miR-3132 upregulates surface TRAIL to induce apoptotic cell death in cancer cells

TRAIL-based therapies are of significant clinical interest because of its unique ability to induce apoptosis in cancer cells while sparing normal and untransformed cells. This selective antitumor potential of the TRAIL pathway has been harnessed by development of therapeutics including recombinant (rh)TRAIL and TRAIL-receptor agonist antibodies such as mapatumumab and lexatumumab. While these TRAIL-based therapies have proven successful in preclinical studies and safe in early phase clinical trials, the limited serum half-life has been a hurdle for further clinical development. Here we characterize miR-3132, a novel and first-in class TRAIL-inducing miRNA with potent anti-proliferative and pro-apoptotic effects in cancer cell lines. Initial mechanistic studies indicate that miR-3132 engages the interferon signaling pathway to induce TRAIL and subsequent TRAIL-dependent apoptosis in cancer cell lines. Our data further suggests that the binding of miR-3132 to toll-like receptors could be the upstream pathway for the interferon response. The current study the first report to demonstrate miR-3132's in vitro efficacy and preliminary mechanism of action in cancer cell lines.

Combination of ONC201 and TLY012 induces selective, synergistic apoptosis in vitro and significantly delays PDAC xenograft growth in vivo

The five-year survival rate for pancreatic ductal adenocarcinoma (PDAC) has remained a dismal 9% for approximately 40 years with an urgent need for novel therapeutic interventions. ONC201 is the founding member of the imipridone class, comprised of orally bioavailable small molecules that have shown efficacy in multiple tumor types both in animal models and in Phase I/II clinical trials. ONC201 is a potent inducer of the tumor necrosis factor related apoptosis inducing ligand (TRAIL) pathway. TRAIL is an innate immune mechanism which induces programmed cell death of cancer cells. We observed that PDAC cells upregulated ATF4, CHOP, and DR5 after treatment with ONC201. This occurred in cell lines that are susceptible to ONC201-induced apoptosis and in ones that are not. In response to ONC201, PDAC cells downregulated anti-apoptotic proteins including c-FLIP, BclXL, XIAP, cIAP1, and survivin. We hypothesized that TRAIL receptor agonists might induce selective, synergistic apoptosis in pancreatic cancer cell lines treated with ONC201. We screened 7 pancreatic cancer cell lines and found synergy with ONC201 and rhTRAIL or the novel TRAIL receptor agonist TLY012 in 6 of the 7 cell lines tested. In vivo experiments using BxPC3 and HPAFII xenograft models showed that the combination of ONC201 plus TLY012 significantly delays tumor growth as compared to controls. Immunohistochemical analysis of the tumors after three doses of the combination showed significantly increased cleavage of caspase 3 in vivo as compared to controls. Taken together, the preclinical efficacy of ONC201 and TLY012 represents a novel therapeutic option for further testing in pancreatic cancer patients. This combination showed marked efficacy in tumor cells that are both sensitive and resistant to the pro-apoptotic effects of ONC201, providing rationale to further investigate the combination of ONC201 plus TLY012 in patients with pancreatic cancer.

Antitumorigenic effect of combination treatment with ONC201 and TRAIL in endometrial cancer in vitro and in vivo

ONC201 demonstrated promising activity in patients with advanced endometrial cancer in a Phase I clinical trial. ONC201 activates the integrated stress response (ISR) and upregulates TRAIL and its receptor DR5. We hypothesized ONC201 upregulation of DR5 could sensitize tumors to TRAIL and combination of ONC201 and TRAIL would lead to enhanced cell death in endometrial cancer models. Five endometrial cancer cell lines AN3CA, HEC1A, Ishikawa, RL952, and KLE as well as a murine xenograft model were treated with ONC201 alone or in combination with TRAIL. ONC201 decreased the cell viability of all five endometrial cancer cell lines at clinically achievable low micro-molar concentrations (2–4 μM). ONC201 activated the ISR and induced protein expression of TRAIL and DR5 at the cell surface. Pretreatment with ONC201 sensitized endometrial cancer cell lines to TRAIL, leading to increased cell death induction compared to either agent alone. Tumor growth was reduced in vivo by the ONC201/TRAIL combination treatment in the xenograft model of endometrial cancer (p = .014). Mice treated with combination treatment survived significantly longer than mice from the three control groups (p = .018). ONC201 decreased cell viability in endometrial cancer cells lines primarily through growth arrest while the combination of ONC201 and TRAIL promoted cell death in vitro and in vivo. Our results suggest a novel cancer therapeutic strategy that can be further investigated in the clinic.

TRAIL receptor agonists convert the response of breast cancer cells to ONC201 from anti-proliferative to apoptotic

ONC201 was initially identified as an inducer of cell death through the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) pathway. The compound is currently being tested in patients with hematological malignancies and solid tumors, including those of the breast. We investigated strategies to convert the response of breast cancers to ONC201 from anti-proliferative to apoptotic. ONC201 treatment upregulates TRAIL and primes TRAIL-resistant non-triple negative breast cancer (TNBC) cells to undergo cell death through the extrinsic pathway. Remarkably, the addition of exogenous recombinant human TRAIL (rhTRAIL) converts the response of TRAIL-resistant non-TNBC cells to ONC201 from anti-proliferative to apoptotic in a death receptor 5 (DR5)-dependent manner in vitro. Importantly, normal fibroblasts do not undergo apoptosis following rhTRAIL plus ONC201. In vivo, MDA-MB-361 tumor growth rate is significantly reduced following treatment with a combination of ONC201 and rhTRAIL as compared to control tumors. Natural killer (NK) cells which use TRAIL to kill DR5-expressing cancer cells, exhibit greater cytotoxicity against ONC201-treated breast cancer cells compared to controls. rhTRAIL also converts the response of cells from other tumor types to ONC201 from anti-proliferative to apoptotic. A monoclonal DR5-agonistic antibody converts the response of non-TNBC cells to ONC201 from anti-proliferative to apoptotic. Our findings describe a novel therapeutic strategy that potently converts the response of a cancer cell to ONC201 from anti-proliferative to apoptotic. This approach may be clinically relevant and has potential to induce tumor regression of patient tumors with relative resistance to ONC201 monotherapy.

Abstract 2057: Small molecule CB001 induces extrinsic apoptosis via downregulation of c-FLIP expression in mutant p53-expressing cancer cells

Cellular FADD-like IL-1β-converting enzyme-inhibitory protein (c-FLIP) is a master anti-apoptotic regulator in cancer cells. c-FLIP inhibits caspase 8 activation and suppresses cell apoptosis induced by TNF-related apoptosis-inducing ligand (TRAIL) in malignant cells. Targeting c-FLIP is an attractive strategy for cancer therapy. We previously identified a small-molecule CB001 as a p53-restoring compound and found that CB001 induces cell death with little or no genotoxicity in human colorectal cancer cells. We now show that CB001 downregulates c-FLIP expression in cancer cells at the post-translational level via protein degradation. CB001 treatment induces an increase in caspase 8 activity which correlates with the decrease in c-FLIP at the protein level in mutant p53-expressing cancer cells. Knockdown of caspase 8 rescues cancer cells from CB001-induced apoptosis in mutant p53-expressing cancer cells, suggesting that downregulation of c-FLIP is one of the major mechanisms by which CB001 induces extrinsic cell apoptosis. Furthermore, our studies reveal a synergy between CB001 and TRAIL to induce apoptosis in TRAIL-resistant cancer cells, but not in normal cells at the tested doses. These results taken together suggest that CB001 is a promising lead for drug development with a strong capability to suppress tumor growth through targeting c-FLIP in cancer cells.

Citation Format: Shengliang Zhang, Lanlan Zhou, Marie D. Ralff, Wafik S. El-Deiry. Small molecule CB001 induces extrinsic apoptosis via downregulation of c-FLIP expression in mutant p53-expressing cancer cells [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 2057.

Abstract 258: Recombinant human TRAIL or a DR5 agonistic antibody convert the response of non-triple negative breast cancer cells to ONC201 from anti-proliferative to apoptotic

ONC201 was initially identified as an inducer of cell death through the tumor necrosis factor related apoptosis inducing ligand (TRAIL) pathway. The compound is being tested in patients with a variety of tumor types, including those of the breast. Both triple negative breast cancer (TNBC) cells and non-TNBC cells are sensitive to ONC201. In a subset of TRAIL-sensitive TNBC cells, ONC201 treatment leads to the induction of apoptosis in a TRAIL-dependent manner. In the majority of TRAIL-resistant non-TNBC cells, ONC201’s effects are anti-proliferative rather than apoptotic. In vivo, the apoptotic response to ONC201 leads to efficacy of the compound while the anti-proliferative response does not (Ralff et al., Mol Cancer Ther., 2017). Here we worked to identify strategies to convert the response of cancer cells to ONC201 from anti-proliferative to apoptotic. ONC201 treatment primed TRAIL-resistant non-TNBC cells to undergo TRAIL-dependent cell death. Increases in the mRNA and surface protein levels of death receptor 5 (DR5) as well as decreases in the expression of multiple anti-apoptotic proteins occured in ONC201-treated cells. We also observed small but significant increases in TRAIL mRNA and surface protein in non-TNBC cells following treatment with ONC201. Despite apoptotic priming and the induction of TRAIL, the effect of the compound in the non-TNBC cells remains anti-proliferative but not apoptotic. We hypothesized that the level of TRAIL induced by ONC201 in these cells, known to be TRAIL-resistant, was insufficient. Remarkably, the addition of exogenous recombinant human TRAIL (rhTRAIL) converted the response of TRAIL-resistant non-TNBC cells to ONC201 from anti-proliferative to apoptotic. Cleaved PARP, caspase-3, caspase-9, and caspase-8 were observed in cells treated with ONC201 followed by rhTRAIL, but not in cells treated with ONC201 or rhTRAIL alone. Propidium iodide staining and quantification of the subG1 population via flow cytometry further confirmed these findings. Similar observations about the ability of rhTRAIL to convert the cellular response to ONC201 from anti-proliferative to apoptotic were made in cancer cells from other tumor types. Importantly, rhTRAIL did not convert the response of normal fibroblasts to ONC201 from anti-proliferative to apoptotic. Addition of a DR5 agonistic antibody to ONC201 treated non-TNBC cells also converted the response of the non-TNBC cells to ONC201 from anti-proliferative to apoptotic. Ongoing experiments are currently testing the combination of ONC201 and rhTRAIL in vivo. These findings describe a strategy for potently converting the response of a cancer cell to ONC201 from anti-proliferative to apoptotic. Clinical application of this combination therapy may result in tumor regressions in patients with decreased sensitivity to ONC201 as a single agent.

Citation Format: Marie D. Ralff, Jocelyn E. Ray, Avital Lev, Lanlan Zhou, David T. Dicker, Wafik S. El-Deiry. Recombinant human TRAIL or a DR5 agonistic antibody convert the response of non-triple negative breast cancer cells to ONC201 from anti-proliferative to apoptotic [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 258.

Abstract 5183: ONC201 induces acetylation of histone binding within the p21 (CDKN1A) gene promoter

ONC201/TIC10 is a promising anticancer agent that upregulates cytotoxic TRAIL pathway signaling in cancer cells. Preliminary clinical data indicates ONC201 induces clinical benefit in a subset of patients with histone H3 K27M glioma, among other tumors. Since H3 K27M mutation reduces levels of H3K27 di- and tri-methylation and in turn alters the expression of genes by epigenetic modulation, we investigated ONC201 effects on epigenetic regulation in cancer. We treated the colorectal cancer cell line HCT116 with the histone deacetylase inhibitor entinostat or ONC201. Chromatin immunoprecipitation (ChIP) was performed with anti-histone H3 (acetyl K9) antibody using lysates from drug-treated tumor cells. Immunoprecipitated DNA was probed by PCR using primers across the promoter of p21 (WAF1; CDKN1A). The results indicate that both ONC201 and entinostat induce the acetylation of histone H3 binding within the p21 promoter. We further observed that ONC201 plus entinostat have synergistic effects in this p21 promoter acetylation activity. Activation of p21 gene expression by enhancing histone acetylation may be relevant in cancer suppression by ONC201.

Citation Format: Yiqun Zhang, Lanlan Zhou, Shengliang Zhang, Marie D. Ralff, Shuai Zhao, Philip H. Abbosh, Rahmat Sidker, Wafik S. El-Deiry. ONC201 induces acetylation of histone binding within the p21 (CDKN1A) gene promoter [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 5183.

Abstract LB-082: ONC201 sensitizes resistant breast cancer cells to TRAIL through death receptor 5 upregulation

ONC201 is a potent inducer of cancer cell death through the tumor necrosis factor related apoptosis inducing ligand (TRAIL) pathway. ONC201 and its structural analogs comprise a novel class known as the imipridones. The compound is being tested clinically against a range of solid tumors and hematological malignancies. We found that both triple negative and non-triple negative breast cancer cells are sensitive to ONC201. This was initially surprising, as the majority of non-triple negative breast cancer cells are resistant to TRAIL. In TRAIL-sensitive cells, ONC201 induced cell death in a TRAIL-dependent manner. In TRAIL-resistant cells, the effects of ONC201 are not pro-apoptotic but are rather anti-proliferative. Here we further investigate the effects of ONC201 in TRAIL-resistant breast cancers from multiple molecular subtypes. ONC201 has been previously shown to induce transcriptional upregulation of TRAIL receptor death receptor 5 (DR5). A known mechanism of TRAIL resistance in breast cancer is low cell surface DR5 expression. We hypothesized that pre-treatment with ONC201 would upregulate DR5 and lead to TRAIL sensitization in resistant cells. Our results confirm our hypothesis and show that treatment with ONC201 transcriptionally upregulates DR5 and increases its expression at the cell surface. In addition, pre-treatment with ONC201 sensitizes TRAIL-resistant breast cancer cells to the pro-apoptotic effects of TRAIL. Caspase-8 and PARP are cleaved when cells are treated with the combination of ONC201 and TRAIL, but not when treated with either compound alone. Annexin-V PI staining and quantitation of subG1 DNA content via flow cytometry further confirmed these results. Knockdown of DR5 abrogated TRAIL sensitization by ONC201. Natural killer (NK) cells are known to use TRAIL to kill targets like tumor cells. We are exploring the hypothesis that pre-treatment of tumor cells with ONC201 would increase their killing by NK cells. We are currently investigating the importance of the TRAIL pathway and DR5 upregulation by imipridone compounds in this sensitization to NK cell induced apoptosis. In summary, these results describe a novel mechanism by which ONC201 sensitizes breast cancer cells to the effects of apoptosis inducing ligand TRAIL. They also provide preclinical rationale for the testing of the compound against breast cancers in the clinic.

Citation Format: Marie D. Ralff, Jessica Wagner, Wafik S. El-Deiry. ONC201 sensitizes resistant breast cancer cells to TRAIL through death receptor 5 upregulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-082.

TRAIL pathway targeting therapeutics

Introduction

Despite decades of focused research efforts, cancer remains a significant cause of morbidity and mortality. Tumor necrosis factor(TNF)-related apoptosis-inducing ligand (TRAIL) is capable of inducing cell death selectively in cancer cells while sparing normal cells.

Areas covered

In this review, the authors cover TRA therapy and strategies that have been undertaken to improve their efficacy, as well as unconventional approaches to TRAIL pathway activation including TRAIL-inducing small molecules. They also discuss mechanisms of resistance to TRAIL and the use of combination strategies to overcome it.

Expert commentary

Targeting the TRAIL pathway has been of interest in oncology, and although initial clinical trials of TRAIL receptor agonists (TRAs) showed limitations, novel approaches represent the future of TRAIL-based therapy.

Dose intensification of TRAIL-inducing ONC201 inhibits metastasis and promotes intratumoral NK cell recruitment

ONC201 is a first-in-class, orally active antitumor agent that upregulates cytotoxic TRAIL pathway signaling in cancer cells. ONC201 has demonstrated safety and preliminary efficacy in a first-in-human trial in which patients were dosed every 3 weeks. We hypothesized that dose intensification of ONC201 may impact antitumor efficacy. We discovered that ONC201 exerts dose- and schedule-dependent effects on tumor progression and cell death signaling in vivo. With dose intensification, we note a potent anti-metastasis effect and inhibition of cancer cell migration and invasion. Our preclinical results prompted a change in ONC201 dosing in all open clinical trials. We observed accumulation of activated NK+ and CD3+ cells within ONC201-treated tumors and that NK cell depletion inhibits ONC201 efficacy in vivo, including against TRAIL/ONC201-resistant Bax-/- tumors. Immunocompetent NCR1-GFP mice, in which NK cells express GFP, demonstrated GFP+ NK cell infiltration of syngeneic MC38 colorectal tumors. Activation of primary human NK cells and increased degranulation occurred in response to ONC201. Coculture experiments identified a role for TRAIL in human NK-mediated antitumor cytotoxicity. Preclinical results indicate the potential utility for ONC201 plus anti-PD-1 therapy. We observed an increase in activated TRAIL-secreting NK cells in the peripheral blood of patients after ONC201 treatment. The results offer what we believe to be a unique pathway of immune stimulation for cancer therapy.

ONC201 Targets AR and AR-V7 Signaling, Reduces PSA, and Synergizes with Everolimus in Prostate Cancer

Androgen receptor (AR) signaling plays a key role in prostate cancer progression, and androgen deprivation therapy (ADT) is a mainstay clinical treatment regimen for patients with advanced disease. Unfortunately, most prostate cancers eventually become androgen-independent and resistant to ADT with patients progressing to metastatic castration-resistant prostate cancer (mCRPC). Constitutively activated AR variants (AR-V) have emerged as mediators of resistance to AR-targeted therapy and the progression of mCRPC, and they represent an important therapeutic target. Out of at least 15 AR-Vs described thus far, AR-V7 is the most abundant, and its expression correlates with ADT resistance. ONC201/TIC10 is the founding member of the imipridone class of small molecules and has shown anticancer activity in a broad range of tumor types. ONC201 is currently being tested in phase I/II clinical trials for advanced solid tumors, including mCRPC, and hematologic malignancies. There has been promising activity observed in patients in early clinical testing. This study demonstrates preclinical single-agent efficacy of ONC201 using in vitro and in vivo models of prostate cancer. ONC201 has potent antiproliferative and proapoptotic effects in both castration-resistant and -sensitive prostate cancer cells. Furthermore, the data demonstrate that ONC201 downregulates the expression of key drivers of prostate cancer such as AR-V7 and downstream target genes including the clinically used biomarker PSA (KLK3). Finally, the data also provide a preclinical rationale for combination of ONC201 with approved therapeutics for prostate cancer such as enzalutamide, everolimus (mTOR inhibitor), or docetaxel.Implications: The preclinical efficacy of ONC201 as a single agent or in combination, in hormone-sensitive or castration-resistant prostate cancer, suggests the potential for immediate clinical translation. Mol Cancer Res; 16(5); 754-66. ©2018 AACR.

Abstract P3-06-08: Imipridone compounds inhibit breast cancer mTORC1 signaling through integrated stress response-mediated upregulation of endogenous mTORC1 inhibitor sestrin2

Breast cancer is a major cause of cancer-related death and there is a need for novel therapies with increased efficacy and decreased toxicity. The small molecule ONC201 was initially identified as a TRAIL pathway inducer. The compound has entered early phase clinical trials and is being tested in a range of solid tumors and hematological malignancies. Our previously published data demonstrate that ONC201 has potent anti-proliferative and pro-apoptotic effects in a broad range of breast cancer subtypes through TRAIL-dependent and TRAIL-independent mechanisms. Analogs of ONC201 with a shared pharmacophore have been developed and form the novel “imipridone” class. When compared with ONC201, imipridones ONC206, ONC212, and ONC213 showed increased potency of anti-proliferative or pro-apoptotic effects in breast cancer cells. We were interested in further defining the previously unstudied anti-proliferative effects of the imipridone compounds. Single agent efficacy of potent imipridone ONC212 in a xenograft model of TNBC was observed in the absence of apoptosis induction. This indicates that the anti-proliferative actions of the compound are sufficient for an in vivo anti-tumor effect. Our lab has previously shown that ONC201 activates an ATF4-dependent integrated stress response (ISR), essential for apoptosis induction in colon cancer cells. In contrast, in breast cancer cells, although ATF4 knockdown did not block cell death induced by ONC201 it did partially abrogate the anti-proliferative effects of the compound. The mammalian target of rapamycin complex 1 (mTORC1) is a well-known regulator of cellular growth and proliferation. mTORC1 signaling is inactivated in breast cancer cells following treatment with ONC201 and its analogs ONC212 and ONC213, regardless of whether the cells undergo apoptosis. Knockdown of ATF4 abrogated ONC201-mediated inhibition of p70 S6 kinase and ribosomal protein S6 phosphorylation, linking ISR induction to mTORC1 inhibition. We hypothesized that sestrin2, an endogenous mTORC1 inhibitor known to be upregulated following cellular stress, might represent a link between induction of ATF4 and inhibition of mTORC1. Treatment with ONC201 and its analogs ONC212 and ONC213 in multiple breast cancer cell lines resulted in sestrin2 upregulation. This was blocked by ATF4 knockdown. Furthermore, knockdown of sestrin2 abrogated the effects of ONC201 on mTORC1 signaling in breast cancers from multiple molecular subtypes. Previous mechanistic studies have focused exclusively on the relevance of ATF4 in the pro-apoptotic effects of ONC201. The novel findings described here help to elucidate the mechanism behind the potent and understudied anti-proliferative effects of the imipridones. Our findings also strengthen the preclinical rationale for testing of imipridone compounds against breast cancers regardless of molecular subtype.

Citation Format: Ralff MD, Kline CLB, El-Deiry WS. Imipridone compounds inhibit breast cancer mTORC1 signaling through integrated stress response-mediated upregulation of endogenous mTORC1 inhibitor sestrin2 [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-06-08.

Role of Dopamine Receptors in the Anticancer Activity of ONC201

ONC201/TIC10 is a first-in-class small molecule inducer of TRAIL that causes early activation of the integrated stress response. Its promising safety profile and broad-spectrum efficacy in vitro have been confirmed in Phase I/II trials in several advanced malignancies. Binding and reporter assays have shown that ONC201 is a selective antagonist of the dopamine D2-like receptors, specifically, DRD2 and DRD3. We hypothesized that ONC201's interaction with DRD2 plays a role in ONC201's anticancer effects. Using cBioportal and quantitative reverse-transcription polymerase chain reaction analyses, we confirmed that DRD2 is expressed in different cancer cell types in a cell type-specific manner. On the other hand, DRD3 was generally not detectable. Overexpressing DRD2 in cells with low DRD2 levels increased ONC201-induced PARP cleavage, which was preceded and correlated with an increase in ONC201-induced CHOP mRNA expression. On the other hand, knocking out DRD2 using CRISPR/Cas9 in three cancer cell lines was not sufficient to abrogate ONC201's anticancer effects. Although ONC201's anticancer activity was not dependent on DRD2 expression in the cancer cell types tested, we assessed the cytotoxic potential of DRD2 blockade. Transient DRD2 knockdown in HCT116 cells activated the integrated stress response and reduced cell number. Pharmacological antagonism of DRD2 significantly reduced cell viability. Thus, we demonstrate in this study that disrupting dopamine receptor expression and activity can have cytotoxic effects that may at least be in part due to the activation of the integrated stress response. On the other hand, ONC201's anticancer activity goes beyond its ability to antagonize DRD2, potentially due to ONC201's ability to activate other pathways that are independent of DRD2. Nevertheless, blocking the dopamine D1-like receptor DRD5 via siRNA or the use of a pharmacological antagonist promoted ONC201-induced anticancer activity.

ONC201: a new treatment option being tested clinically for recurrent glioblastoma

Glioblastoma is an aggressive central nervous system tumor with a 5-year-survival rate of less than 10%. Patients diagnosed with the disease are treated with surgery, radiation and temozolomide chemotherapy. Despite survival benefits, patients eventually relapse. There is a need for new treatments with improved efficacy. Imipridone ONC201 is a small molecule originally identified as a TNF-related apoptosis inducing ligand (TRAIL)-inducing compound. ONC201 has the unique ability to induce expression of both pro-death ligand TRAIL and its receptor DR5 through engagement of the cellular integrated stress response (ISR) pathway. Arrillaga-Romany et al. report early results from futility analysis of a phase II clinical trial of ONC201 in 17 patients with recurrent or refractory glioblastoma conducted at the Massachusetts General Hospital Cancer Center. The results are promising, as ONC201 shows preliminary signs of efficacy. Further testing of ONC201 in an expansion cohort of patients with glioblastoma is ongoing.

Anti-pancreatic cancer activity of ONC212 involves the unfolded protein response (UPR) and is reduced by IGF1-R and GRP78/BIP

Pancreatic cancer is chemo-resistant and metastasizes early with an overall five-year survival of ∼8.2%. First-in-class imipridone ONC201 is a small molecule in clinical trials with anti-cancer activity. ONC212, a fluorinated-ONC201 analogue, shows preclinical efficacy in melanoma and hepatocellular-cancer models. We investigated efficacy of ONC201 and ONC212 against pancreatic cancer cell lines (N=16 including 9 PDX-cell lines). We demonstrate ONC212 efficacy in 4 in-vivo models including ONC201-resistant tumors. ONC212 is active in pancreatic cancer as single agent or in combination with 5-fluorouracil, irinotecan, oxaliplatin or RTK inhibitor crizotinib. Based on upregulation of pro-survival IGF1-R in some tumors, we found an active combination of ONC212 with inhibitor AG1024, including in vivo. We show a rationale for targeting pancreatic cancer using ONC212 combined with targeting the unfolded-protein response and ER chaperones such as GRP78/BIP. Our results lay the foundation to test imipridones, anti-cancer agents, in pancreatic cancer, that is refractory to most drugs.

Cancer stem cell-related gene expression as a potential biomarker of response for first-in-class imipridone ONC201 in solid tumors

Cancer stem cells (CSCs) correlate with recurrence, metastasis and poor survival in clinical studies. Encouraging results from clinical trials of CSC inhibitors have further validated CSCs as therapeutic targets. ONC201 is a first-in-class small molecule imipridone in Phase I/II clinical trials for advanced cancer. We have previously shown that ONC201 targets self-renewing, chemotherapy-resistant colorectal CSCs via Akt/ERK inhibition and DR5/TRAIL induction. In this study, we demonstrate that the anti-CSC effects of ONC201 involve early changes in stem cell-related gene expression prior to tumor cell death induction. A targeted network analysis of gene expression profiles in colorectal cancer cells revealed that ONC201 downregulates stem cell pathways such as Wnt signaling and modulates genes (ID1, ID2, ID3 and ALDH7A1) known to regulate self-renewal in colorectal, prostate cancer and glioblastoma. ONC201-mediated changes in CSC-related gene expression were validated at the RNA and protein level for each tumor type. Accordingly, we observed inhibition of self-renewal and CSC markers in prostate cancer cell lines and patient-derived glioblastoma cells upon ONC201 treatment. Interestingly, ONC201-mediated CSC depletion does not occur in colorectal cancer cells with acquired resistance to ONC201. Finally, we observed that basal expression of CSC-related genes (ID1, CD44, HES7 and TCF3) significantly correlate with ONC201 efficacy in >1000 cancer cell lines and combining the expression of multiple genes leads to a stronger overall prediction. These proof-of-concept studies provide a rationale for testing CSC expression at the RNA and protein level as a predictive and pharmacodynamic biomarker of ONC201 response in ongoing clinical studies.

Preclinical evaluation of the imipridone family, analogs of clinical stage anti-cancer small molecule ONC201, reveals potent anti-cancer effects of ONC212

Anti-cancer small molecule ONC201 upregulates the integrated stress response (ISR) and acts as a dual inactivator of Akt/ERK, leading to TRAIL gene activation. ONC201 is under investigation in multiple clinical trials to treat patients with cancer. Given the unique imipridone core chemical structure of ONC201, we synthesized a series of analogs to identify additional compounds with distinct therapeutic properties. Several imipridones with a broad range of in vitro potencies were identified in an exploration of chemical derivatives. Based on in vitro potency in human cancer cell lines and lack of toxicity to normal human fibroblasts, imipridones ONC206 and ONC212 were prioritized for further study. Both analogs inhibited colony formation, and induced apoptosis and downstream signaling that involves the integrated stress response and Akt/ERK, similar to ONC201. Compared to ONC201, ONC206 demonstrated improved inhibition of cell migration while ONC212 exhibited rapid kinetics of activity. ONC212 was further tested in >1000 human cancer cell lines in vitro and evaluated for safety and anti-tumor efficacy in vivo. ONC212 exhibited broad-spectrum efficacy at nanomolar concentrations across solid tumors and hematological malignancies. Skin cancer emerged as a tumor type with improved efficacy relative to ONC201. Orally administered ONC212 displayed potent anti-tumor effects in vivo, a broad therapeutic window and a favorable PK profile. ONC212 was efficacious in vivo in BRAF V600E melanoma models that are less sensitive to ONC201. Based on these findings, ONC212 warrants further development as a drug candidate. It is clear that therapeutic utility extends beyond ONC201 to include additional imipridones.

ONC201 Demonstrates Antitumor Effects in Both Triple-Negative and Non-Triple-Negative Breast Cancers through TRAIL-Dependent and TRAIL-Independent Mechanisms

Breast cancer is a major cause of cancer-related death. TNF-related apoptosis-inducing ligand (TRAIL) has been of interest as a cancer therapeutic, but only a subset of triple-negative breast cancers (TNBC) is sensitive to TRAIL. The small-molecule ONC201 induces expression of TRAIL and its receptor DR5. ONC201 has entered clinical trials in advanced cancers. Here, we show that ONC201 is efficacious against both TNBC and non-TNBC cells (n = 13). A subset of TNBC and non-TNBC cells succumbs to ONC201-induced cell death. In 2 of 8 TNBC cell lines, ONC201 treatment induces caspase-8 cleavage and cell death that is blocked by TRAIL-neutralizing antibody RIK2. The proapoptotic effect of ONC201 translates to in vivo efficacy in the MDA-MB-468 xenograft model. In most TNBC lines tested (6/8), ONC201 has an antiproliferative effect but does not induce apoptosis. ONC201 decreases cyclin D1 expression and causes an accumulation of cells in the G₁ phase of the cell cycle. pRb expression is associated with sensitivity to the antiproliferative effects of ONC201, and the compound synergizes with taxanes in less sensitive cells. All non-TNBC cells (n = 5) are growth inhibited following ONC201 treatment, and unlike what has been observed with TRAIL, a subset (n = 2) shows PARP cleavage. In these cells, cell death induced by ONC201 is TRAIL independent. Our data demonstrate that ONC201 has potent antiproliferative and proapoptotic effects in a broad range of breast cancer subtypes, through TRAIL-dependent and TRAIL-independent mechanisms. These findings develop a preclinical rationale for developing ONC201 as a single agent and/or in combination with approved therapies in breast cancer. Mol Cancer Ther; 16(7); 1290-8. ©2017 AACR.