ALBERT

Description: Background: Because infections are a major cause of morbidity and mortality after AML induction chemotherapy, patients typically remain hospitalized for monitoring and rapid antimicrobial therapy until hematopoietic recovery. With declining early mortality and improved oral antimicrobials, interest in moving post-induction care to the outpatient setting has emerged. In the 5-year period since completing a prospective phase 2 trial evaluating an Early Hospital Discharge (EHD) strategy, EHD following AML-like induction chemotherapy has become routine at our institution. In recent retrospective analyses, we found 〉80% of EHD patients required hospital readmission, primarily for neutropenic fever. Still, the EHD strategy was safe and reduced healthcare resource utilization, and EHD patients spent 〉70% of their post-chemotherapy time as outpatients. Here, we investigated differences in the pattern of infectious complications between patients managed as outpatients following induction chemotherapy and those who remain hospitalized until hematopoietic recovery. Methods: We retrospectively identified all adults ≥18 years with untreated AML/high-grade myeloid neoplasms (≥10% blasts in blood/ bone marrow) who started intensive induction chemotherapy ("7+3" or a regimen of similar/higher intensity) at our institution from 8/1/2014-7/31/2018. Patients were considered "EHD" if they were discharged from the hospital

Description: Background: Treatment of chronic myeloid leukemia (CML) with a tyrosine kinase inhibitor (TKI) offers significant improvements over previous treatments in terms of survival and toxicity yet has been associated with reduced health-related quality of life and very high cost. Discontinuing TKIs with regular monitoring is safe, but little is known about the impact of discontinuation on patient-reported outcomes (PROs). In the largest U.S. study to date, we evaluated molecular recurrence of CML and PROs after TKI discontinuation. Methods: The Life After Stopping TKIs (LAST) study was a prospective single-group longitudinal study. Key inclusion criteria were age 〉 18 years, patient on TKI therapy (imatinib, dasatinib, nilotinib, or bosutinib) for 〉 3 years with documented BCR-ABL 〈 0.01% by PCR for 〉 2 years, and no previous TKI resistance. We monitored disease outcome (PCRs by central lab) and PROs (PROMIS computerized adaptive tests via REDCap) monthly for the first 6 months, every 2 months until 24 months, then every 3 months until 36 months. Molecular recurrence was defined as 〉 0.1% BCR-ABL IS by central lab (loss of major molecular response [MMR]). We considered 3 points to be clinically meaningful and hypothesized that by 6 months after TKI discontinuation, fatigue, depression, sleep disturbance, and diarrhea would improve by at least 3 points each, corresponding to a standardized effect size of 0.3. Given reports of a withdrawal syndrome of musculoskeletal pain in some patients after discontinuation, pain was an additional outcome of particular interest. For each PRO domain, we estimated a polynomial piecewise linear mixed effects model that specified one nonlinear trajectory after TKI discontinuation and, for those with molecular recurrence, another trajectory after TKI restart. The models included patient-level random effects for the intercepts and linear slopes. Results: From 12/2014 to 12/2016, 172 patients enrolled from 14 U.S. sites. Median age was 60 years (range 21-86) and 89 (52%) were female. The median time on TKI prior to enrollment was 81 months (IQR 54-123). With a minimum follow-up of 24 months, 107 (62%) patients remained in a treatment free remission (TFR). Reasons for restarting therapy were: loss of MMR by central (n=56) or local (n=2) lab, patient decision (n=4), and withdrawal syndrome (n=3). Missing PRO data was minimal (〈 5%) with 〉 2000 assessments completed. For patients in TFR at 6 months, the average estimated improvement in fatigue was 2.6 points (95% CI 2.5-2.7), depression was 1.9 points (95% CI 1.8-1.9), sleep disturbance was 0.9 points (95% CI 0.8-1.0), and diarrhea was 2.7 points (95% CI 2.6-2.7). The average estimated worsening in pain interference (i.e., the extent to which pain affects daily life) was 0.4 points (95% CI 0.3-0.5). The figure shows the distribution of estimated change for each domain at 6 months. All patients showed improvements in depression, diarrhea, and fatigue. About 1 in 6 patients (17%) experienced a clinically meaningful (i.e., at least 3 points) improvement in fatigue and/or diarrhea at 6 months. Conclusion: The LAST study is the largest US TKI discontinuation study to date, and the first to include comprehensive PRO measurement. For patients in TFR at 6 months, TKI discontinuation conferred modest benefits in fatigue and diarrhea on average, with a negligible increase in pain interference. Some patients experienced more notable improvements in fatigue and diarrhea. Planned secondary analyses will include change over time up to 3 years and evaluation of additional PRO domains, including anxiety, physical function, social function, and sexual function. Our results provide important new evidence to support shared patient-provider clinical decision making regarding TKI discontinuation for patients with CML. Figure. Disclosures Radich: Novartis: Other: RNA Sequencing; TwinStrand Biosciences: Research Funding. Mauro:Pfizer: Consultancy; Takeda: Consultancy; Novartis Oncology: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy. Pinilla Ibarz:Sanofi: Speakers Bureau; Abbvie: Consultancy, Speakers Bureau; Teva: Consultancy; Janssen: Consultancy, Speakers Bureau; Novartis: Consultancy; Takeda: Consultancy, Speakers Bureau; Bayer: Speakers Bureau; TG Therapeutics: Consultancy; Bristol-Myers Squibb: Consultancy. Larson:Celgene: Consultancy; Novartis: Honoraria, Other: Contracts for clinical trials; Agios: Consultancy. Oehler:Blueprint Medicines: Consultancy; NCCN: Consultancy; Pfizer Inc.: Research Funding. Deininger:Humana: Honoraria; Incyte: Honoraria; Blueprint: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Research Funding; Ascentage Pharma: Consultancy, Honoraria; TRM: Consultancy; Sangoma: Consultancy; Fusion Pharma: Consultancy; Adelphi: Consultancy; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; Sangamo: Consultancy. Shah:Bristol-Myers Squibb: Research Funding. Ritchie:Tolero: Other: Advisory board; Celgene: Other: Advisory board; Celgene, Novartis: Other: travel support; Jazz Pharmaceuticals: Research Funding; Celgene, Incyte, Novartis, Pfizer: Consultancy; AStella, Bristol-Myers Squibb, Novartis, NS Pharma, Pfizer: Research Funding; Ariad, Celgene, Incyte, Novartis: Speakers Bureau; Genentech: Other: Advisory board; Pfizer: Other: Advisory board, travel support; agios: Other: Advisory board. Silver:PharmEssentia: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Cortes:Sun Pharma: Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; BiolineRx: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Biopath Holdings: Consultancy, Honoraria; Immunogen: Consultancy, Honoraria, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Astellas Pharma: Consultancy, Honoraria, Research Funding. Atallah:Jazz: Consultancy; Helsinn: Consultancy; Pfizer: Consultancy; Takeda: Consultancy, Research Funding; Jazz: Consultancy; Helsinn: Consultancy; Novartis: Consultancy.

Description: Acute myeloid leukemia (AML) is characterized by increased self-renewal of leukemia stem/progenitor cells and failure of differentiation to mature myeloid cells. MicroRNAs (miRNAs, miRs) are short non-coding RNAs whose power stems from the ability to regulate hundreds of targets by interfering with gene expression by degrading messenger RNA or blocking protein translation. It has become evident that miRNAs are important regulators of normal cell processes that are altered in cancer, and restoring or inhibiting miRNAs may be a therapeutic strategy in cancer. MiRNAs play a significant role in normal hematopoiesis and differentiation; however, our understanding of how miRNAs contribute to impaired differentiation and proliferation in acute leukemia remains limited. We have used a combined approach to prioritize miRNAs for investigation for functional roles in leukemogenesis. To identify miRNAs that may play a role in altered cell proliferation or differentiation of AML cells, we used a functional miRNA library screen. We transduced a high-throughput lentiviral library containing 613 precursor miRNAs (Systems Biology) into the AML cell line THP-1 harboring a MLL-AF9 translocation. These cells were then treated with 12-O-tetra-decanoylphorbol-13-acetate (TPA), an agent that induces monocytic differentiation and cell adhesion. After recovery of proliferating cells we compared miRNA expression before and after TPA induced differentiation using quantitative PCR to identify enriched miRNAs (may block differentiation) and miRNAs that drop out (may promote differentiation). To prioritize miRNAs with phenotypic effects that may be relevant to AML, we focused on miRNAs that are differentially expressed in various AML subtypes, using both miRNA-sequencing data from primary pediatric patient AML samples (N=117) and mature miRNA expression of primary adult patient AML samples (N=20). Selected miRNAs were cloned into a lentiviral expression vector and retested in THP-1 cells to assess whether proliferation or differentiation was altered by expression. In line with previously published data we found enrichment of miR-9-1 and members of the miR-17-92 cluster, and its paralogs miR-106a-363 and miR-106b-25, as inhibitors of myeloid differentiation. In addition, we have validated three miRNAs (miR-590, miR-550A1 and miR-550A2) with previously uncharacterized roles that block differentiation and increase proliferation of THP-1 cells. These phenotypes were confirmed in other AML cell lines, including NB4 cells (PML-RARA translocation) and U937 cells (MLL-AF9 translocation). Increased expression of either miR-590 or miR-550A2 enhances MAPK signaling, as detected by increased phospho-ERK1/2, which influences cell proliferation. We have identified that PPP2R2A, the regulatory B55 alpha subunit of the tumor suppressor protein phosphatase 2A (PP2A), is a miR-590 target. Regulation of this complex by miR-590 could contribute to alterations in MAPK/ERK signaling. To identify additional miR-590 and miR-550A putative targets, we profiled gene expression changes by microarray (Illumina Human HT-12v.4) in THP-1 and NB4 cells expressing miR-590 or miR-550A2 versus control cells. Validation of identified putative targets, as well as functional investigations assessing the impact of the identified miRNAs and targets on AML cell proliferation or differentiation, are underway. In conclusion, functional miRNA screening is an important tool to prioritize differentially expressed miRNAs identified in primary AML patient samples that alter differentiation and proliferation. Using this approach we have identified new roles for miR-590 and miR-550A2 in AML. Our goal is to determine mechanistically how these miRNAs block differentiation in AML cells and to establish how to target these pathways therapeutically to promote differentiation and AML cell death. Disclosures No relevant conflicts of interest to declare.

Description: Background: Optimal treatment for medically less fit adults with acute myeloid leukemia (AML) remains uncertain. Retrospective data suggest intensive therapy may lead to better outcomes in these patients. However, these findings must be interpreted cautiously because of the possibility of selection bias and other confounders. Ideally, the optimal treatment intensity is defined via randomized trial but whether patients and their physicians are amenable to such a study is unknown. We therefore designed a trial (NCT03012672) to 1) evaluate the feasibility of randomization between intensive and non-intensive therapy in this population and 2) examine the impact of treatment intensity on response rate and survival. We used CLAG-M as high-dose cytarabine-based intensive induction therapy. Rather than selecting different classes of drugs in the 2 treatment arms- which may have different modes of action and therefore confound the question of treatment intensity - we used reduced-dose ("mini") CLAG-M as the non-intensive comparator. Methods: Adults ≥18 years were eligible if they had untreated AML or high-grade myeloid neoplasms (≥10% blasts in blood or marrow) and were medically less fit as defined by having a "treatment related mortality" (TRM) score of ≥13.1, corresponding to a 〉10-15% 28-day mortality with intensive chemotherapy. Left ventricular ejection fraction ≤45% was the only organ function exclusion. Patient-physician pairs were first asked if they were amenable to randomized treatment allocation. If so, they were randomized 1:1 to mini- vs. regular-dose CLAG-M. If not, in order to evaluate our secondary endpoints, the patient or physician could choose the treatment arm and still enroll on study. Patients and physicians then completed surveys elucidating their decision-making processes. Up to 2 induction courses were given with mini- vs. regular-dose CLAG-M: cladribine 2 or 5 mg/m2/day (days 1-5), cytarabine 100 or 2,000 mg/m2/day (days 1-5), G-CSF 300 or 480µcg/day for weight

Description: Background Adults with newly diagnosed or relapsed acute myeloid leukemia (AML) and high-risk myelodysplastic syndromes (MDS) typically receive intensive chemotherapy to achieve disease remission. Generally, these patients remain hospitalized until blood count recovery due to the risk for infections and bleeding during pancytopenia. However, a recent small pilot study at our institution suggested that early discharge (ED) following induction/salvage therapy for MDS/AML may be safe and may reduce cost. We therefore conducted a phase 2 study to test this care strategy in a larger cohort of patients (NCT01235572). Methods Patients aged 18-75 years with high-risk MDS or AML (other than acute promyelocytic leukemia) were enrolled before or during induction or salvage chemotherapy and provided with outpatient care teaching. Patients were considered eligible for ED if they fulfilled the following medical and logistic criteria: ECOG performance status of 0-1, adequate organ function; no active bleeding; agreeable to close outpatient follow-up; reliable caregiver; and residency within 60 minutes of the outpatient clinic. Patients who met medical but not logistic criteria served as inpatient controls. If readmitted, ED was again possible if all medical/logistic criteria were met. Patients remained on protocol until blood count recovery, additional chemotherapy was administered, or a maximum of 45 days. Our goal was to compare the number of early deaths, healthcare costs and resource utilization among ED patients versus inpatient controls. Safety was monitored with early stopping if the early death rate was 〉7% in the ED group, with a predefined interim analysis after 30 patients. All data are provided as median (range). Results One hundred and seven eligible patients were enrolled over a 2-year period. Two patients died during chemotherapy. Twenty-seven patients failed to meet medical ED criteria after completion of chemotherapy and were taken off study, mostly due to poor performance status. Eighteen patients, age 51.4 (22-70) years, met medical but not logistic ED criteria and served as controls; they were followed for 14 (9-41) days, with 7 patients taken off study at the time of hospital discharge before blood count recovery. Sixty patients, age 51.6 (22-71) years, met all ED criteria and were discharged upon completion of induction (n=19) or salvage (n=41) chemotherapy for AML (n=50) or MDS (n=10). A median number of 1 (1-3) readmission occurred in 53 of these patients, primarily for neutropenic fever; 8 patients were readmitted twice and 3 patients were readmitted 3 times prior to coming off study. Overall, ED patients spent 12.8 (0-38) and 7.5 (0-33) days as out- and inpatients, respectively, for a total of 62.7% (0-100%) of the study time spent as outpatients. ED patients required 0.41 (0-1.9) clinic visits and 0.13 (0-0.66) physician visits per outpatient day. Duration of IV antibiotics was similar in ED and control patients (10 [0-40] vs 12 [0-40] days; p=0.38) as was number of red blood cell transfusions (0.27 [0.0-0.94] vs 0.29 [0.08-0.548] units/study day; p=0.21). In contrast, ED patients required fewer platelet transfusions (0.21 [0.09-1.25] vs 0.33 [0.21-0.80] units/ study day; p=0.02). Six patients in the ED group required between 1-6 days of intensive care unit (ICU) care (p= 0.17 for the difference in ICU days between discharges and controls). Three deaths occurred in the ED group during the study period: two of sepsis (2 and 7 days after readmission), and one of fungal sinusitis (11 days after readmission). The median daily total professional and facility charges, dated from the day of re-evaluation until removal from protocol, were significantly lower for patients discharged early compared to inpatient controls: $3,871 [$360.86-$13,361] vs $6,283 [$4,868-$11,898], p

Description: A retrospective study of CML allogeneic hematopoietic stem cell transplants (HSCT) at the FHCRC from January 2001 to April 2004 was conducted to address the impact of pre-transplant imatinib mesylate (IM) therapy on early treatment toxicity, non-relapse mortality (NRM), overall survival (OS), and relapse. Forty-eight patients, median age 40 years (range, 20–64), received IM prior to transplantation for a median duration of 9.5 months (range, 3–30). Twenty-nine patients received unrelated or mismatched donor HSCT and 19 patients received matched related donor (MRD) HSCT. Forty-four patients were in chronic phase (CP) and 4 patients in accelerated phase (AP) at the time of diagnosis and IM initiation. At transplantation 28 patients were in CP, 14 in AP, 3 in blast crisis (BC) remission, and 3 in BC. Patients were conditioned with busulfan and cytoxan (35) and cytoxan and total body irradiation (13). The median time to neutrophil engraftment for all patients was 16 days (range, 11–33). Median average bilirubin to day 20 and median maximum bilirubin to day 20 were used as an indicator of early transplant hepatotoxicity. These values were 1.0 (range 0.4–5.4) and 1.6 (range 0.6–11.4) for all patients, respectively. Among 48 patients 8 deaths occurred due to poor engraftment (1), diffuse alveolar hemorrhage (1), pneumonia (1), acute GVHD (2), myocardial infarction (1), refractory ITP (1), and fungal infection (1). Only one relapse occurred on day 553 in a CP patient who had no response to IM after 6 months of therapy prior to HSCT. For all patients 100-day survival was 92% (95%CI, 84–99%), one-year survival 85% (95% CI, 74–97%), and 1.5-year survival 73% (95%CI, 54–92%) with a median follow-up of 333 days (range 97–912 days). One of 19 MRD recipients died (at day 440) with a median follow-up among survivors of 291 days. One-year survival for unrelated or mismatched donor recipients was 77% (95% CI, 60–94%). One-year survival was 93% (median follow-up 345 days) for 28 CP patients and 70% (median follow-up 308 days) for 14 AP and 3 BC remission patients. All three patients transplanted in blast crisis are alive (follow-up 115–465 days). There was a suggestive association between time from diagnosis to transplant and mortality (P=0.10) for all patients. To assess the impact of IM response at transplant, patients were assigned to 1 of 5 response groups. One of 13 patients transplanted in complete cytogenetic response (CCyR) died (median follow-up 291 days). None of 9 patients (7 CP and 2 AP) with a major cytogenetic response (MCyR) to IM died (median follow-up 344 days). Three of 10 patients (2/8 CP and 1/2 AP) with no response to IM or with evidence of cytogenetic or hematologic relapse died (median follow-up 467 days). Two of 10 patients with evidence of clonal evolution on IM (median follow-up 354 days) and 2/6 patients who progressed to BC on IM (median follow-up 341 days) died. CONCLUSION: For all patients acute hepatotoxicity, one-year OS, and NRM appear similar to our Center’s historical data. Patients achieving a CCyR or MCyR after IM therapy did particularly well, perhaps due to CP disease at HSCT and the shorter time to transplant (9 mo, range 3–29 mo). Poor IM response may serve as an indicator of poorer transplant outcome; however, more advanced disease at and longer time to transplantation (32 months, range 4–118 months) alone may explain the more adverse outcome.

Description: Imatinib mesylate (IM) has dramatically changed the treatment approach for patients with chronic myeloid leukemia (CML). However, ~20% of chronic phase (CP) patients are initially resistant to IM, and among patients who achieve a complete cytogenetic response (CCyR), a small minority relapse back into CP or progress to advanced disease. Abl tyrosine kinase domain mutations are the major cause of secondary resistance. Oligonucleotide microarray analysis was used to study gene expression patterns associated with primary IM resistance and relapse after initial successful response to IM. Samples included total RNA from diagnostic samples of 25 CML CP patients within 6 months of diagnosis and at the time of failure (7 patients); total RNA from 18 patients who relapsed after initial CCyR with documented Abl point mutations (12 CP and 6 BC); and 10 myeloid progenitor samples (sorted by CD34 and CD38 status) from an IM naïve and IM resistant (R) patient, both in blast crisis. Results: For primary IM resistance, analysis of paired samples before and after treatment revealed that primary failure was associated with the differential expression of genes associated with RNA post-transcriptional modification, protein synthesis, cellular growth and proliferation, and cell death. Two genes with the highest differential expression included the apotosis resistance genes API5 and TRAF5. TRAF5 was also increased in patients who relapsed after initial CCyR, while API5 showed significantly increased expression in sorted CD34+ cells from an IMR patient. In secondary resistance patients, a set of drug transporters including ABCA2, ABCA3, MDR1, and ABCC3 had increased expression and hOCT1 decreased expression relative to 42 IM naïve CP patients. In vitro experiments compared K562 resistant (R) and sensitive (S) cell lines over time exposed to IM. The K562 IMR cell line showed a 1.5 log higher expression of ABCG2 and a 1 log higher expression of TRAF5 compared to the K562 IMS cells. However, sequential clinical samples of 16 IM non-responders vs. 14 CCyR patients showed no change in ABCG2 expression, possibly because ABCG2 is expressed only in early progenitor cells, not differentiated cells. The importance of using CD34+ cells was demonstrated in 7 array studies comparing gene expression in CD34+ selected cells from an IMR patient compared to an IM naïve patient. IM resistance was associated with increased expression of genes associated with cell cycle, DNA recombination and repair, and proliferation. Genes associated with apoptosis resistance included increased expression of API5, survivin, and decreased expression of BAK1. Protein serine/threonine and tyrosine kinases associated with cell proliferation/survival and tumor progression with increased expression in the IMR patient included: AURKB, AKT3, BUB1B, CDC2, CHEK1, MAPK9, STK6, TTK, and WEE1. Conclusion: Gene expression studies suggest that primary resistance to IM therapy is associated with resistance to apoptosis; relapse on IM is associated with activation of drug transporter genes and genes associated with disease progression; in studying disease response and resistance, primitive hematopoetic cells are critical for analysis.

Description: Abstract 2737 Synonymous SNPs may directly impact gene function through various translational or post-translational mechanisms. Further, such “silent” SNPs in the mutational hotspots of AML-associated genes have recently been reported to carry prognostic impact. We aimed to determine the prevalence, clinical associations, and prognostic significance of a known SNP in exon 4 of IDH1, near the location of the frequently-mutated R132 codon. Diagnostic marrow specimens from 253 pediatric AML patients (treated on the COG trial AAML03P1) and 274 adult AML patients (treated on SWOG trials S9031, S9333, or S9500) were analyzed for the presence of SNP rs11554137 via direct sequencing. In the pediatric cohort (median age 9.8 years), SNP rs11554137 was present in 27 of 253 (10.7%) patients. SNP+ pediatric patients did not differ significantly from wild-type patients in terms of sex, racial distribution (African American patients accounted for 23% of SNP+ patients vs. 14% of wild-type patients, P=0.24), bone marrow blast percentage, or age distribution, except in patients aged 0–2 years, who accounted for 44% of SNP+ patients vs. 23% of wild- type patients (P=0.013). Recurrent cytogenetic abnormalities occurred with similar frequencies in both the SNP+ and wild-type pediatric populations, as did FLT3/ITD, NPMc, and CEBPA mutations. Miscellaneous cytogenetic abnormalities accounted for 33% of SNP+ patients vs. 14% of wild-type patients, P=0.033. IDH1 SNP status had no prognostic impact on survival in the pediatric cohort, as SNP+ and wild-type patients had similar rates of five-year overall survival (OS, 76% vs. 63%, P=0.50), disease-free survival (DFS, 48% vs. 53%, P=0.97), and relapse rate (RR, 39% vs. 39%, P=0.94). In the adult cohort (median age 63 years), the IDH1 SNP was present in 30 of 274 (10.9%) patients. A slight female predominance for the SNP (63% vs. 37%, P=0.052) occurred among adult patients. The SNP was more prevalent in African American patients, who accounted for 30% of the SNP+ patients vs. 7% of wild-type patients, P=0.0046. SNP+ patients also had somewhat higher diagnostic bone marrow blast percentages (medians 80% vs. 70%, P=0.025). The normal karyotype subset accounted for similar proportions of SNP+ vs. wild-type patients (42% vs. 46%, P=0.83). Notably, SNP rs11554137 was not present in adult core-binding factor AML. Miscellaneous cytogenetic abnormalities were significantly more common in SNP+ patients (46% vs. 22%, P=0.022). SNP status was not significantly associated with FLT3/ITD status when all adult patients were considered (P=0.14). However, within the normal karyotype subset, FLT3/ITD was present in 90% of SNP+ patients vs. 59% of wild-type patients (P=0.0053). SNP+ patients had somewhat poorer 5 year OS (10% vs. 18%, hazard ratio [HR]=1.17) though this difference was not statistically significant (P=0.44). Among the 142 patients who achieved complete remission (CR), however, 5-year relapse-free survival (RFS) was significantly worse for SNP+ patients (0% vs. 25%, HR = 2.89, P=0.0014). Of the 14 SNP+ patients who achieved CR, 13 relapsed and the 14th patient died of sepsis in remission after 61 days. In multivariate analysis, after adjusting for the effects of age and cytogenetic group, SNP rs11554137 retained an independent prognostic effect (P=0.0062) regarding RFS. Notably, when FLT3/ITD status is included in multivariate analysis, SNP positivity loses independent prognostic significance (HR=1.72, P=0.18). Genome-wide expression profiling was performed on 134 pediatric AML specimens in whom IDH1 SNP status was known. By comparing SNP+ patients with wild-type patients, we derived a distinct gene-expression signature for patients with SNP rs11554137. Among the most upregulated probe sets in the SNP+ cohort were those representing PEX6 and NFYA, both of which interact with the TGF-beta/SMAD signaling network; the retinoid × receptor beta gene RXRB; and the FER gene, a tyrosine kinase critical to FLT3 signaling. The IDH1 SNP rs11554137 is present in approximately 11% of pediatric and adult AML patients, and gene expression profiling data suggests that leukemia in SNP+ patients may have unique biologic features. The SNP was an independent predictor of decreased RFS in adult AML in univariate analysis, but not in multivariate analysis when adjusting for FLT3/ITD status. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 2743 CD52 is a cell surface glycoprotein of unknown function that is expressed in B and T lymphocytes, macrophages, and monocytes, but is not expressed in normal hematopoietic stem/progenitor cells. CD52 is also expressed in chronic lymphocytic leukemia (CLL), B-cell acute lymphoblastic leukemia (ALL), and some cases of T-ALL. Alemtuzumab, a recombinant humanized monoclonal antibody, targets CD52 and is used to treat CLL. In contrast to normal hematopoietic stem/progenitor cells, CD52 expression has been described in acute myeloid leukemia (AML) and in blast crisis (BC) chronic myeloid leukemia (CML). Based on these observations we were curious whether CD52 expression distinguished normal from malignant or more mature from immature stem/progenitors cells, and whether these cells were sensitive to alemtuzumab. CD52 expression was examined in three blast cell populations (CD34+/CD38-, CD34+/CD38+, and CD34-) in patients with myeloid (44) and lymphoid (18) neoplasms, and normal patients (6). In normal hematopoietic cells, stems cells are enriched in the first population; more mature cells are characterized by increasing CD38 expression and loss of CD34 expression. In AML and CML leukemia stem cells may arise within either CD34+ population and possibly in the CD34- population. Relative to normal lymphocytes average CD52 expression could be characterized as low to moderate. Using an expression cutoff of 〉 20%, in contrast to normal patients, CD52 was detected in at least one of three blast populations in almost all patients. Using a more stringent cutoff of 〉 50%, CD52 was expressed in CD34+/CD38- cells in 7/11 B-ALL and 6/7 T-ALL cases and was concordantly expressed in the other two populations. Using the same criteria in myeloid malignancies (Table 1), expression occurred more frequently in AML, AML arising from myelodysplastic syndrome (MDS), and BC CML. In AML and AML arising from MDS, CD52 was expressed in the 34+/38- population in 7/15 cases (47%) and 4/7 cases (57%), respectively; it was expressed in both BC CML patients. In AML and BC CML patients, CD52 was expressed at similar levels in the CD34+/CD38+ fraction. No clear association between CD52 expression and cytogenetic abnormalities was found. We then examined whether CD52 expression differentiated normal from malignant blasts (CD34+/CD38- and CD34+/CD38+) in two CML myeloid BC patients. FISH and quantitative PCR demonstrated that BCR-ABL was expressed in all 4 populations, which were also morphologically distinct. Colony forming unit (CFU) assays demonstrated a significantly decreased ability to form CFU (on average 5–20 fold decrease) in CD52+/CD34+/CD38- CML cells suggesting CD52 cells may be more mature. Lastly and not previously described, we found that several BC CML cell lines express CD52, and complement-mediated cell cytotoxicity was similar in the highest expressing cell lines to that seen in EHEB (B-CLL) cells known to be targeted by alemtuzumab. Thus, alemtuzumab may have clinical efficacy in BC CML. In conclusion, CD52 is expressed on blast populations enriched for leukemic stem cells. Whether the absence or presence of CD52 more precisely segregates a leukemia stem cell containing population currently remains unknown and requires functional testing in a murine model. Our preliminary experiments in CML suggest CD52 may not differentiate between normal and malignant stem/progenitor cells. However, CD52 expression may distinguish normal and malignant stem cell populations in cases where CD52 and CD38 are more highly expressed. The observation that CD52 expression is increased in acute vs. chronic leukemias raises the intriguing possibility that CD52, if not directly involved, may be a marker for genes or pathways contributing to the block in differentiation seen with progression to acute leukemia. Furthermore, given that CD52 expression is heterogeneous in chronic disorders, it is possible that CD52 expression within these populations may correlate with poor prognosis or impending leukemic conversion. Table 1. The proportion of patients (44) expressing CD52 at levels 〉 50% in 3 blast populations. Three populations were present in most, but not all patients. Gray shading indicates chronic myeloid diseases. MPN is myeloproliferative neoplasm; NOS is not otherwise specified; ET is essential thrombocythemia; CMML is chronic myelomonocytic leukemia; and an arrow represents progressed to. Disclosure: Oehler: Pfizer: Research Funding. Radich:Novartis: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria.