Abstract: Lenalidomide, an antineoplastic and immunomodulatory drug, has therapeutic activity in acute myeloid leukemia (AML), but definitive studies about its therapeutic utility have been lacking. In a phase 3 study, we compared 2 induction regimens in newly diagnosed patients age 18 to 65 years with AML: idarubicine-cytarabine (cycle 1) and daunorubicin and intermediate-dose cytarabine (cycle 2) without or with lenalidomide (15 mg orally on days 1-21). One final consolidation cycle of chemotherapy or autologous stem cell transplantation (auto-SCT) or allogeneic SCT (allo-SCT) was provided according to a prognostic risk and minimal residual disease (MRD)–adapted approach. Event-free survival (EFS; primary end point) and other clinical end points were assessed. A second random assignment in patients in complete response or in complete response with incomplete hematologic recovery after cycle 3 or auto-SCT involved 6 cycles of maintenance with lenalidomide (10 mg on days 1-21) or observation. In all, 392 patients were randomly assigned to the control group, and 388 patients were randomly assigned to lenalidomide induction. At a median follow-up of 41 months, the study revealed no differences in outcome between the treatments (EFS, 44% ± 2% standard error and overall survival, 54% ± 2% at 4 years for both arms) although in an exploratory post hoc analysis, a lenalidomide benefit was suggested in SRSF2-mutant AML. In relation to the previous Dutch-Belgian Hemato-Oncology Cooperative Group and Swiss Group for Clinical Cancer Research (HOVON-SAKK) studies that used a similar 3-cycle regimen but did not pursue an MRD-guided approach, these survival estimates compare markedly more favorably. MRD status after cycle 2 lost prognostic value in intermediate-risk AML in the risk-adjusted treatment context. Maintenance with lenalidomide showed no apparent effect on relapse probability in 88 patients randomly assigned for this part of the study.

Abstract: Introduction Acute myeloid leukemia (AML) is characterized by uncontrolled proliferation of malignant myeloid progenitor cells in the bone marrow that are arrested in differentiation. In AML, genetic aberrations often involve the same genes and play an important role in risk assessment and treatment of AML. In the WHO classification 2016 (Arber et al., Blood 2016), nine AML subtypes of clinical and prognostic importance are distinguished by distinct and practically mutually exclusive mutations, covering 50-60% of AML cases. By analysing an extended panel of genes, Papaemmanuil et al. (NEJM 2016) developed a purely genomic classification of AML. In this system, 11 groups are defined including 6 entities characterized by chromosomal translocations. Similar as in WHO 2016, these 6 entities each account for less than 5% of AML and are identified by metaphase cytogenetics. Of these 6 entities, 5 groups are defined by fusion genes and one group by inv(3)/t(3;3) leading to overexpression of EVI1. The 5 remaining classes include 4 entities with cytogenetically normal AML defined by mutations in NPM1 (27%), bi-allelic CEBPA (4%), genes regulating RNA splicing, chromatin or transcription (18%) and IDH2 R172 mutations (1%) and one entity characterized by mutations in TP53, a complex karyotype or specific aneuploidies (13%). Although the majority of patients can be classified by this new system, 15% of patients still lack class-defining lesions and expression levels of structurally normal genes, which can also have a decisive prognostic impact, are not considered. We propose that whole transcriptome messenger RNA sequencing provides a single and flexible platform to identify the diversity of genetic aberrations relevant for classification of AML. Methods A panel of hundred AML were analysed and HAMLET (Human AMLExpedited Transcriptomics) was developed as bioinformatics pipeline to detect fusion genes, small variants in thirteen genes, long tandem duplications in FLT3 and KMT2A and overexpression of EVI1. In HAMLET, a new algorithm based on soft clipped reads was developed to detect long tandem repeats in FLT3 and KMT2A. All genetic aberrations called by HAMLET were validated by diagnostic data and targeted re-sequencing. Results The data showed that HAMLET correctly called all genetic aberrations relevant for current classification of AML with high sensitivity and specificity. Moreover, the new soft clipped approach that has been integrated in HAMLET proved to be useful not only to detect long tandem duplications in FLT3 and KMT2A, but also to determine the allelic ratio of mutant-to-wild type FLT3, which is predictive for overall survival. By filtering small variants for predicted importance according to large AML sequencing data sets (Jaiswal et al., NEJM 2017), we classified the 100 AML according to genomic classification and showed that 87 cases were classified in single entities, 4 cases in two subgroups and 9 cases had no class-defining lesions. Of the 9 cases without class-defining lesions, 8 cases had detectable driver mutations and one case had no detectable driver mutation. These numbers perfectly match percentages reported by Papaemmanuil et al. (NEJM 2016). Apart from genetic aberrations that are relevant for current classification of AML, HAMLET also identified additional abnormalities. Of particular interest is NUP98-NSD1 (Hollink et al., Blood 2011), a cryptic fusion gene that is missed by metaphase cytogenetics in three AML with no class-defining lesions, and EVI1 overexpression in 5 cases without inv(3)/t(3;3) including three KMT2A-rearranged AML with extremely poor prognosis (Groschel et al., JCO 2013). Conclusions HAMLET correctly called all genetic aberrations relevant for current classification of AML and provides a wealth of additional information with potential consequences for patient management. In conclusion, HAMLET is a comprehensive and reliable pipeline for RNA sequence analysis that may contribute to better risk assessment and personalized treatment of AML. Disclosures Borras: GenomeScan B.V.: Employment. Janssen:GenomeScan B.V.: Employment.

Abstract: TL in LSCs is significantly shortened at diagnosis of CML and correlates with LSC burden. TL in nonleukemic myeloid cells in deep molecular remission is unaffected by long-term TKI treatment.

Abstract: Abstract 893 Introduction: A European collaborative harmonization study involving 61 laboratories is being conducted under the auspices of the European Treatment and Outcome Study (EUTOS) for CML that aims to facilitate reporting of molecular BCR-ABL quantification results according to the International Scale (IS). The aim of this analysis was to investigate the effectiveness of this process and specifically the stability of conversion factors (CF) over time. Methods: The currently accepted way of adopting the IS is to establish and validate a laboratory-specific CF which is then used to convert local results to the IS. For round 1, preliminary CFs were calculated by centrally distributing standard samples containing 10–20 million WBC approximating to 10%, 1%, 0.1%, and 0.01% BCR-ABL IS. Rounds 2 and 3 were employed to refine the CF calculations using 25–30 CML patient samples from each participating laboratories covering a range of BCR-ABL levels between 0.01% and 10%. Log BCR-ABL values for the same samples were compared between reference and local laboratories applying the Bland-Altman bias plot. In order to judge the stability of each laboratory`s methodology, a CF index (ratio of round 3 CF divided by round 2 CF) was calculated and evaluated according to its capability to achieve optimum concordance of results. Results: Of the 61 laboratories participating in round 1, evaluable patient samples have been provided to date by 56 and 30 laboratories in rounds 2 and 3, respectively. Of the 30 laboratories with complete data, 12 had stable CFs (defined as a CF index within 0.75–1.33) whereas 18 laboratories were outside this range. Comparison of the CFs derived from round 2 with those derived from round 3 revealed better and more consistent concordance between laboratories with stable CFs compared to those with unstable CFs. For the 12 stable laboratories, 79% (round 3 CF) vs 79% (round 2 CF) of the samples were within a 2-fold range (0.5–2.0) and 93% vs 89% were within a 3-fold range (0.33–3.0). For the 18 unstable laboratories, 74% vs 55% of the samples were within a 2-fold range (0.5–2.0), p=0.0005 and 92% vs 77% were within a 3-fold range (0.33–3.0), p=0.0005. 2 of 12 laboratories with stable CFs and 8 of 18 laboratories with unstable CFs indicated changes in either one or more components of their procedures (cDNA synthesis, PCR platform, RQ-PCR protocol) that may have impacted on their CFs. Conclusion: These data indicate that CFs may be unstable in some laboratories even in the absence of significant changes to laboratory protocols. Further, it supports the need for continuous revalidation of CFs. In laboratories with unstable CFs we suggest revalidation within 3 to 6 months whereas those with stable CFs should be assessed on a yearly basis. We also suggest that laboratories with unstable CFs need to rigorously examine their internal processes to identify potential sources of variation. Disclosures: Müller: Novartis: Honoraria, Research Funding. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

Abstract: The HOVON cooperative study group performed a feasibility study of escalated imatinib and intravenous cytarabine in 165 patients with early chronic-phase chronic myeloid leukemia (CML). Patients received 2 cycles of intravenous cytarabine (200 mg/m2 or 1000 mg/m2 days 1-7) in conjunction with imatinib (200 mg, 400 mg, 600 mg, or 800 mg), according to predefined, successive dose levels. All dose levels proved feasible. Seven dose-limiting toxicities (DLTs) were observed in 302 cycles of chemotherapy, which were caused by streptococcal bacteremia in 5 cases. Intermediate-dose cytarabine (1000 mg/m2) prolonged time to neutrophil recovery and platelet recovery compared with a standard dose (200 mg/m2). High-dose imatinib (600 mg or 800 mg) extended the time to platelet recovery compared with a standard dose (400 mg). More infectious complications common toxicity criteria (CTC) grade 3 or 4 were observed after intermediate-dose cytarabine compared with a standard-dose of cytarabine. Early response data after combination therapy included a complete cytogenetic response in 48% and a major molecular response in 30% of patients, which increased to 46% major molecular responses at 1 year, including 13% complete molecular responses. We conclude that combination therapy of escalating dosages of imatinib and cytarabine is feasible. This study was registered at www.kankerbestrijding.nl as no. CKTO-2001-03.

Abstract: miR-139-3p and miR-199a-3p, induced by ICL-induced damage, respectively, cause a loss and gain of hematopoietic progenitors. miR-199a-3p is an onco-microRNA (onco-miR) causing AML in a Cebpa-deficient mouse model. Target genes of miR-199a-3p include PRDX6, RUNX1, and SUZ12.

Abstract: Background Venetoclax (VEN)-based combination therapy with hypomethylating agents (HMA) has been approved for first-line treatment in patients ineligible for intensive treatment based on two randomized trials. There is some evidence for efficacy also in the in relapsed/ refractory setting (R/R), but comparative controlled data is lacking. Here, we report our experience of VEN-Azacitidine (AZA) in R/R AML salvage treatment and bridge to allogeneic cell transplantation (allo-HCT) in fit patients compared to historical data from the Study Alliance Leukemia (SAL) registry (ClinicalTrials.gov Identifier: NCT03188874). Design/Methods We analyzed all patients with R/R AML after initial intensive therapy, who started VEN-AZA salvage treatment at the University Hospital Heidelberg, between October 2018 and October 2020. Patients, who were bridged to allo-HCT were compared in a multivariable analysis to data of R/R AML patients from the SAL registry receiving an allo-HCT. Results: A total of 26 patients (median age 60 years, range 23 to 79) were included. All patients initially received intensive therapy, 16 patients (62%) had been refractory to intensive induction therapy with DA (daunorubicin, cytarabine) (11 patients)/ CPX-351 (2 patients) or to an intensive salvage therapy regime with HAM (2 patients)/ Cytarabin-Bortezomib (1 patient). Ten patients (38%) had morphologic (7 patients) or molecular relapse (3 patients) after intensive first line therapy. The distribution of AML according to WHO-2016 classification was n=10 recurrent genetic abnormalities (n= 7, mutated NPM1; n=1, biallelic CEBPA mutations; n=1, mutated RUNX1; n=1, CBFB-MYH11), n=10 AML with MRC, n=6 AML NOS. According to the 2017 ELN classification, 9 patients (34,5%) had low risk, 8 (31%) intermediate risk and 9 (34,5%) adverse risk disease. All patients received AZA 75mg/m² for 7 days combined with VEN 400mg/day after initial ramp up or a reduced dose of 100mg/day in case of co-medication with azoles in 28 days cycles. Best response was CR/CRi in 58% (n=15), PR in 23% (n=6) patients. Day 30-mortality was 0%, day 60-mortality was 4% (n=1). Allo-HCT was performed in 20 patients (77%). Pre-Allo-HCT remission status was CR/CRi in 11 (55%), PR in 4 (20%) patients and MLFS in 1 patient and 4 patients had active disease (n=3, relapse after achieving CR/CRi on VEN-AZA, n=1 refractory to VEN-AZA.). At the time of analysis 15 (75%) of the 20 bridged patients were alive and 11 (55%) are still in CR resulting in a median relapse-free survival in bridged patients of 406 days, whereas all patients not proceeding to allo-HCT died after a median of 139 days. In total, 63 patients with R/R AML were identified in the SAL-registry proceeding to allo-HCT with non VEN-based salvage attempt. Pre-Allo-HCT remission status was CR/CRi in 18 (28%), PR in 15 (24%), unknown in 13 patients (21%) and 17 (27%) patients had active disease (n=9 relapsed, n=8 refractory). Patients of the SAL registry were younger (median, 55 years; range, 22-75 years) and more patients were ELN-int (low risk, 32%, n=20; int, 52%, n=33, adv, 16%, n=10). Median follow-up in the VEN-AZA and the SAL cohorts were 1.4 years and 4.6 years, respectively. Cox-regression modeling of survival measured from the date of being refractory/relapsed revealed a non-significant effect of the cohorts favoring the VEN-AZA salvage therapy (HR, 0.87, p=0.73). However, stratified univariable survival analysis revealed in trend better survival (p=0.10) in the VEN-AZA compared to the SAL cohort with 77% (95%-CI, 62-95%) and 74% (95%-CI, 57-97%) as well as 84% (95%-CI, 76-94%) and 52% (95-CI, 41-68%) 1- and 2-years survival, respectively. Conclusion: Our data confirms the efficacy of VEN-AZA in patients with R/R AML and underlines its potential as an effective strategy for bridging to successful allo-HCT. Disclosures Unglaub: JazzPharma: Consultancy, Other: travel costs/ conference fee; Novartis: Consultancy, Other: travel costs/ conference fee. Schlenk: Boehringer Ingelheim: Research Funding; AstraZeneca: Research Funding; Roche: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria; Neovio Biotech: Honoraria; Hexal: Honoraria; Daiichi Sankyo: Honoraria, Research Funding; Celgene: Honoraria; Astellas: Honoraria, Research Funding, Speakers Bureau; Abbvie: Honoraria; Agios: Honoraria. Middeke: Janssen: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria; Gilead: Consultancy; Abbvie: Consultancy, Honoraria; Jazz: Consultancy; Pfizer: Consultancy, Honoraria; Sanofi: Honoraria, Research Funding; Astellas: Consultancy, Honoraria; Novartis: Consultancy; Glycostem: Consultancy; UCB: Honoraria. Krause: Siemens: Research Funding; Takeda: Honoraria; Pfizer: Honoraria; art-tempi: Honoraria; Kosmas: Honoraria; Gilead: Other: travel support; Abbvie: Other: travel support. Schliemann: Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Other: travel grants; Astellas: Consultancy; AstraZeneca: Consultancy; Boehringer-Ingelheim: Research Funding; BMS: Consultancy, Other: travel grants; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Haenel: GSK: Consultancy; Jazz: Consultancy, Honoraria; Bayer Vital: Honoraria; Takeda: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy; Celgene: Consultancy, Honoraria. Crysandt: Pfizer: Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria. Fransecky: Medac: Honoraria; Abbvie: Honoraria, Research Funding; Amgen: Honoraria; Takeda: Honoraria; Novartis: Honoraria. Einsele: Janssen, Celgene/BMS, Amgen, GSK, Sanofi: Consultancy, Honoraria, Research Funding. Seggewiss-Bernhardt: Astra-Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; ipsen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; EusaPharma: Honoraria, Membership on an entity's Board of Directors or advisory committees. Platzbecker: AbbVie: Honoraria; Celgene/BMS: Honoraria; Janssen: Honoraria; Novartis: Honoraria; Geron: Honoraria; Takeda: Honoraria. Baldus: Amgen: Honoraria; Celgene/BMS: Honoraria; Jazz: Honoraria; Novartis: Honoraria. Dreger: Bluebird Bio: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; BMS: Consultancy; AbbVie: Consultancy, Speakers Bureau; Janssen: Consultancy; Gilead Sciences: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Riemser: Consultancy, Research Funding, Speakers Bureau; Roche: Consultancy, Speakers Bureau. Müller-Tidow: Pfizer: Research Funding; Janssen: Consultancy, Research Funding; Bioline: Research Funding. Sauer: Takeda: Consultancy, Other: DSMB/SAB Member; Matterhorn Biosciences AG: Consultancy, Other: DSMB/SAB Member; Abbvie: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau. OffLabel Disclosure: off-label use of Venetoclax-based combination therapy in relapsed or refractory AML

Abstract: Budd-Chiari syndrome (BCS) is a rare disorder caused by obstruction of the hepatic veins or the suprahepatic inferior vena cava. Myeloproliferative diseases (MPD) are the most important aetiological factor in BCS. The aim of this study was to evaluate multifactorial aetiology in BCS patients with MPD, to assess potential added value of the recently discovered JAK2 mutation in the diagnostics of MPD in BCS, and to determine the survival of MPD patients in BCS. All patients referred to our university hospital with primary, non-malignant BCS between January 1980 and January 2006 were included in this study (n=40). Median age was 28.4 years (18.4–53.3), 26 patients (65%) were female and in nine patients (23%) additional portal vein thrombosis (PVT) was present. Overall mean follow-up was 7.1 ± 6.9 years. Only two patients were lost to follow-up, of which one MPD patient. In addition to standard MPD work-up according to WHO criteria, JAK2 mutation analysis was performed in 17 patients. MPD was present in 33% of the patients: Polycythemia Vera (n=6), Essential Thrombocythemia (ET) (n=6) and unclassifiable MPD (n=1). JAK2 mutation was identified in seven out of the 17 tested BCS patients (41%). In two patients suspect for ET, but who failed to meet WHO criteria, JAK2 mutation analysis led to the diagnosis of MPD. In 38% of patients with MPD additional pro-thrombotic factors were present. Survival rates in patients with MPD at 1, 5, and 10 years remained constant at 92% (95% CI, 78%–100%). Survival rates in patients without MPD at 1, 5, and 10 years were 89% (95% CI, 77%–100%), 64% (95% CI, 44%–85%) and 53% (95% CI, 28%–79%), respectively. There was no significant difference in survival between the two (P=0.18). Additional PVT was only present in patients without MPD in our population, which may account for the slightly lowered survival of these patients, since more extensive thrombosis in the splanchnic area is associated with poorer survival. In addition, three patients with and one patients without MPD underwent liver transplantation, which may have affected survival rate in favour of MPD patients. In conclusion, we report MPD in 33% of our BCS patients. In 38% of the patients with MPD, additional pro-thrombotic factors were present. These results enforce the necessity of extensive screening for additional pro-thrombotic conditions. Our study clearly confirms the importance of JAK2 mutation analysis in patients with BCS. Long term follow-up did not show a significant difference in survival between patients with and without MPD.