Rare thrombotic events associated with ChAdOx1 nCoV-19 (ChAdOx1) vaccination have raised concerns; however, the underlying mechanisms remain elusive. Here we report a novel biophysical mechanism by which ChAdOx1 directly interacts with platelets under arterial shear conditions, potentially contributing to post-vaccination arterial thrombosis. Using microfluidic post assays, we demonstrate that ChAdOx1 induces shear-dependent platelet aggregation, distinct from conventional von Willebrand factor-mediated adhesion. This interaction is mediated by platelet integrin αIIbβ3 and requires biomechanical activation, explaining the absence of significant binding under static conditions. Molecular dynamics simulations and docking studies reveal preferential binding of ChAdOx1's penton RGD motif to the activated conformation of αIIbβ3. Inhibiting integrin αIIbβ3 completely abolishes ChAdOx1-induced platelet aggregation, whereas blocking GPIb has minimal effect, confirming a mechanism that bypasses the conventional GPIb-dependent platelet adhesion pathway. Mutagenesis of the RGD motif to AAA eliminates platelet binding, verifying the specificity of this interaction. These findings provide a potential explanation for the association between ChAdOx1 vaccination and arterial thrombotic events, distinct from vaccine-induced immune thrombotic thrombocytopenia (VITT). Our results highlight the importance of considering biomechanical factors in vaccine-related thrombotic complications and suggest that shear-dependent integrin activation may be another determinant in the pathogenesis of these rare adverse events.

Insufficient eradication of cancer cells and survival of drug tolerant clones are major relapse driving forces. Underlying molecular mechanisms comprise activated pro-survival and anti-apoptotic signaling leading to insufficient apoptosis and drug resistance. The identification of programmed cell death pathways alternative to apoptosis opens up for possibilities to antagonize apoptosis escape routes. We have earlier shown that acute lymphoblastic leukemia (ALL) harbours a distinct propensity to undergo cell death by RIPK1-dependent necroptosis, activated by small molecule second mitochondria-derived activators of caspase (SMAC) mimetics. Despite demonstrated safety and tolerability of SMAC mimetics in clinical trials, their efficacy as single agent appears still limited, highlighting the need for combinatorial treatments. Here, we investigate so far unexplored regulatory mechanisms of necroptosis and identify targets for interference to augment the necroptotic anti-leukemia response. Ex vivo drug response profiling in a model of the bone marrow microenvironment reveals powerful synergy of necroptosis induction with histone deacetylase inhibition. Subsequent transcriptome analysis and functional in vivo CRISPR screening identify gene regulatory circuitries through the master transcription regulators SP1, p300 and HDAC2 to drive necroptosis. While deletion of SP1 or p300 confers resistance to necroptosis, loss of HDAC2 sensitizes to RIPK1-dependent cell death by SMAC mimetics. Consequently, our data inform strong in vivo anti-leukemic activity of combinatorial necroptosis induction and HDAC inhibition in patient-derived human leukemia models. Thus, transcriptional dependency of necroptosis activation is a key regulatory mechanism that identifies novel targets for interference, pointing out a strategy to exploit alternative non-apoptotic cell death pathways to eradicate resistant disease.

Following the introduction of tyrosine kinase inhibitors (TKI), the number of patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) for chronic phase chronic myeloid leukemia (CP-CML) has dramatically decreased. Imatinib was the 1st TKI introduced into the clinical arena, predominantly utilized in the 1st line setting. In cases of insufficient response, resistance, or intolerance, CML patients can subsequently be treated with a 2nd, 3rdor 4th generation TKI. However, despite the approval of 1st, 2nd, 3rd, 4th generation TKI allo-HSCT still remains indicated for a minority of CML patients. Here, we discuss the indications in the era of TKI through different cases representing the clinical situations for which allo-HSCT remains the best option. We also propose our transplant strategy to decrease transplant-related morbidity, particularly graft-versus-host disease (GvHD), and mortality in the particular context of CML, a disease that is one of the most sensitive to immune cellular therapy, allowing the use of a combination of donor lymphocyte infusion (DLI) and TKI for post-transplant molecular progression.

In 2013, we published a perspective entitled, "The myth of the second remission of acute leukemia," which underscored the dismal outcomes of relapsed acute leukemia in adults. We emphasized that only a minority of patients achieved second complete remission (CR2) after relapse and were subsequently eligible to receive a potentially curative allogeneic hematopoietic stem cell transplantation (HSCT). Hence, we urged the leukemia community not to delay HSCT in first complete remission (CR1) if indicated to avoid dire outcomes. Historically, poor outcomes resulted from suboptimal frontline therapy, inadequate risk stratification, and lack of effective agents to achieve CR2. In the past decade, remarkable progress has been made in the treatment paradigm of acute leukemia, most evidently in B-cell acute lymphoblastic leukemia. Key advancements include refinement of frontline treatment, incorporation of early immunotherapy, improved disease risk stratification based on molecular profiling and assessment of measurable residual disease, and discovery of highly effective salvage immunotherapies. These innovations have led to a high rate of cure by frontline therapy, precise selection for HSCT in CR1 for high-risk patients, and the reality of HSCT for patients in CR2. Here, we reexamine the myth of CR2 given the progress in the field.

Graft-versus-Host disease (GvHD) ensues as the most common non-relapse complication after allogeneic hematopoietic cell transplantation (allo-HCT). A pivotal goal in GvHD management revolves around quelling inflammation. Phagocytic clearance of inflammatory cells contributes substantially to termination of inflammatory processes. Nevertheless, the precise functions of phagocytosis in GvHD remain largely unclear. In this study, we identified the "don't eat me"-signal CD47 as a promising target for therapeutic interventions aimed at eradicating alloreactive T-cells subsequent to allo-HCT. Analysis of global data sets revealed a remarkable upregulation of CD47 expression on T-cells residing in the ileum of patients with inflamed intestine. Building on this finding, we examined CD47 levels in the gastrointestinal tract (GIT) following allo-HCT. Our work not only confirmed upregulated CD47 expression in the GIT of GvHD patients, but also identified CD47 on T-cells in the ileum of GvHD mice after allo-HCT. Additionally, we found that activated donor T-cells suppress antibody-dependent cellular phagocytosis (ADCP) via CD47 signaling in vitro. Application of anti-CD47 antibodies significantly invigorated the impaired ADCP of activated T-cells. Administering anti-CD47 antibodies to mice elevated phagocytosis of T-cells in the GIT, induced immunosuppressive responses and improved survival. Finally, transplantation of CD47 deficient donor T-cells significantly improved clinical GvHD score with improved survival after allo-HCT. Collectively, our findings illuminate CD47 upregulation as pivotal mechanism in GvHD patients, leading to impaired phagocytic clearance of alloreactive T-cells. This study proposes that anti-CD47 treatment could rectify the compromised phagocytosis of alloreactive T-cells, thereby aiding in the resolution of inflammation after allo-HCT.

We carried out a single-cell (sc) multiomic analysis on a series of MYD88 mutated Waldenström macroglobulinemia (WM) cases and identified two distinct subtypes of disease, memory B-cell-like (MBC-like) and plasma cell-like (PC-like), based on their expression of key lineage defining genes. Biologically, the subtypes are characterized by their variable capacity to differentiate fully towards a plasma cell (PC) and exhibit unique transcriptomic, chromatin accessibility, and genomic profiles. The MBC-like subtype is unable to differentiate beyond the memory B-cell (MBC) stage, upregulates key MBC genes, and is characterized by upregulated BCR and AKT/mTOR signaling. In contrast, the PC-like subtype can partially differentiate towards a PC, upregulates key PC genes, has enhanced NF-kB signaling, and has an upregulated unfolded protein response. Pseudotime trajectory analysis of combined scRNA-sequencing and scATAC-sequencing supports the variable differentiation capacity of each subtype and implicate key transcription factors SPI1, SPIB, BCL11A, and XBP1 in these features. The existence and generalizability of the two disease subtypes were validated further using hierarchical clustering of bulk RNA-seq data from a secondary set of cases. The biological significance of the subtypes was further established using whole genome sequencing, where it was shown that CXCR4, NIK, and ARID1A mutations occur predominantly in the MBC-like subtype and 6q deletions in the PC-like subtype. We conclude that the variable differentiation blockade seen in WM manifests itself clinically as two disease subtypes with distinct epigenetic, mutational, transcriptional, and clinical features with potential implications for WM treatment strategies.

We sought to develop a survival model in chronic myelomonocytic leukemia (CMML) that is primarily based on clinical variables and examine additional impact from mutations and karyotype. 457 molecularly-annotated patients were considered. Multivariable analysis identified circulating Blasts ≥2% (1 point), Leukocytes ≥13 x 109/L (1 point), and severe (2 points) or moderate (1 point) Anemia as preferred risk variables in developing a clinical risk Stratification Tool for overall survival (OS), acronymized to "BLAST": low-risk (0 points; median 63 months); intermediate-risk (1 point; median 28 months; HR 2.2, 95% CI 1.6-3.0), and high-risk (2-4 points; median 13 months; 5.4, 4.1-7.3); the corresponding 3/5 year OS rates were 68%/53%, 43%/18%, and 12%/1%. BLAST model performance (AUC 0.77/0.85 at 3/5-years) was shown to be comparable to that of the molecular CMML-specific prognostic scoring system (CMML-mol; AUC 0.73/0.75) and the international prognostic scoring system-molecular (IPSS-M; AUC 0.73/0.74). Multivariable analysis of mutations and karyotype identified PHF6MUT and TET2MUT as being "favorable" and DNMT3AMUT, U2AF1MUT, BCORMUT, SETBP1MUT, ASXL1MUT, NRASMUT, PTPN11MUT, RUNX1MUT, TP53MUT, and adverse karyotype, "unfavorable". Molecular information was subsequently encoded in a combined clinical-molecular risk model (BLAST-mol; AUC 0.80/0.86 at 3/5-years) that included the aforementioned BLAST clinical risk variables and a 3-tiered molecular risk score. BLAST and BLAST-mol were subsequently validated by two separate external cohorts. Independent risk factors for blast transformation included DNMT3AMUT, ASXL1MUT, PHF6WT, leukocytes ≥13 x 109/L, and ≥2% circulating or ≥10% bone marrow blasts. The current study proposes an easy to implement, globally applicable, and molecularly adaptive risk model for CMML.

The prognosis for relapsed or refractory (R/R) nucleophosmin 1-mutated (NPM1m) acute myeloid leukemia (AML) is poor and represents an urgent unmet medical need. Revumenib, a potent, selective menin inhibitor, was recently approved for the treatment of R/R acute leukemia with a KMT2A translocation in patients aged ≥1 year based on results from the phase 1/2 AUGMENT-101 study. Here we present results from patients with R/R NPM1m AML enrolled in the phase 2 portion of AUGMENT-101. Enrolled patients received revumenib with or without a strong CYP3A4 inhibitor every 12 hours in 28-day cycles. Primary endpoints were rate of complete remission (CR) or CR with partial hematologic recovery (CRh; CR+CRh), and safety and tolerability. Secondary endpoints included overall response rate (ORR) and duration of response. As of September 18, 2024, 84 patients received ≥1 dose of revumenib. Median age was 63 years; 1 patient was aged <18 years. The protocol-defined efficacy-evaluable population for the primary analysis included 64 adult patients (≥3 prior lines of therapy, 35.9%; prior venetoclax, 75.0%). The CR+CRh rate was 23.4% (1-sided P=.0014); the ORR was 46.9%. Median duration of CR+CRh was 4.7 months. Five of 30 responders (16.7%) proceeded to hematopoietic stem cell transplant (HSCT); 3 resumed revumenib after HSCT. Treatment-related adverse events led to treatment discontinuation in 4 patients (4.8%). Revumenib demonstrated clinically meaningful responses in this heavily pretreated, older population with NPM1m AML, including remissions that enabled HSCT. The safety profile of revumenib was consistent with previously reported results. This trial was registered at www.clinicaltrials.gov as NCT04065399.

Small molecules that inhibit LSD1 (lysine-specific demethylase 1, KDM1A) have been shown to induce abundant fetal hemoglobin (HbF) levels in red blood cells both in vitro and in vivo, therefore potentially serving as potent and cost-effective therapeutics to treat the β-globinopathies, sickle cell disease (SCD) and β-thalassaemia major (TM). However, most LSD1 inhibitors (LSD1i) that induce HbF in vivo are covalent and irreversible, which leads to adverse effects. In this study, we utilized structure-aided drug design to develop potent new reversible LSD1i's leading to robust γ-globin expression in vitro. Moreover, in a mouse model of SCD, oral administration of these novel inhibitors lead to significant HbF elevation and alleviation of multiple features of disease pathology that are the usual consequences of SCD. In addition, we discovered that combined treatment of an LSD1i with a BRD4 degrader (BD-9136) represses the induction of RUNX1 and PU.1, thereby rescuing the erythroid to myeloid lineage conversion that accompanies LSD1i in hematopoiesis. The data indicate that this new generation of LSD1i can effectively induce HbF levels, reduce SCD pathologies, and are well-tolerated by oral administration in SCD mice. We anticipate that the combination of these or related binary compounds offer exciting new therapeutic possibilities for treating SCD and TM.