Abstract: Abstract 1715 Twelve participating centers in Austria included 257 unselected, consecutive patients with MDS/CMML or AML, who received azacitidine (AZA) between 02/2007 and 07/2011, in the nationwide Austrian Azacitidine Registry (AAR) of the AGMT-study group. Approval by the national Ethics Committee was obtained. The AAR includes 26 patients with CMML (10 with CMML-1, 16 with CMML-2) and is currently the 2nd largest report on CMML patients treated with AZA, the largest comprising 36 evaluable patients (Costa R. et al., Cancer, June 2011, pp2690). Myeloproliferative CMML (MP-CMML), defined as WBC 〉 13.000/μl at diagnosis, was present in 16/26 patients, whereas 10/26 had myelodysplastic CMML (MD-CMML). Thus, the AAR includes patients for whom AZA is currently not approved by the FDA/EMEA. The AAR includes a high proportion of very old CMML patients (31% 75–79a, 15% 〉 80a). Median age was 75a for both males (n=15) and females (n=11). Patients with various levels of PS were included (ECOG-0 (n=6), ECOG-1 (n=14), ECOG-2 (n=8) and ECOG-3 (n=4)). CMML-patients of the AAR suffered from renal insufficiency (n=8), mild liver disease (n=8), coronary artery disease (n=5), diabetes mellitus (n=5), a prior/concomitant solid tumor (n=3), COPD (n=2) and/or venous thromboembolic disease (n=1), respectively. There was no relevant difference in RBC transfusion dependence (TD) for MP-CMML vs. MD-CMML. However, PLT-TD at diagnosis was lower for MP-CMML (23%) than for MD-CMML (67%). In the 19 patients in whom pretreatment cytogenetics were performed, 15, 4 and 0 could be grouped into IPSS good, intermediate and poor risk categories, respectively. Only 57% of all included CMML-patients were treatment-naïve, whereas the rest were pretreated with ICT (10%), ESA (14%), intensive chemotherapy (21%) and other substances (17%) (mainly hydroxyurea and anagrelide) (numbers add up to more than 100% as several patients were pretreated with more than 1 agent). Thus, this registry more accurately reflects a real-life treatment scenario, than most clinical trials that have strict inclusion/exclusion criteria. Most AZA-cycles were applied s.c. (98%), whereas 2% were applied i.v. Median and mean number of AZA-cycles was 5.5 and 9 (SD 10.61; range 1–43), respectively. The FDA-approved d1-7 schedule was used in 62% of all AZA cycles, whereas the non-approved alternative schedules d1-5, 5-2-2 and ‘others’ were applied in 21%, 12% and 6% of all cycles, respectively. Concerning the number of patients however, 20/26 predominantly received the d1-7 schedule. The FDA-approved target dose (75mg/m2 over 7 days) was achieved in 52% of all cycles and in 17/26 of patients, respectively. Reasons for termination of treatment with AZA were death (33%), disease progression (22%), transformation to AML (11%), no response (6%), toxicity (6%) and other reasons (22%). Any kind of HI was noted in 12/26 (46%) of patients. When looking at each lineage separately, 8/26 had HI-ery, 7/26 HI-PLT and 9/26 HI-neutrophils. 6/14 patients who were RBC-TD and 3/7 patients who were PLT-TD prior to AZA-treatment achieved transfusion independence (TI). In patients, in whom (repetitive) bone marrow aspirations/biopsies were performed for response evaluation (n= 12), the following best marrow responses were observed: CR in 4/12 (33%), marrow CR 1/12 (8%), PR in 2/12 (16%), SD in 4/12 (33%) and primary PD in 1/12 (8%). The OR rate observed prior to 07/2011 was 44% (CR + marrow CR + PR + HI). At the time of writing, 9 patients had received 〈 =2 cycles. When limiting response analysis to patients who received 〉 2 AZA cycles, which is required for achievement of hematologic response by the IWG-criteria, ORR was 66%. These are amongst the highest response rates observed for CMML to date. The median OS was 12.7 months (95%CI 6.9; 19.4). Median OS for patients demonstrating HI was significantly higher than for those who did not (19.4 vs. 5.6 months, p 〈 0.0001). Detailed OS analyses and statistical analyses of various factors known or thought to influence prognosis are currently being analyzed, including MP-CMML vs. MD-CMML, CMML-1 vs. CMML-2, comparison of IPSS cytogenetic risk groups, as well as treatment-naïve vs. pretreated patients. In conclusion, in this population of partly pretreated, comorbid, very old patients with CMML, AZA was well tolerated and yielded substantial clinical and hematological benefit. Disclosures: Pleyer: Celgene: Research Funding. Off Label Use: Azacitidine for treatment of CMML including CMML-1 with transfusion-dependence and MP-CMML. Melchardt:AOP Orphan Pharmaceuticals AG: Research Funding. Egle:AOP Orphan Pharmaceuticals AG: Research Funding. Fridrik:Cephalon: Research Funding. Greil:AOP Orphan Pharmaceuticals AG: Research Funding.

Abstract: Myeloproliferative neoplasms (MPN) are characterized by clonal hematopoiesis, hyperproliferation of myeloid cells, hyperinflammation and immune deregulation. The three classical BCR-ABL1-negative MPN are essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). The disease is driven by JAK2, CALR or MPL somatic mutations in most patients. Drug resistance is a major problem in MPN. Recent data suggest that MPN cells display certain immune checkpoint molecules that may contribute to resistance, including PD-L1. Antibodies targeting the PD1/PD-L1 axis are highly promising anti-cancer drugs. Their potential use in MPN is being explored but it is unclear which MPN subtypes are most suitable for testing in clinical trials. The aim of our project was to assess PD-L1 expression in disease-initiating neoplastic stem cells (SC) and differentiated cells of MPN patients and to develop therapeutic approaches capable of blocking PD-L1 expression in MPN SC. In a first step, PD-L1 expression was assessed by RNA-sequencing of granulocytes of 106 MPN patients and 15 healthy donors (HD). The cohort included 56 PMF, 33 ET and 17 PV patients. For 102 patients data from Human Genome-wide Affymetrix 6.0 SNP arrays were available. We observed a ~5-fold higher expression of PD-L1 mRNA in patients with PV compared to other MPN (P & lt;.01) or HD (P & lt;.01). JAK2-V617F positive ET patients had higher expression of PD-L1 compared to CALR-mutated ET (p & lt;.005) and the same was observed in PMF (p & lt;.01). Other mutations (TET2, DNMT3A) detected by NGS did not affect PD-L1 expression. Since PD-L1 and JAK2 are located on chromosome 9p24, we looked into our previously published dataset of 400 MPN patients analyzed by SNP arrays and found that in all 195 patients with 9p uniparental disomy (UPD) the aberrations covered both genes. As PD-L1 is more centromeric it could represent the second target of 9pUPD which can precede the acquisition of JAK2-V617F in MPN. Granulocytes in JAK2-V617F positive patients with 9pUPD expressed significantly higher levels of PD-L1 compared to patients without 9pUPD (P & lt;.0001; Figure 1A). Moreover, the JAK2-V617F mutational burden significantly correlated with PD-L1 expression (R=.52, P & lt;.0001; Figure 1B). This correlation was lost when cases with 9pUPD were excluded from the analysis (R=.03, P=.9), indicating that the UPD is relevant for PD-L1 upregulation. To investigate PD-L1 surface expression on MPN SC we analyzed CD34+CD45dimCD38- cells isolated from fresh bone marrow (BM) samples of another 51 MPN patients and 7 HD by flow cytometry (FC). MPN patients showed a significantly higher surface expression of PD-L1 on CD34+CD45dimCD38- cells compared to HD (p & lt;.001; Figure 1C). PD-L1 levels on the SC surface were elevated in both JAK2- and CALR-mutated MPN patients compared to HD (p & lt;.001 and P & lt;.005, respectively). PD-L2 was neither expressed in MPN granulocytes nor on MPN SC. CD4+ and CD8+ T-cells from BM samples of 17 MPN patients expressed the PD-L1 receptor PD-1 as assessed by FC. We cultured ex vivo primary MPN cells from 7 JAK2-V617F positive patients and showed that PD-L1 expression on MPN SC spontaneously decreases in culture, that interferon-gamma (IFN-γ) can promote expression of PD-L1 on these cells, and that ruxolitinib and the BRD4-degrader dBET6 block IFN-γ-induced PD-L1 expression in CD34+CD45dimCD38- MPN SC (P & lt;.05). Together, we show that PD-L1 is overexpressed on the surface of disease-initiating MPN SC, that PD-L1 mRNA is overexpressed in granulocytes of MPN patients and that PD-L1 overexpression in granulocytes correlates with the JAK2-V617F mutational burden. In patients with JAK2-V617F positive MPN, 9pUPD leads to further PD-L1 upregulation either through increasing the mutant JAK2 gene dosage, loss of wt-JAK2,or amplification of PD-L1 allele with higher expression. Our data suggest the possibility that 9pUPD and the subsequent elevation of PD-L1 expression may provide an immune escape mechanism and may contribute to positive selection of JAK2-V617F homozygous SC. Ruxolitinib and dBET6 downregulate PD-L1 expression on MPN SC suggesting a role for the JAK2 and BRD4-MYC pathway. As recent studies revealed an immunogenic potential of JAK2 and CALR mutants, overcoming the disease-mediated immune escape may be of particular importance. Further preclinical and clinical studies are now required to examine the value of PD1/PD-L1 inhibitors in patients with MPN. Disclosures Gisslinger: Celgene: Honoraria; MyeloPro Diagnostics and Research: Honoraria; AOP Orphan Pharmaceuticals AG: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; PharmaEssentia: Honoraria; Janssen-Cilag: Honoraria; Roche: Honoraria. Kralovics:AOP Orphan Pharmaceuticals AG: Honoraria; PharmaEssentia: Honoraria; Qiagen: Honoraria; Novartis: Honoraria; MyeloPro Diagnostics and Research: Current equity holder in private company. Valent:Allcyte GmbH: Research Funding; Pfizer: Honoraria; Cellgene: Honoraria, Research Funding.

Abstract: Background In myelodysplastic syndromes (MDS), chronic myelomonocytic leukemia (CMML) and acute myeloid leukemia (AML), achievement of morphologic complete response (CR) is a prerequisite for potential cure. In AML, CR is deemed the major outcome associated with improved overall survival (OS); patients (pts) without CR are considered non-responders, and hematologic improvement (HI) without bone marrow blast (BMB) clearance is considered treatment (trt) failure (Cheson 2003). Evidence suggests that these definitions may not be applicable to older pts treated with hypomethylating agents (HMA), and that achievement of CR may not be necessary for prolonged OS (Pleyer 2013, 2014, 2015; Schuh 2015; Bloomfield 2018). IWG response criteria for HI do not differentiate between pts who qualify for response (QFR) vs those that do not. Pts with 'normal' blood counts at trt start are per definition HI non-responders. This may obscure potential survival benefits of responding pts. Aims 1) Assess the impact of HI irrespective of BMB clearance and excluding immortal time bias via landmark analyses. 2) Differentiate between pts who QFR, and those with 'normal' baseline values (not-QFR) defined according to IWG prerequisites for CR. 3) Introduce 3 new categories of HI: peripheral blood blasts (PBB), elevated white blood cells (WBC), and PB-CR (defined as Hb ≥11 g/dl, ANC ≥1.0 G/l, WBC 〈 15 G/l, PB blasts: 0%) in analogy to the concept of complete hematologic response in chronic myelogenous leukemia. Methods 1301 consecutive pts with azacitidine (AZA) trt were analyzed (NCT01595295). Data cut-off 26.07.19. HI was assessed according to IWG criteria (Cheson 2006) and the definitions specified in 3) above. More recent proposals of revision for low-risk MDS pts included in trials (Platzbecker 2018) remain largely idem. Human errors in HI assessment for each AZA cycle and lineage were excluded by automated computational calculation from electronic case report form (eCRF) data. Landmark analyses were performed at 3 months (mo) (HI requires ≥8 weeks response duration) and 6 mo (91, 92 and 88% of MDS, CMML and AML pts respond by cycle 6 [Silverman 2011; Pleyer 2013, 2014]). Statistics were performed by Unidata Geodesign GmbH using DeployR Open 8.0.0. Results In total, 462, 113, and 720 pts had MDS, CMML and AML (n=6 unknown). At AZA start, median age was 73 (range 23-93) years. One, 2 or 3 cytopenias were present in 25, 41 and 29% of pts and 46% were transfusion dependent. 55% received AZA 1st line (26% of whom received prior growth factors or iron chelators). Median AZA dose was 889 mg/cycle and 73 mg/m2/day. Median time to 1st response was 3.0 mo and 95% of pts responded by cycle 6. During AZA trt 1091 BM evaluations (BME) were performed in 599 (46%) pts. At the 3 (6) mo landmark, 44% (47%) of pts with BME achieved CR or CR with incomplete blood count recovery (CRi). Early mortality was 5.6 and 10.3% at 30 and 60 days. Of 932 (598) pts that met the 3 (6) mo landmark, a total of 39% (25%) had no BME. The impact of HI on OS became smaller the later the landmark (Tables 1 and 2). The impact of response on OS was 0.4-4.4 mo longer and significance at the 6 mo landmark was retained using IWG criteria with (Table 1) vs without (Table 2) differentiating between pts who did or did not QFR. Pts who did not QFR had similar or better OS compared with responders. At the 3 mo landmark, proposed additional response parameters HI-PBB, HI-elevated WBC and PB-CR were assoc. with a survival benefit of +7.4, +5.0 and +12.9 mo (Table 1, Fig 1A-C). Conclusions 1) The impact of HI on OS is overestimated without landmark analyses. Median time to 1st response was 3.0 mo and ≥8 weeks response duration required. We therefore suggest using a 3 mo landmark when assessing HI. 2) Using IWG criteria for HI assessment underestimates the impact of response, as non-responders are diluted by pts who do not QFR. Distinguishing QFR/not-QFR seems necessary. 3) Proposed additional HI categories (HI-PBB, HI-elevated WBC, PB-CR) add value to current response criteria. It is often the case that BME are not performed in elderly pts in real-world settings (Dinmohamed 2015; current study). Achievement of HI in any lineage and especially PB-CR might be used as a surrogate for response in pts unable or unwilling to undergo BME for response assessment. This large and growing database is suitable to allow future validation of potential novel response criteria. Disclosures Pleyer: Celgene: Other: Advisory board; Novartis: Other: Advisory board; Inflection Point Biomedical Advisors: Other: Advisory board; Agios: Other: Advisory board; Abbvie: Other: Advisory board. Pfeilstocker:Novartis: Consultancy, Honoraria; Janssen-Cilag: Honoraria; Celgene: Consultancy, Honoraria. Stauder:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Teva (Ratiopharm): Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board, Research Funding. Heibl:Daiichi Sankyo: Honoraria; Pfizer: Honoraria; Mundipharma: Honoraria; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: 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; AOP Orphan Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Sill:Astex: Other: Advisory board; Novartis: Other: Advisory board; AbbVie: Other: Advisory board; Astellas: Other: Advisory board. Girschikofsky:Pfizer: Honoraria, Research Funding; Mundipharma: Consultancy, Honoraria. Petzer:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Roche: Other: Personal fees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Vallet:MSD: Honoraria; Pfizer: Honoraria; Roche Pharmaceuticals: Consultancy. Geissler:Abbvie: Honoraria; Pfizer: Honoraria; Amgen: Honoraria; AstraZeneca: Honoraria; AOP: Honoraria; Celgene: Honoraria; Novartis: Honoraria; Roche: Honoraria; Ratiopharm: Honoraria. Sperr:Novartis: Honoraria; Celgene: Consultancy, Honoraria. Leisch:Novartis: Honoraria, Other: Travel support; Celgene: Other: Travel support; Bristol-Myers-Squibb: Honoraria. Egle:Celgene: Honoraria, Other: Advisory board and Travel support. Melchardt:MSD: Honoraria; Merck: Honoraria, Research Funding; Takeda: Honoraria; Janssen-Cilag: Honoraria; Roche: Honoraria; Novartis: Honoraria; Cephalon: Research Funding. Piringer:Amgen: Research Funding; Roche: Other: Travel support; Merck: Other: Travel support; Bayer: Research Funding. Zebisch:Roche: Honoraria; Novartis: Honoraria, Other: Advisory board; Celgene: Honoraria; AbbVie: Other: Advisory board. Machherndl-Spandl:Celgene: Other: Advisory board. Wolf:Celgene: Honoraria, Research Funding; Abbvie: Honoraria. Keil:Bionorica: Honoraria, Research Funding; Roche: Honoraria; Pfizer: Honoraria; Celgene: Honoraria; AbbVie: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Daiichi Sankyo: Honoraria; Novartis: Honoraria; Merck: Honoraria, Research Funding; Takeda: Honoraria, Research Funding. Greil:Ratiopharm: Research Funding; MSD: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Novartis: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Cephalon: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Gilead: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Pfizer: Honoraria, Research Funding; Bristol-Myers-Squibb: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Genentech: Honoraria, Research Funding; Merck: Consultancy, Honoraria, Research Funding; Eisai: Honoraria; Mundipharma: Honoraria, Research Funding; Sanofi Aventis: Honoraria; Takeda: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; GSK: Research Funding; Sandoz: Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Janssen-Cilag: Honoraria; Amgen: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Roche: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Boehringer Ingelheim: Honoraria. OffLabel Disclosure: Azacitidine is not approved for the treatment of MP-CMML, CMML with 〈 10% BM blasts and IPSS low-risk MDS in the EU

Abstract: The classical BCR-ABL1-negative myeloproliferative neoplasms (MPN) are characterized by over-production of myeloid cells, disease-related mutations in certain driver-genes (JAK2, CALR, MPL) and an increased risk to transform to secondary acute myeloid leukemia (sAML). Although considered stem cell-derived neoplasms, little is known about the phenotype and functional properties of disease-initiating neoplastic stem cells (NSC) in MPN and sAML. Recent data suggest that MPN NSC reside in a CD34+ fraction of the malignant clone. Therefore, these cells are considered most critical target populations to be examined for expression of molecular and immunological targets with the aim to develop improved or even curative NSC-eliminating therapies, such as antibody-based or CAR-T cell approaches. Using a panel of monoclonal antibodies (n=40) and multicolor flow cytometry, we established the immunological phenotype and target expression profiles of putative CD34+/CD38─ NSC and CD34+/CD38+ progenitor cells in patients with polycythemia vera (PV, n=18), essential thrombocythemia (ET, n=29), primary myelofibrosis (PMF, n=38) and post-MPN sAML (n=11). In almost all patients, the putative MPN stem cells expressed the stem cell invasion receptors Hermes (CD44) and ADGRE5 (CD97), C1qR1 (CD93), the migration/adhesion receptor MIC2 (CD99), and the stem cell antigen AC133 (CD133). Contrasting normal stem cells, MPN NCS and sAML stem cells failed to express Thy-1 (CD90). Among the cytokine receptors tested, MPN NSC invariably displayed the TGFßR-related antigen endoglin (CD105), TPOR (CD110), SCFR KIT (CD117), IL-3RA (CD123), CXCR4 (CD184) and IGF-1R (CD221). NSC expressed particularly high levels of KIT and low levels of TPOR and IGF-1R. The IL-2RA (CD25) was identified on NSC in most patients with PMF and sAML, and in a few with ET, but not in patients with PV. Similarly, the GM-CSFR (CD116) was found to be expressed on NSC in most patients with PMF, a few with ET and no with PV. MPN NSC did not exhibit substantial amounts of M-CSFR (CD115), IL-3RB (CD131), FLT3 (CD135), NGFR (CD271) VEGFR-2 KDR (CD309), EPOR, MET or OSMRB. The CD34+/CD38+ MPN progenitor cells displayed a similar profile of cytokine receptors. In addition, MPN and sAML progenitor cells expressed IL-1RAP and CLL-1 in most donors examined. We next examined the expression of various immunological targets and resistance-mediating immune checkpoint antigens on NSC and MPN progenitor cells. In all MPN patients and all sAML patients tested, NSC were found to express substantial amounts of Siglec-3 (CD33) and low levels of Campath-1 (CD52) and MDR-1 (CD243). In addition, MPN NSC and sAML stem cells invariably displayed the "don't eat" me checkpoint IAP (CD47) and the classical checkpoint PD-L1 (CD274). Exposure to interferon-gamma (200 U/ml, 24 hours) resulted in an upregulation of PD-L1 on NSC. In a subset of patients, MPN NSC expressed low levels of HB15 (CD83). In contrast, MPN NSC and sAML stem cells failed to express B7-1 (CD80), B7-2 (CD86), PD-L2 (CD273) and PD1 (CD279). MPN progenitor cells and sAML progenitors expressed an identical profile of cell surface targets and checkpoint antigens. Finally, we confirmed the disease-initiating capacity of MPN stem- and progenitor cells (CD34+ cells) using primary PMF cells in xenotransplantation experiments employing NSGS mice expressing human interleukin-3 (IL-3), granulocyte/macrophage colony-stimulating factor (GM-CSF) and stem cell factor (SCF). After 28 weeks post injection, engraftment of human CD45+ cells in the bone marrow of NSGS mice was found in 15/15 mice injected with bulk mononuclear cells (MNC) containing CD34+ cells and in 0/15 NSGS mice injected with MNC depleted of CD34+ cells. Together, MPN NSC reside in a CD34+ fraction of the malignant clone and display a unique phenotype, including cytokine receptors, immune checkpoint molecules and other target antigens. The phenotypic characterization of neoplastic stem cells should facilitate their enrichment and the development of NSC-eradicating treatment concepts in MPN. Disclosures Valent: Allcyte GmbH: Research Funding; Pfizer: Honoraria; Cellgene: Honoraria, Research Funding.

Abstract: Myelodysplastic syndromes (MDS) are a group of clonal myeloid neoplasms characterized by ineffective erythropoiesis, peripheral cytopenia(s), and an increased risk to transform to secondary acute myeloid leukemia (AML). The prognosis in MDS is variable and depends on the variant of disease, other disease-related features, and patient-related parameters. In the present study, the influence of comorbidity on survival and AML evolution was analyzed retrospectively in 582 patients (270 females and 312 males, f/m ratio: 1:1.2) with de novo MDS (observation period: 1985–2007). The median age was 71 years (range 18–96 years). Of the 582 patients, 275 died so far. The median survival (OS) of all patients was 3.12 years, and the median event-free survival (EFS) was 2.3 years. The median AML-free survival (AFS) was not reached. All in all, 127 patients (22%) developed secondary AML after a median time of 9.7 months (range 0.3–116.6 months). Two different scoring systems for comorbidity, the hematopoietic stem cell transplantation comorbidity index (HCT-CI) and the Charlson comorbidity index (CCI) were applied. As assessed by log rank test, the overall survival (OS) was found to differ among patients in the three different HCT-CI risk groups (p & lt;0.05) and among patients in the four different CCI risk groups. By univariate analysis, the HCT-CI was found to be of prognostic value for OS and EFS in patients meeting WHO- or FAB criteria (p & lt;0.05). The CCI was also found to be of prognostic value for OS in patients diagnosed according to either WHO or FAB criteria (p & lt;0.05). With regard to EFS, the CCI was a prognostically significant variable only for patients meeting WHO criteria (p & lt;0.05), but not in patients diagnosed according to FAB criteria (p & gt;0.05). Calculating AML-free survival (AFS), neither the CCI nor the HCT-CI were of prognostic significance (p & gt;0.05). To evaluate whether comorbity is an independent prognostic parameter in patients with MDS, multivariate analyses were performed. These analyses included the HCT-CT or the CCI together with IPSS, LDH, and the patients’ age. In these analyses, chronic comorbid conditions were found to be independent prognostic risk factors concerning OS and EFS, but not concerning AFS. Specifically, the HCT-CI was an independent prognostic parameter regarding OS (p & lt;0.05) and EFS (p & lt;0.05) for patients diagnosed according to WHO- or FAB-criteria. In contrast, the CCI was of prognostic significance regarding OS for patients meeting WHO- or FAB-criteria, whereas the CCI was not found to be an independent prognostic factor regarding EFS (p & gt;0.05). Regardless of the score applied (HCT-CI or CCI), the highest predictive value of comorbidity was observed in IPSS low risk patients (p & lt;0.05) concerning OS. Of the other variables included in our multivariate analysis, the IPSS was an independent prognostic parameter for OS, EFS, and AFS. Interestingly, age was an independent prognostic variable for OS and EFS, but not concerning AFS, similar to the impact of comorbidity, whereas LDH was an independent predictive factor concerning EFS and AFS. Together, our data show that comorbidity is an independent risk factor for survival in patients with MDS. Therefore, comorbidity should be considered as an important co-variable in the risk assessment in MDS and in the overall treatment plan in these patients.

Abstract: In myelodysplastic syndromes (MDS) cytogenetic analysis has a major role to assess the individual risk of patients. According to the International Prognostic Scoring System (IPSS) three cytogenetic subgroups can be distinguished: favorable [-y,del(5)(q),del(20)(q)], poor [chr. 7 abnormalities, complex] and intermediate [other abnormalities]. In a multicenter analysis the prognostic impact of karyotypic patterns in a series of 1159 primary MDS patients with cytogenetic data was investigated. Aim of the presented analysis was to study the influence of age and gender on this prognostic model. Median age was 66 years, median survival 37 months, 654 patients (56,4%) were male and 505 (43,6%) female. According to the three cytogenetic riskgroups defined by the IPSS the distribution and the median survival duration were as follows: favorable 739 pts. (63,8%), 53 months; intermediate 206 pts. (17,8%), 31 months; poor 214 pts. (18,4%), 11 months. These results are concordant with other published data, especially the original publication of the IPSS. Focussing on age and gender we divided the whole patient cohort in 4 subgroups:male, female, age at time of diagnosis 〈 66 years (579 pts.) and ≥ 66 years (580 pts.) The distribution and survival data are shown in table 1. Risk distribution was comparable among all different subgroups. Analysis of the influence of gender showed significant shorter survival for men in the low risk group, in the other two subgroups median survival duration was not significantly different in favor of the male cohort (interaction p=0.0057). In the two different age groups the younger subgroup with favorable or intermediate cytogenetics lived significantly longer, in the high risk group survival difference was not significant, but substantially the same as in the other risk groups. The observed difference in the low risk subgroup between men and women could be due to a considerable higher frequency of del(5)(q) in female patients (60 females of 83 cases). The shorter survival of the older patient cohorts with favorable or intermediate cytogenetics could be due to non-hematological comorbidity, which has more impact on survival in the lower risk subgroups, while the disease itself is the predominant factor limiting lifetime in the elderly high risk group as defined by cytogenetics. Table 1 Female Male P (sex) 〈 66 years ≥66 years P(age) Favorab. n(%), survival 314(62,2%) 70mo 425(65%) 40mo 〈 0.00001 348(60,1%) 58mo 391(67,4%) 48mo 0.001 Intermed. n(%), survival 86(17%) 30mo 120(18,3%) 33mo 0.70 117(20,2%), 40mo 89(15,3%) 27mo 0.008 Poor n(%), survival 105(20,8%) 10mo 109(16,7%) 13mo 0.81 114(19,7%) 15mo 100(17,3%) 8mo 0.11 P (risk groups) 〈 0.00001 〈 0.00001 〈 0.00001 〈 0.00001

Abstract: Abstract 4266 Twelve participating centers in Austria included 257 unselected, consecutive patients with MDS, CMML or AML, who received azacitidine (AZA) between 02/2007 and 07/2011, in the nationwide Austrian Azacitidine Registry (AAR) of the AGMT-study group. This registry was approved by the national Ethics Committee and includes 128 patients with AML of all FAB-subtypes, as well as de novo AML (39%), t-AML, MDS-AML and post-CMPD-AML. This registry comprises a large number of patients with 〉 30% bone marrow blasts (83/128) (currently off-label indication for AZA), as well as myeloproliferative AML (35/128), as defined by presence of 〉 10.000 WBC/μ l at diagnosis. The AAR includes a high proportion of very old AML patients (median age 73a, 20% 75–79a, 24% 〉 80a). Although the PS was generally low (22% ECOG-0, 47% ECOG-1), AML patients suffered from coronary artery disease (n=29), renal insufficiency (n=26), diabetes mellitus (n=21), a prior/concomitant solid tumor (n=17), COPD (n=14) and/or mild liver disease (n=13), respectively. Only 40% of all AML-patients included were treatment-naïve, whereas the rest was pretreated with G-CSF (12%), ESA (9%), ICT (3%) revlimid or thalidomide (6%), other agents (11%) and/or intensive chemotherapy (47%), respectively. Thus, this registry more accurately reflects a real-life treatment scenario, than most clinical trials that have strict inclusion/exclusion criteria. In the 93 patients in whom pre-AZA cytogenetics were performed, 56.9%, 25.8% and 17.2% could be grouped into IPSS good, intermediate and poor risk categories, respectively. Of these, 43 patients had MDS-specific cytogenetic aberrations (5q-, +8, -7, -7q, -Y and -20q). Most AZA-cycles were applied s.c. (89%), whereas 11% were applied i.v. Median and mean number of AZA-cycles was 4.0 and 5.6 (range 1–24), respectively. 60% of patients predominantly received the FDA-approved d1-7 schedule, whereas the non-approved alternative schedules 5-2-2, d1-5 and ‘others’ were most often given in 17%, 16% and 7% of patients, respectively. The FDA-approved target dose (75mg/m2 over 7 days) was achieved in 58% of all cycles and in 61% of patients, respectively. Longitudinal repetitive analysis of serum GOT, GPT, bilirubin and creatinine over up to 24 cycles shows no relevant variation or worsening tendency of these parameters during treatment with AZA, including patients with reduced baseline renal and/or hepatic function. Reasons for termination of treatment were death for any reason (26%), disease progression or relapse (27%), no response (6%), toxicity (7%), recurrent infectious complications (2%) and other reasons (23%). Adverse events will be presented in detail (number, grade, duration, hospitalization rate, effects on AZA (dose reductions/treatment pause/termination)). Any kind of hematologic improvement (HI) was noted in 38% of patients. When looking at each lineage separately, 21/128 had HI-ery, 23/128 HI-PLT and 24/128 HI-neutrophils. 35/85 patients who were RBC-TD and 19/55 patients who were PLT-TD prior to AZA-treatment achieved transfusion independence (TI). In patients, in whom (repetitive) bone marrow analyses were performed for response evaluation (n= 56), the following best marrow responses were observed: CR (19.6%), marrow CR (7.1%), PR (33.9%), SD (30.4%) and primary PD (8.9%). At the time of writing, 35 patients had received ≤2 cycles. This number largely accounts for the patients in whom no bone marrow response evaluation was performed. The OR rate observed prior to 07/2011 was 38% (CR + marrow CR + PR + HI). When limiting response analysis to patients who received ≥2 AZA cycles, which is required for achievement of hematologic response by the IWG-criteria, ORR was 57%. The median OS was 9.5mo (95%CI 8.15–10.9). In univariate analyses, ECOG 〉 =2 (p=.0026), circulating blasts (9.3 vs. 24.8mo; p=.0014), IPSS poor risk cytogenetics (p=.0037) and failure to achieve any HI (8.6 vs. 22.4mo; p=.0001), significantly negatively impacted OS. Prior treatment with G-CSF and/or ESA, age 〉 80a, WBC 〉 10G/l, BM blasts 〉 30%, LDH 〉 225U/l, number of cytopenic lineages as well as RBC-TD and/or PLT-TD at baseline, did not significantly impact OS (p 〉 0.05) (detailed statistics will be presented). In conclusion, in this population of partly heavily pretreated very old patients with AML, AZA was well tolerated and yielded substantial clinical and hematological benefit, irrelevant of baseline BM blast or PB WBC count. Disclosures: Pleyer: Celgene: Research Funding. Off Label Use: Azacitidine for treatment of AML including patients with 〉 30% bone marrow blasts. Egle:AOP Orphan Pharmaceuticals AG: Research Funding. Fridrik:Cephalon: Research Funding. Greil:AOP Orphan Pharmaceuticals AG: Research Funding.

Abstract: Abstract 945 In 2001, the WHO defined the category MDS with del(5q) due to unique cytogenetic, morphologic, hematologic, clinical, prognostic and therapeutic features. The survival of these patients, as well as patients with refractory cytopenia with unilineage dysplasia (RCUD) and refractory anemia with ring sideroblasts is favorable in comparison to other MDS types. Data on disease progression to a more advanced MDS category or to acute leukemia (AML) are sparse and have not been examined in detail. In order to address this issue we collated data of all patients with MDS and del(5q) characterized by low or intermediate-1 IPSS risk score that had been included into various collaborating MDS registries. Patients were followed from diagnosis and data on cell counts, transfusion dependency, and MDS progression were documented. No patients received treatment other than best supportive care. The status of 62 patients was censored at the time of the initiation of Lenalidomide therapy. AML progression was defined as 〉 20% marrow blasts. Estimates of survival probability were calculated with the Kaplan-Meier method. The cumulative incidence of progression to AML was calculated both with the Kaplan-Meier method and with the competing risk method where “death without progression to AML” is considered as competing event, not as censoring. For both events the cumulative incidences are estimated simultaneously. This method has the advantage that it takes into account that there is a difference between end of follow-up and death. Depending on the number of competing events, the curves are lower than those calculated with the Kaplan-Meier estimator. We identified 303 patients, median age at diagnosis 65 years (28-91), 71% were females. Median follow up time was 3 years. Median survival was 71.5 months. Patients with del(5q) as a sole chromosomal aberration had a median survival of 73 months as compared to 19.3 months in patients with more than 1 additional aberrations. Patients who had red cell transfusion need at diagnosis had a median survival of 39 months vs. 97 months in transfusion independent patients (p=0.00005). Transfusion need at diagnosis was the most important parameter for survival. Patients in the WPSS very low risk group had a median survival of 107 months, as compared to 73 and 56 months in the low and intermediate risk group and 37 months in the high risk group. 44 of the 303 patients (15%) progressed to AML ( 〉 20% marrow blasts). The cumulative AML progression rate calculated with the Kaplan-Meier method was 7% at 2 years and 18.2% at 5 years. The cumulative risk of AML progression calculated with the competing risk method was 6.6% at 2 years and 15.1% at 5 years. Factors associated with the risk of AML transformation were intermediate-I IPSS risk and high risk WPSS score, marrow blast count 〉 5%, and red-cell transfusion need at diagnosis. Survival and progression rates did not differ among the participating centers. In conclusion, survival of patients with MDS and del(5q) is high and is comparable to patients with RCUD and RARS, but is associated with a risk of AML-transformation similar to RCMD without del(5q). Further cytogenetic and molecular studies are warranted in order to identify patients at greater risk of progression. Disclosures: Germing: Novartis, Celgene: Honoraria, Research Funding. Lauseker:Celgene: Research Funding. Hildebrandt:Celgene: Research Funding. Symeonidis:Celgene: Research Funding. Cermak:Celgene: Research Funding. Pfeilstöcker:Celgene: Research Funding. Nösslinger:Celgene: Research Funding. Sekeres:Celgene: Research Funding. Maciejewski:Celgene: Research Funding. Haase:Celgene: Research Funding. Schanz:Celgene: Research Funding. Seymour:Celgene: Research Funding. Weide:Celgene: Research Funding. Lübbert:Celgene: Research Funding. Platzbecker:Celgene: Research Funding. Valent:Celgene: Research Funding. Götze:Celgene: Research Funding. Stauder:Celgene: Research Funding. Blum:Celgene: Research Funding. Kreuzer:Celgene: Research Funding. Schlenk:Celgene: Research Funding. Aul:Celgene: Research Funding. Kündgen:Celgene: Research Funding. Hasford:Celgene: Research Funding. Giagounidis:Celgene: Research Funding.

Abstract: Background In myelodysplastic syndromes (MDS), chronic myelomonocytic leukemia (CMML) and acute myeloid leukemia (AML) achievement of complete remission (CR) is a prerequisite for potential cure. In AML, CR/CR with incomplete recovery (CRi) is deemed the major outcome associated with improved overall survival (OS); patients (pts) without CR/CRi are considered non-responders, and hematologic improvement (HI) without (assessment of) bone marrow (BM) blast clearance is considered treatment (trt) failure. Achievement of CR may not be necessary for prolonged OS in pts treated with azacitidine (AZA) (Pleyer L, Annals Hematol 2014, 1825; Schuh AC, ASH 2015, P575). Outside of clinical trials, BM evaluations (BME) are only performed in ~50% of pts (Dinmohamed, Leuk Res 2015, 177) when either response or progression are obvious from peripheral blood (PB) values, or when pts are unable or unwilling to have BME. Aims To assess of the impact of response type on AZA trt outcomes in multivariate adjusted analyses (MVA). Methods 1441 pts included in the Austrian Azacitidine Registry were analyzed (NCT01595295). Data cut-off was 1 July 21. Marrow response was assessed for MDS/CMML and AML at each BME; HI was assessed on day 1 of each AZA cycle (Döhner H, Blood 2017, 424; Cheson BD, Blood 2006, 419; Pleyer L, ASH 2019, P3821); peripheral blood complete remission (PB-CR) was defined as hemoglobin ³11 g/dL, platelet count ≥100 G/L, neutrophil count ³1.0 G/L, white blood cell count & lt;15 G/L, PB blasts =0%, and no transfusions. Response types were calculated from electronic case report form data. To identify which response type achieved by which AZA cycle had the highest impact on time-to-event endpoints, likelihood ratios (LR) of the Cox-regression model for OS or time to next treatment (TTNT) were calculated using the respective response types as covariates. Baseline characteristics with univariate p & lt;0·10 (n=23) for association with OS were included in the multivariate regression. After stepwise selection n=17 variables remained and were used for MVA. Assign Data Management and Biostatistics GmbH performed statistical analyses with SAS® 9.4. Results In total, 521, 135, and 785 pts had MDS, CMML and AML. Median year of initial diagnosis was 2012, median time to AZA start was 3·0 (IQR 1·0-13·2) months (mo), median follow-up time from AZA start was 10.6 (IQR 4·0-21·1) mo, 894 pts received AZA as first line trt, median age at AZA start was 73 (range 23-99) years. In total, 13956 AZA cycles were applied, median duration of AZA trt was 5·0 (IQR 1·9-12·1) mo, median AZA dose was 875 (IQR 700-1000) mg/cycle, AZA was applied for a median of 7 (IQR 5-7) days. Median time to best response was 3·7 (IQR 2·0-5·9) months. Early mortality was 5.5% within 30 days. During AZA trt 1225 BM evaluations (BME) were performed in 697 (48·4%) of pts. Of these, 204 achieved CR/CRi. Irrespective of BME, 622 (43%) of 1441 pts achieved an HI and 264 (18·3%) of 1441 pts achieved a PB-CR. Pts achieving CR had longer adjusted OS (23·7 vs 19·7 mo, p=0·0227; HR=0·621 [0·413-0·936]) and TTNT (19·4 vs 15·7 mo, p=0·0262; HR=0·644 [0·436-0·949] ) than pts achieving CRi. Among pts achieving CR, those additionally achieving PB-CR had longer adjusted OS (24·8 vs 16·3; p=0·0040; HR=0·256 [0·101-0·647]; Fig 1A) and TTNT (21·2 vs 11·0; p=0·0005; HR=0·219 [0·094-0·513] ; Fig 1B) than those who did not. Among pts not achieving CR, those additionally achieving PB-CR had longer adjusted OS (20·8 vs 14·1; p & lt;0·0001; HR=0·510 [0·397-0·657]; Fig 1A) and TTNT (17·7 vs 10·9; p & lt;0·0001; HR=0·485 [0·357-0·589]; Fig 1B) than those who did not. Among all pts, irrespective of BM blast count, achievement of PB-CR resulted in longer adjusted OS (21·7 vs 10·0 mo; p & lt;·0001; HR 0·363; Fig 1C) and TTNT (18.5 vs 7.8 mo; p & lt;0.0001; HR=0.346; Fig 1D) and provided added value to CR and CR/CRi. Among all response types and after MVA, the highest prognostic impact on both OS and TTNT was observed when achieving PB-CR or CR/CRi by cycle 9 or 10 (Fig 2A-B). Conclusions Above data indicate that achievement of PB-CR is a strong predictor of OS and TTNT that provides additional information to current response criteria. Inclusion of PB-CR in updated response criteria of pts with MDS, CMML or AML receiving non-intensive trt should be considered. The greatest advantage of PB-CR is that it can be easily, nearly painlessly and quickly assessed. Inclusion of PB-CR as an endpoint in clinical trials would be desirable for validation of these results. Figure 1 Figure 1. Disclosures Pleyer: AbbVie, BMS, Novartis: Honoraria, Other: Travel Sport. Pfeilstocker: BMS: Honoraria. Stauder: Celgene/BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Heibl: BMS: Honoraria. Sill: Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees. Hartmann: Celgene, Amgene, Janssen, AbbVie: Honoraria. Petzer: Kite-Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: 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; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: 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; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Saegen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sandoz: 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; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene-BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees. Geissler: BMS: Honoraria. Sperr: AbbVie, BMS-Celgene, Daiichi Sankyo, Deciphera, Incyte, Jazz, Novartis, Pfizer, StemLine, Thermo Fisher: Honoraria, Research Funding. Leisch: Honoraria from BMS, Celgene, Gilead, Takeda and Novartis; Travel support: Celgene and Novartis: Honoraria, Other: Travel support. Melchardt: Abbvie, Celgene, Novartis: Honoraria. Zebisch: Novartis: Consultancy; AbbVie: Consultancy; Celgene: Consultancy, Honoraria. Machherndl-Spandl: AbbVie, Celgene, BMS, Pfizer: Honoraria. Wolf: Roche: Honoraria, Research Funding; MSD: Honoraria, Research Funding; BMS-Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Takeda: Honoraria; Gilead: Honoraria; Incyte: Honoraria; GEMOAB: Honoraria. Greil: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Daiichi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Other: Travel, Accommodations, Expenses, Research Funding; Sandoz: Honoraria, Research Funding. OffLabel Disclosure: Azacitidine is approved for all types of MDS and CMML as well as low blast count AML by FDA, but not for all subtypes of MDS and CMML by EMA.