Antitumor Activity In Preclinical Models Research Articles

Abstract 2214: GITR ligand fusion protein (GITRL-Fc) induces T cell mediated anti-tumor immune response and can combine with anti-PDL1 to enhance anti-tumor immunity and long-term immune memory

Abstract GITRL (Glucocorticoid-Induced Tumor Necrosis Factor Receptor Ligand, TNFSF18) is a member of the TNF superfamily and naturally exists as a membrane-anchored type II protein that self assembles as a trimer. GITRL activates the co-stimulatory receptor GITR. GITR is found primarily on activated T effector (Teff) cells and regulatory T (Treg) cells. Co-stimulation of GITR by agonist agents is hypothesized to promote anti-tumor immunity by enhancing Teff cell activity and inhibiting Treg suppression. We generated a novel single-gene GITRL trimer fused to an immunoglobulin Fc domain (GITRL-Fc). GITRL-Fc activated GITR signaling more effectively than prototype GITR agonist antibody DTA-1. GITRL-Fc promoted a robust anti-tumor immune response in multiple syngeneic mouse tumor models. GITRL-Fc enhanced tumor specific T-cell responses, particularly of the Th1 type, and also led to reduction in Treg-mediated immunesuppressive activity. GITRL-Fc displayed single agent activity in inhibiting tumor growth and promoting complete tumor rejection in the murine CT26 colon carcinoma model and combination activity with anti-PDL1 as compared to anti-PDL1 and control IgG2a alone. Mice “cured” with GITRL or GITRL/anti-PDL1 combination treatments were protected from re-challenge with tumor cells, suggesting the existence of immunologic memory. More mice were protected from tumor re-challenge with the combination of GITRL-Fc and anti-PDL1, as compared to GITRL-Fc alone. Our results demonstrate that agonist GITRL-Fc induces potent T cell responses, overcomes Treg inhibition, and promotes anti-tumor activity in preclinical models as a single agent or in combination with anti PDL1. The mechanism of tumor eradication and induction of long-term immune memory response by the combination is under investigation and will be discussed at the presentation. Citation Format: Minu K. Srivastava, Rui Yun, Erin Mayes, Hyun_Bae Jie, Fumiko Axelrod, Jorge Monteon, Ming-Hong Xie, John Lewicki, Tim Hoey, Austin Gurney, Angie Inkyung Park. GITR ligand fusion protein (GITRL-Fc) induces T cell mediated anti-tumor immune response and can combine with anti-PDL1 to enhance anti-tumor immunity and long-term immune memory. [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 2214.

Abstract 2232: Immune-inflammatory markers predict the outcome of metastatic colorectal cancer patients treated with the thymidylate synthase poly-epitope peptide (TSPP) vaccine: results from a multi-arm TSPP/VAC phase Ib program

Abstract Thymidylate synthase (TS) is a tumor-associated enzyme critical for DNA replication. TSPP is a poly-epitope-peptide vaccine to TS, which elicits a multi-epitopic CTL response with antitumor activity in preclinical models. TSPP has been tested in 50 advanced cancer patients enrolled in a multi-arm dose-finding TSPP/VAC1 phase Ib trial program (Eudract:# 2009-016897-33)(Table1) between May 2011 and January 2013. The trial results revealed that TSPP is safe and immune-biologically active, and provided preliminary evidence of a antitumor activity in pretreated mCRC patients (Cusi MG et al 2015 and Correale P et al 2015). This population of 41 patients presented a progression-free-survival and an overall-survival (OS) of 6.9 and 11.3 months, respectively, with a one-year survival rate of 32% (13 patients). We focused on mCRC patients as they represented the most relevant and homogeneous population in the trial. We performed Kaplan-Meier curves, log-rank tests and regression curves to correlate immunobiological findings and patients’ outcome. We found that their OS correlated with lower (under the median) ECOG scores (p:0.039), CEA levels (p:0.021), and serum levels of inflammatory markers (NLR, CRP, ESR, and LDH/LDHNR and ENA; p inferior 0.04) at baseline. Patients’ OS also correlated with greater (over the median) baseline levels of IL4 (p:0.028) and 17 (P:0.049), and with a post-treatment increase in anti-neutrophil-cytoplasm-antibodies/anti-proteinase-3 (Fold change to baseline values grater than 1; p:0.039). Activating K-ras mutations did not correlate with survival, however, inflammatory markers, cytokines, and autoantibodies lost their correlation with the survival in patients bearing these mutations. These results suggest that TSPP-antitumor activity in mCRC patients is affected by their baseline inflammatory/immunological status at baseline. TSPPVAC1 Phase Ib program; patients’ distributionARM A1. ADJ + TSPP 100 μg (n = 3)2. ADJ + TSPP 200 μg (n = 3)3. ADJ + TSPP 300 μg (n = 6)ARM B1. ADJ + TSPP 100 μg + IG-1 (n = 3)2. ADJ + TSPP 200 μg + IG-1 (n = 3)3. ADJ + TSPP 300 μg + IG-1 (n = 3)ARM C (DL1-3)1. GOLFIG + ADJ+TSPP 100 μg + IG-1 (n = 3)2. GOLFIG + ADJ+TSPP 200 μg + IG-1 (n = 3)3. GOLFIG + ADJ+TSPP 300 μg + IG-1 (n = 11)ARM C(DL0) 1. GOLFIG (12 courses) -> ADJ + TSPP 300 μg + IG-1 (n = 10)Figure legend: ADJ = montanide; n = number of patients; IG1 = sc. GM-CSF and sc. Aldesleukine; GOLFIG = gemcitabine + FOLFOX4 polychemotherapy + IG1 regimen Citation Format: Pierpaolo Correale, Cirino Botta, Elodia Claudia Martino, Valerio Nardone, Cristina Ulivieri, Claudia Gandolfo, Tatiana Cosima Baldari, Stefano Lazzi, Alessandro Ginori, Antonella Fioravanti, Giacomo Maria Guidelli, Luigi Pirtoli, Antonio Giordano, Pierfrancesco Tassone, Pierosandro Tagliaferri, Maria Grazia Cusi. Immune-inflammatory markers predict the outcome of metastatic colorectal cancer patients treated with the thymidylate synthase poly-epitope peptide (TSPP) vaccine: results from a multi-arm TSPP/VAC phase Ib program. [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 2232.

Herbacetin Is a Novel Allosteric Inhibitor of Ornithine Decarboxylase with Antitumor Activity.

Ornithine decarboxylase (ODC) is a rate-limiting enzyme in the first step of polyamine biosynthesis that is associated with cell growth and tumor formation. Existing catalytic inhibitors of ODC have lacked efficacy in clinical testing or displayed unacceptable toxicity. In this study, we report the identification of an effective and nontoxic allosteric inhibitor of ODC. Using computer docking simulation and an in vitro ODC enzyme assay, we identified herbacetin, a natural compound found in flax and other plants, as a novel ODC inhibitor. Mechanistic investigations defined aspartate 44 in ODC as critical for binding. Herbacetin exhibited potent anticancer activity in colon cancer cell lines expressing high levels of ODC. Intraperitoneal or oral administration of herbacetin effectively suppressed HCT116 xenograft tumor growth and also reduced the number and size of polyps in a mouse model of APC-driven colon cancer (ApcMin/+). Unlike the well-established ODC inhibitor DFMO, herbacetin treatment was not associated with hearing loss. Taken together, our findings defined the natural product herbacetin as an allosteric inhibitor of ODC with chemopreventive and antitumor activity in preclinical models of colon cancer, prompting its further investigation in clinical trials.

Abstract P5-03-01: Therapeutic targeting of Rac GTPases in ER+ and HER2+ breast cancer

Abstract As crucial regulators of cell motility, survival, and proliferation, Rac GTPases (Rac1/2/3) have been implicated in cancer. We previously found that P-REX1, a guanine nucleotide exchange factor that activates Rac GTPases, forms a PI3K-driven positive feedback loop to promote activation of Rac enzymes, receptor tyrosine kinases, PI3K/AKT/mTOR, and MEK/ERK in ER+ breast cancer cells. Importantly, inhibition of Rac GTPases with a small molecule (EHT1864) simultaneously suppressed activation of both the PI3K/AKT/mTOR and MEK/ERK pathways. While co-targeting of the PI3K/AKT/mTOR and MEK/ERK pathways with drug combinations has anti-tumor activity in preclinical models and is being tested in ongoing clinical trials, targeting Rac as a common upstream signaling node may be a more efficient means of simultaneously targeting these two oncogenic pathways. In breast cancer cell lines, treatment with EHT1864 decreased activation of AKT, mTOR, p70S6K, and S6 in a dose-dependent manner. Pulldown of activated Rac from cell lysates revealed that GTP-bound Rac1 and/or Rac3 bind MEK1/2, ERK1/2, p70S6K, S6, Raptor, Rictor, and mTOR. Temporal analysis indicated that EHT1864 inhibits phosphorylation of p70S6K (an mTORC1 substrate) before AKT is inhibited, suggesting that Rac may directly activate p70S6K and/or mTORC1. Mining of sensitivity data from ∼700 cell lines to a panel of 138 drugs (COSMIC/GDSC database) revealed that the growth-suppressive effects of EHT1864 correlate most strongly with growth-suppressive patterns induced by a p70S6K inhibitor, supporting the notion that Rac directly activates p70S6K. Additionally, EHT1864 treatment dose-dependently decreased phosphorylation of ERK1/2 and MEK1/2, and induced apoptosis in breast cancer cell lines. In a panel of 16 breast cancer lines, cells with activating mutations in PIK3CA (encodes the p110-alpha subunit of PI3K) exhibit increased EHT1864 sensitivity. Pharmacokinetic analysis of EHT1864 (100 mg/kg, i.p.) in plasma in NSG mice revealed that drug was present at >50 uM for 1 h after administration. In mice bearing s.c. ER+/HER2+ BT-474 breast cancer xenografts, EHT1864 (100 mg/kg BID) significantly slowed tumor growth compared to vehicle control. Thus, therapeutically targeting Rac could be an effective means of reducing cancer cell proliferation and survival by simultaneously suppressing both the PI3K/AKT/mTOR and MEK/ERK signaling pathways in ER+ and HER2+ breast cancers. Citation Format: Hampsch RA, Shee K, Miller TW. Therapeutic targeting of Rac GTPases in ER+ and HER2+ breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-03-01.

Preclinical evaluation of WYE-687, a mTOR kinase inhibitor, as a potential anti-acute myeloid leukemia agent

Mammalian target of rapamycin (mTOR) as a potential drug target for treatment of acute myeloid leukemia (AML). Here, we investigated the potential anti-leukemic activity by WYE-687, a potent mTOR kinase inhibitor. We demonstrated that WYE-687 potently inhibited survival and proliferation of established (HL-60, U937, AML-193 and THP-1 lines) and human AML progenitor cells. Yet, same WYE-687 treatment was non-cytotoxic to the primary peripheral blood mononuclear leukocytes (PBMCs) isolated from healthy donors. WYE-687 induced caspase-dependent apoptotic death in above AML cells/progenitor cells. On the other hand, the pan-caspase inhibitor (Z-VAD-FMK), the caspase-3 specific inhibitor (Z-DEVD-FMK) or the caspase-9 specific inhibitor (z-LEHD-fmk) attenuated WYE-687-induced cytotoxicity. At the molecular level, WYE-687 concurrently inhibited activation of mTORC1 (p70S6K1 and S6 phosphorylations) and mTORC2 (AKT Ser-473 and FoxO1/3a phosphorylations), whiling downregulating mTORC1/2-regulated genes (Bcl-xL and hypoxia-inducible factor 1/2α) in both HL-60/U937 cells and human AML progenitor cells. In vivo, oral administration of WYE-687 potently inhibited U937 leukemic xenograft tumor growth in severe combined immunodeficient (SCID) mice, without causing significant toxicities. In summary, our results demonstrate that targeting mTORC1/2 by WYE-687 leads to potent antitumor activity in preclinical models of AML.

CD19xCD3 DART protein mediates human B-cell depletion in vivo in humanized BLT mice

Novel therapeutic strategies are needed for the treatment of hematologic malignancies; and bispecific antibody-derived molecules, such as dual-affinity re-targeting (DART) proteins, are being developed to redirect T cells to kill target cells expressing tumor or viral antigens. Here we present our findings of specific and systemic human B-cell depletion by a CD19xCD3 DART protein in humanized BLT mice. Administration of the CD19xCD3 DART protein resulted in a dramatic sustained depletion of human CD19+ B cells from the peripheral blood, as well as a dramatic systemic reduction of human CD19+ B-cell levels in all tissues (bone marrow, spleen, liver, lung) analyzed. When human CD8+ T cells were depleted from the mice, no significant B-cell depletion was observed in response to CD19xCD3 DART protein treatment, confirming that human CD8+ T cells are the primary effector cells in this in vivo model. These studies validate the use of BLT humanized mice for the in vivo evaluation and preclinical development of bispecific molecules that redirect human T cells to selectively deplete target cells.

Antroquinonol A: Scalable Synthesis and Preclinical Biology of a Phase 2 Drug Candidate.

The fungal-derived Taiwanese natural product antroquinonol A has attracted both academic and commercial interest due to its reported exciting biological properties. This reduced quinone is currently in phase II trials (USA and Taiwan) for the treatment of non-small-cell lung carcinoma (NSCLC) and was recently granted orphan drug status by the FDA for the treatment of pancreatic cancer and acute myeloid leukemia. Pending successful completion of human clinical trials, antroquinonol is expected to be commercialized under the trade name Hocena. A synthesis-enabled biological re-examination of this promising natural product, however, reveals minimal in vitro and in vivo antitumor activity in preclinical models.

Preclinical Efficacy and Safety Assessment of an Antibody-Drug Conjugate Targeting the c-RET Proto-Oncogene for Breast Carcinoma.

The RET proto-oncogene has been implicated in breast cancer, and the studies herein describe the preclinical and safety assessment of an anti-RET antibody-drug conjugate (ADC) being developed for the treatment of breast cancer. RET protein expression was analyzed in breast tumor samples using tissue microarrays. The fully human anti-RET antibody (Y078) was conjugated to the DM1 and DM4 derivatives of the potent cytotoxic agent maytansine using thioether and disulfide linkers, respectively. The resulting compounds, designated Y078-DM1 and Y078-DM4, were evaluated for antitumor activity using human breast cancer cell lines and established tumor xenograft models. A single-dose, 28-day, safety study of Y078-DM1 was performed in cynomolgus monkeys. By immunohistochemistry, RET expression was detected in 57% of tumors (1,596 of 2,800 tumor sections) and was most common in HER2-positive and basal breast cancer subtypes. Potent in vitro cytotoxicity was achieved in human breast cancer cell lines that have expression levels comparable with those observed in breast cancer tissue samples. Dose-response studies in xenograft models demonstrated antitumor activity with both weekly and every-3-weeks dosing regimens. In cynomolgus monkeys, a single injection of Y078-DM1 demonstrated dose-dependent, reversible drug-mediated alterations in blood chemistry with evidence of on-target neuropathy. RET is broadly expressed in breast cancer specimens and thus represents a potential therapeutic target; Y078-DM1 and Y078-DM4 demonstrated antitumor activity in preclinical models. Optimization of the dosing schedule or an alternate cytotoxic agent with a different mechanism of action may reduce the potential risk of neuropathy. Clin Cancer Res; 21(24); 5552-62. ©2015 AACR.

Significant blockade of multiple receptor tyrosine kinases by MGCD516 (Sitravatinib), a novel small molecule inhibitor, shows potent anti-tumor activity in preclinical models of sarcoma

Sarcomas are rare but highly aggressive mesenchymal tumors with a median survival of 10–18 months for metastatic disease. Mutation and/or overexpression of many receptor tyrosine kinases (RTKs) including c-Met, PDGFR, c-Kit and IGF1-R drive defective signaling pathways in sarcomas. MGCD516 (Sitravatinib) is a novel small molecule inhibitor targeting multiple RTKs involved in driving sarcoma cell growth. In the present study, we evaluated the efficacy of MGCD516 both in vitro and in mouse xenograft models in vivo. MGCD516 treatment resulted in significant blockade of phosphorylation of potential driver RTKs and induced potent anti-proliferative effects in vitro. Furthermore, MGCD516 treatment of tumor xenografts in vivo resulted in significant suppression of tumor growth. Efficacy of MGCD516 was superior to imatinib and crizotinib, two other well-studied multi-kinase inhibitors with overlapping target specificities, both in vitro and in vivo. This is the first report describing MGCD516 as a potent multi-kinase inhibitor in different models of sarcoma, superior to imatinib and crizotinib. Results from this study showing blockade of multiple driver signaling pathways provides a rationale for further clinical development of MGCD516 for the treatment of patients with soft-tissue sarcoma.

Clinical Evaluation of Combined Epigenetic Therapies on the Induction of Fetal Hemoglobin in Patients with Hematologic Malignancies

Fetal hemoglobin induction with hydroxyurea (HU) is a mainstay of therapy for β-hemoglobinopathies, especially sickle cell disease (SCD). A high level of fetal hemoglobin (HbF) has a direct relationship with acute clinical status in SCD patients including pain crises, acute chest syndrome, and death. However, not all patients benefit from HU, and more effective HbF induction strategies are needed. DNA methyl transferase (DNMT) inhibitors and histone deacetylase (HDAC) inhibitors have been shown in vitro to induce HbF production through epigenetic modification of the β-globin gene cluster. Azacitidine (AZA) is a DNMT already used in some SCD patients resistant to HbF modulation with HU. Entinostat (MS-275) is an orally available histone deacetylase inhibitor with a long half-life and established antitumor activity in preclinical models. Recent studies suggest that drugs, which act with different molecular and epigenetic mechanisms, have synergistic effects on induction of fetal hemoglobin (Fard et al. IJHOSCR 2013). In this study, we evaluated the effects of a combination of AZA and MS-275 on HbF levels. This was preformed as a correlative study of a phase I clinical trial (J0443 trial) of these drugs in patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). We sequentially measured the level of HbF the peripheral blood in 33 patients receiving different doses of AZA (range: 30mg/m2 to 50mg/m2 per day for 10 doses) and MS-275 (range: 2 to 8 mg/m2 orally on days 3 and 10). Patients completed a minimum of four 28-day cycles of combined therapy. HbF levels were measured in peripheral blood at baseline, at day 15 or 16 and day 29 or 30 of cycle 1, and after cycles 2, 4, and if applicable 6. Azacitidine dose positively correlated with HbF fold increase (mean of 1.1, 2.3, and 2.1 for doses of 30, 40, and 50 mg respectively, p=0.07) while MS-275 dose had a slightly negative correlation with HbF level (mean of 3.0, 1.8, and 1.3 for doses of 2, 4, and 6mg respectively, p=0.13). There was no correlation between baseline HbF and HbF fold increase after exposure to treatment (p=NS) and no correlation between baseline HbF levels and clinical disease response (p=0.19). Interestingly, we demonstrated a correlation between HbF fold increase and clinical disease response: median fold increase of 3.5 for patients achieving hematologic normalization (complete response, partial response, or trilineage hematological improvement) versus 1.4 in non-responders (p=0.006). The positive correlation between AZA dose and HbF increase is consistent with prior work showing that this drug induces HbF production. The correlation between clinical response and HbF induction could reflect a greater susceptibility to AZA potentially related to differing methylomes. Alternatively, it may also represent a known increase in HbF in the setting of stress erythropoiesis. The slight inverse correlation between MS-275 and HbF level was surprising, as other HDAC inhibitors are known to induce HbF in vitro. However, these results are in line with the methylation data found in the more recent randomized phase 2 trial of AZA +/- MS-275 (E1905 trial) that showed a potential pharmacodynamic antagonism of the combination (Prebet et al. J Clin Oncol. 2014). Overall, this work supports the use of AZA as a clinical inducer of HbF. It also shows the importance of trialing various combinations of HbF inducers, as not all drugs work synergistically and some may even be antagonistic in combination. Disclosures Off Label Use: Azacitidine (AZA) is a DNA methyl transferase (DNMT) inhibitor. Entinostat (MS-275) is an orally available histone deacetylase inhibitor. Both drugs were used in a phase I clinical trial (J0443 trial) of these drugs in patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). . Keefer:MAST therapeutics: Employment. Gore:Celgene: Consultancy, Honoraria, Research Funding. Prebet:CELGENE: Research Funding.

Abstract C119: Investigation of the anti-angiogenic effects of abituzumab in patients with colorectal or ovarian cancer and liver metastases using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)

Abstract Background: Integrins promote cell survival, metastasis, and angiogenesis, with integrins ανβ3 and ανβ5 promoting neovascularization. Abituzumab (EMD 525797) is a humanized monoclonal IgG2 antibody that specifically binds to the αν integrin subunit to inhibit αν integrin-mediated functions. It has shown antitumor activity in preclinical models and clinical trials. We investigated the tolerability and potential anti-angiogenic activity of abituzumab using DCE-MRI. Methods: This phase I study recruited patients (pts) ≥18 years with liver metastases (3-10 cm in diameter) of either colorectal (CRC) or ovarian cancer (OC) who had failed standard therapy. Pts received abituzumab 250, 500, 1,000, or 1,500 mg IV q2w, with ≥6 pts per dose. The decision to escalate the dose was based on the occurrence of dose-limiting toxicity (DLT). DCE-MRI scans were performed 24 and 96 hours after the first abituzumab dose, 1 week after first dose, and immediately prior to the second dose to identify changes in parameters including Ktrans, extracellular/extravascular volume, and blood plasma volume during one cycle of therapy. DCE-MRI scan data were analyzed centrally. Tumor response was evaluated every 6 weeks. Primary objectives were to assess the tolerability of abituzumab and to investigate vascular and volumetric responses to abituzumab using DCE-MRI. Secondary objectives included characterization of the pharmacokinetics of abituzumab and its effect on exploratory pharmacodynamic markers, including tumor markers. Results: 41 pts were enrolled (CRC, n = 30; OC, n = 11). All pts had received ≥1 prior anticancer treatment. Four of 31 pts included in the dose-escalation analysis set had DLTs: myocardial ischemia (250 mg, n = 1/6), intracranial hemorrhage (500 mg, n = 1/12), and drug hypersensitivity (1,500 mg, n = 2/7). With the exception of drug hypersensitivity, the nature and incidence of adverse events (AEs) were similar between the dose levels. The most frequently reported treatment-related AEs were fatigue (12.2%) and headache (12.2%). Of 32 patients with available response information, 3 with OC had a best overall response of stable disease (SD) lasting ≥6 weeks (2 treated with abituzumab 500 mg, 1 with abituzumab 1,000 mg); one 73-year-old pt with high-grade serous OC who received abituzumab as 5th-line therapy had SD for 33 weeks and a CA-125 response. No complete or partial responses were observed. No trends in differences in mean DCE-MRI parameters between abituzumab doses and no vascular or volumetric responses to abituzumab were observed, although alterations in DCE-MRI parameters were noted in individual patients. Small changes in IAUC60, Ktrans, and blood plasma volume were observed between Week 1 Day 5 and Week 2 Day 1 that may have been due to abituzumab-induced effects, but did not correlate with clinical activity (SD). Conclusions: This phase I trial has confirmed the tolerability of abituzumab, although hypersensitivity reactions represent a new event that warrants further investigation. The occurrence of SD in pts with OC with large liver metastases suggests that abituzumab has activity. However, there was little evidence of a clear effect of abituzumab on tumor vasculature, suggesting limited dependence on neovascularization in advanced tumors. Citation Format: Josep Tabernero, Geoffrey Parker, Andrew Clamp, Elena Elez, Nerissa Mescallado, Rodrigo Dienstmann, Tamara Sauri, Jurjees Hasan, Jose J. Mateos, Rolf Bruns, Claude Gimmi, Gordon C. Jayson. Investigation of the anti-angiogenic effects of abituzumab in patients with colorectal or ovarian cancer and liver metastases using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). [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 C119.

Abstract C137: First-in-human dose escalation study of oral ONC201 in advanced solid tumors

Abstract Background: ONC201 is an orally active first-in-class small molecule with strong antitumor activity in preclinical models of advanced cancers. In cancer cell lines and patient samples ONC201 induces activation of the integrated stress response (Ishizawa et al ASH, 2014) resulting in upregulation of ATF4 and CHOP which in turn regulates several proapoptotic genes namely DR5. ONC201 also causes late-stage inactivation of Akt and ERK, which also results in downstream activation of the apoptotic TRAIL pathway as part of innate immune surveillance (Allen J et al, Sci Trans Med, 2013). Activity of ONC201 is independent of p53 status and mutation agnostic. ONC201 is well tolerated at efficacious doses in animal models, crosses the blood brain barrier, is particularly effective in refractory tumors, depletes cancer stem cells (Ishizawa et al, ASH 2014; Prabhu et al, Blood 2014; Zhao et al, ASCO 2014), and is effective with infrequent dosing preclinically. Based on the compelling efficacy and safety profile of ONC201 as well as the engagement of signaling pathways critical for many cancers, the clinical introduction ONC201 in advanced cancer patients is warranted. Methods: The first-in-human study of ONC201 (NCT02250781) began in January 2015 as an open-label single-site phase I trial enrolling adult patients with refractory advanced solid tumors and glioblastoma (GBM). Patients with symptomatic brain metastases or prior bevacizumab for treatment of GBM are excluded. The primary endpoint is determination of the recommended phase II dose (RP2D) of single agent ONC201 given orally once every 3 weeks (1 cycle). Secondary endpoints include assessment of pharmacodynamics using select biomarkers for ONC201 (Allen et al, 2015), pharmacokinetics, toxicity, and efficacy. The study employs an accelerated, single patient per cohort, dose escalation design with expansion to a standard 3+3 design if a subject has grade > / = grade 2 toxicity or dose limiting toxicity within cycle 1. The maximum tolerated dose is the highest dose level in which 6 patients have been treated with < / = 1 instance of DLT. Based on pre-clinical models doses for once every 3 week dosing were: dose leve1 (DL) 1- 125mg; 2- 250mg; 3- 375mg; 4- 500mg; 5- 626mg. Results: Single patient dose escalation was completed in cohorts 1 to 4 and 6 patients completed at least 3 weeks of level 5 without any > / = grade 2 drug related toxicity. At DL 6, Mean T1/2 = 7.91hours (7.01-9.42); Mean Cmax = 8.58 ug/mL (3.95 - 19.15) Mean AUC(0-24) = 28057 (15293 - 50597) hr-ng/mL. Ongoing radiographic stable disease is noted in a patient with metastatic castrate resistant prostate cancer. Conclusions: The RP2D of ONC201 is 625mg on a once every 3 week schedule. Evaluation of PD markers of response and enrollment to a dose expansion safety cohort are ongoing. Citation Format: Mark N. Stein, Rebecca Moss, Tina Mayer, Ann W. Silk, Nancy Chan, Ling Zheng, Yasmeen Beckett, Noelle Tenpenny, Edward Bentlyewski, Robert DiPaola, Rohinton Tarapore, Joshua Allen, Janice Mehnert. First-in-human dose escalation study of oral ONC201 in advanced solid tumors. [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 C137.

Phase I study of alpha-tocopherlyoxyacetic acid in patients with advanced cancer

Meeting abstracts Alpha-tocopheryloxyacetic acid (α-TEA) is a pro-apoptotic agent that demonstrates in vivo anti-tumor activity in pre-clinical models in a T cell-dependent fashion. In IND-enabling studies, orally administered α-TEA lysine salt demonstrated a safety profile in mice and dogs

Dual mTORC1/2 inhibition by INK-128 results in antitumor activity in preclinical models of osteosarcoma

Existing evidence has shown that mammalian target of rapamycin (mTOR) overactivation is an important contributor of osteosarcoma (OS) progression. Here, we studied the potential anti-OS activity of a potent mTOR kinase inhibitor: INK-128 (MLN0128). We demonstrated that INK-128 induced potent cytotoxic effects against several human OS cell lines (U2OS, MG-63 and SaOs-2), yet same INK-128 treatment was safe (non-cytotoxic) to OB-6 human osteoblastic cells and MLO-Y4 human osteocytic cells. INK-128 induced caspase-dependent apoptosis in OS cells, but not in MLO-Y4/OB-6 cells. The caspase-3 specific inhibitor (z-DVED-fmk) or the pan caspase inhibitor (z-VAD-fmk) dramatically attenuated INK-128-exerted cytotoxicity against OS cells. Molecularly, INK-128 inhibited activation of mTORC1 (S6K1 and S6 phosphorylations) and mTORC2 (AKT Ser-473 phosphorylation), without affecting AKT Thr-308 phosphorylation in U2OS cells. Significantly, AKT inhibition by MK-2206 (an AKT inhibitor), or AKT1/2 stable knockdown by targeted-shRNA, remarkably sensitized INK-128-induced activity in OS cells. In vivo, oral administration of INK-128 potently inhibited U2OS xenograft growth in severe combined immuno-deficient (SCID) mice. mTORC1/2 activation in xenograft tumors was also suppressed with INK-128 administration. In summary, we show that INK-128 exerts potent anti-OS activity in vitro and in vivo. INK-128 might be further investigated as a novel anti-OS agent.

Abstract A56: Intratumoral injection of IMO-2055, a novel Toll-like receptor 9 agonist, with ipilimumab induces a systemic tumor-specific immune response

Abstract Through multiple pathways, tumors suppress immune activity during all phases of growth and dissemination, and enhancement of antitumor immunity is a major goal of cancer treatment. Attractive immunotherapy targets include Toll-like receptors, which activate the innate immune system and play an important role in adaptive immune responses, and immune-checkpoint pathways, such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), which regulate T cell activity. Agents directed against these targets alone or in combination have the potential to break immune tolerance and enhance antitumor immune responses. IMO-2055 is a potent and selective TLR 9 agonist designed to stimulate an immune response, and in previous studies it demonstrated synergistic or additive effects when combined with tyrosine-kinase inhibitors and monoclonal antibodies (mAb). In multiple clinical studies, IMO-2055 has been generally well tolerated in more than 300 healthy volunteers and patients with renal, lung, colon, or head and neck cancer. In the present studies, we studied IMO-2055 alone and in combination with ipilimumab, an approved mAb against CTLA-4, in a CT26 colon carcinoma model to evaluate antitumor immune activity and effects on treated and distant tumors. In the first study, BALB/c mice were s.c. implanted with 106 CT26 and CT26.CL25 cells, a subclone of CT26 expressing a model antigen β-galactosidase (β-gal), on right and left flanks, respectively. Treatment was initiated when tumor nodules reached 200 mm3. Treated mice received 2.5 mg/kg IMO-2055 by intratumoral injections only in CT26 implanted right tumor twice per week for total 5 times. A similar experiment with IMO-2055 was conducted in the MB-49 bladder cancer mouse model. In the second study, BALB/c mice were s.c. implanted with 7.5 x 105 CT26 on right flank and the same mice were i.v. implanted with 4 x 105 CT26.CL25 to generate lung metastases. Coinjections of 2.5 mg/kg IMO-2055 and 0.5 mg/kg ipilimumab into CT26 solid tumors on the right flank were initiated on day 8 when tumor nodules reached 200 to 300 mm3. IMO-2055 was given on days 8, 11, 13 and 15 while ipilimumab was administered on days 8 and 13. IMO-2055 monotherapy resulted in tumor growth inhibition in both treated and distant tumors. Distant tumors grew when treatment stopped, indicating the possible role of immune tolerance. Similar results were observed in the MB-49 bladder cancer model. In situ IMO-2055 injections elicited statistically significant differences in tumor-specific cytotoxic T cells against CT26 associated antigen AH1 (p<0.0001) and β-gal presented only in remote CT26.CL25 tumors (p=0.0003) versus PBS control. IMO-2055 and ipilimumab combination therapy resulted in improved tumor growth inhibition versus IMO-2055 or ipilimumab alone. The cytotoxic T cells against β-gal presented in the systemic lung metastasis sites were dramatically increased (p<0.01) compared to either monotherapy alone. The antitumor immune response generated by the combination of IMO-2055 and ipilimumab eradicated disseminated lung metastases in 6 of 8 tumor-bearing mice. In conclusion, IMO-2055 monotherapy and IMO-2055 and ipilimumab combination therapy showed potent antitumor activity in preclinical models. In addition, combination therapy overcame immune tolerance and demonstrated improved antitumor activity versus monotherapy with either agent, supporting further evaluation of combination regimens with IMO-2055 and CTLA-4 mAbs or possibly other checkpoint inhibitors. Citation Format: Daqing Wang, Dong Yu, Sudhir Agrawal. Intratumoral injection of IMO-2055, a novel Toll-like receptor 9 agonist, with ipilimumab induces a systemic tumor-specific immune response. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A56.

Gene Expression Ratios Lead to Accurate and Translatable Predictors of DR5 Agonism across Multiple Tumor Lineages.

Death Receptor 5 (DR5) agonists demonstrate anti-tumor activity in preclinical models but have yet to demonstrate robust clinical responses. A key limitation may be the lack of patient selection strategies to identify those most likely to respond to treatment. To overcome this limitation, we screened a DR5 agonist Nanobody across >600 cell lines representing 21 tumor lineages and assessed molecular features associated with response. High expression of DR5 and Casp8 were significantly associated with sensitivity, but their expression thresholds were difficult to translate due to low dynamic ranges. To address the translational challenge of establishing thresholds of gene expression, we developed a classifier based on ratios of genes that predicted response across lineages. The ratio classifier outperformed the DR5+Casp8 classifier, as well as standard approaches for feature selection and classification using genes, instead of ratios. This classifier was independently validated using 11 primary patient-derived pancreatic xenograft models showing perfect predictions as well as a striking linearity between prediction probability and anti-tumor response. A network analysis of the genes in the ratio classifier captured important biological relationships mediating drug response, specifically identifying key positive and negative regulators of DR5 mediated apoptosis, including DR5, CASP8, BID, cFLIP, XIAP and PEA15. Importantly, the ratio classifier shows translatability across gene expression platforms (from Affymetrix microarrays to RNA-seq) and across model systems (in vitro to in vivo). Our approach of using gene expression ratios presents a robust and novel method for constructing translatable biomarkers of compound response, which can also probe the underlying biology of treatment response.

Cyclophosphamide-Mediated Tumor Priming for Enhanced Delivery and Antitumor Activity of HER2-Targeted Liposomal Doxorubicin (MM-302).

Given the bulky nature of nanotherapeutics relative to small molecules, it is hypothesized that effective tumor delivery and penetration are critical barriers to their clinical activity. HER2-targeted PEGylated liposomal doxorubicin (MM-302, HER2-tPLD) is an antibody-liposomal drug conjugate designed to deliver doxorubicin to HER2-overexpressing cancer cells while limiting uptake into nontarget cells. In this work, we demonstrate that the administration and appropriate dose sequencing of cyclophosphamide can improve subsequent MM-302 delivery and enhance antitumor activity in preclinical models without negatively affecting nontarget tissues, such as the heart and skin. We demonstrate that this effect is critically dependent on the timing of cyclophosphamide administration. Furthermore, the effect was found to be unique to cyclophosphamide and related analogues, and not shared by other agents, such as taxanes or eribulin, under the conditions examined. Analysis of the cyclophosphamide-treated tumors suggests that the mechanism for improved MM-302 delivery involves the induction of tumor cell apoptosis, reduction of overall tumor cell density, substantial lowering of interstitial fluid pressure, and increasing vascular perfusion. The novel dosing strategy for cyclophosphamide described herein is readily translatable to standard clinical regimens, represents a potentially significant advance in addressing the drug delivery challenge, and may have broad applicability for nanomedicines. This work formed the basis for clinical evaluation of cyclophosphamide for improving liposome deposition as part of an ongoing phase I clinical trial of MM-302 in HER2-positive metastatic breast cancer.

Characterization of the human T cell response to in vitro CD27 costimulation with varlilumab.

BackgroundClinical targeting of TNFR family of receptors (CD40, CD134 and CD137) with immunostimulatory monoclonal antibodies has been successful in cancer immunotherapy. However, targeting of CD27 with a mAb is a relatively new approach to provide costimulation of immune cells undergoing activation. Thus, activation of human CD27 (TNFRSF7) with a monoclonal antibody (varlilumab) has previously been demonstrated to result in T cell activation and anti-tumor activity in preclinical models, and is currently in early phase clinical trials in patients with advanced malignancies. In this study we used an in vitro system using human peripheral blood T cells to characterize the varlilumab-mediated costimulatory effects in combination with TCR stimulation in terms of phenotypic, transcriptional and functionality changes.MethodsT cells were isolated from normal volunteer PBMCs using magnetic bead isolation kits and stimulated in vitro with plate bound anti-CD3 Ab (OKT3) and varlilumab or control Ab for 72 h. Activation profiles were monitored by ELISA or Luminex-based testing cytokine/chemokine releases, cell surface phenotyping for costimulatory and coinhibitory markers and CFSE dye dilution by proliferating T cells and Tregs. Changes in gene expression and transcriptome analysis of varlilumab-stimulated T cells was carried on Agilent Human whole genome microarray datasets using a suite of statistical and bioinformatic software tools.ResultsCostimulation of T cells with varlilumab required continuous TCR signaling as pre-activated T cells were unable to produce cytokines with CD27 signaling alone. Analysis of T cell subsets further revealed that memory CD4+ and CD8+ T cells were specifically activated with a bias toward CD8+ T lymphocyte proliferation. Activation was accompanied by upregulated cell surface expression of costimulatory [4-1BB, OX40, GITR and ICOS] and coinhibitory [PD-1] molecules. Importantly, varlilumab costimulation did not activate purified Tregs as measured by cytokine production, proliferation and suppression of dividing non-Treg T cells. Analysis of changes in gene expression during varlilumab stimulation of T cells revealed modulation of pro-inflammatory signatures consistent with cellular activation and proliferation, with the IL-2 pathway showing the highest frequency of gene modulation.ConclusionsAltogether, the data reveal the requirements and T cell subtype-specific effects of CD27 costimulation, and helps select relevant biomarkers for studying the effects of varlilumab in patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s40425-015-0080-2) contains supplementary material, which is available to authorized users.

Inhibitory Effect of the Noncamptothecin Topoisomerase I Inhibitor LMP-400 on Female Mice Models and Human Pheochromocytoma Cells.

Metastatic pheochromocytoma continues to be an incurable disease, and treatment with conventional cytotoxic chemotherapy offers limited efficacy. In the present study, we evaluated a novel topoisomerase I inhibitor, LMP-400, as a potential treatment for this devastating disease. We found a high expression of topoisomerase I in human metastatic pheochromocytoma, providing a basis for the evaluation of a topoisomerase 1 inhibitor as a therapeutic strategy. LMP-400 inhibited the cell growth of established mouse pheochromocytoma cell lines and primary human tumor tissue cultures. In a study performed in athymic female mice, LMP-400 demonstrated a significant inhibitory effect on tumor growth with two drug administration regimens. Furthermore, low doses of LMP-400 decreased the protein levels of hypoxia-inducible factor 1 (HIF-1α), one of a family of factors studied as potential metastatic drivers in these tumors. The HIF-1α decrease resulted in changes in the mRNA levels of HIF-1 transcriptional targets. In vitro, LMP-400 showed an increase in the growth-inhibitory effects in combination with other chemotherapeutic drugs that are currently used for the treatment of pheochromocytoma. We conclude that LMP-400 has promising antitumor activity in preclinical models of metastatic pheochromocytoma and its use should be considered in future clinical trials.

Abstract CT139: Phase I study of GDC-0425, a checkpoint kinase 1 inhibitor, in combination with gemcitabine in patients with refractory solid tumors

Abstract Background: Checkpoint kinase 1 (Chk1) acts at S and G2/M checkpoints to allow time for high-fidelity DNA replication and repair before cell cycle progression. Chk1 inhibition converts a transient genotoxic insult from chemotherapy into a cytotoxic event by overriding cell cycle arrest, allowing cells mitosis with DNA damage. GDC-0425 is an oral, selective Chk1 inhibitor. GDC-0425 enhances gemcitabine (gem) efficacy in tumor xenograft models. Greater chemopotentiation is observed in cancer cell lines lacking p53 activity. Methods: A phase I dose-escalation trial (3+3+3 design) included patients (pts) with refractory solid tumors and ECOG performance status (PS) ≤ 1. Pts received a single dose of GDC-0425 on day -7 for PK evaluation followed by 21-day cycles of gem on Days 1 and 8 and GDC-0425 on Days 2 and 9 at gem (mg/m2) + GDC-0425 (mg) dose levels of 750 + 60, 1000 + 60, and 1000 + 80. p53 was evaluated in archival tumor tissue by gene sequencing, immunohistochemistry, and gene expression signature. Safety, pharmacokinetics (PK), pharmacodynamics, and tumor response were investigated. Results: Of 40 pts treated, 55% were female, median age was 56 years (range 33-82), and 68% had ECOG PS 0. Most common tumor types were breast (n = 10), non-small cell lung (n = 5), and cancer of unknown primary (CUP, n = 4). Maximum concentrations of GDC-0425 were achieved within 4 hours of dosing and its half-life was approximately 16 hours. Target exposures associated with checkpoint abrogation and anti-tumor activity in preclinical models were exceeded at 60 mg. No PK interaction was observed with GDC-0425 and gem. Dose escalation was halted at GDC-0425 80 mg with gem 1000 mg/m2 as 3 of 6 pts experienced Grade 4 thrombocytopenia as a dose-limiting toxicity (DLT); 1 pt also had Grade 3 neutropenia that delayed Cycle 2 (DLT). Blood counts recovered with treatment interruption and supportive care. The maximum tolerated dose of GDC-0425 was 60 mg with gem 1000 mg/m2. The most frequent adverse events (AEs) (all grades) related to GDC-0425 and/or gem were nausea (48%); anemia, neutropenia, vomiting (45% each); fatigue (43%); pyrexia (40%); and thrombocytopenia (35%). Serious AEs related to GDC-0425 and/or gem occurred in 8 pts: neutropenia and thrombocytopenia (n = 2 each); leukopenia, ALT/AST/GGT increased, pyrexia, rash, dyspnea, gastric ulcer, and gastroenteritis (n = 1 each). Median number of administered cycles was 3.5 (range 1-14). There were 3 partial responses in pts with triple-negative breast cancer (TNBC, TP53 mutated), melanoma, and CUP (n = 1 each). Conclusions: It is safe and feasible to administer GDC-0425 with a standard dose of gem. At the doses assessed, bone marrow suppression is common but manageable and exposures exceed those predicted by preclinical models to inhibit Chk1. Clinical activity was observed, including 1 patient with TP53 mutated TNBC. Citation Format: Jeffrey R. Infante, Antoine Hollebecque, Sophie Postel-Vinay, Todd Bauer, Beth Blackwood, Marie Evangelista, Sami Mahrus, Frank Peale, Xuyang Lu, Srikumar Sahasranaman, Rui Zhu, Yuan Chen, Xiao Ding, Elaine Murray, Jennifer Schutzman, Jennifer Lauchle, Jean-Charles Soria, Patricia LoRusso. Phase I study of GDC-0425, a checkpoint kinase 1 inhibitor, in combination with gemcitabine in patients with refractory solid tumors. [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 CT139. doi:10.1158/1538-7445.AM2015-CT139