VCAR33, a donor-derived CD33-directed chimeric antigen receptor (CAR) T cell product, was developed to decrease relapse of high-risk acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) after allogeneic hematopoietic cell transplantation (alloHCT). We describe pre-clinical characterization of the VCAR33 construct, which was optimized for long-term anti-tumor surveillance based on killing and persistence assays. Prior to its use in post-alloHCT maintenance, we evaluated safety and efficacy of VCAR33 in a phase 1/2 clinical study for adults with relapsed or measurable residual disease (MRD)-positive CD33+ AML/MDS after alloHCT. Fifteen patients received VCAR33 across 2 arms stratified by disease burden: 7 patients in Arm A (bone marrow blasts ≥ 5%) at dose level 1 (DL1; 1 x 106 CAR+ T cells/kg) and 8 patients in Arm B (bone marrow blasts < 5%) at DL1 (n=5) and DL2 (3 x 106 CAR+ T cells/kg; n=3). The study ended for non-safety reasons before escalation to DL3 (1 x 107 CAR+ T cells/kg) and maximum tolerated dose was not determined. The most common treatment-related adverse event was cytokine release syndrome (93.3%; all < grade 3). Four patients (26.7%) experienced immune cell-associated neurotoxicity syndrome (1 ≥ grade 3) and 1 patient (6.7%) had grade III acute graft-versus-host disease within 28 days of VCAR33 infusion. Fourteen patients (93.3%) had transient VCAR33 expansion. Overall response rate was 20%: 2 patients had complete remission with incomplete count recovery in Arm A and 1 Arm B patient achieved MRD clearance. This allogeneic CAR T product demonstrated acceptable safety and preliminary anti-leukemic activity. ClinicalTrials.gov: NCT05984199.

Immune thrombocytopenia (ITP) is associated with a variable and unpredictable clinical course in children, including a spectrum of bleeding and systemic symptoms in the months following diagnosis. Although many children will have spontaneous resolution of disease prior to 1 year, up to 30% will go on to develop chronic disease. Known predictors for developing chronic ITP are limited, making clinical management and guidance during this early course of disease very challenging. Additionally, the pathophysiology of immune dysregulation in ITP is complex, with multiple variables likely contributing to the development of chronic disease. We aimed to create a statistical model to predict development of chronic ITP. Utilizing a retrospective training cohort of 611 children with ITP from two institutions and two validation cohorts comprised of 161 children, we developed and validated a multivariable logistic regression model and found that age, sex, IgG, IgA, IgM, presenting platelet count, presenting lymphocyte count, known secondary cause at diagnosis, and DAT positivity were useful in predicting chronic ITP. The external validations demonstrated consistent discriminative performance and clinical utility. The model is available for use at https://opal.shinyapps.io/citp-rm/. A chronicity prediction tool to use at the time of ITP diagnosis will better equip hematologists to counsel patients and families and engage in appropriate treatment strategies for individual patients earlier in their course.

We found that PSMD1, a key subunit of the 19S proteasome regulatory particle, was overexpressed and correlated with poor prognosis in multiple myeloma (MM). Genetic depletion of PSMD1 decreased cancer cell viability, induced polyubiquitinated protein accumulation, and promoted apoptosis. Proteomic analysis revealed the activation of immune-related pathways, suggesting the potential for immune modulation. Targeting PSMD1 with siRNA, delivered via lipid nanoparticles (LNPs), reduced tumor growth in MM cell lines and primary patient samples while sparing normal cells. It also overcame proteasome inhibitor resistance and the protective effects of the bone marrow milieu. In MM xenograft mouse models, PSMD1 siRNA LNPs significantly reduced tumor growth and prolonged survival. In addition, PSMD1 depletion had similar effects on other types of cancer cell lines. These findings position PSMD1 as a critical target in cancer therapy, with broad implications for overcoming drug resistance, improving therapeutic outcomes, and potentially impacting immune responses across various cancers. These findings provide a foundation for the clinical development of PSMD1-targeted therapies in myeloma and other malignancies.

Caring for individuals with hematological disorders is increasingly complex, and with medical complexity often comes ethical complexity. Prognostic uncertainty, stakeholder conflicts, and myriad other ethical challenges often contribute to situations that can benefit from ethics support. Through the presentation of three vignettes focusing on ethical dilemmas arising from hematology cases, we review the four phases of clinical ethics consultation: consult triage; ethics consult intake; stakeholder meeting(s) and additional data collection; and ethics analysis and recommendations. In tandem, we review some of the most common ethical framework/approaches used to inform hematology ethics consultation support services. We conclude that ethics consult services can be a valuable resource in providing care for patients with blood disorders and are a vital resource to enhance patient care, support clinicians, and ensure that difficult choices are navigated with clarity, compassion, and integrity.

The Bcl2 inhibitor venetoclax in combination with the hypomethylating agents azacitidine (ven/aza) has become increasingly utilized clinically for the treatment of many hematological malignancies. Whilst its effects on malignant cells have been extensively studied, its impact to the surrounding bone marrow microenvironment (BME) remains unexplored. In this study, we report that ven/aza therapy causes significant damage to the BME of mice. Comparatively high Bcl2 expression in the sinusoidal endothelial cell compartment (SEC) amongst all stromal subtypes, results in high sensitivity to ven/aza treatment, causing selective depletion of SECs and breakdown in cell-cell communication pathways in the endothelial cell (EC) network, leading to vascular leakiness in the BM. Furthermore, our detailed transcriptomic and imaging studies reveals significant downregulation of essential adhesion molecules in residual SECs, leading to significant defects in human hematopoietic stem/progenitor cell (HSPC) homing and engraftment of hematopoietic stem cells (HSCs) after ven/aza treatment. To conclude, our study showcases that maintaining SEC integrity in response to ven/aza therapy may play a key factor in achieving effective engraftment of donor derived HSCs.

Infection remains a leading cause of morbidity in multiple myeloma. Preventing infections is paramount and immune profiling could reflect the cumulative effect of host, tumor and treatment-related immunosuppression. However, current understanding of immune dysfunction and its association with infection is limited. To address this gap in knowledge and identify immune biomarkers of increased infection risk, we performed immune profiling using next-generation flow cytometry in bone marrow and peripheral blood samples from 1,786 patients at various disease stages and treatment scenarios. Patients developing infection had significantly lower percentages of CD27+ B cells and CD27- NK cells, as well as increased CD27-/CD27+ T-cell ratio in bone marrow. These immune risk factors were validated in three independent datasets. An immune score was developed to stratify patients with ≤1 vs ≥2 of the aforementioned risk factors, which was associated with higher infection incidence (35% vs 60%, P <.001). The immune score (odds ratio: 2.31, P <.001), disease stage and CD38, BCMA or GPRC5D targeted therapy were independently associated with infection incidence. All cell types detectable in bone marrow and peripheral blood were significantly correlated, suggesting that immune biomarkers of increased infection risk could be monitored using minimally-invasive methods that are available in routine laboratories.

BCMA- or GPRC5D-directed T-cell immunotherapies have substantially improved the survival of patients with relapsed/refractory multiple myeloma (MM). Despite these advances, a subset of patients does not respond, and most patients will eventually relapse. Tumor heterogeneity, resulting in rapid selection of both antigen-negative and antigen-low cells, is a critical issue affecting response to T-cell immunotherapies targeting single tumor-associated antigens. In addition, antigen escape (due to deletions, mutations, or epigenetic alterations) is frequently observed in patients who experience disease progression after CAR T-cell infusion or during BsAb treatment. Simultaneous targeting of two tumor-associated antigens may improve efficacy by addressing heterogeneous target expression and preventing antigen escape. Various dual-targeting strategies are currently evaluated in MM, including the combination of two single-antigen targeting BsAbs. Notably, the efficacy of the combination of teclistamab and talquetamab appears to have enhanced anti-MM activity, compared to the corresponding conventional BsAbs alone in similar patient populations. Furthermore, dual-antigen targeting with T-cell redirecting trispecific antibodies (e.g., ramantamig [BCMAxGPRC5D] and ISB2001 [BCMAxCD38]) has already demonstrated promising results in heavily pretreated MM with several studies ongoing in earlier stages of the disease. Studies with limited numbers of patients have demonstrated that CAR T-cell products with specificity for more than one antigen are also effective in advanced MM, but at this time none of the dual-targeting CAR T-cell products is clearly superior to targeting BCMA alone with ciltacabtagene autoleucel (cilta-cel). Dual-targeting should eventually be compared in large phase 3 trials with the classical approach of serial treatment with mono-targeting agents with target switch.

Circular RNAs are a novel class of RNA transcripts, which regulate important cellular functions in health and disease. Herein, we report on the functional relevance of circPCMTD1 in BCR/ABL1-positive myeloid leukemias. In screening experiments, we found that circPCMTD1 depletion strongly inhibited the proliferative capacity of leukemic cells with BCR/ABL1 translocations. RNA sequencing and mass cytometry experiments identified aberrant activation of the DNA damage response (DDR) pathway as a downstream effect of circPCMTD1 depletion. DNA fiber assays, Comet assays and profiling of DDR markers (phospho-H2AX, phospho-CHK1, etc.) further underscored the pronounced effect of circPCMTD1 depletion in increasing genotoxic stress and inhibiting leukemic cell growth. circPCMTD1 targeting also led to aberrant DDR activation in leukemia patient blasts with BCR/ABL1 translocations. In in vivo experiments, circPCMTD1 knock-down prolonged the survival of mice engrafted with BCR/ABL1-positive leukemia cells. Mechanistically, we found that circPCMTD1 is enriched in the cytoplasm and associates with the ribosomes of leukemic blasts. We detected a cryptic open reading frame within the circPCMTD1 sequence and found that circPCMTD1 generates a 127 amino-acid peptide product (cPCMTD1-127aa). Using a custom-produced antibody, we found that the cPCMTD1-127aa interacts with the BCR/ABL1 oncoprotein, as well as with the BLM, TOP3A and RMI1 proteins, which form the BTR complex and regulate DNA repair and genome stability. cPCMTD1-127aa enhanced BTR complex formation, thereby increasing cellular tolerance to genotoxic stress. In summary, we identify and characterize circPCMTD1 as a molecular vulnerability and potential therapeutic target in BCR/ABL1-positive leukemias.

Acute myeloid leukemia (AML) is a complex hematological malignancy with multiple disease sub-groups defined by somatic mutations and heterogeneous outcomes. Although genome-wide association studies (GWAS) have identified a small number of common genetic variants influencing AML risk, the heritable component of this disease outside of familial susceptibility remains largely undefined. Here we perform a meta-analysis of four published GWAS plus two new GWAS, totalling 4710 AML cases and 12938 controls. We identify a new genome-wide significant risk locus for pan-AML at 2p23.3 (rs4665765; P=1.35x10-8; EFR3B, POMC, DNMT3A, DNAJC27) which also significantly associates with patient survival (P=6.09x10-3). Our analysis also identifies three new genome-wide significant risk loci for disease sub-groups, including AML with deletions of chromosome 5 and/or 7 at 1q23.3 (rs12078864; P=7.0x10-10; DUSP23) and cytogenetically complex AML at 2q33.3 (rs12988876; P=3.28x10-8; PARD3B) and 2p21 (rs79918355; P=1.60x10-9; EPCAM). We also investigated loci previously associated with risk of clonal hematopoiesis (CH) or clonal hematopoiesis of indeterminate potential (CHIP) and identified several variants associated with risk of AML. Our results further inform on AML etiology and demonstrate the existence of disease sub-group specific risk loci.