Search

Venetoclax-based therapy can induce responses in approximately 70% of older previously untreated patients with acute myeloid leukemia (AML). However, up-front resistance as well as relapse following initial response demonstrates the need for a deeper understanding of resistance mechanisms. In the present study, we report that responses to venetoclax +azacitidine in patients with AML correlate closely with developmental stage, where phenotypically primitive AML is sensitive, but monocytic AML is more resistant. Mechanistically, resistant monocytic AML has a distinct transcriptomic profile, loses expression of venetoclax target BCL2, and relies on MCL1 to mediate oxidative phosphorylation and survival. This differential sensitivity drives a selective process in patients which favors the outgrowth of monocytic subpopulations at relapse. Based on these findings, we conclude that resistance to venetoclax + azacitidine can arise due to biological properties intrinsic to monocytic differentiation. We propose that optimal AML therapies should be designed so as to independently target AML subclones that may arise at differing stages of pathogenesis.Significance:Identifying characteristics of patients who respond poorly to venetoclax-based therapy and devising alternative therapeutic strategies for such patients are important topics in AML. We show that venetoclax resistance can arise due to intrinsic molecular/metabolic properties of monocytic AML cells and that such properties can potentially be targeted with alternative strategies.

Supplementary Figures S1-S5 supporting Main Figures 1-5.

Supplementary Tables S1-S6 describing patient characteristics, gene lists, LSC signatures, and reagents.

Supplemental Data

Purpose:The prognosis of patients with multiple myeloma who are resistant to proteasome inhibitors, immunomodulatory drugs (IMiD), and daratumumab is extremely poor. Even B-cell maturation antigen–specific chimeric antigen receptor T-cell therapies provide only a temporary benefit before patients succumb to their disease. In this article, we interrogate the unique sensitivity of multiple myeloma cells to the alternative strategy of blocking protein translation with omacetaxine.Experimental Design:We determined protein translation levels (n = 17) and sensitivity to omacetaxine (n = 51) of primary multiple myeloma patient samples. Synergy was evaluated between omacetaxine and IMiDs in vitro, ex vivo, and in vivo. Underlying mechanism was investigated via proteomic analysis.Results:Almost universally, primary patient multiple myeloma cells exhibit >2.5-fold increased rates of protein translation compared with normal marrow cells. Ex vivo treatment with omacetaxine resulted in >50% reduction in viable multiple myeloma cells. In this cohort, high levels of translation serve as a biomarker for patient multiple myeloma cell sensitivity to omacetaxine. Unexpectedly, omacetaxine demonstrated synergy with IMiDs in multiple myeloma cell lines in vitro. In addition, in an IMiD-resistant relapsed patient sample, omacetaxine/IMiD combination treatment resensitized the multiple myeloma cells to the IMiD. Proteomic analysis found that the omacetaxine/IMiD combination treatment produced a double-hit on the IRF4/c-MYC pathway, which is critical to multiple myeloma survival.Conclusions:Overall, protein translation inhibitors represent a potential new drug class for myeloma treatment and provide a rationale for conducting clinical trials with omacetaxine alone and in combination with IMiDs for patients with relapsed/refractory multiple myeloma.

Venetoclax-based therapy can induce responses in approximately 70% of older previously untreated patients with acute myeloid leukemia (AML). However, up-front resistance as well as relapse following initial response demonstrates the need for a deeper understanding of resistance mechanisms. In the present study, we report that responses to venetoclax +azacitidine in patients with AML correlate closely with developmental stage, where phenotypically primitive AML is sensitive, but monocytic AML is more resistant. Mechanistically, resistant monocytic AML has a distinct transcriptomic profile, loses expression of venetoclax target BCL2, and relies on MCL1 to mediate oxidative phosphorylation and survival. This differential sensitivity drives a selective process in patients which favors the outgrowth of monocytic subpopulations at relapse. Based on these findings, we conclude that resistance to venetoclax + azacitidine can arise due to biological properties intrinsic to monocytic differentiation. We propose that optimal AML therapies should be designed so as to independently target AML subclones that may arise at differing stages of pathogenesis. Significance: Identifying characteristics of patients who respond poorly to venetoclax-based therapy and devising alternative therapeutic strategies for such patients are important topics in AML. We show that venetoclax resistance can arise due to intrinsic molecular/metabolic properties of monocytic AML cells and that such properties can potentially be targeted with alternative strategies.

Background: Among Medicare value-based payment programs for acute myocardial infarction (AMI), the Hospital Readmissions Reduction Program uses International Classification of Diseases, Tenth Revision ( ICD-10 ) codes to identify the program denominator, while the Bundled Payments for Care Improvement Advanced program uses diagnosis-related groups (DRGs). The extent to which these programs target similar patients, whether they target the intended population (type 1 myocardial infarction), and whether outcomes are comparable between cohorts is not known. Methods: In a retrospective study of 2176 patients hospitalized in an integrated health system, a cohort of patients assigned a principal ICD-10 diagnosis of AMI and a cohort of patients assigned an AMI DRG were compared according to patient-level agreement and outcomes such as mortality and readmission. Results: One thousand nine hundred thirty-five patients were included in the ICD-10 cohort compared with 662 patients in the DRG cohort. Only 421 patients were included in both AMI cohorts (19.3% agreement). DRG cohort patients were older (70 versus 65 years, P P P P P P P =0.006) than the ICD-10 cohort. Two observations help explain these differences: 61% of ICD-10 cohort patients were assigned procedural DRGs for revascularization instead of an AMI DRG, and type 1 myocardial infarction patients made up a smaller proportion of the DRG cohort (34%) than the ICD-10 cohort (78%). Conclusions: The method used to identify denominators for value-based payment programs has important implications for the patient characteristics and outcomes of the populations. As national and local quality initiatives mature, an emphasis on ICD-10 codes to define AMI cohorts would better represent type 1 myocardial infarction patients.

Purpose:The prognosis of patients with multiple myeloma who are resistant to proteasome inhibitors, immunomodulatory drugs (IMiD), and daratumumab is extremely poor. Even B-cell maturation antigen–specific chimeric antigen receptor T-cell therapies provide only a temporary benefit before patients succumb to their disease. In this article, we interrogate the unique sensitivity of multiple myeloma cells to the alternative strategy of blocking protein translation with omacetaxine.Experimental Design:We determined protein translation levels (n = 17) and sensitivity to omacetaxine (n = 51) of primary multiple myeloma patient samples. Synergy was evaluated between omacetaxine and IMiDs in vitro, ex vivo, and in vivo. Underlying mechanism was investigated via proteomic analysis.Results:Almost universally, primary patient multiple myeloma cells exhibit >2.5-fold increased rates of protein translation compared with normal marrow cells. Ex vivo treatment with omacetaxine resulted in >50% reduction in viable multiple myeloma cells. In this cohort, high levels of translation serve as a biomarker for patient multiple myeloma cell sensitivity to omacetaxine. Unexpectedly, omacetaxine demonstrated synergy with IMiDs in multiple myeloma cell lines in vitro. In addition, in an IMiD-resistant relapsed patient sample, omacetaxine/IMiD combination treatment resensitized the multiple myeloma cells to the IMiD. Proteomic analysis found that the omacetaxine/IMiD combination treatment produced a double-hit on the IRF4/c-MYC pathway, which is critical to multiple myeloma survival.Conclusions:Overall, protein translation inhibitors represent a potential new drug class for myeloma treatment and provide a rationale for conducting clinical trials with omacetaxine alone and in combination with IMiDs for patients with relapsed/refractory multiple myeloma.

OBJECTIVE Systemic lupus erythematosus (SLE) has one of the highest 30-day hospital readmission rates among chronic diseases in the United States. This quality improvement initiative developed and assessed the feasibility of a multidisciplinary post-discharge intervention to reduce 30-day readmission rates among SLE patients. METHODS A retrospective study was performed using electronic health records of patients with SLE admitted to a university hospital prior to (non-intervention group) and after initiation of the study intervention (intervention group). The study population included patients with a diagnosis of SLE who were admitted to the hospital for any reason during an eight month time period. The intervention involved sending a templated message at the time of discharge to the rheumatology clinic nurses which prompted the nurses to call the patient to coordinate future visits and provide education. The primary outcome was the 30-day hospital readmission rate. Data was analyzed using a multivariate mixed binomial regression model. RESULTS There were 59 hospitalizations in the non-intervention group and 73 hospitalizations in the intervention group during the eight-month study period. The 30-day readmission rate was 29% in the non-intervention group and 19% in the intervention group. The difference in readmission rates between the two groups was not statistically significant based on the multivariate model. CONCLUSION Our study demonstrates the feasibility of implementing a multi-disciplinary post-discharge intervention to reduce readmission rates for patients with SLE in a large academic medical center. Further investigation is warranted to determine if this approach reduces the unacceptably high hospital readmission rates among SLE patients.

In the United States, the positive predictive value (PPV) of cardiac troponin for type 1 myocardial infarction is substantially lower than in Europe (15% vs. 50%). Further, even with publication of the 4 th Universal Definition of Myocardial Infarction, recent studies have shown that inaccurate classification of myocardial injury is common among clinicians in the United States. These findings are at least partly attributable to clinicians’ knowledge and attitudes about cardiac troponin testing; a survey of these parameters has never been conducted. Clinicians at the University of Colorado completed a brief 8-question multiple-choice survey related to troponin use, definitions of myocardial infarction and clinical assessment of elevated troponin levels. The survey was distributed via secure email and administered electronically using the Qualtrics™ platform. Responses were anonymous, completion was estimated to take 3 minutes and a lottery award system was used as an incentive for participation. Respondents included trainees, advanced practice providers and attending physicians from internal medicine, emergency medicine and medical subspecialties. We plan to obtain a total of 300 responses with descriptive findings of preliminary results included below. The survey was completed by 114 clinicians: 37 interns (32%), 45 residents (39%), 9 advanced practice providers (8%), 11 fellows (10%), and 12 attending physicians (11%). Regarding indications for troponin testing, 93% (106/114) indicated that they “usually” or “always” check troponin levels in patients with chest pain. More interestingly, 46% (52/112) reported checking troponin on “undifferentiated patients” at least half the time. For troponin interpretation, 97% (110/114) of participants identified that troponin levels alone cannot rule in or rule out coronary artery disease. In contrast, only 36% (41/114) and 55% (63/114), respectively, identified the NPV and PPV of a contemporary troponin assay for type 1 MI. Further, only 50% (57/114) of respondents identified that the likelihood of type 1 MI increases as troponin levels increase. Three brief clinical vignettes revealed that, while 78% (89/114) and 74% (45/61) of participants, respectively, identified type 1 MI and type 2 MI presentations, only 40% (21/53) of respondents correctly identified a vignette for non-ischemic myocardial injury. Concordant with this finding, 54% (61/114) of clinicians correctly identified the 4 th Universal Definition of Myocardial Infarction. These preliminary findings highlight important facets of clinician attitudes and knowledge about troponin testing that help explain the poor PPV for troponin and diagnostic misclassification observed among U.S. clinicians. These results could help guide curricular and clinical decision support interventions designed to improve the use and interpretation of cardiac troponin testing.

Background: The Center for Medicare and Medicaid Services uses primary discharge ICD-10 codes for Acute Myocardial Infarction (AMI) to define inclusion in value-based payment programs such as the hospital readmissions reduction program. Prior studies have shown that a significant number of hospitalizations with an ICD-10 code for AMI actually represent a Type 2 MI (T2MI) or non-ischemic myocardial injury (NIMI). Yet, the care of such patients may differ from those with AMI, and their inclusion in value-based payment programs risks inaccurately assessing hospital care and even unwarranted financial penalties. In October 2018, a new ICD-10 code for T2MI was introduced (I21.A1). It is unclear what effect, if any, this new code has had on Type 1 MI (T1MI) representation among discharges assigned an ICD-10 code for AMI. Methods: We screened all discharges from 8 UCHealth hospitals between January 1, 2017 and June 30, 2019 for a primary discharge ICD-10 code of AMI (n=3,445). Hospitalizations occurring during a six month period prior to the introduction of I21.A1 (January 1, 2017 to June 30, 2017) and a six-month period after the introduction of I21.A1 (January 1, 2019 to June 30, 2019) were selected for chart review. Using the 4th Universal Definition of MI, hospitalizations were assigned a gold-standard clinical diagnosis of T1MI, T2MI, or NIMI. The cohorts were compared according to the primary outcomes of readmission and mortality at 30 and 90 days. Results: Of 1,364 discharges reviewed, 676 occurred in the pre-I21.A1 period and 667 occurred in the post-I21.A1 period. In the pre-I21.A1 cohort, 86% (585 of 676) of discharges met clinical criteria for T1MI, 10% (67 of 676) were deemed T2MI and 4% (24 of 676) represented NIMI. In the post-I21.A1 group, 93% (626 of 676) were deemed T1MI, while 5% (33 of 667) were deemed T2MI and 2% (12 of 667) met criteria for NIMI. The post-I21.A1 cohort had significantly fewer readmissions at 30 and 90 days when compared to the pre-I21.A1 cohort, but had similar rates of mortality. Conclusions: After the introduction of an ICD-10 code for T2MI, fewer patients with T2MIs and NIMIs were eligible for inclusion in value-based programs. Concomitantly, we observed lower readmission rates among patients with an ICD-10 code for AMI after the T2MI code was introduced.

Background: High-altitude (HA) pregnancies have been associated with decreased glucose levels and increased insulin sensitivity versus sea level. Our objective was to determine if the prevalence of gestational diabetes mellitus (GDM) and the impact of demographic characteristics on GDM diagnosis differed at moderate altitude (MA) versus HA. Methods: Using a retrospective cohort design, we compared women living at HA (>8250 ft) and MA (4000–7000 ft) during pregnancy. Exclusion criteria were as follows: multiple gestation, preexisting diabetes, unavailable GDM results, or relocation from a different altitude during pregnancy. GDM diagnosis was determined using Carpenter and Coustan criteria. Data were compared by t-test (continuous variables) or chi-squared tests (categorical variables). Univariate, multivariate, and stepwise regression models were used to assess the impact of various factors on GDM prevalence. Results: There was no difference in GDM prevalence between altitudes in these populations; the relationship between altitude and GDM was nonsignificant in all regression analyses. At MA, maternal age, Hispanic ethnicity, body mass index (BMI), and gestational age (GA) at testing increased GDM incidence in univariate analyses. At HA, maternal age, Hispanic ethnicity, and multiparity increased GDM incidence in univariate analyses. Conclusion: While GDM prevalence did not differ between MA and HA, the impact of maternal demographic characteristics on GDM risk varied by altitude group. Higher BMI and greater GA at testing increased the incidence of GDM at MA, but not at HA. Multiparity had an effect at HA, but not MA. These differences may represent subtle differences in glucose metabolism at HA.

The "Minnesota" reduced-intensity conditioning (RIC) cord blood transplantation (CBT) regimen (standard RIC) of fludarabine (Flu) (200 mg/m2), cyclophosphamide (Cy) (50 mg/kg), and 200- or 300-cGy total body irradiation (TBI) is the most published RIC CBT regimen. Though well tolerated, high relapse rates remain a concern with this regimen. Intensification of conditioning may reduce relapse without increasing transplant-related mortality (TRM). We performed a retrospective cohort comparison of outcomes in adult patients who underwent first double-unit CBT with standard RIC as compared with the intensified regimen of Flu 150 mg/m2, Cy 50 mg/kg, thiotepa 10 mg/kg, and 400-cGy TBI (intensified RIC). Of the 99 patients studied, 47 received intensified RIC. Acute myelogenous leukemia was the major indication for transplant. The median age at transplant was 67 years (range, 24 to 74 years) and 54 years (range, 25 to 67 years) in standard RIC and intensified RIC, respectively. Median hematopoietic stem cell transplantation comorbidity index was 3 (range, 0 to 5) and 1 (range, 0 to 6) in the standard RIC and intensified RIC groups, respectively. Median follow-up among survivors was 22 months (range, 3.7 to 79 months) following standard RIC and 15 months (range, 2.8 to 36 months) following intensified RIC. The cumulative incidence (CI) of relapse was significantly lower following intensified RIC compared with standard RIC (P = .0013); this finding maintained significance in multivariate analysis (P = .045). TRM was comparable between the 2 groups (P = .99). Overall survival (OS) was significantly improved following intensified RIC as compared with standard RIC (P = .03). Median OS was 17 months following standard RIC versus not reached followed intensified RIC. The CI of grade II to IV acute graft-versus-host disease (GVHD) was significantly higher in the intensified RIC cohort than the standard RIC-cohort (P = .007), while CI of grade III to IV acute GVHD, any chronic GVHD, and moderate-to-severe chronic GVHD was comparable in each cohort (P = .20, P = .21, and P = .61, respectively). This retrospective analysis shows an improvement in OS and decreased relapse without increase in TRM in patients receiving intensified RIC as compared with standard RIC. Our data suggest that consideration of thiotepa-based intensified RIC may improve outcomes in fit, older patients undergoing double-unit CBT.

The adjuvanted varicella-zoster virus (VZV) glycoprotein E (gE) subunit herpes zoster vaccine (HZ/su) confers higher protection against HZ than the live attenuated zoster vaccine (ZV). To understand the immunologic basis for the different efficacies of the vaccines, we compared immune responses to the vaccines in adults 50 to 85 years old. gE-specific T cells were very low/undetectable before vaccination when analyzed by FluoroSpot and flow cytometry. Both ZV and HZ/su increased gE-specific responses, but at peak memory response (PMR) after vaccination (30 days after ZV or after the second dose of HZ/su), gE-specific CD4+ and CD8+ T cell responses were 10-fold or more higher in HZ/su compared with ZV recipients. Comparing the vaccines, T cell memory responses, including gE-IL-2+ and VZV-IL-2+ spot-forming cells (SFCs), were higher in HZ/su recipients and cytotoxic and effector responses were lower. At 1 year after vaccination, all gE-Th1 and VZV-IL-2+ SFCs remained higher in HZ/su compared with ZV recipients. Mediation analyses showed that IL-2+ PMR were necessary for the persistence of Th1 responses to either vaccine and VZV-IL-2+ PMR explained 73% of the total effect of HZ/su on persistence. This emphasizes the biological importance of the memory responses, which were clearly superior in HZ/su compared with ZV participants.

OBJECTIVE The objective was to evaluate the impact of evidence-based clinical decision support tools integrated directly into provider workflow in the electronic health record on utilization of computed tomography (CT) brain, C-spine, and pulmonary embolism (PE). METHODS Validated, well-accepted scoring tools for head injury, C-spine injury, and PE were embedded into the electronic health record in a manner minimally disruptive to provider workflow. This was a longitudinal, before/after study in five emergency departments (EDs) in a healthcare system with a common electronic health record. Attending ED physicians practicing during the entire study period were included. The main outcome measure was proportion of CTs ordered by provider (total number of CT scans of a given type divided by total patients seen by that provider) in aggregate in the pre- and post intervention period. RESULTS There were 235,858 total patient visits analyzed in this study with an absolute decrease of 6,106 CT scan ordering for the three studies. Across all sites, there was greater than 6% decrease in utilization of CT brain and CT C-spine (-10%, 95% CI = -13% to -7%, p

We compared outcomes among adult matched related donor (MRD) patients undergoing peripheral blood stem cell transplantation and adult patients undergoing double unit cord blood transplantation (CBT) at our center between 2010 and 2017. A total of 190 CBT patients were compared with 123 MRD patients. Median follow-up was 896 days (range, 169-3350) among surviving CBT patients and 1262 days (range, 249-3327) among surviving MRD patients. Comparing all CBT with all MRD patients, overall survival (OS) was comparable (P = .61) and graft-versus-host disease (GVHD) relapse-free survival (GRFS) was significantly improved among CBT patients (P = .0056), primarily because of decreased moderate to severe chronic GVHD following CBT (P < .0001; hazard ratio [HR], 3.99; 95% confidence interval [CI], 2.26-7.04). Among patients undergoing our most commonly used MRD and umbilical cord blood (CB) myeloablative regimens, OS was comparable (P = .136) and GRFS was significantly improved among CBT patients (P = .006). Cumulative incidence of relapse trended toward decreased in the CBT group (P = .075; HR, 1.85; CI 0.94-3.67), whereas transplant-related mortality (TRM) was comparable (P = .55; HR, 0.75; CI, 0.29-1.95). Among patients undergoing our most commonly used nonmyeloablative regimens, OS and GRFS were comparable (P = .158 and P = .697). Cumulative incidence of both relapse and TRM were comparable (P = .32; HR, 1.35; CI, 0.75-2.5 for relapse and P = .14; HR, 0.482; CI, 0.18-1.23 for TRM). Our outcomes support the efficacy of CBT and suggest that among patients able to tolerate more intensive conditioning regimens at high risk for relapse, CB may be the preferred donor source.

The oncogenic drivers and progression factors in multiple myeloma (MM) are heterogeneous and difficult to target therapeutically. Many different MM drugs have emerged, however, that attack various phenotypic aspects of malignant plasma cells. These drugs are administered in numerous, seemingly interchangeable combinations. Although the availability of many treatment options is useful, no clinical test capable of optimizing and sequencing the treatment regimens for an individual patient is currently available. To overcome this problem, we developed a functional ex vivo approach to measure patients’ inherent and acquired drug resistance. This method, which we termed myeloma drug sensitivity testing (My-DST), uses unselected bone marrow mononuclear cells with a panel of drugs in clinical use, followed by flow cytometry to measure myeloma-specific cytotoxicity. We found that using whole bone marrow cultures helped preserve primary MM cell viability. My-DST was used to profile 55 primary samples at diagnosis or at relapse. Sensitivity or resistance to each drug was determined from the change in MM viability relative to untreated control samples. My-DST identified progressive loss of sensitivity to immunomodulatory drugs, proteasome inhibitors, and daratumumab through the disease course, mirroring the clinical development of resistance. Prospectively, patients’ ex vivo drug sensitivity to the drugs subsequently received was sensitive and specific for clinical response. In addition, treatment with

CONTEXT: Geriatric hip fractures are increasingly common and confer substantial morbidity and mortality. Fragmentation in geriatric hip fracture care remains a barrier to improved outcomes. OBJECTIVE: To evaluate the impact of a comprehensive geriatric hip fracture program on long-term mortality. DESIGN: We conducted a retrospective cohort study of patients aged 65 years and older admitted to our academic medical center between January 1, 2012, and March 31, 2016 with an acute fragility hip fracture. Mortality data were obtained for in-state residents from the state public health department. MAIN OUTCOME MEASURES: Mortality within 1 year of index admission and overall survival based on available follow-up data. RESULTS: We identified 243 index admissions during the study period, including 135 before and 108 after program implementation in October 2014. The postintervention cohort trended toward a lower unadjusted 1-year mortality rate compared with the preintervention cohort (15.7% vs 24.4%, p = 0.111), as well as lower adjusted mortality at 1 year (relative risk = 0.73, 95% confidence interval = 0.46–1.16, p = 0.18), although the differences were not statistically significant. The postintervention cohort had significantly higher overall survival than did the preintervention cohort (hazard ratio for death = 0.43, 95% confidence interval = 0.25–0.74, p = 0.002). CONCLUSION: Fixing fragmentation in geriatric hip fracture care such as through an orthogeriatric model is essential to improving overall survival for this patient population.

Grading of follicular lymphoma (FL) is important in deciding on a watchful waiting strategy or initiation of chemoimmunotherapy, but accurate determination of grade is complicated by disease heterogeneity and inter-reader variability. Positron emission tomography-computed tomography parameter maximum standardized uptake value (SUVmax) has been studied in differentiating low- versus high-grade FL, but novel parameters total lesion glycolysis (TLG) and total metabolic tumor volume (TMTV) have not been studied and may provide better sensitivity and specificity. SUVmax, TLG, and TMTV were compared in 49 patients with both low-grade and grade 3A FL, and TLG and TMTV had comparable sensitivities and specificities to SUVmax in differentiating low-grade from grade 3A FL. TLG and TMTV are reproducible adjuncts but not replacements for gold-standard biopsy in grading FL. BACKGROUND: Follicular lymphoma (FL) grading, low-grade 1–2 (LG) versus grade 3A (3A), informs management. However, accurate grading is challenging owing to disease heterogeneity and inter-reader variability. The [18F]-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) parameter maximum standardized uptake value (SUVmax) has utility in differentiating LG from 3A FL, but the utility of novel parameters total lesion glycolysis (TLG) and total metabolic tumor volume (TMTV) is unknown. PATIENTS AND METHODS: Retrospective review of diagnostic pre-treatment PET-CTs of patients aged > 18 years with FL grades 1–3A from 2009–2017 was performed. PET-CT parameters SUVmax, TLG, and TMTV values were generated using manual (MW) and semi-automated workflows (SW). Poisson regression and receiver operating characteristic curves were used to compare PET-CT parameters between LG and 3A. RESULTS: A total of 49 patients with FL were identified: 38 LG and 11 3A. PET-CT parameters were significantly higher in 3A as compared with LG in both workflows. The cutoff values, sensitivities, and specificities were as follows: SUVmax: 10.4, 64%, and 74% in MW and 11.9, 73%, and 76% in SW; TLG: 543, 82%, and 74% in MW and 371, 73%, and 74% in SW; and TMTV: 141, 73%, and 76% in MW and 93, 64%, and 76% in SW. SUVmax had identical cutoff, sensitivity, and specificity across all 3 SWs, whereas TLG and TMTV had considerable variance across all 3 SWs. CONCLUSIONS: TLG and TMTV are comparable to SUVmax in differentiating LG versus 3A FL. Cutoffs, sensitivities, and specificities varied in MW versus SW. Novel PET-CT parameters serve as reproducible adjuncts but not replacements for biopsy in differentiating grades of FL.

Background: Patients with elevated troponin (cTn) in the absence of Acute Myocardial Infarction (AMI) present a diagnostic dilemma: they at high risk of adverse cardiac events, yet there is little evidence on how they should be managed clinically. In recent years, greater sensitivity of cTn assays and less selective use of cTn in clinical practice have led to a greater number of non-AMI patients with elevated troponin. The exact scope of the problem in routine clinical practice is not known, as published estimates of troponin’s positive predictive value (PPV) for AMI range from 15% to 70%. We sought to define troponin’s PPV for AMI at our institution and examine both process and outcome measures for AMI and non-AMI patients. Methods: In a retrospective cohort analysis of patients evaluated at the University of Colorado Hospital, we identified 5,903 hospital encounters between January 1, 2017 and October 6, 2018 in which patients were found to have an elevated serum troponin level (>0.04 ng/mL, Siemens Advia Centaur Tnl-Ultra). We used ICD-10 codes, billing diagnosis related groups (DRGs), or inclusion in the NCDR® ACTION Registry® to identify patients with a diagnosis of AMI. Patients not captured by one of these diagnoses were categorized as non-AMI. We then compared AMI and non-AMI patients according to the primary outcome of 100-day mortality. Secondary outcomes and process measures were also examined. Results: Out of 5,903 hospital encounters in which elevated cTn was detected, 730 were associated with any diagnosis of AMI (PPV 12.4%). The PPV was lower for individual AMI diagnosis groups. The primary outcome of 100-day mortality was observed in 10.3% of AMI patients versus 20.5% of non-AMI patients (p < 0.001). AMI patients also had significantly shorter hospitalizations, higher rates of inpatient echocardiography and higher rates of P2Y12 inhibitor therapy (Table 1). Conclusion: The PPV of a contemporary troponin assay for AMI was 12.4% in routine clinical practice at a tertiary care academic hospital. Concordant with prior studies, non-AMI patients had worse outcomes. With high-sensitivity troponin (hsTn) assays poised to increase the prevalence of non-AMI troponin elevation, guidance is needed regarding the appropriate use of hsTn as well as the evaluation and treatment of non-ACS patients.

Background: In the Unites States, there are three major approaches to identify patients diagnosed with Acute Myocardial Infarction (AMI). The Center for Medicare and Medicaid Services uses ICD-10 codes (1) for the Value-Based Payments program whereas it uses DRG codes (2) for the Inpatient Prospective Payment System. Hospital administrators, meanwhile, often use the NCDR® ACTION Registry® (3) to examine process and outcome measures for their AMI patients. Understanding which patients are captured by these different classification systems, and whether there is agreement between them, has important implications for hospitals’ efforts to optimize performance measures and payments for AMI. Methods: In a retrospective cohort analysis, we examined 730 hospitalizations at the University of Colorado Hospital between January 1, 2017 and October 6, 2018 that were captured by one of the three methods for identifying AMI patients: 1) ICD-10, 2) DRG, or 3) ACTION. Categories were not mutually exclusive. Agreement between DRG, ICD-10 and ACTION diagnoses of AMI was assessed by percentage agreement with the total AMI cohort and dual-comparison kappa statistics. AMI cohorts defined by ICD-10 vs. DRG vs. ACTION were then compared according to the primary outcome of 100-day mortality, as well as secondary outcomes of 30-day readmission, length of stay (LOS), P2Y12 inhibition and rates of inpatient echocardiography. Results: Among 730 hospitalizations with at least one diagnosis of AMI, 617 (84.5%) were assigned a primary ICD-10 code for AMI, 227 (31.1%) were assigned a DRG code for AMI, and 479 (65.6%) carried a diagnosis of AMI in ACTION. Only 112 (15.3%) were captured by all 3 diagnosis groups (ICD-10, DRG and ACTION). 159 (21.7%) hospitalizations were captured by both ICD-10 and DRG diagnoses (Kappa -0.143); 425 (58.2%) were included in ICD-10 and ACTION groups (Kappa 0.141); 121 (16.6%) were included in DRG and ACTION groups (Kappa -0.137). Outcomes and process measures as a function of diagnosis category are presented in Figure 1. Conclusion: Only about 15% of patients with a diagnosis of AMI were included in all three diagnosis groups (ICD-10, DRG and ACTION). There may be significant between-group differences in outcomes and process measures. These data emphasize the need to harmonize administrative definitions for AMI.

Background: Venetoclax (ven)+azacitidine (aza) is the standard of care for untreated acute myeloid leukemia (AML) patients (pts) ≥75 years or unfit for intensive induction chemotherapy (IC) due to comorbidities. While the standard of care for younger newly diagnosed pts is IC, long term outcomes for all but favorable risk pts are suboptimal. Specifically, pts with adverse risk disease, per the European Leukemia Network (ELN), are more likely to be refractory to IC and have low rates of long term survival. Ven based regimens have a ~70% response rate in the upfront setting; in contrast to IC, those with adverse risk do not have lower response rates. This study explores the feasibility and outcomes of ven+aza for newly diagnosed younger AML pts who are not necessarily unfit for IC, but carry adverse risk features that make them less likely to respond to this therapy. Methods: This is an interim analysis of an ongoing phase 2 study (NCT03573024) of a planned 36 untreated adverse risk AML pts 18-59. Pts have adequate organ function and white blood cell counts Results: 8 have enrolled between November 2018 and July 2020; median age is 33 (22-52). All have adverse risk disease (Table 1). There were 179 adverse events (AEs); 35 related. The ≥grade 3 events were: fatigue (N=1), leukopenia (N=2), neutropenia (N=2), anemia (N=2), thrombocytopenia (N=1). There were no deaths in the first 60 days. In cycle 1 pts spent a median 10 days (4-19) inpatient and required a median of 2 (0-10) red blood cell transfusions and 3 (0-15) platelet transfusions. Six of 8 (75%) pts responded; all 6 were CRs. 4/6 responses were cytogenetic remissions, 5/6 were MRD negative by MFC and 1/6 was MRD negative by ddPCR. Two pts relapsed, 35 and 84 days after remission; one was successfully salvaged with IC and proceeded to transplant while the other was refractory to IC and died from AML. Two pts were refractory to ven+aza; both were successfully salvaged with IC and have proceeded to transplant. 7/8 proceeded to transplant; 4 required only ven+aza for this outcome and proceeded to transplant a median of 89 days (56-93) after diagnosis. No pts who have proceeded to transplant have relapsed, a median of 340 days (136-444) after transplant. 7/8 remain alive, 345 days (91-586) after enrolling. Conclusions: At the stage 1 interim analysis, the CR rate for ven+aza remains >60% in adverse risk younger patients. With small numbers, up-front treatment with ven+aza allows some younger pts with adverse risk disease a non IC opportunity to achieve a response and proceed to transplant; most of those who relapsed or were refractory were salvaged with IC. Disclosures Pollyea: Syndax: Consultancy; Syros: Consultancy; Abbvie: Consultancy, Research Funding; Daiichi Sankyo: Consultancy; Karyopharm: Consultancy; Novartis: Consultancy; Genentech: Consultancy; Amgen: Consultancy; 47: Consultancy, Research Funding; Janssen: Consultancy; Agios: Consultancy; Glycomimetics: Other; Celgene/BMS: Consultancy; Pfizer: Consultancy; Takeda: Consultancy. OffLabel Disclosure: Venetoclax for younger patients fit for induction chemotherapy

Background: Follow-up time in clinical trials must leverage conflicting aims. To ensure patient safety, investigators often assess toxicity and efficacy endpoints at various times throughout a trial. Yet accurate analysis requires stable estimates of time-to-event outcomes, which can require longer follow-up than is observed in interim analyses. While median follow-up is routinely reported in clinical trials, the stability of time-to-event estimates and their relationship to follow-up times are rarely discussed. However, the potential follow-up of study participants who are censored in a clinical trial can impact time-to-event estimates (Betensky 2015). Methods: A clinical trial of venetoclax + azacitidine in 33 newly diagnosed older patients with AML was conducted at our institution and is described in detail elsewhere (Pollyea 2018). Trial data consisting of follow-up from January 2015 through February 2018 established promising results (overall response rate = 91%; median response duration, progression-free survival, and overall survival (OS) were not yet reached). Due to ongoing interest in median time-to-event patient outcomes that were not reached and thus could not be reported at the time of publication, the data have been re-analyzed on repeated occasions as follow-up has continued, with OS of particular interest. Median follow-up was calculated using the reverse Kaplan-Meier method. Median OS was calculated using Kaplan-Meier product limit estimates. Analysis of trial data has occurred at 6 different censoring time points: December 4, 2017; February 28, 2018; October 3, 2018; December 31, 2018; March 8, 2019; and May 20, 2019. Upper and lower limits of the Kaplan-Meier OS estimate were calculated to explore the stability of OS estimates over time (Betensky 2015). Analyses were performed using SAS version 9.4 (SAS Institute). Results: Median OS was not reached until analysis was conducted as of October 3, 2018. At this analysis the median OS (1130 days) exceeded the median follow-up time (867 days). This phenomenon also occurred for data censored on December 31, 2018, with the median OS (1130 days) also exceeding the median follow-up time (956 days). In the most recent two analyses of the data (March 8, 2019 and May 20, 2019), the median OS settled at a consistent value (880 days) that did not exceed the median follow-up times (1023 days and 1096 days, respectively). Exploration of the stability of OS estimates revealed that a single patient enrolled early in the study and died after 1130 days of follow-up skewed the median OS estimate upward. Conclusions: Interest in our clinical trial results motivated numerous follow-up analyses of our data. As such, we encountered a peculiar result in which median OS exceeded median follow-up. In investigating the stability of the OS K-M estimates, a single patient's study data was found to skew results in these instances. Removal of this patient's data in these instances (when the relationship between median follow-up and median OS suggest estimate instability) results in a median OS consistent with subsequent analyses at later censoring dates (880 days for the modified analysis). We therefore conclude that time-to-event estimate stability is informative and should be incorporated into survival analysis of clinical trial data. Disclosures Pollyea: Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Forty-Seven: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Diachii Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Background: Venetoclax (ven) was approved for older untreated acute myeloid leukemia (AML) patients due to high response rates and durable remissions. As a participating site in the dose escalation study, we observed deeper/more durable responses in some who received >400mg ven. We also noted 16/33 discontinued azacitidine (aza) after achieving a response; 9 relapsed and 7 remained in long term remission on ven only. Based on these observations, we designed a study that hypothesized: A)Higher initial doses of ven would allow deeper/more durable responses, and B)Multi modality high sensitivity measurable residual disease (MRD) testing could identify patients able to discontinue aza and remain on maintenance ven. Methods: This is an ongoing phase 2 study (NCT03466294) of 42 untreated AML patients ≥60 who decline/are ineligible for induction. Patients have adequate organ function and white blood cell counts Results: 30 patients enrolled between May 2018 and July 2019; median age is 71 (60-88), 10% evolved from MDS and 10% and 73% had intermediate and unfavorable risk disease by ELN, respectively (Table 1). 732 adverse events (AEs) occurred; 46 (6%) were serious, the most common were neutropenic fever (37%) and pneumonia (13%). The most common >grade 2 related AEs were leukopenia (53%), thrombocytopenia (44%) and neutropenia (35%); there were no related grade 5 AEs. The overall response rate was 70% (21/30; CR=19, MLFS=2). Median number of cycles to achieve best response was 1. Significant blast reductions were seen on day 8; of the 28 with interpretable day 8 BMBXs, 10 achieved MLFS on day 8. 4 completed ≥1 cycle and were refractory. An additional 4 did not complete cycle 1: 1 died of disease and 3 elected to come off therapy (all subsequently died of disease). Four (19%) responders relapsed, after a median 180 days (27-279). With median follow up of 214 days, median response duration has not been reached. 10 patients died, after a median 65 days (29-256); 1/30 died within 30 days. Median overall survival has not been reached. Of the 26 who completed ≥1 cycle, 19 were MRD- by MPFC, including 18/19 who achieved CR. Of these 26, 3 were not monitored by ddPCR: for 2 patients this was due to the absence of detectable baseline mutations and for 1 patient it was due to refractory disease. The remaining 23 had ddPCR monitoring; 3 became MRD- by this modality (Fig 2). All 3 were also MRD- by MPFC and per protocol discontinued aza and initiated ven maintenance (Fig 1). MRD negativity by both parameters occurred after cycles 1, 2 and 3, respectively. One MRD- patient relapsed after 216 days; two remain in remission after 301 and 124 days. An additional 4 who achieved MRD+ responses discontinued aza at their insistence (and in violation of the protocol); 1 relapsed after 279 days, and 3 remain in ongoing remission. Univariate predictors of refractory disease were FAB M0/M1 (OR 0.070, p=0.02) and RAS pathway mutations (OR 14.25, p=0.02). Conclusions: Higher initial doses of ven are tolerated in this population. Blast reduction occurs quickly in many patients (day 8), for this low intensity regimen. Response rates are consistent with lower doses of ven. Very deep responses, as measured by highly sensitive MRD methods (MPFC and ddPCR are capable of sensitivity up to 0.02%), are attainable. Longer follow up time will determine if higher ven doses and MRD-driven decisions related to continuation of aza result in more durable responses. Increased maturation of blasts and RAS pathway mutations are predictors for refractory disease. Disclosures Lyle: Pfizer: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo Incyte: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Pollyea:Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Diachii Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forty-Seven: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Introduction: The prognosis of patients with multiple myeloma (MM) who are resistant to proteasome inhibitors (PIs) and immunomodulatory drugs (IMiDs) is extremely poor. Even daratumumab and BCMA CAR-T cell therapies appear to provide only temporary benefit before patients eventually succumb to their disease. We show that protein translation is upregulated in MM cells. We also demonstrate that translational inhibition with omacetaxine (Oma) is specifically cytotoxic in a manner that is preserved in MM cells from PI/IMiD resistant patients. Furthermore, protein translation inhibition is synergistic with IMiDs, even in IMiD refractory patients. We hypothesize these findings stem from the origin of MM cells as professional antibody secretory cells, with highly active protein translation fundamental to their biology. Here, we show these findings and provide support to test the translation inhibitor omacetaxine with a clinical trial in multiple myeloma patients. Methods: Primary MM cells in mononuclear cell (MNC) cultures were assayed ex vivo for Oma effect at 48-hrs by high-throughput flow cytometry using our myeloma drug sensitivity testing (My-DST) platform. Protein synthesis rates were measured via flow cytometry using the Cayman OP-puromycin assay. Initial drug combination matrices were performed in MM cell lines via MTS assay after 96-hr incubation. Cell line xenograft study of the Oma and IMiD combination in vivo were performed using an orthometastatic MM model with MM1.S luciferase-expressing cells injected IV in NSG mice. Vehicle control, Oma, pomalidomide (Pom) and the combination were dosed 5 days/week by IP injection beginning on day 30. Disease burden was monitored with imaging of luciferase bioluminescence. Results: Oma had specific cytotoxicity across 5 MM cell lines (EC50 = 15-35 nM, data not shown). Oma also showed MM cell specific cytotoxicity in patient samples with EC50 ranging from 25-100 nM (Fig 1A). Ex vivo treatment with 50 nM Oma for 48 hrs caused >50% reduction in viable MM cells in 39/50 (78%) patient samples. Importantly, 50 nM Oma retained activity in PI/IMiD-refractory patients compared to sensitive patients (64.2% vs 71.6% mean decrease in MM cell viability, respectively, P = 0.44, Fig 1B). Primary MM cells exhibited significantly higher levels of baseline protein translation than other bone marrow MNCs with mean 3.9-fold increase (n = 14, P = Conclusion: Protein translation inhibitors represent a potential new drug class for clinical myeloma treatment. We have shown that the protein synthesis inhibitor omacetaxine possesses a potent and specific killing effect against MM cells. Importantly, this anti-myeloma cytotoxicity was equally active in biopsy samples obtained from patients at diagnosis and patients with disease advanced to the late stage of PI/IMiD resistance. The pretreatment level of MM cell protein translation may serve as a biomarker for clinical response. In further exploration of the optimized treatment approach for clinical trials, we found synergy between omacetaxine and pomalidomide in vitro, in vivo and using patient samples ex vivo. A phase I clinical trial of omacetaxine single agent and in combination with pomalidomide is currently in development at the University of Colorado. Disclosures Mark: Janssen: Honoraria; Takeda: Honoraria; Amgen: Honoraria; Celgene: Honoraria.

Background: Data suggests that the presence of measurable residual disease (MRD) at the time of transplant for AML portends a poor prognosis. The timing of MRD assessment and transplant relative to the amount of pre-transplant therapy, however, may affect this prognosis. To examine further the question of optimal timing of transplant in the setting of MRD, we reviewed outcomes in AML patients treated with traditional cytotoxic induction at our center who achieved CR1 and proceeded to transplant. Methods: We analyzed outcomes in patients undergoing first transplant for AML in CR1 between January 2014 and March 2018. CR was defined according to 2017 European Leukemia Network (ELN) guidelines. Non-core binding factor patients were included if they underwent initial therapy with 7+3 chemotherapy (+/- adjunctive inhibitor during induction or as post-transplant maintenance). MRD testing modalities included cytogenetics/FISH (performed in 37 patients, positive in 10), flow cytometry performed by Hematologics Inc (performed in 49 patients, positive in 16), and/or mutation specific droplet digital PCR (ddPCR) performed at our center (performed in 33 patients, positive in 16). For three patients, other molecular methods demonstrated MRD. We compared outcomes in three groups: patients who underwent transplant in CR1 with positive MRD after induction only (MRD positive induction only) (n=15), patients who underwent transplant in CR1 with positive MRD after induction and additional therapy (MRD positive induction plus) (n=19), and patients undergoing transplant in CR1 with no MRD (MRD negative) (n=37). Patient details are summarized in Table 1. Results: CI of relapse was higher among MRD positive induction plus patients than MRD positive induction only patients (p=0.042, HR 0.301 (0.094-0.96)) and comparable among MRD positive induction only patients and MRD negative patients (p=0.987, HR 1.011 (0.29-3.58)). CI of transplant related mortality (TRM) was comparable between MRD positive induction plus patients and MRD positive induction only patients (p=0.165, HR 0.23 (95% CI 0.028-1.81)) and comparable among MRD positive induction only patients and MRD negative patients (p=0.871, HR 1.22 (95% CI 0.12-12.87)). Relapse free survival (RFS) and overall survival (OS) were comparable between MRD positive induction only patients and MRD negative patients and significantly better than for MRD positive induction plus patients (RFS (p Because multiple strategies were used to assess for MRD, we compared MRD positive induction only to MRD positive induction plus patients using flow cytometry performed by Hematologics Inc as the only MRD assessment technique. CI of relapse trended toward lower in the MRD positive induction only group (p=0.10, HR 0.22, (95% CI 0.036-1.34). OS and RFS were significantly improved in the MRD positive induction only patients (p=0.027 and p=0.026 respectively). Conclusions: For patients achieving CR following induction and moving directly to transplant in spite of MRD positivity, outcomes were comparable to patients going to transplant in an MRD negative state and were significantly improved compared to outcomes of patients in an MRD positive state who received additional therapy following induction. Our series is small, and multiple MRD monitoring strategies were used. However, given the paucity of data on this specific question, uncertainty about whether MRD will clear with additional cytotoxic therapy following induction, and the poor prognosis of patients with persistent MRD in the induction plus group, we consider transplant following induction reasonable in this population regardless of MRD status. Larger series are necessary to more definitively answer this question. Disclosures Loken: Hematologics, Inc: Employment, Equity Ownership. Pollyea:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Diachii Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forty-Seven: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Recent clinical trials have reported that in combination with hypomethylating agents, the BCL-2 inhibitor venetoclax can induce responses in over 70% of older previously untreated AML patients who are unfit for conventional chemotherapy. These findings led to the recent United States Food and Drug Administration approval of this regimen for this population, and it is now considered to be the standard care. However, a significant minority of patients do not achieve a remission and are refractory. In addition, the majority of patients who do achieve a remission ultimately relapse. It is therefore critical to identify AML patients who are likely to be resistant to venetoclax-based therapy. To initially address this question, we retrospectively reviewed 75 newly diagnosed AML patients who received venetoclax + azacitidine (VEN+AZA) at our institution and analyzed several baseline clinical features to determine the ability of each to predict disease that was refractory to treatment (defined as a lack of complete remission [CR], CR with incomplete recovery of peripheral blood counts [CRi], partial remission, or morphological leukemia free state [MLFS]). Both univariate and multivariate analyses revealed the presence of FAB-M5 to be associated with disease that was refractory to VEN+AZA (Table 1). Given that FAB-M5 represents AML with monocytic differentiation, these findings indicate a strong correlation between myeloid differentiation status and resistance to venetoclax. Using multicolor flow cytometry, we show bone marrow specimens of typical FAB-M5 patients who were refractory to VEN+AZA presented dominant monocytic disease that has an immunophenotype of CD45-bright/SSC-high/CD117-/CD11b+/CD68+ (Figure A). In contrast, bone marrow specimens of typical FAB-M0/M1/M2 patients who achieved CR with VEN+AZA presented as a single dominant disease population that is CD45-med/SSC-low/CD117+/CD11b-/CD68- (Figure B). In a subset of AML patients, we observed the co-existence of both phenotypically primitive and monocytic populations, which we term "MPM" AML (for Mixed Primitive/Monocytic). We observe that after attaining CR with VEN+AZA treatment and subsequent relapse, MPM-AML showed almost complete loss of the primitive subpopulation, and evolved to a dominant monocytic disease (Figure C). These data indicate that VEN+AZA treatment induces strong selection of the monocytic phenotype. Importantly, when we compared the immunophenotype of six pairs of diagnostic/relapse specimens from AML patients treated with conventional intensive induction chemotherapy, we observed selection of a more primitive phenotype, suggesting the drive toward a monocytic phenotype observed at relapse appears to be a unique consequence of VEN+AZA therapy. To our knowledge, selection of a monocytic phenotype at relapse has never been previously observed in AML, suggesting the relapse after VEN+AZA may represent a new clinical entity. Mechanistically, using RNA-seq we show the global transcriptome of monocytic AMLs are distinct from primitive AMLs, suggesting they represent two broad classes of AML with likely differential responses to therapy. Indeed, we demonstrate that AML with a primitive immunophenotype is dependent on BCL-2 activity as a means to drive oxidative phosphorylation, a critical requirement for survival of leukemia stem cells. Conversely, AML with a more differentiated monocytic phenotype is no longer dependent on BCL-2, but rather switches to MCL-1 as a mediator of oxidative phosphorylation. Using colony-forming and xenograft assays, we show the stem and progenitor potential of monocytic AMLs are selectively more sensitive to MCL-1 inhibition comparing to BCL-2 inhibition. Together, our study suggests a significantly higher refractory/relapse risk for monocytic AML patients treated with VEN+AZA (Figure D). Further, for those AML patients who do respond to initial VEN+AZA treatment, the therapy drives a powerful selective process resulting in emergence of more differentiated monocytic disease in some patients. Based on these findings, we propose that AML exists on a developmental spectrum that is inherently fluid, where with appropriate selective pressure the disease can acquire characteristics of a more differentiated state. Further, our data indicate that optimal AML therapy will require strategies designed to target both primitive and myeloid phenotypes. Disclosures Pollyea: Forty-Seven: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Diachii Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Savona:TG Therapeutics: 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; Selvita: Membership on an entity's Board of Directors or advisory committees; Karyopharm Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sunesis: Research Funding; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Patents & Royalties; AbbVie: Membership on an entity's Board of Directors or advisory committees.

Effective targeting of the acute myeloid leukemia (AML) leukemia stem cell (LSC) population may allow for deep, durable remissions and curative potential. In older, newly diagnosed AML patients who are not candidates for induction, venetoclax + azacitidine (aza) targets specific metabolic vulnerabilities of LSCs, resulting in very promising clinical outcomes. In our single institution experience treating 45 previously untreated AML patients with venetoclax + aza both in the context of the multi-institutional study NCT02203773 (N=33) and with off-label use (N=12), 36/45 (80%) achieved a complete remission (CR) or CR with incomplete count recovery (CRi). In the relapsed/refractory (R/R) setting, the efficacy of venetoclax + aza has been reported to be significantly worse. In our single-institution off-label experience (N=7), only 1/7 (14%) R/R patients had a CR/CRi (p=0.005 compared to the untreated group). R/R and untreated patients had similar baseline characteristics, although more R/R patients had an antecedent hematological disorder (Table 1). Multivariate analysis showed cytogenetic risk and R/R disease as the sole predictors of response to venetoclax + aza (Table 2). In light of existing data regarding biological changes that occur in LSCs after treatment and subsequent relapse, we aimed to determine whether laboratory analysis of LSCs from patients treated with venetoclax + aza would show differential sensitivity to this therapy in the up-front vs R/R setting that could help to explain the different clinical activity. We have previously shown that LSCs from untreated patients are uniquely reliant on oxidative phosphorylation (OXPHOS), and that venetoclax + aza targets LSCs by decreasing OXPHOS. Therefore, we tested the hypothesis that inferior responses of R/R patients to venetoclax + aza are due to changes in OXPHOS regulation in relapsed LSCs. LSCs were defined as cells bearing relatively low levels of reactive oxygen species (ROS-low), an effective means of enriching primary human LSCs. We found that in contrast with untreated patients, venetoclax + aza does not decrease viability or OXPHOS in LSCs from R/R patients (Fig1). Furthermore, R/R LSCs had altered fatty acid metabolism that contributed to these OXPHOS differences, with increased flux of fatty acids into the TCA cycle (Fig 2). In addition, R/R samples compensated for the metabolic perturbations that occurred upon exposure to venetoclax + aza through upregulation of fatty acid uptake and metabolism into the TCA cycle (Fig 3). Fatty acid metabolism is controlled by multiple genes and pathways. Integral to its activity is the gene Carnitine Palmitolytransferase 1 (CPT1), due to its pivotal role in the beta-oxidation of long chain fatty acids. Investigation of the Cancer Genome Atlas AML dataset reveals higher expression of CPT1 leads to significantly worse overall survival, suggesting increased fatty acid metabolism may drive a more resistant LSC population in R/R AML patients. We also found elevated baseline levels of CPT1 in patients who progressed on venetoclax + aza compared to those that had long term remissions (not shown). Therefore we utilized the CPT1 inhibitor etomoxir to block fatty acid metabolism. We found addition of etomoxir to cultures of R/R LSCs rescued the ability of venetoclax + aza to decrease OXPHOS and re-sensitized R/R LSCs to venetoclax + aza (Fig 4). To prove that this novel regimen targets functionally-defined R/R LSCs we performed ex vivo treatment followed by xenotransplantation of R/R patient specimens, which showed that upon etomoxir addition, engraftment potential is significantly decreased over venetoclax + aza alone (not shown). Therefore we propose a novel mechanism for the increased resistance of R/R AML patients to venetoclax + aza involving altered energy metabolism. We find increased fatty acid metabolism in R/R patient specimens, and targeting this pathway using the CPT1 inhibitor etomoxir leads to sensitization to venetoclax + aza and rescued targeting of OXPHOS, allowing for LSC eradication. Disclosures Pollyea: Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Argenx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Research Funding; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Curis: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees.