Antitumor Activity In Tumor Models Research Articles

Abstract C027: Efficacy advantages of a novel pan-RAS inhibitor, ADT-1004, over mutant- specific KRAS inhibitors for suppressing pancreatic tumor growth in murine models

Abstract Background/Objective: Prognosis remains grim for localized or metastasized pancreatic ductal adenocarcinoma (PDAC) with 5-year survival rates of 3-16%. More than 90% of PDAC cases harbor KRAS mutations. KRASG12C inhibitors recently developed have limited use for PDAC because only 3% of cases express this mutation. We developed a novel pan-RAS inhibitor, ADT-1004 and evaluated antitumor activity in tumor models established from murine or human PDAC cell lines or patient-derived xenografts (PDX). ADT-1004 is an orally bioavailable prodrug of ADT-007, a highly potent and selective pan-RAS inhibitor (doi.org/10.1101/2023.05.17.541233). Methods: Murine PDAC cells harboring the KRASG12D mutation (KPC-Luc or 2838C3-Luc) were orthotopically implanted into the pancreas of C57BL/6J mice. Four PDX PDAC tumors harboring KRAS mutations were implanted orthotopically in NSG mice. To assess potential to overcome RAS inhibitor resistance, parental KRASG12C MIA PaCa-2 PDAC cells and a resistant derivative of MIA PaCa-2 cells were implanted subcutaneously. To assess selectivity, mice were implanted with RASWT BxPC-3 cells SC. Mice were treated orally with ADT-1004 (40mg/kg) 5x/week for 4 weeks. Sotorasib and adagrasib KRASG12C inhibitors were administered at the same dose, route, and schedule as ADT-1004. Results: ADT-007 potently and selectively inhibited the growth of human and mouse PDAC cell lines in vitro. For example, the IC50 value of ADT-007 for KRASG12C MIA PaCa-2 PDAC cells was 2 nM compared to 2500 nM for RASWT BxPC-3 PDAC cells. Growth inhibition by ADT-007 was dependent on activated RAS and associated with reduced GTP-RAS levels and MAPK/AKT signaling. ADT-1004 was well tolerated in mice at doses up to 175 mg/kg bid orally with sustained plasma levels of ADT-007 exceeding growth IC50 values. ADT-1004 displayed robust antitumor activity in mouse tumor models using human- or mouse-derived PDAC cell lines with G12D, G12V, G12C, or G13Q KRAS mutations, causing selective inhibitory effects on ERK phosphorylation in tumors but not in normal tissues. ADT-1004 also inhibited growth of KRASG12C mutant MIA PaCa-2 tumors to a comparable extent as sotorasib and adagrasib. Sotorasib and adagrasib were ineffective against xenografted tumors of resistant cells derived from MIA PaCa-2 cells, while ADT-1004 strongly inhibited tumor growth. Target selectivity of ADT-1004 was confirmed in vivo, as ADT-1004 did not affect the growth of RASWT BxPC-3 tumors. Conclusions: ADT-1004 inhibited tumor growth of KRAS mutant PDAC tumors by blocking activated RAS to disrupt downstream MAPK/AKT signaling. Side-by-side comparisons reveal antitumor efficacy advantages of ADT-1004 over mutant-specific KRAS inhibitors. These results highlight the promise of ADT-1004 for treatment of PDAC and other RAS-driven cancers by addressing the complex genetic landscape of many cancers and limitations from resistance to mutant specific KRAS inhibitions. Citation Format: Dhana Sekhar Reddy Bandi, Ganji P Nagaraju, Jeremy B Foote, Adam B Keeton, Xi Chen, Kristy L Berry, Yulia Y Maxuitenko, Upender Manne, Donald J Buchsbaum, Gary A Piazza, Bassel F El-Rayes. Efficacy advantages of a novel pan-RAS inhibitor, ADT-1004, over mutant- specific KRAS inhibitors for suppressing pancreatic tumor growth in murine models [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C027.

Structural insights into a shared mechanism of human STING activation by a potent agonist and an autoimmune disease-associated mutation

Stimulator of interferon gene (STING) is increasingly exploited for the potential in cancer immunotherapy, yet its mechanism of activation remains not fully understood. Herein, we designed a novel STING agonist, designated as HB3089 that exhibits robust and durable anti-tumor activity in tumor models across various cancer types. Cryo-EM analysis reveals that HB3089-bound human STING has structural changes similar to that of the STING mutant V147L, a constitutively activated mutant identified in patients with STING-associated vasculopathy with onset in infancy (SAVI). Both structures highlight the conformational changes of the transmembrane domain (TMD), but without the 180°-rotation of the ligand binding domain (LBD) previously shown to be required for STING activation. Further structure-based functional analysis confirmed a new STING activation mode shared by the agonist and the SAVI-related mutation, in which the connector linking the LBD and the TMD senses the activation signal and controls the conformational changes of the LBD and the TMD for STING activation. Together, our findings lead to a new working model for STING activation and open a new avenue for the rationale design of STING-targeted therapies either for cancer or autoimmune disorders.

A phase 1b study (STELLAR-002) of XL092 administered in combination with nivolumab (NIVO) with or without ipilimumab (IPI) or bempegaldesleukin (BEMPEG) in patients (pts) with advanced solid tumors.

TPS4600 Background: XL092 is a novel oral inhibitor of receptor tyrosine kinases, including MET, VEGFR2, and TAM kinases (AXL, MER), which are implicated in tumor growth, metastasis, angiogenesis, and immune suppression of the tumor microenvironment. XL092 has a relatively short half-life (̃21h) to support convenient daily dosing and help manage tolerability. Preclinical studies of XL092 with an anti‒PD-1 immune checkpoint inhibitor (ICI) demonstrated antitumor activity in tumor models, and BEMPEG (IL-2 pathway agonist) showed synergy with anti‒PD-L1 and anti‒CTLA-4 agents. This phase 1b trial will evaluate the safety and clinical activity of XL092 alone and in combination with NIVO (anti‒PD-1 mAb) ±IPI (anti‒CTLA-4 mAb) or ±BEMPEG in pts with advanced solid tumors including genitourinary cancers. Presented here is the study design. Methods: This multicenter phase 1b, open-label study (NCT05176483) will enroll pts with unresectable advanced or metastatic solid tumors in dose-escalation and expansion stages. In the dose-escalation stage, ̃36 pts will be enrolled in three XL092 combination therapy cohorts using a rolling 6 design. Cohort A: XL092 (starting dose [SD] 100 mg PO QD) + NIVO (360 mg IV Q3W); Cohort B: XL092 (SD 80 mg PO QD) + NIVO (3 mg/kg IV Q3W × 4, then 480 mg IV Q4W) + IPI (1 mg/kg Q3W × 4); Cohort C: XL092 (SD 100 mg PO QD) + NIVO (360 mg IV Q3W) + BEMPEG (0.006 mg/kg IV Q3W). The primary objective of the dose-escalation stage is to determine the recommended doses of XL092 with the NIVO regimens to be used in the expansion stage. The expansion stage will include cohorts of advanced genitourinary tumors: Cohort 1, clear-cell renal cell carcinoma (ccRCC), no prior systemic therapy; Cohort 2, ccRCC, 1 prior ICI combination regimen; Cohort 3, metastatic castration-resistant prostate cancer (mCRPC), 1 prior novel-hormonal therapy; Cohort 4, urothelial carcinoma (UC), 1 prior platinum-based regimen, ICI-naïve; Cohort 5, UC, ≤2 prior systemic regimens, ICI-experienced; Cohort 6, non-ccRCC, no prior systemic therapy. In each cohort, pts will be randomized to one of the following treatments (based on tumor cohort): single-agent XL092 (Cohorts 2‒6); XL092+NIVO (Cohorts 1‒6); NIVO+IPI (Cohort 1); XL092+NIVO+IPI (Cohorts 1, 3, 6); NIVO+BEMPEG (Cohort 1), XL092+NIVO+BEMPEG (Cohort 1, 2, 4‒6). Thirty pts will be enrolled in each single-agent XL092 arm and 40 pts in each combination therapy arm. Expansion stage objectives are to assess preliminary efficacy, safety, and pharmacokinetics of XL092 alone or in combination in each tumor-specific cohort. Primary efficacy endpoints include objective response rate by investigator per RECIST v1.1 and progression-free survival by blinded independent radiology committee per Prostate Working Group 3 criteria (mCRPC cohort only). The study is currently enrolling pts. Clinical trial information: NCT05176483.

E7386, a Selective Inhibitor of the Interaction between β-Catenin and CBP, Exerts Antitumor Activity in Tumor Models with Activated Canonical Wnt Signaling.

The Wnt/β-catenin signaling pathway plays crucial roles in embryonic development and the development of multiple types of cancer, and its aberrant activation provides cancer cells with escape mechanisms from immune checkpoint inhibitors. E7386, an orally active selective inhibitor of the interaction between β-catenin and CREB binding protein, which is part of the Wnt/β-catenin signaling pathway, disrupts the Wnt/β-catenin signaling pathway in HEK293 and adenomatous polyposis coli (APC)-mutated human gastric cancer ECC10 cells. It also inhibited tumor growth in an ECC10 xenograft model and suppressed polyp formation in the intestinal tract of ApcMin /+ mice, in which mutation of Apc activates the Wnt/β-catenin signaling pathway. E7386 demonstrated antitumor activity against mouse mammary tumors developed in mouse mammary tumor virus (MMTV)-Wnt1 transgenic mice. Gene expression profiling using RNA sequencing data of MMTV-Wnt1 tumor tissue from mice treated with E7386 showed that E7386 downregulated genes in the hypoxia signaling pathway and immune responses related to the CCL2, and IHC analysis showed that E7386 induced infiltration of CD8+ cells into tumor tissues. Furthermore, E7386 showed synergistic antitumor activity against MMTV-Wnt1 tumor in combination with anti-PD-1 antibody. In conclusion, E7386 demonstrates clear antitumor activity via modulation of the Wnt/β-catenin signaling pathway and alteration of the tumor and immune microenvironments, and its antitumor activity can be enhanced in combination with anti-PD-1 antibody. SIGNIFICANCE: These findings demonstrate that the novel anticancer agent, E7386, modulates Wnt/β-catenin signaling, altering the tumor immune microenvironment and exhibiting synergistic antitumor activity in combination with anti-PD-1 antibody.

Abstract 4835: LY3076226, a novel anti-FGFR3 antibody drug conjugate exhibits potent and durable anti-tumor activity in tumor models harboring FGFR3 mutations or fusions

Abstract Fibroblast growth factor receptor 3 (FGFR3) has been shown to be constitutively activated in bladder, multiple myeloma, non-small cell lung cancer (NSCLC), glioblastoma multiforme, and cervical cancer through overexpression, point mutations, and translocations. In bladder cancer, FGFR3 is typically found to be activated by mutation or over-expression. TCGA data suggests that ~48% of bladder cancer patients harbor FGFR3 mutations such as S249, Y373C and others, as well as fusion proteins of FGFR3 involving transforming acidic coiled-coil gene (TACC3) and FGFR3-BAIAP2L1. LY3076226 is an antibody-drug conjugate (ADC) comprising a fully human anti-FGFR3 antibody, IMC-D11, conjugated to a cytotoxic payload, the maytansine-derivative DM4, via a cleavable linker (sulfo-SPDB). The anti-FGFR3 Ab IMC-D11 recognizes and binds not only wild-type receptor, but also constitutively active mutant receptors and fusion proteins of FGFR3. Preclinical in vitro pharmacodynamics studies have demonstrated that LY3076226 binds to the human FGFR3 protein with high affinity, and following internalization can deliver the potent cytotoxic payload into tumor cells resulting in cell cycle arrest and cell death. In vivo studies with LY3076226 demonstrated robust antitumor efficacy resulting in tumor stasis or partial or complete tumor responses after 4 weekly doses at 5 mg/kg in bladder cancer cell lines: SW780, RT112 and UMUC-14 that harbor FGFR3-BAIAP2L1, FGFR3-TACC3 fusion or S249C mutation, respectively. We also evaluated over 90 PDXs models using a Modiplex assay and IHC to determine mutational and FGFR3 expression levels. We identified a number of bladder PDX models with R248C, S249 and G370 mutations and a single NSCLC with FGFR3-TACC3, and tested LY3076226 efficacy in these models. Interestingly the incidence of mutations and fusions in these PDX models confirmed prior TCGA results, and confirm that PDX models represent a valuable translational platform for patient tailoring. Similar to RT-112 cell line, LY3076226 significantly inhibited tumor growth in lung PDX model (LXF-2226) with FGFR3-TACC3 fusion resulting in durable complete response in 100% of mice. LY3076226 was also efficacious after 4 weekly treatments at 5 mg/kg, resulting in tumor growth inhibition, tumor stasis or tumor regressions in bladder PDX models with G370C, S249C or R248C FGFR3 mutations, respectively. Additionally, LY3076226 exhibited superior efficacy compared to the naked IMC-D11 Ab or chKTI-ADC controls. These data support the conclusion that therapy with FGFR3 targeted antibody-drug conjugate LY3076226 may confer tumor control in patients that are FGFR3 positive and harbor FGFR3 mutations or fusion proteins. Citation Format: David Surguladze, Anthony Pennello, Xiaodi Ren, Tim Mack, Alan Rigby, Paul Balderes, Elizabeth Navarro, Nelusha Amaladas, Scott Eastman, Michael Topper, Yung-mae Yao, Chris Moxham, Gregory Plowman, Dale Ludwig. LY3076226, a novel anti-FGFR3 antibody drug conjugate exhibits potent and durable anti-tumor activity in tumor models harboring FGFR3 mutations or fusions [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 4835.

Abstract CT019: ASN003, a novel highly selective BRAF and PI3K dual inhibitor: Phase I PK/PD results in patients with advanced solid tumors

Abstract Background RAS-RAF-MEK and PI3K-AKT-mTOR are two major pathways involved in tumor cell signaling and growth. Components of these pathways are frequently mutated in a broad range of tumors. ASN003 is a highly selective and potent (low nM IC50) inhibitor of BRAF and PI3K-α and -δ. ASN003 shows strong antitumor activity in tumor models harboring BRAF and PIK3CA mutations, and also in patient-derived xenograft (PDX) models that are resistant to selective BRAF and MEK inhibitors. Patients and Methods: Oral once-daily ASN003 is being evaluated for safety/tolerability and preliminary efficacy in eligible patients with advanced solid tumors using an accelerated dose titration design (Part A) and enrolling cohorts of patients diagnosed with melanoma, CRC, NSCLC and other solid tumors with a BRAF, PIK3CA mutations at MTD (Part B). Pharmacokinetic (PK) profile and the pharmacodynamic (PD) effects of ASN003 on tumor tissue biomarkers such as pERK and pS6 are being investigated in both parts of the study. Results: Patient accrual in Part A is ongoing. As of January 2018, fifteen eligible patients were enrolled in dose levels ranging from 10 - 400 mg QD and 400 mg BID. ASN003 has been well tolerated. Treatment-related adverse events (TRAEs) were mostly mild (G1) to moderate (G2). TRAEs include, rash (G3), hypersensitivity (G3) (n=1), diarrhea (G2) (n=1), hyperglycemia (G2) (n=1), rash maculo-papular (G2) (n=1), vomiting (G1) (n=3), nausea (G1) (n=2), hyperglycemia (G1) (n=2), and dry mouth/lips/skin, transient blurred vision, rash acneiform, ALT increase, cognitive disturbance and hyperkalemia. The PK profile showed dose-dependent increase in systemic exposure at steady state (Cmax up to 5,990 ng/mL, AUC0-T up to 110,000 ng.h/mL) and a half-life of 14-25 hours in general. Early evidence of biomarker changes in repeat biopsies, and clinical disease control have been observed. Conclusions: ASN003 is a novel small molecule, with uniquely selective and potent inhibition of BRAF, PI3K-α and -δ kinases. To date, ASN003 was well tolerated at doses up to 400 mg QD/BID and achieved good systemic exposure. Updated and detailed clinical safety/efficacy and PK/PD results will be presented. Citation Format: Drew Rasco, Nehal Lakhani, Ryan Sullivan, Monica Mita, Jaimini Shah, Helen Usansky, Sanjeeva Reddy, Niranjan S. Rao, Sarper Toker, Louis Denis, Keith Flaherty, Anthony Tolcher. ASN003, a novel highly selective BRAF and PI3K dual inhibitor: Phase I PK/PD results in patients with advanced solid tumors [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 CT019.

Abstract B147: A phase 1 PK/PD study of ASN003, a novel, highly selective BRAF and PI3K dual inhibitor, in patients with advanced solid tumors

Abstract Background: RAS-RAF-MEK and PI3K-AKT-mTOR are two major pathways involved in tumor cell signaling and growth. Components of these pathways are frequently mutated in a broad range of tumors. ASN003 is a highly selective and potent (low nM IC50) inhibitor of BRAF and PI3K-α and -δ (low affinity for PI3K-β). ASN003 shows strong antitumor activity in tumor models harboring BRAF and PIK3CA or PTEN mutations, and also in patient-derived xenograft (PDX) models that are resistant to selective BRAF and MEK inhibitors. Patients and Methods: Oral once-daily ASN003 is being evaluated for safety/tolerability and preliminary efficacy in eligible patients with advanced solid tumors using an accelerated dose titration design (Part A) and enrolling cohorts of patients diagnosed with melanoma, CRC, NSCLC, and other solid tumors with a BRAF, PIK3CA, or PTEN mutation at MTD (Part B). Pharmacokinetic (PK) profile and the pharmacodynamic (PD) effects of ASN003 on tumor tissue biomarkers such as pERK and pS6 are investigated in both parts of the study. Results: Patient accrual in Part A is ongoing. As of June 2017, nine eligible patients are enrolled in dose levels ranging from 10 - 240 mg QD. ASN003 has been well tolerated. Treatment-related adverse events (TRAEs) were mild (G1) to moderate (G2). TRAEs include diarrhea (G2) (n=1), nausea/vomiting (G1), blurred vision (G1), and dry mouth/lips/skin (G1). Transient G1 elevation of glucose and insulin c-peptide levels has been noted in 1 pt. No G3/4 or serious TRAEs have been observed to date. The PK profile showed dose-dependent, systemic exposure with Cmax ranging from 74 to 1055 ng/mL, AUCT from 912 to 20100 ng.h/mL. Conclusions: ASN003 is a novel small molecule, with uniquely selective and potent inhibition of BRAF, PI3K-α and -δ kinases. To date, ASN003 was well tolerated at doses up to 240 mg QD and achieved good systemic exposure. Updated and detailed clinical safety/efficacy and PK/PD results will be presented. Citation Format: Drew Rasco, Nehal Lakhani, Ryan Sullivan, Monica Mita, Jaimini Shah, Helena Usansky, Sanjeeva Reddy, Niranjan Rao, Louis J. Denis, Anthony Tolcher, Keith Flaherty. A phase 1 PK/PD study of ASN003, a novel, highly selective BRAF and PI3K dual inhibitor, in patients with advanced solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B147.

Abstract 3741: Antimetastatic activity of ISTH0047, a potent and selective TGF-beta 2 antisense oligonucleotide, in syngeneic lung metastatic model of mouse 4T1 mammary carcinoma

Abstract Transforming growth factor beta (TGF-β) isoforms are the primary mediators for TGF-β signaling via TGF-β receptors and downstream phosphorylation/dephosphorylation cascade. TGF-β is associated with a wide range of biological processes in oncology, including tumor cell invasion, migration, angiogenesis, immunosuppression, as well as regulation of tumor stem cell properties. Mouse 4T1 mammary carcinoma cell line is a transplantable tumor cell line that is highly tumorigenic and invasive and, unlike most tumor models, can spontaneously metastasize from the primary tumor in the mammary gland to multiple distant sites including lymph nodes, blood, liver, lung, brain, and bone. Considering rather challenging preclinical evaluation of antitumor activity in tumor models, mouse 4T1 mammary carcinoma model has been widely used in the literature for evaluation of TGF-β antagonists. In this report, we describe the efficacy of ISTH0047 - a potent and selective TGF-β2 antisense oligonucleotide - in murine 4T1 primary tumors and lung metastasis following tumor cell injection into the mammary fat pad (orthotopic tumor model) of syngeneic Balb/c mice. Consistent with literature data generated with other classes of TGF-β antagonists (e.g., small-molecule kinase inhibitors, antibodies or TGF-β trap agents), although limited antitumor activity was demonstrated on primary tumor growth, marked and statistically significant decrease of lung metastasis number was observed upon subcutaneous administrations of ISTH0047. In addition, side by side comparison with murine surrogates of CTLA-4 or PD-1 antibodies indicated similar efficacy of all test items on lung metastasis in this model. Taken together, these encouraging results pave the way for in-depth preclinical evaluation of both ‘seed and soil’ theory and efficacy of combination regimen (immunomodulation) for better clinical outcome. Citation Format: Katja Wosikowski, Kathy Hasenbach, Jutta Petschenka, Diana Barea Roldan, Sebastian Kreiter, Ugur Sahin, Guillaume Serin, Julie-Orlane Redon, Marc Hillairet de Boisferon, Francis Bichat, Hanna Kohonen, Michel Janicot. Antimetastatic activity of ISTH0047, a potent and selective TGF-beta 2 antisense oligonucleotide, in syngeneic lung metastatic model of mouse 4T1 mammary carcinoma. [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 3741.

PF-06463922 is a potent and selective next-generation ROS1/ALK inhibitor capable of blocking crizotinib-resistant ROS1 mutations

Oncogenic c-ros oncogene1 (ROS1) fusion kinases have been identified in a variety of human cancers and are attractive targets for cancer therapy. The MET/ALK/ROS1 inhibitor crizotinib (Xalkori, PF-02341066) has demonstrated promising clinical activity in ROS1 fusion-positive non-small cell lung cancer. However, emerging clinical evidence has shown that patients can develop resistance by acquiring secondary point mutations in ROS1 kinase. In this study we characterized the ROS1 activity of PF-06463922, a novel, orally available, CNS-penetrant, ATP-competitive small-molecule inhibitor of ALK/ROS1. In vitro, PF-06463922 exhibited subnanomolar cellular potency against oncogenic ROS1 fusions and inhibited the crizotinib-refractory ROS1(G2032R) mutation and the ROS1(G2026M) gatekeeper mutation. Compared with crizotinib and the second-generation ALK/ROS1 inhibitors ceritinib and alectinib, PF-06463922 showed significantly improved inhibitory activity against ROS1 kinase. A crystal structure of the PF-06463922-ROS1 kinase complex revealed favorable interactions contributing to the high-affinity binding. In vivo, PF-06463922 showed marked antitumor activity in tumor models expressing FIG-ROS1, CD74-ROS1, and the CD74-ROS1(G2032R) mutation. Furthermore, PF-06463922 demonstrated antitumor activity in a genetically engineered mouse model of FIG-ROS1 glioblastoma. Taken together, our results indicate that PF-06463922 has potential for treating ROS1 fusion-positive cancers, including those requiring agents with CNS-penetrating properties, as well as for overcoming crizotinib resistance driven by ROS1 mutation.

Inhibition of nicotinamide phosphoribosyltransferase (NAMPT) as a therapeutic strategy in cancer.

NAD is a metabolite that is an important cofactor and second messenger for a number of cellular processes such as genomic stability and metabolism that are essential for survival. NAD is generated de novo from tryptophan or recycled from NAM through the NAMPT-dependent salvage pathway. Alternatively, cells can convert NA to NAD through the NAPRT1-dependent salvage pathway. Tumor cells rapidly turn over NAD but do not efficiently utilize the de novo synthesis pathway. Hence, they are more reliant on the NAMPT salvage pathway for NAD regeneration making this enzyme an attractive therapeutic target for cancer. NAMPT is over-expressed in a number of cancer types such as colorectal, ovarian, breast, gastric, prostate, gliomas as well as B-cell lymphomas. A number of novel, potent and selective NAMPT small molecule inhibitors have been synthesized to date that have displayed robust anti-tumor activity in tumor models in vitro and in vivo. These inhibitors efficiently suppress NAD production in a time dependent manner and sustained reduction of NAD levels leads to loss of ATP and ultimately cell death. This review will summarize the chemical properties of these unique NAMPT inhibitors as well as their mechanism of action, pharmacodynamic activity and efficacy in tumor models in vitro and in vivo. An overview of biomarkers that predict response to treatment and mechanisms of resistance to NAMPT inhibitors will also be provided. Additionally, NAMPT inhibitors that have advanced into clinical trials will be reviewed along with experimental strategies tested to potentially increase the therapeutic index of these inhibitors.

Sensitivity of Selected Human Tumor Models to PF-04217903, a Novel Selective c-Met Kinase Inhibitor

The c-Met pathway has been implicated in a variety of human cancers for its critical role in tumor growth, invasion, and metastasis. PF-04217903 is a novel ATP-competitive small-molecule inhibitor of c-Met kinase. PF-04217903 showed more than 1,000-fold selectivity for c-Met compared with more than 150 kinases, making it one of the most selective c-Met inhibitors described to date. PF-04217903 inhibited tumor cell proliferation, survival, migration/invasion in MET-amplified cell lines in vitro, and showed marked antitumor activity in tumor models harboring either MET gene amplification or a hepatocyte growth factor (HGF)/c-Met autocrine loop at well-tolerated dose levels in vivo. Antitumor efficacy of PF-04217903 was dose-dependent and showed a strong correlation with inhibition of c-Met phosphorylation, downstream signaling, and tumor cell proliferation/survival. In human xenograft models that express relatively high levels of c-Met, complete inhibition of c-Met activity by PF-04217903 only led to partial tumor growth inhibition (38%-46%) in vivo. The combination of PF-04217903 with Recepteur d'origine nantais (RON) short hairpin RNA (shRNA) knockdown in the HT29 model that also expresses activated RON kinase-induced tumor cell apoptosis and resulted in enhanced antitumor efficacy (77%) compared with either PF-04217903 (38%) or RON shRNA alone (56%). PF-04217903 also showed potent antiangiogenic properties in vitro and in vivo. Furthermore, PF-04217903 strongly induced phospho-PDGFRβ (platelet-derived growth factor receptor) levels in U87MG xenograft tumors, indicating a possible oncogene switching mechanism in tumor cell signaling as a potential resistance mechanism that might compromise tumor responses to c-Met inhibitors. Collectively, these results show the use of highly selective inhibition of c-Met and provide insight toward targeting tumors exhibiting different mechanisms of c-Met dysregulation.

311. Oncolytic Adenovirus CG5757 Preferentially Infects Primary Human Tumor Tissues and Shows Strong Anti-Tumor Activity in Tumor Models Following Systemic Administration

Top of pageAbstract A human adenovirus serotype 5 based oncolytic virus CG5757 was designed to preferentially replicate in and kill cancer cells that have a defective retinoblastoma (Rb) pathway and overexpress telomerase. Tumor selectivity of CG5757 was examined using a newly developed ex vivo primary tumor tissue culture model. Primary human colorectal tumors were obtained after surgical resection and placed in Millicell insert with media containing hormones, which can keep tissue viable for about 5 days. The paired tumor or normal tissues from same tissue sample were used in a viral infection experiment to determine the tumor selectivity of CG5757. Cultured tissues were infected with CG5757 or wild type (wt) Ad5 for five days, and progeny viral production was determined by TCID50 assay. Results of the paired tissue cultures from five colon cancer patients indicate that wt Ad5 has similar viral productivity in tumor and normal tissues, whereas CG5757 has higher productivity in tumor tissues. In general, CG5757 produces 100- to 1,000-fold more virus in tumor tissue compared to normal tissue. Immunohistochemical staining for adenoviral E1A shows that CG5757 has positive infection only in the cancer tissue (colon), whereas no signal is detected in normal tissues of colon, pancreas or spleen. Similarly in vitro viral specificity characterization using a panel of tumor cell lines also suggest a strong tumor selectivity of CG5757. Anti-tumor efficacy of CG5757 following intravenous injection was examined in a subcutaneous tumor model. In this study, pre-established prostate cancer LNCaP xenografts in nude mice were treated with two intravenous injections of 4|[times]|1010 viral particles of CG5757 given at a 3-day interval. Significant anti-tumor efficacy was observed in CG5757-treated animals. Eight weeks after treatment, CG5757-treated animals exhibited approximately 72% inhibition of tumor growth. These studies demonstrate the potential therapeutic efficacy of such dual promoter-controlled oncolytic adenoviruses in cancers that are Rb-defective and telomerase-positive.