The progression of multiple myeloma (MM), an incurable malignancy of plasma cells, is often associated with the suppression of ferroptosis, a type of cell death driven by iron-dependent lipid peroxidation. The mechanisms underlying this suppression remain largely unknown. Here, we identified STK17B kinase as a critical suppressor of ferroptosis in MM. Elevated levels of STK17B are associated with poor overall survival in MM patients and STK17B expression is significantly higher in relapsed vs newly diagnosed MM cases. We found that inhibiting STK17B in MM cells increased the labile iron pool, enhanced lipid peroxidation, and sensitized cells to conventional anti-MM therapies. Notably, an orally available, in-house-generated STK17B inhibitor induced ferroptosis and significantly reduced tumor growth in MM xenograft mouse models. Mechanistically, proximity labeling assay combined with the phospho-proteomic analysis identified two major regulators of iron uptake and transport as direct targets of STK17B: iron-responsive element binding protein 2 (IREB2) and heat shock protein family B member 1 (HSPB1). We demonstrated that STK17B phosphorylates critical regulatory sites on IREB2 (S157) and HSPB1 (S15), thereby modulating the balance between IREB2 and HSPB1 downstream effectors, pro-ferropototic transferrin receptor and anti-ferroptotic ferritin heavy chain proteins. Furthermore, we demonstrated that STK17B indirectly maintains activating phosphorylation of STAT3, a ferroptosis suppressor and a major driver of MM pathobiology. Our findings uncovered a clinically relevant and targetable STK17B-pIREB2S157/pHSPB1S15 signaling axis that suppresses ferroptosis and contributes to drug resistance in MM.

The IELSG37 trial enrolled 545 patients with primary mediastinal B-cell lymphoma (PMBCL) and demonstrated that consolidation radiotherapy (RT) can be omitted in patients with complete metabolic response (CMR), defined by the Lugano classification as Deauville score (DS) 1-3. This report evaluates outcomes following different frontline rituximab- and doxorubicin-based immunochemotherapy regimens chosen according to local practice. Patients treated with R-CHOP21 showed a significantly higher percentage of DS 5 than those on other regimens (23.8% vs. 8.2% average, P< 0.001) as well as a trend toward additional unplanned treatments (53.2% vs. 46.9%, P=0.30). The increased risk of poor response was confirmed in a multinomial logistic regression analysis adjusted for age, sex, IPI score, and performance status. R-CHOP21 was also associated with smaller reductions in MTV and less pronounced decreases in SUVmax. Patients with DS 5 more often received additional treatment (RT and/or salvage chemotherapy with or without autologous consolidation) after induction immunochemotherapy (96% vs. 41%, P< 0.001) and experienced significantly poorer outcomes. Although differences in progression-free and overall survival between R-CHOP21 and more aggressive regimens were not statistically significant, R-CHOP21 may increase the risk of additional treatments and may be inadvisable as frontline therapy for PMBCL. NCT01599559.

HHV-6 reactivation in CAR T-cell recipients is reported to be rare. Our patient cohort (n=119) experienced a seven-fold higher incidence of viraemia than a previous study and 2 encephalitis cases. Further studies are needed to determine risk factors for infection.

Isatuximab is an IgG1k monoclonal antibody that binds with high affinity to CD38 expressed on plasma cells. Anti-CD38 antibodies have shown efficacy as monotherapy and in combination in a variety of settings for patients with multiple myeloma and light chain (AL) amyloidosis. This multi-center, cooperative group phase 2 trial was designed to evaluate hematologic response, organ response, and safety of isatuximab monotherapy for the treatment of relapsed AL amyloidosis. Isatuximab at 20 mg/kg was administered intravenously weekly during the first 28-day cycle and then every other week during cycles 2-24. Forty-three patients were registered, with 35 patients being evaluable for response. The overall hematologic response rate was 77.1%, with 57% of patients achieving a VGPR or better. The median time to partial response or better was 1.1 months. Renal response occurred in 50% (7/14) of patients with renal involvement and cardiac response occurred in 57% (8/14) of patients who were evaluable utilizing NT-pro-BNP with cardiac involvement. The most common treatment related grade ≥3 adverse events included lymphopenia (n=3, 8.5%) and infection (n=2, 6%). Isatuximab demonstrated substantial efficacy in previously treated patients with AL amyloidosis and was associated with a good safety profile. This trial was registered at www.clinicaltrials.gov as NCT#03499808.

Hepcidin is the key hyposideremic hormone produced primarily by the liver. However, recent reports reveal extra-hepatic functional sources of hepcidin, including the intestine, the site of dietary iron absorption. To determine whether intestinal hepcidin may play a role in plasma iron lowering, we generated transgenic mice overexpressing the peptide specifically in this tissue. At one month of age, transgenic mice exhibited severe iron deficiency along with decreased haematological indices and a drastic suppression of liver hepcidin in response to hyposideremia. Mechanistically, we showed that intestinal hepcidin was produced in the intestine lumen, inducing a striking down-regulation of Divalent Metal Transporter 1 (DMT1) protein at the enterocyte. To confirm the capacity of hepcidin to decrease DMT1, we developed food-grade recombinant lactic acid bacteria (recLAB) genetically modified to deliver hepcidin directly into the intestinal lumen. These recLAB induced a rapid decrease of duodenal DMT1 and, most importantly, when daily orally administrated, protected against iron overload in a mouse model of hemochromatosis. Taken together, our data reveal a previously unrecognized role of intestinal hepcidin as a regulator of systemic iron homeostasis, acting on DMT1 on the apical side of enterocytes, with potential therapeutics relevance for haematological or iron disorders.

Long-term maintenance of somatic stem cells relies on precise regulation of self-renewal and differentiation. Understanding the molecular framework for these homeostatic processes is essential for improved cellular therapies and treatment of myeloid neoplasms. CUX1 is a widely expressed, dosage-sensitive transcription factor crucial in development and frequently deleted in myeloid neoplasia in the context of -7/(del7q). Here, using novel mouse models and single-cell approaches, we report that dynamic and distinct CUX1 levels are integral to hematopoietic stem cell (HSC) activity. Knockdown of CUX1 reverses HSC differentiation and strikingly re-endows progenitors with stem cell function, accompanied by restoration of the HSC transcriptome and DNA accessibility landscape. CUX1 mediates these activities, in part, via suppressing endogenous retroelements (EREs) and the ensuing interferon-stimulated gene expression program. Both EREs and the interferon response are upregulated in CUX1-deficient acute myeloid leukemia (AML), suggesting a conserved role of CUX1 in regulating these elements. These data establish an unexpected entwinement of stem cell-intrinsic innate immune activation and the transcriptional programs of stem cell identity. Further, we reveal the profound effects of transcription factor levels in cell fate.

Hematopoietic stem cells (HSCs) responsible for blood cell production and their bone marrow regulatory niches undergo age-related changes, impacting immune responses and predisposing individuals to hematologic malignancies. Here, we show that the age-related alterations of the megakaryocytic niche and associated downregulation of Platelet Factor 4 (PF4) are pivotal mechanisms driving HSC aging. PF4-deficient mice display several phenotypes reminiscent of accelerated HSC aging, including lymphopenia, increased myeloid output, and DNA damage, mimicking physiologically aged HSCs. Remarkably, recombinant PF4 administration restored old HSCs to youthful functional phenotypes characterized by improved cell polarity, reduced DNA damage, enhanced in vivo reconstitution capacity, and balanced lineage output. Mechanistically, we identified LDLR and CXCR3 as the HSC receptors transmitting the PF4 signal, with double knockout mice showing exacerbated HSC aging phenotypes similar to PF4-deficient mice. Furthermore, human HSCs across various age groups also respond to the youthful PF4 signaling, highlighting its potential for rejuvenating aged hematopoietic systems. These findings pave the way for targeted therapies aimed at reversing age-related HSC decline with potential implications in the prevention or improvement of the course of age-related hematopoietic diseases.

Multiple myeloma (MM) continues to be an incurable malignancy, even with recent therapeutic advancements. While epigenetic dysregulation at cis-regulatory elements is known to drive disease progression, the complete molecular mechanisms underlying these alterations are poorly understood. Using ATAC-seq analysis combined with computational footprinting of CD138+ cells from 55 MM patients, we depicted the dynamic changes in chromatin accessibility during disease progression and identified Nuclear Respiratory Factor 1 (NRF1) as a master regulator of vital MM survival pathways. We demonstrated that NRF1 maintains proteasome homeostasis by orchestrating the ubiquitination pathway, which is essential for MM cell survival. We discovered a novel enhancer element that physically interacts with the NRF1 promoter, sustaining its expression. Targeting this enhancer RNA reduced NRF1 levels and increased tumor cell sensitivity to bortezomib (BTZ), suggesting therapeutic potential. In xenograft models, we showed that antisense oligonucleotides (ASOs) targeting the NRF1 enhancer, either alone or combined with BTZ, significantly decreased tumor burden and improved survival. Our findings reveal a previously unknown NRF1-dependent mechanism regulating MM cell survival and present a promising therapeutic approach through manipulation of its regulatory network.

Epcoritamab is a subcutaneous CD3xCD20 bispecific antibody approved as monotherapy for relapsed/refractory (R/R) follicular lymphoma (FL). We evaluated fixed-duration epcoritamab with rituximab plus lenalidomide (R2) in R/R FL in arm 2 of EPCORE® NHL-2 (phase 1b/2; NCT04663347). Patients received epcoritamab (2 step-up doses, then 48-mg full doses) for up to 2 years and R2 for up to 12 cycles (28 days/cycle). Primary endpoint was overall response rate (ORR) per investigator assessment (Lugano criteria). As of September 21, 2024, 108 patients received ≥1 epcoritamab dose in expansion (median follow-up, 28.2 months). Median age was 65 years; 57% had 1 prior line of therapy. ORR and complete response (CR) rate were 96% and 88%; CR rates in patients with high-risk features were 90% (primary refractory), 82% (refractory to anti-CD20 and an alkylating agent), and 83% (disease progression within 24 months of first-line therapy). Two-year estimates for remaining in CR, progression-free survival, overall survival, and not starting next antilymphoma therapy were 82%, 76%, 90%, and 84%, respectively. Minimal residual disease negativity was observed in 86% of evaluable patients (clonoSEQ® assay). Common treatment-emergent adverse events (TEAEs) included neutropenia (65%), COVID-19 (59%), and cytokine release syndrome (CRS; 51%). Grade (G) ≥3 TEAEs occurred in 87% of patients; 5 had G5 TEAEs (all COVID-19). CRS events were mostly low grade (38% G1, 11% G2, 2% G3), all resolved, and none led to epcoritamab discontinuation. Fixed-duration epcoritamab plus R2 demonstrated deep, durable responses with manageable safety and favorable outcomes in R/R FL, irrespective of risk features.

Von Willebrand disease (VWD)-type 1 is a bleeding disorder characterized by a quantitative deficiency of functional von Willebrand factor (VWF). We designed a novel bispecific nanobody, named KB-V13A12, that aims to increase endogenous VWF levels by bridging it to albumin. KB-V13A12 comprises two single-domain antibodies, one targeting VWF and one targeting albumin. VWF bound efficiently to the albumin/KB-V13A12 complex (2.0±0.4 nM) in immunosorbent assays and binding was stable at pH 5.6 and 7.4. VWF ristocetin activity and factor VIII binding remained unaffected in the presence of a 100 to 200-fold molar excess of KB-V13A12/albumin. Humanized VWD-type 1 mice were used for in vivo analysis. A single subcutaneous dose of KB-V13A12 (5 mg/kg) was associated with a nanobody half-life of 3.0±0.7 days and dose-dependently increased VWF in VWD-type 1 mice 1.4 to 2.1-fold for up to 14 days. FVIII activity was also increased during this period. The VWF-propeptide/VWF-antigen ratio (a marker for VWF clearance) was significantly reduced in the presence of KB-V13A12, suggesting that delayed clearance contributes to increased VWF levels. Clearance experiments in wild-type mice using recombinant VWF pre-incubated with KB-V13A12 indeed confirmed a prolonged survival, while this prolongation was absent in FcRn-deficient-mice. Finally, treatment with KB-V13A12 resulted in a significantly improved bleeding tendency in VWD-type 1 mice when using the saphenous vein puncture-model. In conclusion, KB-V13A12 is a bispecific nanobody that efficiently increases functional levels of endogenous VWF, and could be a therapeutic option to treat VWD-type 1.

Platelets in peripheral blood critically drive clot formation in health and disease. Previously considered to uniformly respond to vascular injury and inflammatory cues, recent studies have highlighted that circulating platelets exhibit marked heterogeneity, with distinct populations contributing differentially to hemostasis, thrombosis, and inflammation. In this Review, we highlight platelet diversity as a consequence of origin (i.e., megakaryocyte diversity), of circulatory age (i.e., young vs. aged platelets), and, specifically, as a sequela of and contributing factor to cardiovascular and inflammatory diseases. This diversity includes reticulated platelets, newly released from the bone marrow, RNA-rich, and highly prothrombotic, versus aged platelets, which exhibit altered receptor expression and pro-inflammatory rather than hemostatic features. We further describe how platelet subsets actively shape disease progression: Hyperreactive reticulated platelets drive arterial thrombosis, while procoagulant platelets amplify fibrin formation in venous thromboembolism. In chronic inflammation, interactions of immune-responsive platelets with leukocyte subsets facilitate their recruitment and impact on polarization, but can also promote endothelial dysfunction and immune hyperactivation, perpetuating thromboinflammatory dysregulation. Moreover, platelet phenotypes are dynamically regulated by disease states, with systemic inflammation, altered shear forces, and metabolic stress influencing platelet turnover, activation thresholds, and functional specialization. Recognizing platelet heterogeneity in disease pathogenesis could provide new opportunities for precision medicine, potentially allowing stratification of thrombotic risk and differential tailoring of antiplatelet and anti-inflammatory therapies.