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Mantle cell lymphoma (MCL) is an uncommon B-cell non-Hodgkin lymphoma (NHL) that is incurable with standard therapies. The genetic drivers of this cancer have not been firmly established, and the features that contribute to differences in clinical course remain limited. To extend our understanding of the biological pathways involved in this malignancy, we performed a large-scale genomic analysis of MCL using data from 51 exomes and 34 genomes alongside previously published exome cohorts. To confirm our findings, we resequenced the genes identified in the exome cohort in 191 MCL tumors, each having clinical follow-up data. We confirmed the prognostic association of TP53 and NOTCH1 mutations. Our sequencing revealed novel recurrent noncoding mutations surrounding a single exon of the HNRNPH1gene. In RNA-seq data from 103 of these cases, MCL tumors with these mutations had a distinct imbalance of HNRNPH1 isoforms. This altered splicing of HNRNPH1 was associated with inferior outcomes in MCL and showed a significant increase in protein expression by immunohistochemistry. We describe a functional role for these recurrent noncoding mutations in disrupting an autoregulatory feedback mechanism, thereby deregulating HNRNPH1 protein expression. Taken together, these data strongly imply a role for aberrant regulation of messenger RNA processing in MCL pathobiology.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induced coronavirus disease-2019 (COVID-19) has presented humanity with unprecedented challenges. Severe disease is associated with acute respiratory distress syndrome (ARDS), use of mechanical ventilation, ICU stay and prolonged hospitalization, The role of the immune system in the pathogenesis of COVID-19 disease is still unclear, which imposes limitations on identifying potential immunotherapy that can improve care for acute and chronic phases of COVID-19 in conjunction with current therapies. Research efforts are ongoing for more than 1 year to identify key immunological mechanisms involved in the disease process. While insightful, this knowledge is still incomplete and can be complemented with the assessment of immune response kinetics. Such assessment will help with the identification of early interventional modalities of immune cell regulation. With these considerations in mind, we aimed to assess several parameters of immune system regulation during the current medical care of patients with COVID-19. Methods: This is a pre-clinical prospective cohort study which involved laboratory-based assessments of blood samples obtained from COVID-19 patients and healthy volunteers. The study population was divided into three cohorts. Our first cohort included 18 years and older COVID-19 patients with respiratory complaints, oxygen (O2) saturations of less than or equal to 92 and pulmonary infiltrates on an imaging study or who were critically ill and required ventilatory support. Second cohort included 18 years and older COVID-19 patients who were hospitalized and did not require ventilatory support. Third cohort included participants with no prior diagnosis of COVID-19, or any recent viral respiratory symptoms including fever, cough or shortness of breath for the last 2 weeks. Patients with an established diagnosis of cancer or immunologic disorders were excluded. Blood specimens were collected over the period of hospitalization: specimen number 1 on day 1-3 of hospitalization, specimen number 2 on days 3-4 of hospitalization, specimen number 3 on days 5-7 of hospitalization, and specimen number 4 on 7-30 days after discharge. We performed capillary electrophoresis for serology and automated ELISA for cytokine measurement. We collected clinical data on patient demographic, clinical characteristics such as presence of any acute and chronic comorbidities and serum inflammatory markers C-Reactive Protein, D-Dimer and Ferritin. Results: We had 15 patients in cohort 1, 10 in cohort 2 and 15 in cohort 3. Patients in cohort 1 were older and had higher comorbidities. Males constituted a substantially high percentage of patients in cohort 1 and 2 (60% and 70% respectively). Patients had similar BMI in cohort 1 and 2. Total antibody levels were highest in cohort 1 but an upward trend over the course of hospitalization was noted in all cohorts. Most interesting pattern was noted in the context of antibodies against spike protein S1 receptor-binding domain (S1RBD) where patients in cohort 2 developed minimal S1RBD antibodies. Cohort 1 on average had higher levels of Interleukin 6(IL-6), Interleukin 8(IL-8), C-X-C motif chemokine ligand 10 (CXCL10) and other inflammatory cytokines except Interferon gamma (IFN-gamma) compared to Cohort 2. Remarkable difference in CXCL-10 levels was noted between the groups and healthy volunteers had the lowest levels. No significant difference in IFN-gamma was noted between cohorts and the levels quickly depleted over the course of the infection. Conclusion: Our analysis confirms that neutralizing antibodies do not correlate with lessened COVID-19 disease severity. Severe COVID-19 infection is secondary to ineffective innate immunity associated with immune overshoot. CXCL10 serves as a major component in triggering the cytokine storm that is a hallmark of SARS-CoV-2 infections. Our findings show an association between high levels of CXCL10 and more severe COVID-19 infection. There does not seem to be any significant correlation with disease severity and IFN-gamma levels. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Introduction: Genome- and transcriptome-wide analyses continue to enhance our understanding of the molecular pathogenesis of cancer. In lymphomas, this has enabled the identification of hundreds of recurrently mutated genes, highlighting genetic heterogeneity and relationships both within and among clinical entities. While the growing availability of lymphoma genomic data sets can be leveraged to integrate genomic analyses into diagnostic testing and clinical trials, the ability to rapidly process genomic data sets in a reproducible manner serves as a barrier to this goal. To this end, we developed a suite of tools Lymphoid Cancer Research modules (LCR-modules) to facilitate the discovery of novel drivers and molecular features in lymphoma cancers and perform quantitative comparisons between disease entities. We demonstrate here how this toolkit enabled a meta-analysis of lymphoma genomic data involving genome-wide profiles of 3330 patients. Methods: We assembled a collection of whole genome, whole exome, and RNA sequencing data from a combination of controlled-access repositories and ongoing projects at BC Cancer. The scope of genomic analysis of mature B-cell lymphomas (GAMBL) project includes cell lines and patient tumors from all common mature B cell neoplasms, comprising a total of 4612 samples from 3330 patients. To facilitate the project, we developed a suite of open-source and custom bioinformatics tools (https://github.com/LCR-BCCRC/lcr-modules) that leverages the Snakemake workflow management system and includes lymphoma-centric modules for the discovery and annotation of common mutation types, analysis of B-cell receptor repertoires and discovery of novel aSHM targets and relevant non-coding mutations, and RNA-seq analysis with batch correction and normalization. Individual modules are configured to create an automated, scalable, and reproducible workflow that runs each step as dictated by the availability of new data. The cohort-level integrative analysis and comparisons across entities are handled by our custom R package GAMBLR, which facilitates open-ended data analysis and custom visualizations. Results: Simple somatic mutations (SSM) were detected using a workflow that utilizes four algorithms to identify high-confidence variants with validated default thresholds for filtering of germline variants and common FFPE-associated artifacts, allowing for processing of samples without matched normal tissue. This automated and reproducible workflow facilitated the discovery of novel genes significantly mutated across lymphomas and broadened our understanding of the scope of aberrant somatic hypermutation (aSHM) and other non-coding mutations. Specifically, HNRNPU, STAT3, TFAP4, RRAGC were found to be mutated at relatively low frequencies, and their presence is a distinct feature of certain lymphomas or novel genetic subgroups within lymphoma types (Figure 1A). The aSHM analysis and discovery of novel hypermutated regions is handled by a custom tool Rainstorm. As a result, we were able to detect sites preferentially hypermutated in a single entity, such as the transcription start site of BACH2, mutated at lower rates than the other common target sites but significantly more in BL compared to other entities (Figure 1B). Combining aSHM at target sites discovered using our toolkit with other genetic features allowed us to explore and establish novel genetic subgroups within Burkitt lymphoma and follicular lymphoma. SV analysis can be conducted using Manta, GRIDSS, and JaBbA modules with downstream processing in GAMBLR. In B-cell lymphomas, the most common SVs identified using the automated workflow were targeting MYC, BCL2, and CCND1. Unsurprisingly, the most common translocation partner among B-cell lymphomas was the immunoglobulin heavy chain, but the novel BCL6-FOXP1, CD274-BACH2, BCL6-RHOH translocations in DLBCLs and MYC-BCL6 translocations in BLs were identified, among others (Figure 1C). Conclusions: We present here the modularized workflow for scalable and automated analysis of genomic and transcriptomic data and demonstrate that it can be successfully deployed across thousands of tumour samples for the discovery of known and novel lymphoma biology. This represents an important advancement in reproducibility that will facilitate clinical translation of genomic discoveries. Figure 1 Figure 1. Disclosures Grande: Sage Bionetworks: Current Employment. Coyle: Allakos, Inc.: Consultancy. Steidl: AbbVie: Consultancy; Trillium Therapeutics: Research Funding; Epizyme: Research Funding; Seattle Genetics: Consultancy; Curis Inc.: Consultancy; Bayer: Consultancy; Bristol-Myers Squibb: Research Funding. Scott: Abbvie: Consultancy; NanoString Technologies: Patents & Royalties: Patent describing measuring the proliferation signature in MCL using gene expression profiling.; Celgene: Consultancy; AstraZeneca: Consultancy; Incyte: Consultancy; Janssen: Consultancy, Research Funding; Rich/Genentech: Research Funding; BC Cancer: Patents & Royalties: Patent describing assigning DLBCL COO by gene expression profiling--licensed to NanoString Technologies. Patent describing measuring the proliferation signature in MCL using gene expression profiling. . Morin: Epizyme: Patents & Royalties; Celgene: Consultancy; Foundation for Burkitt Lymphoma Research: Membership on an entity's Board of Directors or advisory committees.

Introduction: Follicular lymphoma (FL) is an indolent disease that undergoes histological transformation (HT) to aggressive diffuse large B-cell lymphoma (DLBCL) in 8-15% of patients. FLs frequently share genetic features with DLBCL, especially those of the germinal center B-cell-like (GCB) cell-of-origin (COO) and the EZB/C3 genetic subgroup, and approximately 80% of transformed FL (tFL) are classified as GCB. Our current understanding of the genetics of FL and tFL is based on a variety of studies, most of which have sequenced tumors in small case numbers or using targeted approaches such that the potential role of non-coding mutations and aberrant somatic hypermutation (aSHM) in predicting HT have not previously been fully explored. Methods: Whole genome sequencing (WGS) data from 212 FL (including 24 from patients that subsequently underwent HT) and 241 de novo DLBCL were analyzed. Simple somatic mutations (SSMs) were called using an ensemble of somatic variant callers, while structural variants (SVs) were called with Manta and copy number variants (CNVs) with Battenberg and GISTIC. Fluorescence in situ hybridization with break-apart probes (BA-FISH) was used to identify MYC, BCL2, and BCL6 translocations, and with IGH /BCL2 dual-fusion probes (DF-FISH) for a subset of FLs. To compare the genetics of FL and DLBCL, 83 significantly mutated genes (SMGs) were identified with dNdS, MutSigCV, HotMaps, and OncoDriveFML, and non-silent mutations were tabulated for their presence in each genome. For 38 hypermutated regions, we used a region-specific threshold to binarize the data to aSHM/no aSHM. Recurrent missense mutations in FOXO1, MYD88L265P, CREBBP lysine acetyltransferase (KAT) domain, EZH2Y646, MEF2B, and STAT6 were tabulated separately from other mutations in these genes. Using only the FL tumors from patients with no evidence of subsequent transformation and all available de novo DLBCLs, we trained a random forest classifier to separate these two entities using this set of 129 features, including MYC and BCL6 translocations. To validate this classifier, we fit a linear model to the number of FL votes from each discovery case, utilizing the 65 features (including 19 aSHM features) that were adequately sequenced in a validation cohort of 127 tFL. Statistical tests were corrected for multiple comparisons where necessary. Results: This large cohort of FL and DLBCL genomes has enabled the curation of an extensive list of novel and established FL driver genes and the identification of distinguishing genetic features among SMGs and CNVs. Loci that are significantly enriched for mutations in FL vs. DLBCL include the CREBBP KAT domain (OR 11.5, P < 0.0001), RRAGC (OR 9.61, P < 0.001), and ATP6V1B2 (OR 11.17, P < 0.001). Deletions of ARID1A (OR 4.74, P < 0.1), PTEN (OR 3.65, P < 0.01), and TNFRSF14 (OR 3.31, P < 0.01) were among the CNVs significantly enriched in FL. Out of 156 FLs, 24 (15%) were negative for BCL2 translocations by BA-FISH, but 4 (17%) of these had BCL2 translocations detected from WGS data. All 4 of these cryptic events were confirmed using IGH /BCL2 DF-FISH. Using a threshold of 0.7, the linear model separated discovery FL cases into a more DLBCL-like subgroup, termed dFL (n = 107), and a genetically homogeneous subgroup enriched for the FL-associated features, which we describe as constrained FL (cFL, n = 105). This separation is supported by more mutations in dFL vs cFL across several aSHM loci, including the transcription start sites for BCL6, BCL7A, DTX1, and ZFP36L1 (Figure 1), consistent with reduced exposure to the germinal center reaction in cFL. Within the targeted capture validation cohort of tFL, 30 (24%) tumors were classified as cFL and 97 (76%) as dFL. The tFL cohort was significantly depleted for mutations in the CREBBP KAT domain (OR 0.59, P < 0.05), and were significantly less frequently classified as cFL (OR 0.30, P < 0.0001) compared to the discovery FLs. Conclusions: The distinction between cFL and dFL is strongly driven by CREBBP KAT domain mutations and different rates of aSHM genome wide. Given the known early clonal nature of CREBBP mutations in FL and its role in regulating germinal center cycling, we speculate that CREBBP KAT mutations may limit the exposure of FL to the dark zone, reducing the opportunity for aSHM and creating an evolutionary constraint that may limit the opportunity for HT. This classification may serve as a useful biomarker to identify FLs at higher risk of HT. Figure 1 Figure 1. Disclosures Coyle: Allakos, Inc.: Consultancy. Grande: Sage Bionetworks: Current Employment. Slack: Seagen: Consultancy, Honoraria. Steidl: Curis Inc.: Consultancy; Trillium Therapeutics: Research Funding; Epizyme: Research Funding; Bayer: Consultancy; Seattle Genetics: Consultancy; AbbVie: Consultancy; Bristol-Myers Squibb: Research Funding. Scott: Janssen: Consultancy, Research Funding; Abbvie: Consultancy; AstraZeneca: Consultancy; NanoString Technologies: Patents & Royalties: Patent describing measuring the proliferation signature in MCL using gene expression profiling.; Incyte: Consultancy; Rich/Genentech: Research Funding; Celgene: Consultancy; BC Cancer: Patents & Royalties: Patent describing assigning DLBCL COO by gene expression profiling--licensed to NanoString Technologies. Patent describing measuring the proliferation signature in MCL using gene expression profiling. . Morin: Epizyme: Patents & Royalties; Foundation for Burkitt Lymphoma Research: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy.

Introduction Animal models of human cancers are an important tool for the development and preclinical evaluation of new treatments. Canine B-cell lymphoma (cBCL) is an appealing alternative to murine preclinical models due to its frequent, spontaneous incidence and its clinical and histological similarity to human B-cell non-Hodgkin lymphoma (NHL). The potential utility of cBCL as a veterinary model of human B-cell lymphomas would be bolstered by a more complete understanding of the genetic features found in cBCL. Methods To study the genetics of cBCL, we obtained fresh frozen and matched plasma/serum from 86 patients from the Canine Comparative Oncology Genomic Consortium(CCOGC) with 65 confirmed as B-cell lymphomas by immunophenotyping. Tumor DNA was prepared into libraries using the QIAseq FX DNA Library Kit (Qiagen). Plasma and serum DNA was prepared into libraries using the NebNext Ultra II DNA Library Prep Kit. Targeted hybridization enrichment was performed on the libraries using our custom baits and sequencing reads were aligned to canFam3.1 using Geneious and each mutation was visually confirmed. Variants were annotated with Variant Effect Predictor and human-dog pairwise alignments were extracted from Ensembl to identify the orthologous human amino acid for all canine variants. Results Our analysis confirmed the previously reported high frequency of mutations in TRAF3 and FBXW7. We also observed mutations in POT1, TP53, and SETD2 at similar frequencies to those reported in previous studies. DDX3X was mutated in 20% of cases, which is substantially higher than previously reported. MYC mutations were also more frequent (13%) than has been previously described in cBCL. In human lymphomas, MYC is commonly deregulated by translocation to a potent enhancer and these events are often associated with point mutations in MYC that are induced by aberrant somatic hypermutation (aSHM). Interestingly, we identified a more focal pattern of MYC mutations in cBCL that implies they do not result from aSHM and are likely functional. This finding implicates the conserved MYC phosphodegron sequence, a motif commonly mutated among additional aSHM-associated mutations, as the target of bona fide driver mutations in both human and cBCLs. Mutations in FBXW7 primarily affected the substrate recognition domain responsible for MYC degradation. The observation that MYC and FBXW7 mutations did not co-occur in any canine patient is consistent with the notion that FBXW7 mutations operate as an alternative path to MYC stabilization which is not frequently observed in human NHL. DDX3X was one of the most frequently mutated genes in our cohort (20%). DDX3X mutations are common in human Burkitt lymphoma and, though less abundant in hDLBCL, tend to be observed in samples with MYC translocations. In Burkitt lymphoma, these mutations display a sex-specific pattern, wherein females show mainly missense mutations, while males are affected by loss-of-function mutations. Interestingly, all DDX3X mutations in cBCL are missense variants and are presumed to be dominant acting. This lack of sex difference in DDX3X mutations is an important distinction between human and canine B-cell lymphomas that warrants further exploration. Conclusions Our study has revealed key differences in the mutational profiles of canine and human B-cell lymphomas and provides an impetus for enhanced genomic characterization of canine lymphomas as a model for human NHL, particularly in clinical trial settings. Disclosures Grande: Sage Bionetworks: Current Employment. Alcaide: GA Diagnostics AB: Current Employment. Morin: Celgene: Consultancy; Foundation for Burkitt Lymphoma Research: Membership on an entity's Board of Directors or advisory committees; Epizyme: Patents & Royalties. Coyle: Allakos, Inc.: Consultancy.

Background. Platelet transfusion is a critical therapy for hematology-oncology patients at risk of transfusion-transmitted infection (TTI) and pulmonary injury. Amotosalen-UVA pathogen reduction (PR) treatment of apheresis platelet components (PC) in plasma or additive solution (INTERCEPT Blood System for Platelets, Cerus, Concord, CA) is FDA approved to reduce risk of TTI and transfusion associated graft vs. host disease (TA-GVHD). PRPC meet the FDA bacteria risk reduction guidance, and approximately 50% of U.S. PC are PRPC. Amotosalen-UVA PR replaces bacteria screening, gamma irradiation, and CMV serology. PR is performed within 24 hours of collection enabling early release of PRPC with 5-day storage. We tested the hypothesis that PRPC were not inferior to conventional PC(CPC) for the incidence of pulmonary injury. Methods. An open-label sequential cohort study in platelet transfusion dependent hematology-oncology patients was conducted under routine practice conditions in 15 clinical centers. Each site enrolled a CPC cohort followed by a PRPC cohort using 4 primary therapy strata matched ± 10%: chemotherapy without hematopoietic cell transplant (HCT), HCT with myeloablation, HCT with non-myeloablative conditioning, and HCT with reduced intensity conditioning (RIC). Patients were supported with the assigned PC type for up to 21 days with 7 days of surveillance after the last PC exposure. Patients participated in only one cohort. The primary endpoint was treatment emergent assisted mechanical ventilation (TEAMV) by intubation or tight mask with positive end expiration pressure (5cm H 2O) after initiation of study PC. All endpoint patients were adjudicated by a blinded pulmonary expert panel (PEP) for diagnosis of acute respiratory distress syndrome (ARDS) by the Berlin Criteria. Secondary endpoints included: time to initiation of TEAMV, clinically significant pulmonary adverse events (CSPAE, CTCAE ≥ Grade 2), transfusion reactions, and mortality. The incidence of TEAMV by non-inferiority (margin = 2.3%), and secondary endpoints were analyzed by modified intention to treat (mITT) and per protocol (PP). Sensitivity analyses with propensity score matching for key variables were conducted for the primary endpoint. The associations between PC and categorical variables were tested by stratified Cochran-Mantel-Haenszel and continuous variables by ANOVA for two-sided significance p = 0.05. results. A total of 2291 pediatric and adult patients (1068 PRPC and 1223 CPC) were enrolled in the respective cohorts with transfusion of 5,277 PRPC and 5,491 CPC. PC assignment compliance and study completion were > 94%. For the mITT data set, the cumulative incidence of TEAMV was lower for the PRPC cohort (log rank p = 0.039) than the CPC cohort (2.9% versus 4.6%, HR = 0.633: 95% CI 0.408-0.982). PRPC by mITT were non-inferior to CPC for the incidence of TEAMV due to all indications, and for TEAMV with pulmonary dysfunction (PD) by PEP (Table). PP analyses were consistent with mITT. Relative risk (RR) of TEAMV showed significantly (p Figure 1 Figure 1. Disclosures Wheeler: Novo Nordisk A/S: Consultancy; Bayer: Consultancy; BioMarin: Consultancy; HEMA Biologics: Consultancy; Spark: Consultancy; Takeda: Consultancy; UniQure: Consultancy. Nooka: Janssen Oncology: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Sanofi: Consultancy; Oncopeptides: Consultancy; Amgen: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy; Adaptive technologies: Consultancy; GlaxoSmithKline: Consultancy, Other: Travel expenses; Karyopharm Therapeutics: Consultancy. Uhl: UpToDate: Patents & Royalties; Abbott: Consultancy, Speakers Bureau; Grifols: Consultancy, Speakers Bureau. Spinella: Secure Transfusion Services: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company; Cerus Corporation: Consultancy, Research Funding. Liu: Cerus Corporation: Current Employment, Current equity holder in publicly-traded company. Benjamin: Cerus Corporation: Current Employment, Current equity holder in publicly-traded company. Corash: Cerus Corporation: Current Employment, Current equity holder in publicly-traded company.

Mantle cell lymphoma (MCL) is a rare, incurable mature B-cell lymphoma that can have either an aggressive or indolent clinical course. The hallmark aberration of MCL is the t(11;14)(q13;q32) translocation that places CCND1 under control of the immunoglobulin heavy chain (IGH) locus resulting in its constitutive expression. CCND1/IGH translocation occurs in nearly all MCL cases and arises during VDJ recombination. Whole genome sequencing (WGS) of MCLs has shown the prevalence of additional structural variations (SV), particularly in tumors with poor outcome. Complex rearrangements, such as chromothripsis and chromoplexy have been observed in MCL but their role in lymphomagenesis has not been determined. We hypothesized that some of these complex rearrangements afford a selective advantage to the tumor by disrupting tumor suppressor genes or by placing oncogenes in proximity to regulatory elements in cis, thereby resulting in ectopic expression. We performed WGS on tumor DNA extracted from 106 RCHOP-treated MCL patients. Matching ribosomal-depleted RNA-seq data was available for all tumor samples. Gene expression count values were obtained using Salmon and counts were normalized using the DESeq2 method. Structural variants were identified using a consensus between GRIDSS and Manta and these were analyzed to identify the topology of complex rearrangements using JaBbA. This allows the annotation of rearrangements such as chromothripsis and chromoplexy and enables the detection of genes near new regulatory elements through complex (multi-breakpoint) rearrangements. We supplemented this analysis by including 57 published classical and non-nodal leukemic MCL genomes. Chromothripsis and chromoplexy were observed in 8 and 12 tumors, respectively. The majority of the genomes were associated with isolated structural variations such as large deletions, inversions and reciprocal translocations were more common. Six genes (BCL10, TRAF6, TRAF3, MAP3K7, BTK, RELB) coding for canonical and non-canonical NFκB signaling proteins were found rearranged to within 1Mbp of a naïve B-cell super-enhancer region. The TRAF6 rearrangement was part of a chromothripsis and chromoplexy event involving both chr9 and chr11. A separate chromothripsis example involving chr1 placed each of BCL10 and NOTCH2 within 100-200kbp of super-enhancers. A 1Mbp region containing RELB was amplified and inserted into chr19p approximately 150kbp downstream a super-enhancer. An 800kbp deletion brought MAP3K7 to within 400kbp of a super-enhancer. DAZAP1, a gene known to be recurrently mutated in MCL, was translocated upstream to within 300kbp of a super-enhancer by t(5;19)(p13.3;p15.33). TRAF3 was translocated 400kbp upstream a super-enhancer by t(14;20)(q32.32;q13.13). None of the aforementioned SVs were associated with a detectable increase in expression of the affected gene. In contrast, we identified one genome in which the MYC oncogene was relocated 500kbp upstream of a super-enhancer via an unbalanced t(4;8)(q21.23;q24.21) translocation. In this case, MYC expression was in the 95 th percentile of MYC expression across the cohort. Focal deletions and amplifications were also found affecting lymphoma driver genes. Focal amplifications affecting 3q (34 tumors) and 5p (9 tumors), were among the most common recurrent events. These respectively affect the TERC and TERT genes, both involved in telomerase function. All tumors with TERT amplifications also showed TERC amplifications. TERC and TERT were expressed higher on average in amplified tumors than in unamplified tumors. Two tumors showed focal deletions affecting the 3' end of BIRC3. The focal deletion in one tumor was found to span to the 3' end of BIRC2 resulting in a BIRC2/BIRC3 fusion. Aberrant splicing across the two genes was evident in matching tumor RNA-seq data. Complex rearrangements in MCL have been found to link distant super-enhancer elements with a variety of lymphoma oncogenes. We noted a recurrence of such events affecting known regulators of NFκB signaling. We are using nanopore-based long-read PromethION sequencing to validate the structure of the derivative chromosome in these cases. Although these genes were not detectably overexpressed, deregulation of genes may be occurring by other means. The full extent of deregulation of NFκB and other oncogenic pathways will be revealed as complex rearrangements are studied in additional MCL tumors. Disclosures Coyle: Allakos, Inc.: Consultancy. Melnick: Epizyme: Consultancy; Daiichi Sankyo: Research Funding; Sanofi: Research Funding; Janssen Pharmaceuticals: Research Funding; Constellation: Consultancy; KDAC Pharma: Membership on an entity's Board of Directors or advisory committees. Scott: BC Cancer: Patents & Royalties: Patent describing assigning DLBCL COO by gene expression profiling--licensed to NanoString Technologies. Patent describing measuring the proliferation signature in MCL using gene expression profiling. ; AstraZeneca: Consultancy; Abbvie: Consultancy; NanoString Technologies: Patents & Royalties: Patent describing measuring the proliferation signature in MCL using gene expression profiling.; Rich/Genentech: Research Funding; Celgene: Consultancy; Incyte: Consultancy; Janssen: Consultancy, Research Funding. Morin: Epizyme: Patents & Royalties; Celgene: Consultancy; Foundation for Burkitt Lymphoma Research: Membership on an entity's Board of Directors or advisory committees.

A case of identical twins who developed transient aplastic anemia after chloramphenicol exposure was reported by Nagao and Mauer in the New England Journal of Medicine in 1969. Bone marrow (BM) morphology and tritiated thymidine labeling indices were suggestive of a failure of delivery cells from the undifferentiated stem cell compartment. They concluded that an underlying genetic factor which predisposed to the development of drug induced aplastic anemia was highly likely. We now report long term follow up on the twins from that article and have identified that they both harbour a mutation in GATA2. Twin 1 presented with severe pancytopenia at age 8 months, 3 months after chloramphenicol exposure. His leukocytes and erythrocytes had normalized with supportive care, but platelet count (PC) remained low at 92,000/mm3. Later in life, he was diagnosed with transfusion acquired hepatitis C, treated with Sofosbuvir/Velpatasvir. He did not develop recurrent infections, warts, lymphedema, or pulmonary symptoms. At age 51, he was referred to Hematology for asymptomatic thrombocytopenia with a PC of 17,000/mm3. BM aspirate and biopsy showed a variably cellular marrow with relative erythroid hyperplasia and megaloblastoid features. Cytogenetics, FISH for myelodysplastic syndrome (MDS) related abnormalities and a 33 gene panel for MDS/chronic myelomonocytic leukemia related mutations by next generation sequencing were all normal. A next generation sequencing panel of 59 genes associated with hereditary BM failure syndromes was remarkable only for a previously unreported heterozygous mutation in GATA2 (c1040C>A, pThr347Asn). Twin 2 was also exposed to chloramphenicol at 5 months of age and was found to be pancytopenic when evaluated for BM donation for his brother. His pancytopenia spontaneously resolved at the end of observation. Subsequent medical problems included partial complex seizures, dysautonomia, vertigo, chronic pain syndrome and recurrent Clostridium difficile colitis. He had no history of other recurrent infections, warts, lymphedema, or pulmonary symptoms. He had mild asymptomatic cytopenias noted with a white blood cell count of 3600/mm3, a hemoglobin of 12.9 g/dl and a PC of 97,000/mm3 at the age of 50 years. At the age of 52, he was referred to hematology and was asymptomatic with a normal hemogram. DNA sequencing confirmed an identical GATA2 mutation. GATA2, a DNA binding transcription factor with two zinc finger domains, plays a significant role in gene regulation, cell fate decisions and maintenance of the hematopoietic stem cell pool. Excessive GATA2 activity is reported to prevent stem cells from leaving the pool, while insufficient GATA2 activity causes stem cells to differentiate at increased rates thereby depleting the pool. Homozygous GATA deletions/mutations are lethal. Reported mutations include deletions, frame shift mutations, nonsense mutations and point mutations. Many point mutations appear to act by causing haplo-insufficiency. The point mutation in these patients maps in proximity to the C-zinc finger domain and could potentially disrupt an exonic splicing enhancer causing an in-frame deletion of exon six. Clinical syndromes associated with GATA2 mutations include familial BM failure and cytopenia; familial myelodysplastic syndromes and acute myeloid leukemia; immunodeficiency with monocytopenia and recurrent viral, fungal and mycobacterial infections; immunodeficiency with decreased natural killer, dendritic, B cells, and monocytes; Emberger syndrome presenting with myelodysplastic syndrome, warts and lymphedema; and pulmonary alveolar proteinosis. Cytopenia has been the only clinically obvious manifestation in these twins. Chloramphenicol has been associated with two forms of hematological toxicity. The first is a dose related reversible bone marrow suppression presenting as anemia, and the second is idiosyncratic, often fatal, aplastic anemia. It was proposed that these may be opposite ends of a spectrum with an underlying genetic predisposition leading to the more severe forms. The finding of a GATA2 mutation in these patients supports Nagao and Maurer's speculation that an underlying genetic factor affecting stem cell regulation predisposed to the development of chloramphenicol induced aplastic anemia in these twins. Figure Disclosures No relevant conflicts of interest to declare.

Objectives Mantle cell lymphoma (MCL) is an uncommon B-cell non-Hodgkin lymphoma that is incurable with standard therapies. The genetic drivers of this cancer have not been firmly established and the features known to contribute to differences in clinical course remain limited. We previously discovered non-coding and silent mutations in HNRNPH1 that affect its splicing and contribute to poor outcomes for patients with MCL. We sought to extend our understanding of the mechanisms by which HNRNPH1 contributes to MCL pathology using a combination of in vitro models and integrative analysis of RNA sequencing from MCL tumors. Methods We previously sequenced ribosomal RNA-depleted RNA from 130 MCL tumors. Based on our earlier identification of mutations in HNRNPH1 and altered splicing of this gene, we performed differential splicing analyses using rMATS and leafcutter. We investigated the functional and phenotypic effect of deregulated hnRNP H1 protein through siRNA knockdown. Results Our previous work identified that splicing of HNRNPH1, and not total mRNA expression, correlated with protein abundance in MCL tumors. As a result, our analysis of alternative splicing focused on events associated with altered splicing of HNRNPH1. We identified 155 unique alternative splicing events (ΔPSI > 0.1, FDR < 0.1). Gene ontology analysis identified various aspects of RNA processing which are significantly enriched within this gene list, including mRNA splicing, transport, and metabolic process. This nominates HNRNPH1 as part of the complex network controlling alternative splicing within MCL. Available CLIP-seq in HeLa cells provides evidence for direct interactions between hnRNP H1 and transcripts identified by our analysis (e.g. RBM25, EIF4A1, HNRNPA2B1). Of the 155 events we identified, more than half involved retained introns. Generally, retained introns result in non-productive RNA species, which indicates that this program of intron retention in MCL is a mechanism by which protein abundance can be regulated by hnRNP H1. For all cases with available Mantle Cell Lymphoma International Prognostic Indicator (MIPI) classification, we determined the splicing ratio for HNRNPH1 and observed a general association between high MIPI scores and a lower ratio of non-productive HNRNPH1 transcripts. This suggested that the increased hnRNP H1 abundance we observed in HNRNPH1-mutant tumors contributes to increased proliferation of MCL cells. We verified this in vitro with siRNA knockdown of HNRNPH1 in HEK cells, which resulted in a significant decrease in cell proliferation. Conclusions We have described a pattern of alternative splicing in MCL that is associated with alterations in HNRNPH1 splicing and related protein abundance. The prevalence of retained introns suggests that hnRNP H1 regulates the abundance of protein-coding transcripts via alternative splicing coupled to nonsense-mediated decay. We continue to explore targets of hnRNP H1, a novel oncoprotein in MCL. Disclosures Morin: Celgene: Consultancy.

Introduction: In an open-label phase 2 study, blinatumomab demonstrated efficacy with a manageable safety profile as second salvage in patients with relapsed or refractory B-cell Non-Hodgkin's lymphoma (R/R B-NHL) following platinum-based salvage regimens (Coyle et al. Leukemia & Lymphoma. 2020: 1-10). Blinatumomab is a BiTE® (bispecific T-cell engager) immuno-oncology therapy that activates endogenous cytotoxic T cells to kill target B cells. Here, findings from the updated analysis are reported (NCT02910063). Methods: Patients aged >18 years with biopsy-confirmed B-NHL without prior complete response or complete metabolic response (CMR) following first-line treatment with anthracycline- based chemotherapy and anti-CD20 therapy, had progressive metabolic disease (PMD), no metabolic response (NMR), or partial metabolic response (PMR; Lugano Classification) after ≥2 cycles of platinum-based S1 therapy were eligible. Blinatumomab was given by continuous intravenous infusion for a single 70-day cycle 1 (9 µg/day for 7 days, 28 µg /day for 7 days, and 112 µg /day for 42 days, followed by a 14-day treatment free interval) and an optional 28-day second cycle (9 µg /day for 7 days, 28 µg /day for 7 days and 112 µg / day for 14 days) at the investigator's discretion. Primary endpoint was CMR by central PET. Additional endpoints included objective response rate (ORR; CMR plus PMR), overall survival (OS), progression- free survival (PFS), duration of response, post-response HSCT rate, and the incidence and severity of adverse events (AEs). Results: As of the data cut date (June 3, 2020) for this updated analysis, 41 patients were enrolled between 23 January 2017 and 15 January 2018; 28 (68%) patients were refractory and 13 (32%) relapsed to first-line therapy, 66% had progressive disease following first salvage (S1), and 9 (22%) had double or triple hit status at baseline (Figure 1). ORR was 37% (15/41; 95% CI, 22-53) after 12 weeks of treatment, including 9 (22%) patients who achieved CMR and 6 (15%) achieved PMR. Of the 41 patients enrolled, 17 (42%) were double refractory; of which, 3 (7%) achieved CMR, and 3 (7%) achieved PMR. Of the 41 patients who received blinatumomab, median OS (95% CI) was 11.2 (5.9-NE) months with median follow-up time of 27.9 months. Among the 9 patients who achieved CMR, median OS (95% CI) was NE (7.0, NE) and median PFS (95% CI) was 8.4 (4.9-11.6) months with median follow of time of 4.7 months; of which, 3 patients had disease progression and 0 died. Of the 13 patients who achieved HSCT, median OS (95% CI) was NE (13.1-NE) with 69% of patients alive at 30 months and median PFS (95% CI) was 8.4 (5.3-13.9) months with 21% of patients alive at 12 months (Figure 2 and 3). In total, 29 (71%) patients had grade ≥3 treatment-emergent AEs, including included infections (n=8; 20%), neutropenia (n=4; 10%), pulmonary embolism (n=1; 2%), and acute pancreatitis (n=1; 2%). Consistent with previous blinatumomab reports, neurologic events (NEs) were reported in 23 (56%) patients, including 10 (24%) with grade 3 NEs and 3 (7%) with NEs leading to treatment discontinuation. Grade 3 cytokine release syndrome was reported in only 1 patient. 7 (17%) patients discontinued treatment due to AEs and 7 (17%) had fatal AEs of which were related to disease progression. Conclusions: In conclusion, durable complete remissions can be achieved with a manageable safety profile using blinatumomab as second salvage in patients with aggressive R/R B-NHL following platinum based first salvage regimens Figure 1 Disclosures Coyle: Amgen: Other: Travel support. Morley:Janssen: Honoraria, Other: Fees; AbbVie: Honoraria, Other: Fees; Roche: Other: travel support; Amgen: Honoraria, Other: Fees, travel support. Rambaldi:Sanofi: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Omeros: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support from Gilead.; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Advisory board and speaker fees from Pfizer.; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Research grant from Amgen Inc.; BMS/Celgene: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Astellas: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support of parent study and funding of editorial support. Received travel support., Research Funding; University of Milan: Current Employment. Furness:Amgen: Other: Travel Support. Desai:IQVIA: Current Employment. Mergen:Amgen: Current Employment, Current equity holder in publicly-traded company. OffLabel Disclosure: Durable complete remissions can be achieved with a manageable safety profile using blinatumomab as second salvage in patients with aggressive R/R B-NHL following platinum based first salvage regimens

Lenalidomide is an immunomodulatory drug (IMiD) with activity in lymphoid malignancies occurring primarily through immune modulation (eg, T-cell immune synapse enhancement and NK-cell/T-cell effector augmentation) and antiproliferative effects. Food and Drug Administration–approved for bortezomib-resistant, relapsed/refractory mantle-cell lymphoma, lenalidomide has demonstrated efficacy in several additional lymphoma subtypes. There are many ongoing clinical trials examining the use of lenalidomide alone or in combinatorial therapy. It will be important in these studies to delineate reliable, predictive biomarkers to optimally integrate lenalidomide into lymphoma treatment paradigms.

Objectives Mantle cell lymphoma (MCL) is an uncommon B-cell non-Hodgkin lymphoma that is incurable with standard therapies. The genetic drivers of this cancer have not been firmly established and the features known to contribute to differences in clinical course remain limited. We sought to extend our understanding of the molecular etiology of this malignancy using an integrative genomic analysis of diagnostic biopsies. Methods We performed exome sequencing on 51 frozen MCL tumors and analyzed these alongside previously published exome cohorts. We sequenced tumour genomes and matched constitutional DNA from 34 frozen MCLs, along with matched constitutional DNA, to more broadly identify the pattern of non-coding mutations. Based on mutations identified in this discovery cohort, we re-sequenced 18 recurrently-mutated genes in 212 archival MCLs, each having clinical follow-up data. We also performed RNA-seq on 110 of these cases and analyzed these data for alternative splicing and differential expression, including the differential splicing of HNRNPH1 in the context of recurrent intronic mutations. We investigated the functional and phenotypic effect of mutations and deregulated HNRNPH1 protein through ectopic expression of full-length HNRNPH1 and a mini-gene containing the exons and introns affected by mutations. Using custom droplet digital PCR (ddPCR) assays, we validated alternative splicing patterns in HNRNPH1 itself and other targets identified through re-analysis of available CLIP-seq data. Results In addition to confirming the prognostic association of TP53 and NOTCH1 mutations in MCL, we identified two additional genes associated with outcome: EWSR1 with poor outcome (HR = 5.6) and MEF2B with good outcome (HR = 0.2). By comparing mutation patterns to diffuse large B-cell lymphoma (DLBCL), we identified an MCL-specific missense hot spot in MEF2B, non-specific truncating mutations in EWSR1, and truncating mutations affecting the DAZAP1 C-terminus in both MCL and DLBCL. The DAZAP1 mutations are predicted to alter protein sub-cellular localization and disrupt protein-protein interactions. We also identified the focal recurrence of non-coding mutations surrounding a single exon of the HNRNPH1 gene that were largely restricted to MCL. These mutations affected a region bound by HNRNPH1 protein and disrupted the preferred binding motif of this protein. Intronic mutations were significantly associated with alternative splicing of the HNRNPH1 mRNA and appear to disrupt a negative regulatory loop that normally limits the level of HNRNPH1. Using cell-based assays, we have evaluated the role of HNRNPH1 in cell survival and proliferation. Our interrogation of alternative splicing events in downstream targets implicate HNRNPH1 as a master splicing regulator which may broadly perturb the transcriptome and proteome to favor lymphomagenesis in MCL. Conclusions We discovered three novel MCL-related genes with roles in RNA trafficking or splicing, namely EWSR1, DAZAP1, and HNRNPH1. Mutations in these RNA-binding proteins were identified in 49 of 291 (17%) samples analyzed. Our results improve the current understanding of the MCL mutational landscape, highlight the similarities and differences between MCL and DLBCL, and strongly implicate a role for aberrant regulation of RNA metabolism in MCL pathobiology. We elucidated a functional role for recurrent non-coding HNRNPH1 mutations specific to MCL and identified multiple downstream targets. We continue to explore putative trans targets of HNRNPH1, a novel oncoprotein in MCL. Disclosures Steidl: Seattle Genetics: Consultancy; Roche: Consultancy; Bristol-Myers Squibb: Research Funding; Bayer: Consultancy; Nanostring: Patents & Royalties: Filed patent on behalf of BC Cancer; Juno Therapeutics: Consultancy; Tioma: Research Funding. Connors:Bristol-Myers Squibb: Consultancy; Seattle Genetics: Honoraria, Research Funding; Takeda Pharmaceuticals: Honoraria. Villa:Roche, Abbvie, Celgene, Seattle Genetics, Lundbeck, AstraZeneca, Nanostring, Janssen, Gilead: Consultancy, Honoraria. Johnson:Roche: Consultancy, Employment, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel fees, gifts, and others, Research Funding; Abbvie: Consultancy, Employment, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Honoraria; BMS: Consultancy, Honoraria; BD Biosciences: Other: Provided a significant proportion of the antibodies used in this project free of cost.; Seattle Genetics: Honoraria; Lundbeck: Employment, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel fees, gifts, and others, Research Funding. Scott:Janssen: Consultancy, Research Funding; NanoString: Patents & Royalties: Named inventor on a patent licensed to NanoSting [Institution], Research Funding; Celgene: Consultancy; Roche/Genentech: Research Funding.

Background: Indolent lymphomas are characterized by a chronic relapsing-remitting course. Bendamustine-Rituximab (BR) has been shown to improve overall response rate and progression free survival (PFS) in the upfront treatment of patients with indolent B-cell non-Hodgkin lymphoma (iNHL), as compared with conventional chemoimmunotherapy (Rummel et al., 2013; Flinn et al., 2014). The pan-Canadian Oncology Drug Review has recommended publicly funding BR, but concluded there is substantial uncertainty regarding the regimen's cost-effectiveness. The objective of our study was to assess the cost-effectiveness of BR as compared with Rituximab-Cyclophosphamide, Doxorubicin, Vincristine, Prednisone (RCHOP) as frontline treatment for patients with advanced iNHL from a Canadian perspective. Methods: A Markov model was developed to estimate the costs, life expectancy and quality-adjusted life-years (QALYs) associated with the two regimen options allowing determination of the incremental cost-utility ratio (ICUR). Model parameters were derived from peer-reviewed studies. Key health states included FT (frontline therapy), MR (2-year state of maintenance R), PF1 (1st progression-free state), PD1/2/3 (subsequent progressive disease states requiring salvage), PF2/3/4 (subsequent progression-free states post-salvage), palliation and death. To determine progression after FT, individual data elements were derived from the published literature, and transition probabilities were determined through parametric survival analysis. Age-related mortality was obtained from Statistics Canada. Cost data (in 2016 Canadian dollars) were obtained from current funding arrangements under the New Drug Funding Program of Cancer Care Ontario, the Ontario Health Insurance Plan Schedule of Benefits and Fees, and the published literature. Utility values for health states and utility decrements associated with treatment related adverse events (AEs) were derived from peer-reviewed studies. The analysis was performed from the health care provider perspective, with a lifetime time horizon (equivalent to 24 years) and cycle lengths of 6 months. Patients were treated with a maximum of 3 lines of salvage therapy (3rd salvage permitted in age-appropriate patients achieving at least 1 year remission from 2nd line salvage). In order to address uncertainty of model input variables, a probabilistic analysis in which model inputs were represented by probability distributions was utilized, permitting a Monte Carlo simulation with 5000 replications. Costs and utilities were discounted at a rate of 5% per annum. Subgroup analyses for the following iNHL histologies were performed using individualized parametric survival curves: follicular lymphoma (FL), mantle cell lymphoma (MCL), marginal zone lymphoma (MZL), lymphoplasmacytic lymphoma (LPL). Results: The average costs and QALYs for the two treatment strategies were as follows: $116,811 and 5.86 QALYs for RCHOP; $121,364 and 6.38 QALYs for BR. The incremental cost per QALY gained for using BR with respect to RCHOP was $8,812 (Figure 1). Subgroup analyses revealed robust ICUR results: $27,398 (FL), $8,924 (MCL), $10,012 (MZL), $6,565 (LPL). For the commonly accepted willingness to pay threshold (WTP) of $50,000 per QALY, BR was the more cost-effective strategy 92% of the time in the entire cohort (Figure 2). In the subgroup analyses, BR was the more cost-effective strategy 66%, 82%, 64%, 86% of the time in FL, MCL, MZL, LPL respectively. ICUR results were robust to sensitivity analyses of key variables including age at study entry, maximum allowable age for therapy, duration of AEs, probability of death from palliation state and discount rate. Conclusion: Our model suggests that BR is a cost-effective strategy for the frontline treatment of patients with iNHL as compared with RCHOP. The cost-effectiveness of BR may be driven by the upfront PFS advantage despite higher acquisition costs and is consistent in various iNHL histology subgroups. Our analysis supports the use of frontline BR for iNHL in the Canadian setting. Figure 1 Cost-effectiveness acceptability curve Figure 1. Cost-effectiveness acceptability curve Figure 2 Incremental cost-effectiveness of BR relative to RCHOP with WTP threshold of $50,000 per QALY Figure 2. Incremental cost-effectiveness of BR relative to RCHOP with WTP threshold of $50,000 per QALY Disclosures Bence-Bruckler: Lundbeck: Membership on an entity's Board of Directors or advisory committees.

BACKGROUND: AML is a group of clinically heterogeneous diseases. We hypothesized that heterogeneous presentation of AML is a reflection of equally heterogeneous genetic process during the leukemogenesis. METHODS: 536 AML patients (pts) bone marrow samples were analyzed by targeted capture exome sequencing of 295 genes. Extensive clinical-genotype correlation was performed using well annotated clinical data. RESULTS: The median age of the cohort was 62 years (IQR: 51-72) including 297 (55%) elderly (age ≥60), and 239 (45%) young (age Elderly pts and young pts had distinct mutational landscape. (1.3-9.6), p = 0.0079] were significantly more enriched in elderly AML, whereas young AML pts were enriched with mutations in FLT3 [OR 0.6 (0.4-0.9), p = 0.0089], NPM1 [OR 0.5 (0.3-0.9), p = 0.0113], PTPN11 [OR 0.2 (0.2-0.7), p = 0.0033], and WT1 [OR 0.4 (0.2-0.7), p = 0.0033]. Some of the mutations enriched in elderly pts are frequently observed in pts with clonal hematopoiesis with indeterminate potential. Based on the ontogeny of AML, PTPN11 [OR 7.6 (1-57.2), p=0.0210], NPM1 [OR 3.0 (1.5-6.1), p = 0.0007], WT1 [OR 2.9 (1.1-7.4), p=0.0279] mutations were significantly enriched in dnAML, while SF3B1 [OR 0.4 (0.18-0.89), p=0.0376], SRSF2 [OR 0.5 (0.3-0.85), p = 0.0109], TP53 [OR 0.5 (0.3-0.8), p = 0.0131], ASXL1 [OR 0.6 (0.36-0.95), p=0.0451] mutations were more enriched in stAML (Figure A). We then correlated mutation data with clinical and immunological parameters that are routinely tested in AML. Mutations in NPM1, FLT3, PTPN11 and NRAS were associated with significantly higher white blood cell (WBC) counts, bone marrow blast and LDH, which is consistent with their hyperproliferative activity as class 1 genes. In contrast, pts with mutations in TP53, STAG2 and ASXL1 presented with significantly low bone marrow blast, circulating blast, and WBC. Mutations in BCOR and ASXL1 was associated with significantly low LDH. Interestingly, pts with IDH2 mutations presented with significantly higher platelet, which is consistent with anecdotal report (DiNardo et al. Am J Hematology). Not surprisingly, TP53 mutations were associated with complex cytogenetics, whereas SRSF2, NPM1, IDH2, FLT3, and CEBPA mutations were associated with good and intermediate cytogenetics by ELN classification (Figure B). Pts with NPM1, IDH2, and IDH1 mutations were associated with less HLA-DR and CD34 expression in blast by flow cytometry. This is consistent with the frequent presentation of these AML sub-types with cuplike nuclei (Rakheja et al. BJH). DNA sequencing of a large cohort also allowed us to detect mutations that have not been as commonly reported in AML. We detected hot-spot mutations in exon 2 of MYC and MYCN genes in 9 (2%) AML pts. Additionally, internal tandem duplication (ITD) in MYC was also detected in one patient. Immunohistochemical staining showed that MYC expression was significantly elevated in patients with MYC mutations than in patients without the mutations (median H score 22 vs. 15 in MYC mutated vs. normal karyotype control, p < 0.001, 22 vs. 13.5 in MYC mutated vs. trisomy 8 control). These data suggest that a subset of AML is driven by the strong MYC signaling, consistent with a prior study (Ohanian et al. Leuk Lymphoma). CONCLUSION: Heterogeneous clinical presentation of AML has significant association with genetic heterogeneity, which suggest that distinct genetic basis of leukemogenic process has strong role in defining clinical presentation of AML. These data also help stratifying the patients for the likely target of precision medicine. Disclosures DiNardo: Medimmune: Honoraria; Celgene: Honoraria; Agios: Consultancy; Abbvie: Honoraria; Karyopharm: Honoraria; Bayer: Honoraria. Kadia:Celgene: Research Funding; Pfizer: Consultancy, Research Funding; BMS: Research Funding; Jazz: Consultancy, Research Funding; Abbvie: Consultancy; Abbvie: Consultancy; Amgen: Consultancy, Research Funding; BMS: Research Funding; Pfizer: Consultancy, Research Funding; Jazz: Consultancy, Research Funding; Takeda: Consultancy; Amgen: Consultancy, Research Funding; Takeda: Consultancy; Novartis: Consultancy; Celgene: Research Funding; Novartis: Consultancy. Cortes:novartis: Research Funding. Daver:Daiichi-Sankyo: Research Funding; Pfizer: Consultancy; Alexion: Consultancy; ARIAD: Research Funding; Karyopharm: Consultancy; ImmunoGen: Consultancy; Kiromic: Research Funding; Otsuka: Consultancy; Sunesis: Consultancy; Novartis: Research Funding; BMS: Research Funding; Incyte: Consultancy; Novartis: Consultancy; Sunesis: Research Funding; Karyopharm: Research Funding; Pfizer: Research Funding; Incyte: Research Funding. Pemmaraju:SagerStrong Foundation: Research Funding; celgene: Consultancy, Honoraria; cellectis: Research Funding; samus: Research Funding; daiichi sankyo: Research Funding; Affymetrix: Research Funding; stemline: Consultancy, Honoraria, Research Funding; plexxikon: Research Funding; novartis: Research Funding; abbvie: Research Funding.

Background: Autologous hematopoietic stem cell transplantation (autoHSCT) following response to salvage chemotherapy is the standard of care for patients with relapsed/refractory (r/r) aggressive B-cell lymphoma after first-line chemotherapy. Patients without complete metabolic response (CMR) to first salvage (S1) therapy have limited options and poor outcomes based on historical data. Blinatumomab, a bispecific T-cell engager (BiTE®) antibody construct that directs cytotoxic T cells to lyse B cells expressing CD19, has demonstrated a survival benefit in B-cell acute lymphoblastic leukemia and has antitumor activity in patients with r/r aggressive B-cell non-Hodgkin lymphoma (B-NHL), including patients previously treated with autoHSCT. This open-label, multicenter, phase 2 portion of an adaptive phase 2/3 study (ClinicalTrials.gov, NCT02910063) assessed the efficacy and safety of blinatumomab as a second salvage (S2) therapy for patients with aggressive r/r NHL who have not achieved CMR following platinum-based S1 chemotherapy. Methods: Patients ≥18 years had biopsy-confirmed r/r aggressive B-NHL without a prior complete remission or CMR after first-line treatment with an anthracycline and anti-CD20 agent, and had either progressive metabolic disease (PMD), no metabolic response (NMR), or partial metabolic response (PMR; Lugano Classification) after ≥2 cycles of platinum-based S1 therapy. Patients with prior radiotherapy were PET+ ≥6 weeks after the last dose. Blinatumomab was given by continuous intravenous infusion for a single 70-day cycle 1 (9 μg/day for 7 days, 28 μg/day for 7 days, and 112 μg/day for 42 days, followed by a 14-day treatment-free interval) and an optional 28-day cycle 2 (9 μg/day for 7 days, 28 μg/day for 7 days, and 112 μg/day for 14 days). The primary endpoint was CMR by central PET. Additional endpoints were objective response rate (ORR [CMR + PMR]), post-response HSCT realization rates, and the incidence/severity of adverse events (AEs). Results: Of the 41 patients enrolled, most had PMD/progressive disease (66%) and had refractory (68%) or relapsed (32%) disease; 5 (12%) had NMR, and 9 (22%) had PMR (Table). All 41 patients received blinatumomab; 19 (46%) completed cycle 1 (Table). Twenty-two patients discontinued cycle 1 (disease progression, n=17; AE n=4; death, n=1). Among the 17 patients who discontinued cycle 1 due to disease progression, 8 (47%) completed at least 90% of planned treatment duration. Four patients started cycle 2; 3 (7%) completed cycle 2. One patient discontinued cycle 2 due to AEs. The ORR (within 12 weeks of starting blinatumomab) was 37% (15/41 patients; 95% CI, 22%, 53%); 9 (22%) patients achieved CMR (Table). Eight (20%) patients had HSCT in remission, 7 (17%) with autoHSCT (CMR, n=6; PMR, n=1), and 1 with allogeneic HSCT in PMR. Thirty-five patients did not have HSCT (n=32) or had delayed HSCT (n=3) due to PMD (n=17), lack of CMR (n=4), AE (n=4), patient preference (n=1), NMR or unknown (n=1), and other (n=8); 1 patient had missing information. Eight of 9 CMR patients (89%) were alive without relapse, with a median follow up time of 8.8 months. The Kaplan-Meier estimate at 9 months was 51%; median overall survival (OS) was not reached (Table). In total, 24 (59%) patients had grade ≥3 treatment-emergent AEs, and 10 (24%) had grade ≥4 treatment-emergent AEs. Seven (17%) patients discontinued treatment due to AEs. Consistent with previous blinatumomab reports, neurologic events (NEs) were reported in 23 (56%) patients, including 10 (24%) with grade 3 NEs and 3 (7%) with NEs leading to treatment discontinuation. Grade 3 cytokine release syndrome was reported in only 1 patient. Other grade ≥3 AEs included infections (n=8; 20%), bone marrow toxicity (n=7; 17%), thromboembolic events (n=3; 7%), hepatic disorders (n=2; 5%), and acute pancreatitis (n=1; 2%). Conclusions: In patients with r/r aggressive B-NHL and predominantly progressive disease following ≥2 cycles of platinum-based S1 chemotherapy, blinatumomab monotherapy as S2 therapy induced CMR/PMR in 37% of patients and led to HSCT in 20%. When considering that 66% of the patients enrolled had progressive disease and that 47% received the therapeutic dose, blinatumomab showed promising efficacy consistent with the efficacy and safety demonstrated in earlier blinatumomab B-NHL trials and potentially offers a treatment option for patients unresponsive to standard salvage regimens. Disclosures Coyle: Amgen Inc.: Other: non-financial relationship. Morley:Amgen Inc.: Honoraria, Other: non-financial; Roche: Honoraria, Other: non-financial, Research Funding. Rambaldi:Celgene: Consultancy; Roche: Consultancy; Omeros: Consultancy; Italfarmaco: Consultancy; Novartis: Consultancy; Amgen Inc.: Consultancy; Pfizer: Consultancy. Zhang:Amgen Inc.: Employment, Equity Ownership. Jung:Amgen Inc.: Employment, Equity Ownership. Franklin:Amgen Inc.: Employment, Equity Ownership.

Background: Hydroxyurea, an antineoplastic agent, was approved in 1998 to reduce the frequency of sickle cell crises in adult patients with sickle cell disease (SCD). More recently in 2017, hydroxyurea was also approved for pediatric patients, 2 years of age and older with sickle cell anemia and recurrent moderate to severe painful crises. Prior to this, hydroxyurea had been used in the United States (US) in pediatric patients with SCD without a labeled indication. This study investigated hydroxyurea utilization patterns among pediatric and adult patients with SCD in the US prior to the pediatric approval using administrative claims data in the Sentinel database sponsored by the US Food and Drug Administration. Methods: Data from 17 health plans contributing to the Sentinel Distributed Database were queried from January 1, 2000 through September 30, 2015. Eligible patients had a claim with a diagnosis of SCD in any care setting at any time during the query period. SCD was identified using International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) diagnosis codes. Patients were required to be enrolled in plans with both medical and drug coverage on the date of their SCD diagnosis. Patients who were dispensed hydroxyurea after diagnosis of SCD were identified as hydroxyurea users. Patients included in the sub-analysis evaluating hydroxyurea cumulative duration of therapy were required to be continuously enrolled with medical and drug coverage for at least 90 days prior to the initial hydroxyurea dispensing date, during which, gaps in coverage of up to 45 days were allowed. For this sub-analysis, follow-up began on the day of the first valid hydroxyurea dispensing and continued until the first occurrence of any of the following: 1) disenrollment; 2) death; 3) the end date of the data provided by each Data Partner; 4) the end of the last hydroxyurea exposure episode; or 5) the end of the query period. Cumulative duration of hydroxyurea therapy was calculated by summing days' supplies from outpatient pharmacy hydroxyurea dispensings for each patient. Results were stratified by age group (≤1, 2-5, 6-11, 12-17, 18-49, and 50+ years) and race. Results: A total of 95,606 patients with SCD were identified during the query period. Roughly half of patients (46.8%) were adults 18-49 years of age. Thirty-two percent (n= 30,900) were ≥50 years of age and 20.9% (n= 19,950) were ≤17 years of age. The study population included 40.3% African-American and 15.9% White patients. Race was unknown for 42.6% of the study population. Among pediatric SCD patients ≤1, 2-5, 6-11 and 12-17 years of age, hydroxyurea was dispensed to 4.1%, 7.7%, 16.5% and 16.0% of patients respectively. Among adults 18-49 years and ≥50 years, 18.4% and 4.7% respectively were dispensed hydroxyurea. The majority of pediatric hydroxyurea users were dispensed hydroxyurea for ≥ 325 days cumulatively. The median [inter quartile range] number of days of cumulative hydroxyurea exposure among patients ≤1, 2-5, 6-11, 12-17, 18-49 and 50+ years were 422 [139, 789], 420 [157, 836], 462 [156, 1145], 328 [120, 877], 204 [65, 505] and 253 [88, 599] days respectively. Conclusions: Although hydroxyurea was not approved for pediatric use in the US until 2017, for the period January 1, 2000 through September 30, 2015, the proportion of pediatric SCD patients 6-11 years and 12-17 years and adult SCD patients 18-49 years of age who were dispensed hydroxyurea were similar in the FDA Sentinel database. Among patients dispensed hydroxyurea, the durations of cumulative exposure were generally higher among pediatric compared to adult patients with SCD. The higher cumulative hydroxyurea exposure duration among pediatric SCD patients may reflect greater tolerability and adherence to hydroxyurea treatment in this population among other reasons. While this analysis evaluated utilization patterns prior to hydroxyurea approval for pediatric SCD patients, further research to evaluate any changes in hydroxyurea use patterns after the pediatric labeling would be useful. Disclosures No relevant conflicts of interest to declare.