ALBERT

Description: Background: Luspatercept is a first-in-class erythroid maturation agent that binds TGF-β superfamily ligands to reduce aberrant Smad2/3 signaling and enhance late-stage erythropoiesis. The phase 3 MEDALIST trial evaluated luspatercept in pts with RBC transfusion-dependent, IPSS-R-defined very low-, low-, and intermediate-risk MDS with ring sideroblasts (RS+) who were refractory, intolerant, or ineligible to receive erythropoiesis-stimulating agents. This study explored associations of gene mutations, as analyzed by next-generation sequencing (NGS), with response to luspatercept, as well as dynamics of gene mutations on therapy in MEDALIST pts. Methods: DNA was isolated from bone marrow (BM) mononuclear cells from 222 of 229 pts enrolled in the study (148 luspatercept, 74 placebo) at screening and, when available, following treatment. NGS of 23 MDS-relevant genes was performed at screening and every 24 weeks; mean coverage was 1,000-fold and the variant allele frequency (VAF) cutoff was ≥ 1%. BM cell populations were analyzed by cytomorphology. Response criterion of RBC transfusion independence (RBC-TI) of ≥ 8 weeks within the first 24 weeks of treatment was used for correlative analyses. Results: Mutations in SF3B1 were found in 91.0% of pts analyzed at screening (median VAF 42%, range 6-71%), consistent with the study population being RS+. Overall, a median of 2 (range 0-5) of the 23 MDS-relevant genes analyzed were mutated per pt. In addition to SF3B1, the most frequently mutated genes were TET2 (41.9%), DNMT3A (18.9%), ASXL1 (13.1%), and SRSF2 (8.1%). Mutation profiles were similar to those found in previous studies of refractory anemia with RS (RARS; Malcovati L, et al. Blood. 2015;126:233-41) and balanced between luspatercept and placebo arms. Numbers of mutated genes at baseline were distributed similarly in luspatercept responders (R) and non-responders (NR) (Figure A), and comparable response rates were achieved irrespective of number of mutations, with response rates of 36.4%, 34.9%, 42.4%, and 33.3% for pts with 1 mutation, 2 mutations, 3 mutations, and 4 or 5 mutations in the 23 MDS-relevant genes analyzed, respectively. Response to luspatercept was independent of the presence of mutations in any of the genes analyzed individually (Figure B) or when grouped by functional categories (e.g. spliceosome, epigenetic regulation, transcription factor, etc.) (Figure C). Circos plots of co-occurring mutations showed similar mutation profiles in R and NR (Figure D). Response rates were also similar regardless of baseline SF3B1 allelic burden (R: 43%, NR: 42%; P = 0.11). At baseline, BM erythroid precursors were higher in R (R: 32.8%, NR: 26%; P = 0.008; while R and NR had similar levels of RS+ cells [R: 80%, NR: 84%; P = 0.25], Figure E), consistent with the postulated activity of luspatercept on the erythroid lineage. When comparing the frequency of mutation changes in luspatercept- vs placebo-treated pts at week 24 of the study, no statistically significant differences were observed in the frequency of newly acquired mutations (13/126 [10.3%] pts in luspatercept vs 8/64 [12.5%] pts in placebo, P = 0.63) or mutation losses (4/126 [3.2%] in luspatercept vs 5/64 [7.8%] in placebo, P = 0.17). Evaluation of changes in allele burden (median VAF at week 24 vs baseline) for mutations in genes associated with adverse prognosis (ASXL1, SRSF2, U2AF1, NRAS, IDH2, GATA2, TP53, RUNX1, and EZH2; Bejar R. Curr Opin Hematol. 2017;24:73-8) showed no change between luspatercept- or placebo-treated pts (1.01-fold, n = 58 and 0.95-fold, n = 19, respectively, P = 0.69). Conclusions: Pts enrolled in the MEDALIST study had mutations consistent with RS+, lower-risk MDS with a preponderance of SF3B1 mutations; genes associated with poor prognosis (and other genes) were balanced between study arms. RBC-TI responses with luspatercept were achieved regardless of SF3B1 allelic burden, number of baseline mutations, and presence of individual mutations, including adverse mutations, or co-mutations. Disclosures Platzbecker: Abbvie: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Dunshee:Celgene Corporation: Employment, Equity Ownership. Komrokji:DSI: Consultancy; pfizer: Consultancy; Agios: Consultancy; JAZZ: Consultancy; Novartis: Speakers Bureau; Incyte: Consultancy; celgene: Consultancy; JAZZ: Speakers Bureau. Mufti:Cellectis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Garcia-Manero:Celgene: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding; Amphivena: Consultancy, Research Funding; Helsinn: Research Funding; Novartis: Research Funding; AbbVie: Research Funding. Buckstein:Celgene: Consultancy, Honoraria, Research Funding; Takeda: Research Funding. Santini:Celgene Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Honoraria; Acceleron: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Menarini: Membership on an entity's Board of Directors or advisory committees. Díez-Campelo:Celgene Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Sekeres:Millenium: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. See:Celgene Corporation: Other: Contractor. Tsai:Celgene Corporation: Employment. Risueño:Celgene Corporation: Employment, Equity Ownership, Patents & Royalties: Named in Celgene patent filings related to predictive patient response biomarkers in hematological malignancies. Ma:Celgene Corporation: Employment, Equity Ownership. Schwickart:Celgene Corporation: Employment, Equity Ownership. Rampersad:Celgene Corp: Employment, Equity Ownership. Zhang:Celgene Corporation: Employment, Equity Ownership. Laadem:Celgene Corporation: Employment, Equity Ownership. Menezes:Celgene Corporation: Employment, Equity Ownership. MacBeth:Celgene Corporation: Employment, Equity Ownership. Linde:Acceleron Pharma: Employment, Equity Ownership; Abbott Laboratories, Inc.: Equity Ownership; Fibrogen, Inc.: Equity Ownership. Reynolds:Acceleron Pharma: Employment, Equity Ownership. List:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Fenaux:Celgene Corporation: Honoraria, Research Funding; Astex: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Aprea: Research Funding. OffLabel Disclosure: Luspatercept is an investigational therapy that is not approved for any use in any country. Luspatercept is currently being evaluated for potential use in patients with anemia due to myelodysplastic syndromes, beta-thalassemia, or myelofibrosis.

Description: Abstract 2871 Deletion at 13q14 (13q) is the most common genomic aberration in CLL. It is present in more than 50% of cases, and is the sole documented cytogenetic abnormality in 36% of the patients. These latter cases are known to have a more favorable clinical course. However, recent data from our group and others, suggest that patients with CLL and 13q deletion as the only FISH abnormality could have a different outcome depending on the number of cells displaying this aberration. Thus CLL patients with a high number of 13q cells usually had both shorter overall survival and shorter time to first therapy. However, to the best of our knowledge the molecular characteristics of these patients have not been so far analyzed in detail. A total of 102 samples were selected for the study, 32 of which served as a validation cohort. A complete immunophenotypic analysis by flow cytometry and FISH studies were carried out in all cases. The median age was 68 years (range, 35 to 90 years). For the purpose of the study, only samples with one cytogenetic abnormality were included. For the gene expression profile analysis, according to our previous results, two groups of patients with 13q were compared: those in whom 80% or more of cells showed 13q (13qH) and those in whom fewer than 80% of cells showed 13q losses (13qL). The distribution of cases in the study cohort was: 13qH (n=25; 36%), 13qL (n=27; 39%), normal FISH (nCLL, n=8; 11%) and 17p/11q (n= 10; 14%); and in the validation cohort: 13qH (n=7; 22%), 13qL (n=11; 34%) and nCLL (n=9; 28%). Peripheral blood mononuclear cells (PBMCs) were isolated from fresh peripheral blood samples using Ficoll gradient, snapfrozen and stored at 80°C. For the validation cohort, CD19positive B cells were purified by magnetically activated cell sorting (MACS) CD19 MicroBeads resulting in a 〉98% purity, as analyzed by flow cytometry. CD19positive normal B cells from peripheral blood of five healthy donors served as controls. All samples were hybridized with the Affymetrix Human Exon arrays 1.0 ST. A total of 3 450 genes significantly distinguished 13qH from 13qL patients, defining the 13qH signature. To determine the biological significance of the deregulated genes, a further analysis was carried out, revealing that apoptosis, BCR and NFkB signaling were the most significant affected pathways in 13qH CLL patients. Moreover, 13qH CLL patients were also characterized by a striking overrepresentation of deregulated miRNAs. A total of 15 miRNAs were deregulated in 13qH relative to 13qL patients. HsamiR155 was the most highly upregulated miRNA (Rfold=3.70), while hsamiR223 was the most significantly downregulated (Rfold=0.10). The posttranscriptional regulatory network of miRNA and genes in CLL patients with more than 80% of 13q cells was carried out by analyzing the miRNAmRNA relationships and the pathway analysis demonstrated that B cell receptor signaling, PI3K signaling and NFkB signaling were among the most strongly affected pathways in 13qH patients, highlighting the importance of miRNA regulation in CLL. The influence of other factors with prognostic relevance in CLL, such as IGVH mutational status, was discarded. We also analyzed the gene signature of CLL high risk cytogenetic subgroups in comparison with 13q patients. Surprisingly, our results suggest that some of the biological characteristics of 13qH CLL patients were similar to those of highrisk cytogenetic subgroups, since they share the deregulation of several key signaling pathways. To validate the differences observed between the subgroups of 13q CLL patients and get a visualization of these, we applied the Principal Component Analysis (PCA) in an independent series of patients. The expression pattern of CD19+ cells from CLL patients was notably different from the gene expression profile of CD19+ cells from healthy donors. Thus, CLL patients with a high number of 13q cells can be differentiated based on their expression profile. By contrast, the gene expression of B lymphocytes from 13qL and normal FISH subgroups was similar. Therefore, this study provides new evidences regarding the heterogeneity of 13q deletion in CLL patients. Thus an overexpression of BCR and NFKB patways and as well as a deregulation of the balance between the proliferative and apoptotic signals and miRNA expression are involved in cases with higher percentages of 13q- cells. Disclosures: No relevant conflicts of interest to declare.

Description: Treatment options for relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) are limited with no standard of care; prognosis is poor, with 4- to 6-month median survival. Avadomide (CC-122) is a cereblon-modulating agent with immunomodulatory and direct antitumor activities. This phase 1 dose expansion study assessed safety and clinical activity of avadomide monotherapy in patients with R/R de novo DLBCL and transformed lymphoma. Additionally, a novel gene expression classifier, which identifies tumors with a high immune cell infiltration, was shown to enrich for response to avadomide in R/R DLBCL. Ninety-seven patients with R/R DLBCL, including 12 transformed lymphoma, received 3 to 5 mg of avadomide administered on continuous or intermittent schedules until unacceptable toxicity, disease progression, or withdrawal. Eighty-two patients (85%) experienced ≥1 grade 3/4 treatment-emergent adverse events (AEs), most commonly neutropenia (51%), infections (24%), anemia (12%), and febrile neutropenia (10%). Discontinuations because of AEs occurred in 10% of patients. Introduction of an intermittent 5/7‑day schedule improved tolerability and reduced frequency and severity of neutropenia, febrile neutropenia, and infections. Among 84 patients with de novo R/R DLBCL, overall response rate (ORR) was 29%, including 11% complete response (CR). Responses were cell-of-origin-independent. Classifier-positive DLBCL patients (de novo) had an ORR of 44%, median progression-free survival (mPFS) of 6 months, and 16% CR versus an ORR of 19%, mPFS of 1.5 months, and 5% CR in classifier-negative patients (P = .0096). Avadomide is being evaluated in combination with other antilymphoma agents. This trial was registered at www.clinicaltrials.gov as #NCT01421524.

Description: Approximately 8% to 19% of patients with acute myeloid leukemia (AML) have isocitrate dehydrogenase-2 (IDH2) mutations, which occur at active site arginine residues R140 and R172. IDH2 mutations produce an oncometabolite, 2-hydroxyglutarate (2-HG), which leads to DNA and histone hypermethylation and impaired hematopoietic differentiation. Enasidenib is an oral inhibitor of mutant-IDH2 proteins. This first-in-human phase 1/2 study evaluated enasidenib doses of 50 to 650 mg/d, administered in continuous 28-day cycles, in patients with mutant-IDH2 hematologic malignancies. Overall, 214 of 345 patients (62%) with relapsed or refractory (R/R) AML received enasidenib, 100 mg/d. Median age was 68 years. Forty-two patients (19.6%) attained complete remission (CR), 19 patients (10.3%) proceeded to an allogeneic bone marrow transplant, and the overall response rate was 38.8% (95% confidence interval [CI], 32.2-45.7). Median overall survival was 8.8 months (95% CI, 7.7-9.6). Response and survival were comparable among patients with IDH2-R140 or IDH2-R172 mutations. Response rates were similar among patients who, at study entry, were in relapse (37.7%) or were refractory to intensive (37.5%) or nonintensive (43.2%) therapies. Sixty-six (43.1%) red blood cell transfusion–dependent and 53 (40.2%) platelet transfusion–dependent patients achieved transfusion independence. The magnitude of 2-HG reduction on study was associated with CR in IDH2-R172 patients. Clearance of mutant-IDH2 clones was also associated with achievement of CR. Among all 345 patients, the most common grade 3 or 4 treatment-related adverse events were hyperbilirubinemia (10%), thrombocytopenia (7%), and IDH differentiation syndrome (6%). Enasidenib was well tolerated and induced molecular remissions and hematologic responses in patients with AML for whom prior treatments had failed. The study is registered at www.clinicaltrials.gov as #NCT01915498.

Description: The authors report a phase 1 study of romidepsin combined with oral 5-azacytidine in patients with relapsed/refractory lymphomas, including complete remissions in 3 patients with angioimmunoblastic T-cell lymphoma.

Description: Diffuse large B-cell lymphoma is a heterogeneous disease, commonly described by cell-of-origin (COO) molecular subtypes. We sought to identify novel patient subgroups through an unsupervised analysis of a large public dataset of gene expression profiles from newly diagnosed de novo DLBCL patients, yielding two biologically distinct subgroups characterized by differences in the tumor microenvironment. Pathway analysis and immune deconvolution algorithms identified higher B-cell content and a strong proliferative signal in subgroup A and enriched T-cell, macrophage, and immune/inflammatory signals in subgroup B, reflecting similar biology to published DLBCL stratification research. A gene expression classifier, featuring 26 gene expression scores, was derived from the public dataset to discriminate subgroup A (classifier-negative, immune-low) and subgroup B (classifier-positive, immune-high) patients. Subsequent application to an independent series of diagnostic biopsies and replicated the subgroups with immune cell composition confirmed via immunohistochemistry. Avadomide, a CRL4CRBN E3 ubiquitin ligase modulator, demonstrated clinical activity in relapsed/refractory DLBCL patients, independent of COO subtypes. Given the immunomodulatory activity of avadomide and need for a patient selection strategy, we applied the gene expression classifier to pretreatment biopsies from relapsed/refractory DLBCL patients receiving avadomide (NCT01421524). Classifier-positive patients demonstrated an enrichment in response rate and progression-free survival of 44% and 6.2 months versus 19% and 1.6 months for classifier-negative patients (HR=0.49 [0.280, 0.86]; P=.0096). The classifier was not prognostic for R-CHOP or salvage immunochemotherapy. The classifier described here discriminates DLBCL tumors based on tumor and non-tumor composition and has potential utility to enrich for clinical response to immunomodulatory agents including avadomide.

Description: BACKGROUND: CC-486, a DNA hypomethylating agent and epigenetic modifier, is an oral formulation of azacitidine (AZA) that is administered at lower exposures for extended durations (300 mg/day [d] for 14 or 21d/28d cycle) compared with the injectable formulation of AZA, which is given in a high exposure, limited duration regimen of 75mg/m2 for 7d/28d cycle. AZA induces DNA damage and cytotoxicity, and promotes changes in gene expression leading to cellular differentiation. As DNA incorporation of AZA is S-phase-dependent, it has been hypothesized that extended dosing with CC-486 prolongs drug exposure and DNA incorporation to enhance epigenetic activity. The mechanism of action imparted by extended dosing schedules of CC-486 is not fully understood. In patients with myeloid malignancies, DNA hypomethylation in blood is sustained throughout the 28d Tx cycle with extended CC-486 dosing regimens (Laille, 2015; Garcia-Manero, 2016). To better understand the mechanism of CC-486, we assessed the kinetics of expression of myeloid markers of cellular differentiation and cytotoxicity with various AZA dosing schedules in in vitro and in vivo models of AML. METHODS: AML cell lines (AML-193, KG1a, and MV4-11) were treated in vitro with AZA (0.05 - 5 µM daily for 5d or 15d), and at cumulative concentrations of 1 or 3 µM administered once or fractionated over 2-5d to experimentally model CC-486 extended exposures: 1 µM cumulative dose (1 µM × 1d, 0.5 µM × 2d, 0.33 µM × 3d, 0.25 µM × 4d, or 0.2 µM × 5d); 3 µM cumulative dose (3 µM × 1d, 1.5 µM × 2d, 1 µM × 3d, 0.75 µM × 4d, or 0.6 µM × 5d). AZA- or vehicle-treated cells were analyzed by flow cytometry, DNA methylation (Illumina Infinium EPIC assay), and RNA-Seq. Temporal expression of CD11b was assessed as a surface marker of myeloid differentiation, and Annexin-V staining was used to determine the extent of apoptosis and cell death. In efficacy studies, mouse models of AML (syngeneic, cell line-derived xenografts) were treated intraperitoneally with AZA regimens at 1 mg/kg/d × 15d (extended) or 3 mg/kg/d x 5d. RESULTS: Tx of AML-193 cells with 0.05 - 5 µM daily AZA led to upregulation of markers of myeloid differentiation (including CD11b) at lower doses, and a dose-dependent increase in apoptosis up to 7d after Tx initiation. Following Tx with 1 µM AZA for 1d, maximal cellular differentiation (ie, CD11b expression) occurred at d3 in 30% of AML-193 cells; conversely, cells treated with 0.2 µM/d AZA for 5d showed greater differentiation (40%) peaking on d7 (Fig A). CD11b expression was increased upon each subsequent cell division; after 5 cell divisions, CD11b upregulation was 4-fold higher in cells treated with multiple, lower AZA doses than with 1 µM AZA administered for 1d (Fig B). CD11b upregulation was not observed in the absence of cell division under serum starvation conditions for 3d (to induce cell cycle arrest), further suggesting that cell division is a requirement for AZA-induced CD11b changes (Fig C). Similarly, AML-193 cells treated with a 3 µM cumulative AZA dose over 1, 2, 3, 4, or 5d showed greater changes in myeloid differentiation marker expression, with peak apoptosis at d7 with extended dosing regimens (Fig D). In KG1a and MV4-11 cells, Tx with 1 µM AZA QD for 5d led to induction of myeloid differentiation by d7, and cell death (followed by recovery of undifferentiated cells) by d28. In contrast, daily Tx with 0.3 µM AZA for 15d led to slower, more robust upregulation of differentiation markers, peaking at d21 and accompanied by a gradual loss of cell viability. Extended AZA exposure to cells led to pronounced changes in gene expression (Fig E) and DNA methylation (Fig F) at both d7 (immune response gene signature) and d28 (cell adhesion gene signature) compared with limited duration exposure AZA. In mice, low exposure, extended regimens of AZA exhibited higher DNA and RNA incorporation into peripheral blood mononuclear cells (PBMCs) and bone marrow cells when compared with higher exposure, limited duration regimens. Extended AZA dosing led to significant efficacy in murine AML models. CONCLUSIONS: In AML cell lines, low exposure, extended duration AZA schedules modeling CC-486 induced robust changes in differentiation. These results suggest that CC-486-mediated effects using extended exposure regimens preferentially promote a differentiation effect and cell death of AML tumor cells. These mechanistic insights may help inform rational CC-486 combination Tx strategies. Disclosures Dunshee: Bristol Myers Squibb: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Genentech Inc.: Current Employment, Current equity holder in publicly-traded company. Dai:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Jang:Bristol Myers Squibb: Ended employment in the past 24 months. Risueño:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties: Named in BMS (before Celgene) patent filings related to predictive patient response biomarkers in hematological malignancies. Jeyaraju:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Hagner:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. See:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. MacBeth:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Wang:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. La Torre:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Skikne:Bristol Myers Squibb: Current Employment. Beach:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Kumar:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Thakurta:Oxford University: Other: visiting professor; Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Lopes de Menezes:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company.

Description: Introduction: LR-MDS are characterized by ineffective erythropoiesis that leads to anemia and red blood cell (RBC) transfusion dependence. Luspatercept is a first-in-class erythroid maturation agent that binds to select TGF-β superfamily ligands and enhances late-stage erythropoiesis. MEDALIST is a phase 3, randomized, double-blind, placebo-controlled trial to evaluate the safety and efficacy of luspatercept in pts with LR-MDS (IPSS-R-defined Very low-, Low-, and Intermediate-risk) with ring sideroblasts who required RBC transfusions and were ineligible for, intolerant of, or refractory to erythropoiesis-stimulating agents. Clinical benefit (CB; defined as RBC transfusion independence [RBC-TI] ≥ 8 weeks and/or modified hematologic improvement-erythroid [mHI-E] per IWG 2006 criteria) in the primary MEDALIST treatment phase (Weeks 1-24) was achieved by 58.2% of pts in the luspatercept arm and 21.1% in the placebo arm (P 〈 0.0001). The objective of the study was to investigate the effect of luspatercept treatment on erythropoiesis biomarkers and their relationship to CB in the primary MEDALIST treatment phase (Weeks 1-24). Methods: In the MEDALIST trial, 229 pts were randomized to receive either luspatercept (N = 153) or placebo (N = 76). Reticulocyte count was determined in blood samples collected at baseline and during the primary treatment phase. Serum biomarkers (soluble transferrin receptor 1 [sTfR1], erythroferrone [ERFE], and erythropoietin [EPO]) were measured by ELISA. Bone marrow (BM) erythroid precursors (EP) were determined by cytomorphology from BM aspirates. Biomarker levels were compared between baseline and Week 25 within treatment arms and between pts with CB and without CB in the luspatercept arm using a paired 2-tailed t-test and unpaired t-test (parametric method). Results: In the luspatercept arm, mean reticulocyte count increased from baseline, starting at 8 days after first dose (55.1 vs 34.5 × 109/L at baseline, P 〈 0.0001), and remained elevated throughout the evaluation period (Figure). Mean EPO levels increased significantly within 6 weeks after first dose (440.1 vs 220.4 IU/L at baseline, P 〈 0.0001) and remained elevated up to Week 25. Similarly, levels of sTfR1 (P 〈 0.0001), ERFE (P 〈 0.0001), and EP (P = 0.0010) were elevated at Week 25 relative to baseline (Table). The mean transfusion burden (within 16 weeks) was significantly reduced at Week 25 compared with baseline (7.2 vs 11.0 units, P 〈 0.0001). In contrast, in the placebo arm, reticulocyte count, EPO levels, and 16-week transfusion burden remained largely unchanged, while levels of sTfR1 (P 〈 0.0001), ERFE (P = 0.0431), and EP (P = 0.0010) were significantly lower at Week 25 relative to baseline. In the luspatercept arm, mean baseline EP were higher in 87 pts with CB (31.3%) compared with 63 pts without CB (26.5%; P = 0.0298). No statistically significant differences in baseline EPO, ERFE, sTfR1, reticulocyte count, and 16-week transfusion burden were observed in either group. At Week 25, pts with luspatercept and CB had a significantly greater increase of reticulocyte count (2.7 vs 1.8 mean fold increase from baseline, P = 0.0017), but not EPO levels (2.9 vs 4.3 mean fold increase from baseline, P = 0.1370) compared with pts without CB. Changes in erythropoiesis-related biomarkers (EP, ERFE, and sTfR1) did not differ significantly between pts with and without CB. To investigate whether luspatercept affects erythroid maturation, the ratio of reticulocyte/sTfR1 was calculated. This ratio was reasoned to be an approximation of the ratio of late-stage erythropoiesis (reticulocytes) within total erythropoiesis (sTfR1). Luspatercept increased the mean ratio of reticulocyte/sTfR1 in pts with CB (2.2 in Week 25 vs 1.5 at baseline, P 〈 0.0001) and no CB (1.9 in week 25 vs 1.3 at baseline, P = 0.0071). Conclusions: Luspatercept-treated pts in the MEDALIST trial had an increase of erythropoiesis-associated biomarkers. Luspatercept-mediated CB (RBC-TI ≥ 8 weeks and/or mHI-E) was associated with increased blood reticulocyte counts and was higher in pts with expanded BM erythropoiesis (as measured by EP) at baseline. Together with the observation that the ratio of reticulocytes/sTfR1 increased during luspatercept treatment, this suggests that the luspatercept mechanism of efficacy in pts with LR-MDS is associated with an increase of erythroid maturation and reticulocytes. Disclosures Platzbecker: Novartis: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Geron: Consultancy, Honoraria; Amgen: Honoraria, Research Funding. Zhu:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Ha:Bristol Myers Squibb: Current Employment. Risueño:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties: Named in BMS (before Celgene) patent filings related to predictive patient response biomarkers in hematological malignancies. Chan:Bristol Myers Squibb: Current Employment. Zhang:BMS: Current Employment. Dunshee:Bristol Myers Squibb: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Genentech Inc.: Current Employment, Current equity holder in publicly-traded company. Acar:Bristol Myers Squibb: Ended employment in the past 24 months. Shetty:BMS: Current Employment, Current equity holder in publicly-traded company. Ito:BMS: Current Employment, Current equity holder in publicly-traded company. MacBeth:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Santini:Menarini: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Acceleron: Consultancy; Novartis: Consultancy, Honoraria; Johnson & Johnson: Honoraria; BMS: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees. Garbowski:Imara: Consultancy; Vifor Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees. Fenaux:BMS: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Schwickart:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company.

Description: BACKGROUND: In newly diagnosed AML, high remission rates are typically achieved with IC, but the response is often transient, and detectable residual disease in the bone marrow post-chemotherapy is predictive of early relapse. Emerging data show that the identification of ≥ 0.1% MRD by multiparameter flow cytometry (MFC) in patients with AML in remission after IC is an important prognostic marker that may help guide treatment (Tx) decisions. CC-486 is an oral hypomethylating agent that allows for extended dosing schedules to prolong drug exposure over the Tx cycle. In the QUAZAR AML-001 Maintenance Trial, Tx with CC-486 300 mg QD for 14 days/28-day Tx cycle was associated with significantly improved overall (OS) and relapse-free survival (RFS) vs. placebo (PBO) in patients (pts) with AML in first remission after induction chemotherapy ± consolidation. Samples for MFC were obtained prior to randomization and serially throughout the study to assess the impact of MRD on OS and RFS, and to evaluate rates of conversion from MRD positivity (+) to negativity (-) in the CC-486 and PBO arms. METHODS: Eligible pts aged ≥ 55 years with AML were randomized 1:1 to CC-486 300 mg or PBO within 4 months of achieving first complete remission (CR) or CR with incomplete blood count recovery (CRi). MFC assessments of bone marrow aspirates were performed centrally at screening; at cycles 3, 6, 9, 12, 15, 18, 21, 24, 30, and 36; and as clinically indicated. Samples were analyzed with a panel of 22 cell surface markers using an MRD+ cutoff of ≥ 0.1% (per ELN MRD guidelines). For pts MRD+ at baseline (BL; ie, at randomization), an MRD response was defined as achievement of MRD- for ≥ 2 consecutive assessments. MRD- duration was calculated from the time of randomization (for pts MRD- at BL) or from the first of ≥ 2 consecutive MRD- tests (for pts MRD+ at BL), until the last MRD- assessment (for pts who became MRD+) or Tx discontinuation. OS, RFS, and MRD- durations were estimated using Kaplan-Meier methods. Multivariate (MV) Cox regression analyses were performed to evaluate the association of BL MRD status (MRD+ vs. MRD-) and randomized Tx arm (CC-486 vs. PBO) with OS and RFS. RESULTS: The MRD-evaluable cohort comprised 463/472 randomized pts (98.1%; CC-486, n=236; PBO, n=227) who had samples available for evaluation at BL and at ≥ 1 post-BL visit. At BL, 43% of pts (n=103) in the CC-486 arm and 50% (n=116) in the PBO arm were MRD+. Overall, BL characteristics were similar between MRD+ and MRD- pts: median ages were 69 (range 55-84) and 68 (55-86) years, respectively; 84% and 88% had intermediate-risk cytogenetics at diagnosis; 52% and 46% of pts had an ECOG PS of 0; and 79% and 82% received ≥ 1 cycle of consolidation after induction. CC-486 Tx resulted in improved OS from time of randomization compared with PBO in pts who were either MRD+ (median 14.6 vs. 10.4 mo, respectively; HR 0.69 [95%CI 0.51, 0.93]) or MRD- (median 30.1 vs. 24.3 mo; HR 0.81 [0.59, 1.12]) at BL. Median RFS was also extended with CC-486 vs. PBO for both MRD+ (7.1 vs. 2.7 mo, respectively; HR 0.58 [95%CI 0.43, 0.78]) and MRD- pts (13.4 vs. 7.8 mo; HR 0.71 [0.52, 0.98]). In MV analyses, BL MRD status (MRD+ vs. MRD-) was significantly associated with OS (HR 1.85; P 〈 0.0001) and RFS (HR 2.04; P 〈 0.0001), and CC-486 showed a significant Tx benefit vs. PBO on both OS (HR 0.74; P = 0.0067) and RFS (HR 0.63; P 〈 0.0001) independent of MRD status at BL (Figure). The median duration of MRD negativity was extended with CC-486 vs. PBO: 11.0 vs. 5.0 mo, respectively (HR 0.62 [95%CI 0.48, 0.78]). Tx with CC-486 also resulted in a higher rate of MRD response (MRD+ to MRD-) vs. PBO: 37% vs. 19%, respectively. Among MRD responders, 9/38 patients (24%) in the CC-486 arm achieved MRD negativity 〉 6 mo after randomization, compared with only 1/22 patients (5%) in the PBO arm. CONCLUSIONS: The QUAZAR AML-001 Maintenance Trial was the first prospective, randomized trial to include long-term longitudinal assessment of MRD in older patients with AML in remission. In both treatment arms, MRD+ status (≥ 0.1%) after induction ± consolidation was associated with significantly shorter OS and RFS compared with MRD- status. Approximately one-fourth of MRD responders treated with CC-486 achieved MRD negativity 〉 6 mo after study entry, suggesting that CC-486 could induce MRD negativity after prolonged MRD+ status. Maintenance Tx with CC-486 substantially improved OS and RFS independent of MRD status at BL. Disclosures Roboz: Otsuka: Consultancy; AstraZeneca: Consultancy; Orsenix: Consultancy; Astellas: Consultancy; Argenx: Consultancy; Actinium: Consultancy; Sandoz: Consultancy; Roche/Genentech: Consultancy; Jazz: Consultancy; Eisai: Consultancy; Celltrion: Consultancy; MEI Pharma: Consultancy; Helsinn: Consultancy; Epizyme: Consultancy; Jasper Therapeutics: Consultancy; Cellectis: Research Funding; Trovagene: Consultancy; Takeda: Consultancy; Astex: Consultancy; Amphivena: Consultancy; Agios: Consultancy; Abbvie: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Bayer: Consultancy; Array BioPharma: Consultancy; Daiichi Sankyo: Consultancy. Ravandi:Abbvie: Consultancy, Honoraria, Research Funding; Xencor: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Macrogenics: Research Funding; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Orsenix: Consultancy, Honoraria, Research Funding. Wei:Pfizer: Honoraria; Bristol Myers Squibb: Honoraria, Research Funding, Speakers Bureau; Janssen: Honoraria; Walter and Eliza Hall Institute of Medical Research: Patents & Royalties: AW is eligible for royalty payments related to venetoclax; Roche: Honoraria; Amgen: Honoraria, Research Funding; Novartis: Honoraria, Research Funding, Speakers Bureau; Abbvie: Honoraria, Research Funding, Speakers Bureau; Servier: Consultancy, Honoraria, Research Funding; Macrogenics: Honoraria; Astra Zeneca: Honoraria, Research Funding. Dombret:Menarini: Consultancy; Janssen: Consultancy; Cellectis: Consultancy; Shire-Baxalta: Consultancy; Immunogen: Consultancy; Otsuka: Consultancy; Abbvie: Consultancy; Astellas: Consultancy; Daiichi Sankyo: Consultancy; Servier: Consultancy, Research Funding; Sunesis: Consultancy; Amgen: Consultancy, Research Funding; Jazz Pharma: Consultancy, Research Funding; Celgene: Consultancy; Nova: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding. Döhner:Astex: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Research Funding; AROG: Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria; GEMoaB: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Oxford Biomedicals: Consultancy, Honoraria; Sunesis: Research Funding; Pfizer: Research Funding; Roche: Consultancy, Honoraria; Jazz: Consultancy, Honoraria, Research Funding; Helsinn: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria, Research Funding. Thol:Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees. Voso:Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Porkka:Novartis: Consultancy, Honoraria, Research Funding; BMS/Celgene: Honoraria, Research Funding. La Torre:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Skikne:Bristol Myers Squibb: Current Employment. Kumar:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Dong:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Beach:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Risueño:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties: Named in BMS (before Celgene) patent filings related to predictive patient response biomarkers in hematological malignancies. Lopes de Menezes:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Ossenkoppele:Novartis: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Roche: Consultancy; J&J: Consultancy, Research Funding; Agios: Consultancy; Jazz: Consultancy; Astellas: Consultancy; Daiichi Sayko: Consultancy; Amgen: Consultancy.