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Background: TP53 mutations in acute myeloid leukemia (AML) are associated with complex karyotype, high incidence of minimal residual disease (MRD), and high risk of relapse (Döhner et al., 2017; Giacomelli et al., 2018). While numerous novel treatment regimens, including the combination of the BCL2 inhibitor venetoclax (VEN) and hypomethylating agents (HMA), have emerged as partially effective treatments and resulted in higher remission rates in patients with TP53-mutant AML, full clearance of the mutant TP53 clone is rarely achieved and the majority of patients relapse (Short et al., 2021; Takahashi et al., 2016). The mechanisms responsible for response and relapse in TP53-mutant AML remain unclear and investigating novel mechanisms is critical to develop more effective therapies. Results: In order to shed light on the defective p53 signaling pathways underlying TP53 mutant AML, and to better understand mechanisms of resistance, we performed RNA-sequencing (RNA-seq) on FACS-sorted subpopulations using samples collected from TP53-mutant or TP53-wt high-risk AML patients. Samples were collected at diagnosis (DX) and post-treatment (POSTTX) (total number of samples n= 67, TP53-mutant=36, TP53-wt=31). Diagnostic samples include bulk AML, leukemic stem cells (LSCs), and post-treatment samples including bulk mononuclear cells (MNCS) and patient specific MRD (total n= 67, DX_Bulk=15, DX_LSCs=15, POSTTX_MNCs=14, POSTTX_MRD=23). Differential gene expression analysis of TP53-mutant samples indicates a positive enrichment of the following pathways: G2/M checkpoint, MYC targets, and mitotic spindle, among others. We focused here on genes associated with TP53-mutant AML enriched pathways, and identified a key regulator of centriole biogenesis, one of E2F targets: Polo-like kinase 4 (PLK4) as a potential target highly expressed in TP53-mutant AML samples . Previous publications showed that PLK4 is transcriptionally repressed by p53 and induces apoptosis upon RNAi silencing (Fischer et al., 2014; Li et al., 2005). Here we show that TP53-mutant AML samples lack the p53-dependent PLK4 repression and have higher levels of PLK4 compared to TP53-wt AML. To test the rigor of this finding, we interrogated the Munich Leukemia Laboratory (MLL) data base and analyzed their clinically annotated (e.g. karyotype, survival, complete blood counts, previous treatments ... etc) RNA-seq dataset of 726 AML samples (TP53-mutant=72, TP53-wt=654). TP53-mutant AML samples consistently showed significant PLK4 upregulation (p= 0.0003). We analyzed PLK4 expression and its correlation with TP53 mutations in The Cancer Dependency Map project dataset (1375 cell lines in 35 different types of cancers) (p= 0.004). Furthermore, we found significantly higher PLK4 protein levels in TP53-mutant AML MOLM13 cell lines when compared with syngeneic TP53-wt AML MOLM13 cells. Experimentally, we found that PLK4 inhibition using 25nM CFI-400945 in TP53-mutant AML MOLM13 cell lines triggers polyploidy > 2-fold higher than in TP53-wt AML MOLM13 cell lines 72 hours post treatment (Fig.1A p< 0.0001). Finally, we show that polyploidy is not reversible after drug removal and results in significantly increased levels of apoptotic cell death in TP53-mutant AML MOLM13 cells (Fig.1B). Conclusion: Our data suggest that TP53-mutant AML expresses higher levels of PLK4 in comparison to TP53-wt AML, and targeting PLK4 triggers polyploidy and apoptotic cell death in TP53-mutant AML. A clinical trial is ongoing testing the efficacy of PLK4 inhibition (CFI-400945) in AML (Clinical Trial ID: NCT04730258, TWT-202). Figure 1 Figure 1. Disclosures Issa: Kura Oncology: Consultancy, Research Funding; Syndax Pharmaceuticals: Research Funding; Novartis: Consultancy, Research Funding. Borthakur: Takeda: Membership on an entity's Board of Directors or advisory committees; ArgenX: Membership on an entity's Board of Directors or advisory committees; Ryvu: Research Funding; Astex: Research Funding; University of Texas MD Anderson Cancer Center: Current Employment; Protagonist: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy. Konopleva: Ascentage: Other: grant support, Research Funding; Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights; Stemline Therapeutics: Research Funding; KisoJi: Research Funding; Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding; Sanofi: Other: grant support, Research Funding; AstraZeneca: Other: grant support, Research Funding; Ablynx: Other: grant support, Research Funding; AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support; Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights; Rafael Pharmaceuticals: Other: grant support, Research Funding; Genentech: Consultancy, Honoraria, Other: grant support, Research Funding; Cellectis: Other: grant support; Calithera: Other: grant support, Research Funding; Agios: Other: grant support, Research Funding; Forty Seven: Other: grant support, Research Funding. Haferlach: MLL Munich Leukemia Laboratory: Other: Part ownership. Andreeff: Senti-Bio: Consultancy; ONO Pharmaceuticals: Research Funding; Glycomimetics: Consultancy; Aptose: Consultancy; Breast Cancer Research Foundation: Research Funding; Oxford Biomedica UK: Research Funding; Karyopharm: Research Funding; Medicxi: Consultancy; Amgen: Research Funding; AstraZeneca: Research Funding; Daiichi-Sankyo: Consultancy, Research Funding; Syndax: Consultancy; Novartis, Cancer UK; Leukemia & Lymphoma Society (LLS), German Research Council; NCI-RDCRN (Rare Disease Clin Network), CLL Foundation; Novartis: Membership on an entity's Board of Directors or advisory committees; Reata, Aptose, Eutropics, SentiBio; Chimerix, Oncolyze: Current holder of individual stocks in a privately-held company.

Introduction : Vodobatinib is a novel third generation TKI effective against wild-type and mutated BCR-ABL1 (except T315I) with limited off-target activity. We present updated results from the Phase 1 dose-escalation (DEs) and expansion (DEx) study in CML and Ph+ALL patients (pts) failing ≥ 3 prior TKIs (< 3 prior TKIs if approved TKI is not clinically advised or available); patients with T315I are not eligible (NCT02629692). Methods: This is an open-label, phase 1, multicentre, 3+3 study evaluating maximum tolerated dose (MTD), safety and efficacy of vodobatinib administered once daily in 28 day cycles (dose range: 12 to 240 mg). MTD was established at 204 mg. DEx study enrolled chronic phase CML (CP-CML) patients at 174 mg dose of vodobatinib. Treatment continued until unacceptable toxicity, disease progression, consent withdrawal or death. Adverse events were assessed using NCI-CTCAE v4.03. Results: As of 15 Jul 2021, 52 pts are enrolled in DEs and DEx cohorts. Forty one of these pts received doses from 12 to 240 mg in the DEs cohort;32 chronic phase (CP-CML), 3 accelerated phase CML (AP-CML), 4 blast phase CML (BP-CML), 2 Ph+ ALL. Eleven CP-CML pts were enrolled in DEx cohort at 174 mg dose. The baseline demographics and disease history are represented in Table 1. Efficacy : Of the 32 CP-CML pts enrolled in DEs: At baseline, 21 (65%) pts had no cytogenetic response, 4 (12.5%) were in PCyR, 7 (22%) were in CCyR. On vodobatinib therapy, 11(34%) pts achieved CCyR, 3 (9%) achieved PCyR and 7 (22%) maintained baseline CCyR. Baseline major molecular response (MMR) was present in 1 (3%) pt; and 14 pts (44%) achieved MMR on study. Of the remaining 11 pts, 5 (16%) had haematologically stable disease (no CyR and molecular response) and 6 (19%) had disease progression (cytogenetic or hematological) as their best response (Table 2 and 3). Seventeen CP-CML pts had prior ponatinib treatment, of which 11 (65%) had MCyR (4 achieved CCyR, 4 maintained CCyR, 3 achieved PCyR); while 8 (47%) achieved MMR. In the remaining 15 pts ponatinib naïve CP-CML: 10 (66%) had CCyR (7 achieved CCyR, 3 maintained CCyR); with 7 (47%) with MMR (6 achieved, 1 maintained). Two of the 3, AP-CML pts had baseline hematological response (CHR) with absence of cytogenetic and molecular response. The 3 pts further deepened their responses with 1 pt achieving CCyR with MMR and 2 pts in PCyR. Of the 4 BP-CML pts, 2 achieved CHR and 2 patients had disease progression as their best response; Of the 2 Ph+ ALL pts, 1 pt maintained CCyR and MMR while the other reported disease progression as the best response. Median duration of treatment overall was 23 (0.5-51) months [CP-CML 23 (0.5-51); AP-CML 36 (9-40); BP-CML 3 (0.5-18) and Ph+ ALL 4 (0.7-7.3) months]. Twenty one pts continue in study. In the DEx cohort, 1 of the 11 CP-CML pts was in PCyR at baseline. No pts had molecular response. Of the 11 patients, 6 (54 %) pts achieved CCyR, 1(10%) pt achieved PCyR. MMR was achieved by 1 pt (10%). Data is maturing for 1 pt. Median duration of treatment is 16 (0.3-19) months and 10 pts continue in study. Safety : Forty nine of 52 pts reported at least 1 TEAE. Most common any grade TEAEs included thrombocytopenia (33%), cough (19%), anaemia & diarrhoea (17% each). Thirty one pts (60%) reported Grade 3 and 4 treatment emergent AEs: most common were thrombocytopenia (15%), neutropenia and anaemia (12%), increased amylase and lipase (8% each). Ten (19%) pts reported cardiovascular TEAEs (Grade 1: angina pectoris, palpitations, ventricular extra-systoles, arteriosclerosis, hot flush, hypotension, intermittent claudication; Grade 2: hypertension, hypotension; Grade 3: cardiac failure congestive, hypertension); with a Grade 2 hypertension being vodobatinib related. Nineteen pts (37%) reported SAEs; vodobatinib related SAEs were reported in 3 pts (fatal intracranial haemorrhage (ICH), Grade 2 back pain and Grade 3 amnesia reported in 1 pt each). There were 5 deaths on study: 1 was related to use of vodobatinib (1 ICH, confounded by disease progression to blast phase that included extra- medullary sites) and the remaining unrelated (1 sudden death, 1 disease progression, 1 pneumonia fungal, 1 suspected COVID-19). Conclusion: Vodobatinib continues to be associated with favourable long term safety and efficacy in heavily pre-treated CML failing ≥ 3 prior TKIs, including ponatinib. Phase 2 study evaluating vodobatinib in pts failing at least 3 prior lines of therapy, including ponatinib, is ongoing. Figure 1 Figure 1. Disclosures Cortes: Novartis: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Bristol Myers Squibb, Daiichi Sankyo, Jazz Pharmaceuticals, Astellas, Novartis, Pfizer, Takeda, BioPath Holdings, Incyte: Consultancy, Research Funding; Bio-Path Holdings, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sun Pharma: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding. Kim: Novartis: Research Funding; BMS: Research Funding; Pfizer: Research Funding; ILYANG: Research Funding; Takeda: Research Funding. Alvarado: MEI Pharma: Research Funding; Daiichi-Sankyo: Research Funding; Sun Pharma: Consultancy, Research Funding; CytomX Therapeutics: Consultancy; Jazz Pharmaceuticals: Research Funding; BerGenBio: Research Funding; Astex Pharmaceuticals: Research Funding; FibroGen: Research Funding. Nicolini: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel, accommodations, expenses, Research Funding; Incyte Biosciences: Honoraria, Other: travel, accommodations, expenses, Research Funding, Speakers Bureau; BMS: Honoraria; Sun Pharma Ltd.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kartos Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Apperley: Incyte, Pfizer: Honoraria, Research Funding, Speakers Bureau; Bristol Myers Squibb, Novartis: Honoraria, Speakers Bureau. Deininger: Fusion Pharma, Medscape, DisperSol: Consultancy; Novartis: Consultancy, Research Funding; SPARC, DisperSol, Leukemia & Lymphoma Society: Research Funding; Incyte: Consultancy, Honoraria, Research Funding; Blueprint Medicines Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Part of a Study Management Committee, Research Funding; Sangamo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Part of a Study Management Committee, Research Funding. de Lavallade: Bristol Myers Squibb: Research Funding; Incyte: Honoraria, Research Funding; Novartis: Speakers Bureau. Charbonnier: Novartis: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Gambacorti-Passerini: Pfizer: Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy. Mauro: Novartis: Consultancy, Research Funding; Takeda: Consultancy; Pfizer: Consultancy; Sun Pharma / SPARC: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding. Vandenberghe: Pfizer: Research Funding; Bristol Myers Squibb/Celgene: Consultancy; Miltenyi Biotec: Consultancy; Novartis: Consultancy; Janssen: Consultancy, Research Funding; Kite, a Gilead Company: Consultancy; Gilead Sciences: Consultancy, Other: Travel support. Radhakrishnan: Intas Pharmaceuticals: Research Funding; Emcure Pharmaceuticals: Research Funding; Dr Reddy's Laboratories: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen India: Honoraria; Cipla Pharmaceuticals India: Research Funding; Bristol-Myers-Squibb India: Membership on an entity's Board of Directors or advisory committees, Research Funding; Aurigene: Speakers Bureau; AstraZeneca India: Honoraria, Speakers Bureau; NATCO Pharmaceuticals: Research Funding; Novartis India: Membership on an entity's Board of Directors or advisory committees; Roche India: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Yao: Sun Pharma: Current Employment. Inamdar: Sun Pharma Advanced Research Company: Current Employment. Sreenivasan: Sun Pharma Advanced Research Company: Current Employment. Dillu: Sun Pharma Advanced Research Company: Current Employment. Chimote: Sun Pharma Advanced Research Company: Current Employment.

Introduction Acute graft versus host disease (aGVHD) is an important complication of allogeneic hematopoietic stem cell transplant (AHSCT). Steroid refractory (SR) aGVHD is seen in about 40- 50% of patients with no recommended standard of care. We report our experience with etanercept (ETA) as the initial agent in SR aGVHD. Materials and Methods We retrospectively analysed 43 AHSCT patients from 2010 to 2019 who received ETA as initial agent for SR aGVHD amongst 311 patients who underwent AHSCT in the same period. Patients received myeloablative (MAC) or reduced intensity conditioning (RIC). The transplants were from matched sibling donor (MSD), matched unrelated donor (MUD) and haploidentical donor (Haplo). GVHD prophylaxis was calcineurin inhibitor (CNI) plus methotrexate (MTX)/ mycophenolate mofetil (MMF) in MSD/MUD. Rabbit ATG (2.5-5 mg/kg) was used for MUD. Haplo transplant patients received post-transplant cyclophosphamide (PTCy) with CNI and MMF. aGVHD was graded as per the modified Glucksberg criteria. Additionally, all aGVHD episodes were also classified as per the Minnesota Scoring into High Risk (HR) and Standard Risk (sr) GVHD. First line treatment of aGVHD Grade II-IV was systemic steroids with methylprednisolone 1-2 mg/kg/day. SR aGVHD was defined as per standard criteria. ETA was started as 25 mg (0.4 mg/kg in children) subcutaneously every 72 hours initially and was tapered gradually depending on response. Response of SR aGVHD to ETA was defined as follows:Complete response (CR) was the complete resolution of aGVHD manifestations in all organs. Partial response (PR) was improvement in GVHD stage in at least 1 of the initially involved organs without CR and worsening in any other organs. Very good partial response (VGPR) was improvement in GVHD in all initial organs, with maximum stage I involvement in 1 or more organs (except upper gut). No response (NR)/Progression/Failure of therapy was defined as same grade or progression of GVHD in any organ or the addition of further GVHD therapy beyond ETA. Death prior to 1st response assessment was taken as NR. Response assessment was done at 3 time points - Day 14, Day 28 and Day 56 after initiation of ETA. Reduction of initial systemic steroid dose by ≥30% from baseline on day 28 after start of ETA was analysed as a subgroup to assess outcomes of patients. Results The characteristics of all 43 patients are shown in Table 1. ETA was required in a total of 45 episodes in 43 patients. The overall grade of GVHD and organs involved at the start of first line treatment are as in Table 2. The median day of onset of acute GVHD was 58 days (range 8-738 days). The median day of start of ETA was 86 days (range 16-74 days). The median number of days steroid was given prior to start of ETA was 7 days. The median number of ETA doses given were 11 (range 2-25). Response assessment on the predetermined time points are as in Table 2. The response rates (CR+VGPR+PR) at Day 14, Day 28 and Day 56 were 62%, 69% and 64% respectively. The organ specific response rates (CR+VGPR+PR) were 70% for lower gut, 67% for skin and 50% for liver. A third line agent for aGVHD was added in 10 patients, which included ruxolitinib, cyclosporine, mycophenolate mofetil, basiliximab or low dose weekly cyclophosphamide. The median OS of the whole cohort of SR aGVHD was 5.2 months. The median OS of the responders (CR+PR+VGPR) at Day 28 from ETA start was 6.8 months versus 2.8 months (p=0.0003) in non-responders (Fig 1). The median OS of sr group of Minnesota Grading was 24 months versus 10 months in HR group (p=0.085) (Fig 2). Patients, in whom reduction in the systemic steroid dose ≥ 30% at Day 28 from start of ETA was possible, had a significantly better median OS (9.5 months versus 3.5 months; p=0.000021) (Fig 3). In multivariate analysis, steroid dose reduction on day 28 of start of ETA was the most significant factor (p=0.008; hazard ratio 3.33; CI 1.3-8.1) CMV reactivation was seen in 64% of the patients. Fungal infections in 51% and bacterial infections in 78% patients after start of ETA. The causes of death were infection in 25 (58%) patients, refractory GVHD in 8 (18%), combination of GVHD and infection in 2 (5%) and relapse in 4 (9%) patients. Conclusion ETA used as initial agent has shown acceptable response rates for SR aGVHD in our cohort, especially for lower gut and skin. However, infections were the major cause for mortality for this cohort and early tapering of systemic steroids may be the key to improving outcomes. Disclosures No relevant conflicts of interest to declare.

Introduction Outcomes of patients (pts) with relapsed hematological malignancies post allogeneic stem cell transplant (ASCT) are dismal. Donor lymphocyte infusion (DLI) is one of the treatment options; however outcomes with DLI are also poor especially in acute leukemias. Addition of immunomodulatory drugs to DLI may augment graft-versus-leukemia effect and may improve outcomes. Lenalidomide (len) is an immunomodulatory drug and has several effects on the immune system. Addition of len to DLI has been variably practiced at our centre. In this study, we retrospectively compare the outcomes of DLI with or without len. Methods All pts who received DLI from January 2010 to January 2020 were included in this retrospective analysis. No immunosuppressant prophylaxis was administered and ongoing immunosuppression (if any) was stopped prior to DLI. DLI was defined as therapeutic if it was given for hematological relapse (with or without cytoreductive chemotherapy); pre-emptive if there was cytogenetic / flow cytometric / molecular relapse or slipping chimerism. DLI was prophylactic if it was given to prevent a relapse in the absence of any of the above features. Len was given on a continuous schedule at a starting dose of 2.5-25 mg/day. Len was started along with 1st or subsequent DLI as per discretion of treating clinician. For the purpose of this study, pts were divided into two groups - those who received DLI alone (no len group) versus those who received DLI with len (len group). In both groups, cytoreductive chemotherapy was given for some pts with hematological relapse at discretion of treating physician. Event free and overall survival were calculated from the date of 1st DLI. Event was defined as hematological relapse / progression or death. Complete response (CR) was defined as attainment of full donor chimerism in those with chimerism slippage; attainment of cytogenetic/ flow/molecular negativity in those with any of these positive at time of DLI; attainment of morphological remission in those with hematologic relapse. The primary objective was to compare the overall survival (OS) in no len group versus len group. Secondary endpoints were event free survival (EFS), CR rates, grade II-IV acute GVHD, len related toxicities and therapy related mortality. Patient and donor age, gender, diagnosis, type of ASCT, disease risk index (DRI), time to relapse (or slipping chimerism), type of DLI, pre-DLI morphological disease status, and HLA-A*24 or B*40 in pts were evaluated as factors affecting outcomes with or without len. (HLA-A*24 and B*40 were selected because of prior data from our institute showing benefit of len in pts with AML who had these alleles.) Statistical analysis was done using standard methods. Survival was assessed by Kaplan Meier method. All p values were 2 sided; p value of Results Total 61 pts received DLI. Table 1 shows the baseline characteristics, transplant details, & details of DLI & len. The 2 groups were comparable in all aspects except for younger age in len group. Median OS (Fig 1a) and EFS (Fig 1b) were not different in len vs no len group (11 vs 8 months, p=0.66 and 6 vs 2 months, p=0.42). Len was not associated with improvement in OS in pts with myeloid malignancies (n=47, median OS 8 vs 3 months, p=0.80) or in AML pts (n=25, median OS 9 months vs 2 months, p=0.47). Among pts with HLA-A*24 or B*40 (n=26), there was an improvement in OS (median not reached vs 8 months, 4 year OS 62% vs 32%, p=0.1) (Fig 1c) and EFS (median 9 vs 1 month, 4 year EFS 50% vs 22%, p=0.1) (Fig 1d) with len. In this subgroup, hazard ratio for both OS and EFS was 0.47 (Fig 1e and 1f respectively). 49 pts had measurable disease / slipped chimerism at DLI. Among these, CR rate was not different between the 2 groups (41% vs 40% with len, p=0.9). Median time to CR was similar (31 vs 38 days, p= 0.36). Post DLI acute grade II-IV GVHD developed in 8 (19%) in no len group vs 4 (22%) in len group respectively, p=0.75. Median duration of len was 36 days. In the len group, 17 discontinued len; 8 (44%) due to disease progression, 5 (28%) due to GVHD, 3 (17%) due to cytopenias and 1 due to unrelated cause. Death due to DLI related GVHD was seen in 1 (6%) and 4 (9%) in len and no len group respectively, p=0.6. Conclusions There was no difference in outcomes in patients who received DLI with or without len. However, in subset of patients who had HLA*24 or B*40, an improvement in OS and EFS was seen. The relation of above HLA alleles with len needs further exploration. Disclosures No relevant conflicts of interest to declare. OffLabel Disclosure: This abstract discusses the use of lenalidomide as an immunomodulatory drug to enhance the graft versus leukemia effect of donor lymphocyte infusions for hematological malignancies post allogeneic transplant.

Introduction The monitoring of a patient's response to chemotherapy, called, measurable residual disease (MRD) is one of the most important predictors of outcome in Acute Myeloid Leukemia (AML). Although universally applicable, FCM-MRD for AML suffers from low sensitivity as compared to precursor B lineage acute lymphoblastic leukemia. Here, we evaluated the clinical utility of error corrected next generation sequencing (NGS) to detect MRD (NGS-MRD) in AML using single molecule molecular inversion probes (smMIPS). We compare NGS-MRD and FCM-MRD and determine their impact on patient outcome. We demonstrate that error corrected NGS-MRD at early timepoints in therapy is an independent and significant predictor of outcome in patients of AML treated with conventional therapies. Methods We created a 35 gene "hotspot" panel comprising of a pool of 302 smMIPS. In brief, this panel covers regions of 35 commonly mutated genes in AML.FLT3-ITD were detected using a novel one-step PCR based NGS assay. Post mapping, singleton reads (originating from one UMI) were discarded and consensus family based variant calling was performed. We then created a site and mutation specific error model to ascertain the relevance of an observed variant at each site. A limit of detection (LOD) experiment demonstrated a lower detection limit of 0.05%. For FLT3-ITD the LOD was 0.002%. A total of 393 adult patients of AMLwere accrued over a period of six years.Patients were treated with standard 3+7 induction followed by 3 doses of HiDAC. Allogeneic bone marrow transplantation was offered where feasible. Somatic mutations at diagnosis were evaluated using a smMIPS based 50 gene myeloid panel which was applicable to 327 patients [83.2% of AMLs, median 2 mutations per case (range 1 - 6 trackable mutations)].MRD assessment could be performed in 201 adult patients of AML in morphological remission (not performed in the rest because of suboptimal quality DNA at MRD time points or missing sample).Samples were sequenced on multiple S4 flow cells of a NovaSeq 6000 using 150PE chemistry.FCM-MRD was obtained from the bone marrow at end of induction (PI, n=200) and end of first consolidation cycle (PC, n=98). NGS-MRD sample also obtained at the same time points (PI, n=196& PC, n=127) from the bone marrow (n=266) or peripheral blood (n=45). Results The interaction of mutations that were trackable at diagnosis can be seen in Figure 1A. A total of 345 mutations could be detected in 196 patients (Figure 1B) with a median VAF of 1.01% [0.82% after exclusion of mutations in DNMT3A, TET2, ASXL1 (DTA) genes; (median of 2 mutations for PI and one for PC timepoint)]. The median consensus read coverage was 11,127 for the smMIPS assay, whereas for the FLT3-ITD assay it was 13,96,366.The median follow-up of the cohort was 42.3 months. The presence of NGS-MRD (70.9%) was associated with inferior overall survival (OS; p=0.001) [hazard ratio(HR)- 2.24; 95% confidence interval (CI)- 1.47 to 3.43] and relapse free survival (RFS; p=0.0002) [HR- 2.28; 95% CI- 1.58 to 3.31] at PI time point as well as PC time points [40.94% positive; OS (p=0.008)(HR- 1.92; 95% CI- 1.14 to 3.22) and RFS (p=0.004)(HR- 1.90; 95% CI- 1.18 to 3.05)].Similarly, FCM-MRD (44%) was predictive of inferior OS (p=0.0002)(HR- 2.08; 95% CI- 1.38 to 3.13)and RFS (p=0.0008)(HR- 1.81; 95% CI- 1.26 to 2.60) at PI as well as PC time points [21.4% positive, OS (p=0.04)(HR- 1.87; 95% CI- 0.89 to 3.91) and RFS (p=0.001)(HR- 2.38; 95% CI- 1.17 to 4.81)]. On multivariate analysis post induction NGS MRD emerged as the most important independent prognostic factor predictive of inferior outcome for OS [HR- 1.94; 95% CI-1.15 to 3.27; (p Conclusion In conclusion, we demonstrate that error corrected panel-based sequencing is feasible for MRD monitoring in AML and may offer an advantage over existing techniques. Maximum clinical utility may be leveraged by combining FCM and NGS modalities. Figure Disclosures No relevant conflicts of interest to declare.

Introduction : There has been an increase in number of alternative donor [Unrelated donor (UD) or Haploidentical (HIT)] transplants in recent years due to better graft vs. host disease (GVHD) prophylaxis and comparable outcomes with matched sibling transplants. However, viral reactivations frequently complicate these transplants and can lead to organ dysfunction, poor graft function and death. We aimed to analyze incidence, risk factors, and outcomes of viral reactivations in alternative donor transplants at our centre. Methods: All UD or HIT transplants performed between January 1st 2009 and February 29th 2020 were included in this retrospective analysis. Conditioning regimen used were either myeloablative (TBI based) or reduced intensity (fludarabine based). All patients received T cell replete grafts. Calcineurin inhibitors (with methotrexate or mycophenolate mofetil) were used for GVHD prophylaxis. Rabbit anti-thymocyte globulin (ATG) was used in UD transplants and post transplant cyclophosphamide was used in HIT. Cytomegalovirus (CMV) was monitored twice weekly from start of conditioning. Adenovirus (ADV), BK, Epstein Barr virus (EBV) were monitored weekly post engraftment. Monitoring was done by real time quantitative PCR in peripheral blood for CMV, EBV and in blood as well as urine for ADV and BK virus. Parvovirus and Human Herpes virus-6 (HHV-6) were monitored if clinically indicated. Viral reactivation was defined as 2 consecutive readings of >150 copies/mL. Monitoring was stopped after withdrawal of immunosuppressants and restarted with onset of GVHD or use of systemic steroids. Ganciclovir (GCV) was usually preferred for pre-emptive treatment of CMV. Cidofovir (CDV), foscarnet (FOS), artesunate (ART) or leflunomide (LEF) were used when GCV failed or was myelotoxic. Cidofovir was used for ADV disease. Intravenous immunoglobulin (IVIg) prophylaxis was used in all patients. Primary objective was to estimate the incidence of viral reactivation. Secondary objectives were to explore various risk factors associated with viral reactivations and determine their strength of association using odds ratio (OR). Results: Of 334 allogeneic transplants performed during this period, 87 were alternative donor transplants (26 UD and 61 HIT). Incidence of CMV reactivation was 80.5 % (92 episodes of CMV reactivations in 70 patients). Two in UD transplant and 4 in HIT developed CMV colitis. Acute GVHD was a significant risk factor for developing CMV reactivation (OR=4.32, 95% CI 1.3-13.6; p=0.013). Pre-emptive 1st line treatment with GCV was used in 59 episodes, ART in 10, LEF in 19, CDV and FOS was used in 1 and 3 episodes each. No deaths were attributed to CMV disease. Incidence of ADV reactivation was 26% (21 episodes in 80 patients tested). Four patients developed ADV disease and were treated with CDV (ADV colitis in 2, ADV cystitis in 1, and 1 had colitis with CNS involvement) of which 2 died. Use of ATG (OR 3.5, 95% CI 1.2 - 10; p=0.03) and presence of acute GVHD (OR 7.9, 95% CI 2.5- 25; p=0.0004) were significant risk factors of ADV reactivation. EBV reactivation was seen in 25 of 68 patients tested (incidence 36.7%).Two patients developed post transplant lymphoproliferative disorder requiring therapy with rituximab, of which 1 died. One out of 15 patients tested by qualitative PCR had HHV 6 reactivation and primary graft failure. BK viral reactivation was seen in 59 of 71 tested (incidence 83.1%). Grade I and II hemorrhagic cystitis (Droller's grading system) was seen in 12 and 11 patients respectively. Foley's catheterization with bladder irrigation was used in 3 patients and intravesical GCSF was given to 1 patient. Parvovirus infection was seen in 2 of 12 patients tested, of which 1 was given IVIg. Cumulative incidence of viral reactivations is shown in Figure 1. Viral reactivation characteristics and risk factors are shown in tables 1 and 2 respectively. Median OS for the cohort of 87 patients was 52 months. There was no statistically significant impact of viral reactivations on OS. Conclusion: Incidence of CMV reactivation is high (80%) in alternative donor HSCT and acute GVHD is a significant risk factor for CMV, ADV and EBV reactivation. Use of ATG is a significant risk factor for ADV reactivation. However, rates of ADV, BK virus, and EBV reactivation requiring intervention were low. Better prophylactic strategies are necessary for prevention of CMV reactivations in alternative donor transplants. Disclosures No relevant conflicts of interest to declare.

Trauma-induced coagulopathy (TIC) manifests as a bimodal disruption of normal fibrinolysis, where at the two extremes, fibrinolytic shutdown (TICFS) places the patient at increased risk for thromboembolism and post-injury multiple organ failure, and systemic hyperfibrinolysis (TICHF) results in excessive bleeding. Plasma proteomic profiles for 65 trauma patients were used to identify changes in the patient's plasma protein profile stratifying them by risk for TIC. A strong correlation was seen between total plasma protein concentration of individual patients and the concentration of coagulation proteins within that patient, suggesting that trauma-induced coagulation may be affected through a mechanism that controls the efflux of many coagulation proteins into the plasma (Figure 1). Pathway analysis, in addition to elucidating changes in the coagulation cascade, identified several proteins that are known to be regulated by the Liver X receptor/Retinoid X receptor (LXR/RXR), suggesting that LXR/RXR-mediated activity may regulate TIC (p=9.03E-26). Validation experiments in a rat model revealed that fibrinolytic response to an LXR antagonist and/or agonist can be observed in less than 60 minutes (Figure 2). Additionally, we show through reciprocal rescue of fibrinolysis that the TIC phenotypes (TICHF and TICFS) are one continuum and are ultimately co-reversible, where the reduced LXR signaling that causes sequestration of blood factors in the liver leading to excess bleeding or induced LXR signaling that causes excess efflux leading to thrombosis can be reversed through administration of the LXR agonist or antagonist, respectively. Thus, as modulation of LXR shows co-reversibility and rapid response, induction/inhibition of the LXR pathway provides a direct and novel therapeutic intervention in severely injured patients at risk for TIC. Disclosures No relevant conflicts of interest to declare.