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International audience; Whether the LSC17 gene expression can improve risk stratification in the context of NGS-based risk stratification and measurable residual disease (MRD) in AML patients treated intensively has not been explored. We analyzed LSC17 in 504 adult patients prospectively treated in the ALFA-0702 trial. Multiple (cyto)genetic alterations were associated with changes in LSC17, such as higher LSC17 in patients with RUNX1 or TP53 mutations, and lower scores in those with CEBPA and NPM1 mutations. LSC17-high patients had a lower rate of complete response (CR) or CR with incomplete platelet recovery (CRp) after one induction course in a multivariable analysis (OR=0.41, p=0.0007) accounting for European LeukemiaNet 2022 (ELN22) risk groups, age, and white blood cell (WBC) count. The LSC17-high status was associated with shorter overall survival (OS) (3-year OS: 70.0% versus 52.7% in LSC17-low patients, p

By querying metabolic pathways associated with leukemic stemness and survival in multiple AML datasets, we nominated SLC7A11 encoding the xCT cystine importer as a putative AML dependency. Genetic and chemical inhibition of SLC7A11 impaired the viability and clonogenic capacity of AML cell lines in a cysteine-dependent manner. Sulfasalazine, a broadly available drug with xCT inhibitory activity, had anti-leukemic activity against primary AML samples in ex vivo cultures. Multiple metabolic pathways were impacted upon xCT inhibition, resulting in depletion of glutathione pools in leukemic cells and oxidative stress-dependent cell death, only in part through ferroptosis. Higher expression of cysteine metabolism genes and greater cystine dependency was noted in NPM1-mutated AMLs. Among eight anti-leukemic drugs, the anthracycline daunorubicin was identified as the top synergistic agent in combination with sulfasalazine in vitro. Addition of sulfasalazine at a clinically relevant concentration significantly augmented the anti-leukemic activity of a daunorubicin-cytarabine combination in a panel of 45 primary samples enriched in NPM1-mutated AML. These results were confirmed in vivo in a patient-derived xenograft model. Collectively, our results nominate cystine import as a druggable target in AML and raise the possibility to repurpose sulfasalazine for the treatment of AML, notably in combination with chemotherapy.

Intra-tumor heterogeneity portends poor outcome in many cancers. In AML, a higher number of drivers worsens prognosis. The Shannon Index is a robust metric of clonal heterogeneity that accounts for the number of clones, but also their relative abundance. We show that a Shannon Index can be estimated from bulk sequencing, which is correlated (ρ = 0.76) with clonal diversity from single-colony genotyping. In a discovery cohort of 292 patients with sequencing of 43 genes, a higher number of drivers (HR = 1.18, P = 0.028) and a lower Shannon Index (HR = 0.68, P = 0.048), the latter reflecting clonal dominance, are independently associated with worse OS independently of European LeukemiaNet 2017 risk. These findings are validated in an independent cohort of 1184 patients with 111-gene sequencing (number of drivers HR = 1.16, P = 1 × 10−5, Shannon Index HR = 0.81, P = 0.007). By re-interrogating paired diagnosis/relapse exomes from 50 cytogenetically normal AMLs, we find clonal dominance at diagnosis to be correlated with the gain of a significantly higher number of mutations at relapse (P = 6 × 10−6), hence with clonal sweeping. Our results suggest that clonal dominance at diagnosis is associated with the presence of a leukemic phenotype allowing rapid expansion of new clones and driving relapse after chemotherapy.

Functional precision medicine in AML often relies on short-term in vitro drug sensitivity screening (DSS) of primary patient cells in standard culture conditions. We designed a niche-like DSS assay combining physiologic hypoxia (O2 3%) and mesenchymal stromal cell (MSC) co-culture with multiparameter flow cytometry to enumerate lymphocytes and differentiating (CD11/CD14/CD15+) or leukemic stem cell (LSC)-enriched (GPR56+) cells within the leukemic bulk. After functional validation of GPR56 expression as a surrogate for LSC enrichment, the assay identified three patterns of response, including cytotoxicity on blasts sparing LSCs, induction of differentiation, and selective impairment of LSCs. We refined our niche-like culture by including plasma-like amino-acid and cytokine concentrations identified by targeted metabolomics and proteomics of primary AML bone marrow plasma samples. Systematic interrogation revealed distinct contributions of each niche-like component to leukemic outgrowth and drug response. Short-term niche-like culture preserved clonal architecture and transcriptional states of primary leukemic cells. In a cohort of 45 AML samples enriched for NPM1c AML, the niche-like multiparametric assay could predict morphologically (p = 0.02) and molecular (NPM1c MRD, p = 0.04) response to anthracycline-cytarabine induction chemotherapy. In this cohort, a 23-drug screen nominated ruxolitinib as a sensitizer to anthracycline-cytarabine. This finding was validated in an NPM1c PDX model.

A 77-year-old patient without remarkable past medical history developed in 2016, thrombocytopenia (Platelets 30 G/L), anemia (Hemoglobin 10.8 g/dL), and monocytosis (Monocytes 1.1 G/L) with no peri...

Introduction Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative therapy for sickle cell disease (SCD) allowing a SCD-free survival over 95% among children with matched HLA-identical donor (Gluckman E. Blood, 2017; Bernaudin F. Haematologica, 2020). In adults, myeloablative HSCT is associated with more graft-versus host disease (GVHD) and higher toxicity (Cappelli B. Haematologica, 2019). More recent approaches using non myeloablative (NMA) conditioning regimen (3 gray (Gy) total body irradiation (TBI) plus alemtuzumab) followed by HLA-identical peripheral blood stem cells (PBSC) and post-transplant sirolimus appear safe in adults (Hsieh MM. JAMA, 2014), but incidence of graft failure might be higher than the one reported after myeloablative conditioning (MAC) (Alzahrani M. Br J Haematol, 2021). Here, we compare outcomes after MAC or NMA conditioning regimens in patients over 15 years old transplanted from a matched related donor (MRD). Patients and methods All consecutive patients transplanted for SCD from a MRD from January 2015 to October 2020 were eligible if they were over 15 years old and received a busulfan-based MAC conditioning regimen or a NMA conditioning regimen. Chimerism was studied by analyzing various polymorphisms after polymerase chain reaction (PCR) amplification of DNA obtained from whole blood cells. Rejection was defined as donor chimerism Results Thirty-four patients were included: 20 in the MAC and 14 in the NMA groups. Median age at transplant was 17 years (range 15-46) without difference between groups. Forty four percent of patients had a history of cerebral vasculopathy, 79% of recurrent vaso-occlusive crises and 76% of acute chest syndrome. ABO major incompatibility was present in 15% of patients. There was no difference in patient characteristics according to the conditioning regimen group except for pre-transplant cerebral vasculopathy, more frequently reported in the MAC group: 70% versus 6% in the NMA group (p In the MAC group, conditioning regimen associated busulfan (12.8 mg/kg IV), cyclophosphamide (N=17) or fludarabine (N= 3) and anti-thymoglobulin (ATG, mostly 20mg/kg). Stem cell source was bone marrow and post-transplant immunosuppression combined cyclosporine and mycophenolate or methotrexate. In the NMA group, conditioning regimen associated 3Gy TBI and alemtuzumab (1mg/kg), followed by PBSC and post-transplant sirolimus. All patients engrafted and no secondary graft failure was observed. One MAC group patient died from GVHD. The 2-year overall and EFS were 95% (CI 95%: 85.9-100) in the MAC group (median follow-up of 39 months (range 8-63)) and 100% (CI 95%: 100-100) in the NMA group (median follow-up of 17 months (range 9-39)). Incidence of grade II-IV acute GVHD was 0% in the NMA group versus 20% in the MAC group (p=0.12). Incidence of chronic GVHD was 0% in the NMA group versus 25% in the MAC group (p=0.06). From the 27 patients with follow-up>12 months, 17/17 discontinued immunosuppressive therapy in the MAC group versus 8/10 in the NMA group. Hematopoietic recovery was faster in the NMA group with less platelet and red blood cell units transfused (Table). Throughout the follow-up, median donor chimerism was higher after MAC transplantation than after NMA transplantation: 98% (range 69-100) and 86 % (range 50-97) respectively at 1 year (p=0.017). Donor chimerism remained above 50% throughout the follow-up in all patients except 1 of the NMA group who displayed stable chimerism between 40 and 50%. All patients achieved HbS level close to the one of their donors. There was no difference between the 2 groups regarding occurrence of infections. MAC transplant was more often associated with hypertension, neurological complications, severe mucositis and need of enteral or parenteral nutrition. Moreover, duration of hospitalization was longer in MAC group: 54 days (range 39-192) versus 35 days in the NMA group (range 21-52) (p Conclusion In this series of adolescents and adults transplanted for SCD, the survival without SCD was excellent with a faster hematological recovery and a lower toxicity after NMA HSCT. Longer follow-up is required to confirm stable mixed donor chimerism and the cure of SCD after NMA approach. Figure 1 Figure 1. Disclosures Joseph: bluebird bio: Consultancy. Boissel: Servier: Consultancy, Honoraria; JAZZ Pharma: Honoraria, Research Funding; Incyte: Honoraria; Amgen: Consultancy, Honoraria, Research Funding; SANOFI: Honoraria; CELGENE: Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; PFIZER: Consultancy, Honoraria. Pondarré: ADDMEDICA: Honoraria.

Introduction Allogeneic hematopoïetic stem cell transplantation (HSCT) is the only established curative therapy for patients (pts) with sickle cell disease (SCD). It is mostly performed in children 1, due to higher risk of graft-versus-host disease (GVHD) and transplant related mortality in adults. Different approaches have been developped to improve tolerance of transplant in adults: use of reduced intensity conditioning (RIC) regimens 2 and intensive immunosuppression to avoid GVHD. Here, we have studied the impact of such approaches on immune reconstitution in adolescents and adults transplanted for SCD. Patients and methods We report 39 transplants in adolescents and adults, performed in Saint Louis hospital from 2008 to 2020: 25 were matched related transplants (MRT) and 14 haplo-identical related transplant (HRT). In MRT, conditioning was myeloablative (MAC) in 15 pts (busulfan, cyclophosphamide, rabbit anti-thymoglobulin (ATG) 20 mg/kg) and non myeloablative (NMA) in 10 pts (alemtuzumab 1 mg/kg, 3 Gy total body irradiation (TBI)). In MAC transplants, stem cell source was bone marrow and post-transplant immunosuppression was methotrexate and cyclosporine. In NMA transplants, stem cell source was peripheral blood cells with post-transplant immunosuppression by sirolimus. In the 14 HRT, the conditioning was reduced (cyclophosphamide, thiotepa, fludarabine, 2 Gy TBI, ATG 4.5 mg/kg), stem cell source was bone marrow and GVHD prophylaxis was ensured by post-transplant cyclophosphamide (100 mg/kg), sirolimus and mycophenolate mofetil. Results Median age at transplant was 17 years (y) old (range (r) 14-39). With a median follow-up of 3.6 y, the 2-y overall survival and survival without SCD were 97% (IC95%: 0.92-1) and 92% (IC95%: 0.83-1) respectively: no event after MRT, 1 death of GVHD and 2 graft rejections after HRT. The acute GVHD grade II-IV rate was 33%: 21% after HRT, 13% after MAC MRT and 0% after NMA MRT. Chronic GVHD occured in 3 pts (8%): severe in 1 HRT and mild in 2 MAC MRT. At 6 months, the blood chimerism evaluated in the 36 patients alive without rejection, was more often mixed (5 to 95% of donor) after NMA MRT (100%) versus MAC MRT (40%, p = 0.003) and HRT (18%, p < 0.001). Total lymphocytes (TL) counts increased rapidly in HRT and MAC MRT with a normalization from 3 months post-transplant. In contrast, NMA MRT experienced a slower recovery: at 6 months, median count was 1039/mm3 (r 463-1767) compared to 2071/mm3 (r 882-5985, p = 0.002) after MAC MRT and 2382/mm3 (r 676-3978, p = 0.005) after HRT. After NMA MRT, TL counts remained lower than normal values up to 12 months with a median of 1195/mm3 (r 870-3210) (Figure 1A). HRT displayed a rapid normalization of CD4 counts with a 3-month median count of 645/mm3 (r 350-1076) higher than reported after MRT (p < 0.001). Evolution of CD4 counts was similar after NMA and MAC MRT. They were lower than normal values during the first 12 months: median 364/mm3 and 388/mm3 respectively at 12 months (p = 0.25) (Figure 1B). From 3 months post-transplant, CD8 counts reached normal values after MAC MRT (314/mm3, r 108-2175) and were superior to normal after HRT (1335/mm3, r 66-4529), with a significant difference between HRT and MRT (p = 0.003). After NMA MRT, there was a trend for lower 3-month CD8 counts compared to MAC MRT: median of 107/mm3 (r 18-631, p = 0.08). CD8 counts remained under normal values after NMA MRT up to 12 months post-transplant (Figure 1C). From 3 to 6 months, CD4 and CD8 were mostly memory, with only 3.2% (r 0.1%-20.6%) and 6.2% (r 2.1%-11.2%) of CD45RA+ CCR7+ naïve CD8+ and CD4+ respectively. In the 3 groups NK cell counts reached normal values after 3 months. B lymphocytes counts normalized in the first months post-transplant except for patients who received rituximab for EBV reactivation. From 3 to 6 months, B lymphocytes were mostly naive: 98% of CD27- (r 92%-99%). Gammaglobuline levels were normal from 3 months in the 3 groups. Twelve (31%) pts were treated for a CMV and 6 (15%) for an EBV reactivation. No patient had CMV or adenovirus disease, or post-transplant lymphoproliferative disorder. Infections according to transplant types are detailed in figure 1D. Conclusion NMA MRT were associated with a delayed CD4 and CD8 recovery probably due to alemtuzumab. As previously reported 3, HRT displayed a rapid immune reconstitution. Despite use of serotherapy in the three modalities of transplant, the rate of viral infections remained acceptable without severe episode. Figure 1 Figure 1. Disclosures Pondarré: ADDMEDICA: Honoraria. Peffault De Latour: Jazz Pharmaceuticals: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Amgen: Consultancy, Other, Research Funding; Alexion, AstraZeneca Rare Disease: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding. Boissel: CELGENE: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; JAZZ Pharma: Honoraria, Research Funding; Incyte: Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Servier: Consultancy, Honoraria; SANOFI: Honoraria; PFIZER: Consultancy, Honoraria.

Context. Functional precision medicine is gaining momentum in AML, notably through ex vivo drug sensitivity screening (DSS) of primary patient (pt) cells (Pemovska Cancer Discov 2013, Tyner Nature 2018). The DSS landscape differs across genetic AML subgroups (Tyner Nature 2016), of which NPM1mut is the most frequent (Papaemmanuil NEJM 2016). DSS in AML has mostly been done in standard conditions, with overall viability as unique endpoint. Niche signals, which can be partly mimicked in vitro, convey drug resistance in vivo. Drugs can induce a variety of cell fates in AML. Induction of differentiation rather than killing of blasts, can result in false negative results in global viability assays. Persistence of leukemic stem cells (LSC) represents a major cause of treatment failure. GPR56 is a ubiquitous surface marker enriching for LSCs and stable upon short-term ex vivo culture (Pabst Blood 2016). Objectives. To develop an ex vivo niche-like multiparametric DSS platform for primary AML cells. To validate its clinical relevance in NPM1mut pts treated with conventional DNR-AraC chemotherapy. To discover new sensitizers to DNR-AraC chemotherapy in NPM1mut AML. Results. We designed an MFC panel to count viable blasts and measure their differentiation (CD11b/CD14/CD15) and stemness (GPR56) after exclusion of residual lymphocytes (Figure 1A). We validated GPR56 expression as stemness marker based on increased retention of GPR56+ cells in niche-like coculture combining hypoxia (O2 3%) and MSC compared to standard conditions (p To further mimic in vivo conditions, we derived a MEMa-based plasma-like medium (PLM) based on targeted metabolomics (Figure 1E) and electro-chemoluminescent cytokine assays of 29 diagnostic AML bone marrow plasma samples compared to conditioned media of primary AML cells cultured in niche-like conditions (MSC, hypoxia). This instructed the design of our custom PLM with dialyzed FBS and defined low-dose (~1 ng/mL range) cytokines (CK) and amino-acid (AA) concentrations. We next investigated the contribution of MSCs, hypoxia, plasma-like AAs and CKs on blasts viability, differentiation, stemness and drug response in 3 NPM1mut AMLs exposed to fixed concentrations of 6 core AML therapies. This analysis uncovered significant interactions between these 4 niche components in dictating blast viability and stemness upon 72h ex vivo culture (Figure 1F) and revealed the distinct contribution of these niche components to drug sensitivity. RNA-seq of primary blasts cultured in niche-like, plasma-like conditions revealed marked enrichment of stemness pathways compared to ex vivo culture in standard conditions. Finally, we explored DNR-AraC (five-point serial dilution) alone or in combination with fixed, clinically relevant concentrations of 24 drugs in 49 primary AML samples (including 34 NPM1mut). Using AUCs of DNR-AraC on lymphocytes as internal control, we first validated our NEXT assay on NPM1 MRD levels in the 34 NPM1mut pts treated frontline with conventional DNR-AraC regimens (Figure 1G). Across all 49 pts, we uncovered 11 different optimal 'third-drugs', stressing the role of our NEXT assay to deploy precision medicine in daily practice. At the population level, we could nominate 3 top combinations, two of which are currently in clinical investigation (Venetoclax and Selinexor). The unpublished sensitizing effect of low dose (0.25µM) Ruxolitinib on DNR-AraC uncovered with our NEXT assay is currently being investigated in PDX models. Conclusion. We designed the NEXT assay, a multiparametric drug screening of AML viability, differentiation and stemness in niche-like culture combining hypoxia, stromal interactions and plasma-like medium. Components of the niche-like culture interact to govern leukemic viability and stemness. Our assay could predict MRD achievement in NPM1mut AML and identifies novel sensitizers to DNR-AraC in these pts. Disclosures Clappier: Amgen: Honoraria, Research Funding. Ades:Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; jazz: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Research Funding; novartis: Research Funding; Celgene/BMS: Research Funding. Itzykson:Amgen: Membership on an entity's Board of Directors or advisory committees; Otsuka Pharma: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Stemline: Membership on an entity's Board of Directors or advisory committees; Oncoethix (now Merck): Research Funding; Janssen: Research Funding; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria; Daiichi Sankyo: Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS (Celgene): Honoraria; Sanofi: Honoraria; Astellas: Honoraria.

Intra-tumor heterogeneity portends poor outcome in many cancers. In AML, a higher number of drivers worsens prognosis. The Shannon Index is a robust metric of clonal heterogeneity that accounts for the number of clones, but also their relative abundance. We show that a Shannon Index can be estimated from bulk sequencing, which is correlated (ρ = 0.76) with clonal diversity from single-colony genotyping. In a discovery cohort of 292 patients with sequencing of 43 genes, a higher number of drivers (HR = 1.18, P = 0.028) and a lower Shannon Index (HR = 0.68, P = 0.048), the latter reflecting clonal dominance, are independently associated with worse OS independently of European LeukemiaNet 2017 risk. These findings are validated in an independent cohort of 1184 patients with 111-gene sequencing (number of drivers HR = 1.16, P = 1 × 10