine Sensitivity Genes Tested on Secondary Screen (S4).

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with poor outcomes with current therapies. Gemcitabine is the primary adjuvant drug used clinically, but its effectiveness is limited. In this study, our objective was to use a rationale-driven approach to identify novel biomarkers for outcome in patients with early-stage resected PDAC treated with adjuvant gemcitabine. Using a synthetic lethal screen in human PDAC cells, we identified 93 genes, including 55 genes linked to DNA damage responses (DDR), that demonstrated gemcitabine sensitization when silenced, including CHD7, which functions in chromatin remodeling. CHD7 depletion sensitized PDAC cells to gemcitabine and delayed their growth in tumor xenografts. Moreover, CHD7 silencing impaired ATR-dependent phosphorylation of CHK1 and increased DNA damage induced by gemcitabine. CHD7 was dysregulated, ranking above the 90th percentile in differential expression in a panel of PDAC clinical specimens, highlighting its potential as a biomarker. Immunohistochemical analysis of specimens from 59 patients with resected PDAC receiving adjuvant gemcitabine revealed that low CHD7 expression was associated with increased recurrence-free survival (RFS) and overall survival (OS), in univariate and multivariate analyses. Notably, CHD7 expression was not associated with RFS or OS for patients not receiving gemcitabine. Thus, low CHD7 expression was correlated selectively with gemcitabine sensitivity in this patient population. These results supported our rationale-driven strategy to exploit dysregulated DDR pathways in PDAC to identify genetic determinants of gemcitabine sensitivity, identifying CHD7 as a novel biomarker candidate to evaluate further for individualizing PDAC treatment. Cancer Res; 74(10); 2677–87. ©2014 AACR.

A variety of organisms have been shown to have altered physiology or developed pathology due to gene transfer, but mammals have never been shown to do so. Here, we show that circulating tumor DNA (ct) can promote cell-specific horizontal gene transfer (HGT) between human cancer cells and explain the mechanisms behind this phenomenon. Once ctDNA enters the host cell, it migrates to the nucleus and integrates into the cell’s genome, thereby transferring its genetic information. We determine that retrotransposons of the ERVL, SINE, and LINE families are necessary for cell targeting and the integration of ctDNA into host DNA. Using chemically synthesized retrotransposons, we found that AluSp and MER11C reproduced multiple myeloma’s (MM) ctDNA’s cell targeting and integration into MM cells. We also discovered that ctDNA might, as a result of HGT, influence the treatment response of multiple myeloma and pancreatic cancer models. Overall, this is the first study to show that retrotransposon-directed HGT can promote genetic material transfer in cancer. There is, however, a broader impact of our findings than just cancer since cell-free DNA has also been found in physiological and other pathological conditions as well. Furthermore, with the discovery of transposons-mediated tissue-specific targeting, a new avenue for the delivery of genes and therapies will emerge.

Pancreatic ductal adenocarcinoma (PDA) is the 4th leading cause of cancer death in the U.S. with only about a 10% five-year survival rate and an estimated 60,000 deaths/year by 2030. Poor survival is frequently due to advanced disease at the time of diagnosis, as well as the high prevalence of KRAS driver mutations. Currently, approved KRAS-targeted therapeutics are designed to covalently inactivate only KRAS-G12C mutants, whereas the most common mutations in PDA are KRAS-G12D, KRAS-G12V, and KRAS-G12R. Thus, the need for novel RAS-targeted therapeutics with efficacy in tumors with these more common mutations is of utmost urgency to reduce PDA disease burden. We have synthesized a novel chemical class of pan-RAS inhibitors with unique biological properties and attractive drug-like properties. As a prodrug, ADT-1004, generates an active metabolite, ADT-007, that potently inhibits the growth of human and murine PDA cell lines in vitro with single-digit nM IC50 irrespective of specific RAS mutational codon or isozyme by inhibiting activated RAS and signaling downstream of KRAS (ERK1/2 and AKT phosphorylation). ADT-1004 is well tolerated with no discernable toxicity at oral dosages of up to 175 mg/kg bid. Pharmacokinetic studies demonstrated that ADT-1004 produces sustained plasma concentrations of ADT-007 ~50-fold above IC50 values, with even higher concentrations in both subcutaneous and orthotopic pancreatic tumors. Once daily oral administration of ADT-1004 significantly inhibited the growth of orthotopically implanted PDA tumors with a corresponding reduction in RAS/MAPK signaling. ADT-1004 represents a 1st-in-class pan-RAS inhibitor with potential advantages over mutant-specific KRAS inhibitors for greater efficacy and ability to avert mechanisms of resistance. These data support future clinical trials of ADT-1004 as a monotherapy for the treatment of patients with PDA regardless of the underlying mutation. Citation Format: Yulia Y. Maxuitenko, Jeremy B. Foote, Adam B. Keeton, Xi Chen, Kristy Berry, Khalda Fadlalla, Jacob Valiyaveettil, Chung-Hui Huang, Austin M. Moore, Emily C. Graff, Ganji P. Nagaraju, Julienne L. Carstens, Bassel F. El-Rayes, Donald J. Buchsbaum, Gary A. Piazza. Antitumor activity of 1st-in-class pan-RAS inhibitor ADT-1004 in mouse models of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB322.

Pancreatic ductal adenocarcinoma (PDAC) has a prominent fibrotic stroma, which is a result of interactions between tumor, immune and pancreatic stellate cells (PSC). Prior work from our laboratory has defined a role for stroma-derived cytokines such as IL-6 as a significant barrier restraining immunity against PDAC. Our group is pursuing novel approaches to target pathways in the tumor microenvironment (TME), in an effort to improve access of effector immune cells to PDAC and response to immunotherapy. Heat shock protein-90 (Hsp90), is a chaperone protein and a versatile target in pancreatic cancer. Hsp90 regulates a diverse array of cellular processes of relevance to both the tumor and the immune system. However, to date the role of Hsp90 in PSC has not been explored in detail. We hypothesize that targeting Hsp90 can modulate the TME, through its ability to target inflammatory signaling and cytokine production by PSC and enhance the efficacy of immunotherapy. Treatment of immortalized and primary patient PSC with the Hsp90 inhibitor XL888 led to decreased IL-6 at the transcript and protein level in vitro. XL888 directly limited PSC growth, and reduced expression of alpha-SMA, Jak/STAT and MAPK signaling intermediates as determined via immunoblot. Combined therapy with XL888 and anti-PD-1 was efficacious in C57BL/6 mice bearing syngeneic subcutaneous (Panc02) or orthotopic (KPC-Luc) tumors, as compared to treatment with either agent alone. The treatment was well-tolerated, with no difference in body weight observed in either model. Laboratory studies are assessing immune and stromal biomarkers to define the impact on PSC, cytokines and T-cell biomarkers in the TME. Finally, we have completed the dose escalation phase of a Phase Ib/II clinical trial of XL888 (Hsp90i) and pembrolizumab (anti-PD-1) at our institution. Expansion cohorts of patients with metastatic pancreatic cancer (n=16) or colorectal cancer (n=16) are now accruing, with paired biopsy and peripheral blood samples to address the impact of Hsp90 inhibition on anti-PD-1 mediated T cell proliferation, cytokine production, and PSC-derived cytokine signatures. Citation Format: Mohammad Zaidi, Yuchen Zhang, Michael B. Ware, Matthew R. Farren, Hannah Komar, Brian Olson, Ganji P. Nagaraju, Mehmet Akce, Olatunji Alese, Shishir Maithel, Juan Sarmiento, Walid Shaib, Christina Wu, Bassel El-Rayes, Gregory B. Lesinski. Heat shock protein 90 inhibitors alter pancreatic stellate cell cytokine production and enhances the efficacy of immune checkpoint blockade in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4074.

One feature of pancreatic ductal adenocarcinoma (PDAC) is the fibrotic stroma, which is a result of interactions between tumor cells, immune suppressive cells and pancreatic stellate cells (PSC). Stroma-derived cytokines including IL-6 represent a significant barrier restraining immunity against PDAC. Targeting pathways in the tumor microenvironment (TME) that regulate cytokine secretion can be an innovative means to improve access of effector immune cells to PDAC. We hypothesize that targeting Hsp90 can modulate the TME, through its ability to target inflammatory signaling and cytokine production by PSC and enhance the efficacy of immunotherapy. The Hsp90 inhibitor XL888 led to a concentration-dependent inhibition of IL-6 and MCP-1 production by PSC in vitro. Concurrently, PSC displayed growth inhibition as determined by MTT assay, and reduced alpha-SMA expression, a marker of cell activation. Inhibition of Jak/STAT and MAPK signaling was confirmed via immunoblot. These data compliment our published results indicating that Hsp90 inhibitors modulate survival pathways and PDAC growth in vitro and in vivo. This has led to an investigator-initiated Phase Ib/II clinical trial of XL888 (Hsp90i) and pembrolizumab (anti-PD-1) now accruing at our institution. Extensive laboratory correlative studies are ongoing to examine the impact of Hsp90 inhibition on anti-PD-1 mediated T cell proliferation, cytokine production, and impact on PSC-derived cytokine signatures. This work is being performed in paired biopsy samples (pre- and on-treatment), and peripheral blood from expansion cohorts of patients with metastatic pancreatic cancer (n=16) or colorectal cancer (n=16).