Isatuximab is an immunoglobulin G1κ 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 multicenter, 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 IV weekly during the first 28-day cycle, and then every other week during cycles 2 to 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 very good partial response (VGPR) or better. The median time to partial response (PR) 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 N-terminal pro b-type natriuretic peptide (NT-proBNP) 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 #NCT03499808.

Hepcidin is the key hyposideremic hormone produced primarily by the liver. However, recent reports reveal extrahepatic 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 1 month of age, transgenic mice exhibited severe iron deficiency along with decreased hematologic 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 downregulation 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 therapeutic relevance for hematologic 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 for 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 reendows 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, suggesting a conserved role of CUX1 in regulating these elements. These data establish an unexpected entwinement between stem cell-intrinsic innate immune activation and the transcriptional programs of stem cell identity. Furthermore, 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, affecting 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 low-density lipoprotein receptor and C-X-C motif chemokine receptor 3 as HSC receptors transmitting the PF4 signal, with double knockout mice exhibiting 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. Although epigenetic dysregulation at cis-regulatory elements is known to drive disease progression, the complete molecular mechanisms underlying these alterations are poorly understood. Using Assay for Transposase-Accessible Chromatin with high-throughput sequencing analysis combined with the computational footprinting of CD138+ cells from 55 patients with MM, 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 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 the manipulation of its regulatory network.

Epcoritamab is a subcutaneous CD3×CD20 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). 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 per cycle). The primary end point was overall response rate (ORR) per investigator assessment (Lugano criteria). As of 21 September 2024, 108 patients received ≥1 epcoritamab dose in expansion (median follow-up, 28.2 months). Median age was 65 years; 57% had 1 previous line of therapy. ORR and complete response (CR) rate were 96% and 88%, respectively; 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 ≥3 TEAEs occurred in 87% of patients; 5 had grade 5 TEAEs (all COVID-19). CRS events were mostly low grade (grade 1, 38%; grade 2, 11%; grade 3, 2%), 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. This trial was registered at www.ClinicalTrials.gov as #NCT04663347.

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 2 single-domain antibodies, 1 targeting VWF and 1 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. Factor VIII 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 preincubated 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 (ie, megakaryocyte diversity), circulatory age (ie, young vs aged platelets), and, specifically, as both a sequela of and a contributing factor to cardiovascular and inflammatory diseases. This diversity includes reticulated platelets (RPs), newly released from the bone marrow, RNA-rich, and highly prothrombotic, vs aged platelets, which exhibit altered receptor expression and proinflammatory rather than hemostatic features. We further describe how platelet subsets actively shape disease progression. Hyperreactive RPs drive arterial thrombosis, whereas 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.

Because frail patients and patients aged ≥80 years with chronic lymphocytic leukemia (CLL) are still underrepresented in clinical trials, the CLL-Frail trial aimed to evaluate the efficacy and safety of acalabrutinib in these patients. The primary end point was the overall response rate (ORR) after 6 cycles of treatment to test the null hypothesis of ORR ≤65%. Fifty-three patients were included in the trial, and 34 patients are still on therapy. Adverse events (AEs) were the most frequent reason for early discontinuation (10 patients), whereas 5 patients stopped treatment because of death. Median age was 81 years, and 47.2% of patients were frail. The ORR for the 46 patients receiving ≥3 cycles of treatment was 93.5% (95% confidence interval, 82.1-98.6) meeting the primary end point of this trial (P < .001). The estimated 12-month progression-free and overall survival rates were 93.3% and 95.7%, respectively, after a median follow-up of 19 months. 53.5% of patients reported an improvement in their self-perceived frailty. Although all patients experienced AEs, and severe (Common Terminology Criteria of ≥3) events were reported in 63.5% of patients, there were no events of severe bleeding and atrial fibrillation was rare (2 cases of Common Terminology Criteria Grades 2 and 3). Five patients died, of which 4 deaths happened during or <28 days after treatment. Infections/COVID-19 were the cause of death in 3 cases. To our knowledge, this is the first prospective trial in older and/or frail patients with CLL demonstrating a high efficacy and safe treatment with acalabrutinib monotherapy. This trial was registered at www.ClinicalTrials.gov as #NCT04883749.

The significance of endogenous immune surveillance in acute lymphoblastic leukemia (ALL) remains controversial. Using clinical B-cell ALL samples and a novel mouse model, we show that neoantigen-specific CD4+ T cells are induced to adopt type 1 regulatory (Tr1) function in the leukemia microenvironment. Tr1 cells then inhibit cytotoxic CD8+ T cells, preventing effective leukemia clearance. Leukemic cells induce Tr1 cells by phenocopying hematopoietic stem cells, which normally are subject to effective surveillance by this CD4+ subset. This mechanism effectively redirects Tr1 cells from a role in preventing cancer to maladaptively promoting clinical relapse. In mouse models, addition of interleukin-10 receptor (IL-10R) blockade to cytotoxic therapy modestly affected Tr1 development but was insufficient to improve leukemia control. In contrast, combined therapy with a cytotoxic agent and anti-PDL1 blockade eradicated measurable residual disease. This correlates with polarization of the neoantigen-specific CD4+ T-cell population from Tr1 toward T helper 1 (Th1) states. Our findings uncover a mechanism that enables leukemic relapse and resolves existing controversies on the role of immune surveillance toward this cancer type. Therapeutic polarization of neoantigen-specific CD4+ T cells away from Tr1 and toward Th1 states may improve contemporary immune therapies by reshaping the immune microenvironment toward states permissive for cytotoxic attack of residual leukemia.

Innate lymphoid cells (ILCs) are tissue-resident lymphocytes that regulate tissue homeostasis and immune responses. How ILCs modulate T cells, remains incompletely understood. To investigate the interaction between ILCs and T cells, we differentiated ILC2s and ILC3s from hematopoietic stem cells (HSCs). Both suppressed T-cell proliferation, enhanced cytokine production, and upregulated T-cell senescence-associated surface receptors (CD57, KLRG1, TIGIT, and TIM3). T cells exposed to ILCs also increased expression of senescence-related proteins, including p16, p21, p53, GATA4, and NF-κB. Mechanistically, ILCs produced interleukin-9 (IL-9), and IL-9 blockade prevented ILC-driven T-cell senescence. Conversely, addition of exogenous IL-9 to T cells recapitulated the effects of ILC coculture. Finally, in both human xenogeneic and murine allogeneic hematopoietic cell transplantation models, we observed ILC-mediated T-cell modulation in vivo, with evidence of T-cell senescence. In conclusion, HSC-derived ILCs from both humans and mice mitigate graft-versus-host disease by inducing T-cell senescence.