Lymphodepleting preconditioning (LD) is essential for the efficacy of chimeric antigen receptor (CAR) T-cell therapy in hematologic malignancies. However, in the setting of autoimmune diseases (ADs), the contribution of LD for efficacy is unclear. Here, we report on the early safety, efficacy, and correlative data of the first 4 patients with pemphigus vulgaris (PV) who received resecabtagene autoleucel (rese-cel), a fully human CD19 CAR T-cell therapy, without LD in the RESET-PV trial, a substudy of the DesCAARTes trial. Following infusion, pemphigus disease area index scores improved significantly in all patients. A favorable safety profile was observed, with a single episode of grade 1 cytokine release syndrome. Immune effector cell-associated neurotoxicity was not observed. Rese-cel expansion was similar in patients with PV compared with other rese-cel-treated patients with AD who received LD. B-cell depletion was observed in all patients with PV, with 3 of 4 patients achieving B-cell aplasia. Elevations in serum B-cell activating factor (BAFF) level were observed, with 3 of 4 patients achieving levels within the lowest end of the range exhibited in rese-cel-treated patients with AD who received LD. PV autoantibodies decreased in 2 of 4 patients. These preliminary data suggest that LD may be dispensable for humanized CAR T-cell efficacy in patients with AD. This trial was registered at www.clinicaltrials.gov as NCT04422912.

IDH1 and IDH2 are frequently mutated in various cancers, including acute leukemias. However, the distinct mechanisms by which mutant IDH1 or IDH2 drive hematopoietic neoplasms remain poorly understood. Here, we analyzed DNA methylation in IDH1- and IDH2-mutant acute myeloid leukemia and found neutrophil lineage-specific epigenetic alterations in IDH1-mutant patients that went along with severely impaired neutrophil differentiation. Transcriptional analysis of normal hematopoiesis in humans and mice revealed a strong physiological upregulation of IDH1/Idh1 in myeloid progenitors. To study the functional effects of Idh1 mutations on hematopoiesis in a preleukemic setting, we used a genetically engineered inducible mouse model expressing a heterozygous Idh1 mutation under control of the endogenous promotor. Our study revealed a cell-intrinsic block in neutrophil differentiation caused by repression of myeloid transcription programs in neutrophil progenitors. This included impaired expression of Cebpe, which encodes a key transcription factor regulating neutrophil differentiation. Reactivation of Cebpe expression, by overexpression of its upstream regulator Cebpa or following treatment with hypomethylating agents, restored differentiation, indicating that the differentiation block is reversible. In summary, we found a reversible, preleukemic impairment of neutrophil differentiation in IDH1-mutant hematopoiesis that correlates with elevated IDH1 expression in myeloid progenitors and likely explains the strong association of IDH1 mutations with myeloid neoplasms.

Understanding how metabolism governs human hematopoietic stem cells (HSCs) function is essential for advancing regenerative therapies, yet direct metabolic profiling of human HSCs has been limited by their extreme scarcity and the technical limitations of conventional methods. Here, we applied a low-input mass spectrometry-based metabolomics platform, optimized for rare cell populations, to generate metabolic profiles of 13 immunophenotypically defined hematopoietic cell types from adult human bone marrow. Using as few as ∼10 000 cells per sample, we detected >80 metabolites and uncovered both conserved metabolic programs in primitive hematopoietic stem and progenitor cells (HSPCs) and lineage-specific metabolic specializations. Of note, we identified l-carnitine-driven fatty acid oxidation as a key metabolic feature supporting HSPC function. Mechanistically, l-carnitine activates the peroxisome proliferator-activated receptor alpha-transcription factor EB signaling axis, promoting mitochondrial metabolism and autophagy to preserve regenerative capacity. Functional assays in primary CD34+ HSPCs derived from healthy donors or patients with aplastic anemia confirm that l-carnitine supplementation improves stem cell function ex vivo and in vivo. This work provides a foundation for human hematopoietic metabolism and reveals a targetable metabolic circuit governing HSPC regenerative fitness with therapeutic potential for improving stem cell-based interventions.

Genetically modified T cells expressing chimeric antigen receptors (CARs) manufactured ex vivo have demonstrated high efficacy in patients with lymphoid hematologic malignancies, but their logistic complexity limits patient access. In vivo approaches generate the CAR-expressing T cells within the body but may have their own challenges. Recent clinical reports provide proof of concept for the feasibility and therapeutic potential of in vivo CAR gene delivery. We summarize clinical evidence and discuss the critical technical, biological, and safety considerations of this approach.

The BCL-2 inhibitor venetoclax has shown promise in acute lymphoblastic leukemia (ALL), but its role in first-line therapy for newly diagnosed (ND) Philadelphia chromosome-negative (Ph⁻) ALL is undefined. In this prospective phase 2 study, 167 adolescents and adults (aged 14-60 years) with ND Ph⁻ ALL received venetoclax combined with pediatric-inspired chemotherapy. The primary endpoint was the rate of measurable residual disease (MRD) negativity by multiparameter flow cytometry (MFC) after induction. The complete remission rate was 91.0%, and 73.0% of responders achieved MFC-MRD negativity, meeting the primary endpoint. After a median follow-up of 19.3 months, median overall and disease-free survival were not reached; estimated 2-year survival rates were 78.5% and 76.7%, respectively. Propensity score-matched analysis confirmed superior survival compared with historical chemotherapy-only controls. Grade ≥ 3 adverse events were primarily hematologic toxicities and infections, with an incidence comparable to that of the historical cohort. These results demonstrate that adding venetoclax to pediatric-inspired chemotherapy significantly improves MRD response and survival outcomes in ND Ph⁻ ALL, with a manageable safety profile. This trial was registered with ClinicalTrials.gov under the identifier NCT05660473.

Peripheral T-cell lymphoma (PTCL) represents a highly heterogeneous and aggressive lymphoid neoplasm, lacking pathogenic biomarkers of RNA modification with therapeutic potential. IGF2BP2 is recognized as an N6-methyladenosine (m6A) reader, critically involved in oncogenesis. In this study, we observed consistently high expression of IGF2BP2 across common nodal PTCL subtypes in three independent external cohorts, which was further confirmed in our RNA sequencing (RNA-seq) dataset of 196 patients with newly diagnosed PTCL. Both in vitro and in vivo, IGF2BP2 promoted tumor cell growth and inhibited CD8+ T cell infiltration within the tumor microenvironment. Mechanistically, IGF2BP2 bound to endosome-related genes (RAB4, VPS35, RAB9, and STAM) to maintain their stability, resulting in enhanced endocytic activity and increased internalization of membrane proteins, and ultimately induced tumor cell proliferation and inhibition of CD8+ T cell-mediated tumor cytotoxicity. The relationship between IGF2BP2 and endocytosis-associated genes was confirmed by RNA-seq data of PTCL patients. IGF2BP2 as an upstream regulator of both tumor growth and immune suppression was further demonstrated by patient-derived xenograft models and co-culture system established by tumor samples of PTCL patients and peripheral blood mononuclear cells. Of note, therapeutic targeting of IGF2BP2 with CWI1-2 suppressed endocytosis and impeded tumor growth in both cell lines and patient-derived xenograft models. Collectively, our findings highlight IGF2BP2 as a clinically relevant oncogenic driver in PTCL that integrates tumor-intrinsic growth signals with immune evasion through endocytosis-centered regulation, providing a novel therapeutic rationale for RNA modification-based strategies that concurrently target tumor cells and tumor microenvironment.

FLT3 internal tandem duplications (FLT3-ITD) are major genetic events in acute myeloid leukemia (AML). Although the clinical impact of FLT3-ITD "macroclones" (allelic ratio [AR] ≥0.05) is well established, the significance of low-level FLT3-ITD subclones ("microclones") remains uncertain. We conducted a post hoc analysis of 1733 patients with newly diagnosed AML enrolled in the Backbone Intergroup 1 trial (ClinicalTrials.gov identifier: NCT02416388). Using next-generation sequencing (NGS), we detected FLT3-ITD microclones (AR between 0.0004 and 0.05) in 17.4% of patients without FLT3-ITD macroclones. Microclones and macroclones (low and high AR) were independently associated with increased relapse risk (cause-specific hazard ratio, 1.50 [95% confidence interval (CI), 1.18-1.91]; 1.98 [1.50-2.62]; and 2.33 [1.69-3.22], respectively) after adjustment for age, white blood cell count, other gene mutations, midostaurin treatment, and allogeneic hematopoietic stem cell transplantation. At 2 years, the cumulative incidence of relapse reached 42.5% (95% CI, 37.0-47.9) in patients with macroclones, 45.1% (38.3-51.6) in patients with microclones, and 29.4% (26.6-32.3) in patients without FLT3-ITD. In NPM1-mutated AML, both microclones and macroclones were associated with higher levels of measurable residual disease (MRD) and increased relapse risk, without independent impact on overall survival after adjustment for MRD. An analysis of paired samples further revealed that 41.8% of relapses in patients with FLT3-ITD microclones at diagnosis were associated with a macroclone at relapse. These findings challenge current risk stratification models and support the integration of NGS-based FLT3-ITD detection into the diagnostic and prognostic workflow for AML. Prospective trials addressing the management of patients with FLT3-ITD microclones are warranted, as is their consideration in future European LeukemiaNet guidelines.

We identified biallelic loss-of-function BPNT1 mutations in 3 patients with recurrent vitamin B12-dependent megaloblastic anemia. Mechanistically, BPNT1 deficiency caused the accumulation of PAP (3'-phosphoadenosine 5'-phosphate), impaired ribosome biogenesis, and reduced ileal expression of the cubilin/amnionless receptor complex in Bpnt1-null mice.

Clonal acquisition of multiple chromosomal abnormalities in hematopoietic stem and progenitor cells (HSPCs) is a hallmark of high-risk acute myeloid leukemias with complex karyotype (AML-CK). AML-CK is associated with TP53 mutations and chromosome 5q deletions (del5q); however, the drivers and clonal trajectories of aneuploid evolution in HSPCs remain unknown. We have developed a patient-derived induced pluripotent stem cell (iPSC) model in which preleukemic HSPCs clonally evolve to distinct, highly aneuploid states following transient mitotic inhibition. By tracking chromosome evolution at single cell resolution, we show that TP53-mutant HSPCs with del5q, but not TP53- mutation alone, evolved complex chromosomal changes. Clonal evolution was marked by stepwise acquisition of numerical and structural chromosome changes seen in AML-CK patients, with individual abnormalities conferring fitness advantage. iPSC-derived aneuploid HSPCs and primary AML-CK patient samples exhibited a conserved gene expression signature marked by upregulation of PTEN, cohesins, and anti-apoptotic factor BCL2, indicative of a shared aneuploid cell state in HSPCs. Clinical BCL2 inhibitor venetoclax eradicated BCL2-dependent aneuploid clones, with resistant clones undergoing a lineage switch to upregulate alternative BCL2 factors. In summary, we demonstrate that mutant TP53 and del5q drive chromosome evolution marked by stepwise acquisition of individual abnormalities. Moreover, aneuploid HSPCs exhibit a shared gene expression state which confers unique targetable therapeutic vulnerabilities in AML-CK.

Uncertainty remains about whether sickle cell trait (SCT) shortens life or predispose to disease. Therefore, we examined whether SCT-carriers had increased risk of death or diseases linked to SCT. We studied 467,779 general population individuals from the UK Biobank. All had whole-exome sequencing performed and were followed prospectively for a median of 15 years. Individuals with SCT (n=1,253) were not at increased risk of all-cause death (hazard ratio[HR]:1.04;95%CI:0.84-1.29), cardiovascular death (1.34;0.90-2.00), or for having myocardial infarction (0.72;0.42-1.24), ischemic stroke (1.30;0.88-1.94), pulmonary embolism (1.29;0.84-1.99), or heart failure (0.79;0.55-1.14) compared to non-carriers. However, SCT-carriers had increased risk of diabetes (HR:1.30;95%CI:1.12-1.50), chronic kidney disease (HR:1.46;95%CI:1.18-1.80), and hypertension (odds ratio:1.24;95%CI:1.08-1.42). Surprisingly, risk of cardiovascular death was increased in SCT-carriers with diabetes when compared to non-carriers with diabetes (HR:2.17;95%CI:1.14-4.12). To examine whether selection bias may explain why previous studies based on hospital-diagnosed SCT found increased risk of cardiovascular disease, we repeated our analyses using hospital diagnoses of SCT from national registries, instead of defining SCT from genotyping. Individuals registered as SCT-carriers in hospital registries had markedly increased risk of all-cause death (HR:2.24;95%CI:1.42-3.52) and ischemic stroke (2.92;1.30-6.60), likely due to selection bias. In conclusion, SCT-carriers were not at increased risk of all-cause death or cardiovascular disease.

Patients with relapsed or refractory multiple myeloma (RRMM) with extraosseous extramedullary disease (EMD) have inferior outcomes and lack effective therapies. We developed anti-B-cell maturation antigen (anti-BCMA)/G protein-coupled receptor, class C group 5 member D (GPRC5D) bispecific chimeric antigen receptors (CARs) to investigate the activity and safety of the CAR T cells in patients with extraosseous EMD. In this single-arm, open-label, phase 2 trial, we enrolled 37 patients with RRMM with extraosseous EMD, and anti-BCMA/GPRC5D bispecific CAR T cells were administered at 2.0 × 106 CAR T cells per kg. At a median follow-up of 10.1 months (interquartile range, 6.4-19.1), 36 of 37 patients (97%) obtained an overall response and measurable residual disease negativity, including 16 (43%) with stringent complete response. The median progression-free survival was 5.8 months (95% confidence interval, 2.2-9.4), and the median overall survival was not reached. The most common grade 3 or worse adverse events were hematologic toxicities (except lymphopenia; 37/37). Twenty-seven patients (73%) experienced cytokine release syndrome, all cases of which were grade 1 or 2. Two patients (5%) had grade 1 or 3 immune effector cell-associated neurotoxicity syndrome. These findings support that anti-BCMA/GPRC5D bispecific CAR T cells induced a high response rate in patients with RRMM with extraosseous EMD, and the safety profile was manageable. This ongoing trial is registered at www.clinicaltrials.gov as NCT05509530.