Anne Marie Ronchetti

Cancer cells require glutamine to adapt to increased biosynthetic activity. The limiting step in intracellular glutamine catabolism involves its conversion to glutamate by glutaminase (GA). Different GA isoforms are encoded by the genes GLS1 and GLS2 in humans. Herein, we show that glutamine levels control mitochondrial oxidative phosphorylation (OXPHOS) in acute myeloid leukemia (AML) cells. Glutaminase C (GAC) is the GA isoform that is most abundantly expressed in AML. Both knockdown of GLS1 expression and pharmacologic GLS1 inhibition by the drug CB-839 can reduce OXPHOS, leading to leukemic cell proliferation arrest and apoptosis without causing cytotoxic activity against normal human CD34(+) progenitors. Strikingly, GLS1 knockdown dramatically inhibited AML development in NSG mice. The antileukemic activity of CB-839 was abrogated by both the expression of a hyperactive GAC(K320A) allele and the addition of the tricarboxyclic acid cycle product α-ketoglutarate, indicating the critical function of GLS1 in AML cell survival. Finally, glutaminolysis inhibition activated mitochondrial apoptosis and synergistically sensitized leukemic cells to priming with the BCL-2 inhibitor ABT-199. These findings show that targeting glutamine addiction via GLS1 inhibition offers a potential novel therapeutic strategy for AML.

Kaposi sarcoma-associated herpesvirus (KSHV)/human herpesvirus 8-associated multicentric Castleman disease (MCD) is a polyclonal B-cell lymphoproliferative disorder that mainly occurs in immunocompromised hosts. The diagnosis relies on lymph node biopsy demonstrating KSHV-infected cells located in the mantle zone with a marked interfollicular plasma cell infiltration. Infected cells are large cells positive for immunoglobulin M (IgM), λ light chain, and CD38, described initially as infected plasmablasts. We show that IgM+λ+CD38high cells were also detectable in the peripheral blood of 14 out of 18 (78%) patients with active KSHV-MCD and absent in 40 controls. Using immunofluorescence and flow-fluorescence in situ hybridization, we demonstrate that these cells are KSHV infected and express both latent and lytic KSHV transcripts. These KSHV-infected viroblasts (KIVs) harbor a distinct phenotype compared with conventional plasmablasts. We also identified several putative mechanisms of immune escape used by KSHV, because KIVs displayed an overall decrease of costimulatory molecules, with a remarkable lack of CD40 expression and are interleukin-10-producing cells. The identification of this specific and easily accessible KSHV+ circulating population brings new elements to the understanding of KSHV-MCD but also raises new questions that need to be clarified.

Rationale. Acute lymphoblastic leukemia (ALL) with unfavorable biology and/or high minimal residual disease (MRD) levels are at high-risk of disease recurrence. Based on the results of the GRAALL-2005/T study (Trinquand A et al, JCO 2013; Beldjord K et al, Blood 2014), T-ALL patients enrolled in the GRAALL-2014/T trial were classified at high-risk (HR) if presenting an unfavorable 4-gene classifier (absence of NOTCH1/FBXW7 mutations or presence of RAS/PTEN alterations) and/or a post-induction IG/TR MRD1 ≥ 10 -4 (including the need of a salvage course to reach a complete remission [CR]). In the phase 2 ATRIALL sub-study, HR patients were offered to receive nelarabine (NELA) during consolidation and maintenance or as bridge to allogeneic hematopoietic stem cell transplantation (HSCT). The aim of the present report is to compare their outcome to that of similar patients treated in the same GRAALL-2014/T trial but without frontline NELA. Method. Between November 2015 and May 2022, the GRAALL-2014/T included 325 patients with T-ALL. Among these patients, 199 presented with HR features. The ATRIALL sub-study was activated in April 2017. ATRIALL eligibility criteria were defined as HR features, no CNS involvement at baseline, and continuous CR before to start consolidation 2 (first NELA course) at week 12. Based on the results of the COG phase 3 study, the protocol was amended in January 2021 to include patients with CNS involvement at baseline. NELA was given at 1,500 mg/sqm/day at day 1,3 and 5 in combination with etoposide and cyclophosphamide for a maximum of 5 courses during consolidation (2 cycles) and maintenance (3 cycles). Patients with MRD1 ≥ 10 -3 and/or with post-consolidation 1 MRD2 ≥ 10 -4 were eligible for HSCT after one NELA course. A total of 121 patients were included. One patient was excluded due to overt relapse before to start NELA. Eight patients had CNS involvement at baseline. A total of 33 patients included in the GRAALL-2014/T met initial ATRIALL criteria but were not included in the sub-study either before ATRIALL activation (N=21), or during accrual (N=10), or after accrual completion (N=2) and received standard of care (SOC) without NELA. The ATRIALL/CNS- cohort (N=112) was compared to the control cohort (N=33) for MRD response, cumulative incidence of relapse (CIR), disease-free survival (DFS) and overall survival (OS). Results. The median follow-up in the ATRIALL study (n=120) was 2.9 years (95%CI, 2.5-3.5). At 3 years, the CIR, DFS, and OS were 28% (95%CI, 20-37), 67% (95%CI, 55-76), and 71% (95%CI, 61-79), respectively. Patients from the ATRIALL/CNS- (N=112) and control (N=33) cohorts exhibited similar characteristics, except for a longer median follow-up in the control cohort (Figure A). Patients included in the ATRIALL study reached lower post-consolidation MRD3 levels (p=0.05). Among patients with MRD1 ≥10 -4, undetectable MRD3 was achieved in 36/55 (65%) after NELA versus 5/16 (31%) after SOC (p=0.02). When censoring at HSCT time, NELA was associated with a significantly reduced CIR (SHR=0.48; 95%CI, 0.23-0.99; p=0.045) and a trend for a prolonged DFS (HR=0.52; 95%CI, 0.26-1.07; p=0.075) (Figure B,C). This difference did not reach significance when patients were not censored at HSCT time. Indeed, high-risk patients not eligible for HSCT benefited from NELA in terms of CIR (SHR=0.43; 95%CI, 0.20-0.98; p=0.045) and DFS (HR=0.46; 95%CI, 0.21-1.03; p=0.06). Patients with non-ETP ALL had a significantly improved CIR (SHR=0.03; 95%CI, 0.17-0.89; p=0.025) and DFS (HR=0.47; 95%CI, 0.22-0.99; p=0.048), whereas ETP-ALL patients did not benefit from NELA over SOC. There was no benefit of prior NELA in patients who received alloHSCT per protocol. Conclusion. While NELA did not yield an overall improved outcome in the study population, benefits were observed in favorable MRD responders and non-ETP patients. Additional prospective studies are needed to further delineate the specific patient subgroups that might benefit from NELA.

Introduction T-cell acute lymphoblastic leukemia (T-ALL) is an orphan disease diagnosed mostly in adolescent and young adults. In adult population, 5-10% of T-ALL patients (pts) will be primary refractory and 30-40% will relapse. In relapse/refractory (R/R) patients, standard of care treatments, including nelarabine, yield response rate of about 20-40% and responses are of short duration. On behalf of the GRAALL (Group for Research on Adult Acute Lymphoblastic Leukemia), we launched the ALL-TARGET project combining a precision medicine platform dedicated to R/R T-ALL and T-cell lymphoblastic lymphoma (T-LL), and an observatory to evaluate therapeutic proposals based on mutational profile and intracellular signaling pathways alterations. Objectives and methods Leukemic samples from pts with R/R T-ALL/LL were shipped to the GRAALL T-ALL central laboratory in France (V. Asnafi, Hôpital Necker). Biological characterization comprised oncogenetic, phenotypic and in some cases functional analysis. Clinical data from R/R T-ALL/LL pts were collected in a real-life observatory (NCT05832125). Adults pts were eligible if an oncogenetic characterization was available at diagnosis or relapse, and if they received a salvage, either with conventional therapy or with a targeted therapeutic option (TTO). For example, TTOs included Tofacitinib and Venetoclax (Tofa/Ven) in case of IL7R (CD127) expression or IL7R-pathway alterations (IL7R ALT), 5-azacytidine and Venetoclax (Aza/Ven) in case of T-ALL/LL with epigenetic regulators alterations (DNMT3A, ASXL1, PHF6, TET2, PRC2, IDH1/2, SRSF2...) or Temsirolimus, Erwinase and Venetoclax (Tem/Erw/Ven) in case of PI3K signaling pathway alterations (PI3K ALT). The ALL-TARGET Observatory primary endpoint was overall response rate (ORR) including complete remission (CR), CR with incomplete hematological recovery and partial response. We report here the results of the first pts included, with a focus on those who received TTOs as salvage therapy. Results Eighty-nine were analyzed, including 80 T-ALL and 9 T-LL. Sex ratio was 3 and median age at diagnosis was 37.5y, and 51y at the time of the first TTO. Seventy-one pts were in relapse (79.7%) and 18 primary refractory (20.2%). Relapses occurred after a median first CR duration of 16.6 months (range: 2.5-92), with 62.8% in bone marrow, 30% in CNS and 30.3% in other extramedullary sites. Phenotype at diagnosis was available for 68 pts, including 36 Early T-cell Precursor (ETP or near-ETP) (52.9%), 6 immature non-ETP (8.8%), 20 cortical (29.4%) and 6 mature phenotype (8.8%). IL7R-expression was available for 53 pts, of whom 40 were IL7R+ (75.5%) and 13 IL7R- (24.5%). Out of 50 samples with available BCL2-expression, 47 were BCL2+ (94%) and 3 BCL2- (6%). IL7R ALT were evidenced in 41 pts (48.2%), PI3K ALT in 21 pts (24.7%), RAS pathway alterations (RAS ALT) in 19 pts (22.4%) and epigenetic dysregulation in 42 pts (49.4%). Ten pts harbored TP53/ATM mutations (11.7%) . These different alterations could coexist. At relapse, 33 phenotypes were reported, showing 22 ETP (66.6%), 2 immature non-ETP (6%) and 9 cortical (27.3%). IL7R-expression was available for 26 pts, among which 21 were IL7R+ (63.6%) and 5 IL7R- (19.2%). NGS was performed in 24 patients, revealing IL7R ALT in 9 pts (37.5%), PI3K ALT in 6 pts (25%), RAS ALT in 5 pts (20.8%) and epigenetic dysregulation in 15 pts (62.5%). Nine patients had TP53 mutations (37.5%). Twenty-five patients received a TTO, including 14 Aza/Ven (56%), 8 Tofa/Ven (32%), 2 Tem/Erw/Ven (8%) and 1 Trametinib/Ven (4%). Among these, 8 were in first salvage (32%), 10 in 2 nd (40%), and 6 in 3 rd/4 th salvage (28%). Of note, 14 patients received Ven associated with chemotherapy, including 4 Nelarabine-Ven, and 3 Ven in monotherapy. By 3 months, the cumulative incidence of response under the chosen TTO was 70.7% (95%CI:51-88) (Figure). Ten of 14 patients were in response after Aza/Ven (ORR 71.4%), 4 of 8 patients after Tofa/Ven (50%) and 2 of 2 patients treated with Tem/Erw/Ven (100%). Five patients were bridged to allogeneic stem cell transplantation. Conclusion Our results demonstrate the feasibility of the ALL-TARGET project. A better knowledge of the oncogenetic landscape of T-ALL, and a close collaboration between clinicians and biologists, resulted in individualized treatment strategies. With a 3 months cumulative incidence of response of 70%, TTOs appear to be a promising approach in R/R T-ALL.

We report here the first clinical case of GvL post Blinatumomab treatment in acute lymphoblastic leukemia relapsing after allo stem cell transplantation. This effects accompanied a skin GvHD and has been documented by skin biopsy, immune-staining and FISH. We thus hypothesize that the GvHD may have contributed to disease eradication in this patient, the allogeneic setting reinforcing the immunological efficacy of blinatumomab through a GvL effect. Blinatumomab could actually represent a very interesting therapeutic approach in relapse and/or in prevention of relapse after alloSCT.