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Abstract Abstract 2617 Introduction: ABT-348 is a potent, novel, adenosine triphospate competitive inhibitor of Aurora A, B and C kinases. ABT-348 is also a potent inhibitor of all members of the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) receptor tyrosine kinase (RTK) families. ABT-348 has demonstrated strong antitumor activity in a variety of preclinical cancer cell line models, in vitro and in vivo, including leukemias as monotherapy and in combination with the DNA methyltransferase inhibitor, azacitidine. Objectives: The primary objectives of this study are to determine the safety and pharmacokinetics (PK) of orally and IV administered ABT-348 as monotherapy or in combination with azacitidine in patients (pts) with advanced hematologic malignancies. Secondary objectives include determination of the maximum tolerated dose (MTD) and exploration of biomarkers associated with ABT-348 activity. Methods: This phase 1 dose-escalation study of ABT-348 utilizes a modified continual reassessment method in pts with advanced hematologic malignancies: acute myelogenous leukemia (AML), acute lymphoblastic leukemia, chronic myelogenous leukemia (CML), chronic lymphocytic leukemia and myelodysplasia (MDS). Adult pts with histological or cytological confirmed disease, ECOG status 0–2, adequate hematological, renal and hepatic function and without significant hypertension or proteinuria are eligible. This study has four arms consisting of ABT-348 administered on a 28-day (D) cycle. Pts receive ABT-348 monotherapy once daily (QD, Arm A) or twice daily (BID; Arm B) on Days (D) 1, 8, and 15 of a 28-day cycle under fasting conditions. In Arm C, ABT-348 is given on the same schedule as Arm A in combination with azacitidine (75 mg/m2) administered IV or SC on Days 1 – 7 of each 28-day cycle. In Arm D, pts receive ABT-348 monotherapy on the same schedule as Arm A, but via IV administration. Samples are collected for PK and biomarker analyses. Pts are treated until progressive disease (PD) or unacceptable toxicity. Adverse event (AE) severity is graded using NCI-CTCAE v4.0. Results: 39 pts (median age, 66 y [45–86]) have enrolled (Arm A, n=32; Arm B, n=4; Arm C, n=3). Of these pts, 27 had AML, 11 had MDS and 1 had CML. Pts received a median of 4 prior therapies (range, 1 – 8). Best response to last prior therapy was: complete or partial response in 3 pts, stable disease in 11 pts, PD in 24, and not determined in 1. Dose escalation is shown in the table. The first dose-limiting toxicity (DLT) of grade 3 pancreatitis was observed at 640 mg in Arm A. Due to this DLT, along with a second case of grade 3 pancreatitis, further enrollment in Arm A was held and Arms B and C were opened. A DLT of grade 4 acute kidney injury was seen at 440 mg in Arm C. ABT-348-related AEs in greater than 2 pts were proteinuria (23%), nausea (21%), diarrhea (18%), hypertension (13%), vomiting (10%) and fatigue (8%). Grade 3/4 ABT-348-related AEs were hypertension (13%), pancreatitis (5%), acute kidney injury (3%) and diarrhea (3%). One patient in Arm A achieved a CRi (640 mg). Five of 32 pts in Arm A were treated for ≥4 cycles, including 2 of 7 pts at ABT-348 doses ≥ 640 mg. Based on preliminary PK analyses, Cmax and AUC of ABT-348 were approximately dose proportional in the dose range studied (10–690 mg); co-administration of azacitidine had no apparent effect on ABT-348 PK. Evidence of dual aurora/VEGF receptor kinase inhibition has been demonstrated by induction of polyploidy and PlGF, respectively. 33 pts have discontinued and 6 remain on study. Conclusions: ABT-348 has demonstrated on-target biomarker and clinical activity in pts with advanced hematologic magnancies, and was well tolerated at doses below 640 mg in Arm A. PK appears to be dose-proportional. Dose escalation is ongoing in Arms B and C (with azacitidine); an IV formulation of ABT-348 will also be evaluated. Disclosures: Off Label Use: Clofarabine in AML. Tibes:Abbott: Research Funding. Chiu:Abbott: Employment, Owns stocks Other. Xiong:Abbott: Employment, own Abbott stock Other. Qin:Abbott: Employment. Ansell:Abbott: Employment, own Abbott stock Other. Albert:Abbott: Employment, own Abbott stock Other. Tse:Abbott: Employment, own Abbott stock Other. Oliver:Abbott: Employment, own Abbott stock Other. Sajwani:Abbott: Employment, own Abbott stocks and participated in study design, data collection, analysis, interpretation and reviewing approving study documents related to ABT-348 programs. Other. McKee:Abbott: Employment, own Abbott stocks Other. Ricker:Abbott: Employment, own Abbott stocks Other.

Abstract Introduction: Daratumumab is a human CD38 IgGκ monoclonal antibody that demonstrated significant activity and a manageable safety profile in combination with bortezomib and dexamethasone. In a randomized phase 3 study, daratumumab in combination with bortezomib and dexamethasone (DVd) significantly prolonged progression-free survival (PFS) versus bortezomib and dexamethasone alone (Vd) in a pre-specified interim analysis of patients (pts) with relapsed or refractory multiple myeloma (RRMM; Palumbo A. N Engl J Med 2016; in press). Herein, we examine subgroups from this study to compare the efficacy of DVd vs Vd in bortezomib-naive and bortezomib-experienced pt populations. In addition, the efficacy of DVd vs Vd in pts who were refractory to lenalidomide at last prior line of therapy was also evaluated. Methods: Pts who received ≥1 prior line of therapy were randomized (1:1) to 8 cycles (q3w) of Vd (bortezomib: 1.3 mg/m2 SC on Days 1, 4, 8, 11; dexamethasone: 20 mg PO on Days 1, 2, 4, 5, 8, 9, 11, 12) with or without daratumumab (16 mg/kg IV qw in Cycles 1-3, Day 1 of Cycles 4-8, then q4w until progression). Pts who were refractory to bortezomib were not eligible. The primary endpoint was PFS. Bone marrow aspirate samples that had been prepared with Ficoll were evaluated for minimal residual disease (MRD) using three different thresholds (10-4, 10-5, and 10-6) based on the ClonoSEQ assay (Adaptive Biotechnologies, Seattle, WA, USA). Results: Median follow-up was 7.4 months. Among bortezomib-naive pts (DVd, n=89; Vd, n=83), PFS was significantly improved with DVd vs Vd (median: not reached [NR] vs 7.5 months; HR, 0.25; 95% CI, 0.13-0.47; P<0.0001); estimated 12-month PFS rates were 72% vs 28%, respectively. ORR was 88% with DVd vs 70% with Vd (P=0.0040), with ≥very good partial response (VGPR) rates of 72% vs 42% (P<0.0001), and ≥complete response (CR) rates of 30% vs 20% (P=0.1199), respectively. For pts who previously received a bortezomib-containing regimen (DVd, n=162; Vd, n=164), PFS was also significantly longer with DVd vs Vd (median: 12.3 vs 6.7 months; HR, 0.46; 95% CI, 0.32-0.66; P<0.0001). Estimated 12-month PFS rates were 55% vs 27%, respectively. ORR was significantly higher with DVd vs Vd (80% vs 60%; P=0.0001), along with significantly higher rates of ≥VGPR (52% vs 22%; P<0.0001) and ≥CR (13% vs 3%; P=0.0019). Among pts who were refractory to lenalidomide at the last prior line of therapy (DVd, n=45; Vd, n=60), PFS was significantly longer in DVd vs Vd (median: 10.3 vs 4.4 mo; HR, 0.37; 95% CI, 0.21-0.65; P=0.0004; Figure). Within this subgroup, ORR was significantly higher for DVd vs Vd (81% vs 50%; P=0.0021), and the same trends were observed for rates of ≥VGPR (54% vs 12%; P<0.0001) and ≥CR (20% vs 5%; P=0.0261). Updated efficacy and safety data, including MRD analyses across different sensitivity thresholds (10-4, 10-5, and 10-6), will be presented at the meeting. Conclusions: These analyses confirm that addition of daratumumab to Vd significantly improves outcomes for RRMM pts regardless of prior treatment with bortezomib. Importantly, this treatment benefit of DVd vs Vd was maintained in pts who were refractory to lenalidomide at the last prior line of therapy. These data lend further support to adding daratumumab to a standard-of-care regimen in RRMM. Figure Progression-free Survival in Patients Refractory to Lenalidomide at the Last Prior Line of Therapy Figure. Progression-free Survival in Patients Refractory to Lenalidomide at the Last Prior Line of Therapy Disclosures Lentzsch: BMS: Consultancy; Foundation One: Consultancy; Celgene: Consultancy, Honoraria. Quach:Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen Cilag: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees. Ovilla:Janssen: Consultancy. Qi:Janssen: Employment. Deraedt:Janssen: Employment, Equity Ownership. Schecter:Janssen: Employment, Equity Ownership. Amin:Janssen: Employment. Qin:Janssen: Employment. Casneuf:Johnson & Johnson: Equity Ownership; Janssen R&D, Beerse, Belgium: Employment. Chiu:Janssen: Employment. Sasser:Johnson & Johnson: Equity Ownership; Janssen Pharmaceuticals R&D: Employment. Sonneveld:Karyopharm: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding.

Abstract Purpose: The burden of esophageal cancer continues to rise, and noninvasive screening tools are needed. Methylated DNA markers (MDM) assayed from plasma show promise in detection of other cancers. For esophageal cancer detection, we aimed to discover and validate MDMs in tissue, and determine their feasibility when assayed from plasma. Experimental Design: Whole-methylome sequencing was performed on DNA extracted from 37 tissues (28 EC; 9 normal esophagus) and 8 buffy coat samples. Top MDMs were validated by methylation specific PCR on tissue from 76 EC (41 adeno, 35 squamous cell) and 17 normal esophagus. Quantitative allele-specific real-time target and signal amplification was used to assay MDMs in plasma from 183 patients (85 EC, 98 controls). Recursive partitioning (rPART) identified MDM combinations predictive of esophageal cancer. Validation was performed in silico by bootstrapping. Results: From discovery, 23 candidate MDMs were selected for independent tissue validation; median area under the receiver operating curve (AUC) for individual MDMs was 0.93. Among 12 MDMs advanced to plasma testing, rPART modeling selected a 5 MDM panel (FER1L4, ZNF671, ST8SIA1, TBX15, ARHGEF4) which achieved an AUC of 0.93 (95% CI, 0.89–0.96) on best-fit and 0.81 (95% CI, 0.75–0.88) on cross-validation. At 91% specificity, the panel detected 74% of esophageal cancer overall, and 43%, 64%, 77%, and 92% of stages I, II, III, and IV, respectively. Discrimination was not affected by age, sex, smoking, or body mass index. Conclusions: Novel MDMs assayed from plasma detect esophageal cancer with moderate accuracy. Further optimization and clinical testing are warranted.

Abstract INTRODUCTION: Breast cancer is the most common invasive cancer and the second leading cause of cancer death in women. Approximately 20% of breast cancer tumors overexpress human epidermal growth factor receptor 2 (HER2), which is associated with an aggressive clinical phenotype and with a poorer prognosis. The development of trastuzumab, an immunoglobulin G monoclonal antibody directed against HER2, has changed the treatment paradigm for this disease. However, approximately 15-20% still does not respond to anti-HER2 therapy. Furthermore, despite advances in the management of metastatic HER2-positive breast cancer, response rate varies greatly, with most patients eventually succumbing to their disease. It is crucial to develop additional therapeutic strategies to improve outcomes for HER2 positive patients, especially those with tumors that do not respond to anti-HER2 therapy. METHODS and RESULTS: Using HER2+ breast cancer cell lines, we found that an USP7 inhibitor, P5091, dramatically sensitized cancer cells to HER2 inhibitor, trastuzumab treatment. To confirm it in vivo, we tested the drug combination in BT474 xenografts and found P5091 and trastuzumab synergistically suppressed tumor growth. Furthermore, using trastuzumab resistant HER2+ breast cancer cell line, we found that USP7 inhibitor, P5091, can dramatically re-sensitize trastuzumab-resistant BT474 cell line to trastuzumab treatment both in vitro and in vivo. More importantly, using patient derived xenograft (PDX) HER2+ models, we confirmed the synergistic combination effect of P5091 and trastuzumab. Mechanistically, USP7 inhibitor, P5091 led to significantly increased degradation of all four HER family members (HER1-4). When we knocked down USP7 by RNA interference or small hairpin RNA (shRNA), we observed similar substantial decrease in HER family member proteins. CONCLUSIONS: We have demonstrated the feasibility of using USP7 inhibitor P5091 to sensitize HER2+ breast cancers to trastuzumab treatment. These results provide a rationale for the use of combination therapy of USP7 inhibitors and HER2 inhibitors to treat HER2+ breast cancer. This combination therapy might also be effective in other cancers with upregulated HER signaling, such as GI cancer, lung cancer or ovarian cancer. Citation Format: Jia Yu, Bo Qin, Judy Boughey, Matthew Goetz, Liewei Wang. The role of USP7 and USP7 inhibitor in HER2+ breast cancer treatment [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 2980.

Abstract The present project was undertaken to determine whether the activation of the EGFR family (EGFR/ErbB2/ErbB3/ErbB4) and its downstream signaling effector ERK1/2 plays a role in enzalutamide resistance and whether treatment with ErbB or ERK inhibitors overcome this resistance. C4-2B (enzalutamide sensitive) and 22Rv1 (partially enzalutamide resistant) cell lines cultured for prolonged periods in enzalutamide, developed resistance to this drug (C4-2B/MDVR and 22Rv1/MDVR, respectively). Whole genome comparison of enza-resistant to parental lines demonstrated that the ErbB signaling network was significantly upregulated in the enza-resistant lines. Comparison of various enza-sensitive and resistant lines demonstrated a strong correlation between phosphorylation at EGFR(Y1068) and enza resistance. Inhibition of EGFR, but not that of ErbB2 or ErbB3 prevented cell viability. The EGFR inhibitors erlotinib and dacomitinib, but not the ErbB2 inhibitor lapatinib, suppressed viability in combination with enzalutamide. We hypothesized that enza-resistant tumors expressing higher levels of EGFR would be more responsive to erlotinib. To test this hypothesis, we compared the effects of erlotinib and enzalutamide, individually or in combination, in organelles from PDX tumors expressing high or low EGFR levels. Significantly, tumors expressing high EGFR, but not those expressing low EGFR, were responsive to the combination. Finally, we investigated the cause for greater efficacy with erlotinib compared to lapatinib in PCa. Comparison of the effects of different ligands revealed that while both lapatinib and erlotinib inhibited EGFR phosphorylation, only erlotinib but not lapatinib was able to inhibit EGF-induced ERK phosphorylation. This indicated an important role for ERK in the mediation of EGFR ligand induced enzalutamide resistance. Continuous culture of enza-sensitive C4 cells in enzalutamide resulted in the development of ERK phosphorylation in these PTEN-null cells that normally do not express phosphorylated ERK, and the newly ERK phosphorylated cells also were more susceptible to erlotinib as well. In support of a role for ERK in mediating the effects of EGFR activation in enza-resistant cells, inhibition of EGFR but not ErbB2 or ErbB3 inhibited ERK phosphorylation, and the ERK inhibitor ulitertinib inhibited viability of enza-resistant lines. We conclude that enzalutamide treatment causes an increase in EGFR ligands that result in the phosphorylation of EGFR at Y1068, which further resulted in phosphorylation of ERK. EGFR inhibitors that prevent ERK phosphorylation were effective in suppressing viability of enza-resistant CRPC cells, whereas ErbB2 inhibitors that did not affect ERK phosphorylation were unable to affect cell viability. These results demonstrate why certain ErbB inhibitors failed to affect enza-resistant CRPC tumors but provide encouragement for others. Citation Format: Thomas M. Steele, Maitreyee K. Jathal, Salma Siddiqui, Sisi Qin, Clifford G. Tepper, Ralph W. deVere White, Manish Kohli, Liewei Wang, Allen C. Gao, Paramita M. Ghosh. Overcoming EGFR and ERK-mediated resistance to enzalutamide in castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4842.

Abstract Background: In early stage, ERα-positive breast cancer, the concurrent use of endocrine therapy and chemotherapy has not been shown to be superior to sequential use. We hypothesized that genetic biomarkers can aid in selecting patients who would benefit from chemo-endocrine therapy. Our previous genome-wide association study (GWAS) and functional studies revealed that a single nucleotide polymorphism (SNP) in ZNF423, rs9940645, determines tamoxifen response. Specifically, 4-hydroxytamoxifen (4-OH-TAM) increases the gene expression of ZNF423, a transcription factor for BRCA1, in cells that are carry the rs9940645 variant, but not the wildtype, genotype. In this study, we set out to identify additional genes regulated by ZNF423, which, upon identifying a relationship between ZNF423 and cell cycle genes, led us to investigate taxane response in a SNP- and tamoxifen-dependent fashion. Method: Gene correlation analysis using The Cancer Genome Atlas (TCGA) breast cancer dataset was used to identify genes with expression correlated with that of ZNF423. Quantitative reverse transcription PCR, chromatin immunoprecipitation, and luciferase reporter assays were used to validate the gene associations. To test ZNF423 rs9940645-specific phenotypes, we used ZR75-1 cells, which are homozygous for the variant SNP, and ZR75-1 cells that were generated to be homozygous wild type (WT) using CRISPR-Cas9 technology, in addition to Hs578T breast cells with ERα overexpression (WT) and HCC1500 cells (variant). Cell cycle was assessed by propidium iodide staining. Cytotoxicity was assessed using a colorimetric assay. Results: Mitosis-related genes VRK1 and PBK, which encode histone H3 kinases, were experimentally validated to be regulated by ZNF423. Specifically, ZNF423 knockdown resulted in decreased VRK1 and PBK expression and activity. Additionally, ZNF423 knockdown resulted in enhanced docetaxel-induced G2/M arrest and cytotoxicity which could be rescued by VRK1 or PBK overexpression. Lastly, breast cancer cells carrying the rs9940645 variant SNP genotype had increased G2-M arrest and decreased cell viability when treated with docetaxel in combination with estradiol and 4-OH-TAM. Conclusion: We identified ZNF423regulated genes involved in the G2/M phase of the cell cycle. We found that 4-OH-TAM sensitized ERα-positive breast cancer cells to docetaxel treatment in a ZNF423 SNP-dependent manner. Our findings suggest that patients with rs9940645 variant genotype may benefit from concurrent tamoxifen endocrine therapy and docetaxel chemotherapy. This would impact a substantial proportion of patients given the minor allele frequency of 0.47 for this SNP. Citation Format: Gen Wang, Sisi QIN, Jacqueline Zayas, James N. Ingle, Mohan Liu, Richard Weinshilboum, Kunwei Shen, Liewei Wang. 4-Hydroxytamoxifen enhances sensitivity of estrogen receptor α-positive breast cancer to docetaxel in an estrogen and ZNF423 SNP-dependent fashion [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 2940.

Abstract Introduction The aim of this study was to investigate the rates of lobar atrophy in the asymptomatic microtubule‐associated protein tau ( MAPT ) mutation carriers. Methods MAPT mutation carriers (n = 14; 10 asymptomatic, 4 converters from asymptomatic to symptomatic) and noncarriers (n = 13) underwent structural magnetic resonance imaging and were followed annually with a median of 9.2 years. Longitudinal changes in lobar atrophy were analyzed using the tensor‐based morphometry with symmetric normalization algorithm. Results The rate of temporal lobe atrophy in asymptomatic MAPT mutation carriers was faster than that in noncarriers. Although the greatest rate of atrophy was observed in the temporal lobe in converters, they also had increased atrophy rates in the frontal and parietal lobes compared to noncarriers. Discussion Accelerated decline in temporal lobe volume occurs in asymptomatic MAPT mutation carriers followed by the frontal and parietal lobe in those who have become symptomatic. The findings have implications for monitoring the progression of neurodegeneration during clinical trials in asymptomatic MAPT mutation carriers.

ABSTRACT BACKGROUND AND PURPOSE The objective of this study was to longitudinally investigate the trajectory of change in 1 H MRS measurements in asymptomatic MAPT mutation carriers who became symptomatic during follow‐up, and to determine the time at which the neurochemical alterations accelerated during disease progression. METHODS We identified eight MAPT mutations carriers who transitioned from asymptomatic to symptomatic disease during follow‐up. All participants were longitudinally followed with an average of 7.75 years (range 4‐11 years) and underwent two or more single voxel 1 H MRS examinations from the posterior cingulate voxel, with a total of 60 examinations. The rate of longitudinal change for each metabolite was estimated using linear mixed models. A flex point model was used to estimate the flex time point of the change in slope. RESULTS The decrease in the NAA/mI ratio accelerated 2.09 years prior to symptom onset, and continued to decline. A similar trajectory was observed in the presumed glial marker mI/Cr ratio accelerating 1.86 years prior to symptom onset. CONCLUSIONS Our findings support the potential use of longitudinal 1 H MRS for monitoring the neurodegenerative progression in MAPT mutation carriers starting from the asymptomatic stage.