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Background: Immune thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal hematologic disorder characterized by thrombocytopenia, microangiopathic hemolytic anemia, and ischemic organ impairment. The incidence of iTTP is higher among African-Americans (AA), however, differences in presentation and outcomes have not been fully investigated. In a multi-center cohort of patients with iTTP from the United States Thrombotic Microangiopathy (USTMA) Consortium, we tested the hypothesis that AA race is an independent predictor of poor outcomes including iTTP related mortality and relapse. Methods: We queried data from the USTMA iTTP registry, which currently includes data from 785 individual patients from 15 institutions across the United States. Data from at least one iTTP episode are available for 734 patients. The cohort is 35.1% (N = 272) White, 58.7% (N = 455) African American, 0.4% (N=3) Asian, 1.8% (N=14) Hispanic, and 4.0 % (N=31) other/unknown race. We restricted our analyses to AA and White participants because of small numbers in the other groups. We compared presenting features and treatments using the chi-squared test and t-test for categorical and continuous variables, respectively. A relapse was defined as a recurrent iTTP episode occurring at least 30 days after last therapeutic plasma exchange. To evaluate relapse-free survival, we included only patients enrolled in the registry at their first TTP episode (144 White and 246 AA) since patients presenting with a relapse as their index episode are already confirmed to have relapsing iTTP. Kaplan Meier analysis was used to compare relapse-free survival in White and AA patients, and a Cox regression model was developed to evaluate the independent effect of race on relapse, adjusting for potential confounders including age, sex, and the use of rituximab. Results: Demographics and presenting features of 390 individuals (144 White and 246 AA) presenting with a first episode of iTTP are shown in Table 1. Presenting symptoms including fever, confusion, seizure, memory deficits, stupor, headache, stroke, chest pain, abdominal pain, fatigue, and dark urine were similar between Whites and AA except for petechiae, which were more frequently documented in Whites (28.8% vs 17.7%, p=0.011). Presenting laboratory studies were also comparable though AA had a higher rate of elevated serum troponin (50.6% vs 32.5%, p=0.003), lower hemoglobin level (8.27 ± 0.13 vs 8.81 ± 0.19, p=0.0176) and platelet count (20.3 ± 1.2 vs 26.2 ± 3.2, p=0.0432). In addition to therapeutic plasma exchange and corticosteroids, rituximab was administered to 23.7% of White patients and 22.7% of AA during their first iTTP episode (P=0.815). Median time to platelet count recovery (days of daily plasma exchange until normal platelet count for two consecutive days) was shorter in AA compared with White patients [5 (IQR 4, 10) vs. 8 (IQR 5, 14), log rank P = 0.004]. AA race remained a significant predictor of the shorter time to platelet count recovery [HR 1.44 (95% CI 1.12, 1.85), P=0.004] after adjusting for rituximab therapy [HR 0.60 (95% CI 0.0.46, 0.80), P<0.001], female sex [HR 0.95 (95% CI 0.73, 1.22), P=0.669], age [HR 0.99 (95% CI 0.99, 1.01), P=0.682], platelet count [HR 1.00 (95% CI 0.99, 1.04), P=0.820] and LDH at presentation [HR 1.00 (95% CI 1.00, 1.00), P=0.525]. Death during the first episode occurred in 8.9% of White patients and 5.5% of AA patients (P=0.206). Relapse-free survival after the first episode of iTTP was lower in AA than White patients (Figure 1). AA race was associated with the reduced relapse free survival [HR 1.79 (95% CI 1.08, 2.98), P=0.024] in a Cox regression model adjusted for age [HR 1.00 (95% CI 0.98, 1.01), P=0.683], sex [HR 0.96 (95% CI 0.60, 1.54), P=0.867], and rituximab therapy [HR 0.93 (95% CI 0.55, 1.59), P=0.806]. Conclusion: African Americans with iTTP have a higher relapse rate and shorter relapse free survival after the first episode of the disease compared with Caucasian patients, which is independent of age, sex and rituximab therapy. Contrary to our hypothesis, acute outcomes of iTTP (time to platelet count recovery and mortality) were not worse in AA patients. The factors contributing to the higher relapse rate in AA with iTTP need to be further investigated. Our findings suggest that AA patients may also benefit from closer follow up. Disclosures Farland: Sanofi: Membership on an entity's Board of Directors or advisory committees. Metjian:Sanofi: Membership on an entity's Board of Directors or advisory committees. Raval:Bayer, Inc: Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees. Liles:Shire: Other: PI on clinical trial Sickle cell ; Imara: Other: PI on Clinical trial- Sickle cell ; Novartis: Other: PI on clinical trial Sickle cell . Baumann Kreuziger:CSL Behring: Consultancy; Vaccine Injury Compensation Program: Consultancy. McCrae:Dova Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Pfizer Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Rigel Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Sanofi Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Zheng:Alexion: Speakers Bureau; Ablynx/Sanofi: Consultancy, Speakers Bureau; Clotsolution: Other: Co-Founder; Shire/Takeda: Research Funding. Cataland:Alexion: Consultancy, Research Funding; Ablynx/Sanofi: Consultancy, Research Funding. Chaturvedi:Shire/Takeda: Research Funding; Sanofi: Consultancy; Alexion: Consultancy.

Abstract Systemic immunosuppression following neurological insults including stroke, traumatic brain injury, and glioblastoma (GBM) causes mortality and leads to failure of immune-modulating therapies. Exact immunological nature and the underlying mechanisms of this immunosuppression are unknown. Our goal was to define effects of neurological insults given exclusively to the brain on the thymus. The thymus is the primary immune organ responsible for T-cell development and maintenance both in children and in adults. We evaluated the brain-thymus communication using the following neurological insults: physical injury, CNS viral infection, sterile injury, tumor implantation, and seizures. All insults resulted in significant thymic involution that was reversible upon clearance of the insult. Thymic involution did not occur following similar peripheral insults. We next demonstrated that the GL261 model of GBM recapitulates hallmark features of peripheral immunosuppression observed in GBM patients including low CD4 T-cell counts. Thus, we aimed to further study the immunosuppression affecting the thymus in this clinically relevant model. Principle component analysis following RNA-sequencing of thymi from naïve and glioma-bearing mice revealed unbiased separation of the groups suggesting that the thymus is directly affected by a brain tumor. To determine the extent to which thymic involution was caused by a soluble factor we employed parabiosis. We demonstrated that thymic involution was transferable from glioma-bearing to non-tumor-bearing parabionts. Similarly, serum taken from GL261 glioma-bearing mice potently inhibited proliferation of T-cells in vitro. Together our data demonstrate that CNS-specific insults, regardless of nature, cause immunosuppression by prompting thymic involution through circulating factors. This accounts at least partially for immune deficiencies observed following neurological injuries. Identification of this suppressive factor is crucial in designing future therapeutics for GBM patients, and patients with other acute and chronic neurological trauma.

Abstract Colorectal cancer (CRC) is the second leading cause of cancer death worldwide. Growing evidence supports gene fusions as good candidates for molecularly targeted therapy in CRC. Here we describe a case of a 63-year-old man who had a radical right hemicolectomy procedure 24 months ago. Pathological diagnosis indicated colorectal adenocarcinoma with stage pT4N2bMx. During re-examination in December 2016, positron emission tomography/computed tomography scans indicated relapse with multiple lymph nodes metastasis. Then the patient received a nine-cycle combination treatment of XELOX and bevacizumab and showed progressive disease (PD). Subsequently, the patient was treated with bevacizumab plus FOLFIRI for 2 months before discontinuation because of adverse events. Paraffin sections of postoperative colorectal tissue were subjected to next-generation sequencing, and epidermal growth factor receptor (EGFR) amplification and rare EGFR–SEPT14 fusion were identified. The patient then received erlotinib, an EGFR tyrosine kinase inhibitor (TKI), and achieved a partial response. However, the patient subsequently showed PD, and a new variant, EGFRvIII, appeared in metastasis, which may be involved in erlotinib resistance. We suggest that there is value in treating patients harboring EGFR fusions with EGFR TKI therapy, and EGFR–SEPT14 fusion may be used as a therapeutic target for CRC. Key Points To the authors' knowledge, this is the first report of EGFR–SEPT14 fusion in colorectal cancer. The patient achieved a partial response after treatment with the epidermal growth factor receptor tyrosine kinase inhibitor erlotinib. This report expands the list of gene fusions in colorectal cancer and highlights new targets for the therapeutic intervention. EGFRvIII may be involved in erlotinib resistance, which is rare in colorectal cancer.

Abstract The objective of the study was to assess racial disparities in the treatment and outcomes among white, African American, and Hispanic patients with multiple myeloma (MM). Patients with an MM diagnosis from the Surveillance Epidemiology and End Results (SEER)–Medicare (2007-2013) database were included. Continuous Medicare enrollment for 6 months before (baseline) and after MM diagnosis was required unless death occurred. Time from MM diagnosis to novel therapy initiation and autologous stem cell transplant (ASCT), overall survival (OS), and MM-specific survival (MSS) was evaluated. Unadjusted and multivariable regressions compared African Americans and Hispanics vs whites. Trends of novel therapy and ASCT use across MM diagnosis years were assessed using linear regression models. The study included 3504 whites, 858 African Americans, and 468 Hispanics. African Americans and Hispanics had a longer time from MM diagnosis to novel therapy initiation vs whites (median: 5.2 and 4.6 vs 2.7 months, respectively). All cohorts had an increasing trend of novel therapy initiation within 6 months of MM diagnosis, particularly whites (all P &lt; .05). Median MSS was significantly longer for African Americans (5.4 years) than whites (4.5 years; P &lt; .05), and was comparable for Hispanics and whites. Median OS was similar overall (2.6-2.8 years). ASCT rate within 1 year of MM diagnosis rose among whites and African Americans (P &lt; .05), but not Hispanics, who were less likely to receive ASCT vs whites. Significant variations in novel therapy and ASCT use were observed among different racial/ethnic groups with MM. Although OS was similar, both African Americans and Hispanics may not be fully benefitting from the introduction of novel therapies, as they receive them later than whites.

Abstract Background: The persistence of detectable MRD in complete remission (CR/CRi - CR with incomplete CBC recovery) has been reported to contribute to inferior outcome in younger AML patients (pts) in retrospective studies, however MRD has not been studied prospectively in older adults (age ≥60 yrs) receiving intensive therapy with curative intent. We performed a planned prospective study of MRD status after AML induction therapy in older adults, integrated into the large multicenter ECOG-ACRIN (E-A) E2906 Phase III trial. Methods Eligible patients age ≥60 yrs with AML were randomized 1:1 to receive either 'Standard' 7&3 (Dauno 60mg/m2) induction, with 2 cycles of intermediate dose Ara-C (1.5g/m2 x 12 doses; 6 doses if age ≥70) consolidation (Arm A); or single agent clofarabine (CLO) induction and consolidation (2 cycles) (Arm B). The design and primary clinical results for E2906 (n=727) have been reported previously (Foran et al, ASH #217a, 2015), demonstrating superior overall survival (OS) with standard therapy despite similar CR/CRi rates using stringent criteria, and similar 30-day induction mortality rates. Submission of diagnostic & remission bone marrow or peripheral blood samples was protocol mandated for prospective MRD assessment, and analysis was performed in the central E-A Leukemia Translational Research Lab (LTL) using 6-color multiparameter flow cytometry. MRD-positive (MRD+) was defined as ≥0.1%. LTL flow cytometric analysis was done blinded to treatment arm and outcome of patients. Only pt samples collected within +/-6 days of CR/CRi confirmation were included in this analysis. Statistical analysis was performed using X2 (categories) and Wilcoxon rank sum (continuous) tests to compare baseline patient and disease characteristics. Log-rank tests and multivariate Cox models stratified by treatment arm and adjusted for patient and disease variable (including WBC, cytogenetics, sex, performance status, secondary AML) were used to examine the MRD effect on OS and disease-free survival (DFS, relapse or death). Results The median follow-up is 47.8 months, and 297 of 685 evaluable patients (43.4%) achieved CR/CRi (Standard 44.6%; CLO 42.0%, p=ns). Remission MRD samples were only available for 147 CR/CRi patients (49.5%), owing to variability in sample viability and AML involvement, collection practices and timing of sample collection at individual sites, and patient/physician decision. 58/147 evaluable CR/CRi patients achieved MRD-negative (MRD-) status (Standard 40.7%, CLO 47.9%, p=0.74). Women (56.9% vs. men 43.1%, p=0.003) were more likely to be MRD-, but there was no other significant difference in MRD status stratified by clinical or disease features. MRD+ status at CR/CRi was associated with significantly inferior OS (p=0.031, Figure 1) and also inferior overall DFS (p=0.02); this was most pronounced for DFS after CLO (Arm B, Figure 2) (p=0.005), but not Standard (Arm A) therapy (p=0.41). The impact of MRD+ was confirmed on multivariate analysis using Cox Model Fitting, for OS: OS for All MRD+ pts, HR 1.64 (95% CI 1.00-2.68) (p=0.05); OS for Standard (Arm A) MRD+ pts, HR 1.06 (95% CI 0.51-2.21) (p=0.87); and OS for CLO (Arm B) MRD+ pts, HR 2.30 (95% CI 1.05-5.06) (p=0.04). There was a similar impact for DFS on multivariate analysis using Cox Model Fitting: DFS for All MRD+ pts, HR 1.86 (95% CI 1.16-2.98) (p=0.01); DFS for Standard (Arm A) MRD+ pts, HR 1.15 (95% CI 0.60-2.19) (p=0.67); and DFS for CLO (Arm B) MRD+ pts, HR 3.45 (95% CI 1.47-8.09) (p=0.004). Post-remission therapy was not stratified by MRD in E2906, and 33% of MRD-evaluable pts underwent allogeneic transplantation (no difference in transplant rate for MRD+ vs. MRD-). Conclusions MRD+ ≥0.1% is common (60.5%) after induction therapy in older adults & is significantly associated with inferior OS and DFS in 1st CR/CRi. However we observed excellent outcomes for MRD- pts in first CR/CRi regardless of induction regimen or post-remission therapy used. MRD+ pts in CR/CRi who went on to receive CLO consolidation had significantly poorer outcomes than those who went on to receive intermediate dose Ara-C consolidation. This observation differs strikingly from younger AML, and suggests that intensified Ara-C may abrogate the adverse impact of MRD in older pts in CR. These results strongly support incorporation of centralized MRD at the time of remission into future studies to guide optimal post-remission strategies in older pts with AML. Disclosures Foran: Agios: Research Funding; Xencor, Inc.: Research Funding. Lazarus:Pluristem Ltd.: Consultancy. Altman:Bayer: Other: payment to the institution to conduct clinical trial work; Pfizer: Other: payment to the institution to conduct clinical trial work; Boeringer Ingelheim: Other: payment to the institution to conduct clinical trial work; Epizyme: Other: payment to the institution to conduct clinical trial work; Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Immune Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Cyclacel: Other: payment to the institution to conduct clinical trial work; Incyte: Other: payment to the institution to conduct clinical trial work; GSK: Other: payment to the institution to conduct clinical trial work; Agios: Other: Payment to the institution to conduct the trial ; Astellas Pharma: Other; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: payment to the institution to conduct clinical trial work; BMS: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Ariad: Other: payment to the institution to conduct clinical trial work; FujiFilm: Other: payment to the institution to conduct clinical trial work; Genetech: Other: Payment to the institution to conduct clinical trial work; Celator: Other: payment to the institution to conduct clinical trial work. Al-Kali:Novartis: Research Funding. Pratz:Millenium/Takeda: Research Funding; Agios: Research Funding; AbbVie: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Boston Scientific: Consultancy. Powell:Rafael Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Tallman:ADC Therapeutics: Research Funding; BioSight: Other: Advisory board; Daiichi-Sankyo: Other: Advisory board; Orsenix: Other: Advisory board; AROG: Research Funding; AbbVie: Research Funding; Cellerant: Research Funding.

Abstract Background: There is limited data comparing the outcomes of the two most common (FM or FB) RIC regimens in AML. Previous smaller retrospective studies suggest increased non-relapse mortality (NRM) but decreased relapse with FM based RIC with a variable effect on overall survival as compared to FB. Methods: AML patients aged ≥18 years who had their 1st allo HCT using FM or FB (iv Bu only) RIC between 2001-2015 who had data reported to CIBMTR were studied. Patients with cord blood or identical twin donors, TBI as a part of conditioning, GVHD prophylaxis with T cell depletion/CD34 selection or post HCT Cyclophosphamide were excluded. Primary endpoint was overall survival (OS), and secondary endpoints included non-relapse mortality (NRM), relapse, leukemia free survival (LFS) and acute and chronic GVHD. Cox proportional hazards multivariable regression was used to compare the two RIC regimens while adjusting for significant patient, disease and transplant related factors. Major subgroup analysis included patients in CR pre-HCT. Results: 622 patients received FB and 791 had FM RIC. Median age of the FM group was 59 years, range (18 to 76) and median age of FB group was 61 years, range (18- 77). Compared to FB RIC regimen, FM group had more patients with active disease (36% vs 18%), with mismatched donors (24% vs 15%), with bone marrow grafts (19% vs 9%), HCT before 2005 (29% vs 12%) and without ATG/alemtuzumab (58 % vs 48%); but fewer patients in CR1 (46% vs 62%) and matched sibling donor grafts (21% vs 30%). There was significantly increased NRM in the FM vs FB within 3 mo post HCT (hazard ratio (HR)=3.85 (95% confidence intervals [CI] 2.46-6.03), but not beyond 3 mo FM vs FB , HR= 1.14 (95% CI 0.88-1.47). There was significantly decreased relapse for FM vs FB, (HR=0.65 (0.55-0.76), p<0.001) and a marginally superior LFS for FM vs FB, (HR=0.89 (95% CI 0.78-1.00), p=0.05). There was a lower OS FM vs FB within 3 mo post HCT (HR=1.82 (95% CI 1.36-2.45), p<0.001) but similar OS for FM vs FB beyond 3 mo post HCT (HR=0.87 (95% CI 0.76-1.00), p=0.05). Analysis restricted to only patients in CR pre-HCT showed similar results: equivalent survival, higher early NRM and lower relapse with FM. Conclusion: The current study of this large CIBMTR AML transplant cohort has showed that in these two most common RIC regimens for allogeneic HCT, long-term survival with FM was similar to FB. While the FM regimen showed higher early NRM, it was associated with lower risks of relapse. Further analysis to evaluate FB and FM regimens in relationship to comorbidities, comprehensive geriatric assessments, and presence of minimal residual disease is warranted to better define the relative efficacy of these two RIC regimens in AML. Disclosures Weisdorf: Pharmacyclics: Consultancy; Seattle Genetics: Consultancy; SL Behring: Consultancy; FATE: Consultancy; Equillium: Consultancy.

Abstract Background SAR650984 (SAR) is a naked humanized IgG1 monoclonal antibody (mAb) that binds selectively to the human surface antigen CD38 highly expressed in multiple myeloma cells and other hematological malignancies. SAR kills tumor cells via 3 different biological mechanisms: Antibody-dependent cellular-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC) and Induction of apoptosis (pro-apoptosis). Here we present preliminary data from the ongoing first in human, Phase I dose escalation study of SAR in patients with selected CD38+ hematological malignancies. (clinicaltrials.gov: NCT01084252) Objectives The primary objective is to determine the maximum tolerated dose (MTD). Secondary objectives include characterization of safety, pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity and disease response. Methods SAR is administered as a single agent IV infusion every week (QW) or every 2 weeks (Q2W) to adult patients with selected CD38+ hematological malignancies who have progressed on or after standard therapy or for whom no effective standard therapy exists. An accelerated dose escalation schedule was used for the first 5 dose levels (DL) (0.0001 mg/kg to 0.1 mg/kg Q2W), with one evaluable patient per DL unless DLT was experienced. All subsequent DL (0.3 mg/kg, 1 mg/kg, 3 mg/kg, 5mg/kg, 10 mg/kg, 20 mg/kg Q2W and 10 mg/kg QW), followed the classic 3+3 design for dose escalation based on DLT. Results 32 patients have been treated across all DLs including 3 patients with NHL, 2 with CLL, and 27 with MM. The 20 mg/kg Q2W and 10 mg/kg QW DLs are currently being evaluated and the MTD has not been reached. DLTs have been limited to Grade (G) 2 infusion reactions during cycle 1 with 1 at DL 0.3 mg/kg and 1 at DL 3.0 mg/kg. This was mitigated by the implementation of routine pretreatment with methylprednisone, diphenhydramine, ranitidine and acetaminophen. The most frequent occurring adverse events (≥ 10%) all DL, regardless of causality, are fatigue (46.9%), nausea (31.3%), pyrexia (28.1%), cough (25%), vomiting (21.9%), hypercalcemia (18.8%), with headache, constipation, bone pain, chills and diarrhea each occurring in 15.6% of patients. In addition, pneumonia, anemia, dysgeusia and hypokalemia each occurred in 12.5% of patients. Serious adverse events considered related to therapy include G 3 pneumonia (6.3%) associated with fever (3.1%), hyperglycemia (3.1%) and one Grade 2 infusion reaction (3.1%). Of the 19 patients treated at DL 1.0 mg/kg to 10 mg/kg Q2W, 1 had CLL, 1 had NHL and 17 had MM. The 17 MM patients were older and heavily pretreated patients; median age of 64 years (range: 55-74); and median of seven prior regimens (range: 2-14). All MM patients had received prior lenalidomide and bortezomib. The median time from diagnosis to first SAR650984 dosing was 6. 8 years (range 1.8 – 16.8 years). Responses in this group (fig 1), according to EBMT MM criteria, included 1 PR at 1 mg/kg (n = 3) and 5 mg/kg (n=3), and 1 MR at DL 3 mg/kg (n = 6). The 10 mg/kg DL demonstrated 3 PR and 2 SD among 6 MM patients treated. For the 19 patients treated at or above the 1 mg/kg DL the median time on treatment is 8 weeks (range 2-50 weeks). Immunogenicity studies show no anti-SAR antibodies. Receptor Occupancy could be detected from DL 1 mg/kg and reached a range of 84.1 to 97.7 % at 10 mg/kg. PK analysis show a more than dose proportional increase of exposure over the 0.03 to 10 mg/kg dose range with clearance in a similar range between 5 mg/kg and 10 mg/kg. No accumulation was observed based on Cmax at cycle 2 over the 0.03 to 3 mg/kg dose range. Tumor growth inhibition threshold was reached at Cmax for 1 patient at DL 5 mg/kg and 5 patients at DL 10 mg/kg. Conclusion The safety profile of SAR is predictable and manageable and the MTD has not been reached. SAR demonstrates encouraging single agent activity in patients with heavily pretreated RRMM and warrants further evaluation in this patient population. Disclosures: Zheng: sanofi: Employment. Daskalakis:sanofi: Employment.

Abstract Abstract 3836 Poster Board III-772 Antibody-drug conjugates (ADCs), potent cytotoxic drugs linked to antibodies via specialized chemical linkers, provide a means to increase the effectiveness of chemotherapy by targeting the drug to neoplastic cells while reducing side effects. Target selection is a key component to the success of an ADC. In addition to expression on the tumor, the target should have limited expression on normal tissues. The most prevalent and best-studied surface antigens on multiple myeloma (MM) cells, CD138, CD38, CD72, and CD56, all have relatively broad expression patterns that may lead to target-dependent toxicities with ADCs. We have previously shown that FcRL5/FcRH5/IRTA2 is expressed only on B-cells and plasma cells. Here we show that FcRL5 is expressed on the surface of MM cells from 85% of patients and thus could be a target for antibody and ADC treatments of MM. As experience in humans with anti-CD20 antibodies suggests that depletion of B-cells does not present a major safety issue, FcRL5 appears to have an excellent expression pattern as an ADC target for MM. Internalization of target antigens is known to increase the efficacy of ADCs and we found that FcRL5 is internalized upon antibody binding, an ideal trait. We made two different ADCs consisting of anti-FcRL5 antibodies 1) conjugated through cysteines to monomethylauristatin E (MMAE) by a maleimidocaproyl-valine-citrulline-p-aminobenzyloxycarbonyl (MC-vcPAB) linker that is designed to be cleaved by cathepsins (Anti-FcRL5-MC-vcPAB-MMAE); and 2) conjugated via lysines to the maytansinoid DM4 through a disulified linker designed to be cleaved by reducing conditions (anti-FcRL5-SPDB-DM4). These ADCs were tested for cell killing in vitro and in xenograft studies using OPM2 cells stably expressing FcRL5. While unconjugated anti-FcRH5 and control ADCs were not effective, anti-FcRL5-MC-vcPAB-MMAE and anti-FcRL5-SPDB-DM4 were effective at killing this MM cell line both in vitro and in vivo. Furthermore, the anti-FcRL5-SPDB-DM4 conjugate was effective in a SCID-rabbit bone model of MM using the LD cell line. These data suggest that FcRL5 ADCs could be an effective treatment for MM. Disclosures: Polson: Genentech, Inc.: Employment, Equity Ownership. Zheng:Genentech, Inc.: Employment, Equity Ownership. Elkins:Genentech, Inc.: Employment, Equity Ownership. Lau:Genentech, Inc.: Employment, Equity Ownership. Go:Genentech, Inc.: Employment, Equity Ownership. Scales:Genentech, Inc.: Employment, Equity Ownership. Yu:Genentech, Inc.: Employment, Equity Ownership. Chesi:Genentech, Inc.: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Merck: Research Funding. Bergsagel:Genentech, Inc.: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Merck: Research Funding. Ebens:Genentech, Inc.: Employment, Equity Ownership, Patents & Royalties.

Abstract Background: Retinoblastoma (RB) is the most frequent pediatric retinal tumor. In the present study, to elucidate chemoresistance mechanisms and identify potential biomarkers in RB, we utilized RNA sequencing (RNAseq) technological platforms to reveal transcriptome profiles and identify any differentially expressed genes (DEGs) between an etoposide drug-resistant subline (Y79/EDR) and parental Y79 cells. Methods: To test whether Y79/EDR cells showed resistance to antineoplastic agents for RB, we treated the cells with etoposide, carboplatin and vincristine and analyzed them with a Cell Counting Kit-8 (CCK-8). Y79/EDR and parental Y79 cells were used for RNAseq and bioinformatics analysis to enable a genome-wide review of DEGs between the two lines using the DESeq R package (1.10.1). Then, DEG enrichment in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways was analyzed with KOBAS software. Next, real-time quantitative reverse transcription polymerase chain reaction (real time QRT-PCR) and cytotoxicity assays were performed to experimentally and functionally validate the identified candidate biomarkers. Results: Y79/EDR cells showed resistance to etoposide, carboplatin and vincristine at different concentrations. In total, 524 transcripts were differentially expressed in Y79/EDR cells based on analysis of fragments per kilobase of transcript per million fragments mapped (FPKM); among these, 57 genes were downregulated and 467 genes were upregulated in Y79/EDR cells compared to parental Y79 cells. We selected candidate DEGs, including ARHGAP9 , HIST1H4H , RELN , DDIT4 , HK2 , STC1 and PFKFB4, for mRNA expression validation with real time QRT-PCR assays and found that the expression levels determined by real time QRT-PCR were consistent with the RNAseq data. Further studies involving downregulation of ARHGAP9 with a specific siRNA showed that ARHGAP9 altered the cellular sensitivity of Y79 cells to etoposide and carboplatin. Conclusion: Our initial findings provided a genomic view of the transcription profiles of etoposide-induced acquired resistance in RB. Follow-up studies indicated that ARHGAP9 might be a chemoresistance biomarker in RB, providing insight into potential therapeutic targets for overcoming acquired chemoresistance in RB. These findings can aid in understanding and overcoming chemoresistance during treatment of RB in the clinic.

Abstract Background: Induction therapy with daunorubicin (Dauno) & cytarabine (Ara-C) [DA] has been the standard of care for eligible older adults (age ≥ 60 years) with newly diagnosed acute myeloid leukemia (AML) for over 2 decades. Single agent Clofarabine (CLO) induction & consolidation (Consol.) therapy has demonstrated important clinical activity in this age group in large phase II studies. Lower induction mortality (IM) & similar reported complete remission rate (CR) & overall survival (OS), as well as notable activity in those with higher risk disease features [including unfavorable cytogenetics, therapy-related AML (t-AML) & prior antecedent hematologic disorder (AHD)] raises the possibility that a non-Ara-C-based regimen could achieve similar or superior OS with lower toxicity. Methods: We performed a randomized United States Intergroup Phase III trial of single agent CLO [30mg/m2 x 5 days induction; 20 mg/m2 re-induction (if indicated) & 2 cycles Consol.] vs. standard DA therapy [Dauno 60mg/m2 D1-3 & Ara-C 100mg/m2 D1-7 induction x 1-2 cycles; 2 cycles Consol. with Ara-C (1.5g/m2 Q12hrs D1-6 age 60-69; once daily if age 70+)] in patients (pts) age ≥ 60 yrs with newly diagnosed AML. Patients with serum creatinine >1.0 (or GFR <60 mL/min) and those with AML-M3 and ECOG performance status >3 (PS>2 if age 70+ yrs) were excluded. Randomization was stratified by age (60-69 vs. 70+), t-AML, & AHD. Pts with HLA-matched donor were eligible for allogeneic transplantation (AlloHCT) after induction, and those completing Consol. were eligible for randomization #2 (R#2) to maintenance decitabine [20mg/m2 x 3D, monthly x 1 year] versus observation. With a target accrual of 747, E2906 was powered to determine non-inferiority [and possible superiority] of CLO vs. standard DA, and primary endpoint was OS. A weighted statistical analysis was performed to account for confounding impact of R#2. AlloHCT patients were censored at transplant in this analysis. Responses & cytogenetics were confirmed centrally and OS & CR rates were monitored by an independent Data Safety Monitoring Committee (DSMC) at pre-specified time points. Results: As of Feb 23, 2015, 727 pts were randomized. Median age was 68 years (range 60-86); 57% were male, and 38% were age ≥70 yrs. Treatment arms are well balanced for all baselineclinical & AML characteristics, & 30% had unfavorable cytogenetics. Of 659 with complete treatment information reported, 30.4% on DA vs. 40.1% on CLO received 2 cycles of induction (p=0.006). Median follow-up of surviving patients is 7.6 months. Table 1. shows early treatment results (CR, toxicity) for the 686 pts randomized as of Dec 23, 2014 (2 months prior to study end, & excluding 90 with ongoing response evaluation). DA CLO p-value CR/CRi 43.8% 42.8% p=0.87 30-day mortality 8.5% 7.9% p=0.89 60-day mortality 14.9% 13.1% p=0.58 Gr 4-5 Non-Heme Tox.Induction 27% 19% p=0.02 Gr 4-5 Non-Heme Tox.Consol. 20% 7% p=0.001 374 pts have died (174, DA; 200, CLO) & significantly inferior OS was observed for CLO vs. DA [Hazard Ratio (HR) 1.41 (95% CI 1.12-1.78)] (Fig. 1). Planned subgroup analyses were performed (Table 2) demonstrating significant differences in OS after CLO for patients age 60-69 yrs, without AHD, & with intermediate risk cytogenetics; but not for those with Unfav. Cytogen. (Fig. 2) or t-AML. Based on the primary weighted analysis, DSMC recommended suspension of new accrual to E2906 on Feb 23, 2015 & all active patients on CLO were transitioned to DA Arm. Table 2.NHR CLO/Standard (95% CI)*Weighted OS7271.41 (1.12-1.78)Unweighted OS7271.23 (1.00-1.50)Age 60-694491.48 (1.10-1.99)Age 70+2781.34 (0.93-1.93)Intermed. Risk Cytogen.3781.77 (1.27-2.47)Unfav. Risk Cytogen.2160.96 (0.65-1.43)No AHD6041.46 (1.13-1.89)AHD1231.22 (0.74-2.00)De novo AML6271.52 (1.18-1.96)Therapy-related AML1000.94 (0.54-1.61) Conclusions: Despite similar CR & IM, OS after single agent CLO is inferior to standard DA therapy for pts age ≥60 years with newly diagnosed AML who are fit for intensive therapy, and DA remains the standard of care. However no difference in OS was observed after CLO in some pre-specified high risk AML subgroups. R#2 & AlloHCT arms continue in E2906 for pts already enrolled. Embedded prospective minimal residual disease study at CR is being performed to identify pts at higher risk after CLO & DA. Figure 1. Weighted Kaplan-Meier Curves for OS Figure 1. Weighted Kaplan-Meier Curves for OS Figure 2. Unfavorable Cytogenetics OS by Therapy Figure 2. Unfavorable Cytogenetics OS by Therapy Disclosures Off Label Use: Use of clofarabine in AML, and maintenance therapy with decitabine in AML. Claxton:Medimmune: Research Funding; BMS: Consultancy; Astellas: Research Funding; Cyclacel: Research Funding; Merck: Research Funding; Ambit: Research Funding. Levine:Loxo Oncology: Membership on an entity's Board of Directors or advisory committees; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Foundation Medicine: Consultancy. Altman:Seattle Genetics: Consultancy; BMS: Consultancy; Spectrum: Consultancy; Astellas: Consultancy; Ariad: Consultancy; Novartis: Consultancy. Al-Kali:Novartis: Research Funding.