Litzow, Mark R.

Abstract Background: Adult acute myeloid leukemia (AML) patients with high-risk cytogenetics have a significantly worse survival compared to similarly treated intermediate- or favorable-risk patients. Although prior studies suggest better outcome in high-risk AML patients in first complete remission (CR1) who undergo allogeneic hematopoietic cell transplantation (HCT) compared with consolidation chemotherapy, only 40% of patients proceed to HCT. The lack of a matched sibling donor (available in about 33%) should not be a barrier to HCT since alternative donors are available for the large majority of high-risk AMLpatients and recent data suggest outcomes after allogeneic HCT from fully matched unrelated donors are similar to those following matched related donor transplantation. We sought to determine if a prospective organized effort could rapidly identify alternative donors to improve the historical 40% allogeneic HCT rate in high-risk CR1 AML patients ≤ age 61. Secondly, we hypothesized that transplanting significantly more adults with high-risk AML in CR1 would lead to an improved outcome compared with the historical relapse-free survival (RFS) of 22%. Patients and Methods: Adult patients between ages 18 and 60 years with untreated AML were randomized to receive induction therapy with standard cytarabine plus daunorubicin (7+3; n=261), idarubicin with high-dose cytarabine (IA; n=261), or IA with vorinostat (IA+V; n=216). Conventional cytogenetics were obtained at time of enrollment and used to determine risk classification by standard criteria. All patients with high-risk cytogenetics underwent expedited HLA-typing. High-risk patientswere encouraged tobe referred for consultation with a transplant team with the goal of conducting an allogeneic HCT in CR1. Results: Of 738 eligible patients (median age, 49 years; range, 18-60), 159 (22%) had high-risk cytogenetics, of whom 60 (38%), 61 (38%), and 38 (24%) received induction with 7+3, IA, or IA+V, respectively. A total of 107 of the 159 high-risk patients achieved CR/CRi (67%). HCT was performed in 317 of all 738 patients (43%) and 68 (64%) of the high-risk patients received a transplant in CR1 (p<0.001 compared to historical rate of 40%). Twenty-five (37%) had a matched related donor, 31 (45%) had a matched unrelated donor, 3 (4%) had a mismatched related donor, 8 (12%) had a mismatched unrelated donor, and 1 (1%) received an umbilical cord blood transplant. Sixty-six high-risk patients transplanted in CR/CRi have detailed data. Median time to HCT from CR1 was 76 days (range, 20-365). Fifty-seven patients (86%) received a myeloablative regimen and 9 (14%) reduced-intensity conditioning. Reasons for 39 high-risk CR1 patients not receiving a transplant in CR1 were: co-morbidities (n=1), death (n=6), no insurance (n=1), no donor (n=1), physician decision (n=3), patient decision (n=3), relapse (n=6), other (n=10), or unknown (n=8). The 2-year RFS estimate in the entire high-risk cohort is 32%, significantly higher than the 22% historical rate (p=0.05). Median RFS in the high-risk CR1 cohort (n=107) was 10 months [range, 1-32* (censored) months]. RFS and OS were similar among HCT patients using matched related [1 year estimates: 40% (95% CI 27%, 74%) and 56% (37%, 74%), respectively] and matched unrelated [1 year estimates: 52% (37%, 75%) and 56% (37%, 74%), respectively] donors in CR1. The HR (reference = unrelated) for RFS was 0.67 (0.32, 1.37) and for OS was 0.88 (0.41, 1.90). Median overall survival (OS) among all patients in the high-risk cohort (n=159) was 12 months [range, 1-33* (censored) months] and was 18 months [range 3-33* (censored) months] for those transplanted in CR1 (Fig. 1). Conclusions: In newly diagnosed adults with AML age 18-60, early cytogenetic testing with an organized effort to identify a suitable allogeneic HCT donorled to a CR1 transplant rate of 64% in the high-risk group, which in turn led to a significant improvement in RFS over historical controls. Better outcomes in poor prognosis AML patients may be achieved simply by rapidly finding unrelated donors and performing allogeneic HCT in CR1 as soon as possible. Clinical Trials Registry: NCT #0180233; Support: NIH/NCI grants: CA180888, CA180819, CA18020, CA180821, CA180863, CA077202; CCSRI #021039 Figure 1 Overall Survival (OS) among all patients in the high-risk cohort, all high-risk patients achieving CR1, and in those high-risk patients transplanted in CR1. Figure 1. Overall Survival (OS) among all patients in the high-risk cohort, all high-risk patients achieving CR1, and in those high-risk patients transplanted in CR1. Disclosures Othus: Glycomimetics: Consultancy; Celgene: Consultancy. Radich:Novartis: Consultancy, Other: laboratory contract; ARIAD: Consultancy; Pfizer: Consultancy; TwinStrand: Consultancy; Bristol-MyersSquibb: Consultancy. Strickland:Alexion Pharmaceuticals: Consultancy; Ambit: Consultancy; Baxalta: Consultancy; Boehringer Ingelheim: Consultancy, Research Funding; CTI Biopharma: Consultancy; Daiichi Sankyo: Consultancy; Sunesis Pharmaceuticals: Consultancy, Research Funding; Abbvie: Research Funding; Astellas Pharma: Research Funding; Celator: Research Funding; Cyclacel: Research Funding; GlaxoSmithKline: Research Funding; Karyopharm Therapeutica: Research Funding; Sanofi: Research Funding. Savoie:AbbVie: Consultancy; Lundbeck: Consultancy; BMS: Consultancy, Honoraria; Velgene: Consultancy; Pfizer: Consultancy; Amgen: Consultancy; Novartis: Consultancy, Honoraria; Jazz: Consultancy. Sekeres:Millenium/Takeda: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Stone:Amgen: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Xenetic Biosciences: Consultancy; Jansen: Consultancy; Pfizer: Consultancy; ONO: Consultancy; Juno Therapeutics: Consultancy; Merck: Consultancy; Roche: Consultancy; Seattle Genetics: Consultancy; Sunesis Pharmaceuticals: Consultancy; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy; Novartis: Consultancy; Celator: Consultancy; Karyopharm: Consultancy. Erba:Seattle Genetics: Consultancy, Research Funding; Pfizer: Consultancy; Jannsen: Consultancy, Research Funding; Juno: Research Funding; Celator: Research Funding; Ariad: Consultancy; Agios: Research Funding; Amgen: Consultancy, Research Funding; Novartis: Consultancy, Speakers Bureau; Millennium Pharmaceuticals, Inc.: Research Funding; Incyte: Consultancy, DSMB, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Gylcomimetics: Other: DSMB; Sunesis: Consultancy; Daiichi Sankyo: Consultancy; Astellas: Research Funding.

Abstract Background: Adult relapsed/refractory acute lymphoblastic leukemia/lymphoma (rALL) carries a very poor prognosis with limited options for effective salvage therapy. To date, there has been only a single retrospective report on the use of clofarabine in adult rALL demonstrating CR rate of 31% in this setting (Barba P et al. 2012). Aim: To evaluate the efficacy and toxicity of clofarabine based therapy in a relatively large cohort of adult rALL patients. Method: After IRB approval, a retrospective single institution study of all patients (pts) diagnosed with rALL treated with a clofarabine based regimen at Mayo Clinic between 2000 - 2014 was performed. Categorical variables were analyzed using Pearson's chi-squared test while continuous variables were analyzed using the Wilcoxon / Kruskal-Wallis test with P < 0.05 considered statistically significant. Survival estimates were calculated using Kaplan-Meier method and means were compared using log ranks. Results: Presenting features: We identified a total of 22 pts with a diagnosis of rALL who received clofarabine based therapy. 20 patients were evaluable and 2 were excluded (one received clofarabine as salvage for positive MRD and the other as systemic maintenance with CNS directed therapy for an isolated CNS relapse). Among evaluable pts, median age at time of Clofarabine based chemotherapy was 39 years (range 19-65) and 50% were males. Thirteen had B-ALL while 7 had T-ALL. Median leukocyte count was 6 x109 (0.2-28.7), hemoglobin 9.8 g/dL (7-12.9), platelet 65 x109 (12-493), peripheral blood blast 4% (0-88) and bone marrow blasts 80% (0-95) while five pts had extramedullary disease. Median number of prior regimens was 2 (1-7).. 8 (40%) pts were post allogeneic transplant Treatment and Response: 10 pts (50%) received clofarabine monotherapy, 7(35%) clofarabine and cytarabine, and 3 (15%) had clofarabine, etoposide and cyclophosphamide. Overall response rate (CR/CRi + PR) was 35%. Five (25%) achieved CR/CRi, and 2 achieved PR. Among those who achieved CR, 4 out 5 proceeded to further therapy; 2 to allogeneic stem cell transplant and two additional patients received donor lymphocyte infusion (DLI). One pt with PR also proceeded to allogeneic stem cell transplant. In comparative analysis, there were more males 6 (86%) vs 1(14%) in the responding arm (P = 0.014), otherwise the number of regimens prior to clofarabine, type of clofarabine regimen, transplant status, T vs B cell ALL, did not impact response. Median overall survival was 2.4 months (1.3-2.9) in non-responders vs. 12.8 months (3-27.4) in responders (P =0.0007) (Figure 1). All pts who proceeded to transplant or DLI relapsed with a median time to relapse of 6.4 (4.8-13.7) months. Toxicity: Rash/Hand Foot syndrome was observed in 3 pts (19%), Grade III-IV liver toxicity occurred in 4 (26%) with no permanent sequela. Opportunistic infection occurred in 3 pt (17%). Conclusion: Clofarabine based chemotherapy was a well-tolerated salvage regimen in heavily pretreated patients and was an effective bridge to definitive therapy in a significant proportion of cases. Prospective evaluation of these findings is warranted. Figure 1. Figure 1. Disclosures Al-Kali: Celgene: Research Funding.

Abstract Background: MDS is a clonal bone marrow disorder characterized by ineffective hematopoiesis with peripheral blood cytopenias and an increased risk for transformation to acute leukemia. Patients with MDS who have a history of prior exposure to chemotherapy and/or radiotherapy are called therapy-related MDS (t-MDS). We hereby describe our experience with this entity and compare it to our experience with de novo MDS patients. Aim: To study the differences of clinical outcome between t-MDS and de novo MDS patients. Method: A retrospective single institution study chart review of cases with MDS at Mayo Clinic Rochester between 1993- 2011 was performed. De novo MDS, t-MDS and leukemic transformation (LT) were defined according to the World Health Organization (WHO) classification (Swerdlow et al 2008). Prior exposures to chemotherapy, radiotherapy and/ or both were defined as t-MDS; while lack of any as de novo MDS. Appropriate IRB approval was obtained in accordance with the Helsinki declaration. Comparison between group medians was done using Wilcoxon test, comparison between values was done using contingency and One-way analyses (Means/Anova/Pooled t), while survival estimates were calculated using Kaplan-Meier curves JMP V10 Results: Out of 827 patients with MDS, 153 (19%) patients were t-MDS (group (Gr) 1) versus 674 (81%) (rest of patients, Gr 2). Out of the t-MDS, 79 (52%) pts had CTX, and 42 (27%) had XRT, and 32 (21%) pts had both CTX/XRT). Upon comparison between Gr 1 vs 2, statistical significant difference was seen in median age 69 vs 72 (p=0.01), Platelets 68 vs 114 x109(<p0.0001), and WBC 3.2 vs 3.6 x109(0.02), respectively. No significant statistical difference was found in median Hg 9.6 vs 9.7 gm/dL (p 0.6), peripheral blood (PB) blasts 0% in both groups, and bone marrow (BM) blasts 2% in both groups. IPSS was low, int-1, int-2, high in 16%, 40%, 34%, 9%in Gr 1 and 32%, 46%, 18%, 4% in Gr 2. IPSS-R was very low, low, int, high, very high in 9%, 24%, 18%, 20%, 28% in Gr 1 vs 18%, 36%, 20%, 16%, 10% in Gr 2. AML transformation (LT) was identical in both groups at 12%. Upon comparison between Gr 1 and 2, median time to AML transformation was 7.9 vs 13 months (p=0.08). Median overall survival (mOS) was shorter in Gr 1 vs 2 at 16 vs 34 months (P<0.0001). When analysis was limited to diploid cytogenetics, median OS was 63 vs 50 months, respectively (p=0.9). Both IPSS and IPSS-R were prognostic of mOS in t-MDS (p<0.0001). On multivariate analysis; age (<0.0001), IPSS-R (p<0.0001) and previous CTX and/ or XRT (P=0.02) were the only variables that affected mOS. Conclusion: T-MDS comprises a small portion of all MDS cases (19%). Median overall survival in the de novo MDS group was longer than t-MDS group; however this difference was not maintained in patients with diploid cytogenetics. Similarly, time to AML was longer in de novo MDS compared to t-MDS (although similar rates of incidence). All of age, IPSS-R and t-MDS did affect median OS on multivariate analysis. Disclosures Al-Kali: Celgene: Research Funding.

Abstract Background: Momelotinib is a JAK 1/2 inhibitor that is active in the treatment of myelofibrosis (MF); a previous phase 1/2 study included 100 consecutive patients from the Mayo Clinic (Leukemia. 2015;29:741). In the current long-term study of these 100 patients, we provide a cumulative account of short and long term efficacy and toxicity data, as well as survival analysis. Methods: The current study represents sponsor-independent analysis. The study patients are part of a larger (n=166) phase-1/2 momelotinib study (NCT00935987), which was conducted in two dose-escalation (100 mg-400 mg daily doses) and dose-confirmation (300 mg daily dose) phases. Adverse events (AEs) were monitored by Common Terminology Criteria for Adverse Events (Version 4.03) and responses by the International Working Group criteria (Blood. 2013;122:1395). All statistical analyses considered clinical and laboratory parameters obtained at the time of entry to study. Results: Baseline data: 100 patients with MF (median age 66 years; 58% males) were treated between 11/20/09 and 11/10/10; 64 patients had primary MF, 22 post-polycythemia vera MF and 14 post-essential thrombocythemia MF. 73 (73%) patients harbored JAK2 mutations, 16 (16%) CALR, 7 MPL and 4 were "triple-negative"; among the 16 CALR-mutated cases, 13 were classified as "type 1/type 1-like". DIPSS-plus risk distribution (JCO 2011;29:392) was 63% high, 36% intermediate-2 and 1% intermediate-1; 49% displayed red cell transfusion-dependency, 58% constitutional symptoms, 87% palpable splenomegaly >5 cm and 50% abnormal karyotype. 94 patients were screened for ASXL1 mutations with 41 (44%) mutated and 78 for SRSF2 mutations with 14 (18%) mutated. 21 (21%) patients were previously treated with another JAK inhibitor. Current disposition: All information was updated in July 2016. To-date, after a median follow-up of 3.2 years, 88 drug discontinuations, 70 deaths and 14 leukemic transformations have been documented; median follow-up for living patients was 5.7 years (range 5.1-6.4). Among the 30 patients who are currently alive, 12 remain on study and another 5 have received stem cell transplant. Toxicity data: After a median treatment duration of 1.7 years, "momelotinib related" grade 3 or 4 AEs included thrombocytopenia (34%), neutropenia (9%), anemia (5%), increased lipase (7%), increased ALT (4%), increased AST (2%), increased ALP (2%) and headaches (2%). In addition, noteworthy grade 1 or 2 AEs included peripheral neuropathy (PN) 47%, increased lipase (14%), increased amylase (17%), increased bilirubin (13%), increased AST (21%), increased ALT (19%), increased APTT (17%), headaches (13%), dizziness (22%), nausea (23%) and diarrhea (20%). Most of the AEs, except PN, were reversible. Efficacy data and predictors of response and relapse-free survival: Clinical improvement (CI) was documented in 57% of patients, anemia response in 44%, and spleen response in 43%. 51% of transfusion-dependent patients became transfusion independent. The majority of patients also had marked improvement in their symptoms. 46 (81%) of the 57 responding patients discontinued treatment after a median treatment duration of 2.3 years. ASXL1 mutations predicted inferior CI (p=0.03) whereas relapse-free survival was adversely affected by absence of type 1/type 1-like CALR (p=0.03) or presence of unfavorable karyotype (p=0.002); among the 11 responding patients currently still receiving the drug, all had favorable karyotype and 5 had type 1/type 1-like CALR mutations. Survival analysis and risk factors : Median survival, calculated from the time of study entry, was 3.2 years with 5-year survival rate of 32%. In multivariable analysis of genetic markers, absence of type 1/type 1-like CALR (HR 2.9, 95% CI 1.1-7.2) or presence of SRSF2 (2.9, 1.5-5.4) or ASXL1 (1.8, 1.1-3.2) mutations were independently predictive of shortened survival (Figure). Conclusions: Momelotinib therapy in MF provides effective palliation in terms of anemia, splenomegaly and constitutional symptoms. However, less than 20% of treated patients enjoy durable long-term benefit and almost half experience drug-related and mostly irreversible peripheral neuropathy. Long-term survival and durability of response were superior in patients with type 1/type 1-like CALR mutations and inferior in those with ASXL1/SRSF2 mutations or unfavorable karyotype. Figure Figure. Disclosures Al-Kali: Onconova Therapeutics, Inc.: Research Funding; Celgene: Research Funding.

Abstract The UKALLXII/ECOG2993 international study for adults with acute lymphoblastic leukeamia (ALL) included a separate, single-arm study (still open) to evaluate the role of etoposide/TBI conditioned allogeneic bone marrow transplantation (BMT) in patients with Philadelphia chromosome positive (Ph pos) disease. Patients received 2 phases of induction, intensification with high dose methotrexate and BMT using unrelated donor stem cells where a matched sibling was not available. 267 patients with Ph pos ALL were treated from 1993 onwards, in the pre-imatinib era. The study was amended in 2003 to add imatinib 600mg per day following induction and after BMT for 2 years or until relapse. A subsequent amendment at the end of 2005, added imatinib 600mg per day also to phase 2 of induction. 153 patients have now been treated on the imatinib-containing protocol − 89 received imatinib following induction and 64 started imatinib with phase 2 induction. Complete remission (CR) rate at the end of 2 phases of induction was 91% with imatinib started in induction, 81% with imatinib started in consolidation only & 83% in the pre imatinib era. 128 of the 153 patients treated with any imatinib were eligible for BMT. Of the 98 patients with over 6 months follow-up, 57 (58%) actually received BMT. This transplant rate does not differ from the 62% in the pre-imatinib era although the data pertain mostly to those whose imatinib started later during therapy. Overall survival of the imatinib-treated group as a whole is 23% at 3 years, which does not differ from the 26% pre-imatinib rate as shown in the figure. Hence, imatinib started post-induction does not appear to improve survival. Imatinib given with induction may improve the CR rate, but there is insufficient follow up to assess transplant or survival rates. Earlier imatinib may be optimal but overall, our study does not provide evidence yet that imatinib alters the outcome of this disease. Figure Figure Patient characteristics Pre-imatinib (N=267) Post-imatinib (N=153) Gender: Male 150 (56%) 96 (63%) WBC (x 10 ^9/l) (2 unknown): <30 141(53%) 86 (56%) ≥ 30 124 (47%) 67 (44%) Median (range) 26.8 (1.5–438) 21.0 (0.5–491) Age: median (range) 40 (15–60) 42 (16–64) CNS disease (82 unknown) 14 (8%) 4 (3%)

Background: Inotuzumab ozogamicin (InO) is an antibody-drug conjugate composed of anti-CD22 antibody conjugated to the cytotoxic agent calicheamicin, which is approved for relapsed/ refractory (RR) B-cell acute lymphocytic leukemia (ALL), based on efficacy demonstrated in a randomized control trial. We sought to investigate the safety and efficacy of InO in the "real world" setting. Methods: We conducted a retrospective multicenter study in collaboration with 11 U.S. academic institutions, and evaluated the outcome of patients (pts) with RR B-cell ALL, who received InO outside of clinical trials. These pts were evaluated for response to InO, duration of response, overall survival (OS) and toxicity. Demographic and disease characteristics were summarized using descriptive statistics. Survival curves were estimated using the Kaplan-Meier method and compared via log-rank test. Duration of response was estimated among pts who achieve complete remission (CR)/CR with incomplete count recovery (CRi). Results: From June 2016 to May 2019, 84 pts with RR-B cell ALL were identified. Baseline characteristics are summarized in Table 1. The median age of pts at InO initiation was 50 years (yrs) (range, 20-87). Twenty-two (27.5%) pts had t(9;22) (Ph+ve) and 6 (7.5%) pts had t(4;11) (MLL gene) chromosomal abnormalities. Nine (11%) and 20 (25%) pts had CNS disease at diagnosis and at relapse, respectively. Median number of therapies prior to InO was 2 (range, 0-7), 40 (48%) pts had ≥ 3 therapies and 23 (27%) pts had allogeneic stem cell transplantation (allo-HCT) prior to InO. Forty (48%) pts received blinatumomab prior to InO. Fourteen (17%) pts received InO in combination with chemotherapy and/ or tyrosine kinase inhibitor (TKI). Overall response rate (CR/CRi) was 63%; 44% had CR with minimal residual disease (MRD) negativity by flow cytometry. Response rate in Ph+ve B-cell ALL was 73%. Twenty-three (27%) pts were successfully bridged to allo-HCT. Median response duration with InO was 11.5 months (mo); 32.5% had sustained response at 2 yrs (Fig. 1a). Median response duration post InO, censored at allo-HCT was not reached (NR) (51% in remission at 2 yrs) (Fig. 1b). Median OS after InO was 11.6 mo and 32% were alive at 2 yrs (Fig. 1c). Median OS post InO, censored at of allo-HCT was 13.6 mo (Fig. 1d). Median OS after InO in Ph+ve pts was NR (71% alive at 1 yr). Forty-nine percent, 27%, 6% and 5% of pts discontinued InO due to progression, allo-HCT, adverse events and maintenance therapy, respectively. Nineteen (30%) pts had dose interruptions. In terms of toxicities, 14 (17%) and 7 (8%) pts had grade (G)1-2 and G3 transaminases secondary to InO, respectively. One pt each had G2 and G3 pancreatitis, respectively. One (1%) and 2 (2%) pts had G2 and G4 veno-occlusive disease secondary to InO, respectively. Two of these pts were treated with defibrotide. Two (2%) pts died due to InO toxicity. A complete description of adverse events are summarized in Table 1. Conclusion: Our real-world data obtained by multicenter collaboration suggest that InO was well tolerated and had significant efficacy in this heavily treated patient population of RR B-cell ALL. Disclosures Liedtke: Celator: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech/Roche: Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; IQVIA/Jazz: 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; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Prothena: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Caelum: Membership on an entity's Board of Directors or advisory committees; BlueBirdBio: Research Funding; Adaptive: Membership on an entity's Board of Directors or advisory committees; Agios: Research Funding; Amgen/Onyx: Consultancy, Honoraria, Research Funding. Aldoss:Jazz Pharmaceuticals: Honoraria, Other: travel/accommodation/expenses, Speakers Bureau; Agios: Consultancy, Honoraria; AUTO1: Consultancy; Helocyte: Consultancy, Honoraria, Other: travel/accommodation/expenses. Curran:Incyte: Research Funding; Merck: Research Funding; Gilead: Research Funding. Podoltsev:Celgene: Other: Grant funding, Research Funding; Genentech: Research Funding; AI Therapeutics: Research Funding; Agios Pharmaceuticals: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Blueprint Medicines: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Research Funding; Astellas Pharma: Research Funding; Daiichi Sankyo: Research Funding; Sunesis Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Research Funding; Pfizer: Research Funding; Astex Pharmaceuticals: Research Funding; CTI Biopharma: Research Funding; Samus Therapeutics: Research Funding; Arog Pharmaceuticals: Research Funding; Kartos Therapeutics: Research Funding; Alexion: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Yang:AstraZeneca: Research Funding; Agios: Consultancy. Mattison:Pfizer: Membership on an entity's Board of Directors or advisory committees. Advani:Pfizer: Honoraria, Research Funding; Amgen: Research Funding; Macrogenics: Research Funding; Glycomimetics: Consultancy, Research Funding; Kite Pharmaceuticals: Consultancy; Abbvie: Research Funding. Atallah:Takeda: Consultancy, Research Funding; Jazz: Consultancy; Helsinn: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; Jazz: Consultancy; Helsinn: Consultancy.

Introduction: It is known that overexpression of DNA methyltransferases (e.g., DNMT1) is frequent and changes of DNA cytosine methylation (5mC) are a constant feature of cancers. DNA methylation inhibitors, such as 5-aza-2'-deoxycytidine (Dec), have been in clinics for patients with leukemia. It is classically believed that promoter hypomethylation coupled by reexpression of epigenetically-suppressed tumor suppressors is a core mechanism behind Dec-impaired leukemia cell growth. However, the fact that global DNA methylation profiling barely predicts Dec-response suggests a demethylation-independent mechanism of Dec-induced cell death. N6-methyladenine (m6A) has been identified recently as an abundant DNA modification in eukaryotes (Wu, Nature 2016;532:329). Importantly, m6A is extensively present in the human genome, and m6A abundance is associated with tumorigenesis (Xie, Cell 2018;71:306). Furthermore, the DNA m6A is dynamically modulated by the methyltransferases (i.e., METTL3, N6AMT1) and demethylases (i.e., ALKBH1), and changes in m6A predict gene expression (Wu, Nature 2016;532:329). Given a potential crosstalk between m6A and distinct epigenetic mechanisms (Yao, Nat. Commun 2017;8:1122), we hypothesized that the anticancer actions of Dec may partially result from changes in DNA m6A in leukemia cells. Methods: Protein expression of target genes was assessed by Western blotting. The levels of DNA cytosine methylation (5mC) and N6-methyladenine (m6A) were measured by dotblotting or liquid chromatography-mass spectrometry (LC-MS/MS). The cell viability and apoptosis were determined by the Cell Counting Kit 8 (CCK8) assays as well as the Annexin V/Propidium Iodide staining and flow cytometry. The peripheral blood mononuclear cells (PBMCs) of leukemia patients from Mayo Clinic were prepared by Ficoll-Hypaque gradient centrifugation. Results: To test our hypothesis, leukemia cells, Kasumi-1, MV4-11, K562 and KU812, were exposed to 2 µM Dec, a clinical achievable concentration, for 72 hours. As expected, Dec treatment led to a downregulation of DNMT1 and DNMT3a, a reduction of 5mC levels by dotblotting using anti-5mC antibody, a blockage of cell proliferation and a promotion of cell apoptosis. When genomic DNA was subjected to dotblotting using anti-m6A antibody, the results revealed a marked decrease of DNA m6A levels in all Dec-treated cells. Then genomic DNA from K562 and MV4-11 cells was enzymatically digested to 2'-deoxynucleosides. dA was quantified by HPLC-UV, while the amount of m6A was measured by isotope dilution HPLC-ESI-MS/MS using 15N labeled internal standard. The standard curves were generated using pure standards, from which the m6A/A ratio was calculated. In agreement with dotblotting results, Dec treatment significantly decreased DNA m6A abundance in both cell lines. Mechanistically, exposure to Dec led to a consistent increase of demethylase fat mass and obesity-associated protein (FTO), but not METTL3 nor ALKBH1 and ALKBH5. Further, knockdown of FTO increased DNA m6A, which was further confirmed by treatment with FTO inhibitors rhein and meclofenamic acid (MA). These data indicate that FTO may be responsible for Dec-induced m6A changes in leukemia cells. To investigate the clinical implications of DNA m6A, we obtained PBMCs from AML patients (n = 10), who received Dec therapy (20 mg/m2 daily for 5 days every 4 weeks) in Mayo Clinic. These PBMCs were further cultured for 48 hours, frozen and stored in 100% ethanol before DNA extraction. The results from dotblotting using anti-5mC or anti-m6A showed that a trend of decrease in both m6A and 5mC abundance is observed, and the pattern of changes in m6A and 5mC displays a positive correlation. Finally, exposure of leukemia cells to the combination of Dec (2 µM) with FTO inhibitor MA (50 µM) induced more cell apoptosis and greater inhibition on cell proliferation as compared to single agent in vitro, supporting FTO inhibitors as new therapeutic agents in leukemia. Conclusion: Our studies suggest that the FTO-DNA m6A axis may partially mediate the therapeutic outcomes of Dec in leukemia. Our findings provide a new mechanistic paradigm for the anticancer activities of Dec, and define the m6A methylation status in leukemia cells as a new pharmacodynamic marker for their response to Dec-based therapy, pointing to a novel treatment strategy for incorporating m6A modulators to enhance the therapeutic index of Dec. Disclosures Al-Kali: Astex Pharmaceuticals, Inc.: Research Funding.

Introduction Novel high-risk groups have been identified in adult ALL, including secondary (sALL) and Philadelphia-like ALL (Ph-like, based on CRLF2, IgH, ABL2, JAK2 and other tyrosine kinase translocations), and those with minimal residual disease >0.1% (MRD+) after induction therapy. Novel targeted therapies are now routinely incorporated into 1st line regimens, including tyrosine kinase inhibitors (BCR-ABL1-pos), rituximab (CD20+) and blinatumomab (Blina) for MRD+. The impact of these novel high risk groups and therapies after alloHCT is unknown; therefore, we evaluated their impact on overall survival (OS), relapse rate (REL), non-relapse mortality (NRM) and acute and chronic GVHD. Methods We evaluated pts receiving 1st Allo-HCT for ALL at Mayo Clinic (Rochester, Phoenix, and Jacksonville) from 2008-2018 for outcomes of interest, specifically the impact of novel therapies and risk groups. Associations of patient factors with outcomes were examined using univariable (UVA) and multivariable (MVA) Cox proportional hazards regression models, where the cause-specific hazard of the given outcome was modeled to account for the competing risk of death. Results We identified 261 consecutive AlloHCT recipients during the study period. Median age at transplant was 48 years (18-72) and 147 (56.3%) were male. The median comorbidity (HCT-CI) score was 2 (0-8). 213 pts (81.6%) had B-lineage ALL, of which 85 (32.6%) were BCR-ABL-pos, 17 (6.5%) Ph-like (identified by FISH), 16 (6.1%) hypoploidy/near triploidy (Hy/Tri), and 67 (25.7%) pre-B ALL NOS. The remaining 48 (18.4%) had T-ALL. 30 pts (11.5%) had sALL (i.e. prior chemo/radiotherapy for another malignancy). HyperCVAD was the most common 1st line regimen (68.2%). 243 (93.1%) pts achieved Complete Remission (CR1) after induction therapy, and 203 (77.8%) were in CR1 at the time of alloHCT. Blina was administered for MRD+ in 14 pts (5.4%), and for relapsed/refractory ALL (R/R) in 13 (27% of R/R pts), 7 of whom received Blina as initial therapy for R/R. Donors were matched unrelated in 149 (57.1%), matched related in 98 (37.5%), and haploidentical in 14 (5.4%). Peripheral blood (PB) grafts were used in 233 (89.3%). 103 (54.5%) were donor:recipient (D:R) sex-matched, and 86 D:R mismatched [47 (24.9%) M:F; and 39 (20.6%) F:M]. Myeloablative conditioning was used for the majority (78.5%) mostly with Cy/TBI (60.5%). Standard GVHD prophylaxis regimens were used. Outcomes Median follow-up after transplant was 22.4 months (0.5-135), and 51 (19.5%) had REL. The 1, 2 and 5-year survival rates were 71.9%, 64.9%, and 54.1%, respectively (Figure 1). Acute GVHD developed in 144 (55.2%) and chronic GVHD in 100 (38.3%). Ph-like ALL, Blina for MRD+, Blina for R/R, sALL and CD20-pos had no independent impact on OS. In contrast, age>60, Hy/Tri, and >CR1 at alloHCT were associated with worse OS in UVA, however, in MVA only pre-B ALL NOS was associated with better OS. Female:male D:R status was associated with inferior OS. Blina for R/R disease was associated with increased risk of REL in UVA [HR 5.26 95% CI (1.33, 20.00), p=0.017], whereas other novel high risk groups had no impact on REL. In contrast, T-ALL, Hy/Tri and >CR1 at AlloHCT were associated with increased REL in UVA, but only T-ALL and Hy/Tri continued to predict for increased REL in MVA. Secondary ALL was associated with increased NRM in UVA [HR 1.96 95% CI (1.07, 3.57), p=0.028], whereas other novel high risk groups had no impact on NRM. In contrast, age>60, >CR1 at AlloHCT and D:R sex mismatch were associated with higher NRM in UVA, but only sex mismatch and >CR1 at AlloHCT were associated with higher NRM in MVA. TBI use was associated with higher risk of acute GvHD (p=0.008) and ATG use with lower risk chronic GVHD (p<0.001). Similarly non-PB grafts were associated with a lower risk of chronic GVHD (p=0.005). Results for OS, REL, NRM, acute and chronic GVHD analysis are shown in Table 1. Conclusion Novel high risk groups (CD20+, Ph-like and sALL) do not appear to adversely impact OS after alloHCT, although sALL was associated with increased risk of NRM. Interestingly, pre-B-ALL NOS appear to be associated with favorable OS. Novel targeted therapies also do not independently predict outcome, with the exception of Blina for R/R ALL which may be associated with REL after subsequent alloHCT (a subgroup for whom novel maintenance strategies should be explored). Our analysis highlights the importance of allo-HCT for novel high risk ALL subgroups. Disclosures Patnaik: Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees. Kharfan-Dabaja:Daiichi Sankyo: Consultancy; Pharmacyclics: Consultancy. Foran:Agios: Honoraria, Research Funding.

BACKGROUND Pulmonary infiltrates are common after allogeneic hematopoietic cell transplantation (HCT) and can have infectious or non-infectious etiologies. Fiberoptic Bronchoscopy (FOB) with bronchoalveolar lavage (BAL) is frequently used to evaluate these patients. However, the diagnostic yield can be highly variable according to patient populations, and the impact on management is not well defined, especially in the era of modern antimicrobial therapies. The aim of this study was to investigate the diagnostic and therapeutic yield of FOB-BAL in adult patients with pulmonary infiltrates during the first 100 days following HCT. METHODS We retrospectively reviewed the medical records of adult HCT patients who underwent FOB-BAL during the first 100 days post HCT between January 2005 and December 2015 at Mayo Clinic, Rochester, MN. The interval from HCT to FOB was stratified into early (days 1-30) vs. late (days 31-100). The finding of progressively more hemorrhagic effluent and/or ≥ 20% hemosiderin-laden macrophages in BAL were considered diagnostic for diffuse alveolar hemorrhage (DAH). Univariate and multivariate logistic regression models were fit to identify clinical and transplant characteristics that may impact the diagnostic yield of FOB-BAL. RESULTS A total of 114 patients (median age 55 years), representing 12% of all HCT patients underwent FOB-BAL. Underlying diagnoses were AML in 36%, MDS in 16%, ALL in 16%, MPN in 12% , CLL in 7%, and other in 13%. Transplants were from matched related donor in 43%, matched unrelated donor in 40%, and other donor/matching status in 17%. FOB-BAL was performed during the early period in 61% and during the late period in 39% of patients. In the early period, FOB-BAL provided a specific diagnosis in 49% of patients (30% DAH and 19% infection). In the late period, FOB-BAL had a diagnostic yield of 55% (14% DAH and 36% infection) (Figure 1). The distribution of bacterial and viral infections identified via BAL were similar during the early period (39% and 38%, respectively), whereas more bacterial than viral infections were identified in the later period (56% vs. 19%, respectively) (Figure 2). Non-invasive testing for respiratory tract infection was performed in 34% of patients. These included nasopharyngeal swab for RSV/Influenza PCR in 16% (all negative), multiplex respiratory pathogen PCR in 5% (1 positive for coronavirus), and sputum culture in 21% (positive in 8 patients). This compares with the identification of an infectious pathogen via BAL in 36% of patients; bacterial in 16%, viral in 11%, and fungal in 10%. Transbronchoscopic lung biopsy biopsies were performed in 8 patients and provided diagnostic information in 3 patients (eosinophilic pneumonia, organizing pneumonia and diffuse alveolar damage each in 1 patient). Procedural complications occurred in 3 patients; 2 after transbronchoscopic lung biopsy (1 bleeding and 1 pneumothorax) and 1 during FOB-BAL (atrial fibrillation with rapid ventricular rate). In a multivariable logistic regression model, the underlying diagnosis, presence of acute respiratory failure, and early vs. later time period after HCT were independently affecting the diagnostic yield of FOB-BAL, with higher likelihood of DAH being diagnosed in patients with AML/MDS and during the early post-HCT period, and higher likelihood of DAH being diagnosed in patients with acute respiratory failure (Table 1). In 40% of patients, FOB-BAL findings lead to treatment changes. These included addition of antimicrobials in 24% and addition of corticosteroids in 22% (17% DAH, 2% idiopathic pneumonia syndrome, and 1% organizing pneumonia) (Figure 3). FOB findings lead to more antimicrobial modifications in the early than in the later period (32% vs. 18%, respectively). Overall survival was poor in all the three groups, although significantly better in patients with non-diagnostic FOB findings (median of 2, 3, and 11 months in patients with DAH, infection, or non-diagnostic FOB finings, respectively) (p = 0.03) (Figure 4). CONCLUSION FOB-BAL provides clinically useful information in the post-transplant period. BAL findings were diagnostic in 51% of patients, and led to management changes in 40% of patients. Transbronchoscopic lung biopsy is associated with higher rates of procedural complications. Further characterization of the underlying diagnosis in patients with non-diagnostic FOB-BAL findings remains an unmet clinical goal. Disclosures Sakemura: Humanigen: Patents & Royalties. Kenderian:Morphosys: Research Funding; Kite/Gilead: Research Funding; Lentigen: Research Funding; Humanigen: Other: Scientific advisory board , Patents & Royalties, Research Funding; Tolero: Research Funding; Novartis: Patents & Royalties, Research Funding. Patnaik:Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees.

Patients who develop therapy-related myelodysplastic syndromes (t-MDSs) or acute myeloid leukemia (t-AML) following prior chemotherapy or an autologous hematopoietic cell transplant (HCT), have a poor prognosis. An earlier analysis of allogeneic HCT (n=868, 1990-2004) showed 5-year overall survival (OS) and disease free survival (DFS) were 22% and 21% (reference). Furthermore, older age, graft source other than a HLA-matched sibling or HLA well matched unrelated donor (URD), t-AML not in remission or advanced t-MDS, and poor risk cytogenetics were associated with worse outcomes. Modern supportive care and conditioning regimens including reduced intensity (RIC) regimens may have improved outcomes. Therefore we analyzed 1531 HCT for t-AML (n = 772) or t-MDS (n = 759) performed from 2000 to 2014. The median age at transplant was 52 (18-77) for t-AML and 59 (18-74) for t-MDS. Eleven percent of patient with t-AML and 24% of patient with t-MDS had a prior autologous transplant. A myeloablative regimen was used for conditioning in 61% of patients with t-AML and 49% of patients with t-MDS (Table 1). For t-AML, the 5-year non-relapse mortality (NRM) and relapse rates (RR) were 33% (95% confidence interval [CI], 30-36) and 43% (40-47), respectively. For t-MDS, the 5 year TRM and RR were 32% (29-36) and 46% (43-50), respectively. Five year DFS and OS were 24% (21-27) and 25% (22-28), respectively, for patients with t-AML. Five year DFS and OS were 21% (18-24) and 27% (23-31), respectively, for patients with t-MDS. In multivariate analysis, t-AML OS and DFS was worse for: previous autologous transplant, relapsed disease at HCT, intermediate or adverse cytogenetics, partially matched and cord blood grafts, and RIC. For t-MDS: age greater than 60, previous autologous transplant, very high IPSS score, and use of HLA-partially matched unrelated grafts. A significant minority of patients with t-AML and t-MDS can achieve long-term remission with allogeneic HCT, yet risks of both NRM and relapse are still excessive. Relapse is the major cause of treatment failure. Disclosures Metheny: Takeda: Speakers Bureau; Incyte: Speakers Bureau. Weisdorf:Incyte: Research Funding; Fate Therapeutics: Consultancy; Pharmacyclics: Consultancy. Kebriaei:Jazz: Consultancy; Amgen: Research Funding; Pfizer: Honoraria; Kite: Honoraria.