ALBERT

Description: Introduction: Venetoclax (VEN) based therapy has become a standard of care in front line and relapsed-refractory (R/R) CLL based on favorable efficacy and toxicity. Whereas prospective data regarding activity of therapies following ibrutinib (IBR) or idelalisib (IDE) are available in the settings of progression (VEN, non-covalent BTKi) and intolerance (acalabrutinib), how best to manage patients (pts) who discontinue (dc) VEN remains a key unanswered question. With the increased use of VEN in early lines of therapy (LOT; CLL 14, MURANO), the activity of BTK inhibitors (BTKi) and cellular therapies following VEN becomes a critical issue. No prospective study has addressed this question, and currently reported VEN clinical trials have limited information about subsequent treatments. While recent data describe VEN resistance mechanisms (Guieze 2018, Blombery 2019), the impact of VEN resistance on efficacy of post VEN therapies is unknown. To address this gap, we conducted an international study to identify a large cohort of pts who dc VEN and have been subsequently treated. Methods: We conducted an IRB approved multicenter (31 US, EU, South American sites, in partnership with UK CLL Forum and CORE registry), retrospective cohort study of CLL pts who dc VEN for any reason. We examined demographics, dc reasons, responses, survival, adverse events (AEs) and activity of post VEN therapies. Primary endpoints were overall response rate (ORR) and progression free survival (PFS) for the post VEN treatments stratified by treatment type (BTKi, PI3Ki and cellular therapy: CAR-T or alloHSCT). ORR was defined by iwCLL criteria and PFS was defined from VEN dc to disease progression (PD), death, or last follow up for next treatment. Pts were further stratified by BTKi (resistant / intolerant) and PI3Ki exposure prior to VEN. PFS-2 was defined as time from VEN start to tumor progression on IBR or death from any cause. Results: 326 CLL pts who dc VEN in the front line (4%) and R/R settings (96%) were identified. The cohort was 69% male, 87% white, median (med) age 66 (38-91) at VEN start, 27% treated with VEN based combinations (n=88, med 6 cycles anti-CD20 abs). Pre VEN prognostic features: 82% IGHV unmutated (n tested=166), 47% del17p (n=306), 45% TP53 mut (n=217), 39% complex karyotype (n=273), 23% BTK mut (n=79), 18% NOTCH1 mut (n=103), 10% PLCγ2 mut (n=74). Pts received med 3 therapies (0-11) prior to VEN; 40% were BTKi naïve (n=130), 60% were BTKi exposed (196) and 81% were IDE naïve (n=263). Most common reasons for VEN dc were PD (38%), AE (20%), Richter's transformation (RT, 14%), 8% pt preference, and HSCT 5%. Of 326 pts who dc VEN, 188 (58%) were treated with a subsequent LOT, 61 are alive and untreated and 77 died prior to a subsequent LOT. Post VEN sequencing analyses focused on BTKi, PI3Ki and cellular therapy (CAR-T or alloHSCT) activities following VEN dc (Table1). ORR to BTKi was 84% (n=44) vs. 54% (n=30, p

Description: Introduction: Venetoclax (Ven) is approved for relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL) as monotherapy (Ven mono) or in combination (Ven paired) with rituximab based on clinical trials with selected patients (pts) and limited ibrutinib exposure. Whether Ven paired is superior to Ven mono, patterns of care, and outcomes following Ven discontinuation are unknown. Further, better delineation of adverse events (AEs) when Ven is used outside of clinical trials is needed. To address these gaps, we conducted a multicenter, international study in partnership with CLL Collaborative Study of Real World Evidence (CORE) and UK CLL Study Forum examining the clinical experience of 348 Ven treated CLL pts, representing the largest series of Ven treated pts reported to date. Methods: We conducted a retrospective cohort analysis of CLL pts treated with Ven across 24 US and 42 UK academic and community centers. We examined demographics, baseline disease characteristics, dosing, AEs, TLS risk and outcomes, response rates, outcomes (overall survival (OS) and progression free survival (PFS)), and tx sequencing. TLS events were defined by Howard criteria. PFS and OS were estimated by the Kaplan Meier method. Comparisons of outcomes used the Log Rank test. Univariate and multivariate analyses were performed with COX regression. All other comparisons were descriptive. Results: Of these 348 CLL pts, 94% were R/R, median age 67 years (range:37-91), 69% male, 85% white, and 73% Rai stage ≥2. 19% received Ven on clinical trial. 79% had Ven mono; Ven was paired most commonly with anti-CD20 (n=51) and ibrutinib (n=10). Pts received a median of 3 tx (range 0-15) before Ven; 78% received ibrutinib, 29% received PI3Ki, 20% had ≥2 prior kinase inhibitors, and 68% had chemoimmunotherapy. Median time from most recent tx to Ven start was 1.1 months (range 0-62). Pre-Ven prognostic markers included 43% del17p, 34% TP53 mutated, 24% del11q, 38% complex karyotype (≥ 3 abnormalities), and 84% IGHV unmutated (Table 1). TLS risk was low in 38%, intermediate in 34% and high in 28%. During ramp up, TLS was observed in 10% (22 lab, 9 clinical TLS events, 3 missing data). Following dose escalation, 70% achieved a stable Ven dose of 400 mg, 33% required ≥ 1 dose interruption and 27% required ≥ 1 dose reduction. AEs included grade 3 neutropenia 39%, grade 3 thrombocytopenia 29%, infections 25%, grade ≥ 2 diarrhea 7.8%, and neutropenic fever 7.7%. AEs were similar whether treated on or off clinical trial. The ORR to Ven mono, Ven paired was 81% (34% CR), 86% (29% CR). With a median follow-up of 14.2 months, median PFS and OS were not reached (12 month PFS 74%, OS 82%). Figure 1 depicts PFS stratified by Ven mono vs. paired, clinical trial vs. clinical practice, del17p status, and complex karyotype. Pts who discontinued Ven due to AEs had better OS compared with those who discontinued due to progression or Richter Transformation (RT) (Median OS 47 vs. 15.1 vs. 8.6 months, respectively). In multivariate analyses, complex karyotype was the only independent predictor of PFS (HR 2.8, p

Description: Introduction Chromosome instability (CIN) is a driver of copy number aberrations (CNAs) in cancer, and is a major factor leading to tumor heterogeneity and resistance to therapy. By definition, CIN is an increased rate or ongoing acquisition and accumulation of CNAs and not simply the existence of structurally and numerically abnormal aneuploid clones. In multiple myeloma (MM), the most common whole-chromosome CNAs involve either hyperdiploid or non-hyperdiploid clones. Secondary segmental CNAs are associated with high-risk (HR) in MM and involve gains of 1q21 and deletions of 17p (del17p). These types of intra-chromosomal segmental CNAs are also found in the CIN phenotypes of the autosomal recessive (AR) chromosome instability syndromes. These syndromes include Fanconi anemia, Bloom's syndrome, and ICF syndrome (Immunodeficiency, Centromeric instability and Facial anomalies). These chromosome instability syndromes display a spectrum of aberrations characterized by higher rates of chromosomal breaks, chromatid exchanges, quadriradials, and pericentromeric aberrations. In particular, patients with ICF syndrome show a marked increase of 1q12 pericentromeric instability including 1q12 decondensation, triradials, multibranched chromosomes 1q, and 1q micronuclei. ICF patients also show transient 1q aberrations including isochromosome 1q (iso1q) and unbalanced translocations of 1q to 9q and 16q. In MM, we have previously reported increasing pericentromeric instability during tumor progression resulting in increasing CNAs of 1q21 by unbalanced jumping translocations of 1q12 (JT1q12). Strikingly, in a subset of MM patients with 1q21 CNAs of ≥ 5 a distinct cytogenetic phenotype emerges which demonstrates transient 1q12 aberrations including 1q12 decondensation, triradials, and multibranched chromosomes 1q morphologically identical to those seen in ICF patients. In MM this chromosome instability leads to a cascade of increasing clonal 1q21 duplications, iso 1qs, and unbalanced 1q translocations with 16q and 17p, resulting in losses in these receptor chromosomes (RC) and massive intra-clonal CNA heterogeneity. Methods To investigate the cytogenetic impact and progression of high CNAs of 1q21, we performed a comprehensive metaphase analysis of 50 patients showing segmental aneuploidies with 4 or more copies of 1q by G-banding. Locus specific FISH and spectral karyotyping were used to identify the key transient unstable and clonal structural aberrations of 1q12 resulting in segmental aneuploidies in the derivative RCs. Probe for 1q12 (Vysis) was used according to the manufacturer's protocol. Locus specific BAC clones for 1q21 (CKS1B) and 17p (TP53) were prepared and analyzed as previously described (Sawyer et al., Blood 123: 2014). IGH translocations were investigated with IGH break apart probes (Vysis). Results Data for 50 patients including CNAs of 1q21 of ≥ 4, IGH translocations, del(17p), derivative RCs, are presented. The t(4;14) was found in 15 patients, del(17p) in 23, and both aberrations were found in 8 patients. All patients showed unbalanced gains of 1q and deletions of RCs, the most frequent being 7 patients with der(1;16) and 6 with iso1q. In four of the 23 patients with del(17p), the deletion was due to a JT1q12 to 17p. Seven patients with 1q21 CNAs of ≥ 5 showed profound instability involving the 1q12 satellite DNA, demonstrating both transient and clonal aberrations driving the 1q21 CNAs. These aberrations included unstable 1q21 triplications, JT1q12s, iso1q formation with intra-arm 1q12 CNAs, and region specific breakage-fusion-bridge cycle amplifications. Conclusions Among patients with ≥ 5 CNAs of 1q21, a subset develop an acquired HR chromosome instability phenotype with an elevated rate of 1q12 pericentromeric instability characterized by concomitant deletions in 16q, iso1q, del(17p), and intra-arm segmental instability. These patients show pronounced instability in the 1q12 satellite DNA, morphologically identical to ICF syndrome, suggesting hypomethylation of this region as a driver of both 1q21 CNAs and deletions in RCs. We hypothesize that region specific hypomethylation of 1q12 provides the genomic background for the onset of an acquired 1q12 chromosome instability phenotype in MM similar to that found in ICF syndrome. For myeloma patients demonstrating this 1q12 chromosome instability phenotype we propose the term "jumping 1q syndrome." Disclosures Epstein: University of Arkansas for Medical Sciences: Employment. Davies:Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; ASH: Honoraria; Abbvie: Consultancy; TRM Oncology: Honoraria; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; MMRF: Honoraria; Janssen: Consultancy, Honoraria. Morgan:Takeda: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria.

Description: Background: Sickle Cell Disease (SCD) describes a group of inherited hemolytic disorders caused by structurally abnormal variants of hemoglobin, which result in the sickle-shaped red blood cells (RBCs) that are characteristic of the disease. In patients with SCD, overexpression of adhesion molecules such as P-selectin bind sickled RBCs to endothelial cells; this contributes to hemolytic anemia and vaso-occlusive crises (VOCs), which are associated with severe acute and chronic pain. Patients with sickle cell disease often experience disease-related complications, affecting a diverse range of organs, thought to be due to the systemic impact of chronically inflamed vasculature, ongoing hemolysis and ischemic damage as a result of vaso-occlusive events. Many of these SCD-related complications are associated with significant morbidity and poor quality of life. The relationship between VOC frequency and the incidence of these complications is still being assessed. This study aimed to assess the relationship between the number of VOC experienced in the previous year and the occurrence of complications using real world evidence from the UK, specifically the Hospital Episode Statistics (HES) database. OBJECTIVE: To examine the relationship between the number of VOCs reported in the previous 12 months and the presence of SCD-related complications using a mixed modelling approach. METHODS: All patients reported with a diagnosis of SCD between 2008 and 2017 in the NHS England's HES database were identified. Detailed follow-up data on the number of vaso-occlusive crisis events and occurrence of complications was evaluated using ICD-10 diagnosis codes. Assuming no unmeasured confounding, the causal effect of VOCs, categorized into 3 groups (0, 1-2, 3+), was estimated using marginal structural models (MSM) for the complications reported in the dataset. To obtain inverse probability of treatment and censoring weights (IPTW and IPCW), the probability of being in each VOC category was estimated with a multinomial logistic model, and subsequently, the probability of being censored was estimated with a binary logistic model. The two models were adjusted for age, gender, ethnicity, and the occurrence in the previous 12 months of the 20 most common SCD complications and comorbidities in the dataset. Pooled logistic regressions were used to approximate the IPW-MSM Cox model. E-values were used to assess the minimum strength of association that an unmeasured confounder would have to have with both exposure (VOC) and outcome in order to fully explain away the observed relationship. Uncertainty in the magnitude of the E-value required to explain observed associations was explored by calculating values for both the point estimate and the lower bound of the confidence interval. RESULTS: A total of 15,076 patients were identified with a diagnosis of SCD in the HES database for this analysis. Patients had a median age of 30 and a female-male ratio of 1.7:1. A broad range of SCD related-complications were experienced by patients in the UK as shown in Table 1. Rates of some complications were observed less frequently than expected, in particular, leg ulcers, pulmonary hypertension, osteomyelitis, priapism and acute kidney injury, reported at

Description: Heterozygous mutations in several core members of the spliceosome complex have been reported in Myelodysplastic Syndromes (MDS) and Acute Myeloid Leukemia (AML). In particular high frequency SF3B1 hotspot mutations, a component of the U2 complex involved in the interaction with the branch point (BP) and recognition of the 3' splice sites (ss) during splicing, have been identified in Refractory Anemia with Ringed Sideroblasts (RARS) a subtype of MDS. Using computational analyses of RNAseq from several cancer types including RARS, we identified that SF3B1 hotspot mutations induce aberrant 3'ss selection by recognizing a cryptic AG located between 15 to 24 nucleotides upstream of the canonical AG. Experimental confirmation of these motif features was performed using minigenes in SF3B1 mutant cells. Furthermore, we discovered that SF3B1 mutant utilized a different BP from that used by SF3B1 wild-type providing novel mechanistic insights into changes in function induced by the hotspot mutations. The induction of aberrant splicing can introduce premature termination codons thus targeting mRNA for degradation by Nonsense Mediated Decay (NMD). We predicted that close to 50% of the aberrantly spliced genes would be subject to NMD and showed (using isogenic Nalm-6 cells engineered by AAV homology to express SF3B1K700E or SF3B1K700K) that several of these genes were downregulated at the transcript and protein levels. These downregulated genes/proteins might be involved in the pathogenesis of SF3B1 mutant cancers. Interestingly, pathway analysis of genes differentially expressed or aberrantly spliced in SF3B1 mutant compared to wild-type in RARS samples identified cell differentiation and epigenetics as the primary misregulated pathways. To study the impact of SF3B1 mutations on differentiation, we used the TF-1 differentiation cell model where erythroid differentiation is induced by treatment with erythropoietin (EPO). EPO treatment, as expected, induced erythroid differentiation in TF-1 cells transduced with SF3B1WT, but a block in erythroid differentiation was observed in TF-1 cells transduced with SF3B1K700E (the most common mutation in MDS and chronic lymphocytic leukemia (CLL)). Intriguingly, SF3B1G742D, which is found mutated in CLL but not MDS, did not block differentiation in this myeloid differentiation model, implying that specific SF3B1 mutations and splicing aberrations have important context dependent effects. Pathway analysis comparing SF3B1K700E vs. SF3B1WT or SF3B1G742D identified several genes involved in heme biosynthesis or downstream of GATA1 to be downregulated (such as, AHSP, ALAS2, CCL5, CD36, EPOR, GP1BB, HBB, HBE1, HBG1, PRG2) in SF3B1K700E cells only. This is consistent with the role of SF3B1K700E in RARS. In our analyses, we also identified that ABCB7 is aberrantly spliced and that the aberrant transcript is subject to NMD, causing downregulation of the canonical transcript and protein. ABCB7 is a mitochondrial transporter important in cellular iron metabolism and in heme production; moreover, partial loss of function mutation in ABCB7 has been identified in X-linked sideroblastic anemia and ataxia, demonstrating an iron overload phenotype in cells with defective ABCB7. Interestingly, when ABCB7 was knocked down in TF-1 cells we observed block in differentiation similar to that observed in SF3B1K700E cells suggesting a link between SF3B1 mutation and ABCB7 levels and impaired differentiation. Taken together, these data suggest that SF3B1 mutations induce aberrant splicing and as a consequence downregulation of several genes that contribute to the block in erythroid differentiation, one of the key biological defects observed in MDS. Disclosures Buonamici: H3 Biomedicine: Employment. Darman:H3 Biomedicine: Employment. Perino:H3 Biomedicine: Employment. Agrawal:H3 Biomedicine: Employment. Peng:H3 Biomedicine: Employment. Seiler:H3 Biomedicine: Employment. Feala:H3 Biomedicine: Employment. Bailey:H3 Biomedicine: Employment. Chan:H3 Biomedicine: Employment. Fekkes:H3 Biomedicine: Employment. Keaney:H3 Biomedicine: Employment. Kumar:H3 Biomedicine: Employment. Kunii:H3 Biomedicine: Employment. Lee:H3 Biomedicine: Employment. Mackenzie:Eisai: Employment. Matijevic:Eisai: Employment. Mizui:H3 Biomedicine: Employment. Myint:Eisai: Employment. Park:H3 Biomedicine: Employment. Pazolli:H3 Biomedicine: Employment. Thomas:H3 Biomedicine: Employment. Wang:H3 Biomedicine: Employment. Warmuth:H3 Biomedicine: Employment. Yu:H3 Biomedicine: Employment. Zhu:H3 Biomedicine: Employment. Furman:Acerta Pharma BV: Research Funding; Gilead: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Speakers Bureau. Ebert:Celgene: Consultancy; H3 Biomedicine: Consultancy; Genoptix: Consultancy, Patents & Royalties. Smith:H3 Biomedicine: Employment.

Description: Background: Trauma surgeons have suggested that the optimal transfusion support for actively bleeding patients may be a 1:1:1 ratio of red cells, plasma and platelets (plts). Therefore, the only reason to give component therapy - rather than whole blood (WB) - for these patients may be because of the poor post-transfusion survivals of plts stored at 4°C. However, for trauma/surgical patients, even short plt survivals may be sufficient to allow the surgeon enough time to repair the injury. We report the "first ever" data on the post-storage viability of plts stored at 4°C beyond 3 days. In the studies to be reported here, plts were stored within WB for up to 22 days at 4°C. Study Design/Methods: Normal subjects donated a unit of WB that was stored at 4°C either for 12 days with mixing only at the end of storage or for 10, 15, or 22 days with end-over-end rotation of the WB throughout storage. After storage, a plt concentrate was prepared from the WB using standard centrifugation procedures. At the end of WB storage, the donor donated a 40 ml blood sample from which fresh plts were prepared. The autologous stored and fresh plts were radiolabeled with 111In or 51Cr, respectively, before simultaneous transfusion into their donor. Serial post-transfusion blood samples were collected to determine stored versus fresh plt recoveries and survivals. Our pre-defined acceptance criteria were: 1) stored plt recoveries should average ≥50% of the same donor's fresh plt recoveries; and 2) plt survivals should average ≥1 day. Results/Findings: When the WB was mixed only at the end of storage, plt yields in the WB were just 48% of baseline values with average plt counts of 4.6 ± 2.0 x 1010. This amount of plt loss was considered unacceptable (Table). In contrast, with continuous end-over-end rotation of the WB during storage, plt yields after 15 days were 76% of baseline values and plt counts averaged 7.6 ± 1.4 x 1010 (well within FDA guidelines that require 5.5 x 1010 plts/concentrate prepared from WB). Radiolabeled autologous plt recoveries averaged 27 ± 11% (49 ± 16% of fresh) and survivals averaged 1.2 ± 0.4 days (16 ± 1% of fresh); i.e., our pre-defined plt acceptance criteria were met. Storage for 22 days gave unacceptable results. Conclusion: Plt concentrates stored at 4°C for up to 3 days have been FDA approved for use in thrombocytopenic patients since the 1970's. These plts had autologous plt recoveries of 40 ± 5% and survivals of 1.0 ± 0.1 days (S.E.) (Br J Haematol 1976;34:403-419). The FDA has recently approved the use of 3-day 4°C stored apheresis plts for actively bleeding patients. Our data may suggest that plts stored within WB at 4°C for up to 15 days may provide similar post-storage plt viability as plt concentrates or apheresis plts stored for ≤3 days. Red cells and plasma derived from CP2D WB stored for 21 days at 4°C are already licensed. Therefore, for actively bleeding patients who need all three components (red cells, plasma, and plts), WB stored for up to 15 days may provide effective quantities of all the needed components. Table 1. AUTOLOGOUS YIELDS, RECOVERIES, AND SURVIVALS OF PLATELETS STORED IN WHOLE BLOOD AT 4°C Storage Time (Days) N Rotation WB PLT COUNTS x 1010 Post-Storage Yield(% of Baseline) PLT RECOVERIES (%) PLT SURVIVALS (Days) Baseline Post-Storage Fresh Stored % of Fresh Fresh Stored % of Fresh 12 7 Mixed at end of storage* 9.4 ± 2.4 4.6 ± 2.0 48 ± 12 50 ± 15 22 ± 8 48 ± 29 8.3 ± 1.6 1.8 ± 0.6 23 ± 10 10 10 Continuously during storage** 9.5 ± 2.1 7.2 ± 1.6 77 ± 10 50 ± 10 26 ± 7 51 ± 7 8.1 ± 1.1 1.3 ± 0.3 16 ± 4 15 10 Continuously during storage** 10.0 ± 1.0 7.6 ± 1.4 76 ± 10 55 ± 11 27 ± 11 49 ± 16 8.0 ± 0.1 1.2 ± 0.4 16 ± 1 22 3 Continuously during storage** 12.9 ± 1.9 9.2 ± 0.7 73 ± 15 56 ± 12 14 ± 4 25 ± 5 7.7 ± 0.6 0.8 ± 0.3 10 ± 3 Data reported as average ±1 S.D. *WB units were hand mixed only at the end of storage before plt counting. **WB units were continuously rotated end-over-end during storage. Disclosures Slichter: Cellphire, Inc.: Research Funding; Cerus Corporation: Research Funding; Terumo BCT: Research Funding; Department of Defense: Research Funding; Genentech: Research Funding.

Description: Innate immune receptors like pattern recognition receptors (PRRs) including toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD) like-receptors (NLR) on immune cells play an important role in initiating inflammatory responses to damage- and pathogen- associated molecular patterns (DAMPs and PAMPs) expressed on invading pathogens or released from damaged cells. Although it is well known that DAMPs directly modulate innate immune functions, it is less clear whether DAMPs directly regulate T cell intrinsic function. Members of the sialic acid binding Ig-like lectin (Siglec) family have immunoreceptor tyrosine-based inhibitory motifs (ITIM) or ITIM-like regions in their intracellular domain that negatively regulate immune activation induced by DAMPs. Our previous data suggested that the Siglec- G-CD24 interaction in host APCs plays an important role in the negative regulation of graft-versus host (GVH) responses. However, the T cell autonomous role of Siglec-G in the regulation of T cell responses is not known. Because Siglecs are important negative regulators of immune responses, we tested the hypothesis that the deficiency of Siglec-G in donor T cells would enhance GVHD. To test our hypothesis, we first examined detailed phenotypic analysis of various T cell subsets and activation markers in naïve Siglec-G-/- and wild-type (WT) B6 animals and found similar distribution of naïve, memory, effector and regulatory T cells. In order to examine whether the absence of Siglec-G in donors affects GVHD, WT-BALB/cmice were lethally irradiated (850cGy) and transplanted on day 0 with 5x106 bone marrow and 0.5x106 splenic CD90+ T cells from either syngeneic WT-BALB/c, allogeneic MHC-mismatched WT-B6 or Siglec-G-/- animals. The recipients receiving donor T cells from Siglec-G-/- animals showed a significantly worse survival compared to allogeneic WT-B6 animals (p

Description: Introduction: Therapy related myelodysplastic syndrome (t-MDS) and acute myeloid leukemia (t-AML) are significant long-term complications of MM treatment. We have treated pts on standard therapy protocols including TT2, TT3, TT4 and TT5. These protocols include an induction, tandem melphalan-based ASCT and consolidation, followed by three years of maintenance. As a part of the protocols, multiple bone marrow examinations including metaphase cytogenetics are performed at regular intervals, giving us the unique opportunity to examine the development of t-MDS/t-AML and understand the efficacy of subsequent treatment. Here we investigate the outcome of t-AML and t-MDS treated with autologous stem cell transplantation (ASCT) in MM patients. Materials and Methods, Results: During the period between 1998 to 2015, a total of 1558 pts were treated for MM with standard therapy protocols. We identified 68 pts out of 1558 who developed t-AML + t-MDS. Thirty-one had a confirmed diagnosis of t-AML, and thirty-seven had a diagnosis of t-MDS. The median age at diagnosis was 60 years (range 45-76). The median time from diagnosis MM of t-AML and t-MDS was 66 months (range, 9.6-155.4) and 63 months (range, 8-130), respectively. Baseline cytogenetics were as follows: complex cytogenetics in 34 pts out of 68, del(7) in 24 pts, del(5) in 17 pts, and del(17p) in 5 pts. Eighteen out of thirty-one t-AML pts were treated with ASCT. The remaining 13 pts did not receive ASCT. The treatment related mortality (TRM) at day100 (D100) in the ASCT group was 33% (6/18 pts). Neutrophil and platelet engraftment was achieved in all 18 pts by D21. Complete remission was achieved in 50% (9 out of 18) of pts. When we compared pts who received ASCT to those who were treated with chemotherapy only, the median overall survival (OS) was 11.28 months after ASCT vs 1.32 months without ASCT (p 〈 0.05). Nineteen out of thirty seven t-MDS pts were treated with ASCT. When we compared pts who received ASCT to chemotherapy only for t-MDS, there was no difference in survival between the groups. A mortality rate of 47% (9/19) was recorded at D200 after transplantation due to severe infections and lack of engraftment. Conclusion: t-AML and t-MDS treatment is a significant therapeutic challenge for the elderly, who often have poor risk cytogenetic markers, significant comorbidities and a compromised performance status. In our case series of post MM therapy t-AML, ASCT prolonged survival. In contrast, there was no change in survival of t-MDS pts, most likely due to high rate of infectious complications seen in this group. To our knowledge, this is the first analysis suggesting a survival benefit from ASCT in treating t-AML. Although the numbers in our study are small, we recommend that ASCT can be safely considered for t-AML patients who are physically fit, have autologous stem cells in storage and are overseen by a good supportive care team. These results need to be validated in large prospective studies. Disclosures Atrash: University of Arkansas for Medical Sciences: Employment. Barlogie:Millennium: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; European School of Haematology- International Conference on Multiple Myeloma: Other: Travel Stipend; ComtecMed- World Congress on Controversies in Hematology: Other: Travel Stipend; International Workshop on Waldenström's Macroglobulinemia: Other: Travel Stipend; Dana Farber Cancer Institute: Other: Travel Stipend; Multiple Myeloma Research Foundation: Other: Travel Stipend; Myeloma Health, LLC: Patents & Royalties: Co-inventor of patents and patent applications related to use of GEP in cancer medicine licensed to Myeloma Health, LLC. Zangari:Onyx: Research Funding; Novartis: Research Funding; Millennium: Research Funding; University of Arkansas for Medical Sciences: Employment. van Rhee:University of Arkansa for Medical Sciences: Employment. Waheed:University of Arkansas for Medical Sciences: Employment. Bailey:University of Arkansas for Medical Sciences: Employment. Petty:University of Arkansas for Medical Sciences: Employment. Heuck:Celgene: Consultancy; Janssen: Other: Advisory Board; Millenium: Other: Advisory Board; Foundation Medicine: Honoraria; University of Arkansas for Medical Sciences: Employment. Morgan:Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; MMRF: Honoraria; Weismann Institute: Honoraria; CancerNet: Honoraria; University of Arkansas for Medical Sciences: Employment; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Jethava:University of Arkansas for Medical Sciences: Employment.

Description: Background & Hypothesis: IFITM3 (Interferon-induced transmembrane protein 3) also known as CD225/Leu-13 was identified as interferon-inducible molecule in the context of viral infection. IFITM3 encodes a surface receptor, basally expressed on the plasma membrane, that is associated with known B cell co-receptors including CD19, CD81 and CD21. Recent immunotherapy approaches based on CD19-specific engineered chimeric antigen receptors (CART19) have achieved spectacular successes in eliminating pre-B ALL cells based on surface expression of CD19 (Grupp et al., 2013). However, in some cases, CART19 treatment was followed by ALL relapse developing from clones that lacked CD19 surface expression. Therefore, we studied factors that regulate CD19 surface expression on human pre-B ALL cells. Results: Studying IFITM3 mRNA levels in ALL cells at the time of diagnosis in clinical trials for childhood (COG P9906) and adult ALL (ECOG E2993), we found that higher than median expression levels of IFITM3 predicted shorter overall and relapse-free survival (P=0.014). In addition, patients with higher than median IFITM3 mRNA levels at the time of diagnosis were significantly more likely to experience ALL relapse and had a higher risk of a positive MRD status at the end of induction chemotherapy. To study the function of Ifitm3 in a model for human pre-B ALL, pre-B cells from Ifitm3-/- mice were transformed with BCR-ABL1. Strikingly, deletion of IFITM3 resulted in loss of CD19 expression on the surface of normal and leukemic pre-B cells. Besides loss of surface expression, loss of Ifitm3 also caused impaired phosphorylation of CD19-Y513, which mediates downstream activation of PI3K-AKT signaling in both B cell progenitors and pre-B ALL cells. These changes were paralleled by G0/1 cell cycle arrest (P

Description: Background: Mitogen activated protein kinase (MAPK) pathway is activated in myeloid malignancies both mutationally and non-mutationally. Most frequent mutations are encountered in RAS genes. While direct inhibition of RAS has been elusive, MEK inhibition downstream of RAS is a viable alternative. Trametinib is an allosteric MEK 1/2 inhibitor with pre-clinical activity against multiple cell lines representative of myeloid malignancies. A Phase 1/2 trial in relapsed/refractory acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML) involving 97 patients showed remissions with or without recovery of counts in 20% of patients harboring mutations in RAS oncogenes. Methods: As responses were only seen among patients with RAS mutations, in collaboration with the Sheikh Khalifa Bin Zayed Al Nahyan Institute for Personalized Cancer Therapy (IPCT) at MD Anderson Cancer Center, we undertook sequencing of DNA extracted from bone marrow samples of 6 responders and 10 non-responders (all with RAS mutation) before treatment on a next generation sequencing (NGS) platform of 202 cancer-relevant genes All of these patients also had at least one follow up bone marrow sample collected during treatment or at loss of response. Results: Patients were of median age of 69 years (range, 40-79) with median bone marrow blast count of 25 (range, 6-88), median WBC count of 6.1X109 /L (range, 0.4-29.3) and received a median of 2 prior therapies (range, 1-5). Cytogenetics was diploid in 6, complex/-7 in 5 patients. Fifteen of the sixteen patients had an NRAS mutation (Codon 12=9, codon 61=4, codon 13=1) and one patient had a KRAS mutation in codon 12. None carried concomitant mutation in NPM1, KIT or CEBPA genes, and one patient with an NRAS mutation also had a FLT3 D835 mutation. Median baseline RAS allelic burden was 34.4% (range, 18-73) with no difference among responders and non-responders. One non-responder lost the mutant NRAS allele at follow up but gained a FLT3 D835E mutation. There was no overall significant difference in RAS allelic burden at follow-up in non-responders or responders. The range of RAS allelic frequency change was a gain in 11% to a loss of 28% in non-responders and a 17% gain to a 20% loss in responders, for all patients with data collected before and after treatment. Median baseline frequency of mutations or identified copy number changes was 7.25, including both responders (range, 4-16) and non-responders (range, 4-10). Before the start of treatment, 70% of the non-responders had additional mutations in genes encoding epigenetic regulators e.g. MLL2, SETD2, TET2, IDH1 or 2 etc. , compared with only 33% of responders (Fig.1). Of the 7 non-responders with mutations in an epigenetic regulator, we obtained data at follow-up on 6 patients. Each of these 6 patients retained the mutation at follow-up and an additional non-responder gained a mutation in an epigenetic regulator at follow-up. Interestingly 100% of responders had at least one mutation in a gene encoding a member of the cellular matrix and/or involved in cellular adhesion e.g. CSMD1, CSMD3, FLG, USH2A etc. before treatment, compared with only 50% of non-responders. This trend also persisted after treatment, with only one responder losing such a mutation. Conclusion: Mutation analysis in a subset of patients with RAS mutations and myeloid malignancies treated with trametinib suggest presence of higher frequency of epigenetic mutations among non-responders. Further study is needed to determine whether the combination of MEK 1/2 inhibitor with epigenetic therapy may improve outcomes. Figure 1. Figure 1. Disclosures Cortes: Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Teva: Research Funding; BerGenBio AS: Research Funding; Ariad: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Ambit: Consultancy, Research Funding; Arog: Research Funding; Celator: Research Funding; Jenssen: Consultancy. Jabbour:Pfizer: Consultancy, Research Funding.