96 Thursday 8 November 2012 Poster Session – Monoclonal Antibodies and Targeted Toxins/Nuclides

were treated with MGCD265 and almost complete inhibition of tumor growthwas observed. The inhibition of Met phosphorylation in vitro was alsoassociated with the inhibition of phosphorylation of Met in the MKN45xenografts as assessed by immunohistochemistry.Conclusions: Using an in vitro surrogate bioassay to monitor targetinhibition, up to 75% inhibition of Met phosphorylation occurred atMGCD265 exposures reached to-date in patients treated with single agentMGCD265. This degree of inhibition surpassed that observed in the MKN45xenograft model at exposures of MGCD265 that demonstrated tumorgrowth inhibition. Dose escalation continues and updates will be providedat the meeting.

313 POSTERA Pooled Analysis to Evaluate the Incidence of Proteinuria,

Hypoalbuminemia, and Edema Secondary to MET and VEGFR

Inhibition

P. Bradbury1, E. Eisenhauer1, D. Rayson2, S. Lupichuk3, S. Chia4,N. Leighl5, C. Ho4, L. Seymour1. 1Queen’s University, NCIC Clinical TrialsGroup, Kingston ON, Canada; 2Dalhousie University, Atlantic ClinicalCancer Research Unit, Halifax NS, Canada; 3University of Calgary,Tom Baker Cancer Centre, Calgary AB, Canada; 4British ColumbiaCancer Agency, Medical Oncology, Vancouver BC, Canada; 5Universityof Toronto, Princess Margaret Hospital, Toronto ON, Canada

Background: Proteinuria and hypoalbuminemia are associated with anti-angiogenic and MET pathway inhibiting agents which may require doseadjustments or discontinuation of treatment. Foretinib is an oral multikinase-inhibitor of MET, RON, AXL, TIE-2 and VEGFR, with activity in papillaryrenal cell and hepatocellular carcinoma. We evaluated the incidence andoutcome of proteinuria, hypoalbuminemia and edema in a pooled analysisof three NCIC CTG trials evaluating foretinib in lung and breast cancer.Methods: This is a pooled descriptive analysis of three trials, (IND196: aphase I/II study of foretinib in patients with previously treated non-smallcell lung cancer receiving standard erlotinib therapy; IND197: a phase IIstudy of foretinib in patients with estrogen receptor, progesterone receptorand human epidermal growth factor receptor 2 (HER2) negative, recurrent/metastatic breast cancer and IND198: a phase I/II study of foretinib incombination with lapatinib in patients with human epidermal growth factorreceptor (HER2) over-expressing metastatic breast cancer) to evaluatethe incidence and outcome of proteinuria and peripheral edema. Adverseevents were graded using NCI Common Terminology Criteria for AdverseEvents (CTCAE) v.4.Results: 82 patients have been enrolled to date (62 female; median age60 (29−86); PS 0/1/2:36/43/3; 31 NSCLC. There have been five cases ofproteinuria (grade 3 in 4), 23 cases of a fall in albumin levels from baselineto grade �2 and 9 cases of edema (grade 3 in 1; grade 2 in 2). The mediannumber of cycles at first report of proteinuria was 4 (1−20) and it led totreatment discontinuation in 2 cases. Of these 5 cases, 2 had a prior historyof hypertension, and 2 others developed hypertension on study. Concomi-tant edema occurred in 3 of the cases. The median number of cycles at firstreport of edema was 3 (1−20). In the absence of proteinuria, edema wasreported as mild in the majority of cases (86%) and did not lead to treatmentdiscontinuation. Comparison of the incidence of these adverse eventswith data from other pooled NCIC CTG trials with other anti-angiogenicagents, and agents with no putative mechanism to induce proteinuria andhypoalbuminemia to elucidate whether the incidence is higher is on-going.Conclusions: Proteinuria, hypoalbuminemia and edema appear commonadverse events associated with MET and VEGFR inhibition. Edema is amore frequent adverse event compared with proteinuria but is more likely tobe mild in the absence of proteinuria. Comparison of the incidence of theseadverse events with additional pooled NCIC CTG trials of anti-angiogenicagents, and agents with no putative mechanism to induce these adverseevents is underway.

314 POSTERBiomarker Analysis in the First-in-human OMP-59R5 (anti-Notch2/3)

Phase I Study Demonstrates Pharmacodynamic (PD) Modulation of

the Notch Pathway in Patients with Advanced Solid Tumors

A. Tolcher1, A.M. Kapoun2, M. Wang2, C. Zhang2, A. Patnaik1,K. Papadopoulos1, R. Chugh3, V. Thorpe3, J. Dupont4, D.C. Smith3.1South Texas Accelerated Research Therapeutics (START), ClinicalResearch, San Antonio TX, USA; 2OncoMed Pharmaceuticals Inc.,Translational Medicine, Redwood City CA, USA; 3University of Michigan,Clinical Research, Ann Arbor MI, USA; 4OncoMed PharmaceuticalsInc., Product Development, Redwood City CA, USA

Background: The Notch pathway plays a central role in embryonicdevelopment, the regulation of stem and progenitor cells, and is implicatedin many human cancers. OMP-59R5 is a fully human IgG2 which inhibits

the signaling of both Notch2 and Notch3 receptors. Mouse xenograftstudies using minimally-passaged, patient-derived xenografts show thatOMP-59R5 impedes tumor growth and reduces cancer stem cell (CSC)frequency in multiple tumor types. OMP-59R5 modulates gene expressionin tumor cells associated with stem cell pathways and down-regulatesstromal genes indicative of inhibiting the function of pericytes in tumorvasculature. As such, OMP-59R5 is a novel anti-cancer agent that inhibitstumor growth through direct actions on tumor cells, including CSCs, andeffects on the stroma and vasculature. We sought to determine the PDeffects of various doses of OMP-59R5 on Notch signaling, stem cellpathways, and other aspects of its mechanism of action by examiningsurrogate tissues (hair follicle and blood cells) and also serial tumorbiopsies from Phase I patients.Methods and Results: PD biomarker analysis of surrogate tissuesand tumors was performed in the OMP-59R5 phase Ia dose escalationstudy in patients with solid tumors. Thirty-two patients enrolled in 7dose-escalation cohorts at 0.5, 1, 2.5, and 5mg/kg administered weekly(QW), 5 and 10mg/kg administered every other week (QOW), and7.5mg/kg administered every three weeks (Q3Wk). Notch pathway-relatedgenes including HES1, NEURL, MAML2 and POFUT1 were found to beregulated in blood cells at doses of 1mg/kg and above. OMP-59R5 plasmabiomarkers were also modulated by OMP-59R5, as were stem cell anddifferentiation markers in hair follicles, including KITLG. In tumors, Notchpathway related micro RNAs eg. mir199b and mir150 were induced post-treatment consistent with suppression of the Notch pathway by OMP-59R5.Conclusions: The PD effects of OMP-59R5 on Notch targets, stem cellpathways in surrogate tissues and in tumor tissue on serial biopsy wereclearly established in this first-in-human study.

Monoclonal Antibodies and Targeted

Toxins/Nuclides

315 POSTERImmunoPET and Biodistribution with Human Epidermal Growth

Factor Receptor 3 Targeting Radiolabeled Antibody 89Zr-GE-huMAb-

HER3

A.G.T. Terwisscha van Scheltinga1, M.N. Lub-de Hooge2, K. Abiraj3,C.P. Schroder1, L. Pot1, B. Bossenmaier4, M. Pickl4, T. Friess4,J.G.W. Kosterink2, E.G.E. de Vries1. 1University of Groningen UniversityMedical Center Groningen, Department of Medical Oncology, Groningen,The Netherlands; 2University of Groningen University Medical CenterGroningen, Department of Hospital and Clinical Pharmacy, Groningen,The Netherlands; 3F. Hoffmann-La Roche AG, pRED PharmaResearch & Early Development Translational Research Sciences, Basel,Switzerland; 4Roche Diagnostics GmbH, pRED Pharma Research &Early Development, Penzberg, Germany

Background: The humanized monoclonal antibody with high affinity for thehuman epidermal growth factor receptor (HER) 3, GE-huMAb-HER3, is aglycoengineered, IgG1 class antibody. By labeling GE-huMAb-HER3 withzirconium-89 (89Zr) we aimed to visualize in vivo HER3 expression andstudy the biodistribution of this antibody in human tumor bearing mice.Methods: GE-huMAb-HER3 was conjugated with tetrafluorophenol-N-succinyldesferal and radiolabeled with 89Zr. Quality control included sizeexclusion HPLC analysis, stability of the radiolabeled compound andimmunoreactivity analysis. In vivo imaging and ex vivo experiments wereconducted using female SCID Beige mice. Biodistribution of 89Zr-GE-huMAb-HER3 was studied in subcutaneously xenografted FaDu humanhead and neck squamous cell carcinoma (HNSCC) tumor cells (HER3positive). Dose-dependency of 89Zr-GE-huMAb-HER3 organ distributionand specific tumor uptake was assessed by administering doses rangingfrom 0.05 to 10mg/kg GE-huMAb-HER3 to mice. Biodistribution wasanalyzed at 24 and 144 h after injection. MicroPET imaging was performedat 1, 3 and 6 days after injection of 1.0mg/kg 89Zr-GE-huMAb-HER3 in theFaDu and human non-small cell lung cancer (NSCLC) cell lines H441, QG-56 and Calu-1 xenografts with varying HER3 expression. To discriminatebetween specific and non-specific tumor uptake and biodistribution, 111In-IgG was co-injected in all animals.Results: 89Zr-GE-huMAb-HER3 can be produced with high specificactivity and purity, is stable during 1 week after radiolabeling and haspreserved immunoreactivity. Biodistribution analyses showed a dose- andtime-dependent 89Zr-GE-huMAb-HER3 tumor uptake. The highest relativeuptake of 89Zr-GE-huMAb-HER3 occurred in the 0.05mg/kg dose groupwith 21.2 and 27.5%ID/g at 24 and 144 h after tracer injection respectively,the lowest relative uptake was found in the 10mg/kg group; 7.1%ID/g 24 hand 10.1%ID/g 144 h after tracer injection. MicroPET imaging revealedspecific tumor uptake of 89Zr-GE-huMAb-HER3 in FaDu and H441 models

Poster Session – Monoclonal Antibodies and Targeted Toxins/Nuclides Thursday 8 November 2012 97

with an increase in tumor uptake over time. 89Zr-GE-huMAb-HER3 didnot specifically accumulate in non-tumor organs. Biodistribution data wasconsistent with the microPET findings, showing ex vivo tumor uptake of89Zr-GE-huMAb-HER3 of 13.9, 19.0, 9.2 and 7.6%ID/g in FaDu, H441,QG56 and Calu-1 xenografts respectively.Conclusion: 89Zr-GE-huMAb-HER3 is specifically taken up in HER3overexpressing tumors. PET imaging with this tracer provides real-timenon-invasive information about GE-huMAb-HER3 distribution and tumoraccumulation.

316 POSTERMM-141, a Novel Bispecific Antibody Co-targeting IGF-1R and ErbB3,

Inhibits PI3K/Akt/mTOR Pro-survival Signaling in Preclinical Cancer

Models

J. Baum1, B. Johnson1, S. Adams1, J. Tang1, S. Iadevaia1, B. Schoeberl1,U. Nielsen1, J. Fitzgerald1, A. Lugovskoy1. 1Merrimack Pharmaceuticals,Cambridge Massachusetts, USA

Monospecific antibody therapies have significantly advanced our ability totreat cancer, but their effectiveness over time is often limited due to theemergence of acquired resistance to therapy. This, in part, can be explainedby the tumor cells being able to respond to multiple pro-survival stimuli,such as growth factors. We show that many cancer cell lines frequentlyrely on Insulin-like growth factor 1 (IGF-1) and Heregulin (HRG) signalingin a redundant fashion to support their survival and proliferation. Furtherwe demonstrated that heregulin secretion or ErbB3 up-regulation cancompensate for the IGF-1/IGF-1R blockade. To address this challenge, weused a Network Biology approach to design and optimize a novel bispecificantibody, MM-141, for co-targeting ErbB3 and IGF-1R. MM-141 is a fullyhuman tetravalent antibody that inhibits both proliferative and metabolicsignals in cancer cells. MM-141 blocks IGF-1, IGF-2, and HRG binding toIGF1-R and ErbB3, and causes downregulation of receptor homodimers aswell as IGF-1R-InsR, ErbB1-ErbB3 and ErbB2-ErbB3 heterodimers. MM-141 does not bind to other ErbB family receptors or homodimers of insulinreceptor, thus reducing the risk of metabolic side effects. MM-141 inhibitsphosphorylation of IGF-1R and ErbB3 as well as downstream activationof the PI3K/Akt/mTOR pathway. MM-141 displays activity in vitro in thepresence of single or multiple ligands, over a broad range of physiologicreceptor profiles. Inhibition of growth by MM-141 has been observed in vitroas well as in vivo. We have demonstrated monotherapy activity in xenograftmodels of sarcoma (SK-ES-1), prostate cancer (DU145), pancreatic cancer(BxPC-3) and renal cell carcinoma (Caki-1). MM-141 shows greater activitythan monospecific antibodies and their combination in tumors where bothIGF-1R and ErbB3 signaling are present. Pharmacodynamic (PD) profilingstudies have demonstrated that this is largely due to the ability of MM-141 to control feedback loops through autocrine HRG signaling, FoxO-mediated upregulation of RTKs, and re-activation of Akt by ribosomal S6kinase (S6K) and insulin receptor substrate 1 (IRS-1). MM-141 potentiatesthe activity of both targeted therapies (everolimus) and chemotherapies(gemcitabine) through the combined inhibition of PI3K/Akt/mTOR signalingand superior control over network adaptation in response to inhibitionof the PI3K/Akt/mTOR axis. Our preclinical studies reveal that MM-141has favorable pharmaceutical properties and pharmacokinetic profiles.Taken together, these results suggest advancing MM-141 into clinicaldevelopment to assess its potential to be an effective therapeutic fortreatment of patients with solid tumors.

317 POSTERSchedule Dependent Tumor Cell Response to Radiation When

Combined with Anti-IGF1R and Anti-EGFR Antibodies

U. Raju1, D. Molkentine1, D. Valdecanas1, K.K. Ang2. 1University ofTexas M.D. Anderson Cancer Center, Experimental Radiation Oncology,Houston Texas, USA; 2University of Texas M.D. Anderson Cancer Center,Radiation Oncology, Houston Texas, USA

Background: Higher IGF-1R expression was associated with resistanceto EGFR inhibitors and ionizing radiation (IR). We investigated the effectsof IMC-A12 (IGF-1R antibody) and cetuximab (EGFR antibody) on theresponse of head and neck squamous cell carcinoma (HNSCC) cell linesto IR and mechanisms leading to radioresistance.Materials and Methods: HNSCC lines expressing different levels of EGFRand IGF-1R were studied. The effects of IMC-A12 and cetuximab on cellviability (MTS assay) and radiosensitivity (clonogenic survival assay) weredetermined. Various scheduling of drugs were examined. Alterations intarget signaling were analyzed by Western blots.Results: Cells that express relatively more baseline EGFR were moreresponsive to cetuximab. IMC-A12 alone did not reduce cell viability butelicited a moderate radiosensitization of a few cell lines (enhancementfactors, EFs, ranged from 1.11 to 1.67) given 6 h before till 66 h after IR.Cetuximab, as a single agent suppressed the cell viability in 5 cell lines but

had no effect in 3 cells lines. In combination with IR, cetuximab given 6 hbefore till 66 h after IR significantly enhanced the radiosensitivity of three(e.g.: HN-5, EF: 2.55) out of 6 lines. A 48 h exposure to cetuximab beforeIR, however, increased radioresistance of HN-5 and FaDu without affectingUMSCC-1. Continuing with cetuximab for 72 h after IR resulted in a netradiation sensitization in HN-5, partially reversed radioresistance in FaDu,and enhanced the radiosensitivity of UMSCC-1. Western blots revealedthat 48 h exposure to cetuximab upregulated IGF-1R in FaDu (2.28 fold)and UMSCC-1 (1.26 fold) but not in HN-5; however, EGFR was upregulatedin HN-5. IGF-1R inhibition by IMC-A12 had no effect on HN-5, reverted theradiation response partially in FaDu, and increased the net radiosensitivityof UMSCC-1. Compared to EGFR inhibition alone, co-targeting of bothpathways did not yield a better effect on HN-5, reverted radiosensitivity tothe baseline level in FaDu, but further increased UMSCC-1 radiosensitivity.Conclusion: This study showed that some tumors responded to prolongedEGFR inhibition by upregulating other pro-survival RTK signaling, e.g. IGF-1R. EGFR appeared to be the main pro-survival signaling in HN-5 asEGFR inhibition yielded consistent sensitization that was not enhancedby IGF-1R blockade. UMSCC-1 seemed to rely on EGFR and IGF-1Rsignaling as dual inhibition yielded better sensitization than single pathwayblockade. In FaDu, IGF-1R could become a major pro-survival signaling asits induced upregulation was associated with increased resistance that wasonly reverted by co-targeting IGF-1R. Taken together our data suggest thattherapeutic benefit would result from combining cetuximab and IMC-A12with IR in some HNSCC.Supported by R0−1 CA168485 supplemented by Gilbert H. FletcherMemorial Distinguished Chair.

318 POSTEREffects of Radiologic Tumor Response of Anti-Glypican-3 GC33

and Multi Tyrosine Kinases Inhibitor Sorafenib in Hepatocellular

Carcinoma

G.K. Abou-Alfa1, B. Zhao2, J.F. Chou3, J. Ma4, M. Capanu3,M. Koga5, R. Lee6, T. Othomo7, J. Germino8, L. Schwartz2. 1MemorialSloan-Kettering Cancer Center and Weill Medical College at CornellUniversity, Medicine, New York NY, USA; 2Columbia University Collegeof Physicians and Surgeons, Radiology, New York NY, USA; 3MemorialSloan-Kettering Cancer Center, Epidemiology and Biostatistics, NewYork NY, USA; 4Memorial Sloan-Kettering Cancer Center, Medicine,New York NY, USA; 5KM Pharmaceutical Consulting LLC, Medical AffairsOncology, Washington DC, USA; 6Hoffmann-La Roche Inc., TranslationalMedicine, Nutley NJ, USA; 7 Chugai Pharmaceutical Co. Ltd., ProjectManagement, Tokyo, Japan; 8Bayer HealthCare Pharmaceuticals Inc.,Medical Affairs Oncology, Wayne NJ, USA

Background: Central tumor necrosis in response to multi-tyrosine kinaseinhibitor sorafenib was previously reported. Humanized anti-glypican-3antibody, GC33 anti-tumoral effect as a single agent and in combinationwith sorafenib continues to be studied. We assessed RECIST and tumornecrosis based radiologic parameters of response in patients treated withGC33, sorafenib, or the combination.Material and Methods: Triphasic computed tomography (CT) scans wereperformed before and after treatment on 29 patients enrolled in threemulti-center clinical trials in HCC: GC 33 (8), sorafenib (12), and GC 33plus sorafenib (9). De-identified CT images were transferred to a centralimage analysis laboratory where lesion and central necrosis volumeswere semi-automatically quantified. Overall survival (OS), progression-free-survival (PFS) and time-to-progression (TTP) were assessed clinicallyfrom the start of first therapy. Patients were followed-up until death(OS), progression (TTP), or until progression or death (PFS), whicheveroccurred first. Univariate Cox-models stratified by center were employedto evaluate the association between OS, PFS, TTP, and the differentradiologic parameters treated as time-dependent covariates. Changesin the radiologic parameters from baseline to first CT scan were alsoevaluated for association with pre-treatment tumor biopsy samples GPC-3expression by immunohistochemistry (IHC) on all GC33 and GC33 plussorafenib treated patients using Spearmen correlation coefficients andlinear regression model adjusted for study centers.Results: A trend towards significance was noted between RECIST andTTP among all GC33 treated patients (HR 1.01, 95%CI 1–1.02, p = 0.06).A significant correlation was noted between total N/TV and OS in thesorafenib only group (HR 1.06, 95%CI 1–1.131, p = 0.05) and all sorafenibtreated patients (HR 1.09, 95%CI 1.02–1.15, p = 0.01). There was nosignificant correlation noted between GPC3 IHC expression and changesin RECIST and TN/V.Conclusions: In this exploratory study, GC33 seems to exert its treatmenteffect by reducing tumor volume in GPC3 high expression tumors, whilesorafenib exerts tumor necrosis effect that is shown to correlate with OS.Based on the combination data of GC33 plus sorafenib, GC33 does notseem to block sorafenib effect on tumor necrosis.