Abstract: Purpose: The enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase and key epigenetic regulator involved in transcriptional repression and embryonic development. Loss of EZH2 activity by inactivating mutations is associated with poor prognosis in myeloid malignancies such as MDS. More recently, EZH2 inactivation was shown to induce chemoresistance in acute myeloid leukemia (AML) (Göllner et al., 2017). Data on the frequency and prognostic role of EZH2-mutations in AML are rare and mostly confined to smaller cohorts. To investigate the prevalence and prognostic impact of this alteration in more detail, we analyzed a large cohort of AML patients (n = 1604) for EZH2 mutations. Patients and Methods: All patients analyzed had newly diagnosed AML, were registered in clinical protocols of the Study Alliance Leukemia (SAL) (AML96, AML2003 or AML60+, SORAML) and had available material at diagnosis. Screening for EZH2 mutations and associated alterations was done using Next-Generation Sequencing (NGS) (TruSight Myeloid Sequencing Panel, Illumina) on an Illumina MiSeq-system using bone marrow or peripheral blood. Detection was conducted with a defined cut-off of 5% variant allele frequency (VAF). All samples below the predefined threshold were classified as EZH2 wild type (wt). Patient clinical characteristics and co-mutations were analyzed according to the mutational status. Furthermore, multivariate analysis was used to identify the impact of EZH2 mutations on outcome. Results: EZH2-mutations were found in 63 of 1604 (4%) patients, with a median VAF of 44% (range 6-97%; median coverage 3077x). Mutations were detected within several exons (2-6; 8-12; 14-20) with highest frequencies in exons 17 and 18 (29%). The majority of detected mutations (71% missense and 29% nonsense/frameshift) were single nucleotide variants (SNVs) (87%), followed by small indel mutations. Descriptive statistics of clinical parameters and associated co-mutations revealed significant differences between EZH2-mut and -wt patients. At diagnosis, patients with EZH2 mutations were significantly older (median age 59 yrs) than EZH2-wt patients (median 56 yrs; p=0.044). In addition, significantly fewer EZH2-mut patients (71%) were diagnosed with de novo AML compared to EZH2-wt patients (84%; p=0.036). Accordingly, EZH2-mut patients had a higher rate of secondary acute myeloid leukemia (sAML) (21%), evolving from prior MDS or after prior chemotherapy (tAML) (8%; p=0.036). Also, bone marrow (and blood) blast counts differed between the two groups (EZH2-mut patients had significantly lower BM and PB blast counts; p=0.013). In contrast, no differences were observed for WBC counts, karyotype, ECOG performance status and ELN-2017 risk category compared to EZH2-wt patients. Based on cytogenetics according to the 2017 ELN criteria, 35% of EZH2-mut patients were categorized with favorable risk, 28% had intermediate and 37% adverse risk. No association was seen with -7/7q-. In the group of EZH2-mut AML patients, significantly higher rates of co-mutations were detected in RUNX1 (25%), ASXL1 (22%) and NRAS (25%) compared to EZH2-wt patients (with 10%; 8% and 15%, respectively). Vice versa, concomitant mutations in NPM1 were (non-significantly) more common in EZH2-wt patients (33%) vs EZH2-mut patients (21%). For other frequently mutated genes in AML there was no major difference between EZH2-mut and -wt patients, e.g. FLT3ITD (13%), FLT3TKD (10%) and CEBPA (24%), as well as genes encoding epigenetic modifiers, namely, DNMT3A (21%), IDH1/2 (11/14%), and TET2 (21%). The correlation of EZH2 mutational status with clinical outcomes showed no effect of EZH2 mutations on the rate of complete remission (CR), relapse free survival (RFS) and overall survival (OS) (with a median OS of 18.4 and 17.1 months for EZH2-mut and -wt patients, respectively) in the univariate analyses. Likewise, the multivariate analysis with clinical variable such as age, cytogenetics and WBC using Cox proportional hazard regression, revealed that EZH2 mutations were not an independent risk factor for OS or RFS. Conclusion EZH mutations are recurrent alterations in patients with AML. The association with certain clinical factors and typical mutations such as RUNX1 and ASXL1 points to the fact that these mutations are associated with secondary AML. Our data do not indicate that EZH2 mutations represent an independent prognostic factor. Disclosures Middeke: Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees. Rollig:Bayer: Research Funding; Janssen: Research Funding. Scholl:Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Abbivie: Other: Travel support; Alexion: Other: Travel support; MDS: Other: Travel support; Novartis: Other: Travel support; Deutsche Krebshilfe: Research Funding; Carreras Foundation: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees. Hochhaus:Pfizer: Research Funding; Incyte: Research Funding; Novartis: Research Funding; Bristol-Myers Squibb: Research Funding; Takeda: Research Funding. Brümmendorf:Janssen: Consultancy; Takeda: Consultancy; Novartis: Consultancy, Research Funding; Merck: Consultancy; Pfizer: Consultancy, Research Funding. Burchert:AOP Orphan: Honoraria, Research Funding; Bayer: Research Funding; Pfizer: Honoraria; Bristol Myers Squibb: Honoraria, Research Funding; Novartis: Research Funding. Krause:Novartis: Research Funding. Hänel:Amgen: Honoraria; Roche: Honoraria; Takeda: Honoraria; Novartis: Honoraria. Platzbecker:Celgene: Research Funding. Mayer:Eisai: Research Funding; Novartis: Research Funding; Roche: Research Funding; Johnson & Johnson: Research Funding; Affimed: Research Funding. Serve:Bayer: Research Funding. Ehninger:Cellex Gesellschaft fuer Zellgewinnung mbH: Employment, Equity Ownership; Bayer: Research Funding; GEMoaB Monoclonals GmbH: Employment, Equity Ownership. Thiede:AgenDix: Other: Ownership; Novartis: Honoraria, Research Funding.

Abstract: Chordomas are rare bone tumors with few therapeutic options. Here we show, using whole-exome and genome sequencing within a precision oncology program, that advanced chordomas ( n  = 11) may be characterized by genomic patterns indicative of defective homologous recombination (HR) DNA repair and alterations affecting HR-related genes, including, for example, deletions and pathogenic germline variants of BRCA2 , NBN , and CHEK2 . A mutational signature associated with HR deficiency was significantly enriched in 72.7% of samples and co-occurred with genomic instability. The poly(ADP-ribose) polymerase (PARP) inhibitor olaparib, which is preferentially toxic to HR-incompetent cells, led to prolonged clinical benefit in a patient with refractory chordoma, and whole-genome analysis at progression revealed a PARP1 p.T910A mutation predicted to disrupt the autoinhibitory PARP1 helical domain. These findings uncover a therapeutic opportunity in chordoma that warrants further exploration, and provide insight into the mechanisms underlying PARP inhibitor resistance.

Abstract: Most adult gastrointestinal stromal tumors (GIST) are driven by activating KIT or PDGFRA mutations. The remaining 10-15% of cases, often referred to as wildtype (WT) GIST, display either alterations of the succinate dehydrogenase complex (SDH) or RAS pathway mutations. To gain additional insight into the biology of GIST, we performed whole-exome or genome and RNA sequencing in 38 GIST patients (WT, n=15; KIT-mutant, n=21; PDGFRA-mutant, n=2) enrolled in a prospective molecular stratification trial of NCT Heidelberg/Dresden and the German Cancer Consortium (DKTK) designed for younger adults with advanced-stage cancer across histologies and patients with rare tumors (NCT/DKTK MASTER). Of the 15 patients with WT GIST, 3 had pathogenic germline mutations in NF1 and 9 harbored SDH alterations (germline, n=5; somatic, n=4). In the 3 patients with quadruple-negative GIST - defined by the absence of KIT, PDGFRA, SDH, or RAS pathway alterations - we detected novel gene fusions affecting RET, FGFR2, and FGF4, respectively. To delineate biologically relevant subgroups of GIST based on RNA sequencing data from the entire cohort (n=34), we used 3 different clustering methods and 4 different measures of stability and consistency. Despite the underlying clinical and molecular heterogeneity, we identified 3 distinct transcriptional subgroups that were characterized by (i) SDH deficiency, (ii) recurrent somatic RB1 alterations and mutational signatures associated with defective homologous recombination DNA repair, and (iii) elevated PDGFRA expression, respectively. Furthermore, we used random forest analysis to identifiy genes that are significantly (p & lt;0.005) differentially expressed between the 3 subgroups. Interestingly, quadruple-negative cases did not form a separate cluster or clustered within a specific subgroup. Collectively, our data illustrate the molecular heterogeneity of advanced-stage GIST and support comprehensive molecular profiling approaches to capture the entire spectrum of clinically actionable genetic alterations, such as diverse fusion genes affecting kinase signaling pathways in quadruple-negative cases or pathogenic germline mutations in patients with inconspicuous family histories. The finding of two separate transcriptional clusters among patients with SDH-proficient GIST may be reflective of distinct regulatory pathways whose molecular underpinnings and clinical actionability warrant further study. Citation Format: Peter Horak, Matea Hajnic, Laura Gieldon, Mario Hlevnjak, Susan Richter, Barbara Hutter, Johanna Falkenhorst, Sebastian Uhrig, Gregor Warsow, Nagarajan Paramasivam, Stefan Gröschel, Barbara Klink, Simon Kreutzfeldt, Christoph Heining, Christoph E. Heilig, Martina Fröhlich, Stephan Richter, Christian Brandts, Wilko Weichert, Philipp Jost, Olaf Neumann, Marc Zapatka, Albrecht Stenzinger, Alexander Marx, Benedikt Brors, Evelin Schröck, Sebastian Bauer, Peter Hohenberger, Hanno Glimm, Claudia Scholl, Stefan Fröhling. Comprehensive genomic and transcriptomic profiling of gastrointestinal stromal tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1686.

Abstract: Co-senior authors Andrew Brunner and Andrew H. Wei contributed equally to this work Background: MBG453 is a high-affinity humanized anti-TIM-3 (T-cell immunoglobulin domain and mucin domain-3) IgG4 antibody in development for the treatment of MDS, AML, and other malignancies. TIM-3 is an immune checkpoint with a complex regulatory role in both adaptive and innate immune responses and is also preferentially expressed on leukemic stem and progenitor cells, making it a potential target in MDS and AML. MBG453 has been shown to enhance immune cell-mediated killing of AML cells in vitro. Hypomethylating agents (HMAs) have been shown to increase immune checkpoint expression in MDS and AML, providing rationale to study the combination of HMAs with MBG453. Methods: Patients with Revised International Prognostic Scoring System (IPSS-R) high or very high-risk (HR) MDS and newly diagnosed, or relapsed/refractory (R/R), AML following ≥ 1 prior therapy who were not candidates for standard chemotherapy and who were HMA naive were enrolled in this multi-center, open label phase Ib dose-escalation study (NCT03066648). Escalating doses of MBG453 were administered i.v. every 2 weeks (Q2W; days 8, 22) or every four weeks (Q4W; day 8) in combination with decitabine (20 mg/m2; i.v. days 1-5). The primary objectives were to characterize the safety and tolerability of MBG453 in combination with decitabine and to identify recommended doses for future studies. Secondary objectives included assessing preliminary efficacy and pharmacokinetics of the combination. Dose escalation followed a Bayesian logistic regression model based on dose-limiting toxicities (DLTs). Adverse events (AEs) were graded using NCI-CTCAE v4.03. The International Working Group criteria for MDS (Cheson et al, 2006) or AML (Cheson et al, 2003) were used to assess efficacy. Results: As of March 25, 2019, 17 HR-MDS, 4 chronic myelomonocytic leukemia (CMML), and 38 AML patients have received decitabine and MBG453 at 240 mg Q2W (n=22), 400 mg Q2W (n=21), or 800 mg Q4W (n=16). MTD has not been reached. Median age was 70 years (range 23-87 years). 24 patients are ongoing (duration of exposure 1.1 to 18.6 months) with 35 patients discontinued (disease progression [n=19, 32%], AE [n=1, 2%] , patient/physician decision [n=13, 22%], death [n=2, 3%] ). There was one DLT consisting of a grade 3 ALT elevation that was corticosteroid responsive. The most common treatment emergent grade 3/4 AEs were febrile neutropenia (39%), neutropenia (34%), thrombocytopenia (31%), and anemia (29%). A total of 8 patients (14%) developed ≥ grade 2 suspected immune related AEs (irAEs) considered to be MBG453 related; 4 of whom (7%) presented with grade 3/4 events: ALT elevation (n=2), arthritis (n=1), and GGT increase (n=1). No study treatment-related deaths were observed. 16 HR-MDS and 31 AML patients have had post-baseline disease response assessments. Median duration of decitabine and MBG453 is 3.9 months (range 0.7-18.6 months). Evidence of activity with MBG453 in combination with decitabine has been seen at doses ranging from 240 mg Q2W to 800 mg Q4W. 8 of 16 (50%) HR-MDS patients achieved mCR or CR. None of the responding HR-MDS patients has had disease recurrence with exposure durations currently ranging from 3.4 to 18.6 months; two patients in mCR underwent allogeneic stem cell transplant. 4 of 14 (29%) newly diagnosed AML patients have achieved a response of PR or better (2 PR, 2 CR), with 3 additional patients exhibiting ≥ 50% bone marrow blast reduction, and 10 of 14 (71%) continuing on study. 5 of 17 (29%) R/R AML patients have achieved a response of CRi, with 5 additional patients exhibiting ≥ 50% bone marrow blast reduction. Exposure durations for all AML responders currently range from 2.1 to 17.9 months. Median onset of response among all patients was 2.0 months. TIM-3 expression was detected on leukemic cells, with modulation of TIM-3 expression following treatment with decitabine. Conclusions: In this ongoing study in patients with HR-MDS and AML, the combination of MBG453 and decitabine was safe and well tolerated, and exhibited evidence of anti-leukemic activity with encouraging preliminary response rates occurring at a median of 2 cycles, with durability in both HR-MDS and AML. These findings validate TIM-3 as a promising therapeutic target in MDS and AML and support further clinical development of MBG453 in combination with HMAs in patients with MDS and AML. Disclosures Borate: AbbVie: Consultancy; Daiichi Sankyo: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Takeda: Consultancy. Esteve:Novartis: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy; Daiichi Sankyo: Consultancy; Celgene: Consultancy, Speakers Bureau; Jazz Pharmaceuticals: Consultancy; Roche: Consultancy; Astellas: Consultancy, Speakers Bureau; Pfizer: Consultancy. Porkka:Daiichi Sankyo: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Knapper:Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; Tolero: Consultancy; Daiichi Sankyo: Honoraria; Pfizer: Consultancy. Vey:Janssen: Honoraria; Novartis: Consultancy, Honoraria. Scholl:Novartis: Other: Project funding; Pfizer: Other: Advisory boards; Gilead: Other: Project funding; AbbVie: Other: Advisory boards; Daiichi Sankyo: Other: Advisory boards. Garcia-Manero:Amphivena: Consultancy, Research Funding; Helsinn: Research Funding; Novartis: Research Funding; AbbVie: Research Funding; Celgene: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding. Wermke:Novartis: Honoraria, Research Funding. Janssen:Amsterdam University Medical Center, location VUmc, Amsterdam, The Netherlands: Employment; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Other: Founder of the HematologyApp which is supported by BMS, among others, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Founder of the HematologyApp which is supported by Pfizer, among others; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Founder of the HematologyApp which is supported by Incyte, among others; AbbVie: Membership on an entity's Board of Directors or advisory committees; Janssen: Other: Founder of the HematologyApp which is supported by Janssen, among others; MSD: Other: Founder of the HematologyApp which is supported by MSD, among others; Daiichi-Sankyo: Other: Founder of the HematologyApp which is supported by Daiichi-Sankyo, among others; Roche: Other: Founder of the HematologyApp which is supported by Roche, among others; Takeda: Other: Founder of the HematologyApp which is supported by Takeda, among others. Traer:AbbVie: Consultancy; Notable Labs: Equity Ownership; Agios: Consultancy; Astellas: Consultancy; Daiichi Sankyo: Consultancy. Chua:Alfred Hospital, Melbourne, Australia: Employment. Narayan:Takeda: Other: Employment (spouse); Merck: Other: Equity ownership (spouse); Genentech: Other: Equity ownership (spouse). Tovar:Hospital Clinic Barcelona: Employment. Kontro:Amgen: Consultancy; Astellas: Consultancy; AbbVie: Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees. Ottmann:Roche: Honoraria; Pfizer: Honoraria; Fusion Pharma: Honoraria; Takeda: Honoraria; Novartis: Honoraria; Celgene: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Amgen: Honoraria, Research Funding. Sun:Novartis Institutes for BioMedical Research: Employment; Novartis: Other: Novartis stock owner (stock share as long-term employee incentive). Longmire:Novartis Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties. Szpakowski:Novartis Institutes for Biomedical Research: Employment, Other: Novartis Stock. Liao:Novartis: Employment. Patel:Novartis Pharmaceuticals: Employment. Rinne:Novartis: Employment; N-Of-One, Inc: Consultancy. Brunner:Astra Zeneca: Research Funding; Forty Seven Inc: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees. Wei:Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Honoraria, Research Funding; Janssen: Honoraria; Servier: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Macrogenics: 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, Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: AHW is a former employee of the Walter and Eliza Hall Institute and receives a fraction of its royalty stream related to venetoclax, Research Funding, Speakers Bureau; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: MBG453 is an investigational anti-TIM-3 antibody that is being evaluated in hematological malignancies and solid tumors

Abstract: Introduction: Outcome of patients (pts) with refractory AML or following relapse is considered dismal and usually reported as refractory/relapsed. Here we analyzed long term outcome of refractory and relapsing pts separately over a 10 year (y) period from two prospective, non-age-limited, adult AML studies. Results have been published or presented previously as part of the German AML Intergroup studies1,2. However, incidence, characteristics, treatment and outcome of refractory and relapsed pts have not been evaluated. Patients and Methods: A total of 1621 pts from the OSHO 2002 ≤60 y (n=740) and 2004 & gt;60 y (n=881) with newly diagnosed AML (except acute promyelocytic leukemia) and eligible for chemotherapy were analyzed. The gender was male in 51.7% of pts. AML type was de novo in 66.6%, followed by secondary AML in 25.8% and therapy related in 7.6%. Cytogenetic risk status was normal in 47.9%, intermediate in 16.3%, unfavorable in 15.3%, monosomal in 12.6% and favorable in 7.9%. Molecular analysis revealed wildtype (wt) FLT3 in 80.9% and FLT3 ITD mutated (mut) in 19.1% of pts. NPM was mutated in 30.2% of 1124 pts. In the AML 2002 and 2004 studies (NCT 01414231; NCT 01497002; NCT00266136), pts were randomly (9:1) assigned to remission induction by cytarabine (1 g/m2 bid d 1, 3, 5, 7) and Idarubicin (AML 2002) 12 mg/m2/d d 1-31 or mitoxantrone (AML 2004) 10 mg/m2/d iv d 1 - 32 or to a common arm consisting of a 3+7 scheme 3. Pts in complete remission (CR) received consolidation and stem cell transplantation (HSCT) according to cytogenetic risk and donor availability1,2. Pts with partial remission (PR) or non-response (NR) to two induction cycles were considered refractory. Pts achieving CR and relapsing thereafter were considered relapses and treated with MitoFlag or Flag-Ida4. Results: The majority of pts [median age 62 (range 17-87) y] entered CR or CRi after one or two induction cycles (n=1144; 70.6%). OS was 31.9 (29.5-34.4) % @5y and 26.0 (23.4-28.9) % @10y. Results were age dependent and superior in younger pts with an OS of 46.8 (43.1-50.7) % @5y compared to 19.3 (16.7-22.4) % @ 5y in elderly. Age, cytogenetics and NPM1 were determinants for CR and WBC (p & lt;0,001), gender (p & lt;0,05) and AML type (p & lt;0,01) for OS. FLT3-ITD mut was an important determinant for relapse free survival in pts ≤60y. A total of 238 (14.7%) of 1621 pts, 23.5% in the younger and 76.5% in the elderly study, were refractory (PR 60.1%, NR 39.9%). Pts had a median age of 66 (range 23-83)y. OS of refractory pts was 11.4 (7.9-16.6)% @5y, and dependent upon PR [(13.1 (8.1-21.1) % @10y] and NR [5.2 (2.1-12.6) % @5y; p=0.0003] . Intensive chemotherapy ± HSCT and hypomethylating agents (HMA) were able to induce CR in 24.8% of pts. CR and non-CR pts had an OS of 42.7 (31.4-58.2) % @5y and an OS of 3.7 (1.7-8.0) % @2y, respectively. Risk factors for OS in refractory pts were age and type of therapy (p & lt;0.0001). Almost all long term survivors were treated with HSCT. Of the 1144 CR/CRi pts, 582 relapsed 1-121 months (mts) after CR. Relapse occurred in 34.0% ≤6 mts, in 38,8% between 7-18 mts and in 12,2% & gt;18 mts. Age, cytogenetic risk, type of AML, interval CR to relapse and HSCT were the dominant factors for relapse. CR2 was achieved after intensive chemotherapy ± HSCT, ± DLI and HMA in 227 pts (39.0%), 54.5% in the AML 2002 and 28.4% in the AML 2004. OS of relapsed pts was 13.8 (11.1 - 17.3) % @5y and 10.9 (7.4 - 16.2) % @10y and was higher in the younger with 23.4 (18.2-29.9) % @5y as compared to elderly pts 6.9 (4.4 - 11.0) % @5y. Pts with CR2 had a LFS of 24.9 (19.5-31.7) % @5y and was highest in patients & lt;60y when intensive chemotherapy followed by HSCT was involved. Independent risk factors for OS in relapsed pts were age, cytogenetic risk, interval CR1 to relapse and type of therapy. Relapsed pts with HSCT in CR1 showed a trend for reduced survival. Conclusions Outcome of pts with refractory and relapsed AML is unsatisfactory but consistent & gt;10% @5y. A differential response is observed in refractory and relapsed pts and is dependent upon PR, NR and the achievement of CR. Increase of CR rate in younger but especially in elderly pts with second generation TKI, reduction of TRM using FLT3-inhibitor monotherapy and the option to treat pts ineligible to chemotherapy promise better outcome in refractory and relapsed AML. 1Büchner et al. JCO 2012; 2Niederwieser et al Blood 2016; 3Mayer et al. NEJM 1994; 4Thiel et al. Ann Oncology 2015 Disclosures Niederwieser: Daichii: Speakers Bureau; Cellectis: Consultancy. Scholl:Gilead: Other: Project funding; Daiichi Sankyo: Other: Advisory boards; AbbVie: Other: Advisory boards; Pfizer: Other: Advisory boards; Novartis: Other: Project funding. Zojer:Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Sayer:Novartis: Other: none. Schwind:Daiichi Sankyo: Honoraria; Novartis: Honoraria, Research Funding. Maschmeyer:Gilead, Janssen Cilag, Astra Zeneca; BMS, Merk-Serono: Honoraria. Hochhaus:Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; Incyte: Research Funding; MSD: Research Funding. Al-Ali:Celgene: Research Funding; Novartis: Consultancy, Honoraria, Research Funding; CTI: Honoraria.

Abstract: CMV associated tissue-invasive disease is associated with a considerable risk of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Recently, the terminase inhibitor letermovir (LMV) has been approved for prophylaxis of CMV infection in HSCT. We hereby report a 60-year-old female experiencing CMV reactivation after HSCT in a CMV seronegative donor-constellation. Due to ongoing elevated CMV viral load and drug-associated myelosuppression, which prevented ganciclovir therapy, treatment was replaced by foscarnet. Due to nephrotoxicity, foscarnet was switched to LMV. The patient developed skin GvHD and prednisolone was started. Subsequently, CMV viremia worsened despite LMV therapy. Genotyping revealed the mutation C325Y of the CMV UL56 terminase being associated with high-level resistance against LMV. Prolonged uncontrolled low-level viremia due to prednisolone treatment may have favored the selection of drug-resistant CMV. Despite the excellent toxicity profile of LMV, physicians should be aware of risk factors for the emergence of resistance.

Abstract: Background: Despite the recent approval of DNA-hypomethylating agents (HMAs) for treatment of elderly AML patients (pts) ineligible for induction, their prognosis is still poor, and rational, effective HMA-based combination treatments are under study. Histone deacetylase inhibitors (HDACi) show synergism with HMAs in vitro. ATRA - as single agent clinically ineffective in non-M3 AML - in combination with HMAs also shows in vitro synergistic antileukemic activity in non-M3 AML cells. We previously conducted a non-randomized phase II trial in elderly non-fit AML pts with DAC (3-dy schedule), given alone or combined with ATRA (45 mg/m2 dy 4-28, only during course 2), with encouraging results (Lübbert et al., Haematologica 2012). We now expanded this approach to a 4-arm randomized phase II study (2x2 factorial design) asking whether the addition of either VPA (HDACi activity) or ATRA or both to DAC as first-line treatment of elderly AML pts might improve the effect of DAC monotherapy (NCT00867672). Patients and Methods: Inclusion criteria: newly diagnosed pts 〉 60 yr unfit for induction (reasons for treatment decision prospectively captured) with non-M3 AML (WHO, de novo or after antecedent hematologic disorder [AHD], therapy-associated [t] AML), ECOG performance status (PS) 0-2. Pts with 〉 30,000 WBC/µl were to receive a short course of hydroxyurea. Treatment: DAC 20 mg/m2 dy 1-5 (treatment arms A/B/C/D), VPA p.o. continuously (target serum levels: 50-110 mg/l) from dy 6 (arms B/D), ATRA p.o. dy 6-28 (arms C/D) of each 28-dy course (repeated until relapse/progression, prohibitive toxicity, withdrawal or death). Key endpoints: objective response rate (ORR): CR/CRi/PR (ELN criteria), overall survival (OS). Sample size calculation was based on the primary endpoint ORR, assuming an ORR of 25% in arm A (Lübbert et al., Haematologica 2012). For a power of 80% (test in this phase II study at 1-sided alpha=0.1) for an increase of ORR to 40% with VPA or ATRA, 176 pts were necessary, planned sample size 200. Efficacy analyses were performed in the intention-to-treat (ITT) population including all randomized pts for whom treatment was started. VPA was investigated by comparing arms B+D vs arms A+C, ATRA by comparing arms C+D vs arms A+B. ORR was analyzed with logistic regression, OS with Cox regression, without adjustment for prognostic factors. Odds ratios (OR) for the effect on ORR and hazard ratios (HR) for the effect on death with 95% confidence intervals (CI), and two-sided p values of the tests of no treatment effect are presented. Central hematopathological review by an independent morphologist was conducted in a blinded fashion as to treatment arms. Results: Between 12/2011 and 2/2015, 204 pts were randomized (4 were excluded from the analysis because no treatment was administered). Median age: 76 yrs (interquartile range 72-79, range 61-92), ECOG PS 0/1/2-3: 19/61/20%: 52% had an HCT-CI 〉 3, 16.5% WBC 〉 30.000/µl, 31.5% poor cytogenetics (ELN), 51% had an AHD, 13.5% tAML (characteristics overall balanced across all 4 treatment arms). A median of 3 DAC courses were administered (per arm: 2/3/5.5/4), however 53 pts (26.5%), who were older, with reduced PS and a higher HCT-CI compared to the other 147 pts, received only a single course. The ORR (usually achieved only after 〉 3 courses) was 17.5%, median OS 6.2 mths (arm A: 8.5% and 4.8 CI [2.8,7.6] mths, arm B: 17.5% and 6.1 CI [3.7,7.2] mths, arm C: 26.1% and 8.4 CI [4.0,14.0] mths, arm D: 18% and 7.7 CI [4.6,11.2] mths, respectively). Effect on ORR of VPA vs no VPA (17.8 vs 17.2%): OR 1.06, CI [0.51,2.21], p=0.88; of ATRA vs no ATRA (21.9 vs 13.5%): OR 1.80, CI [0.86,3.79] , p=0.12. Effect on OS of VPA vs no VPA (6.2 vs 6.4 mths median OS): HR 0.94, CI [0.70,1.28], p=0.70; of ATRA vs no ATRA (8.2 vs 5.1 months median OS): HR 0.65, CI [0.48,0.88] , p=0.006 (after adjustment for PS, HCT-CI, WBC, LDH: HR 0.59, CI [0.43,0.82], p=0.002). Improved survival with ATRA was also seen in pts with poor cytogenetics. Toxicities (predominantly hematologic) did not show relevant differences between the 4 treatment arms. Conclusions: Based on this ITT analysis of a randomized trial, the addition of ATRA to standard-dose DAC resulted in a higher ORR and in a clinically relevant extension of OS, without additional (hematologic and non-hematologic) toxicity. In contrast, the addition of VPA did not affect ORR or OS. Disclosures Lübbert: Celgene: Other: Travel Funding; Janssen-Cilag: Other: Travel Funding, Research Funding; Ratiopharm: Other: Study drug valproic acid. Schlenk:Pfizer: Honoraria, Research Funding; Amgen: Research Funding. Heuser:Pfizer: Research Funding; Tetralogic: Research Funding; BerGenBio: Research Funding; Karyopharm Therapeutics Inc: Research Funding; Bayer Pharma AG: Research Funding; Celgene: Honoraria; Novartis: Consultancy, Research Funding. Bug:Janssen: Other: Travel Grant; Astellas: Other: Travel Grant; Teva Oncology: Other: Travel Grant; Novartis: Honoraria, Research Funding; Celgene: Honoraria, Other: Travel Grant; Nord Medica: Consultancy. Giagounidis:Celgene Corporation: Consultancy. Brugger:Astrazeneca: Employment. Niederwieser:Amgen: Speakers Bureau; Novartis Oncology Europe: Research Funding, Speakers Bureau.

Abstract: Purpose Mutations of the isocitrate dehydrogenase-1 (IDH1) and IDH2 genes are one of the most frequent alterations in acute myeloid leukemia (AML) and can be found in ~20% of patients at diagnosis. Several IDH inhibitors are currently in late stage clinical development with Enasidenib, an IDH2 inhibitor, being recently approved by the FDA. Previous analyses have reported differential impact on response to chemotherapy and outcome, depending on the IDH-mutation type, co-occurring mutations and cytogenetic abnormalities, as well as the variant allele frequency (VAF) of IDH mutations. In order to better understand its prognostic role, we analyzed newly diagnosed AML patients enrolled in prospective trials of the Study Alliance Leukemia (SAL) to investigate the impact of IDH1/2 mutations on outcome. Patients and Methods All AML patients consecutively enrolled into intensive AML treatment protocols of the SAL or into the SAL registry were included in this analysis. Next-generation sequencing (NGS) on an Illumina MiSeq-system was performed to detect IDH1/2 mutations using pre-treatment samples. Overall survival (OS) and response to therapy were analyzed for all patients with intensive treatment and according to the mutational status. Results Overall, samples of 3898 patients were analyzed. The median follow-up was 91 months (95% CI 87.2 - 93.9). Patients' characteristics are shown in Tbl.1. Three-hundred twenty-nine patients (8.4%) had IDH1 mutations and 423 (11%) had IDH2 mutations; both mutations were found in 12 pts, so the overall mutation rate in IDH1 and 2 was 19% (740/3898 patients). Of the IDH1 variants, the most common ones were the R132C found in 143 patients (43%) and R132H in 137 patients (42%). For IDH2, 324 patients had the R140Q (77%) and 80 patients the R172K (19%) variant. According to the two main variants of the more common IDH2 mutations, as reported before, the IDH2 R172K was mutually exclusive with NPM1 and/or FLT3-ITD mutations. Overall, there was a trend for increased OS for patients with IDH2 R172K (26 vs. 15 months) as compared to those with R140Q. Considering only patients with a normal karyotype and no NPM1/FLT3-ITD mutation, these patients (n=27) had a highly significant better OS than patients with IDH2 R140Q (46.3 vs. 13.1 months, p=.012), supporting the findings published by Papaemmanuil et al. (NEJM 2016). In IDH1-mutated patients, we observed statistically significant differences in baseline characteristics between the two most common mutation types, IDH1 R132C and R132H. Patients carrying the R132C mutation were older (62 vs. 55 years, p=.001), had lower WBC (3.6 vs. 21 Gpt/L, p≤.001) and were less likely to have a normal karyotype (43% vs. 66%, p=.002), NPM1 (23% vs. 66%, p= 〈 .001), and FLT3-ITD mutations (8% vs. 27%, p 〈 .001) than those with the R132H variant. In univariate testing, the CR rate was also statistically significant lower in patients with IDH1 R132C (53% vs. 72%, p≤.001), with a median OS of 12.9 months compared to 17.4 months for patients with R132H variant (p=.08). In multivariate analysis including age, WBC, NPM1 and FLT3 status, and ELN risk, the CR rate was significantly lower in patients with the IDH1 R132C variant (p=.038). The median IDH VAF was 38% (range, 0.1 - 58) with no difference according to the different types of mutation. Patients with a VAF 〉 30% had a significantly higher BM blast count (73% vs 40% for VAF≤5%) and WBC (21.2 Gpt/L vs. 3.7 Gpt/L) at baseline, but there was no clear impact on CR rate or OS found in multivariate analysis. Conclusion In this large cohort of AML patients with IDH1/2 mutations, we found significant and so far not reported differences for one of the two most prominent mutations types of IDH1. The R132C variant was associated with increased age, lower WBC, and lower NPM1 and/or FLT3 co-mutation rate. Further, these patients had lower CR rates and a trend for shorter OS. For IDH2 we were able to reproduce findings on co-mutations and showed a favorable outcome for intensively treated patients with a normal karyotype and no NPM1/FLT3-ITD mutation and the IDH2 R172K variant, providing additional evidence for classification as a separate AML entity. Disclosures Middeke: Roche: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees. Rollig:Bayer: Research Funding; Janssen: Research Funding. Kramer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; Daiichi Sankyo: Consultancy. Scholl:Alexion: Other: Travel support; Abbivie: Other: Travel support; Novartis: Other: Travel support; Deutsche Krebshilfe: Research Funding; Carreras Foundation: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; MDS: Other: Travel support; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees. Hochhaus:Incyte: Research Funding; Pfizer: Research Funding; Takeda: Research Funding; Bristol-Myers Squibb: Research Funding; Novartis: Research Funding. Brümmendorf:Takeda: Consultancy; Pfizer: Consultancy, Research Funding; Janssen: Consultancy; Merck: Consultancy; Novartis: Consultancy, Research Funding. Burchert:Novartis: Research Funding; Pfizer: Honoraria; Bristol Myers Squibb: Honoraria, Research Funding; AOP Orphan: Honoraria, Research Funding; Bayer: Research Funding. Krause:Novartis: Research Funding. Hänel:Amgen: Honoraria; Novartis: Honoraria; Roche: Honoraria; Takeda: Honoraria. Platzbecker:Celgene: Research Funding. Mayer:Johnson & Johnson: Research Funding; Roche: Research Funding; Eisai: Research Funding; Affimed: Research Funding; Novartis: Research Funding. Serve:Bayer: Research Funding. Ehninger:Cellex Gesellschaft fuer Zellgewinnung mbH: Employment, Equity Ownership; Bayer: Research Funding; GEMoaB Monoclonals GmbH: Employment, Equity Ownership. Schetelig:Gilead: Consultancy, Honoraria, Research Funding; Abbvie: Honoraria; Janssen: Consultancy, Honoraria; Roche: Honoraria; Sanofi: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Thiede:AgenDix: Other: Ownership; Novartis: Honoraria, Research Funding. Stoelzel:Neovii: Speakers Bureau.

Abstract: Despite recent advances, treatment of elderly patients with AML remains a challenge because of adverse disease biology, comorbidities and therapy related toxicities. The balance between effectivity and toxicity of treatment strategies play a key role. Since comparative studies are lacking, a prospective randomized trial was designed among German AML study groups with different treatment strategies to compare outcome. Patients ≥60 years with all AML subtypes except M3 were randomized up-front to a common standard arm (CSA) (10%) and to study specific arms (90%) of the AMLCG or the OSHO. The CSA consisted of one or two inductions of araC 100 mg/m2/d continuous IV (CI) d 1-7 d and daunorubicin (dauno) 60 mg/m2/d IV d 3, 4, 5 and two courses of araC 1 g/m2/d BID IV d 1, 3 and 5 as consolidation (Mayer RJ et al, NEJM 1994). The AMLCG study arm randomized TAD (araC 100 mg/m2/d CI d1-2 followed by BID d 3-8, dauno 60 mg/m2/d IV d 3-5 and 6-thioguanine 100 mg/m2/d po BID d 3-9) and HAM [araC 1 mg/m2/d IV BID d 1-3 and mitoxantrone (mito) 10 mg/m2/d IV d 3-5] versus two courses of HAM with any 2nd course only given if blasts persisted ± G-CSF. Two courses of TAD were given as consolidation followed by maintenance chemotherapy over three years. The OSHO study arm included araC 1 g/m²/d BID IV d 1 + 3 + 5 + 7 and mito 10 mg/m2/d IV d 1 - 3 for one or two induction courses and ara-C 500 mg/m² BID 1h IV d 1 + 3 + 5 in combination with mito10 mg/m2/d IV d 1 + 2 as consolidation. Pegfilgrastim 6 mg s.c. was applied on day 10 of induction and on d 8 of consolidation. The study was approved by the IRB and registered at clinicaltrials.gov (NCT01497002 and NCT00266136). Written informed consent was obtained from all patients prior to randomization. Between April 1st, 2005 and May 26th, 2015 1286 patients were assigned randomly to the CSA (n=132) or to the study groups arm (n=1154). After excluding 139 patients (10.8%), 1147 patients were eligible for analysis, 1120 with follow-up for overall survival (OS) and 1079 for complete remission (CR) analysis. Baseline characteristics of all eligible patients showed median ages of 68 (60-82) years for the CSA and 69 (60-87) and 70 (60-85) years in the study arms A and B, respectively (p=0.05). Proportions of patients with secondary AML differed significantly between study arms (A: 42%, B: 30%, CSA: 36%; p=0.003). The CSA had less flt3 wildtype/npm1 wildtype patients (31%) vs. arm A (51% p=0.040) and arm B (58%, p=0.0455). No differences were observed with respect to cytogenetic risk groups, white blood cell counts, LDH, and npm1 mutant/ flt3-wildtype or mutant. The primary endpoint event free survival (EFS) did not differ between the CSA and study group strategies. Three-year EFS was 12.4% (95% CI: 6.7 - 19.9%) in the CSA, 15.6% (95% CI: 13.1 - 18.3%) in group A and 11.4% (95% CI, 7.4% to 16.4%) in group B (n.s.;Fig.1). With a median follow-up of 67 months, OS did not differ significantly between CSA and study group regimens. The 3-year survival probability was 22.3% (95% CI: 14.7-30.9%) in the CSA, 24.7% (95% CI: 21.6-27.9%) in group A and 22.4% (95% CI, 16.7% - 18.3%) in group B (Fig.2). CR status after 90 days of therapy was evaluated as secondary endpoint. The proportion of patients in CR in the CSA [51% (95% CI: 42-61%)] was comparable to the 50% (95% CI: 47-54%) and 48% (95% CI: 41-55%) of the study group arms (p=n.s.). Persistent leukemia was seen in 16% (95% CI: 10-24%) in the CSA vs 17% (95% CI: 14-19%) and 12% (95% CI: 8-17%) in groups A and B, respectively (both p= n.s.). A total of 226 patients died within 90 days of treatment, 24% (95% CI: 17-33%) in CSA, 19% in group A (95% CI: 16-22%) and 27% (95% CI: 21-33%) in group B; CSA vs A p=0.1859, CSA vs B p=0.5902). Death without AML was 3% in CSA, 2% in group A and 3% in group B, death with AML was 9% in CSA, 6% in group A and 5% in group B and death from indeterminate cause was 12% in CSA, 11% in group A and 20% in group B. Three-year relapse free survival (RFS) was 21.3% (95% CI: 12.2 - 31.0) in the CSA, 28.9% (95% CI: 24.9 -33.0%) in group A and 24.0% (95% CI: 16.8 - 31.9) in group B (both p=n.s.; Fig.3). In multivariate analysis independent variables for EFS and OS were age, type of disease, cytogenetic group and WBC count, but not the allocation to one of the treatment arms. Age and cytogenetic group were determinants for RFS. Conclusion A strictly prospective comparison of different treatment strategies in patients with AML did not show clinically relevant outcome differences when compared to a common standard arm. Figure 1. Figure 1. Figure 2. Figure 2. Figure 3. Figure 3. Disclosures Niederwieser: Novartis Oncology Europe: Research Funding, Speakers Bureau; Amgen: Speakers Bureau. Hoffmann:Novartis Oncology Europe: Research Funding. Al-Ali:Celgene: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Hegenbart:Pfizer: Other: Travel grant; Janssen: Honoraria, Other: Travel grant. Sayer:Riemser Pharma: Consultancy. Hochhaus:BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; ARIAD: Honoraria, Research Funding. Fischer:Novartis: Consultancy, Honoraria. Dreger:Novartis: Consultancy; Janssen: Consultancy; Gilead: Consultancy; Gilead: Speakers Bureau; Roche: Consultancy; Novartis: Speakers Bureau. Hiddemann:Roche: Membership on an entity's Board of Directors or advisory committees; Genentech: Other: Grants; Roche: Other: Grants.

Abstract: Chordomas are rare tumors of the axial skeleton and skull base with few therapeutic options and no clinically validated molecular drug targets. The value of comprehensive genomic analyses for guiding medical therapy of patients with advanced-stage chordoma is unknown. We performed whole-exome and genome sequencing of tumor and matched germline control samples from 11 patients with locally advanced or metastatic chordoma within the MASTER program, a prospective clinical sequencing program of the German Cancer Consortium. All patients were pretreated and had progressive disease prior to molecular analysis. Genomic profiling showed that advanced chordomas are frequently characterized by genomic patterns indicative of defective homologous recombination (HR) DNA repair. First, DNA copy number profiles showed high numbers of structural variants greater than 10 million base pairs in size in the majority of cases. Second, all patients harbored somatic aberrations of at least 2 genes known to be involved in HR, and 10/11 cases harbored somatic alterations in 3 or more HR pathway genes. For example, 8 patients showed heterozygous BRCA2 deletions, which were associated with heterozygous deletions of ERCC6 in 6 patients and RAD54L in 7 patients, as well as PTEN alterations (heterozygous deletion, heterozygous mutation and deletion of the wildtype allele or loss of heterozygosity). Other recurrently altered HR genes included ATR, CHEK2, FANCC, FANCD2, FANCG, RAD18, RAD51B, and XRCC3. Third, pathogenic germline alterations were detected in 3 patients. A heterozygous BRCA2 frameshift mutation (p.T3085fs*26; ACMG Class 5), a heterozygous NBN frameshift mutation (p.K219Nfs*16; ACMG Class 5), and a heterozygous CHEK2 missense mutation (p.R145W; ACMG Class 4) were accompanied by somatic deletion of the respective wildtype alleles. Fourth, a mutational signature associated with HR deficiency was significantly enriched in 72.7% of samples and coincided with genomic instability. The high prevalence of an HR deficiency “footprint” in chordoma patients prompted us to explore the clinical efficacy of the poly(ADP-ribose) polymerase(PARP) inhibitor olaparib, which is preferentially toxic to HR-incompetent cells. Olaparib treatment of a patient whose tumor showed a prominent exposure to an HR deficiency-associated mutational signature, a high degree of genomic instability, and 13 heterozygous HR gene alterations halted tumor growth for 10 months. Whole-genome analysis at progression revealed a PARP1 p.T910A mutation predicted to disrupt the autoinhibitory PARP1 helical domain, providing novel insight into the mechanisms of PARP inhibitor resistance. In summary, our study has uncovered a key biological feature of advanced chordoma that represents an immediately actionable therapeutic target and provides a rationale for genomics-guided clinical trials of PARP inhibition in this intractable tumor entity. Citation Format: Stefan Gröschel, Daniel Hübschmann, Francesco Raimondi, Peter Horak, Gregor Warsow, Martina Fröhlich, Barbara Klink, Laura Gieldon, Barbara Hutter, Kortine Kleinhenz, David Bonekamp, Oliver Marschal, Priya Chudasama, Jagoda Mika, Marie Groth, Sebastian Uhrig, Stephen Krämer, Christoph Heining, Christoph Heilig, Daniela Richter, Eva Reisinger, Katrin Pfütze, Roland Eils, Stephan Wolf, Christof von Kalle, Christian Brandts, Claudia Scholl, Wilko Weichert, Stephan Richter, Sebastian Bauer, Roland Penzel, Evelin Schröck, Albrecht Stenzinger, Richard Schlenk, Benedikt Brors, Robert Russell, Hanno Glimm, Matthias Schlesner, Stefan Fröhling. Defective homologous recombination DNA repair as therapeutic target in advanced chordoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2723.