ALBERT

Description: Introduction: APL, while highly curable in the modern era, remains a therapeutic challenge in the high-risk subset, with high rates of early mortality and relapse compared to non-high-risk APL. Recent evidence has confirmed excellent outcomes in non- high-risk APL with the combination of ATO and ATRA, and a previous pilot study had indicated the efficacy of a combination of ATO + ATRA + GO in high-risk APL. The North American Leukemia Intergroup designed a larger phase 2 study to confirm the efficacy and safety of this combination in high-risk APL. Primary Objectives: 1) assessment of 3-year event-free survival (EFS); 2) assessment of early (6 week) death rate. Methods: Adult patients with newly diagnosed high-risk APL (WBC ≥10k/uL) were eligible. Induction therapy consisted of: ATRA (45 mg/m2/day), beginning on day 1; ATO 0.15 mg/kg/day, beginning on day 10; GO 9 mg/m2on day 1. ATRA and ATO were continued until remission achieved. Patients in remission went on to receive consolidation with ATO x 2 cycles, followed by ATRA + daunorubicin x 2 cycles, followed by GO x 2 cycles. Subsequent maintenance therapy consisted of ATRA + 6-mercaptupurine + methotrexate for up to 1 year. Results: Between 2008 and 2013, 73 registered patients began protocol treatment. Median age was 46.5 years, with 52% females and 48% males. Sixty-two (85%) patients completed induction therapy as planned, and 50 patients (68%) completed all planned consolidation. Sixty-two patients (85%) achieved a documented complete response (CR). Non-responses were attributable to lack of response assessment (n=10), most commonly related to death. One patient had resistant disease. With a median follow-up of 3.3 years, the Kaplan Meier 3-year EFS estimate was 79% (95% CI 68% - 87%), which was significantly improved compared to the protocol-defined historical rate of 50% (p

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: SRSF2 is a RNA-binding protein frequently mutated in CMML tasked with marking exon-intron boundaries during alternative splicing. SRSF2 contains a domain consisting of serine-arginine repeats that are dynamically phosphorylated and comprise a major regulatory mechanism in RNA capture. It has been previously demonstrated that EGFR signaling can elicit the phosphorylation of SRSF2 in an AKT dependent manner, resulting in functional alterations in exon usage of SRSF2 target genes. We previously reported that GM-CSF hypersensitivity is a reproducible feature of CMML. Because AKT is a known signaling intermediate of GM-CSF, we hypothesize that aberrant GM-CSF signaling could induce mutation-independent splicing abnormalities in CMML via phosphorylation of SRSF2. To test this hypothesis, we selected CMML samples that displayed GM-CSF hypersensitivity but lacked mutations by Sanger sequencing in 5 splicing-related genes commonly mutated in myeloid malignancies (SRSF2, SF3B1,U2AF1, ZRSF2,and PRPF40B) and labeled this group as CMML ‘splicing WT’. A second sample set included CMML specimens with isolated SRSF2 mutation (SRSF2 ‘splicing MT’). Bone marrow mononuclear cells from the SRSF2 ‘splicing WT’ group (n=4), CMML ‘splicing MT’ group (n=4), and normal controls (n=4) were lymphodepleted (CD3 and CD19) to enrich for the clonal myeloid population. RNA was extracted and whole transcriptome RNA sequencing and exon arrays were performed to compare the relative global exon usage of CMML ‘splicing WT’, CMML ‘splicing MT’, and normal controls. Briefly, the human exon 1.0 ST array was used for exon array analysis and splice index was calculated with the Exon/Gene Array Analyzer Web Tool (Gellert Bioinformatics 2009). RNA sequencing data was generated and aligned with TopHat2 (Kim Genome Bio 2013) while read counts and exon usage assignments were made with DexSeq (Anders Genome Res 2012). Splice indices determined by exon array demonstrated statistically significant exon usage differences between CMML ‘splicing MT’ and normal controls consistent with previously published results (Figure 1a). Interestingly, when CMML ‘splicing WT’ was compared to normal controls, a statistically significant difference in exon usage was also identified (Figure 1b). Further, when ‘splicing MT’ and ‘splicing WT’ were compared by splice index, differences in exon usage differences were dramatically reduced indicating similar splicing abnormalities in the CMML ’splicing WT’ group (1c). Euclidian hierarchical clustering at the gene- and exon-level separated normal controls from CMML groups but failed to separate ‘splicing MT’ from ‘splicing WT’, supporting the notion that mutation-independent splicing aberrancy may characterize CMML (1d). Global patterns in exon usage were also tested by whole transcriptome RNA-sequencing and were similar to those described above identified by exon array splice index.Figure 1Figure 1. We first attempted to determine if the transcript levels of core splicing components in CMML ‘splicing WT’ were altered but were unable to identify differences in expression when compared to CMML ’splicing MT’ and controls. Next we explored the possibility that GM-CSF signaling, known to be upregulated in CMML, could post-translationally modify SRSF2. The THP-1 monocytic leukemia cell line was stimulated with 10ng/ml of GM-CSF for 15 minutes. Cell lysates were immediately prepared and western blot analysis was used to assess SRSF2 phosphorylation after stimulation with GM-CSF, demonstrating induction of pSRSF2 at 15 minutes as accompanied by induction of the known GM-CSF signaling intermediates pJAK2, pAKT, and pERK. Pharmacologic inhibition of these intermediates abrogated GM-CSF-induced pSRSF2, whereas only the JAK 1/2 inhibitor ruxolitinib was able to inhibit pSTAT5, pAKT, and pERK, suggesting that JAK2 is a proximal kinase in the signaling cascade. Our results indicate that splicing abnormalities are present in CMML specimens lacking mutations in splicing-related genes. GM-CSF induces phosphorylation of SRSF2 for post-translational regulation of the RS domain. Low dose GM-CSF dependent pSRSF2 and functional splicing analyses are currently underway in primary CMML ‘SRSF2 WT’ samples to directly determine whether GM-CSF hypersensitivity is responsible for mutation-independent splicing aberrancies. Disclosures: List: Celgene: Membership on an entity’s Board of Directors or advisory committees.

Description: Introduction Lenalidomide (LEN) is the standard of care for treatment of transfusion dependent lower risk myelodysplastic syndromes (MDS) with chromosome 5q deletion (del 5q). In the MDS-002 study, 26% of lower risk transfusion dependent MDS patients became red blood cell transfusion independent after LEN treatment. National Comprehensive Cancer Network (NCCN) clinical guidelines list LEN as a second line treatment alternative for transfusion dependent anemia in lower risk non-del 5q MDS after azanucleosides failure. The response rate to LEN after azanucleosides failure, however, is not known given that the MDS-002 study preceded FDA approval of azanucleosides. To address the best sequence of LEN to optimize response potential in lower risk MDS, we examined the response rates to LEN in non-del 5q lower risk MDS when offered as first line after (erythroid stimulating agents) ESA's or after azacitidine failure. Methods This was a retrospective study conducted using the Moffitt Cancer Center (MCC) MDS database. We identified patients with lower risk MDS who received both LEN and azacitidine as first or second line therapy after erythroid stimulating agents. Lower risk MDS was defined according to the international prognostic scoring system (IPSS) Low or intermediate-1 (int-1) risk groups. The primary endpoint was to compare rates of erythroid hematological improvement (HI-E) between the group of patients who received LEN as first line therapy followed by azacitidine as second line (LEN 1st line group) and those who received LEN as second line therapy after azacitidine (LEN 2nd line group). HI was defined according to international working group criteria (IWG 2006). Chi- square test was used for categorical variables, T-test was used for continuous variables, and Kaplan Meier estimates for overall survival. All analyses were conducted using SPSS statistical software (IBM version 21) Results We identified 63 patients who received both azacitidine and LEN as first and second line where 37 patients were in group 1 (LEN 1st line) and 26 patients were in group 2 (LEN 2nd line). Baseline characteristics between the two groups are summarized in Table-1. There were no statistically significant differences between the 2 groups in terms of mean age at diagnosis, gender, WHO subtype, revised IPSS, or mean blood counts. The majority of patients had refractory cytopenia with multilineage dysplasia (RCMD) and had low risk revised IPSS . The rate of HI-E was 38% (n=14) among LEN 1st line group compared to 12% (n=3) in LEN 2nd line group. (p=0.04). There was no difference in overall survival (OS) among the two groups with a median OS of 104 months and 87 months, respectively, p=0.55. There was no difference in AML transformation rate, 5.4% (n=2) and 11% (n=3) among the two groups, respectively, p=0.33. There were no differences in response rates to azacitidine among the two groups. Among the Len 1st line group response to 2nd line azacitidine was 38% (n=14) compared to 35% (n=9) among those who received azacitidine as first line followed by LEN as 2nd line. (p=0.69). Conclusion LEN yields a higher rate of HI-E in non-del 5q lower risk MDS when used as first line therapy. If validated in a larger cohort, LEN should be considered for 1st line therapy after ESAs rather than after azacitidine failure. Responses to azacitidine were similar among the two groups, indicating no adverse effect of LEN on azacitidine response. Disclosures: Komrokji: Celgene: Research Funding, Speakers Bureau. Off Label Use: use of lenalidomide in non del 5q. Lancet:Celgene: Research Funding. List:Celgene: Research Funding.

Description: Abstract 292 Background: Allelic deficiency for the RPS14 gene impairs differentiation and survival of erythroid progenitors in del(5q) MDS (Nature 2008; 451:335). Nucleolar stress arising from disruption of ribosome assembly fosters MDM2 sequestration by free ribosome components resulting in p53 stabilization and erythroid hypoplasia (Nat Cell Biol 2009; 11:501). We recently reported that reduced gene dosage of the lenalidomide (LEN) inhibitable, haplodeficient phosphatases CDC25C and PP2Acα is a key determinant of drug sensitivity in del(5q) MDS (PNAS 2009; 106: 12974). We now show that shRNA suppression of these genes to levels commensurate with haplodeficiency reinforces p53 accumulation, and that treatment with LEN promotes MDM2-mediated p53 degradation to transition del(5q) clones to G2/M arrest. We hypothesized that emergence of resistance to LEN in del(5q) MDS arises from two possible mechanisms: (1) up-regulation of haplodeficient drug targets or compensatory isotypes, or (2) inactivating mutations of the TP53 or CDC25C genes. Methods: To investigate mechanisms of LEN resistance, we studied sequential bone marrow (BM) specimens obtained at baseline (BL), response to treatment (TR) and treatment failure (TF) from 12 LEN treated patients with Low/INT-1 risk, transfusion-dependent del(5q) MDS. Eleven patients achieved clonal suppression and transfusion independence; 7 patients developed clinical drug resistance with primary clonal recovery. Immunohistochemical (IHC) staining for cdc25-C, -A and -B; PP2A–Ca and p53 were performed using a biotin-streptavidin-horseradish peroxidase method and compared to 6 age-matched controls; intensity of cytoplasmic or nuclear staining in hematopoietic elements was recorded after blinded review. DNA and RNA were extracted from cryopreserved BM mononuclear cells (BM-MNC) or fixed paraffin blocks from BM clot and biopsy sections. Expression of CDC25C splice variants was assessed by RT-PCR and total gene expression by real time (QT)-PCR. Exonic DNA encoding the catalytic [exons 8–14] and nuclear export domains [exon 11] of CDC25C and the DNA-binding domain of TP53 [exons 4–9] was sequenced for gene mutation analysis. Differences in mean values were compared by paired t-test. Results: P53 immunostaining was significantly higher in del(5q) BL specimens compared to controls ( relative expression [RE] 9.6 vs. 0.25; P =0.007). An admixture of nuclear and cytoplasmic staining for p53 and each cdc25 isotype was observed at BL that was largely restricted to erythroid precursors, whereas at TR cdc25-C and -A expression was primarily cytoplasmic, consistent with drug-induced nuclear exclusion. At TR, RE of only cdc25C (BL, 75 vs. TR, 49; P=0.05) and PP2A (29.2 vs. 12.3; P=0.025) was significantly reduced; whereas at TF cdc25C (TR, 43 vs. TF, 166; P=0.003), cdc25A (42.4 vs. 150; P=0.006), PP2A (7.3 vs. 65.6; P=0.028) and p53 (0.92 vs. 25.4; P=0.024) RE significantly increased. Nuclear localization of cdc25C and p53 but not cdc25A predominated at TF, consistent with escape from cdc25C inhibition. QT-PCR confirmed transcriptional up-regulation of CDC25C at TF with a mean 8.8-fold increase in gene expression vs. BL. DNA sequencing revealed no acquisition of somatic mutations within the CDC25C and TP53 exons studied [n=5]. Conclusions: Secondary resistance to LEN in del(5q) MDS is associated with over-expression and activation of the haplodeficient drug-inhibitable phosphatases, cdc25C and PP2A, with consequent restoration of wt-p53 activation. Absence of gene mutations within the coding exons analyzed suggests that transcriptional compensation alone is responsible for drug resistance. Novel agents targeting transcriptional repression of CDC25C may restore LEN sensitivity and merit investigation in drug resistant del(5q) MDS. Disclosures: List: Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Komrokji:Celgene: Research Funding, Speakers Bureau. Lancet:Celgene: Research Funding. Maciejewski:Esai: Membership on an entity's Board of Directors or advisory committees; Celgene: Speakers Bureau. Sekeres:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

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: Farnesyltransferase inhibitors (FTI) make up a novel class of anti-cancer agents that competitively and selectively inhibit farnesyl protein transferase. Early trials of the orally bioavailable non-peptidomimetic FTI tipifarnib (ZARNESTRATM, Johnson & Johnson PRD) demonstrated both clinical responses and excellent tolerability in patients with poor-risk or refractory acute myeloid leukemia (AML). (Karp, et al. Blood97:3361, 2001). We herein report updated results of a multicenter phase 2 trial of tipifarnib in an elderly, previously untreated poor-risk AML population who refused or were deemed unfit for conventional induction chemotherapy. Tipifarnib was administered orally in the outpatient setting at a dose of 600 mg BID for 21 days, followed by a 1–3 week recovery period. Up to 4 cycles of tipifarnib were permitted in patients with complete responses (CR). The primary endpoint was overall response rate (CR + PR). Secondary endpoints included toxicity rates, measurement of markers of farnesylation (HDJ-2) in bone marrow cells, measurement of signaling intermediates ERK and AKT, and RNA microarray expression patterns. Accrual to the trial is complete. 170 patients have been enrolled, 148 of whom are evaluable for response (AML=160; high-risk MDS=4; high-risk CMML=6). The median age was 73 years (range 34–85), and 76 patients (45%) were age = 75. M/F ratio was 2:1. An unfavorable karyotype and/or antecedent MDS was present in 47% and 79% of patients, respectively. The median number of cycles received was 1, and the median number of days of drug received was 36 days. Dose reductions were implemented in 38% of patients, more commonly in cycles subsequent to cycle #1. The overall response rate (CR + PR) was 34%. CR occurred in 18% of patients. Responses were evenly distributed across study centers. In patients ≥ 75 years, the overall response rate was 30% (CR 20 %). Median CR duration was 6.4 months (range 1.5–11+ months). Median overall survival was 5.6 months for all patients. CR patients had a median survival of 14.4 months, with 63% alive at 12 months. In non-responders, median survival was 3.1 months. The incidence of grade = 3 tipifarnib-related non-hematologic adverse events was 43%, comprised mainly of infectious and gastrointestinal complications. The hospitalization rate for tipifarnib-related toxicity was 18% (median duration: 12 days). The death rate from tipifarnib-related toxicity at 6 weeks was 5%. Microarray analysis of pre-and post-treatment bone marrow samples is being performed to identify both predictive and pharmacodynamic gene markers of response to tipifarnib. In summary, tipifarnib is a novel outpatient treatment with activity in previously untreated poor-risk AML. The low hospitalization rate may reflect the low incidence of severe non-hematological toxicity.