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Key Points Induction of Sbds deficiency in recipient BM niche cells impairs efficient engraftment of healthy donor HSC after transplantation.SBDS deficiency impairs multiple cellular signaling pathways in post-myeloablation marrow niches critical for restoration of hematopoiesis., Visual Abstract, Bone marrow (BM) niche-derived signals are critical for facilitating engraftment after hematopoietic stem cell (HSC) transplantation (HSCT). HSCT is required for restoration of hematopoiesis in patients with inherited BM failure syndromes (iBMFSs). Shwachman-Diamond syndrome (SDS) is a rare iBMFS associated with mutations in SBDS. Previous studies have demonstrated that SBDS deficiency in osteolineage niche cells causes BM dysfunction that promotes leukemia development. However, it is unknown whether BM niche defects caused by SBDS deficiency also impair efficient engraftment of healthy donor HSC after HSCT, a hypothesis that could explain morbidity noted after clinical HSCT for patients with SDS. Here, we report a mouse model with inducible Sbds deletion in hematopoietic and osteolineage cells. Primary and secondary BM transplantation (BMT) studies demonstrated that SBDS deficiency within BM niches caused poor donor hematopoietic recovery and specifically poor HSC engraftment after myeloablative BMT. We have also identified multiple molecular and cellular defects within niche populations that are driven by SBDS deficiency and are accentuated by or develop specifically after myeloablative conditioning. These abnormalities include altered frequencies of multiple niche cell subsets, including mesenchymal lineage cells, macrophages, and endothelial cells; disruption of growth factor signaling, chemokine pathway activation, and adhesion molecule expression; and p53 pathway activation and signals involved in cell cycle arrest. Taken together, this study demonstrates that SBDS deficiency profoundly impacts recipient hematopoietic niche function in the setting of HSCT, suggesting that novel therapeutic strategies targeting host niches could improve clinical HSCT outcomes for patients with SDS.

Acquired aplastic anemia (AA) is a life-threatening bone marrow aplasia caused by the autoimmune destruction of hematopoietic stem and progenitor cells. There are no existing diagnostic tests that definitively establish AA, and diagnosis is currently made via systematic exclusion of various alternative etiologies, including inherited bone marrow failure syndromes (IBMFSs). The exclusion of IBMFSs, which requires syndrome-specific functional and genetic testing, can substantially delay treatment. AA and IBMFSs can have mimicking clinical presentations, and their distinction has significant implications for treatment and family planning, making accurate and prompt diagnosis imperative to optimal patient outcomes. We hypothesized that AA could be distinguished from IBMFSs using 3 laboratory findings specific to the autoimmune pathogenesis of AA: paroxysmal nocturnal hemoglobinuria (PNH) clones, copy-number–neutral loss of heterozygosity in chromosome arm 6p (6p CN-LOH), and clonal T-cell receptor (TCR) γ gene (TRG) rearrangement. To test our hypothesis, we determined the prevalence of PNH, acquired 6p CN-LOH, and clonal TRG rearrangement in 454 consecutive pediatric and adult patients diagnosed with AA, IBMFSs, and other hematologic diseases. Our results indicated that PNH and acquired 6p CN-LOH clones encompassing HLA genes have ∽100% positive predictive value for AA, and they can facilitate diagnosis in approximately one-half of AA patients. In contrast, clonal TRG rearrangement is not specific for AA. Our analysis demonstrates that PNH and 6p CN-LOH clones effectively distinguish AA from IBMFSs, and both measures should be incorporated early in the diagnostic evaluation of suspected AA using the included Bayesian nomogram to inform clinical application.

Inherited bone marrow failure (IBMF) syndromes are rare blood disorders characterized by hematopoietic cell dysfunction and predisposition to hematologic malignancies. Despite advances in the understanding of molecular pathogenesis of these heterogeneous diseases, genetic variant interpretation, genotype–phenotype correlation, and outcome prognostication remain difficult. As new IBMF and other myelodysplastic syndrome (MDS) predisposition genes continue to be discovered (frequently in small kindred studies), there is an increasing need for a systematic framework to evaluate penetrance and prevalence of mutations in genes associated with IBMF phenotypes. To address this need, we analyzed population-based genomic data from >125 000 individuals in the Genome Aggregation Database for loss-of-function (LoF) variants in 100 genes associated with IBMF. LoF variants in genes associated with IBMF/MDS were present in 0.426% of individuals. Heterozygous LoF variants in genes in which haploinsufficiency is associated with IBMF/MDS were identified in 0.422% of the population; homozygous LoF variants associated with autosomal recessive IBMF/MDS diseases were identified in only .004% of the cohort. Using age distribution of LoF variants and 2 measures of mutational constraint, LOEUF (“loss-of-function observed/expected upper bound fraction”) and pLI (“probability of being loss-of-function intolerance”), we evaluated the pathogenicity, tolerance, and age-related penetrance of LoF mutations in specific genes associated with IBMF syndromes. This analysis led to insights into rare IBMF diseases, including syndromes associated with DHX34, MDM4, RAD51, SRP54, and WIPF1. Our results provide an important population-based framework for the interpretation of LoF variant pathogenicity in rare and emerging IBMF syndromes.

Oropharyngeal mucositis (OPM) is common following conditioning for allogeneic hematopoietic cell transplantation (alloHCT) and results in pain, functional status decline, need for nutritional support, infections, and prolonged length of stay (LOS). Methotrexate (MTX) graft-versus-host disease (GVHD) prophylaxis exacerbates OPM and slows hematopoietic engraftment, which may prolong LOS. Previous studies have demonstrated reduced OPM and more rapid engraftment when leucovorin (LCV) is added following MTX GVHD prophylaxis, yet this practice is controversial. The primary objective of this study was to determine if the routine addition of LCV to MTX GVHD prophylaxis impacted the duration of grade 2 to 4 OPM. Secondary objectives included determination of the incidence of grade 2 to 4 and grade 3 to 4 OPM, time to engraftment, ability to receive all four planned MTX doses, use of total parenteral nutrition (TPN), use of patient-controlled analgesia (PCA), LOS, incidence of acute or chronic GVHD, relapse-free survival (RFS), and overall survival (OS). This single-center, retrospective cohort study compared alloHCT outcomes for 46 adult patients who received MTX 15 mg/m2 day +1; MTX 10 mg/m2 days +3, +6, and +11 (15-10-10-10); and LCV following days +3, +6, and +11 MTX compared to historical controls who did not. Patients who received myeloablative conditioning (MAC) and matched related donor (MRD) or matched unrelated donor (MUD) alloHCT were included. The addition of LCV resulted in significant reductions in the duration of grade 2 to 4 OPM (median, 6 days versus 10.5 days; P = .0004), duration of TPN (7 days versus 16 days; P = .001), PCA use (16% versus 39%; P = .0001), time to neutrophil engraftment (median, 18 versus 20 days; P = .008), and LOS (median, 27.5 versus 31 days; P = .017) compared to historical controls. Patients who received routine LCV had similar incidences of grade 2 to 4 acute GVHD (30% versus 28%; relative risk [RR], 1.08; 95% confidence interval [CI], .57 to 2.03; P = 1.0), grade 3 or 4 acute GVHD (2% versus 7%; RR, .33; 95% CI, .04 to 3.09; P = .62) and chronic GVHD (37% versus 30%; RR, 1.21; 95% CI, .67 to 2.16; P = .66) compared to historical controls. Graft failure occurred in 2% of patients in each group. In a multivariable logistic regression analysis, RFS was similar in the LCV group compared to historical controls (HR, .86; 95% CI, .24 to 1.2; P = .13); however, OS was improved in patients who received LCV (HR, .33; 95% CI, .13 to .83; P = .01). In patients undergoing MAC MRD/MUD alloHCT with four planned doses of MTX GVHD prophylaxis (15-10-10-10), LCV was associated with reduced duration of grade 2 to 4 OPM, faster neutrophil engraftment, reduced utilization of TPN and PCA, and shortened LOS compared to historical controls not receiving routine LCV. These benefits were apparent without an increased risk of acute or chronic GVHD or adverse effect on RFS. LCV improved OS; however, it is unclear if this was due to the intervention or an unmeasured confounder. A randomized, prospective trial of LCV prophylaxis in patients receiving MAC alloHCT and MTX 15-10-10-10 GVHD prophylaxis is warranted to confirm our findings.

Inherited bone marrow failure is caused by mutations in genes that are critical for normal cell development or intrinsic cell function. Because of the protean effects of the mutations, multi-organ involvement is common. Compromised growth and early senescence drive strong selective pressure to acquire oncogenic somatic abnormalities. Thus, testing should be performed on non-hematopoietic cells such as fibroblasts.

Acquired aplastic anemia (AA) is an immune-mediated bone marrow aplasia that is strongly associated with clonal hematopoiesis upon marrow recovery. More than 70% of AA patients develop somatic mutations in their hematopoietic cells. In contrast to other conditions linked to clonal hematopoiesis, such as myelodysplastic syndrome (MDS) or clonal hematopoiesis of indeterminate potential in the elderly, the top alterations in AA are closely related to its immune pathogenesis. Nearly 40% of AA patients carry somatic mutations in the PIGA gene manifested as clonal populations of cells with the paroxysmal nocturnal hemoglobinuria phenotype, and 17% of AA patients have loss of HLA class I alleles. It is estimated that between 20% and 35% of AA patients have somatic mutations associated with hematologic malignancies, most characteristically in the ASXL1, BCOR, and BCORL1 genes. Risk factors for evolution to MDS in AA include the duration of disease, acquisition of high-risk somatic mutations, and age at AA onset. Emerging data suggest that several HLA class I alleles not only predispose to the development of AA but may also predispose to clonal evolution in AA patients. Long-term prospective studies are needed to determine the true prognostic implications of clonal hematopoiesis in AA. This article provides a brief, but comprehensive, review of our current understanding of clonal evolution in AA and concludes with 3 cases that illustrate a practical approach for integrating results of next-generation molecular studies into the clinical care of AA patients in 2018.

BACKGROUND: Clostridium difficile infection (CDI) is a leading cause of infectious complications in allogeneic hematopoietic cell transplant recipients (alloHCT). We sought to evaluate whether prophylactic oral vancomycin reduces the incidence of CDI in alloHCT recipients. METHODS: We conducted a retrospective cohort study to examine the effectiveness of CDI prophylaxis with oral vancomycin, as compared to no prophylaxis, in 145 consecutive adult alloHCT recipients at the University of Pennsylvania between April 2015 and November 2016. Patients received oral vancomycin 125 mg twice daily, starting on admission and continuing until discharge. The primary outcome of interest was the association between oral vancomycin prophylaxis and CDI diagnosis. Secondary outcomes included graft-versus-host disease (GVHD) and relapse. RESULTS: There were no cases of CDI in patients that received prophylaxis (0/90, 0%), whereas 11/55 (20%) patients who did not receive prophylaxis developed CDI (P < .001). Oral vancomycin prophylaxis was not associated with a higher risk of acute, grades 2–4 GVHD (subhazard ratio [sHR] 1.59; 95% confidence interval [CI] 0.88–2.89; P = .12), acute, grades 3–4 GVHD (sHR 0.65; 95% CI 0.25–1.66; P = .36), or acute, grades 2–4 gastrointestinal GVHD (sHR 1.95; 95% CI 0.93–4.07; P = .08) at day 180 post-transplant. No associations between oral vancomycin and relapse or survival were observed. CONCLUSIONS: Prophylaxis with oral vancomycin is highly effective in preventing CDI in alloHCT recipients without increasing the risk of graft-versus-host disease or disease relapse. Further evaluation via a prospective study is warranted.

Steroid-refractory (SR) acute gastrointestinal (GI) graft-versus-host disease (GVHD) is associated with significant mortality in allogeneic hematopoietic cell transplantation recipients. We retrospectively evaluated the efficacy of tocilizumab for the treatment of SR biopsy-proven acute lower GI GVHD in 16 consecutive adult transplant recipients between October 2015 and July 2016. Tocilizumab 8 mg/kg was administered every 2 weeks until achievement of complete response, defined as resolution of all manifestations of GI GVHD, or until patients had progression or initiation of other therapy. Ten of 16 patients (62.5%; 95% CI, 0.39-82) achieved a complete response after a median time of 11 days (range, 2-28 days) from tocilizumab initiation. The median time to response onset (improvement in stage by at least 1) was 1 day (range, 1-4 days). Tocilizumab was administered at a median of 9 days (range, 3-75 days) from GVHD diagnosis and 10 days (range, 3-75 days) from initiation of high-dose steroids. At a median follow-up of 7.6 months (range, 0.8-27.7 months) from initiation of tocilizumab, 6/16 (37.5%) patients are alive and free of their underlying hematologic malignancy. Tocilizumab appears to be a highly active agent for the treatment of severe SR lower GI acute GVHD.

The JAK2 V617F mutation is characteristic of most Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) and occurs rarely in de novo acute myeloid leukaemia (AML). We sought to characterize AMLs that harbour this mutation and distinguish those that arise de novo (AML-DN) from those that reflect transformation of an underlying MPN (AML-MPN). Forty-five patients with JAK2 V617F-mutated AML were identified; 15 were AML-DN and 30 were AML-MPN. AML-MPN cases were more likely to have splenomegaly (P = 0·02), MPN-like megakaryocytes and higher mean JAK2 V617F VAF at diagnosis (P = 0·04). Mutations involving TET2 were exclusively identified in AML-DN patients. Mutations of genes affecting DNA methylation were more common in AML-DN (P < 0·01). A complex karyotype was more frequent in AML-MPN cases than in AML-DN (P < 0·01), with AML-DN more likely to display a normal karyotype (P = 0·02). Bone marrow histology after recovery from induction chemotherapy in AML-DN cases revealed no morphological evidence of any previously occult MPNs, while this was evident in most of the AML-MPN specimens (P < 0·01). These findings in this largest study of JAK2 V617F-mutated AMLs indicate that AML-DN is distinct from AML-MPN.

Myeloproliferative neoplasms arise from hematopoietic stem cells with somatically altered tyrosine kinase signaling. Classification of myeloproliferative neoplasms is based on hematologic, histopathologic and molecular characteristics including the presence of the BCR-ABL1 and JAK2 V617F. Although thought to be mutually exclusive, a number of cases with co-occurring BCR-ABL1 and JAK2 V617F have been identified. To characterize the clinicopathologic features of myeloproliferative neoplasms with concomitant BCR-ABL1 and JAK2 V617F, and define the frequency of co-occurrence, we conducted a retrospective multi-institutional study. Cases were identified using a search of electronic databases over a decade at six major institutions. Of 1570 patients who were tested for both BCR-ABL1 and JAK2 V617F, six were positive for both. An additional five patients were identified via clinical records providing a total of 11 cases for detailed evaluation. For each case, clinical variables, hematologic and genetic data, and bone marrow histomorphologic features were analyzed. The sequence of identification of the genetic abnormalities varied: five patients were initially diagnosed with a JAK2 V617F+ myeloproliferative neoplasm, one patient initially had BCR-ABL1+ chronic myeloid leukemia, while both alterations were identified simultaneously in five patients. Classification of the BCR-ABL1-negative myeloproliferative neoplasms varied, and in some cases, features only became apparent following tyrosine kinase inhibitor therapy. Seven of the 11 patients showed myelofibrosis, in some cases before identification of the second genetic alteration. Our data, reflecting the largest reported study comprehensively detailing clinicopathologic features and response to therapy, show that the co-occurrence of BCR-ABL1 and JAK2 V617F is rare, with an estimated frequency of 0.4%, and most often reflects two distinct ('composite') myeloproliferative neoplasms. Although uncommon, it is important to be aware of this potentially confounding genetic combination, lest these features be misinterpreted to reflect resistance to therapy or disease progression, considerations that could lead to inappropriate management.

Key Points Success of hematopoietic stem cell transplantation for MIRAGE syndrome may be limited by syndrome-specific comorbidities. SAMD9 mutations associated with MIRAGE syndrome are a newly described cause of congenital amegakaryocytic thrombocytopenia.

Introduction Increasingly clinicians face the choice between CPX-351 (NCT01696084) and venetoclax and azacitadine (ven/aza, NCT02993523) in front-line acute myeloid leukemia (AML), especially for frailer older adults with comorbidities. Given no prospective data, we examined retrospective observational survival outcomes for patients with newly diagnosed AML receiving either CPX-351 or ven/aza as initial therapy. Methods After local Institutional Review Board approval, we included patients from both the University of Pennsylvania ("HUP", n=111) and the Flatiron Health electronic health record (EHR) derived, de-identified database with a first incident AML diagnosed between January 2017 and 2021, and with documented receipt of CPX-351 or venetoclax and azacitadine as initial therapy (n=548). Given a total of 219 patients received CPX-351 and 440 received ven/aza, there was 90% power to detect a hazard ratio (HR) of 0.77 or smaller with alpha 0.05. Overall Survival (OS) was analyzed by the Kaplan-Meier method and compared between arms using the log-rank test. Pre-planned sensitivity analyses included restriction and multiple imputation (MI) to address missingness with inverse-probability of treatment weighting (IPTW) to balance baseline covariates with treatment effect estimates from each imputed dataset combined via Rubin's rules. Results For all patients, baseline covariates showed patients receiving ven/aza were older (75 vs 65 years old median age), more likely to have Medicare (29% vs 20%), have de-novo AML vs secondary or therapy-related disease (52% vs 29%) and be treated in the community rather than an academic center (66% vs 52%). All other baseline covariates-including ELN cytogenetic risk groups, high risk mutations (TP53, ASXL1, RUNX1), FLT3, IDH, HCT-comorbidity index-were not statistically significant different between groups (table 1). Missing values in the HUP dataset was Median OS (mOS) was 12 months for all patients and 13 months for CPX-351 versus 11 months for ven/aza (HR 0.87, 95% CI 0.70-1.07, p-value 0.184, Fig 1a). There was no clear subset with improved OS with CPX-351 vs ven/aza (Fig 1b); in multi-variate analysis controlling for all covariates with univariate p-value < 0.20 induction choice did not affect overall survival (limited to complete cases n=133, HR 0.63, p-value 0.73). Restricting to only the population eligible for CPX-351 pivotal trial, there was no significant difference in OS (CPX-351 n=160 mOS=10, ven/aza n=181 mOS=12 HR 0.86 p-value 0.33). After MI and IPTW, survival remained similar with HR 0.95 p-value 0.77 (Fig 1c). Adjusting further for variables with absolute standardized difference >10% after MI and IPTW (baseline HCT-comorbidity index, race and insurance status), multivariable Cox model gave similar results (HR 0.93, p-value 0.70). Regarding safety outcomes, early mortality was similar. However, documented diagnosed infections were higher in CPX-351 patients and within the HUP cohort, rates of febrile neutropenia and culture positive infection were also higher (Fig 1d). Length of stay, including any admission prior to next cycle of therapy, was more than twice as long for CPX-351 in the HUP cohort. Additional analyses, including detailed assessment of baseline covariates, multivariate analysis with transplant as a time-varying dependent covariate, event free survival, disease free survival also available for presentation. Conclusion In this multi-center real word dataset with over 600 patients, there was no statistically significant difference in overall survival between induction with CPX-351 and ven/aza. This large retrospective dataset is limited by missingness in covariates, risk of misclassification bias and lack of power for formal equivalence testing. However, a consistent lack of superiority for CPX-351 or ven/aza within a robust, manual chart-review of an academic institution, a large national real world database and combined analyses of these cohorts supports clinical equipoise. Given the apparent lack of a large survival benefit further work is needed. Prospective studies to confirm similar effectiveness with careful attention to side effects, quality of life and impact on transplant outcomes may help clinicians decide between these therapies. Figure 1 Figure 1. Disclosures Perl: Syndax: Consultancy; Loxo: Consultancy; Forma: Consultancy; AbbVie: Consultancy, Research Funding; Roche: Consultancy; Actinium: Consultancy; Genentech: Consultancy; Astellas: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Fujifilm: Research Funding; BMS/Celgene: Consultancy; Arog: Research Funding; Onconova: Consultancy; Sumitomo Dainippon: Consultancy. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Frey: Kite Pharma: Consultancy; Novartis: Research Funding; Sana Biotechnology: Consultancy; Syndax Pharmaceuticals: Consultancy. Gill: Interius Biotherapeutics: Current holder of stock options in a privately-held company, Research Funding; Carisma Therapeutics: Current holder of stock options in a privately-held company, Research Funding; Novartis: Other: licensed intellectual property, Research Funding. Hexner: Blueprint medicines: Membership on an entity's Board of Directors or advisory committees, Research Funding; PharmaEssentia: Membership on an entity's Board of Directors or advisory committees; Tmunity Therapeutics: Research Funding. Porter: American Society for Transplantation and Cellular Therapy: Honoraria; ASH: Membership on an entity's Board of Directors or advisory committees; DeCart: Membership on an entity's Board of Directors or advisory committees; Genentech: Current Employment, Current equity holder in publicly-traded company; Incyte: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Membership on an entity's Board of Directors or advisory committees; National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Unity: Patents & Royalties; Wiley and Sons Publishing: Honoraria. Stadtmauer: Oncopeptides: Consultancy; Amgen: Consultancy; BMS Celgene: Consultancy; GSK: Consultancy; Janssen: Consultancy; AbbVie: Consultancy, Research Funding. Maillard: Regeneron: Research Funding. Margolis: Pfizer: Consultancy; Leo: Consultancy; Sanofi: Consultancy; National Eczema Association: Membership on an entity's Board of Directors or advisory committees. Pratz: Abbvie: Consultancy, Honoraria, Research Funding; Agios: Consultancy; BMS: Consultancy, Honoraria; Novartis: Consultancy; Astellas: Consultancy, Honoraria, Research Funding; Cellgene: Consultancy, Honoraria; Millenium: Research Funding; University of Pennsylvania: Current Employment.

Fanconi anemia (FA), a genetic disorder affecting DNA repair, is characterized by bone marrow failure and cancer susceptibility. In FA mouse models, metformin (N,N-dimethylguanide) a biguanide metabolic agent, improves blood counts and delays tumor development. Given these findings, we conducted a single institution pilot study of metformin in non-diabetic patients with FA to assess feasibility, tolerability, and impact of metformin on hematologic response as defined by modified MDS International Working Group (IWG) criteria (Table 1). Fourteen of 15 patients with at least 1 cytopenia (hemoglobin Figure 1 Figure 1. Disclosures Pollard: Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Syndax: Membership on an entity's Board of Directors or advisory committees. Furutani: Keros Therapeutics: Current Employment, Current equity holder in publicly-traded company. Esrick: bluebird bio: Consultancy. Nakano: Novartis: Consultancy. Thompson: Celgene: Consultancy, Research Funding; bluebird bio: Consultancy, Research Funding; Biomarin: Research Funding; Vertex: Research Funding; Graphite Bio: Research Funding; Baxalta: Research Funding; CRISPR Therapeutics: Research Funding; Novartis: Research Funding; Agios Pharmaceuticals: Consultancy; Beam Therapeutics: Consultancy; Global Blood Therapeutics: Current equity holder in publicly-traded company. OffLabel Disclosure: metformin- use in Fanconi anemia in an effort to improve hematopoiesis

BCR-ABL1-negative myeloproliferative neoplasms (MPNs) are clonal stem cell disorders defined by proliferation of one or more myeloid lineages, and carry an increased risk of vascular events and progression to myelofibrosis and leukemia. Portal hypertension (pHTN) occurs in 7-18% of MPN patients via both thrombotic and nonthrombotic mechanisms and portends a poor prognosis. Transjugular intrahepatic portosystemic shunt (TIPS) has been used in the management of MPN-associated pHTN; however, data on long-term outcomes of TIPS in this setting is limited and the optimal management of medically refractory MPN-associated pHTN is not known. In order to assess the efficacy and long-term outcomes of TIPS in MPN-associated pHTN, we performed a retrospective analysis of 29 MPN patients who underwent TIPS at three academic medical centers between 1997 and 2016. The majority of patients experienced complete clinical resolution of pHTN and its clinical sequelae following TIPS. One, two, three, and four-year overall survival post-TIPS was 96.4%, 92.3%, 84.6%, and 71.4%, respectively. However, despite therapeutic anticoagulation, in-stent thrombosis occurred in 31.0% of patients after TIPS, necessitating additional interventions. In conclusion, TIPS can be an effective intervention for MPN-associated pHTN regardless of etiology. However, TIPS thrombosis is a frequent complication in the MPN population and indefinite anticoagulation post-TIPS should be considered.

In this issue of Blood, Simon et al evaluated 430 samples from patients with acute myeloid leukemia (AML) for germline and somatic mutations in RUNX family transcription factor 1 (RUNX1). They found that nearly 30% of the identified variants were germline.(1)

Acquired aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH) are pathogenically related nonmalignant bone marrow failure disorders linked to T-cell–mediated autoimmunity; they are associated with an increased risk of secondary myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Approximately 15% to 20% of AA patients and 2% to 6% of PNH patients go on to develop secondary MDS/AML by 10 years of follow-up. Factors determining an individual patient’s risk of malignant transformation remain poorly defined. Recent studies identified nearly ubiquitous clonal hematopoiesis (CH) in AA patients. Similarly, CH with additional, non-PIGA, somatic alterations occurs in the majority of patients with PNH. Factors associated with progression to secondary MDS/AML include longer duration of disease, increased telomere attrition, presence of adverse prognostic mutations, and multiple mutations, particularly when occurring early in the disease course and at a high allelic burden. Here, we will review the prevalence and characteristics of somatic alterations in AA and PNH and will explore their prognostic significance and mechanisms of clonal selection. We will then discuss the available data on post-AA and post-PNH progression to secondary MDS/AML and provide practical guidance for approaching patients with PNH and AA who have CH.

Key Points Acquired aplastic anemia is a T-cell–mediated autoimmune bone marrow aplasia, without a known etiologic trigger. Clonal expansion of CD8+ effector T lymphocytes can occur following vaccination and accompany graft dysfunction or aplastic anemia relapse.

Eltrombopag (EPAG) received approval from the US Food and Drug Administration for the treatment of refractory severe aplastic anemia (rSAA) based on treatment of 43 patients with doses escalating from 50 to 150 mg daily for 12 weeks. Response kinetics suggested that more prolonged administration of EPAG at a dose of 150 mg could speed and improve response rates. We enrolled 40 patients with rSAA in a study of EPAG 150 mg daily, with a primary end point of response at 24 weeks. Twenty (50%) of 40 patients responded at 24 weeks; 5 (25%) of 20 would have been deemed nonresponders at 12 weeks, the end point of the previous study. Fifteen of the 19 responding patients continuing on EPAG had drug discontinued for robust response; 5 of the 15 required EPAG re-initiation for relapse, with all recovering response. To analyze risk of clonal progression, we combined long-term data from the 83 patients with rSAA enrolled in both studies. Evolution to an abnormal karyotype occurred in 16 (19%), most within 6 months of EPAG initiation. Targeted deep sequencing/whole-exome sequencing was performed pre-EPAG and at primary response end point and/or time of clonal evolution or longest follow-up. Cytogenetic evolution did not correlate with mutational status, and overall mutated allele fractions of myeloid cancer genes did not increase on EPAG. In summary, extended administration of EPAG at a dose of 150 mg for 24 weeks rescued responses in some patients with rSAA not responding at 12 weeks. The temporal relationship between clonal evolution and drug exposure suggests that EPAG may promote expansion of dormant preexisting clones with an aberrant karyotype. The studies were registered at www.clinicaltrials.gov as #NCT00922883 and #NCT01891994.

Idiopathic acquired aplastic anemia (AA) is a rare lymphocyte-mediated bone marrow aplasia. No specific mechanisms or triggers of AA have been identified. We recently observed several patients who developed AA after Hodgkin lymphoma (HL). We hypothesized that the co-occurrence of HL and AA is not random and may be etiologically significant. To test this hypothesis, we determined the incidence of AA in HL patients at our institution. We identified four patients with co-occurring HL and AA, with the incidence of AA in HL patients >20-fold higher compared to the general population. We identified 12 additional patients with AA and HL through a systematic literature review. Of the 16 total patients,15 (93.8%) developed AA after or concurrent with a HL diagnosis. None of the patients had marrow involvement by HL. Five of 15 patients were in complete remission from HL at the time of AA diagnosis, and six had a concurrent presentation with no prior cytotoxic therapy, with diagnostic timeframe information unavailable for four patients. The median interval between HL diagnosis and AA onset was 16 months, ranging from concurrent to 14 years after a HL diagnosis. The median survival after AA diagnosis was 14 months (range: 1 month to 20 years). Our results show that patients with HL have a higher incidence of AA compared to the general population and suggest that HL-related immune dysregulation may be a risk factor for AA. Better recognition and management of AA in HL patients is needed to improve outcomes in this population.

Importance Health care workers (HCWs) caring for patients with coronavirus disease 2019 (COVID-19) are at risk of exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, to our knowledge, there is no effective pharmacologic prophylaxis for individuals at risk. Objective To evaluate the efficacy of hydroxychloroquine to prevent transmission of SARS-CoV-2 in hospital-based HCWs with exposure to patients with COVID-19 using a pre-exposure prophylaxis strategy. Design, Setting, and Participants This randomized, double-blind, placebo-controlled clinical trial (the Prevention and Treatment of COVID-19 With Hydroxychloroquine Study) was conducted at 2 tertiary urban hospitals, with enrollment from April 9, 2020, to July 14, 2020; follow-up ended August 4, 2020. The trial randomized 132 full-time, hospital-based HCWs (physicians, nurses, certified nursing assistants, emergency technicians, and respiratory therapists), of whom 125 were initially asymptomatic and had negative results for SARS-CoV-2 by nasopharyngeal swab. The trial was terminated early for futility before reaching a planned enrollment of 200 participants. Interventions Hydroxychloroquine, 600 mg, daily, or size-matched placebo taken orally for 8 weeks. Main Outcomes and Measures The primary outcome was the incidence of SARS-CoV-2 infection as determined by a nasopharyngeal swab during the 8 weeks of treatment. Secondary outcomes included adverse effects, treatment discontinuation, presence of SARS-CoV-2 antibodies, frequency of QTc prolongation, and clinical outcomes for SARS-CoV-2–positive participants. Results Of the 132 randomized participants (median age, 33 years [range, 20-66 years]; 91 women [69%]), 125 (94.7%) were evaluable for the primary outcome. There was no significant difference in infection rates in participants randomized to receive hydroxychloroquine compared with placebo (4 of 64 [6.3%] vs 4 of 61 [6.6%];P > .99). Mild adverse events were more common in participants taking hydroxychloroquine compared with placebo (45% vs 26%;P = .04); rates of treatment discontinuation were similar in both arms (19% vs 16%;P = .81). The median change in QTc (baseline to 4-week evaluation) did not differ between arms (hydroxychloroquine: 4 milliseconds; 95% CI, −9 to 17; vs placebo: 3 milliseconds; 95% CI, −5 to 11;P = .98). Of the 8 participants with positive results for SARS-CoV-2 (6.4%), 6 developed viral symptoms; none required hospitalization, and all clinically recovered. Conclusions and Relevance In this randomized clinical trial, although limited by early termination, there was no clinical benefit of hydroxychloroquine administered daily for 8 weeks as pre-exposure prophylaxis in hospital-based HCWs exposed to patients with COVID-19. Trial Registration ClinicalTrials.gov Identifier:NCT04329923

Acquired aplastic anemia (aAA) results from the T cell-mediated autoimmune destruction of hematopoietic stem cells. Factors predicting response to immune suppression therapy (IST) or development of myelodysplastic syndrome (MDS) are beginning to be elucidated. Our recent data suggest most patients with aAA treated with IST develop clonal somatic genetic alterations in hematopoietic cells. One frequent acquired abnormality is copy-number neutral loss of heterozygosity on chromosome 6p (6p CN-LOH) involving the human leukocyte antigen (HLA) locus. We hypothesized that because 6p CN-LOH clones may arise from selective pressure to escape immune surveillance through deletion of HLA alleles, the development of 6p CN-LOH may affect response to IST. We used single nucleotide polymorphism array genotyping and targeted next-generation sequencing of HLA alleles to assess frequency of 6p CN-LOH, identity of HLA alleles lost through 6p CN-LOH, and impact of 6p CN-LOH on response to IST. 6p CN-LOH clones were present in 11.3% of patients, remained stable over time, and were not associated with development of MDS-defining cytogenetic abnormalities. Notably, no patient with 6p CN-LOH treated with IST achieved a complete response. In summary, clonal 6p CN-LOH in aAA defines a unique subgroup of patients that may provide insights into hematopoietic clonal evolution.

Hepatitis‐associated aplastic anemia (HAA) is a variant of acquired aplastic anemia (AA) in which immune‐mediated bone marrow failure (BMF) develops following an acute episode of seronegative hepatitis. Dyskeratosis congenita (DC) is an inherited BMF syndrome characterized by the presence of short telomeres, mucocutaneous abnormalities, and cancer predisposition. While both conditions may cause BMF and hepatic impairment, therapeutic approaches are distinct, making it imperative to establish the correct diagnosis. In clinical practice, lymphocyte telomere lengths (TL) are used as a first‐line screen to rule out inherited telomeropathies before initiating treatment for AA. To evaluate the reliability of TL in the HAA population, we performed a retrospective analysis of TL in 10 consecutively enrolled HAA patients compared to 19 patients with idiopathic AA (IAA). HAA patients had significantly shorter telomeres than IAA patients (P = 0.009), including four patients with TL at or below the 1st percentile for age‐matched controls. HAA patients had no clinical features of DC and did not carry disease‐causing mutations in known genes associated with inherited telomere disorders. Instead, short TLs were significantly correlated with severe lymphopenia and skewed lymphocyte subsets, features characteristic of HAA. Our results indicate the importance of caution in the interpretation of TL measurements in HAA, because, in this patient population, short telomeres have limited specificity. Am. J. Hematol. 91:243–247, 2016. © 2015 The Authors. American Journal of Hematology Published by Wiley Periodicals, Inc.

Acquired aplastic anemia (AA) is a life-threatening bone marrow failure caused by an autoimmune cytotoxic T lymphocyte attack on hematopoietic stem and progenitor cells. Factors contributing to aberrant autoimmune activation in AA include a deficit of T regulatory cells and high levels of inflammatory cytokines. Several acquired conditions of immune dysregulation and genetic polymorphisms in inflammatory cytokines and human leukocyte antigen genes have been linked to an increased risk of AA. However, AA has not been reported in patients with Mendelian disorders of immune regulation. Here we report a patient with familial common variable immunodeficiency (CVID) caused by a pathogenic variant in NFKB1, who developed AA as an adult. The patient had a difficult clinical course and was unable to tolerate standard AA therapy with cyclosporine A and eltrombopag, with complications attributed in part to the effect of cyclosporine A on NF-κB signaling. Our case suggests a novel link between genetic disorders of immune regulation and AA and highlights the importance of recognizing inherited autoimmunity syndromes in AA patients for the selection of optimal therapy and prognostic counseling.

The introduction of Janus kinase (JAK) 1/2 inhibitor ruxolitinib into the armamentarium of myelofibrosis therapies has allowed to effectively control systemic symptoms, reduce splenomegaly, and imp...

Comprehensive genomic profiling of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) cases have enabled the detection and differentiation of driver and subclonal mutations, informed risk prognostication, and defined targeted therapies. These insights into disease biology, and management have made multigene-acquired mutation testing a critical part of the diagnostic assessment of patients with sporadic MDS and AML. More recently, our understanding of the role of an increasing number of inherited genetic factors on MDS/AML risk and management has rapidly progressed. In recognition of the growing impact of this field, clinical guidelines and disease classification systems for both MDS and AML have recently incorporated familial MDS/AML predisposition syndromes into their diagnostic algorithms. In this perspective piece, we contemplate the advantages, disadvantages, and barriers that would need to be overcome to incorporate inherited MDS/AML genetic testing into the upfront molecular diagnostic work-up of every MDS/AML patient. For centers already performing panel-based tumor-only testing, including genes associated with familial forms of MDS/AML (e.g., RUNX1, CEBPA, GATA2, TP53), we advocate optimizing these tests to detect all types of germline variants in these genes and moving toward upfront paired tumor/germline testing to maximize detection and streamline patient care.

Myelodysplastic syndrome (MDS) is a clonal blood disorder characterized by ineffective hematopoiesis, cytopenias, dysplasia and an increased risk of acute myeloid leukemia (AML). With the growing availability of clinical genetic testing, there is an increasing appreciation that a number of genetic predisposition syndromes may underlie apparent de novo presentations of MDS/AML, particularly in children and young adults. Recent findings of clonal hematopoiesis in acquired aplastic anemia add another facet to our understanding of the mechanisms of MDS/AML predisposition. As more predisposition syndromes are recognized, it is becoming increasingly important for hematologists and oncologists to have familiarity with the common as well as emerging syndromes, and to have a systematic approach to diagnosis and screening of at risk patient populations. Here, we provide a practical algorithm for approaching a patient with a suspected MDS/AML predisposition, and provide an in-depth review of the established and emerging familial MDS/AML syndromes caused by mutations in the ANKRD26, CEBPA, DDX41, ETV6, GATA2, RUNX1, SRP72 genes. Finally, we discuss recent data on the role of somatic mutations in malignant transformation in acquired aplastic anemia, and review the practical aspects of MDS/AML management in patients and families with predisposition syndromes.

Acquired aplastic anemia (aAA) is a nonmalignant disease caused by autoimmune destruction of early hematopoietic cells. Clonal hematopoiesis is a late complication, seen in 20–25% of older patients. We hypothesized that clonal hematopoiesis in aAA is a more general phenomenon, which can arise early in disease, even in younger patients. To evaluate clonal hematopoiesis in aAA, we used comparative whole exome sequencing of paired bone marrow and skin samples in 22 patients. We found somatic mutations in 16 patients (72.7%) with a median disease duration of 1 year; of these, 12 (66.7%) were patients with pediatric-onset aAA. Fifty-eight mutations in 51 unique genes were found primarily in pathways of immunity and transcriptional regulation. Most frequently mutated was PIGA , with seven mutations. Only two mutations were in genes recurrently mutated in myelodysplastic syndrome. Two patients had oligoclonal loss of the HLA alleles, linking immune escape to clone emergence. Two patients had activating mutations in key signaling pathways (STAT5B (p.N642H) and CAMK2G (p.T306M)). Our results suggest that clonal hematopoiesis in aAA is common, with two mechanisms emerging—immune escape and increased proliferation. Our findings expand conceptual understanding of this nonneoplastic blood disorder. Future prospective studies of clonal hematopoiesis in aAA will be critical for understanding outcomes and for designing personalized treatment strategies.

Myelodysplastic syndromes (MDS) are clonal hematopoietic disorders characterized by cytopenias, ineffective hematopoiesis, myelodysplasia, and an increased risk of acute myeloid leukemia (AML). While sporadic MDS is primarily a disease of the elderly, MDS in children and young and middle-aged adults is frequently associated with underlying genetic predisposition syndromes. In addition to the classic hereditary bone marrow failure syndromes (BMFS) such as Fanconi Anemia and Dyskeratosis Congenita, in recent years there has been an increased awareness of non-syndromic familial MDS/AML predisposition syndromes such as those caused by mutations in GATA2, RUNX1, CEBPA, and SRP72 genes. Here, we will discuss the importance of recognizing an underlying genetic predisposition syndrome a patient with MDS, will review clinical scenarios when genetic predisposition should be considered, and will provide a practical overview of the common BMFS and familial MDS/AML syndromes which may be encountered in adult patients with MDS.

Acquired aplastic anemia (AA) is a rare, life-threatening bone marrow failure (BMF) disorder that affects patients of all ages and is caused by lymphocyte destruction of early hematopoietic cells. Diagnosis of AA requires a comprehensive approach with prompt evaluation for inherited and secondary causes of bone marrow aplasia, while providing aggressive supportive care. The choice of frontline therapy is determined by a number of factors including AA severity, age of the patient, donor availability, and access to optimal therapies. For newly diagnosed severe aplastic anemia, bone marrow transplant should be pursued in all pediatric patients and in younger adult patients when a matched sibling donor is available. Frontline therapy in older adult patients and in all patients lacking a matched sibling donor involves immunosuppressive therapy (IST) with horse antithymocyte globulin and cyclosporine A. Recent improvements in upfront therapy include encouraging results with upfront closely matched unrelated donor transplants in younger patients and the emerging benefits of eltrombopag combined with initial IST, with randomized studies underway. In the refractory setting, several therapeutic options exist, with improving outcomes of matched unrelated donor and haploidentical bone marrow transplantation as well as the addition of eltrombopag to the non-transplant AA armamentarium. With the recent appreciation of frequent clonal hematopoiesis in AA patients and with the growing use of next-generation sequencing in the clinic, utmost caution should be exercised in interpreting the significance of somatic mutations in AA. Future longitudinal studies of large numbers of patients are needed to determine the prognostic significance of somatic mutations and to guide optimal surveillance and treatment approaches to prevent long term clonal complications.

Acquired aplastic anemia (aAA) is an acquired deficiency of early hematopoietic cells, characterized by inadequate blood production, and a predisposition to myelodysplastic syndrome (MDS) and leukemia. Although its exact pathogenesis is unknown, aAA is thought to be driven by human leukocyte antigen (HLA)–restricted T cell immunity, with earlier studies favoring HLA class II-mediated pathways. Using whole-exome sequencing (WES), we recently identified 2 patients with aAA with somatic mutations in HLA class I genes. We hypothesized that HLA class I mutations are pathognomonic for autoimmunity in aAA, but were previously underappreciated because the major histocompatibility complex (MHC) region is notoriously difficult to analyze by WES. Using a combination of targeted deep sequencing of HLA class I genes and single nucleotide polymorphism array (SNP-A) genotyping, we screened 66 patients with aAA for somatic HLA class I loss. We found somatic HLA loss in 11 patients (17%), with 13 loss-of-function mutations in HLA-A*33:03, HLA-A*68:01, HLA-B*14:02, and HLA-B*40:02 alleles. Three patients had more than 1 mutation targeting the same HLA allele. Interestingly, HLA-B*14:02 and HLA-B*40:02 were significantly overrepresented in patients with aAA compared with ethnicity-matched controls. Patients who inherited the targeted HLA alleles, regardless of HLA mutation status, had a more severe disease course with more frequent clonal complications as assessed by WES, SNP-A, and metaphase cytogenetics, and more frequent secondary MDS. The finding of recurrent HLA class I mutations provides compelling evidence for a predominant HLA class I-driven autoimmunity in aAA and establishes a novel link between immunogenetics and clonal evolution of patients with aAA.

Acquired aplastic anaemia (AA) is an immune-mediated bone marrow failure disorder inextricably linked to clonal haematopoiesis. The majority of AA patients have somatic mutations and/or structural chromosomal abnormalities detected as early as at diagnosis. In contrast to other conditions linked to clonal haematopoiesis, the clonal signature of AA reflects its immune pathophysiology. The most common alterations are clonal expansions of cells lacking glycophosphotidylinositol-anchored proteins, loss of human leucocyte antigen alleles, and mutations in BCOR/BCORL1, ASXL1 and DNMT3A. Here, we present the current knowledge of clonal haematopoiesis in AA as it relates to aging, inherited bone marrow failure, and the grey-zone overlap of AA and myelodysplastic syndrome (MDS). We conclude by discussing the significance of clonal haematopoiesis both for improved diagnosis of AA, as well as for a more precise, personalized approach to prognostication of outcomes and therapy choices.

Introduction: Older patients with high-risk myeloid malignancies are now eligible for either induction chemotherapy (IC) or novel treatment strategies including liposomal cytarabine and daunorubicin (Vyxeos) or hypomethylating agent (HMA)/venetoclax. Vyxeos and HMA/venetoclax may be associated with less early mortality, but no trials have demonstrated significantly less mortality compared to IC. In this context, we need a better tool to determine a patient's risk of early mortality by strategy in order to inform therapy selection for older patients. The current methods to assess a patient's fitness for IC are the Eastern Cooperative Oncology Group (ECOG) or Karnofsky Performance Status (KPS) assessments, clinician subjective evaluations [i.e. gestalt (CG)], and often age itself (>75-80 years). None of these include objective measures of fitness. The Fried frailty phenotype (FP) uses both subjective (exhaustion and activity level) and objective measures (weight loss, gait speed, and grip strength) of frailty to categorize patients into fit, pre-frail, and frail. We hypothesized that FP would correlate with early mortality in this population and could be used to guide initial treatment selection. Methods: From September, 2018 to June, 2019 we prospectively enrolled 30 patients age 60 years or older with newly diagnosed, untreated acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS) on an ongoing institutional review board approved clinical trial. We performed FP, CG, hematopoietic cell transplantation-comorbidity index (HCT-CI), and ECOG assessments on all patients prior to initiation of any therapy for their high grade myeloid disease. The primary endpoints were 60 and 100-day mortality. Results: Median patient age and follow up were 70.9 (range 61-82) years and 111 days, respectively. Patients had high-risk disease features as shown in Table 1, with the vast majority of AML patients being adverse risk by European Leukemia Network criteria and all MDS patients being high or very high-risk by the Revised International Prognostic Scoring System. The most common molecular mutations were TP53, ASXL1, RUNX1, IDH1/2, FLT3, and DNMT3A. IC consisting of either 7+3 or Vyxeos was used in 11 patients, HMA alone or in combination in 16, targeted therapy with enasidenib alone in 1, and best supportive care (BSC) in 2 (Table 1). Four patients who were frail by FP received IC (3 with Vyxeos). By FP assessments, 17% of patients were fit (score 0), 33% were pre-frail (score 1-2), and 50% were frail (score 3-5). In contrast, CG categorized 37% of patients as fit, 30% as pre-frail, and 33% as frail. Seven of 15 frail patients by FP were categorized as pre-frail or fit by CG. FP and ECOG scores also differed with 7 patients having low-risk ECOG scores of 0-1 and a high-risk FP of ≥3 (frail). For entire cohort, 60- and 100-day mortality rates were 15% and 25%, respectively. Frail patients by FP had 60-day and 100-day mortality rates of 32% and 51%, respectively, which was significantly worse than fit and pre-frail patients, all of whom were alive at 100 days (Figure 1/2, p=.016). Of the 6 out of 15 FP frail patients who died, 1 received a HMA alone, 3 HMA with venetoclax, and 2 BSC. In patients with ECOG scores of 0-1 or those categorized as fit by CG, 100-day mortalities were 8% and 10%, respectively. Mortality for patients with HCT-CI scores of 1-2 was unexpectedly higher (34% at both 60 days and 100 days) than for patients with higher risk HCT-CI scores ≥3 (13% and 29%, respectively). Conclusion: In newly diagnosed older patients with advanced myeloid neoplasms, being frail by FP was associated with increased 60 and 100-day mortality, owing to high mortality rates with HMA based therapies. While HCT-CI scores have been significantly associated with mortality after allogeneic transplantation, we observed that these scores were not linearly associated with survival or mortality in newly diagnosed AML and high/very-high risk MDS patients. By ECOG and CG, even the low risk groups contained patient deaths, suggesting that these standard metrics may not capture certain at-risk patients. CG tended to down grade frailty scores, categorizing patients as fitter than they were by FP. As such, FP may be a useful tool to predict early mortality. Further research is warranted to determine whether mortality differs by treatment within a given FP category, which may support the use of FP to select initial therapy. Disclosures Frey: Novartis: . Gill:Novartis: Research Funding; Tmunity Therapeutics: Research Funding; Carisma Therapeutics: Research Funding; Amphivena: Consultancy; Aro: Consultancy; Intellia: Consultancy; Sensei Bio: Consultancy; Carisma Therapeutics: Equity Ownership. Perl:Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding. Maillard:Genentech: Consultancy; Regeneron: Consultancy. Pratz:Millenium/Takeda: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios: Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Membership on an entity's Board of Directors or advisory committees, Research Funding. Porter:Kite: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees; Glenmark Pharm: Membership on an entity's Board of Directors or advisory committees; Immunovative: Membership on an entity's Board of Directors or advisory committees; American Board of Internal Medicine: Membership on an entity's Board of Directors or advisory committees; Wiley and Sons: Honoraria; Genentech: Employment. Carroll:Astellas Pharmaceuticals: Research Funding; Incyte: Research Funding; Janssen Pharmaceuticals: Consultancy. Luger:Seattle Genetics: Research Funding; Biosight: Research Funding; Ariad: Research Funding; Agios: Honoraria; Genetech: Research Funding; Daichi Sankyo: Honoraria; Onconova: Research Funding; Kura: Research Funding; Jazz: Honoraria; Celgene: Research Funding; Cyslacel: Research Funding; Pfizer: Honoraria.

PNH is the most common clonal hematopoietic disorder arising in patients with aAA. PNH is caused by mutations in PIGA, a gene that encodes the catalytic subunit of an enzyme involved in the biosynthesis of GPI anchors, transmembrane glycolipids required for cell surface expression of many proteins. PNH clones likely arise as immune escape mechanisms in aAA by preventing CD1D-restricted T-cell recognition of GPI anchors and GPI-linked autoantigens. Though many patients with aAA treated with IST will develop subclinical PNH clones, only a subset will develop PNH disease, characterized by increased thrombosis, intravascular hemolysis, and potential for severe organ dysfunction. In contrast to IST, allogeneic HSCT for patients with aAA is thought to cure bone marrow aplasia and prevent hematopoietic clonal evolution to PNH. Herein, we present a phenomenon of host-derived PNH disease arising in a patient with aAA many years following MSD-BMT, highlighting the importance of monitoring for this clonal disease in aAA patients with stable mixed donor/recipient chimerism after HSCT. We also provide a literature review for similar occurrences of PNH arising after HSCT.

Introduction Grade (gr) 2-4 mucositis complicates myeloablative (MAC) allogeneic hematopoietic transplantation (HCT) in 90% of patients. Methotrexate (MTX) GVHD prophylaxis (ppx) contributes to mucositis and delays engraftment. Severe mucositis increases patient-controlled analgesia (PCA) and TPN (total parenteral nutrition) use, length of stay (LOS) and precludes completion of post HCT MTX. Leucovorin (LCV) following MTX is controversial. Objectives To address exacerbation of mucositis by MTX, we implemented routine LCV post MAC alloHCT and compared outcomes with historical controls. The primary endpoint was the duration of gr 2-4 mucositis. Secondary endpoints were the incidence of gr 3-4 mucositis, time to engraftment, TPN and PCA use, LOS, incidence of GVHD and relapse. Methods Thirty-two consecutive adults received MAC alloHCT and MTX ppx with LCV 15 mg PO q6h x 4 doses, 12 h post d+3, +6, and +11 MTX and were compared to 33 consecutive historical controls. Controls did not receive routine LCV, but may have received ≥ 1 dose post d+6 or +11 MTX at physician discretion. Results Baseline characteristics were similar between the groups. All patients received tacrolimus and MTX GVHD ppx, most with Cy/TBI conditioning. Forty percent received peripheral blood stem cells and 60% had a matched unrelated donor. The median age was 46 y and 50% had AML. Thirty percent of controls received ≥ 1 LCV dose (most post d+11 MTX). The mean duration of gr 2-4 mucositis was shorter with LCV vs. control (7.4 vs. 11 d, p = 0.02). A trend towards lower incidence of gr 3-4 mucositis was observed with LCV (34% vs. 58%, p = 0.08). TPN use was similar between groups (25% vs. 36%, p = 0.4), however duration was shorter with LCV (8.6 vs. 21 d, p = 0.02). A trend towards less frequent PCA use was observed with LCV (34% vs. 58%, p = 0.08). Neutrophil engraftment was faster with LCV (17.6 vs. 20 d, p = 0.04) and a trend towards faster platelet engraftment was observed (15 vs. 20 d, p = 0.06). LOS was shorter with LCV (27 vs. 33 d, p = 0.01). LCV did not impact the incidence of GVHD. Relapse was less common in the LCV group (3% vs. 27%, p = 0.01) albeit with a shorter follow up (mean 202 d vs. 560 d). Conclusion Routine LCV addition to MAC alloHCT with MTX ppx shortened the duration of gr 2-4 mucositis, expedited neutrophil engraftment, shortened TPN and LOS and showed trends towards reduction in clinically important endpoints related to mucositis incidence, severity and associated supportive care. Our small sample size and non-randomized design may limit the strength of these conclusions. Differences between the groups may have been biased towards the null as 30% of controls received ≥ 1 LCV dose. LCV ppx warrants prospective evaluation to assess effects on mucositis, engraftment, GVHD, resource utilization and LOS.

The bone marrow failure syndromes (BMFS) are a heterogeneous group of rare blood disorders characterized by inadequate haematopoiesis, clonal evolution, and increased risk of leukaemia. Single nucleotide polymorphism arrays (SNP-A) have been proposed as a tool for surveillance of clonal evolution in BMFS. To better understand the natural history of BMFS and to assess the clinical utility of SNP-A in these disorders, we analysed 124 SNP-A from a comprehensively characterized cohort of 91 patients at our BMFS centre. SNP-A were correlated with medical histories, haematopathology, cytogenetic and molecular data. To assess clonal evolution, longitudinal analysis of SNP-A was performed in 25 patients. We found that acquired copy number-neutral loss of heterozygosity (CN-LOH) was significantly more frequent in acquired aplastic anaemia (aAA) than in other BMFS (odds ratio 12·2, P 0·01). Homozygosity by descent was most common in congenital BMFS, frequently unmasking autosomal recessive mutations. Copy number variants (CNVs) were frequently polymorphic, and we identified CNVs enriched in neutropenia and aAA. Our results suggest that acquired CN-LOH is a general phenomenon in aAA that is probably mechanistically and prognostically distinct from typical CN-LOH of myeloid malignancies. Our analysis of clinical utility of SNP-A shows the highest yield of detecting new clonal haematopoiesis at diagnosis and at relapse.

Acquired aplastic anemia (AA) is a rare life-threatening bone marrow failure syndrome, caused by autoimmune destruction of hematopoietic stem and progenitor cells. Epidemiologic studies suggest that environmental exposures and metabolic gene polymorphisms contribute to disease pathogenesis. Several case–control studies linked homozygous deletion of the glutathione S-transferase theta (GSTT1) gene to AA; however, the role of GSTT1 deletion remains controversial as other studies failed to confirm the association. We asked whether a more precise relationship between the GSTT1 null polymorphism and aplastic anemia could be defined using a meta-analysis of 609 aplastic anemia patients, including an independent cohort of 67 patients from our institution. We searched PubMed, Embase, and the Cochrane Database for studies evaluating the association between GSTT1 null genotype and development of AA. Seven studies, involving a total of 609 patients and 3,914 controls, fulfilled the eligibility criteria. Meta-analysis revealed a significant association of GSTT1 null genotype and AA, with an OR = 1.74 (95% CI 1.31–2.31, P

Dyskeratosis congenita (DC) is a rare inherited telomeropathy most frequently caused by mutations in a number of genes all thought to be involved in telomere maintenance. The main causes of mortality in DC are bone marrow failure as well as malignancies including leukemias and solid tumors. The clinical picture including the degree of bone marrow failure is highly variable and factors that contribute to this variability are poorly understood. Based on the recent finding of frequent clonal hematopoiesis in related bone marrow failure syndromes, we hypothesized that somatic mutations may also occur in DC and may contribute at least in part to the variability in blood production. To evaluate for the presence of clonal hematopoiesis in DC, we used a combination of X-inactivation, comparative whole exome sequencing (WES) and single nucleotide polymorphism array (SNP-A) analyses. We found that clonal hematopoiesis in DC is common, as suggested by skewed X-inactivation in 8 out of 9 female patients compared to 3 out of 10 controls, and by the finding of acquired copy neutral loss-of-heterozygosity on SNP-A analysis. In addition, 3 out of 6 independent DC patients were found to have acquired somatic changes in their bone marrow by WES, including a somatic reversion in DKC1, as well as missense mutations in other protein coding genes. Our results indicate that clonal hematopoiesis is a common feature of DC, and suggest that such somatic changes, though commonly expected to indicate malignancy, may lead to improved blood cell production or stem cell survival. Am. J. Hematol. 91:1227-1233, 2016. © 2016 Wiley Periodicals, Inc.

Introduction: Grade 2-4 mucositis is a major complication after myeloablative (MAC) allogeneic hematopoietic transplantation (HCT) in about 90% of patients. Graft-vs-host-disease (GVHD) prophylaxis with methotrexate (MTX) exacerbates mucositis and delays engraftment. Severe mucositis precludes administration of all 4 MTX doses which increases the risk of GVHD and can prolong hospitalization due to infection, pain control, and the use of total parenteral nutrition (TPN). Leucovorin (LCV) prophylaxis following MTX is advised by the EBMT-ELN adult working group, but not universally accepted given the absence of prospective trials. Our group implemented routine LCV prophylaxis following MAC alloHCT with MTX GVHD prophylaxis in 8/2017. We compared the outcomes of these patients with historical controls. Methods: We treated 22 consecutive adults receiving MAC alloHCT with MTX GVHD prophylaxis with LCV 15 mg PO q6h x 4 doses, starting 12 h after the d +3, +6, and +11 MTX doses. Twenty-nine consecutive patients undergoing similar MAC conditioning and MTX GVHD prophylaxis were retrospectively identified as the control. Routine LCV was not given to control patients, but could have been added following d +6 or +11 MTX to limit toxicity at physician discretion. The primary endpoint was the incidence of grade 2-4 mucositis. Secondary endpoints included the duration of grade 2-4 mucositis, time to engraftment, incidence of neutropenic fever (NF) and bacteremia pre-engraftment, duration of antibacterials for NF, ability to receive all MTX doses, incidence and duration of TPN and patient-controlled analgesia (PCA) use, duration of hospitalization, incidence of acute and chronic GVHD, graft failure, and relapse. Results: Baseline characteristics between the two groups were similar (table 1). All patients received tacrolimus and MTX GVHD prophylaxis with the majority receiving Cy/TBI conditioning. Approximately 30% of controls received ≥ 1 dose of LCV (most following d +11 MTX) to limit toxicity. Although the incidence of grade 2-4 mucositis was similar with between groups (82% vs 91%, p = 0.38), a lower incidence of grade 3-4 mucositis was observed with LCV, although this did not reach statistical significance (32% vs. 55%, p = 0.16). The LCV group had a significantly shorter duration of grade 2-4 mucositis (5.6 vs. 9.7 d, p = 0.01) and less frequent PCA use (32% vs. 62%, p = 0.048). The LCV group needed TPN less often (18% vs. 38%, p = 0.21) and when needed, had a shorter duration of TPN (10 vs. 21 d, p = 0.15), although these findings did not reach statistical significance. The LCV group had a significantly shorter duration of hospitalization (28 d vs. 33.7 d, p = 0.03). Platelet engraftment seemed to be more rapid (16.5 vs 22.2 d, p = 0.097) without reaching statistical significance. The addition of LCV did not appear to impact the incidence of acute GVHD (grade 2-4: 23% vs. 14%, p = 0.47; grade 3-4 14 % vs 3%, p = 0.3) by d +100 or chronic GVHD at 1 year (14% vs. 21%, p = 0.44). No differences were observed in the time to neutrophil engraftment, or in the incidence of nephrotoxicity, hepatotoxicity, graft failure, or relapse between the arms. No other obvious practice change was implemented during the study period that would have been anticipated to impact any of these endpoints. Conclusions: The addition of LCV to MAC alloHCT with MTX GVHD prophylaxis resulted in significant reductions in the duration of grade 2-4 mucositis, frequency of PCA use, and duration of hospitalization compared to a similar historical control. We also observed less frequent grade 3-4 mucositis, more rapid platelet engraftment and less TPN use with LCV, but these findings did not reach statistical significance. Our sample size was small, which may have limited our power to detect small differences between the groups. In addition, about 30% of controls received at least 1 dose of LCV which could have biased our results toward the null. There was no increase in acute or chronic GVHD, graft failure, or relapse risk with the addition of LCV; however follow up remains relatively short. LCV prophylaxis following MTX GVHD prophylaxis warrants prospective evaluation to more definitely assess effects on mucositis, engraftment, GVHD and relapse, as well as to clearly determine the impact on resource utilization such as use of TPN, PCA, and length of hospitalization. Disclosures Frey: Novartis: Consultancy; Servier Consultancy: Consultancy. Gill:Extellia: Consultancy, Membership on an entity's Board of Directors or advisory committees; Carisma Therapeutics: Equity Ownership; Novartis: Research Funding. Perl:Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy; NewLink Genetics: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees. Stadtmauer:Celgene: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Takeda: Consultancy. Porter:Novartis: Other: Advisory board, Patents & Royalties, Research Funding; Kite Pharma: Other: Advisory board; Genentech: Other: Spouse employment.

Idiopathic acquired aplastic anemia (AA) is a rare immune-mediated bone marrow aplasia of unknown etiology. Interestingly, we noted several cases of AA developing after a previous diagnosis of classical Hodgkin lymphoma (HL). Due to the rarity of both HL and AA, we hypothesized that their co-occurrence represents a non-random association that may be etiologically significant. To evaluate this potential association, we analyzed the prevalence, incidence and characteristics of patients with co-occurring AA and HL at our institution and through a systematic literature review. Using a defined search of electronic medical records for patients seen at our institution between 2005 and 2018, we identified 4 patients with severe AA who were also diagnosed with HL. The prevalence of AA in patients with HL at our institution (0.2%; 4 of ~2040) was in agreement with the prevalence of AA in published cohorts of HL patients (e.g., 1 in 138 - 200; p 0.205). Using a conservative incidence measure of AA, we found that patients with HL have a striking, over 20-fold higher incidence of AA compared to the published incidence of AA in the general population (4 in 26,497 person-years vs 2.2 to ~7 in 1,000,000 person-years; p=0.0001). To determine the clinical and pathologic characteristics of AA in patients with a history of HL, we expanded our study by performing a systematic literature review. Using the search terms "Hodgkin lymphoma", "Hodgkin disease", "aplastic anemia" and "pancytopenia" in the PubMed database, we identified 7 cases of associated AA and HL diagnoses published between 1956 and 2007. Patients with other HL complications, such as post-chemotherapy myelosuppression, infections, myelodysplastic syndrome, acute leukemia, and hemophagocytic syndrome were excluded. Of the 11 total cases of AA also diagnosed with HL, the median age at AA diagnosis was 31.5 years (range of 12-49 years), with 80% of patients being male (Figure 1, Table 1). Ten of the 11 patients developed AA after or concurrent with a HL diagnosis. The median interval between HL diagnosis and AA onset was 2 months, ranging from concurrent presentation in 5 patients to a maximum of 14 years after an initial HL diagnosis. Of the 10 patients initially presenting with HL, 3 were treated with ABVD, 4 with MOPP-related regimens, and 2 patients required salvage therapy. There were no unusual hematological or other toxicities due to chemotherapy. At the time of AA diagnosis, none of the patients had marrow involvement with HL, and 5 of 10 patients were in complete remission from HL. Five patients for whom cytogenetic information was available had no cytogenetic abnormalities at AA diagnosis. Among the 4 cases from our institution, 2 had a diagnosis of marginal zone lymphoma (1 treated by splenectomy, 1 by rituximab monotherapy), and 1 had a remote history of testicular carcinoma treated by orchiectomy; all 3 cases were in remission prior to HL diagnosis. There was no family history indicative of bone marrow failure or inherited cancer syndromes. The 10 patients who developed AA concurrent with or after HL had dramatically poor outcomes, with a median survival of 14 months (range of 1 month to not reached) (Figure 1, Table 1). Of these 10 patients, 4 were treated with immunosuppression, 2 with eltrombopag, and 2 received allogeneic bone marrow transplants. Of the 4 patients who received immunosuppression, 1 evolved to MDS/AML 4 months after AA diagnosis. Five patients presented with both diagnoses concurrently: 1 was refractory to immunosuppression and achieved complete remission after receiving an allogenic bone marrow transplant, while 4 were unable to receive standard therapy for either condition. Of the historical cases, 5 of the 7 patients received supportive therapy only; the median survival for these patients was 14 months (range of 1 month to 84 months). In conclusion, the data suggest that patients with HL have a significantly higher incidence of AA compared to the general population. The underlying reason for this association is not known; however, the development of AA after HL, a unique B-cell neoplasm associated with a marked inflammatory component, without having received prior cytotoxic therapy in half of the cases, points to secondary immune dysregulation as the possible etiologic factor for AA pathogenesis. Recognition of this syndrome and improved management algorithms are needed for the management of AA presenting in patients with HL. Disclosures Frey: Novartis: Consultancy; Servier Consultancy: Consultancy. Landsburg:Curis: Consultancy, Research Funding; Takeda: Consultancy. Schuster:Dava Oncology: Consultancy, Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees; Genentech: Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Honoraria, Research Funding; Novartis Pharmaceuticals Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Nordic Nanovector: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Svoboda:Kyowa: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; KITE: Consultancy; TG Therapeutics: Research Funding; Regeneron: Research Funding; Seattle Genetics: Consultancy, Research Funding; Merck: Research Funding. Olson:Novartis: Other: participated in 2 advisory boards in 2018; Merck: Other: participated on an advisory board in 2018; BluebirdBio: Other: participated in an advisory board in 2018.

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only potentially curative therapy for myelofibrosis. Despite improved outcomes, morbidity and mortality of HSCT remain high. Here we examine recent data on patient selection, timing, and outcomes of HSCT in myelofibrosis.While there is a general effort to restrict HSCT to transplant-eligible intermediate-2 and high-risk patients, this group has comparatively worse HSCT outcomes, largely driven by their high transplant-related mortality (TRM). When adjusted for age, reduced intensity conditioning (RIC) has shown superior outcomes compared with myeloablative conditioning (MAC), making RIC-HSCT a viable option for older patients. Emerging concepts include the use of ruxolitinib pretransplant, optimizing MAC to decrease toxicity, and use of posttransplant JAK2-mutant allele burden to guide prophylactic immunotherapy to prevent relapse. The recognition of prognostic significance of somatic mutations in the ASXL1, EZH2, SRSF2, and IDH1/2 genes, and the improved assessment of risk of leukemic transformation have added a new dimension to risk stratification.Improving our understanding of molecular genetics and leukemic transformation holds promise for more precise patient selection for HSCT. Although RIC-HSCT may reduce TRM, further studies are needed to optimize conditioning regimens and to define the optimal timing of HSCT.

Introduction: Severe steroid-refractory (SR) gastrointestinal acute graft-versus-host disease (GI-GVHD) is associated with significant mortality in allogeneic hematopoietic cell transplantation (HCT) recipients. Although numerous agents have been studied for this indication, long-term outcomes remain dismal. Tocilizumab, an interleukin-6 receptor monoclonal antibody, is active in SR GI-GVHD with varying efficacy and impact on survival. Tocilizumab was recently adopted at our center as initial therapy for SR GI-GVHD. Methods: We retrospectively evaluated the efficacy of tocilizumab for the treatment of SR biopsy-proven GI-GVHD in 5 consecutive adult allogeneic HCT recipients between October 2015 and July 2016. All patients had stage IV GI GVHD (Glucksberg criteria) without other organ involvement at time of tocilizumab initiation. Three patients underwent myeloablative conditioning and two reduced-intensity conditioning for a hematologic malignancy (AML n=3; ALL n=1; myelofibrosis n=1). SR GI-GVHD was defined as progressive symptoms after 3 days or no improvement after 7 days of methylprednisolone 2 mg/kg/day. Tocilizumab 8 mg/kg was administered approximately every 2 weeks until achievement of complete response (CR), defined as resolution of all manifestations of GI GVHD, progression or initiation of other therapy. Serum levels of pro-inflammatory cytokines (IFN-γ, IL-2, IL-2R, IL-6, IL-7, IL-15, TNF-α) were measured prior to and after the start of tocilizumab using multiplex arrays. Results: All 5 patients (100%; 95% CI, 0.52 - 1.00) achieved a CR after a median time of 9 days (range, 8 - 13) from tocilizumab initiation. The median time to response onset (improvement in GVHD stage by at least 1) was 1 day (range, 1 - 2). Tocilizumab was administered at a median of 17 days (range 8 - 25) from GVHD diagnosis and 15 days (range, 7 - 18) from initiation of high-dose steroids. The median number of tocilizumab doses administered was 2 (range, 1 - 4). Two patients achieved CR after a single dose and 3 patients required multiple doses of tocilizumab to achieve CR (2 doses n=1; 3 doses n=1; 4 doses n=1). At a median follow up of 5.6 months (range, 2.1 - 8.5) from initiation of tocilizumab, 3 of 5 patients are alive and free of their underlying hematologic malignancy. One patient died from complications related to biopsy-proven liver GVHD that developed after tocilizumab initiation and 1 patient died from polymicrobial sepsis. Serum levels of IL-6 prior to the start of tocilizumab ranged from 4 - 21 pg/mL (normal 0 - 12). As all patients responded, no associations between serum levels of pro-inflammatory cytokines, including IL-6, and tocilizumab response could be identified. Conclusion: Tocilizumab appears to be a highly active agent for the treatment of SR GI-GVHD. Detailed evaluation through prospective clinical trials is warranted. Disclosures Frey: Servier: Consultancy; Amgen: Consultancy; Novartis: Research Funding. Mangan:Incyte: Other: Advisory Board; Novartis: Research Funding. Gill:Novartis: Patents & Royalties, Research Funding. Cohen:Bristol-Meyers Squibb: Consultancy, Research Funding; Janssen: Consultancy. Porter:Novartis: Patents & Royalties, Research Funding; Genentech: Other: Spouse Employment.

The myeloproliferativeneoplasms (MPNs), polycythemia vera(PV), essential thrombocythemia(ET), and primary myelofibrosis(PMF), are clonal stem cell disorders defined by proliferation of one or more myeloid lineages and variable progression to myelofibrosisand leukemia. Portal hypertension (pHTN) occurs in 7-18% of MPN patients and portends a poor prognosis. The most common causes of MPN-associated pHTNinclude splanchnic vein thrombosis (SVT), extramedullaryhematopoiesis (EMH), and nodular regenerative hyperplasia (NRH). pHTNin MPN patients presents similarly to that in patients with cirrhosis, with refractory ascites, gastrointestinal bleeding, and hepatic encephalopathy. Transjugularintrahepatic portosystemicshunt (TIPS) insertion has been used empirically to treat refractory ascites and varicealbleeding in MPN-associated pHTN; however, little data exists on long-term outcomes of MPN patients who have undergone TIPS procedure. To assess the safety and efficacy of TIPS for treatment of pHTNin MPN, we performed a retrospective analysis of outcomes of TIPS procedure in MPN patients at three academic medical centers. Through a defined search of the electronic medical records of the participating institutions, 29 MPN patients were identified who underwent TIPS procedure forpHTNbetween 2000 and 2016. Patients with portal hypertension from causes other than MPN were excluded from the study as were patient with fewer than 6 months of follow-up. Clinical characteristics and long-term outcomes were analyzed. The mean age of the patients was 51.5 years (range 29-86 years) and 65.5% were women. PV and PV-MF were the most common MPN subtypes (58.6%), followed by MPN unclassifiable (20.7%), PMF (10.3%), and ET (10.3%) (Table 1).JAK2V617F mutation was present in all but one patient, while CALR and MPL mutations were detected in one patient each. Budd-Chiari syndrome (BCS) represented the predominant etiology of portal hypertension in 72.4% of patients. Of note, 31% of patients had a multifactorial etiology of portal hypertension. Females with PV comprised 75% of BCS presentations, whereas males with MF comprised 80% of EMH. Indications for TIPS included refractory ascites (86%), esophagealvarices (51.7%), intestinal ischemia (6.9%), and fulminant liver failure (6.9%). All patients demonstrated immediate normalization of portal pressures following TIPS insertion with a covered-uncovered stent-graft. Post-TIPS anticoagulation included warfarin (69%), low-molecular weight heparin (17.2%), andfondaparinux (17.2%). Four patients (13.8%) did not receive anticoagulation following TIPS, two of whom had knownvarices and one who had gastro-intestinal bleeding following TIPS. The majority of patients experienced complete resolution of ascites (96.2%) andvarices (93.3%). Post-TIPS complications included TIPS thrombosis (31.0%; notably these occurred despite anticoagulation), heparin-induced thrombocytopenia (20.7%), low-grade hepatic encephalopathy (20.7%), TIPS stenosis (17.2%), and mild NSTEMI (1 patient). Of the eight patients listed for liver transplant, only one patient required transplant following TIPS. One, two, and three-year overall survival post-TIPS were 96.4%, 92.5% and 85.2%, respectively. Our study represents the largest cohort to date of MPN-associated portal hypertension patients who received TIPS. Our results indicate that TIPS can be performed safely in this high-risk population and can effectively mitigate the clinical consequences of MPN-associatedpHTN. However, the risk of TIPS complications, particularly of thrombosis and hepatic encephalopathy, remains prevalent and must be balanced against the intended clinical benefits. Disclosures Stein: Incyte: Membership on an entity's Board of Directors or advisory committees.

Acquired aplastic anemia (AA) is a rare bone marrow failure syndrome. AA is believed to be immune-mediated, supported by in vitro studies and the success of empiric immunosuppressive therapy. Recently, a chromosomal alteration-copy number-neutral loss of heterozygosity of chromosome arm 6p, the site of the Major Histocompatibility Complex and the Human Leukocyte Antigen (HLA) genes-has been identified as a recurrent somatic change in AA. Clonal hematopoiesis marked by 6p CN-LOH is hypothesized to emerge by immune escape of hematopoietic cells lacking certain HLA alleles. However, because of the large size of the genomic region involved by 6p CN-LOH and the strong linkage disequilibrium among other genes in the region, specific alleles targeted by the immune selection in AA are unknown. In a previous study, we reported two patients with somatic loss-of-function mutations in HLA class I genes, leading us to hypothesize that loss of HLA alleles in AA may be common and likely defines a subset of patients with unique characteristics and disease course. To characterize the prevalence of HLA allele loss in AA, we performed targeted next generation sequencing of HLA-A, B, and C genes, in conjunction with single nucleotide polymorphism array genotyping of bone marrow (BM) or peripheral blood DNA in 74 patients with AA. 52 patients had pediatric-onset AA, and 22 had adult-onset AA. Somatic status of mutations was confirmed by sequencing paired constitutional DNA. Eleven patients (15%) were found to have somatic loss of HLA alleles: 5 patients had 6p CN-LOH, 3 patients had loss-of-function mutations (frameshift, nonsense, or start codon loss) of the HLA class I alleles, and 3 patients were found to have both 6p CN-LOH as well as loss-of-function HLA mutations. HLA loss was more frequent in pediatric-onset AA (9 of 52 patients, 17%) as compared to adults (2 of 22 patients, 9%), although the difference did not reach statistical significance. No HLA mutations were identified in 19 patients with classical Paroxysmal Nocturnal Hemoglobinuria, nor in 20 healthy relatives (p=0.06). Among the 11 patients with somatic HLA loss, 8 patients had evidence of oligoclonal hematopoiesis with several independent clones carrying different alterations of the same HLA allele. Among the 6 patients with loss-of-of function HLA mutations, the median number of HLA mutations per patient was 1.5 (range 1-3). Of the 8 patients with acquired 6p CN-LOH, the median number of distinct 6p CN-LOH events per patient was 2 (range 1-4). In the 3 patients harboring both 6p CN-LOH as well as the loss-of-function HLA mutations, both mechanisms led to the recurrent loss of the same allele. Strikingly, only a few distinct HLA class I alleles were targeted by mutations. The most frequently affected were HLA-B*40:02:01 (5 independent mutations in 2 patients) and HLA-B*14:02:01 (3 mutations in 2 patients, and as well as loss through polyclonal 6p CN-LOH in 2 patients). Additionally, one patient each had loss of HLA-A*68:01:01 and HLA-A*33:03:01 through mutational inactivation as well as through 6p CN-LOH. To investigate whether HLA mutations are sufficient to cause clonal expansion or whether other somatic mutations are required, we performed comparative whole exome sequencing (WES) of paired BM and skin DNA in five patients carrying inactivating HLA mutations. Four of the five patients had no other mutations affecting protein sequence or untranslated regulatory regions. One patient had additional somatic mutations, which were subclonal to and co-segregated with the three independent inactivating mutations in the HLA-B*40:02:01 allele. Serial follow-up confirmed that HLA mutations persisted overtime, with a relative expansion of one of the HLA-B*40:02:01 mutant clones bearing a protein-altering mutation in the BCL9 gene. Our results show that loss of HLA class I alleles is common in AA, second only to PIGA gene mutations. The affected alleles are non-random, with immune selection most commonly targeting HLA-B* 40:02:01 and HLA-B*14:02:01 alleles, providing the first evidence of specificity of immune attack in AA. The resultant hematopoiesis caused by selection of cells with HLA allele loss is typically oligoclonal and commonly occurs in the absence of other somatic mutations. Acquisition of additional mutations can lead to clonal dominance overtime. Further studies are underway to better understand the role of HLA loss in patient outcomes and AA pathogenesis. Disclosures No relevant conflicts of interest to declare.