ALBERT

Description: Despite recent advancements, approximately 50% of patients with acute myeloid leukemia (AML) do not respond to induction therapy (primary induction failure, PIF) or relapse after

Description: Introduction: MDS encompasses a heterogeneous group of clonal neoplastic hematopoietic stem cell diseases characterized by ineffective hematopoiesis and frequent progression to acute myeloid leukemia (AML). While the advent of hypomethylating agent (HMA) therapy has modestly improved survival in higher-risk MDS, outcomes following HMA failure are dismal. The hedgehog (HH) signaling pathway is an important regulator of hematopoietic cell survival and differentiation, with upregulation of HH target genes and signaling proteins a frequent occurrence in MDS and AML. PF-04449913 (PF-04) is an orally bioavailable inhibitor of Smoothened (SMO), which demonstrated antileukemic activity in a prior phase 1 study. We performed a phase 2 study of PF-004449913 in patients with MDS following HMA failure. Objectives: 1) primary: to estimate overall IWG-2006 response rate (CR + PR + HI + marrow CR) to PF-04449913 in patients with relapsed/refractory MDS and CMML; 2) secondary: to assess safety , overall survival, time to AML transformation, and effect of PF-04 on HH target gene expression. Methods: This was a single center, open-label phase 2 study. Key eligibility criteria included: 1) patients age ≥ 18 with MDS, CMML, or AML (20-29% blasts) following failure of HMA; 2) ECOG 0-2; 3) Adequate kidney and hepatic function. Treatment consisted of PF-04 at 100 mg/day in 4-week cycles for 4 cycles, with continuation allowed for achievement of stable disease or better. Dose increase to 200 mg/day was permitted after cycle 2 for patients with stable disease. Bone marrow biopsy for response assessment occurred after cycle 2, cycle 4, and every 4th cycle thereafter. For correlative studies, total cellular RNA was isolated from ficolled mononuclear cells in baseline marrow samples, and qPCR performed for expression of GLI1, PTCH1, and SMO). Results: Thirty five patients were enrolled, 24M and 11F. Median age was 75 years (range 55-88). A majority of patients had higher-risk (54%) vs lower-risk (43%) MDS by IPSS at time of enrollment. A total of thirty four patients (97%) had received prior azacitidine for a median of 9 cycles (range 1-88), while 6 patients had received decitabine for a median of 4 cycles (5 of whom had also received azacitidine). The median number of cycles of PF-04 received was 3 (range 1-11). All 35 patients were evaluable for response. Two of 35 patients (6%) achieved response per MDS IWG 2006 criteria, including one patient with HI-N/HI-P and another with marrow CR and HI-N. Nineteen additional patients (54%) had stable disease following cycle 2 (8 weeks). With a median follow-up of 10.1 months, the median survival for all treated patients was 10.2 months (95% CI 6.8-13.6 mo)(Figure 1). Median survival for patients with low/INT-1 risk MDS was longer than for INT-2/high risk patients (22.4 mo vs 7.5 mo, p=0.013). Six patients (17%) died while on-treatment, but none of the deaths were considered related to PF-04. The most common treatment-emergent adverse events included myalgia/muscle cramps (65%), dysgeusia (60%), nausea (31%), anorexia (31%), oral mucositis (25%), and AST elevation (22%). The vast majority of these events were grade 1/2. Except for infection (11%), there were no treatment-emergent grade 3/4 events in 〉 10% of patients. Only 5 patients (14%) required dose reduction to 50 mg/day due to intolerance. In the pharmacodynamics analysis, responding patients had higher baseline expression of SMO, PTC ,and GLI1 than non-responders, while non-responders had higher post-treatment increases in these transcripts compared with responders. Conclusions: PF-04 was well tolerated in patients with advanced, HMA refractory MDS, but had limited efficacy in this unselected, heavily pre-treated patient population. The pharmacodynamic analysis suggests predictive potential of HH pathway gene expression for response warranting further investigation. Figure 1 Figure 1. Disclosures Komrokji: Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Speakers Bureau; Incyte: Consultancy. Sweet:Novartis: Consultancy, Speakers Bureau; Ariad: Consultancy, Speakers Bureau; Pfizer: Speakers Bureau; Incyte Corporation: Research Funding; Karyopharm: Honoraria, Research Funding.

Description: Background: Runt-related transcription factor 1 (RUNX1) is a key regulator of hematopoiesis, and aberrant expression of this gene can facilitate leukemogenesis. RUNX1 mutations (RUNX1mut) are thought to carry a poor prognosis and have been recently incorporated into the risk stratification systems for acute myeloid leukemia (AML) by European LeukemiaNet (ELN) (Dohner et al. 2017) and National Comprehensive Cancer Network (NCCN et al. 2019). However, the clinical significance of this mutation after allogeneic stem cell transplantation (allo-SCT) is controversial with a recent study suggesting that allo-SCT may reverse the unfavorable influence of RUNX1mut(Qin et al. 2017). In this study, we describe the prognostic impact of RUNX1mutin patients with AML undergoing allo-SCT and compare the outcomes to ELN-defined adverse risk, RUNX1wtAML patients and patients with intermediate risk AML. Methods: We retrospectively reviewed our database of 407 patients who received allo-SCT at the Moffitt Cancer Center between 2013 and 2018. Only AML patients undergoing allo-SCT during first complete remission that had molecular information prior to transplant were included. This cohort was divided into three subgroups: 1) RUNX1mutAML 2) ELN-defined adverse risk, RUNX1wtAML and 3) ELN-defined intermediate risk AML. We utilized clinical data captured by BMT Research and Analysis Information Network (BRAIN). Univariate and multivariate analyses were conducted using log-rank and Cox regression, respectively. Cumulative incidence function was performed as defined by the Fine and Gray model. Kaplan-Meier analysis with log-rank test was used to estimate median overall survival (mOS) from the time of diagnosis. Results: Among 407 AML patients reviewed, we identified 28 patients with RUNX1mut, 71 adverse risk RUNX1wtpatients, and 69 intermediate risk patients. Of the 28 patients (18 males/10 females) with RUNX1mut, 53.6% were under age 60, two-thirds had de novo AML (dAML), and 92.9% had intermediate risk cytogenetics as defined by ELN 2017 at diagnosis. Baseline characteristics are described in Table 1. Univariate analysis identified RUNX1mutto be predictive of inferior OS compared to the intermediate risk cohort (HR 2.29, 95% CI 1.12-4.64, p=0.022). Subsequent multivariate regression using covariates of age, sex, AML type, lines of therapy prior to allo-SCT, and conditioning regimen confirmed RUNX1mutas an independent covariate for reduced OS (HR 2.51, 95% CI: 1.18-5.33, p=0.016). At a median follow-up of 29.3 months for the entire cohort, Kaplan-Meier analysis confirmed an inferior mOS in patients with RUNX1mutcompared to the intermediate risk group (25.7 months vs. 59.8 months, p=0.029) and was not different from RUNX1wtadverse risk group (25.7 months vs. 45.7 months, p=0.872) (Figure 1A). Cumulative incidence of relapse after allo-SCT for patients with RUNX1mutis significantly higher than intermediate risk patients (p=0.005, Figure 1B); however, there was no difference compared to RUNXwtadverse risk AML (p=0.295). There was no difference in non-relapse mortality (NRM) between RUNX1mutand intermediate risk patients (p=0.789, Figure 1B) or RUNX1mutand RUNX1wtadverse risk AML (p=0.323). When impact of concomitant somatic mutations on disease recurrence in RUNX1mutcohort was assessed, no discernible trends were identified. RUNX1mutwas mutually exclusive with NPM1 and frequently co-occurred with DNMT3A (21.4%), IDH2 (17.9%), and SRSF2 (17.9%) (Figure 2). Interestingly, 92.9% of the patients with RUNX1muthad ELN-defined intermediate risk cytogenetics and only 7.1% of the cohort had ELN-defined adverse risk cytogenetics. Conclusions: Our findings indicate that allo-SCT AML patients with RUNX1muthave poor outcomes analogous to RUNX1wtadverse risk AML. Disclosures Talati: Jazz Pharmaceuticals: Honoraria, Speakers Bureau; Pfizer: Honoraria; Astellas: Honoraria, Speakers Bureau; Celgene: Honoraria; Daiichi-Sankyo: Honoraria; Agios: Honoraria. Kuykendall:Incyte: Honoraria, Speakers Bureau; Janssen: Consultancy; Abbvie: Honoraria; Celgene: Honoraria. Sallman:Celyad: Membership on an entity's Board of Directors or advisory committees. Komrokji:Novartis: Speakers Bureau; Agios: Consultancy; Incyte: Consultancy; JAZZ: Speakers Bureau; JAZZ: Consultancy; celgene: Consultancy; pfizer: Consultancy; DSI: Consultancy. List:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Lancet:Pfizer: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Other: fees for non-CME/CE services ; Agios, Biopath, Biosight, Boehringer Inglheim, Celator, Celgene, Janssen, Jazz Pharmaceuticals, Karyopharm, Novartis: Consultancy. Sweet:Astellas: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Celgene: Speakers Bureau; Incyte: Research Funding; Stemline: Consultancy; Agios: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Jazz: Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Description: Background Hypomethylating agent (HMA) therapy represents the standard of care for patients with higher risk myelodysplastic syndromes (MDS) although only 50% of patients respond to treatment. Recent evidence from molecular profiling through next-generation sequencing (NGS) in myeloid diseases has been conflicting as to the value of somatic mutations as a biomarker for response to HMA. In particular, there have been conflicting data on response rates and outcomes in TP53 mutant (MT) MDS and acute myeloid leukemia (AML) based on azacitidine versus decitabine (Welch et al., NEJM 2016; Garcia-Manero et al., NEJM 2017). However, the TP53 mutant cohorts in these studies were small (median 23 patients, range 13-39) and heterogeneous based on treatment status (treatment naïve versus relapse/refractory). Therefore, our goal was to characterize outcomes of TP53 mutant MDS patients who received frontline HMA therapy. Patients and Methods TP53 MT MDS and oligoblastic AML (20-30% blasts) cases were retrospectively identified from the Moffitt Cancer Center MDS database. All patients had NGS of TP53 and up to 53 additional genes performed prior to the initiation of HMA. The lower limit of VAF detection was set at 5% and the minimum depth of coverage at each position was 500X. Clinical variables and outcomes of MDS patients were characterized at the time of sample procurement. Fisher's exact tests were used for comparative analyses. Kaplan-Meier curves were used to estimate overall survival (OS) and analyzed from the date of HMA initiation. Response rates and outcomes of TP53 MT patients were compared to a cohort of wildtype (WT) patients (n=63). Results From May 2013 to May 2018, a total of 71 patients with TP53 mutant MDS were identified with a median age of 68 years (39-82) and male predominance (66%). Fourteen patients (20%) had multiple mutations in TP53. Of the cohort, 82% of patients (n=58) were treated with azacitidine (88% (n=51) with AZA monotherapy; 12% (n=7) with AZA in combination (2 pts with lenalidomide and 5 pts with investigational agents)) with 18% (n=13) receiving decitabine. The median # of HMA cycles was 4 (range 1-33). Thirteen pts (18%) proceeded to allogeneic hematopoietic stem cell transplant (HSCT). Of the cohort, 18% (n=13) obtained complete remission (CR) with 39% (n=28) overall response rate (ORR). There was no difference in CR or ORR in pts treated with AZA vs DAC (P=0.24 and P=0.2, respectively). At a median follow up 20 months, the median OS of the entire cohort was 9.7 months. There was no difference in median OS between AZA vs AZA combo vs DAC (7.6 vs 15.2 vs 12.5 months; P = 0.44; Figure 1A). TP53 variant allele frequency (VAF 〉 20% vs ≤ 20%) was not predictive of outcomes to HMA (7.8 vs 10.4 months, P = 0.36). However, TP53 MT patients who had clonal response to HMA (i.e. VAF 〈 5%; n=19 (27%)) had improved OS (14.5 vs 7.5 months; HR 0.33, 95% CI 0.18 to 0.59; P = 0.001; Figure 1B). In multivariable analysis incorporating age, revised international prognostic scoring system (IPSS-R) category, HSCT status, or type of HMA, TP53 clonal clearance remained an independent covariate for improved OS (HR 0.34, 95% CI 0.16 to 0.72; P = 0.005). Pts who underwent HSCT (n=13) had a trend for improved OS (14.5 months vs 7.9 months; P = 0.09). Notably in transplanted pts who had serial TP53 NGS (n=7), pts who achieved a VAF 〈 5% had significant improved OS (16.3 months vs 8.9 months; P=0.03). Compared to higher risk MDS/AML TP53 WT patients treated with HMA, there was no difference in CR (18% vs 14% (P = 0.64) or ORR rates (39% vs 40%). In contrast, TP53 MT patients had significantly inferior OS with HMA therapy (9.7 vs 15.4 months; HR 2.14, 95% CI 1.32. to 3.27; P = 0.001; Figure 1C). Conclusion In this large cohort of higher risk MDS and oligoblastic AML pts who received frontline HMA therapy, TP53 MT patients have significantly inferior OS with no significant differences in response rates or outcomes by HMA. TP53 MT patients who achieve maximum clonal suppression with HMA treatment (i.e. VAF 〈 5%) have improved OS as well as improved outcome with HSCT. Novel therapy targeting TP53 mutation is needed to improve outcomes. Figure 1. Figure 1. Disclosures Sallman: Celgene: Research Funding, Speakers Bureau. Sweet:Agios: Consultancy; Jazz: Speakers Bureau; Astellas: Consultancy; Phizer: Consultancy; Phizer: Consultancy; Astellas: Consultancy; Jazz: Speakers Bureau; Celgene: Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Agios: Consultancy; BMS: Honoraria; Celgene: Honoraria, Speakers Bureau; BMS: Honoraria. List:Celgene: Research Funding. Komrokji:Novartis: Honoraria, Speakers Bureau; Celgene: Honoraria, Research Funding; Novartis: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Celgene: Honoraria, Research Funding; Novartis: Honoraria, Speakers Bureau.

Description: Background: Patients (pts) with secondary acute myeloid leukemia (s-AML) have poor long-term outcomes following standard induction chemotherapy with 7+3. Last year, a liposomal cytarabine and daunorubicin formulation (CPX-351) was FDA approved for upfront treatment of s-AML based on a pivotal phase 3 trial demonstrating improved overall survival in pts aged 60-75 years old (Lancet J et al; JCO 2018). Although CPX-351 treatment is indicated in all adults with s-AML, it is unclear whether CPX-351 is safe and effective in younger pts 〈 60 years. We sought to address this unanswered question by retrospective review of clinical experience since FDA approval at 4 large academic centers. Methods: Medical records were retrospectively reviewed at Roswell Park Comprehensive Cancer Center, Moffitt Cancer Center, University of Alabama Comprehensive Cancer Center, and Levine Cancer Institute to identify pts aged 18-59 years old with untreated s-AML defined as antecedent MDS or CMML, prior cytotoxic therapy, or AML with WHO defined myelodysplasia related changes (AML-MRC) treated with CPX-351 as induction therapy. Demographics, disease-specific variables, as well as overall outcomes were collected in accordance with the institutional review board approved protocol. Responses were defined according to the 2003 International Working Group (IWG) criteria. Demographics, baseline clinical characteristics, treatment response, and adverse events were analyzed using descriptive statistics. Overall survival was estimated utilizing Kaplan-Meier (KM) analysis. Results: Twenty-one pts with confirmed s-AML received CPX-351 therapy. Mean age was 54 years (range 42 - 59), 13 were male (62%). The majority (62%, N=13) had AML-MRC, 4 (19%) had treatment-related AML (t-AML) and 4 (19%) had MDS-MRC. Four of 5 pts had received prior hypomethylating therapy. Fourteen pts had a complex karyotype (67%), and 4 patients were found to have a normal karyotype (12%). The most common molecular event was TP53 mutation seen in 9 pts (43%), followed by FLT3-ITD identified in 3 pts (14%). At the time of analysis, response assessments were available for 16 pts. Overall response rate (CR/CRi/PR) was 25% with 1 CR (6.25%, 1/16), 1 CRi (6.25%, 1/16), and 2 PR (13%, 2/16). The remaining pts (12/16, 75%) were non-responders (Table 1). One pt has received an allogenic stem cell transplant. The most common adverse event was infection (81%, 17/21) with 3 clinically significant bleeding events. Thirty-day mortality was 14.3%, with 60-day mortality of 19.1%. Overall survival in all evaluable pts (N=21) was 7.1 months (range 0.5 - 7.4 months) (Figure 1), with mean follow up of 14.8 weeks. Conclusions: This multi-institutional retrospective analysis suggests that CPX-351 results in lower response rates (CR/CRi 12.5%) and shorter overall survival (7.1 mos) than reported in the recently published phase 3 trial data in pts aged 60-75 years old (Table 1). Potential explanations for this discrepancy include short follow up, small sample size, the retrospective design of this study, and the significant proportions of pts with complex karyotype and TP53 mutations. Historically, patients 〈 65 years old with s-AML have had a reported overall survival of approximately 7 months. Further investigation of this regimen in younger pts with s-AML as compared with 7+3 and other approaches is warranted. Disclosures Thota: Incyte: Speakers Bureau. Baron:Pfizer Pharmaceuticals: Other: Previously served as a consult on the Advisory Boards (May 2017).. Griffiths:Alexion Inc.: Honoraria, Research Funding; Novartis, Inc.: Research Funding; Astex/Otsuka Pharmaceuticals: Honoraria, Research Funding; Pfizer, Inc.: Research Funding; Celgene, Inc: Honoraria, Research Funding. Sweet:Jazz Pharmaceuticals: Honoraria, Speakers Bureau; Bristol Myers Squibb: Honoraria; Incyte: Research Funding; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Speakers Bureau; Agios: Consultancy; Celgene: Speakers Bureau. Wang:Jazz: Speakers Bureau; Jazz: Speakers Bureau; Pfizer: 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; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy; Novartis: Speakers Bureau; Novartis: Speakers Bureau; Amgen: Consultancy; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Description: Background: CPX-351 (Vyxeos) is a liposomal combination of daunorubicin and cytarabine that was FDA approved in 2017 for treatment of adults with newly diagnosed therapy-related acute myeloid leukemia (t-AML) or AML with myelodysplasia-related changes (AML-MRC). Genomic predictors of response to CPX-351 have not been described. TP53 mutations are uncommon in de novo AML, but relatively enriched in the t-AML and AML-MRC populations for which CPX-351 is approved (Christiansen DH et al. JCO 2001; Devillier R et al. Oncotarget 2015). As TP53 mutations confer resistance to conventional daunorubicin and cytarabine chemotherapy, we sought to determine whether TP53 mutations confer resistance to CPX-351. Methods: This is a retrospective, multi-center review of patients who received at least 1 cycle of induction chemotherapy with CPX-351 at Memorial Sloan Kettering Cancer Center (MSKCC), Moffitt Cancer Center (MCC), and Weill Cornell Medical College (WCMC). 101 patients were identified at MSKCC (n=22), MCC (n=44), and WCMC (n=35). Responses to CPX-351 were graded using European Leukemia Net (ELN) response criteria. (Döhner H et al Blood 2017) Immunophenotypic minimal residual disease (MRD) was identified in bone marrow aspirates (BMA) by multiparameter flow cytometry in 43 patients (MSKCC n=22, WCMC n=21). Any level of residual disease was considered MRD+. Molecular analysis was obtained from pre-induction BMA by next-generation sequencing using 21, 32, 49, or 400 gene panels, all of which included TP53. Cytogenetics/FISH were performed using standard techniques. Fisher's exact tests were used to determine significance and are two-tailed. Kaplan-Meier (KM) analysis with log-rank test was performed to estimate overall survival (OS). Results: Patient characteristics are in Table 1. 84/101 (83.1%) had baseline molecular profiling prior to CPX-351. TP53 mutations were identified in 18/84 (21.4% of patients). Analysis of additional co-mutations and responses will be presented by our collaborators (Talati et al., ASH 2018 submitted). TP53 mutations (19/20 distinct mutations) clustered in the DNA binding domain (Figure 1A). TP53 mutations are significantly associated with complex or monosomal karyotypes (p

Description: Background: In recent years, genomic studies have uncovered a number of driver gene mutations in acute myeloid leukemia (AML). There is great interest in leveraging residual disease detection methods including next-generation sequencing (NGS) to predict outcomes, especially in the setting of allogeneic hematopoietic cell transplantation (HCT). One study showed measurable minimal residual disease (MRD) at the time of HCT increases the risk of relapse in patients who received a reduced-intensity conditioning (RIC) regimen (Hourigan et al. 2019). In this study, we evaluate the prognostic impact of somatic mutation clearance using NGS prior to HCT in patients with AML. Methods: We identified a total of 139 patients with AML who underwent HCT at the Moffitt Cancer Center (2013-2018). Using European LeukemiaNet (ELN) criteria, patients were included if at the time of HCT they were adverse risk in complete remission (CR)1, intermediate risk in CR1, favorable risk in CR1 if indication for transplant present, or favorable risk in CR2 with at least one time point when NGS was performed before and after HCT. We utilized clinical data captured by BMT Research and Analysis Information Network (BRAIN). Molecular testing via NGS included 54-gene TruSight Myeloid panel tested on Illumina sequencers with a lower limit of detection of 5%. Positive persistent detectable disease (PDD) was defined as presence of detectable mutations on NGS at HCT. Univariate and multivariate analyses were conducted using log-rank and Cox regression, respectively. Kaplan-Meier analysis was used to estimate overall survival (OS) and relapse free survival (RFS) from the time of diagnosis. Cumulative incidence of relapse (CIR) and non-relapse mortality (NRM) were calculated by the Fine and Gray model. Results: Of the 139 patients (74 males/65 females), 59% were PDD positive at HCT and 41% PDD negative at HCT. Median age at HCT was 59 years. More patients were in ELN-defined adverse risk (46.8%) in comparison to intermediate risk (35.3%) or favorable risk (18%). In both cohorts, majority of the patients had 1 line of therapy prior to HCT. Overall, 57.6% of patients received myeloablative conditioning regimen (MAC) with the remaining receiving RIC. More patients received MAC in both PDD positive at HCT and PPD negative at HCT groups (Table 1). There were 35 patients (25.2%) who relapsed after HCT, and 17 had NGS available at diagnosis, at the time of HCT, and at relapse. The mutation frequencies and changes over time are shown in Figure 1. Univariate analysis showed inferior OS in patients who are PDD positive at HCT compared to PDD negative at HCT (HR 1.98, 95% CI 1.06-3.72, p=0.032). After adjusting for ELN risk and PDD status, the patients who received more than 1 line of therapy prior to HCT had significantly worse OS (p=0.005). Patients with negative PDD at HCT had a significantly better OS at 2-year compared to PDD positive at HCT patients, 78.7% vs. 62.4% (p=0.029) with a median follow up of 29.9 months (Figure 2A). The RFS at 2-year were 72.6% for PDD negative at HCT patients and 51.8% for PDD positive at HCT patients (p=0.090). There was no difference in NRM or CIR between these two groups (p=0.605 and p=0.136, respectively). Further subgroup analysis did not find a significant difference between PDD status and different types of conditioning regimen (Figure 2B). Conclusions: In this study, we report that clearance of somatic gene mutations in AML patients prior to HCT confers better outcomes compared to those with measurable PDD at HCT. There is a survival advantage in patients who received fewer lines of treatment prior to HCT. Larger cohort and greater depth of NGS coverage is needed to better clarify the impact of conditioning regimen in this population. Disclosures Talati: Jazz Pharmaceuticals: Honoraria, Speakers Bureau; Daiichi-Sankyo: Honoraria; Astellas: Honoraria, Speakers Bureau; Pfizer: Honoraria; Celgene: Honoraria; Agios: Honoraria. Bejanyan:Kiadis Pharma: Other: advisory board. Komrokji:JAZZ: Consultancy; Agios: Consultancy; Incyte: Consultancy; DSI: Consultancy; pfizer: Consultancy; celgene: Consultancy; Novartis: Speakers Bureau; JAZZ: Speakers Bureau. Kuykendall:Janssen: Consultancy; Incyte: Honoraria, Speakers Bureau; Abbvie: Honoraria; Celgene: Honoraria. Lancet:Daiichi Sankyo: Consultancy, Other: fees for non-CME/CE services ; Agios, Biopath, Biosight, Boehringer Inglheim, Celator, Celgene, Janssen, Jazz Pharmaceuticals, Karyopharm, Novartis: Consultancy; Pfizer: Consultancy, Research Funding. List:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Nishihori:Novartis: Research Funding; Karyopharm: Research Funding. Sallman:Abbvie: Speakers Bureau; Novartis: Speakers Bureau; Jazz: Research Funding; Incyte: Speakers Bureau; Celyad: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding, Speakers Bureau. Sweet:Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Celgene: Speakers Bureau; Pfizer: Consultancy; Incyte: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Agios: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Stemline: Consultancy; Jazz: Speakers Bureau.

Description: Background: SL-401 is a novel targeted therapy directed to the interleukin-3 receptor (CD123), a target overexpressed on acute myeloid leukemia (AML) blasts and AML cancer stem cells (CSCs), and a variety of additional hematologic malignancies. While conventional chemotherapy can induce remission in a majority of treatment-naive AML patients, relapse rates remain high. Outcomes are particularly poor when minimal residual disease (MRD), as determined by genetic and/or flow cytometric analyses, remains after therapy, with high rates of relapse and short disease-free survival. Conceivably, a therapy directed at lowering MRD burden may improve long-term outcomes. Given the association of MRD with CD123+ AML CSCs, SL-401 is being evaluated in patients with AML in first or second complete remission (CR1 or CR2, respectively) with high risk of relapse including persistent MRD. Preliminary results are reported here. Methods & Results: This multicenter, single-arm Phase 2 trial of AML patients in CR1 or CR2 with high risk of relapse includes a lead-in (stage 1) and expansion (stage 2). In stage 1, patients (MRD+ or MRD-) receive SL-401 as a daily IV infusion at 7, 9, or 12 ug/kg/day for days 1- 5 of a 28 day cycle in a 3x3 design. In stage 2, patients (MRD+ only) receive SL-401 at the dose determined in stage 1. Presence of MRD for eligibility requires either molecular (by cytogenetics, FISH, PCR, or next-generation sequencing of AML-associated mutations) or multiparameter flow cytometry (MFC) evidence of persistent abnormalities in the setting of morphologic CR. In stage 2, MRD assessment will include MFC of bone marrow aspirates conducted at a central laboratory for uniformity. Objectives include characterization of SL-401 safety with determination of the maximum tolerated or tested dose, and preliminary assessment of efficacy including changes in MRD burden and response duration. As of 7/27/16, stage 1 has been completed and stage 2 is open for enrollment. Nine patients (stage 1) received SL-401 (7 ug/kg, n=3; 9 ug/kg, n=3; 12ug/kg, n=3). The median age was 63 years (range: 51-78 years); 6 males and 3 females were treated; 8 patients were in CR1 and 1 patient was in CR2 at enrollment. The 12 ug/kg dose level was the highest tested dose with no DLTs; MTD was not reached. The most common treatment-related AEs, all grades, were thrombocytopenia (3/9; 33%) and hypoalbuminemia (3/9; 33%); the most common ≥ grade 3 treatment-related AE was thrombocytopenia (1/9; 11%); there was no DLT. Patients treated at all doses received 1+ to 5+ cycles (ongoing) of SL-401, including 3 MRD+ patients treated at 7 ug/kg (n=1) or 9 ug/kg (n=2) who received 1-5 cycles, and 1 MRD+ patient treated at 12 ug/kg who is receiving ongoing SL-401 for 4+ cycles. For all 3 patients treated at 12 ug/kg (MRD+, n=1; MRD-, n=2), 2 patients remain on SL-401 and have received 1+ and 4+ cycles (both ongoing); one other patient treated at 12 ug/kg discontinued the study because of infection unrelated to study drug. Notably, the one MRD+ patient treated at 12 ug/kg (ongoing at 4+ cycles) had marked MRD reduction as determined by MFC at the local institution; this patient is being considered for stem cell transplant (SCT). Conclusions: Stage 1 is complete without DLT or MTD, and stage 2 (expansion) is open to enroll AML patients in CR1 or CR2 who are MRD+ at the highest tested dose of 12 ug/kg. The safety profile has been similar to that observed in other SL-401 clinical studies, with no unexpected AEs. Targeting MRD with SL-401 has the potential to reduce this chemo-resistant cell population and offer improved long-term outcomes for AML patients in remission with high risk of relapse. Updated data will be presented. Clinical trial information: NCT02270463. Disclosures Lane: N-of-1: Consultancy; Stemline Therapeutics: Research Funding. Sweet:Pfizer: Speakers Bureau; Karyopharm: Honoraria, Research Funding; Incyte Corporation: Research Funding; Novartis: Consultancy, Speakers Bureau; Ariad: Consultancy, Speakers Bureau. Wang:Immunogen: Research Funding; Incyte: Speakers Bureau. Stein:Seattle Genetics: Research Funding; Amgen: Consultancy, Research Funding, Speakers Bureau; Stemline Therapeutics: Consultancy, Research Funding; Argios: Research Funding; Celgene: Research Funding. Carraway:Incyte: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding, Speakers Bureau; Baxalta: Speakers Bureau. Prebet:celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Chen:Stemline Therapeutics, Inc.: Employment, Equity Ownership. Lindsay:Stemline Therapeutics, Inc.: Employment, Equity Ownership. Shemesh:Stemline Therapeutics: Employment, Equity Ownership. Brooks:Stemline Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties. Stone:Novartis: Consultancy; Juno Therapeutics: Consultancy; Celgene: 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; Agios: Consultancy; Amgen: Consultancy; Celator: Consultancy; Karyopharm: Consultancy; Jansen: Consultancy; Pfizer: Consultancy; ONO: Consultancy; Merck: Consultancy; Roche: Consultancy; Seattle Genetics: Consultancy; Sunesis Pharmaceuticals: Consultancy; Xenetic Biosciences: Consultancy. Jabbour:ARIAD: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Research Funding; BMS: Consultancy. Konopleva:Cellectis: Research Funding; Calithera: Research Funding.

Description: Background: Flotetuzumab (FLZ; MGD006/S80880) is a novel CD123 x CD3 bispecific DART® protein being tested in a Phase 1/2 study (NCT02152956) in patients with relapsed/refractory acute myeloid leukemia (AML). As with all T-cell redirecting therapies, cytokine secretion, inherent in T-cell activation, with ensuing potential for cytokine release syndrome (CRS), remains an important side effect. We have previously reported that multi-step dosing mitigates CRS severity (1). CRS diagnosis and treatment is guided by the occurrence of non-specific clinical signs, such as fever, chills, hypotension and tachycardia. Therefore, identification of predictors of CRS will be useful for optimal pt. management. Here we report on potential biomarkers of CRS severity that may help guide CRS management. Methods: Data from pts treated with FLZ at RP2D (lead-in dose of 30ng/kg/d for 3d, 100ng/kg/d for 4d for week 1 followed by 500ng/kg/d CIV week 2-4 of cycle 1, and a 4d-on/3d-off schedule for Cycle 2 and beyond in 28-day cycles) was collected and analyzed. Incidence and severity of CRS were analyzed for correlation with cytokine levels and changes in BM blasts. Relation between immune cells (T-cell subsets, monocytes) with tumor burden, percent CD123+ AML blasts, and CD123 expression, were interrogated as potential determinants of CRS. Administration, dose and frequency of tocilizumab (TCZ), an IL-6 receptor antagonist, were evaluated for their relationship with CRS severity, frequency, CRP and cytokine levels. Results: 30 pts were dosed at RP2D. Most pts experienced mild to moderate CRS (G1 26.7%, G2 60%) of short duration (median 1 day(d), range 1-26 d) and were conservatively managed to full resolution. Grade ≥ 3 events occurred in 4/30 pts (13%), with vasopressors use in 2 pts, and a median duration of 2.5 d (range 2-13 d). CRS frequency decreased with time on treatment: 42% occurred within the first week (LID), 39.6% occurring in week 2 (step up to 500ng/kg/day) and 18% occurring during week 3 and 4. IL-6 levels showed the best relationship with CRS severity, as previously shown (1). IL-6 levels, however, did not correlate with response. Twenty pts (67%) received at least one dose of TCZ (median 2 doses/pt; range 1-12 doses). As anticipated, mean IL-6 levels increased after administration of TCZ. CRS severity showed a relationship with the baseline frequency of circulating CD4+ cells (median 47% in G1 vs 73% in G ≥2, p = 0.0082), while CD8+ cell frequency did not correlate with CRS. Disease burden (absolute AML blasts, % CD123 AML blasts), CD123 expression on AML blasts, monocytes levels or effector-to-target ratio in the peripheral blood did not show a relationship with CRS severity. Importantly, CRS severity was not correlated with FLZ anti-leukemic activity. Conclusion: The frequency of CD4+ cells at baseline may be a potential biomarker for identifying pts at risk of more severe CRS. Early use of TCZ can effectively modify the activity of IL-6, a significant contributor to CRS, and blunt CRS severity. Since severity of CRS and IL-6 levels did not correlate with FLZ anti-leukemic activity, blunting its severity should be aggressively pursued. Early identification of pts at greater CRS risk together with multistep dosing (1) and early use of TCZ can effectively manage CRS with no impact on FLZ anti-leukemic activity.Jacobs et al. ASH 2017, abstract #3856 Disclosures Jacobs: MacroGenics: Employment. Viero:Servier: Employment. Baughman:MacroGenics: Employment. Sun:MacroGenics: Employment. Ying:Macrogenics: Employment. Muth:MacroGenics: Employment. Hong:MacroGenics: Employment. Sweet:BMS: Honoraria; Agios: Consultancy; Phizer: Consultancy; Astellas: Consultancy; Jazz: Speakers Bureau; Jazz: Speakers Bureau; BMS: Honoraria; Novartis: Consultancy, Honoraria, Speakers Bureau; Celgene: Honoraria, Speakers Bureau; Agios: Consultancy; Phizer: Consultancy; Celgene: Honoraria, Speakers Bureau; Astellas: Consultancy; Novartis: Consultancy, Honoraria, Speakers Bureau. Uy:Curis: Consultancy; GlycoMimetics: Consultancy. Ravandi:Xencor: Research Funding; Macrogenix: Honoraria, Research Funding; Bristol-Myers Squibb: Research Funding; Astellas Pharmaceuticals: Consultancy, Honoraria; Abbvie: Research Funding; Jazz: Honoraria; Amgen: Honoraria, Research Funding, Speakers Bureau; Orsenix: Honoraria; Abbvie: Research Funding; Orsenix: Honoraria; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Sunesis: Honoraria; Sunesis: Honoraria; Xencor: Research Funding; Astellas Pharmaceuticals: Consultancy, Honoraria; Amgen: Honoraria, Research Funding, Speakers Bureau; Macrogenix: Honoraria, Research Funding; Jazz: Honoraria. Foster:Celgene: Research Funding; Macrogenics: Research Funding; Pfizer: Research Funding; Shire: Honoraria. Rizzieri:Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: 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; Novartis: Consultancy; Arog: Consultancy, Membership on an entity's Board of Directors or advisory committees; Teva: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees. Arellano:Cephalon: Research Funding. Rettig:Amphivena Therapeutics: Research Funding; Novimmune: Research Funding. Topp:F. Hoffmann-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees, Research Funding; Regeneron Pharmaceuticals, Inc.: Honoraria, Research Funding; Boehringer Ingelheim: Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding. Lelièvre:Servier: Employment. Lowenberg:Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; international Scientific Advisory Board, Institute Gustave Roussy, Paris: Membership on an entity's Board of Directors or advisory committees; "Up-to-Date", section editor leukemia: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astex: Consultancy; Supervisory Board, National Comprehensive Cancer Center (IKNL), Netherlands: Membership on an entity's Board of Directors or advisory committees; Editorial Board "European Oncology & Haematology": Membership on an entity's Board of Directors or advisory committees; Elected member, Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; Chairman, Leukemia Cooperative Trial Group HOVON (Netherlands): Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Editorial Board "International Journal of Hematology": Membership on an entity's Board of Directors or advisory committees; Clear Creek Bio Ltd: Consultancy, Honoraria; Editorial Board "The Netherlands Journal of Medicine": Membership on an entity's Board of Directors or advisory committees; Chairman Scientific Committee and Member Executive Committee, European School of Hematology (ESH, Paris, France): Membership on an entity's Board of Directors or advisory committees. Wigginton:MacroGenics: Employment. Davidson-Moncada:MacroGenics: Employment.

Description: Background: Approximately 60 - 80% of AML patients achieve a complete remission [CR] with one or two cycles of induction chemotherapy, leaving many patients with refractory AML [PIF]. Unfortunately, the majority of patients in CR1 ultimately relapse. With salvage therapy, only 30-50% achieve CR2. Those with PIF or relapsed AML have shortened survival and few therapeutic options. Risk stratification is primarily based on karyotype, however other factors including age, initial white blood cell count, secondary AML and mutational status are also utilized to determine prognosis. HCT is an effective option for treatment of AML with intermediate/high risk features in CR1. It has also been utilized in refractory or relapsed disease. Advances in HCT over the last decade have improved overall survival (OS) and extended this option to older patients. Our aim is to characterize outcomes after HCT for AML patients who are not in CR1. Methods: We analyzed 136 AML patients who were not in CR1 at the time of HCT from 2004 - 2013. The conditioning regimen was fludarabine and myeloablative doses of PK targeted busulfan. IWG AML response criteria were used to define disease status at the time of transplant. Cytogenetic risk was based on the NCCN AML guidelines. OS is defined as the time from HCT until the time of death from any cause. Disease free survival (DFS) is defined as the time from HCT to the time of relapse or death from any cause. Results: Disease status consisted of 74 (54.4%) in CR2, 6 (4.4%) in CR3 or beyond, 27 (18.9%) were PIF, 21 (15.4%) with relapsed AML (REL) that was treated but still present at time of transplant, and 8 (5.7%) who received either no treatment or a hypomethylating agent (HMA). Median age was 52.0 (21.8 - 72.5) years, and 80 (59%) were male. Time from most recent treatment to HCT was 〈 1 month in 8 (5.8%), 1-3 months in 75 (55.8%), 〉3 months in 50 (36.8%) and not applicable in 3. Ninety-six (70.6%) had de novo AML, while 40 (29.4%) had secondary AML. Cytogenetic risk was favorable in 32 (23.5%), intermediate in 57 (42%), poor in 40 (29.4%) and unknown in 7 (5.1%). Graft-versus-host disease prophylaxis was tacrolimus with methotrexate or sirolimus, or mycophenolate mofetil. Donors included 41 (30.2%) matched related, 2 (1.4%) mismatched related, 65 (47.8%) matched unrelated and 28 (20.6%) mismatched unrelated donors. Peripheral blood stem cells were used in 97.2% of cases. Two year OS, DFS, cumulative incidence (CI) of relapse and CI-NRM for all patients was 45.3%, 35.2%, 47.1% and 18.2%, respectively. Two-year DFS stratified by disease status at time of HCT was 41.9%, 33.3%, 25.9%, 33.3% and 12.5% in CR2, CR3 or beyond, PIF, REL and HMA, respectively(p=0.011 for CR2 vs HMA) (Figure 1). Two-year DFS stratified by cytogenetic risk was 43.8%, 31.6%, 37.1% and 14.3% in favorable, intermediate, poor and unknown, respectively (p〉0.05) (Figure2). CI-Rel stratified by disease status was 43.2%, 16.7%, 66.7%, 42.9% and 50% in CR2, CR3 or greater, PIF, REL and HMA, respectively (Figure 3). Conclusions: We analyzed 136 AML patients after undergoing HST outside of CR1 and the cumulative incidence of relapse at two years was 47%. Relapse was highest in those with primary induction failure or residual disease after either no or low intensity therapy. These data suggest that patients with active disease at the time of transplant fare worse than those who are transplanted in remission, highlighting the importance of effective upfront therapies in order to obtain the maximum potential benefit from HCT. Cytogenetic risk stratification did not significantly impact outcomes, although those with favorable risk cytogenetics trend towards higher 2-year DFS vs those with intermediate or poor-risk disease. Trials looking at the impact of maintenance therapy post-transplant may be valuable in this patient population. Table 1. Disease Status @ HSCT CR2 CR3 or beyond PIF RES HMA/untreated 2 years 41.9% (30.6 - 52.8) 33.3% (4.6 - 67.6) 25.9% (11.5 - 43.1) 33.3% (14.9 - 53.1) 12.5% (0.7 - 42.3) Table 2. Cytogenetic Risk Group Favorable Intermediate Unfavorable Unknown 2 years 43.8% (26.5 - 59.8) 31.6% (20.1 - 43.7) 37.1% (22.5 - 51.8) 14.3% (0.7 - 46.5) Table 3. Cumulative Incidence of Relapse CR2 (1) CR3 or beyond (2) PIF (3) REL (4) HMA/untreated (5) 2 years 43.2% (32.2 - 54.6) 16.7% (0.0 - 53.5) 66.7% (48.1 - 82.9) 42.9% (23.0 - 64.0) 50.0% (18.1 - 81.9) Figure 1. Figure 1. Figure 2. Figure 2. Figure 3. Figure 3. Disclosures Sweet: Novartis Pharmaceuticals: Speakers Bureau; Ariad Pharmaceuticals: Consultancy, Speakers Bureau; Karyopharm Therapeutics Inc: Research Funding; Incyte: Research Funding. Lancet:Celgene: Consultancy, Research Funding; Seattle Genetics: Consultancy; Boehringer-Ingelheim: Consultancy; Pfizer: Research Funding; Kalo-Bios: Consultancy; Amgen: Consultancy. Perkins:PDL Biopharma: Research Funding. Field:PDL Biopharma: Research Funding.