The discovery of calreticulin (CALR) mutations in patients with myeloproliferative neoplasms (MPN) has paved the way for the elucidation of a unique disease mechanism that is particularly well-suited to targeting by biologics. All MPN-associated pathogenic CALR mutations are characterized by a frameshift, resulting in translation of the same neoantigen peptide. This neoantigen directly activates the thrombopoietin receptor, leading to uncontrolled neoplastic cell proliferation. Current therapeutic approaches for MPN are focused primarily on blood count control. Furthermore, current approaches are neither disease-modifying nor clonally selective. However, as the mutant CALR neoantigen peptide is functional and not expressed in normal physiology, it is an ideal drug target. Here, we review the structure and function of mutant CALR, including the subtle yet clinically and therapeutically relevant differences between the two most commonly occurring types of mutation. We also review the current therapeutic landscape for CALR-mutated MPN, highlighting the areas in which current approaches are inadequate. Finally, we review ongoing clinical and preclinical experimental approaches for targeting mutant CALR in MPN in a clonally selective manner using monoclonal antibodies, bispecific antibodies, cancer vaccination, chimeric antigen receptor T cells, and antibody-drug conjugates. Taken together, we expect that ongoing developments in mutant CALR-targeted therapeutics will lead to promising novel strategies for long-term disease control.

T-cell acute lymphoblastic leukemia (T-ALL) represents a group of aggressive hematological malignancies characterized by unfavorable prognosis, urging the need for innovative therapeutic strategies. LEF1 is a member of the lymphoid enhancer factor/T-cell factor (LEF/TCF) family of DNA-binding transcription factors, known for their interaction with nuclear β-catenin in the context of the Wnt signaling pathway. Although LEF1's implication in colon cancer is well-documented, its clinical relevance and functional consequences remain elusive in T-ALL. In this study, we provide valuable insights into the prevalence and significance of LEF1 alterations in a comprehensive cohort of 474 pediatric and adult T-ALL patients enrolled in the FRALLE 2000 and GRAALL-2003-2005 trials (NCT00222027; NCT00327678) respectively. LEF1 alterations were detected in 63 cases (13%), including 9 point-mutations (14.3%), 18 large deletions (28.6%), and - strikingly - 36 focal deletions (57.1%), which emerge as the most recurrent subtype. LEF1-altered cases were associated with increased central nervous system involvement and improved initial treatment response. Importantly, we unveil the existence of a previously undescribed dominant-negative LEF1 isoform resulting from focal deletions of the exons 2-3. This novel truncated protein, previously unreported in the literature, is associated with the disruption of the Wnt pathway and TCR signaling, which can be exploited as a therapeutic strategy to enhance chemosensitivity in LEF1-deleted T-ALL cases.

Fetal hemoglobin (HbF) reactivation is a promising therapy for β-hemoglobinopathies. We developed a prime-editing strategy that introduces multiple mutations in the fetal γ-globin promoters that are expected to increase their activity. We tested multiple targets and optimized a variety of parameters to achieve ~50% of precise edits in a hematopoietic cell line, with minimal off-targets effects. This work improved our understanding of the complex DNA repair mechanisms involved in prime editing. We tested this strategy in patients' hematopoietic stem/progenitor cells (HSPCs). Although the editing efficiency was variable amongst donors, erythroid clones carrying multiple mutations express a significantly higher γ-globin level compared to cells carrying individual mutations, confirming the potential therapeutic benefit of our combined strategy for patients with β-hemoglobinopathies.

Adoptive transfer of NK cells can induce complete remissions in 30-50% of patients with refractory acute myeloid leukemia and lymphoma. While blood chimerism occurs, attaining functional homing to the site of tumor without exhaustion has been elusive. During chronic infections and tumorigenesis, exposure to activating stimuli weakens the effector activity of NK cells. Despite this knowledge, there is little known about the mechanisms that govern this dysregulation and whether these disparate activating stimuli use distinct pathways to downregulate effector immunity. In this study, we reveal that chronic NK cell activating receptor (NKAR) stimulation and chronic IL-15 exposure impart distinct modes of dysregulation, with NKAR stimulation inducing a tissue resident-like state that resembles that of tumor-infiltrating NK cells in cancer patients. Using loss- and gain-of-function studies, we identify the transcription factor KLF2 as a master regulator of the NK cell response to chronic activation and provide evidence that KLF2 overexpression promotes NK cell cytotoxicity, cytokine production, and chemotaxis, and inhibits the development of dysfunctional, tissue resident-like features. Using KLF2 reporter mice, we show that in certain tissues, tissue resident NK cells are predominantly KLF2-negative while circulating NK cells in these tissues are overwhelmingly KLF2+. Lastly, using mixed bone marrow chimeras, we demonstrate that conditional KLF2 deficiency in NK cells leads to altered homing and the acquisition of tissue resident-like features in vivo. Together, these findings highlight the profound changes NK cells undergo during prolonged activation and advance our understanding of how some NK cell therapies fail during malignant relapse.

Platelets are dynamic cells that perform vital roles both in thrombosis and in immune regulation. Platelets are activated through well described signaling pathways following injury to the vascular wall to prevent excess bleeding and initiate vascular repair. However, platelet functions extend beyond this initial physical phase of platelet activation, through their expression and secretion of angiogenic factors and immune mediators that initiate wound healing and recruit leukocytes to prevent infection. Not only do activated platelets induce inflammation and vascular repair but circulating resting platelets maintain vascular integrity and immune homeostasis. Furthermore, many studies have shown that platelets are not homogenous, demonstrating transcriptomic and proteomic differences that associate with platelet phenotypes and functions in multiple disease states. Platelets are produced by megakaryocytes that are found not only in the bone marrow but also in the lungs and spleen. Megakaryocytes within the bone marrow are heterogeneous, which may contribute to platelet heterogeneity. Additionally, lung megakaryocytes are immune-differentiated compared to those in other tissues and proportionately produce more platelets at times of increased demand, perhaps adding to platelet heterogeneity in disease contexts. In this review, we will discuss underlying mechanisms that may lead to platelet heterogeneity impacting both health maintenance and disease.

Artificial intelligence (AI) and its subdiscipline, machine learning (ML), have the potential to revolutionize health care, including hematology. The diagnosis and treatment of hematologic disorders depend on the integration of diverse data sources, such as imaging, pathology, omics, and laboratory parameters. The increasing volume and complexity of patient data have made clinical decision-making more challenging. AI/ML hold significant potential for enhancing diagnostic accuracy, risk stratification, and treatment response prediction through advanced modeling techniques. Generative AI, a recent advancement within the broader field of AI, is poised to have a profound impact on health care and hematology. Generative AI can enhance the development of novel therapeutic strategies, improve diagnostic workflows by generating high-fidelity images or pathology reports, and facilitate more personalized approaches to patient management. Its ability to augment clinical decision-making and streamline research represents a significant leap forward in the field. However, despite this potential, few AI/ML tools have been fully implemented in clinical practice due to challenges related to data quality, equity, advanced infrastructure, and the establishment of robust evaluation metrics. Despite its promise, AI implementation in hematology faces critical challenges, including bias, data quality issues, and a lack of regulatory frameworks and safety standards that keep pace with rapid technological advancements. In this review, we provide an overview of the current state of AI/ML in hematology as of 2025, identify existing gaps, and offer insights into future developments.

Desmopressin (DDAVP) is often administered to correct factor VIII (FVIII) levels in female hemophilia A carriers (HACs). However, the post-DDAVP FVIII pharmacokinetic profiles have been reported only in small series in HACs. Therefore, this study analyzed the post-DDAVP FVIII and von Willebrand factor (VWF) response in 361 HACs. A population pharmacokinetic/pharmacodynamic model was developed to analyze the VWF and FVIII levels by taking into account the F8 gene variants (n = 143 [39.6%] with null; and n = 218 [60.4%] with non-null variants), demographic and laboratory covariates. The before/after DDAVP mean basal, peak and recovery FVIII activity (FVIII:C) levels were 0.34 IU/mL (0.08-0.65), 1.13 IU/mL (0.19-2.69), and 2.85 IU/mL (1.06-7.13), respectively. Peak FVIII:C was ≥0.5 IU/mL in 95.6% (345/361) and ≥0.8 IU/mL in 78.7% (284/361) of patients. The covariate analysis showed a poorer DDAVP FVIII:C response for null than non-null F8 variants: lower mean FVIII:C peak (1.04 vs 1.23 IU/mL; P < 5 × 10-5) and patients percentage with normalized FVIII:C (91.6% vs 98.1%; P = .0068), higher mean FVIII:C clearance (5898.83 vs 2704.06 IU/h; P = 1.58 × 10-15), lower mean FVIII:C area under the curve during the first 12 hours (AUC0-12h =7.73 vs 9.06 IU/mL per hour; P < 5 × 10-6), and shorter mean time with FVIII:C ≥0.8 IU/mL (1.9 vs 4.1 hours; P < 6 × 10-6). HAC with body weight <35 kg had lower peak FVIII:C, higher FVIII:C clearance, lower AUC0-12h, and shorter time with FVIII:C ≥0.8 IU/mL than HAC with body weight 35 to 70 kg. In HACs, the post-DDAVP FVIII response is strongly influenced by the F8 genotype and body weight.

Transfusion-related acute lung injury (TRALI) is a leading cause of transfusion-related mortality. Though the precise mechanism is not fully understood, a two-hit model is widely accepted, involving both a predisposing patient condition and the transfusion itself. Mitochondrial damage-associated molecular patterns (mtDAMPs), such as mitochondrial DNA (mtDNA) and N-formylated peptides (NFPs), are elevated in trauma patients and stored blood products, and have been implicated in adverse transfusion outcomes, prompting us to investigated whether mtDAMPs could serve as a priming "first-hit" in TRALI. Using a murine model, we found that injection of purified mitochondria followed by a monoclonal anti-major histocompatibility complex class I (MHC class I) antibody (34-1-2s) induced significantly greater lung injury compared to the isotype control. This was evidenced by increased pulmonary edema, elevated plasma macrophage inflammatory protein-2 (MIP-2), enhanced neutrophil lung infiltration, hypothermia, and respiratory distress. Similar effects were observed using a Toll-Like Receptor 9 agonist (ODN 2395), purified mtDNA, and a synthetic NFP (WKYMVm), agonist of Formyl Peptide Receptor (FPR). Notably, a TLR9 antagonist blocked the mtDAMP-induced TRALI response, whereas two FPR antagonists did not, underscoring a key role for mtDNA and TLR9 signaling in disease priming. These findings suggest that mtDAMPs, particularly mtDNA, present in both transfusion products and recipient plasma may predispose patients to antibody-mediated TRALI. Targeting mtDAMPs or their receptors may offer a novel therapeutic strategy to mitigate TRALI risk.

Until recently, the JAK1/2 inhibitor ruxolitinib (Jakafi) was the only therapy for steroid-refractory acute graft-versus-host disease approved by the US Food and Drug Administration (FDA) for use in patients aged >12 years. The FDA has now approved a potent mesenchymal stromal cell product, remestemcel-L-rknd (Ryoncil), for children aged ≤18 years, showing 70% response rates and ∼70% 6-month survival. In this spotlight, we highlight this important advance in the field.

Functional high-risk (FHR) multiple myeloma (MM) is defined as an unexpected, early relapse (ER) of disease in the absence of baseline molecular or clinical risk factors (RF), making FHR MM inherently dependent on which RFs were assessed at diagnosis, but also on what treatment patients received. To establish the true incidence of FHR, we analysed uniformly treated, transplant-eligible (TE) patients from the UK NCRI Myeloma-XI trial that had been profiled for IMS/IMWG defined high-risk cytogenetic aberrations (HRCA) and the SKY92 gene expression HR signature (GEP-HR). 135 TE MyXI patients meeting these criteria were studied, with a median follow-up of 88 months. 25 patients (18.5%) experienced ER, defined as relapse <18 months from maintenance randomization post-autologous stem-cell transplantation. Hereof, 15 (60%) were classified as IMS/IMWG-HR at diagnosis, of whom 8 were also GEP-HR. Another 6 patients were GEP-HR only and would have been missed by IMS/IMWG-HR. Among 4 patients with both IMS/IMWG- & GEP-standard risk (SR), 2 had isolated HR markers at diagnosis, leaving only 2 patients (8% of ER; 1.5% of all) truly meeting all FHR criteria. The combination of IMS/IMWG-HR and GEP-HR profiling identified 84% of ER, and differentiated long-term outcome across all 135 patients: co-occurring IMS/IMWG-HR and GEP-HR was associated with very short overall survival compared to the absence of both (HR=13.1, 95%-CI: 6.5-26.1, P<0.0001), followed by GEP-HR only (HR=5.1, 95%-CI: 2.4-11.1, P<0.0001) and IMS/IMWG-HR only (HR=3.2, 95%-CI: 1.6-6.2, P=0.0007). Our results support more comprehensive baseline diagnostic profiling to identify those at risk of ER upfront. ISRCTN49407852, NCT01554852.

Two gene therapy products have been FDA approved for sickle cell disease. Nearly all patients in the clinical trials that led to approval were either sickle hemoglobin gene homozygotes (sickle cell anemia) or had HbS-β0 thalassemia. HbSC disease, caused by compound heterozygosity for HbS and HbC genes, is the second most common genotype of sickle cell disease. Gene therapy has not been tested in HbSC disease patients who are severely symptomatic. We discuss the pathophysiology and clinical features of HbSC disease, and how gene therapy is likely to provide a curative option for some individuals. We also discuss the mechanism through which HbF and HbF-like HbA (HbAT87Q) might mitigate adverse clinical outcomes and end-organ damage in HbSC disease and other compound heterozygous sickle hemoglobinopathies.