Search

Dysregulated cellular differentiation is a hallmark of acute leukemogenesis. Phosphatases are widely suppressed in cancers but have not been traditionally associated with differentiation. In this study, we found that the silencing of protein phosphatase 2A (PP2A) directly blocks differentiation in acute myeloid leukemia (AML). Gene expression and mass cytometric profiling revealed that PP2A activation modulates cell cycle and transcriptional regulators that program terminal myeloid differentiation. Using a novel pharmacological agent, OSU-2S, in parallel with genetic approaches, we discovered that PP2A enforced c-Myc and p21 dependent terminal differentiation, proliferation arrest, and apoptosis in AML. Finally, we demonstrated that PP2A activation decreased leukemia-initiating stem cells, increased leukemic blast maturation, and improved overall survival in murine Tet2−/−Flt3ITD/WT and human cell-line derived xenograft AML models in vivo. Our findings identify the PP2A/c-Myc/p21 axis as a critical regulator of the differentiation/proliferation switch in AML that can be therapeutically targeted in malignancies with dysregulated maturation fate.

Background: Allogeneic stem cell transplantation (allo-SCT) has become an increasingly important consolidation treatment option for patients with acute myeloid leukemia (AML) and as upfront therapy for patients with high-risk myelodysplastic syndrome (MDS). Although the median age at diagnosis for both diseases is above 65 years, studies evaluating allo-SCT as treatment option for patients aged 65 years or older are limited. Further, as the population ages, the number of patients above 65 years considered for allo-SCT will continue to rise. Thus, the aim of our current investigation was to analyze outcomes based on age in AML/MDS patients Methods: A retrospective analysis was performed for all AML/MDS patients who received allo-SCT between January 1984 and December 2018 at our institution. Primary endpoints included progression free survival (PFS) and overall survival (OS). PFS was counted from the day of transplantation to relapse or death. OS was defined as survival from the day of allo-SCT until death from any cause, with censoring of patients known to be alive at the time of last follow-up. PFS and OS were calculated using Kaplan Meier Curves. Secondary endpoints included cumulative incidences of grade II-IV and III-IV acute GVHD (aGVHD), chronic GVHD (cGVHD), relapse, and non-relapse mortality (NRM). Cumulative incidence rates of aGVHD, cGVHD, relapse, NRM were estimated and compared using Gray's test accounting for competing risks. Results: The cohort consisted of 900 AML/MDS patients, with 150 patients ≥65 years and 750 patients The median time from diagnosis to transplantation was 176 days (range: 55-4920) for age Conclusion: Overall, our study suggests similar outcomes for elderly patients undergoing allo-HCT as compared to their counterparts, which is in line with prior studies. This likely is due to advancements in the transplant field, including the development of RIC and alternative donors, which have allowed greater access to transplant for older adults. Utilization of allo-HCT is feasible and should be considered for AML/MDS patients ≥65 years. Further research is underway to evaluate the important determinants of health status in older patients undergoing allo-HCT and to ultimately help predict NRM (BMT CTN 1704). Figure 1 Figure 1. Disclosures Bumma: Amgen, Sanofi: Speakers Bureau; Janssen, Oncopeptides, Sanofi: Consultancy. Vasu: Seattle Genetics: Other: travel support; Boehringer Ingelheim: Other: Travel support; Kiadis, Inc.: Research Funding; Omeros, Inc.: Membership on an entity's Board of Directors or advisory committees. Jaglowski: Takeda: Consultancy; Juno: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding; CRISPR Therapeutics: Consultancy; Novartis: Consultancy, Research Funding. Mims: Syndax Pharmaceuticals: Consultancy; BMS: Consultancy; Jazz Pharmaceuticals: Consultancy; Abbvie: Consultancy; Genentech: Consultancy; Kura Oncology: Consultancy; Leukemia and Lymphoma Society: Consultancy; Glycomemetics: Research Funding; Aptevo: Research Funding; Xencor: Research Funding; Daiichi-Saynko: Consultancy. Brammer: Celgene: Research Funding; Seattle Genetics: Speakers Bureau; Kymera Therapeutics: Consultancy. Saad: Incyte Pharmaceuticals: Consultancy; careDx: Consultancy; Amgen: Research Funding; Kadmon: Research Funding; OrcaBio: Research Funding; Magenta Therapeutics: Consultancy. de Lima: Miltenyi Biotec: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees.

Background: Allogeneic transplantation (allo-HCT) is a potentially curative treatment for a variety of hematologic malignancies and nonmalignant hematologic disorders. Allo-HCT from a haploidentical (Haplo) related donor has emerged as a suitable alternative in the absence of matched related donor (MRD) and matched unrelated donor (MUD). Haplo HCT patients however have higher risk of graft rejection and graft versus-host disease (GVHD). Thus, patients often receive post-transplant cyclophosphamide (PTCy), which has proven to be highly effective in reducing GVHD. While the use of peripheral blood is an attractive option due to the ease of collection and rapid peripheral blood count recovery, not much information is available on the impact of graft sources using PTCy in Haplo-HCT. This study compares outcomes of bone marrow (BM) versus peripheral blood (PB) stem cell graft for Haplo-HCT in adult patients. Methods: We performed a retrospective study of 81 adult patients who underwent Haplo-HCT at The Ohio State University from 2009 to 2018. The study endpoints were overall survival (OS), progression free survival (PFS), non-relapse mortality (NRM), relapse, engraftment, acute GVHD (grade II-IV), and chronic GVHD. All endpoints were measured from the time of transplantation. Patient, disease, and transplant-related characteristics were compared between the two groups (BM versus PB) using the Mann-Whitney U test for continuous variables, and chi-squared or Fisher's exact test for categorical variables. The probabilities of OS and PFS were calculated using the Kaplan-Meier (KM) method and compared using log-rank test. Cumulative incidence rates were estimated and compared using Gray's test accounting for competing risks. Results: We compared the outcomes of patients who received a BM graft (N=43) with those receiving a PB graft (N=38). The median age at transplant was 57 years (20-74). All patients received PTCy in addition to tacrolimus and mycophenolate in 91% of patients. Reduced intensity conditioning (RIC) was used in majority of patients (N=63, 78%). The two groups were comparable including age (median, 60 years for BM and 56 years for PB, p=0.60) and the type of conditioning regimen (79% RIC for BM, 76% RIC for PB, p=0.77). The number of CD34+ and CD3+ infused cells was higher in PB grafts (median, 8.6x106 CD34+ cells/Kg, 2.0 x108 CD3+ cells/Kg, respectively) than for BM (median, 3.7x106 CD34+cells/Kg, 0.4x108 CD3+cells/Kg, respectively). Time to neutrophil and platelet engraftment were significantly shorter in patients receiving PB versus those getting BM grafts: median 15 vs. 17.5 days, (p=0.02) and median 20 vs. 29 days (p Conclusion: Our study suggests peripheral blood for haploidentical transplant to be a good alternative to bone marrow. Similar PFS, OS and NRM were seen between the two graft sources. As expected, faster neutrophil and platelets engraftment were seen with PB due to more CD3+ and CD34+ infused, but without an increase in acute or chronic GVHD. A reduced relapse risk was observed with PB graft. Our study is small and is retrospective, but provide encouraging results. A prospective randomized controlled trial is required to confirm these results. Disclosures Chaudhry: Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bumma:Sanofi: Speakers Bureau; Amgen: Speakers Bureau. Khan:Amgen: Consultancy; Janssen: Consultancy. Devarakonda:Janssen: Consultancy. Vasu:Kiadis Inc: Other: Kiadis has obtained exclusive licensing requirements from The OHio State University; Janssen: Membership on an entity's Board of Directors or advisory committees; Omeros: Membership on an entity's Board of Directors or advisory committees. Jaglowski:Novartis: Consultancy, Research Funding; Juno: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding; CRISPR: Consultancy. William:Seattle Genetics: Research Funding; Merck: Research Funding; Dova: Research Funding; Kyowa Kirin: Consultancy, Honoraria; Guidepoint Global: Consultancy; Incyte: Research Funding; Celgene: Consultancy, Honoraria. Mims:Jazz Pharmaceuticals: Other: Data Safety Monitoring Board; Abbvie: Membership on an entity's Board of Directors or advisory committees; Syndax Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Leukemia and Lymphoma Society: Other: Senior Medical Director for Beat AML Study; Agios: Consultancy; Novartis: Speakers Bureau. Brammer:Bristol-Myers Squibb: Research Funding; Celgene: Research Funding; Seattle Genetics: Honoraria, Speakers Bureau; Kymera: Honoraria; Verastem Oncology: Other: Travel. Saad:Amgen: Other: research support; Magenta Therapeutics: Other: Personal Fees; Incyte Pharmaceuticals: Other: Personal Fees; Orcabio: Other: research support; Kadmon: Other: research support. Efebera:Celgene: Research Funding; Ohio State University: Current Employment; Takeda: Honoraria, Speakers Bureau; Pharmacyclics: Research Funding.

B ackground Premature death from opioid-related causes imposes an enormous public health burden across the United States. Between 2001 and 2016, the number of opioid-related deaths in the United States increased by 345%, from 9489 to 42 245 deaths (33.3 to 130.7 deaths per million population. Moreover, opioids may have immunosuppressive properties independent of their psychotropic effects; opioid use has been associated with increased invasive pneumococcal disease in a nested case-control study of 1233 Medicaid patients from Tennessee. In liver transplant recipients, opioid use disorder has been associated with increased mortality after transplant. The impact of opioid use disorder on patients receiving blood and marrow transplant (BMT) remains to be defined. Methods We performed a retrospective analysis of all consecutive adult patients who had BMT (autologous and allogeneic) from 1/1/2008 through 1/1/2018 at the James Comprehensive Cancer Center. Overall survival (OS) was measured from the date of transplant to the date of death, censoring at date of last follow up if alive. Progression free survival (PFS) was measured from the date of transplant to the date of disease progression or the date of death, whichever occurred first, censoring at last follow up if no event. OS and PFS were estimated by the Kaplan-Meier method and compared using the log-rank test. Opioid use (OU) was defined as a binary yes/no variable if an opioid was prescribed upon discharge from the hospital after BMT. The impact of OU, along with other patient, disease, and BMT related factors, on PFS/OS, was analyzed using Cox regression method. Results A total of 1585 patients were included in the analysis (Table 1). The median age at BMT was 58 (range=18-79) years; 59% were males; 60% had autologous transplants; and 58% were prescribed opioids upon discharge from the hospital. OU was significantly more in patients who were younger, have had allogeneic transplant, reduced intensity conditioning, had acute myeloid leukemia (AML), or higher BMT comorbidity index (CMI). On univariable analysis, OU was not associated with cumulative incidence of relapse (CIR) or PFS however it was associated with inferior OS; hazard ratio (HR)=1.25, 95% CI: 1.06-1.49; p=0.01 (Figure-1). There were no differences in CIR, PFS, or OS when autologous and allogeneic transplants were analyzed separately. Upon multivariable analysis of OS, OU lost statistical significance after controlling for age, diagnosis, type of transplant, intensity of conditioning regimen, CMI, and disease risk index (DRE). Of interest, OU independently predicted for superior OS at 100 days and 365 days post-BMT; HR=0.29, 95% CI 0.16-0.50 (p= Conclusion: Our results suggest that opioid use (OU) may have a long term negative impact on survival in BMT patients. The apparently protective effects of OU early on after BMT is elusive but may be possibly related immunomodulatory effects of opioids. A major limitation of our study is that OU is analyzed at a single time point at hospital discharge after BMT. We plan to undertake a more detailed analysis of ongoing OU after discharge and its impact on survival outcomes after BMT. Disclosures Brammer: Celgene Corporation: Research Funding; Seattle Genetics, Inc.: Speakers Bureau. Efebera:Celgene: Research Funding; Ohio State University: Current Employment; Pharmacyclics: Research Funding; Takeda: Honoraria, Speakers Bureau. Mims:Abbvie: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Other: Data Safety Monitoring Board; Syndax Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Leukemia and Lymphoma Society: Other: Senior Medical Director for Beat AML Study; Agios: Consultancy; Novartis: Speakers Bureau. Chaudhry:Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bumma:Sanofi: Speakers Bureau; Amgen: Speakers Bureau. Khan:Amgen: Consultancy; Janssen: Consultancy. Devarakonda:Janssen: Consultancy. Jaglowski:Novartis: Consultancy, Research Funding; CRISPR: Consultancy; Juno: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding. William:Kyowa Kirin: Consultancy, Honoraria; Merck: Research Funding; Seattle Genetics: Research Funding; Incyte: Research Funding; Guidepoint Global: Consultancy; Dova: Research Funding; Celgene: Consultancy, Honoraria.

Introduction: Allogeneic hematopoietic stem cell transplant (allo-HCT) is a potential curative therapy for a variety of both malignant and nonmalignant hematologic disorders. However, allo-HCT is costly and requires highly specialized, technologically advanced care that is only available in select healthcare centers across the country. Due to its cost and limited availability, minority populations are at risk for healthcare disparities in access to and outcomes of allo-HCT. Prior studies have focused on the impact of health disparities, including race, and geographic residence at time of transplant, on allo-HCT outcomes with variable results. The aim of this study was to evaluate the impact of race and location of residence on outcomes of allo-HCT at one major referral institution. Methods: We performed a retrospective cohort study of patients that underwent allo-HCT at the Ohio State University from 1984 to 2018. The impact of demographic factors including race and place of primary residence were assessed. Patients were divided into race defined as Caucasian, African American (AA), and other. They were also grouped by zip code into rural, suburban, and urban groups. Rural was defined as less than 1000 people per square mile, suburban between 1000-3000 people per square mile, and urban greater than 3000 people per square mile. 2018 population estimates were used. Patients were then stratified into 7 groups based on year (yr) of transplant for analysis. Group (gp) 1 included 1984-1988, gp 2 1989-1993, gp 3 1994-1998, gp 4 1999-2003, gp 5 2004-2008, gp 6 2009-2013, and gp 7 2014-2018. Primary endpoints were progression free survival (PFS) and overall survival (OS). PFS and OS were calculated using Kaplan Meier Curves and compared using log-rank test between race and residence groups. Results: A total of 1,943 patients were included in the study. Of these patients, median age at time of transplant was 50 years old (range 18-76), and 59.6% were male. AML/MDS patients made up the majority of the cohort at 46.3%, with the other most common diagnoses being non-Hodgkin's lymphoma (14.2%), acute lymphocytic leukemia (11.8%), and chronic myeloid leukemia (10.1%). Most patients (94.3%) identified as Caucasian, while 4.6% identified as AA, and 1.1% other. The majority of patients lived in a rural area at the time of transplant with 63.4% rural, 22.9% suburban, and 13.8% urban. There was no significant difference in OS or PFS between Caucasian and AA patients (Figure 1A and B; p=0.15, 0.21). Median OS for AA was 1.9 yrs [95% confidence interval (CI): 0.8-3.6] as compared to 2.3 yrs (95% CI: 1.9-2.9) for Caucasians, with 5 -yr OS of 33 vs. 42% and 10-yr OS of 21 vs. 36% for AA and Caucasian, respectively. Median PFS was 0.9 (95% CI: 0.5-2.7) and 1.3 yrs (95% CI 1.1-1.6), with 5 -yr PFS of 30 vs. 37% and 10-yr PFS of 21 vs. 32% for AA and Caucasian, respectively. There also was no significant difference in OS or PFS between rural, urban, and suburban patients (Figure 2A and 2B; p=0.39, 0.17), with median OS in the three groups 2.2 (95%CI: 1.7-2.9), 2.9 (95%CI: 1.6-4.5), and 2.2 (95% CI: 1.6-3.6) yrs, and 5-yr OS of 40 vs. 43 vs. 43% and 10-yr OS of 33 vs. 39 vs. 39%, respectively. Median PFS were 2.2 (95%CI: 1.7-2.9), 2.9 (95%CI: 1.6-4.5), and 2.2 yrs [95% CI: 1.6-3.6], with 5-yr PFS of 36 vs. 40 vs. 38% and 10-yr PFS of 30 vs. 37 vs. 35%, respectively. Conclusion: Our study suggests that once patients undergo allo-HCT, there is no significant difference in outcomes between patients based on race or residence. This finding suggests that while these underserved populations may initially have less access to specialized care for HCT, if they ultimately undergo allo-HCT, outcomes are similar to their counterparts. Our study did show a significantly lower rates of allo-HCT performed in non-Caucasian races (94% Caucasians vs 4.6% AA and 1% other), which may reflect disparities in access to care in these groups as well as a lack of donors. Further research is needed to assess the barriers for these underserved patients to undergo transplant and to help ameliorate these barriers. Disclosures Chaudhry: Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bumma:Amgen: Speakers Bureau; Sanofi: Speakers Bureau. Khan:Amgen: Consultancy; Janssen: Consultancy. Devarakonda:Janssen: Consultancy. Vasu:Janssen: Membership on an entity's Board of Directors or advisory committees; Omeros: Membership on an entity's Board of Directors or advisory committees; Kiadis Inc: Other: Kiadis has obtained exclusive licensing requirements from The OHio State University. Jaglowski:Kite, a Gilead Company: Consultancy, Research Funding; Juno: Consultancy; Novartis: Consultancy, Research Funding; CRISPR: Consultancy. William:Merck: Research Funding; Celgene: Consultancy, Honoraria; Dova: Research Funding; Seattle Genetics: Research Funding; Incyte: Research Funding; Guidepoint Global: Consultancy; Kyowa Kirin: Consultancy, Honoraria. Mims:Syndax Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Leukemia and Lymphoma Society: Other: Senior Medical Director for Beat AML Study; Agios: Consultancy; Novartis: Speakers Bureau; Jazz Pharmaceuticals: Other: Data Safety Monitoring Board. Brammer:Seattle Genetics, Inc.: Speakers Bureau; Celgene Corporation: Research Funding. Efebera:Celgene: Research Funding; Pharmacyclics: Research Funding; Takeda: Honoraria, Speakers Bureau; Ohio State University: Current Employment.

Introduction: Allogeneic hematopoietic stem cell transplantation (allo-SCT) is a potentially curative treatment for many hematological malignancies and disorders. However, this potential is often impeded by several factors including relapse of the underlying disease, graft-vs-host disease (GVHD) and infectious complications. Specifically, acute GVHD continues to be a major factor in the morbidity and mortality of patients. Hence, the practice of allo-SCT is continuously evolving to mitigate these factors. In particular, advances in the conditioning regimens, GVHD prophylaxis, infectious disease monitoring and prophylaxis and supportive care not only have resulted in improved outcomes, but also have expanded potential indications for allo-HSCT. Therefore, we conducted a retrospective analysis on patients who underwent allo-SCT at The Ohio State University from 1986-2018 to better understand how survival has changed longitudinally in accordance with these therapeutic advancements. Method: We analyzed data from 1943 consecutive patients who received an allo-SCT. Patients were divided into seven groups based on the year of transplant: groups (gp) 1: 1984-1988, 2: 1989-1993, 3: 1994-1998, 4: 1999-2003, 5: 2004-2008, 6: 2009-2013, and 7: 2014-2018. The primary endpoints were overall survival (OS) and progression free survival (PFS), and log-rank test was used to compare across transplant years. The Kaplan-Meier method was used to estimate OS and PFS. The secondary endpoints were the cumulative incidences of grade II-IV and grade III-IV acute GVHD (aGVHD), chronic GVHD (cGVHD), and non-relapse mortality (NRM). Cumulative incidence rates were estimated and compared using Gray's test accounting for competing risks. Results: Across the years (1984-2018), the median age was 50.0 (range: 18-76) with 59.6% of the patients being male. Acute myeloid leukemia accounted for 36.3% of transplants, followed by non-Hodgkin lymphoma (14.2%), acute lymphoid leukemia (11.8%), chronic myeloid leukemia (10.1%), and myelodysplastic syndrome (10.0%). Fifty-five percent of patients received myeloablative conditioning. Across the groups, statistically significant improvements in PFS and OS were observed (p Conclusion: Our data shows improved overall and progression-free survival post allo-SCT over decades, which may be attributed to advances in supportive care, and GVHD and relapse mitigation therapy. The decline in NRM is also likely due to improved supportive measures such as infectious disease monitoring and prophylaxis. Nonetheless, post-transplant relapse and grade III-IV aGVHD remain prominent challenges. Therefore, future research should continue to investigate therapeutic strategies that can both reduce high grade GVHD while limiting post-transplant relapse. Disclosures Chaudhry: Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bumma:Amgen: Speakers Bureau; Sanofi: Speakers Bureau. Khan:Amgen: Consultancy; Janssen: Consultancy. Devarakonda:Janssen: Consultancy. Vasu:Kiadis Inc: Other: Kiadis has obtained exclusive licensing requirements from The OHio State University; Janssen: Membership on an entity's Board of Directors or advisory committees; Omeros: Membership on an entity's Board of Directors or advisory committees. Jaglowski:CRISPR: Consultancy; Novartis: Consultancy, Research Funding; Juno: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding. William:Incyte: Research Funding; Guidepoint Global: Consultancy; Dova: Research Funding; Merck: Research Funding; Seattle Genetics: Research Funding; Kyowa Kirin: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Mims:Leukemia and Lymphoma Society: Other: Senior Medical Director for Beat AML Study; Agios: Consultancy; Abbvie: Membership on an entity's Board of Directors or advisory committees; Syndax Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Other: Data Safety Monitoring Board; Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Novartis: Speakers Bureau. Brammer:Bristol-Myers Squibb: Research Funding; Celgene: Research Funding; Seattle Genetics: Honoraria, Speakers Bureau; Kymera: Honoraria; Verastem Oncology: Other: Travel. Saad:Incyte Pharmaceuticals: Other: Personal Fees; Amgen: Other: research support; Kadmon: Other: research support; Orcabio: Other: research support; Magenta Therapeutics: Other: Personal Fees. Efebera:Celgene: Research Funding; Takeda: Honoraria, Speakers Bureau; Pharmacyclics: Research Funding; Ohio State University: Current Employment.

Introduction: Allogeneic stem cell transplant (allo-SCT) plays a key role in the post-remission therapy for acute myeloid leukemia (AML) patients due to its high rates of efficacy as compared to alternate therapies. For patients with relapsed/refractory AML and those with high-risk myelodysplastic syndrome (MDS), it remains the sole curative option. However, these patients continue to have significant obstacles for successful transplant including risk for relapse of underlying disease, graft versus host disease (GVHD), and infectious complications. Outcomes of allo-SCT in these patients have improved over time with the evolution of practice of allo-SCT, including modifications of transplant conditioning regimens, supportive care, and earlier recognition of transplant complications. Our study sought to assess the trends in survival in AML and MDS patients undergoing allogeneic transplant at The Ohio State University from 1984-2018. Methods: We analyzed data from 900 consecutive patients who received an allo-SCT (705 AML and 195 MDS). The patients were stratified into 7 different groups based on year of transplant using 5 year increments; group (gp) 1 included 1984-1988, gp 2 1989-1993, gp 3 1994-1998, gp 4 1999-2003, gp 5 2004-2008, gp 6 2009-2013, and gp 7 2014-2018. Progression free survival (PFS) and overall survival (OS) were utilized as primary end points. PFS and OS were calculated using Kaplan Meier Curves. Secondary endpoints included cumulative incidences of grade II-IV and III-IV acute GVHD (aGVHD), chronic GVHD (cGVHD), and non-relapse mortality (NRM). Cumulative incidence rates were estimated and compared using Gray's test accounting for competing risks. Results: Median age at transplant was 52 years (yrs) old (range 18-76) and 55.6% were male. Patients having myeloablative (MA) conditioning regimen comprised 57.6% of the cohort. From 1984 to 2018, there was a statistically significant improvement in both PFS and OS (Figure 1 a and b; p Conclusion: Our study demonstrates significant improvement over the past several decades in survival in AML and MDS patients undergoing allo-SCT. Major factors that likely contribute to improvement in outcomes throughout the years include adjustments in conditioning regimens and GVHD prophylaxis, earlier recognition of complications as well as improved management, and improved general supportive care. Overall, while outcomes have improved significantly throughout the years, post-transplant relapses remains the leading cause of transplant failure in this group. Preventing relapse post-transplant represents a continued target for research today. Disclosures Chaudhry: Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bumma:Amgen: Speakers Bureau; Sanofi: Speakers Bureau. Khan:Amgen: Consultancy; Janssen: Consultancy. Devarakonda:Janssen: Consultancy. Vasu:Omeros: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Kiadis Inc: Other: Kiadis has obtained exclusive licensing requirements from The OHio State University. Jaglowski:CRISPR: Consultancy; Novartis: Consultancy, Research Funding; Juno: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding. William:Kyowa Kirin: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Guidepoint Global: Consultancy; Incyte: Research Funding; Seattle Genetics: Research Funding; Merck: Research Funding; Dova: Research Funding. Mims:Novartis: Speakers Bureau; Agios: Consultancy; Leukemia and Lymphoma Society: Other: Senior Medical Director for Beat AML Study; Abbvie: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Syndax Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Other: Data Safety Monitoring Board. Brammer:Seattle Genetics, Inc.: Speakers Bureau; Celgene Corporation: Research Funding. Efebera:Celgene: Research Funding; Pharmacyclics: Research Funding; Takeda: Honoraria, Speakers Bureau; Ohio State University: Current Employment.

Introduction-Chronic graft-versus-host disease (cGVHD) poses as a major late complication of hematopoietic stem cell transplantation. The role of cGVHD as a determinant in transplant-related morbidity and mortality, infectious complications, prolonged immune suppression, and impaired patient-reported quality of life has been extensively studied. Nonetheless, numerous advances in allogeneic hematopoietic stem cell transplant (allo-SCT) in recent years have expanded the indications for allo-SCT to a broader range of patients, including previously excluded older patients. However, long-term health status of older transplant recipients is poorly studied. Notably, the incidence of cGVHD may increase with age. Therefore, the development of cGVHD and the use of immunosuppressive therapy may lead to a higher degree of non-relapse mortality (NRM) in older patients. The objective of this study was to compare the NRM in both younger and older transplant recipients with and without cGVHD. Methods-We performed a retrospective cohort study of patients that underwent allo-SCT at the Ohio State University from 1999 to 2018. Data was analyzed from 1194 patients who survived or have been followed up with by at least day (d) 180 post-transplantation, among which 373 patients had developed cGVHD. Patients were grouped based on their age into a younger and older population. The older population was defined as ≥60 (N=373, 31%) with the younger population defined as Results-The median age at allo-SCT was 53.0 yr (range: 18-76) and 61.1% were male. Acute myeloid leukemia accounted for 36.7% of transplants, followed by non-Hodgkin's lymphoma (14.8%), acute lymphoid leukemia (12.7%), and myelodysplastic syndrome (11.0%). Additionally, 58.0% received reduced-intensity conditioning regimen. The majority of stem cell donor types were match unrelated (45.3%) and match related (39.8%). Patients who had developed cGVHD by d180, regardless of age, were at higher risk of NRM compared to patients with no cGVHD (hazard ratio [HR]: 1.52, 95% confidence interval [CI]: 1.16-1.99; p=0.002). To examine the influence of age with NRM, we stratified the analysis by cGVHD status by d180. Among patients developed cGVHD by d180, in both univariable (HR 1.22, 95% CI 0.79-1.9, p=0.373) and multivariable analysis (HR: 1.17, 95% CI: 0.74-1.87; p=0.501), there was no statistically significant difference in NRM between patients ≥60 and Conclusion-This study showed that patients with cGVHD by day 180 were at higher risk for higher NRM compared to patients without cGVHD. Among cGVHD patients, there was no difference on the outcome of older patients (≥60 years old) compared to younger ones ( Disclosures Chaudhry: Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bumma:Sanofi: Speakers Bureau; Amgen: Speakers Bureau. Khan:Amgen: Consultancy; Janssen: Consultancy. Devarakonda:Janssen: Consultancy. Vasu:Kiadis Inc: Other: Kiadis has obtained exclusive licensing requirements from The OHio State University; Janssen: Membership on an entity's Board of Directors or advisory committees; Omeros: Membership on an entity's Board of Directors or advisory committees. Jaglowski:Novartis: Consultancy, Research Funding; Juno: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding; CRISPR: Consultancy. William:Celgene: Consultancy, Honoraria; Dova: Research Funding; Guidepoint Global: Consultancy; Merck: Research Funding; Kyowa Kirin: Consultancy, Honoraria; Seattle Genetics: Research Funding; Incyte: Research Funding. Mims:Syndax Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Other: Data Safety Monitoring Board; Abbvie: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Leukemia and Lymphoma Society: Other: Senior Medical Director for Beat AML Study; Novartis: Speakers Bureau; Agios: Consultancy. Brammer:Bristol-Myers Squibb: Research Funding; Celgene: Research Funding; Seattle Genetics: Honoraria, Speakers Bureau; Kymera: Honoraria; Verastem Oncology: Other: Travel. Saad:Magenta Therapeutics: Other: Personal Fees; Incyte Pharmaceuticals: Other: Personal Fees; Amgen: Other: research support; Kadmon: Other: research support; Orcabio: Other: research support. Efebera:Takeda: Honoraria, Speakers Bureau; Pharmacyclics: Research Funding; Celgene: Research Funding; Ohio State University: Current Employment.

Introduction: Acute graft versus host disease (aGVHD) remains a leading cause of morbidity and mortality in allogeneic hematopoietic stem marrow transplant (allo-HSCT), with rates ranging from 30% to 70%. Preventing GVHD without impairing the graft-versus-tumor effect remains an important goal for successful allo-HSCT. Tacrolimus (TAC), a calcineurin inhibitor that prevents T-cell activation, is commonly used as aGVHD prophylaxis. The influence of TAC has proved effective for preventing aGVHD after allo-HSCT. There is also variability in the serum concentrations of TAC and very little is known on the impact of early (first 4 weeks) TAC levels on aGVHD incidence. Given the immunologic events that lead to aGVHD, which occur within the first few days after transplant, we sought to assess whether early TAC levels were associated with aGVHD. Methods: Data were analyzed for 707 consecutive patients undergoing allo-HSCT at the Ohio State University between 2002- 2016. All patients received standard prophylaxis with TAC daily and methotrexate at a dose of 5mg/m2 on days +1, +3, +6, and +11 post allo-HSCT. Patients received anti-thymoglobulin (ATG) if receiving stem cells from an unrelated/mismatch related donor. The TAC target range was 5-12 ng/mL averaged over a 7-day period. The primary outcome of interest was the incidence of aGVHD and its association with the mean weekly TAC levels. Secondary endpoints included incidence of chronic GVHD (cGVHD), relapse and overall survival (OS). Fine and Gray's proportional hazard models accounting for competing risks were used to evaluate the association between TAC levels and outcome of aGVHD, cGVHD and relapse. Cox proportional hazard models were used for the association with OS. Mean weekly TAC levels were included in the analyses as continuous variables and then divided into tertiles. A multivariable model adjusted for confounding factors. Results: Among the 707 patients, median age was 53 years (range: 19-75) and 60.7% were male. In all, 68% patients received reduced-intensity conditioning and the remaining 32% received myeloablative conditioning. The median age of donors was 34 years (range: 18-81) with 74.7% male. Of the donors, 36.9% were match related and 55.9% match unrelated. Peripheral blood was the stem cell source for 90.2% of the patients. A total of 449 (63.5%) patients received ATG. The diagnosis included acute myeloid leukemia (36.3%), non-Hodgkin lymphoma (16.41%), myelodysplastic syndrome (11.7%), and acute lymphoblastic leukemia (11.88%). The mean weekly TAC concentrations at weeks 1, 2, 3 and 4 were 8.0, 9.7, 11.3 and 10.5 ng/mL, respectively. The cumulative incidence of grades II-IV aGVHD was 40% (95% confidence interval (95% CI): 36%-43%) at day 100 and 45% (95% CI: 41%-48%) at day 180 post-transplant. In univariable analysis, high TAC level at week 1 was associated with lower grade II-IV aGVHD (Hazard ratio (HR), 0.96; 95%CI, 0.93-0.99; p = 0.006). We examined the effect of week 1 TAC levels categorized into tertiles (< 5.85, 5.85-8.95 and >8.95 ng/ml). Higher level of TAC (>8.95 ng/ml) was associated with lower risk of aGVHD (Figure 1a). In multivariable analysis, week 1 TAC levels > 5.85 ng/ml remained associated with a lower risk of grade II-IV aGVHD. However, only levels of 5.85-8.95 ng/ml were associated with statistically significant lower risk with HR=0.75 95% CI, 0.57-0.98; p=0.04 compared to the lower group (7.2 ng/ml (HR: 0.78, 95%CI: 0.62-0.98; p=0.03). The cumulative incidence of cGVHD was 41% (95% CI: 37%-44%) at 1 year post-allo-HSCT. Since GVHD is closely intertwined with the graft-versus-tumor effect, we examined whether early TAC levels influenced the risk of disease relapse. TAC levels at week 1 were not associated with relapse. However, week 2 TAC level >10.6 ng/ml was associated with an increased risk of relapse in multivariable analysis (HR, 1.37, CI, 1.01-1.85, p=0.043) (Figure 1b), after adjusting for confounding variables. The cumulative incidence of relapse at 1, 3 and 5 year post allo-HSCT was 33%, 38% and 40%, respectively. TAC levels at weeks 1, 2, 3 and 4 were not associated with OS. Conclusion: Achieving mean whole-blood level of tacrolimus between 6.0-9.0 ng/ml within the first week post-allogenic bone marrow transplantation may reduce the risk of aGVHD. Disclosures Rosko: Vyxeos: Other: Travel support. Vasu:Boehringer Ingelheim: Other: Travel support; Seattle Genetics: Other: Clinical trial support. Jaglowski:Kite: Consultancy, Other: advisory board, Research Funding; Juno: Consultancy, Other: advisory board; Novartis: Consultancy, Other: advisory board, Research Funding; Unum Therapeutics Inc.: Research Funding. William:Techspert: Consultancy; Guidepoint Global: Consultancy; Defined Health: Consultancy; Celgene Corporation: Consultancy; Kyowa Kirin, Inc.: Consultancy. Mims:Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astellas Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; PTC Therapeutics: Membership on an entity's Board of Directors or advisory committees. Brammer:Bioniz Therapeutics, Inc.: Research Funding; Viracta Therapeutics, Inc.: Research Funding; Verastem, Inc: Research Funding. Saad:Actinium Pharma Inc: Consultancy; Amgen: Other: Research Support; Kadmon: Other: Research Support; OrcaBio: Other: Research Support. Efebera:Janssen: Speakers Bureau; Akcea: Other: Advisory board, Speakers Bureau; Takeda: Honoraria.

Introduction: NPM1 gene mutations are a common molecular aberration in acute myeloid leukemia (AML). In the absence of concurrent high FLT3-ITD ratio mutations (>0.5), NPM1 mutations typically associate with higher complete remission (CR) rates following intensive induction chemotherapy. NPM1 mutations have been shown to be stable markers of persistent disease or impending relapse during CR or complete remission with incomplete count recovery (CRi). Given the clinical implications that persistent NPM1 mutations can have during CR/CRi, we used Deep Amplicon sequencing on CR/CRi bone marrow (BM) samples collected from adult de novoNPM1-mutated AML patients to determine the ability of NPM1 mutations at both a high and lower sensitivity next generation sequencing methods and also the presence of additional clonal abnormalities on relapse risk. Methods: We performed targeted next generation sequencing (NGS) analysis in addition to NPM1 Deep Amplicon sequencing on paired BM or blood samples collected from 38 newly diagnosed NPM1-mutated AML patients during CR/CRi after successful induction (1-2 courses of 7 + 3) and, if available, at relapse. NPM1 mutated NGS libraries were prepared using a KAPA HyperPlus Kit (Roche, Pleasanton, CA) and xGen Lockdown Probes (IDT, Coralville, IA). Libraries were sequenced using the Illumina HiSeq 4000 (Illumina, San Diego, CA). GATK's MuTect2 was used to perform variant calling. Variant allele frequency (VAF) cut-off for the NGS panel was 0.05 (5%) with the exception of hotspot variants in IDH1 (R132) and IDH2 (R140) where variants detected to a level of 0.01 (1%) were included. The VAF cut off used for NPM1 Deep Amplicon sequencing was 0.00012 (0.012%). Results: Targeted NGS analysis and NPM1 Deep Amplicon sequencing had exceptional concordance at the level of detection of VAF= 0.05 (Figure 1). Of 38 patients, 23 patients had undetectable NPM1 mutations as analyzed through NPM1 Deep Amplicon sequencing of whom 9 (38.1%) relapsed. In contrast, 15 patients were positive by NPM1 Deep Amplicon sequencing and 9 (60%) relapsed. Only 4 patients had detectable persistent NPM1 mutations after induction according to both detection techniques and two of these relapsed. We next examined the potential impact of clearing both NPM1 mutation and co-occurring mutations together on relapses (Figure 2). A total of 15 patients cleared all of their clonal abnormalities and 5 (27%) relapsed. In contrast, of the 23 patients who did not clear the NPM1 mutation and/or another co-occurring mutation at remission, 14 (61%) have relapsed. Eleven of the relapsed patients had relapse samples available of whom all had persistent NPM1 mutation at this time. Paired CR/CRi and relapsed samples showed acquisition or recurrence of several other mutations, most notably FLT3-ITD, IDH1, and IDH2 which are all targetable with small molecule therapeutics. Conclusions: The use of Deep Amplicon sequencing to identify NPM1 mutations at a lower detection threshold compared to standard NGS techniques was more sensitive, but did not appear to fully inform relapse rates in NPM1-mutated AML patients after receipt of induction therapy. The appearance of other AML-associated mutations, identified together with NPM1 at time of remission, was more frequent among patients relapsing. These pilot data provide support for concurrent assessment of Deep Amplicon sequencing together with a broad standard NGS AML mutational assay to further enhance risk stratification of NPM1-mutated patients. Additionally, while NPM1 clones are present in all patients examined at the time of relapse, persistence or development of targetable clones justifies repeat broad NGS sequencing at this time. Figure Disclosures Bhatnagar: Novartis and Astellas: Consultancy, Honoraria; Cell Therapeutics, Inc.: Other: Research support; Karyopharm Therapeutics: Other: Research support. Mims:Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astellas Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; PTC Therapeutics: Membership on an entity's Board of Directors or advisory committees. Behbehani:Fluidigm corporation: Other: Travel funding. Byrd:Novartis: Other: Travel Expenses, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Ohio State University: Patents & Royalties: OSU-2S.

Background: Acute myeloid leukemia (AML) is a disease for which there is an urgent need for therapy that is more effective and less toxic. Antibody based therapy has been of limited success due to both the lack of consistent immunophenotype in AML as well as the overlap with normal hematopoetic stem cells (HSCs). CD37 is a tetraspanin best characterized for its role in B-cell development and immune response (Van Spriel et al., 2004, 2009, 2012), recently shown to be expressed on AML cells but not in normal HSCs (Pereira et al.,2015). Debio 1562 (formerly IMGN529) is a potent antibody drug conjugate (ADC) directed at CD37, comprised of the antibody K7153A linked to the microtubule inhibitor (DM1) and has already demonstrated tolerability and efficacy in early phase clinical trials in lymphoid malignancies. We evaluated the expression of CD37 across primary AML samples as well as the activity of Debio 1562 in both in vitro and in vivo AML model systems. Methods: MTS assays were used to assess relative viability in AML cell lines with (THP1, OCI-AML3) or without (KG-1a) CD37 expression. Cells were treated with either the ADC, the payload conjugated to an isotype antibody (Iso-DM1) or a vehicle control for 72 hours. After determining the IC50 for each cell line, flow cytometry annexin V/PI was performed to assess apoptosis and cell death. THP-1 and OCI-AML3 CD37 knock out cell lines were created using an inducible CRISPR Cas9 system and evaluated by MTS and annexin V/PI following confirmation of knockdown of CD37 expression. Primary AML samples were obtained to assess CD37 expression by flow cytometry using K7153A-PE and separately used to evaluate direct cytotoxicity in an in vitroassay. Peripheral blood mononuclear cells from newly diagnosed AML patients were treated with either therapy, cells were harvested after 72 hours and subsequently stained with CD2/CD19/CD45 as well as EdU to assess degree of proliferation and analyzed using flow cytometry with the addition of Countbright beads to measure absolute cell counts. In vivo therapy evaluations were performed in NSG mice were engrafted with the THP1 cell line, and then treated with either the ADC, Iso-DM1 or vehicle. The mice were treated twice weekly with 10mg/kg given IP, for 7 total doses. The mice were monitored for overall survival. Results: Analysis of the TCGA database shows AML patients with higher levels of CD37 transcripts had lower overall survival (p Conclusions: CD37 is expressed across a wide range of AML subtypes, and higher transcript levels of CD37 expression is associated with decreased survival. Despite the majority of primary samples showing minimal to modest expression of the protein when compared to B lymphocytes, CD37 is an efficient target on AML cells using Debio 1562. Additional studies are ongoing to evaluate the mechanism of CD37 trafficking in myeloid cells as well as the ability to upregulate this important target. This work provides rationale for phase I clinical trials of Debio 1562 in AML patients, as well as demonstrating CD37 as a potential target for other CD37 Immunotherapies. Figure. Figure. Disclosures No relevant conflicts of interest to declare.

Background: Haploidentical hematopoietic cell transplantation (haplo-HCT) is an advancing and potentially curative therapy for patients with hematologic malignancies when the availability of HLA-matched donors are limited. The common source for haplo-HCT is donor bone marrow, but peripheral blood (PB) haplo-HCT is an emerging and less invasive option with similar survival outcomes. However, multiple series showed an increased incidence of culture negative fever early after haplo-HCT, which has been attributed to cytokine release syndrome (CRS) and more commonly observed with PB haplo-HCT. In this study, we investigated the incidence and impact of CRS on clinical outcomes and financial toxicity in PB haplo-HCT patients treated at a single center. Methods: A total of 40 patients who underwent PB haplo-HCT in the Ohio State University between Jan 2015 - Dec 2017 were included. CRS was defined and graded based on the criteria proposed by Lee, et al (Blood, 2014). Symptoms occurring before day +14 were included, patients with a documented infection (e.g. positive culture data) and clinical suspicion of sepsis were excluded. Overall survival (OS) was defined as the time from transplantation until death. Transplant-related mortality (TRM) was defined as death before day +28 from any cause and patients who died after day +28 with no evidence of disease. Results:. The median age at HCT was 53 years (range, 19 to 74), 63% were male. The most common diagnosis was acute myeloid leukemia (47.5%), followed by lymphoma (22.5%), acute lymphoblastic leukemia (7.5%) and myelodysplastic syndrome (7.5%). Two patients had undergone previous autologous HCT. At the time of haplo-HCT, 62% of patients were in complete remission, 38% had relapsed/refractory disease. Donor was the child in 58%, sibling in 24% and parent in 18% with an antigen match ratio of 5/10 in 50%, 6/10 in 30%, 7/10 in 12.5%, 8/10 in 7.5%. Mismatch for sex and ABO blood group were seen in 50% and 45%, respectively. Twenty percent of patients received myeloablative conditioning with fludarabine/busulfan/thiotepa, while 80% received reduced-intensity regimen with fludarabine/cyclophosphamide/total body irradiation. The incidence of CRS was 85%, including grade 1-2 CRS in 77.5% and grade 3-4 CRS in 7.5%. Time to the onset of CRS was Conclusions: CRS is commonly observed after PB haplo-HCT and usually manifests with fever within 48 hours of cell infusion. We observed favorable survival outcomes in patients who experienced mild CRS, which may suggest an association between mild CRS and graft-versus-leukemia effect. A minority of patients developed severe CRS requiring intensive care unit support, which was associated with poor OS, high TRM, prolonged hospital stay and increased financial toxicity. Further studies investigating biomarkers that can predict the development of severe CRS might enable the incorporation of CRS prophylaxis (e.g. with tocilizumab) into standard conditioning regimens for PB haplo-HCT. Disclosures Vasu: Boehringer Ingelheim Inc: Membership on an entity's Board of Directors or advisory committees. Mims:Novartis: Consultancy; Abbvie Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Devine:Kiadis Pharma: Consultancy. Jaglowski:Novartis Pharmaceuticals Corporation: Consultancy, Research Funding; Kite Pharma: Consultancy, Research Funding; Juno: Consultancy.

Acute Myeloid Leukemia (AML) is a heterogeneous disease that is characterized by an accumulation of neoplastic myeloid precursor cells in the bone marrow. Recently, multiple agents targeting AML associated mutations in FLT3, IDH1 and IDH2 have been developed. However, a majority of AML patients lack these mutations. Therefore, development of a novel therapeutic approach broadly relevant to AML would be attractive. The clonal capacity of AML cells is maintained by leukemic initiating cells (LICs), which possess self-renewal capabilities and are resistant against cytotoxic combination chemotherapy. Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step in the generation of NAD+, which is an important enzymatic cofactor and serves as a metabolite required for cellular respiration. LICs show a higher energy turnover rate than normal cells and are heavily reliant on oxidative phosphorylation. This suggests that energy generation processes, such as NAD+ biosynthesis, are critically required in myeloid malignancies. Thus, targeting the regeneration of NAD+ offers an attractive alternative therapeutic strategy in AML. Unlike many targeted therapies that are limited to one genetic subtype of AML, targeting regeneration of NAD+ via NAMPT inhibition could be relevant to a much broader patient population based upon metabolic differences between tumor and normal cells. We show that inhibition of NAMPT using the agent KPT-9274 induces loss of glycolytic and mitochondrial activity, more specifically a depleted total spare reserve capacity (p Disclosures Mims: Abbvie Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy. Baloglu:Karyopharm Therpeutics: Employment. Senapedis:Karyopharm Therapeutics: Employment.

Background: Mutations of MAP2K1, which encodes MEK1, have been identified in up to half of patients with variant Hairy Cell Leukemia (vHCL).[Waterfall et al., Nat Gen 2014, Mason et al., Leukemia & Lymphoma 2016], and have been associated with vHCL with IGHV4-34 gene usage, which This form of HCL tends to have a worse prognosis than classic HCL or wild type vHCL (Arons et al., Blood 2009), with inferior responses to chemotherapy and shorter durations of remission. Trametinib, an oral inhibitor of MEK1 and MEK2, is FDA approved for treatment of patients with BRAF p.V600E mutant melanoma. We hypothesized that this MEK inhibitor would have activity in MAP2K1 mutant vHCL. Case Report: The patient is a 52 year old man with a history of CD25+, BRAF wildtype, IGHV4-34 usage vHCL diagnosed in 2005. His previous treatments included cladribine, BL22, pentostatin/rituximab, splenectomy, single agent rituximab, ibrutinib, bendamustine/rituximab, and allogeneic transplantation from a matched unrelated donor. The patient experienced disease relapse day +350 post transplant when he developed skin nodules as well as a generalized skin rash. The skin rash appeared clinically consistent with acute GVHD. However, when biopsies of both the skin nodules and skin rash were performed he was found to have relapsed vHCL. He was consented for paired tumor and germline next generation sequencing with a 25-gene amplicon panel which revealed a somatic MAP2K1 K57N mutation that has been shown to constitutively activate MEK [Marks et al., Cancer Res 2008]. As the patient had exhausted the majority of available treatment options, he was prescribed trametinib 2 mg po daily (commercial supply, according to approved melanoma dosing). Within a week of therapy initiation his skin nodules were markedly diminished in size and his generalized rash had resolved. He did develop a new acneiform rash over his face consistent with drug toxicity. This was managed with topical agents with improvement and did not require a dose reduction. Disease restaging following cycle 2 of therapy showed near complete resolution of skin nodules, with disappearance of visible skin rash. Repeat bone marrow biopsy showed unchanged hairy cell index. Skin biopsies were repeated and phospho-ERK (T202/Y204) staining of skin biopsies pre- and post-trametinib were performed (Figure 1). This showed diminished lymphocyte involvement on H&E staining with a decrease in p-ERK expression on immunostaining, indicative of decreased signaling downstream of MEK and consistent with on target trametinib effects. As of this writing, the patient has remained on trametinib for 12 weeks with no recurrence of leukemia cutis rash. Discussion: MEK inhibition with the oral MEKi trametinib is a well tolerated therapy with clinical activity in MAP2K1 mutant vHCL. Additional studies of this agent are warranted. Optimal dose and duration of therapy will need to be explored in prospective clinical trials. Figure 1 Skin biopsies pre- and post-trametinib. (A)(C) H&E staining shows diminished lymphocyte involvement. (B)(D) PhosphoERK immunostaining shows decrease of phosphoERK expression. Bar = 500 μm Figure 1. Skin biopsies pre- and post-trametinib. (A)(C) H&E staining shows diminished lymphocyte involvement. (B)(D) PhosphoERK immunostaining shows decrease of phosphoERK expression. Bar = 500 μm Disclosures Andritsos: Hairy Cell Leukemia Foundation: Research Funding. Anghelina:Hairy Cell Leukemia Foundation: Research Funding. Lozanski:Boehringer Ingelheim: Research Funding; Beckman Coulter: Research Funding; Genentech: Research Funding; Stemline Therapeutics Inc.: Research Funding. Jones:Pharmacyclics, LLC, an AbbVie Company: 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, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background: Acute myeloid leukemia (AML) has very poor long-term survival with traditional therapies. AML has a diverse pathogenesis and likely represents multiple different diseases. Various epigenetic effector proteins are altered in AML by mutation, over-expression, or compartmental displacement and these changes maintain transcriptional programs important for leukemogenesis. The bromodomain and extra-terminal domain (BET) proteins, including BRD2, BRD3 and BRD4, play roles in many cellular functions important to leukemogenesis, such as super-enhancer function, transcriptional elongation, histone acetylation and cell cycle progression. In particular, AML cells depend on BRD4 for expression of the pro-survival proteins MYC and BCL2. BRD4 has therefore become an attractive target for novel therapeutics. PLX51107 is a novel BET inhibitor with a unique binding mode in the acetylated lysine binding pocket of BRD4 that differentiates it from other compounds under investigation. Our group has previously shown this compound to have antineoplastic activity in models of aggressive B cell malignancies. We have now investigated the anti-leukemic properties of PLX51107 in both in vitro and in vivo models of AML. Results: PLX51107 treatment potently reduced viability and proliferation of the human AML cell lines MV4-11, MOLM-13, OCI-AML3, and Kasumi-1, with IC50 of 0.17, 1.8, 0.2 and 0.2 μM, respectively. We then evaluated the in vitro activity of PLX51007 in primary human AML samples. PLX51107 inhibited the proliferation of primary human AML cells co-cultured with HS5 stromal cells. For nearly all samples tested (n=9), the IC50 of PLX51007 was less than 1 μM (average = 0.41 μM, range 0.039 - 1.5 μM). Notably, PLX51107 showed efficacy across a broad range of AML risk groups, including samples with adverse risk features such as 11q23 abnormalities and FLT3-ITD mutations. In comparison, for the same AML samples, the average IC50 for JQ1 was 0.71 μM (range 0.02 - 3.3 μM) and for cytarabine was 3.5 μM (range 0.33 to >10 μM). Furthermore, PLX51107 treatment reduced the clonogenicity of primary AML cells. Following incubation of AML cells in 1 μM PLX51107, there was significantly decreased colony formation (p We next examined the efficacy of PLX51107 in vivo, utilizing luciferase labeled MV4-11 AML cells xenotransplanted into NOD / SCID / IL2rgnull (NSG) immunodeficient mice. Daily oral dosing with 20 mg/kg PLX51107 resulted in prolonged survival (median 47 days) compared to vehicle treated control animals (median 30 days, p< 0.001). Weekly measurement of bioluminescence showed decreased disease burden in PLX51107 treated mice. In addition, human peripheral blood CD45 / CD33 double positive cells were significantly decreased in treated animals. Histologic analysis conducted at day 16 showed decreased leukemic burden in the bone marrow of the PLX51107 treated animals. In addition, examination of tissues from moribund mice at time of euthanasia demonstrated fewer leukemia cells in the spleen, liver and bone marrow. Conclusions: Collectively, our results show pre-clinical activity of PLX51107 in AML, supporting further development of this compound in clinical trials for relapsed or refractory myeloid malignancies. We are currently working to define downstream targets of PLX51107 action and developing patient derived AML xenografts to further characterize the in vivo effects of PLX51107. Disclosures Walker: Gilead Sciences: Research Funding. Bhatnagar:Karyopharm: Research Funding.