Immune effector cell-associated hematotoxicity: EHA/EBMT consensus grading and best practice recommendations.

Hematological toxicity is the most common adverse event after chimeric antigen receptor (CAR) T-cell therapy. Cytopenias can be profound and long-lasting and can predispose for severe infectious complications. In a recent worldwide survey, we demonstrated that there remains considerable heterogeneity in regard to current practice patterns. Here, we sought to build consensus on the grading and management of immune effector cell-associated hematotoxicity (ICAHT) after CAR T-cell therapy. For this purpose, a joint effort between the European Society for Blood and Marrow Transplantation (EBMT) and the European Hematology Association (EHA) involved an international panel of 36 CAR T-cell experts who met in a series of virtual conferences, culminating in a 2-day meeting in Lille, France. On the basis of these deliberations, best practice recommendations were developed. For the grading of ICAHT, a classification system based on depth and duration of neutropenia was developed for early (day 0-30) and late (after day +30) cytopenia. Detailed recommendations on risk factors, available preinfusion scoring systems (eg, CAR-HEMATOTOX score), and diagnostic workup are provided. A further section focuses on identifying hemophagocytosis in the context of severe hematotoxicity. Finally, we review current evidence and provide consensus recommendations for the management of ICAHT, including growth factor support, anti-infectious prophylaxis, transfusions, autologous hematopoietic stem cell boost, and allogeneic hematopoietic cell transplantation. In conclusion, we propose ICAHT as a novel toxicity category after immune effector cell therapy, provide a framework for its grading, review literature on risk factors, and outline expert recommendations for the diagnostic workup and short- and long-term management.

Flotetuzumab as salvage immunotherapy for refractory acute myeloid leukemia.

Approximately 50% of acute myeloid leukemia (AML) patients do not respond to induction therapy (primary induction failure [PIF]) or relapse after <6 months (early relapse [ER]). We have recently shown an association between an immune-infiltrated tumor microenvironment (TME) and resistance to cytarabine-based chemotherapy but responsiveness to flotetuzumab, a bispecific DART antibody-based molecule to CD3ε and CD123. This paper reports the results of a multicenter, open-label, phase 1/2 study of flotetuzumab in 88 adults with relapsed/refractory AML: 42 in a dose-finding segment and 46 at the recommended phase 2 dose (RP2D) of 500 ng/kg per day. The most frequent adverse events were infusion-related reactions (IRRs)/cytokine release syndrome (CRS), largely grade 1-2. Stepwise dosing during week 1, pretreatment dexamethasone, prompt use of tocilizumab, and temporary dose reductions/interruptions successfully prevented severe IRR/CRS. Clinical benefit accrued to PIF/ER patients showing an immune-infiltrated TME. Among 30 PIF/ER patients treated at the RP2D, the complete remission (CR)/CR with partial hematological recovery (CRh) rate was 26.7%, with an overall response rate (CR/CRh/CR with incomplete hematological recovery) of 30.0%. In PIF/ER patients who achieved CR/CRh, median overall survival was 10.2 months (range, 1.87-27.27), with 6- and 12-month survival rates of 75% (95% confidence interval [CI], 0.450-1.05) and 50% (95% CI, 0.154-0.846). Bone marrow transcriptomic analysis showed that a parsimonious 10-gene signature predicted CRs to flotetuzumab (area under the receiver operating characteristic curve = 0.904 vs 0.672 for the European LeukemiaNet classifier). Flotetuzumab represents an innovative experimental approach associated with acceptable safety and encouraging evidence of activity in PIF/ER patients. This trial was registered at www.clinicaltrials.gov as #NCT02152956.

Clinical Impact of Pretransplant Multidrug-Resistant Gram-Negative Colonization in Autologous and Allogeneic Hematopoietic Stem Cell Transplantation.

Multidrug-resistant Gram-negative bacteria (MDR-GNB) are an emerging cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). Three-hundred forty-eight consecutive patients transplanted at our hospital from July 2012 to January 2016 were screened for a pretransplant MDR-GNB colonization and evaluated for clinical outcomes. A pretransplant MDR-GNB colonization was found in 16.9% of allo-HSCT and in 9.6% of auto-HSCT recipients. Both in auto- and in allo-HSCT, carriers of a MDR-GNB showed no significant differences in overall survival (OS), transplant-related mortality (TRM), or infection-related mortality (IRM) compared with noncarriers. OS at 2 years for carriers compared with noncarriers was 85% versus 81% (P = .262) in auto-HSCT and 50% versus 43% (P = .091) in allo-HSCT. TRM at 2 years was 14% versus 5% (P = .405) in auto-HSCT and 31% versus 25% (P = .301) in allo-HSCT. IRM at 2 years was 14% versus 2% (P = .142) in auto-HSCT and 23% versus 14% (P = .304) in allo-HSCT. In multivariate analysis, only grade III to IV acute graft-versus-host disease was an independent factor for reduced OS (P < .001) and increased TRM (P < .001) and IRM (P < .001). During the first year after transplant, we collected 73 GNB bloodstream infectious (BSI) episodes in 54 patients, 42.4% of which sustained by a MDR-GNB. Rectal swabs positivity associated with the pathogen causing subsequent MDR-GNB BSI episodes in 13 of 31 (41.9%). Overall, OS at 4 months from MDR-GNB BSI episode onset was of 67.9%, with a 14-day attributed mortality of 12.9%, not being significantly different between carriers and noncarriers (P = .207). We conclude that in this extended single-center experience, a pretransplant MDR-GNB colonization did not significantly influence OS, TRM, and IRM both in auto- and allo-HSCT settings and that MDR-GNB attributed mortality can be controlled in carriers when an early pre-emptive antimicrobial therapy is started in case of neutropenic fever.

A New Clinicobiological Scoring System for the Prediction of Infection-Related Mortality and Survival after Allogeneic Hematopoietic Stem Cell Transplantation.

Infection-related mortality (IRM) is a substantial component of nonrelapse mortality (NRM) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). No scores have been developed to predict IRM before transplantation. Pretransplantation clinical and biochemical data were collected from a study cohort of 607 adult patients undergoing allo-HSCT between January 2009 and February 2017. In a training set of 273 patients, multivariate analysis revealed that age >60 years (P = .003), cytomegalovirus host/donor serostatus different from negative/negative (P < .001), pretransplantation IgA level <1.11 g/L (P = .004), and pretransplantation IgM level <.305 g/L (P = .028) were independent predictors of increased IRM. Based on these results, we developed and subsequently validated a 3-tiered weighted prognostic index for IRM in a retrospective set of patients (n = 219) and a prospective set of patients (n = 115). Patients were assigned to 3 different IRM risk classes based on this index score. The score significantly predicted IRM in the training set, retrospective validation set, and prospective validation set (P < .001, .044, and .011, respectively). In the training set, 100-day IRM was 5% for the low-risk group, 11% for the intermediate-riak group, and 16% for the high-risk groups. In the retrospective validation set, the respective 100-day IRM values were 7%, 17%, and 28%, and in the prospective set, they were 0%, 5%, and 7%. This score predicted also overall survival (P < .001 in the training set, P < 041 in the retrospective validation set, and P < .023 in the prospective validation set). Because pretransplantation levels of IgA/IgM can be modulated by the supplementation of enriched immunoglobulins, these results suggest the possibility of prophylactic interventional studies to improve transplantation outcomes.

Recurrent ETNK1 mutations in atypical chronic myeloid leukemia.

Despite the recent identification of recurrent SETBP1 mutations in atypical chronic myeloid leukemia (aCML), a complete description of the somatic lesions responsible for the onset of this disorder is still lacking. To find additional somatic abnormalities in aCML, we performed whole-exome sequencing on 15 aCML cases. In 2 cases (13.3%), we identified somatic missense mutations in the ETNK1 gene. Targeted resequencing on 515 hematological clonal disorders revealed the presence of ETNK1 variants in 6 (8.8%) of 68 aCML and 2 (2.6%) of 77 chronic myelomonocytic leukemia samples. These mutations clustered in a small region of the kinase domain, encoding for H243Y and N244S (1/8 H243Y; 7/8 N244S). They were all heterozygous and present in the dominant clone. The intracellular phosphoethanolamine/phosphocholine ratio was, on average, 5.2-fold lower in ETNK1-mutated samples (P < .05). Similar results were obtained using myeloid TF1 cells transduced with ETNK1 wild type, ETNK1-N244S, and ETNK1-H243Y, where the intracellular phosphoethanolamine/phosphocholine ratio was significantly lower in ETNK1-N244S (0.76 ± 0.07) and ETNK1-H243Y (0.37 ± 0.02) than in ETNK1-WT (1.37 ± 0.32; P = .01 and P = .0008, respectively), suggesting that ETNK1 mutations may inhibit the catalytic activity of the enzyme. In summary, our study shows for the first time the evidence of recurrent somatic ETNK1 mutations in the context of myeloproliferative/myelodysplastic disorders.

Human Herpesvirus 6 Infection Following Haploidentical Transplantation: Immune Recovery and Outcome.

Human herpesvirus 6 (HHV-6) is increasingly recognized as a potentially life-threatening pathogen in allogeneic hematopoietic stem cell transplantation (alloSCT). We retrospectively evaluated 54 adult patients who developed positivity to HHV-6 after alloSCT. The median time from alloSCT to HHV-6 reactivation was 34 days. HHV-6 was present in plasma samples from 31 patients, in bone marrow (BM) of 9 patients, in bronchoalveolar lavage fluid and liver or gut biopsy specimens from 33 patients, and in cerebrospinal fluid of 7 patients. Twenty-nine patients developed acute graft-versus-host disease (GVHD), mainly grade III-IV, and 15 had concomitant cytomegalovirus reactivation. The median absolute CD3+ lymphocyte count was 207 cells/µL. We reported the following clinical manifestations: fever in 43 patients, skin rash in 22, hepatitis in 19, diarrhea in 24, encephalitis in 10, BM suppression in 18, and delayed engraftment in 11. Antiviral pharmacologic treatment was administered to 37 patients; nonetheless, the mortality rate was relatively high in this population (overall survival [OS] at 1 year, 38% ± 7%). A better OS was significantly associated with a CD3+ cell count ≥200/µL at the time of HHV-6 reactivation (P = .0002). OS was also positively affected by the absence of acute GVHD grade III-IV (P = .03) and by complete disease remission (P = .03), but was not significantly influenced by steroid administration, time after alloSCT, type of antiviral prophylaxis, plasma viral load, or organ involvement. Although HHV-6 detection typically occurred early after alloSCT, better T cell immune reconstitution seems to have the potential to improve clinical outcomes. Our findings provide new insight into the interplay between HHV-6 and the transplanted immune system.

Treosulfan based reduced toxicity conditioning followed by allogeneic stem cell transplantation in patients with myelofibrosis.

Allogeneic transplantation is the only potentially curative strategy for myelofibrosis, even in the era of new drugs that so far only mitigate symptoms. The choice to proceed to allogeneic transplantation is based on several variables including age, disease phase, degree of splenomegaly, donor availability, comorbidities and iron overload. These factors, along with conditioning regimen and time to transplantation, may influence the outcome of ASCT. We report 14 patients affected by myelofibrosis with a median age of 57 years (range, 41-76) receiving a treosulfan-fludarabine based reduced toxicity conditioning. Patients (pts) received a stem cell transplantation from an HLA identical (n = 10) or matched unrelated donor (n = 4). All pts had a complete myeloablation followed by engraftment and in 12 out of 13 evaluated pts donor chimerism was 100% at 1 month. In most cases a reduction of splenomegaly and a reduction (or resolution) of bone marrow fibrosis was observed. After a median follow-up of 39 months (range, 3-106), the 3-year probability of overall survival and disease free survival was 54 +/- 14% and 46 +/- 14%, respectively. The cumulative incidence of non-relapse mortality at 2 years was 39 +/- 15%. Causes of non-relapse mortality were: infection (n = 2), GvHD (n = 2) and haemorrhage (n = 1). We can conclude that a treosulfan and fludarabine based conditioning has a potent myeloablative and anti-disease activity although non-relapse mortality remains high in this challenging clinical setting. Copyright © 2014 John Wiley & Sons, Ltd.

High rate of hematological responses to sorafenib in FLT3-ITD acute myeloid leukemia relapsed after allogeneic hematopoietic stem cell transplantation.

Relapse represents the most significant cause of failure of allogeneic hematopoietic stem cell transplantation (HSCT) for FLT3-ITD-positive acute myeloid leukemia (AML), and available therapies are largely unsatisfactory. In this study, we retrospectively collected data on the off-label use of the tyrosine kinase inhibitor sorafenib, either alone or in association with hypomethylating agents and adoptive immunotherapy, in 13 patients with post-transplantation FLT3-ITD-positive AML relapses. Hematological response was documented in 12 of 13 patients (92%), and five of 13 (38%) achieved complete bone marrow remission. Treatment was overall manageable in the outpatient setting, although all patients experienced significant adverse events, especially severe cytopenias (requiring a donor stem cell boost in five patients) and typical hand-foot syndrome. None of the patients developed graft-vs.-host disease following sorafenib alone, whereas this was frequently observed when this was given in association with donor T-cell infusions. Six patients are alive and in remission at the last follow-up, and four could be bridged to a second allogeneic HSCT, configuring a 65 ± 14% overall survival at 100 d from relapse. Taken together, our data suggest that sorafenib might represent a valid treatment option for patients with FLT3-ITD-positive post-transplantation relapses, manageable also in combination with other therapeutic strategies.

Post-transplantation Cyclophosphamide and Sirolimus after Haploidentical Hematopoietic Stem Cell Transplantation Using a Treosulfan-based Myeloablative Conditioning and Peripheral Blood Stem Cells.

Haploidentical hematopoietic stem cell transplantation (HSCT) performed using bone marrow (BM) grafts and post-transplantation cyclophosphamide (PTCy) has gained much interest for the excellent toxicity profile after both reduced-intensity and myeloablative conditioning. We investigated, in a cohort of 40 high-risk hematological patients, the feasibility of peripheral blood stem cells grafts after a treosulfan-melphalan myeloablative conditioning, followed by a PTCy and sirolimus-based graft-versus-host disease (GVHD) prophylaxis (Sir-PTCy). Donor engraftment occurred in all patients, with full donor chimerism achieved by day 30. Post-HSCT recovery of lymphocyte subsets was broad and fast, with a median time to CD4 > 200/µL of 41 days. Cumulative incidences of grade II to IV and III-IV acute GVHD were 15% and 7.5%, respectively, and were associated with a significant early increase in circulating regulatory T cells at day 15 after HSCT, with values < 5% being predictive of subsequent GVHD occurrence. The 1-year cumulative incidence of chronic GVHD was 20%. Nonrelapse mortality (NRM) at 100 days and 1 year were 12% and 17%, respectively. With a median follow-up for living patients of 15 months, the estimated 1-year overall and disease-free survival (DFS) was 56% and 48%, respectively. Outcomes were more favorable in patients who underwent transplantation in complete remission (1-year DFS 71%) versus patients who underwent transplantation with active disease (DFS, 34%; P = .01). Overall, myeloablative haploidentical HSCT with peripheral blood stem cells (PBSC) and Sir-PTCy is a feasible treatment option: the low rates of GVHD and NRM as well as the favorable immune reconstitution profile pave the way for a prospective comparative trial comparing BM and PBSC in this specific transplantation setting.

Wilms' tumor gene 1 transcript levels in leukapheresis of peripheral blood hematopoietic cells predict relapse risk in patients autografted for acute myeloid leukemia.

Autologous hematopoietic stem cell transplantation (ASCT) is a curative option alternative to allogeneic transplantation for patients with acute myeloid leukemia (AML). Relapse after ASCT can be due to contamination with leukemic blasts of autologous peripheral blood stem cells (PBSCs) collected by leukapheresis (LK). Identification and quantification of a minimal residual disease (MRD) marker in PBSCs could be relevant in determining the relapse risk after ASCT. High levels of the WT1 gene transcript in bone marrow of AML patients after treatment completion predict disease relapse. We evaluated WT1 transcript levels in autologous PBSC from LK used for ASCT in 30 consecutive AML patients in complete remission (CR) and established a correlation with clinical outcome. At diagnosis, all patients had WT1 overexpression. All patients were in morphological and genetic CR at the time of PBSC collection and before ASCT. Real-time quantitative PCR of WT1 was performed in samples of each LK, using TaqMan technology on RNA from mononucleated cells. The median WT1 transcript level in the PBSC graft (WT1-LK) of patients who relapsed was significantly higher than of those who did not relapse after transplantation (P <.0001). We defined a cut-off level of 80 WT1-LK copies/ABL 10e4 copies to discriminate between positive and negative PBSC grafts. The cut-off level was strongly associated with disease recurrence, DFS and OS. Our study represents the largest series of patients evaluating WT1 as a marker of MRD in PBSC LK products using a completely standardized real-time WT1-reverse transcriptase-PCR based assay. These data, if confirmed by prospective study, will help to determine an individual patient's adapted postremission allocation strategy.

Spontaneous remission of choroidal involvement by chronic myelomonocytic leukemia: a case report.

Chronic myelomonocytic leukemia (CMML) is a rare hematological disorder characterized by variable risk of evolution to acute myeloid leukemia; to date, allogeneic stem cell transplantation is the only curative treatment. We report a case of choroidal involvement in a woman affected by CMML and presenting only with visual impairment. The patient was initially evaluated for an intensive therapeutic approach, but after biopsy the ocular lesion spontaneously regressed. Thus a "watch and wait" strategy was preferred. One year and a half after initial diagnosis, the patient is alive, with stable hematological disease and without any ocular involvement. Therefore, a close, not invasive follow up could be useful to tailor treatment for patients affected by single ocular lesions in CMML.

A multi-center real-life prospective study of axicabtagene ciloleucel versus tisagenlecleucel toxicity and outcomes in Large B-Cell Lymphomas.

This real-world prospective observational study across 21 Italian centers (CART-SIE) compares axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisa-cel) outcomes in 485 relapsed-refractory large B-cell lymphoma patients with baseline characteristics matched by Stabilized Inverse Propensity-Score Weighting. Axi-cel versus tisa-cel had higher all-grade cytokine release syndrome (78.6% vs 89.3%, p=0.0017) and neurotoxicity (9.9% vs 32.2%, p<0.0001), but also superior progression-free survival (PFS) at one year (46.5% vs 34.1%, p=0.0009). Even among patients who failed bridging therapy, axi-cel PFS was superior to tisa-cel (37.5% vs 22.7%, p=0.0059). Differences in overall survival (OS) and high-grade immune toxicities were not significant. The CAR-HEMATOTOX score not only predicted hematologic toxicity but also 1-year survival outcomes (51.5% in CAR-HEMATOTOX high vs. 77.2% in CAR-HEMATOTOX low, p<0.0001). Twenty patients developed second primary malignancies, including two cases of T-cell neoplasms. These findings enable more informed selection of anti-CD19 CAR T-cell therapy balancing bridging, safety and efficacy considerations for individual patients.

Longitudinal single-cell profiling of chemotherapy response in acute myeloid leukemia.

Acute myeloid leukemia may be characterized by a fraction of leukemia stem cells (LSCs) that sustain disease propagation eventually leading to relapse. Yet, the contribution of LSCs to early therapy resistance and AML regeneration remains controversial. We prospectively identify LSCs in AML patients and xenografts by single-cell RNA sequencing coupled with functional validation by a microRNA-126 reporter enriching for LSCs. Through nucleophosmin 1 (NPM1) mutation calling or chromosomal monosomy detection in single-cell transcriptomes, we discriminate LSCs from regenerating hematopoiesis, and assess their longitudinal response to chemotherapy. Chemotherapy induced a generalized inflammatory and senescence-associated response. Moreover, we observe heterogeneity within progenitor AML cells, some of which proliferate and differentiate with expression of oxidative-phosphorylation (OxPhos) signatures, while others are OxPhos (low) miR-126 (high) and display enforced stemness and quiescence features. miR-126 (high) LSCs are enriched at diagnosis in chemotherapy-refractory AML and at relapse, and their transcriptional signature robustly stratifies patients for survival in large AML cohorts.

Levofloxacin prophylaxis vs no prophylaxis in patients with neutropenia within an endemic country for carbapenem-resistant GNB.

Fluoroquinolone prophylaxis's (FQ-P) usefulness in patients with neutropenia is controversial. In recent decades, Italian epidemiological data has shown worrisome rates of FQ resistance. A single-center cohort study on 136 autologous stem cell transplantations (ASCTs) and 223 allogeneic hematopoietic stem cell transplantations (allo-HSCTs) was performed from January 2018 to December 2020. Piperacillin/tazobactam was the first-line therapy for febrile neutropenia (FN). Since February 2019, FQ-P has been omitted. We evaluated the day +30 posttransplant cumulative incidence function (CIF) of gram-negative bacteria pre-engraftment bloodstream infections (PE-BSIs) and any changes in antimicrobial resistance, FN, and infection-related mortality (IRM). In ASCTs, ≥1 FN episode occurred in 74.3% of transplants, without differences among groups (P = .66). CIF of gram-negative bacteria PE-BSI was 10.1%, with a significant difference according to FQ-P (0% [LEVO-group] vs 14.1% [NO-LEVO-group], P = .016). CIF of IRM was 0% in both groups. In allo-HSCTs, ≥1 FN episode occurred in 96.4% of transplants, without differences among groups (P = .72). CIF of gram-negative bacteria PE-BSI was 28%, significantly higher without FQ-P (14.7% [LEVO-group] vs 34.4% [NO-LEVO-group], P = .003). CIF of IRM was 5%, superimposable in both groups (P = .62). Comparing antimicrobial resistance among gram-negative bacteria of allo-HSCT setting, in the group without FQ-P, a significantly higher proportion of pathogens was susceptible to piperacillin/tazobactam (71% vs 30%, P = .026), FQ (49% vs 10%, P = .03), and carbapenems (95% vs 50%, P = .001). FQ-P discontinuation increased gram-negative bacteria PE-BSI but did not impact IRM, both in the ASCT and allo-HSCT settings; importantly, it concurred to significantly decrease antimicrobial resistance in gram-negative bacteria.

MRD in Venetoclax-Based Treatment for AML: Does it Really Matter?

The prognosis of newly diagnosed patients with acute myeloid leukemia is still unfavorable in the majority of cases within the intermediate and mainly adverse genetic risk group but also in a considerable fraction of favorable-risk patients, mainly due to recurrence of disease after complete remission achievement or, less frequently, primary refractoriness. Besides genetic classification at diagnosis, post-treatment prognostic factors include measurable residual disease evaluation in patients in complete remission and in most cases measurable residual disease (MRD) positivity predicts hematologic relapse potentially allowing early therapeutic intervention. Currently, the most commonly used methods for detection of minimal residual disease are multiparameter flow cytometry and quantitative PCR, applicable to around 90% and 50% of patients, respectively. In addition, in > 90% of acute myeloid leukemia (AML) patients, molecular aberrations can be identified by next-generation sequencing, a technology that is widely used in clinical practice for the initial mutational screening at the time of diagnosis but more often, for MRD detection because its flexibility allows almost every mutated gene to be used as an MRD marker. Threshold levels of residual disease and correlation with outcome have been thoroughly studied and established in younger patients treated with intensive induction and consolidation chemotherapy as well as after allogeneic transplantation. Yet, experience on MRD monitoring and interpretation in patients treated with low-intensity regimens, including new agents, is still limited. The updated armamentarium of anti-leukemic agents includes the BCL-2 inhibitor venetoclax, which demonstrated good tolerability, high response rates, and prolonged overall survival when combined with hypomethylating agents or low dose cytarabine in patients considered elderly/"unfit" to tolerate intensive regimens. Although remissions with negative minimal residual disease clearly translated into improved outcomes after intensive treatments, data supporting the same evidence in patients receiving low-intensity venetoclax-based treatments are not still consolidated. We here review and discuss more recent data on the minimal residual disease interpretation and role in AML patients treated with venetoclax-based combinations.

Use of a maturity model for facilitating the introduction of CAR T-cell therapy-Results of the START CAR-T project.

Introduction: Chimeric antigen receptor (CAR) T-cell therapies are novel immunotherapies for the treatment of hematologic malignancies. They are administered in specialized centers by a multidisciplinary team and require the careful coordination of all steps involved in manufacturing and using cellular therapies. The Maturity Model (MM) is a tool developed and used for assessing the effectiveness of a variety of activities. In healthcare, it may assist clinicians in the gradual improvement of patient management with CAR T-cell therapy and other complex treatments. Methods: The START CAR-T project was initiated to investigate the potential of a MM in the setting of CAR T-cell therapy. Four Italian clinics participated in the creation of a dedicated MM. Following the development and test of this MM, its validity and generalizability were further tested with a questionnaire submitted to 18 Italian centers. Results: The START CAR-T MM assessed the maturity level of clinical sites, with a focus on organization, process, and digital support. For each area, the model defined four maturity steps, and indicated the actions required to evolve from a basic to an advanced status. The application of the MM to 18 clinical sites provided a description of the maturity level of Italian centers with regard to the introduction of CAR T-cell therapy. Conclusion: The START CAR-T MM appears to be a useful and widely applicable tool. It may help centers optimize many aspects of CAR T-cell therapy and improve patient access to this novel treatment option.

Integrated Multiomic Profiling Identifies the Epigenetic Regulator PRC2 as a Therapeutic Target to Counteract Leukemia Immune Escape and Relapse.

Immune escape represents a major driver of acute myeloid leukemia (AML) reemergence after allogeneic hematopoietic cell transplantation (allo-HCT), with up to 40% of relapses prompted by nongenomic loss of HLA class II expression in leukemia cells. By integrative analysis of gene expression, DNA methylation, and chromatin accessibility in paired diagnosis/relapse primary samples and in the respective patient-derived xenografts (PDX), we identify the polycomb repressive complex 2 (PRC2) as a key epigenetic driver of this immune escape modality. We report that loss of expression of HLA class II molecules is accompanied by a PRC2-dependent reduction in chromatin accessibility. Pharmacologic inhibition of PRC2 subunits rescues HLA class II expression in AML relapses in vitro and in vivo, with consequent recovery of leukemia recognition by CD4+ T cells. Our results uncover a novel link between epigenetics and leukemia immune escape, which may rapidly translate into innovative strategies to cure or prevent AML posttransplantation relapse. SIGNIFICANCE: Loss of HLA class II expression represents a frequent mechanism of leukemia posttransplantation relapse. Here we identify PRC2 as the main epigenetic driver of this immune escape modality and show that its chemical inhibition can reinstate a proficient graft-versus-leukemia effect, providing an innovative rationale for personalized epigenetic immunotherapies. See related commentary by Köhler and Zeiser, p. 1410. This article is highlighted in the In This Issue feature, p. 1397.

CAR T cell manufacturing from naive/stem memory T lymphocytes enhances antitumor responses while curtailing cytokine release syndrome.

Chimeric antigen receptor (CAR) T cell expansion and persistence represent key factors to achieve complete responses and prevent relapses. These features are typical of early memory T cells, which can be highly enriched through optimized manufacturing protocols. Here, we investigated the efficacy and safety profiles of CAR T cell products generated from preselected naive/stem memory T cells (TN/SCM), as compared with unselected T cells (TBULK). Notwithstanding their reduced effector signature in vitro, limiting CAR TN/SCM doses showed superior antitumor activity and the unique ability to counteract leukemia rechallenge in hematopoietic stem/precursor cell-humanized mice, featuring increased expansion rates and persistence together with an ameliorated exhaustion and memory phenotype. Most relevantly, CAR TN/SCM proved to be intrinsically less prone to inducing severe cytokine release syndrome, independently of the costimulatory endodomain employed. This safer profile was associated with milder T cell activation, which translated into reduced monocyte activation and cytokine release. These data suggest that CAR TN/SCM are endowed with a wider therapeutic index compared with CAR TBULK.