"Nonclassical" myeloproliferative neoplasms (MPNs) and myelodysplastic/myeloproliferative neoplasms (MDS/MPNs) represent a heterogeneous group of malignancies characterized by a wide range of clinical manifestations. Unlike classical MPNs, there is no standardized management approach for these conditions, particularly concerning the indications for and management of allogeneic hematopoietic cell transplantation. To address this gap, the European Society for Blood and Marrow Transplantation (EBMT) Practice Harmonization and Guidelines (PH&G) Committee and the Chronic Malignancies Working Party (CMWP) have collaborated to develop shared guidelines aimed at optimizing the selection and management of patients with these rare forms of neoplasms. A comprehensive review of the literature from the publication of the revised fourth edition of the (2016) World Health Organization classification onward was conducted. A multidisciplinary group of experts in the field convened to produce this document, which was developed through multiple rounds of draft circulation. Key recommendations include the early identification of potential transplant candidates, particularly in cases of chronic neutrophilic leukemia, chronic eosinophilic leukemia (CEL)/CEL, not otherwise specified (CEL-NOS), myeloid/lymphoid neoplasm with eosinophilia and tyrosine kinase gene fusions with FGFR1, JAK2, ABL1, and FLT3 rearrangements, MDS/MPN with neutrophilia/atypical chronic myeloid leukemia, and MDS/MPN, NOS. For patients with MPN, NOS/MPN unclassifiable, standard recommendations for myelofibrosis should be applied. Similarly, in MDS/MPN with thrombocytosis, transplantation is recommended on the basis of established MDS guidelines. Given the current lack of robust evidence, this document will serve as a valuable resource to guide future research activities, providing a framework for addressing critical unanswered questions and advancing the field.

Despite recent advances in graft-versus-host disease (GVHD) prophylaxis, novel approaches to effective prevention of chronic GVHD (cGVHD) remain of high importance. In this prospective, multicenter, phase 2 trial, ruxolitinib, an oral inhibitor of Janus kinase (JAK) 1 and 2, was administered as maintenance therapy after reduced-intensity allogeneic hematopoietic cell transplantation (HCT). GVHD prophylaxis consisted of tacrolimus and methotrexate. Ruxolitinib began between day +30 to 100 and was administered continuously in 28-day cycles for up to 24 cycles. Seventy-eight participants were enrolled before HCT; 63 participants received the intervention. The median start date of ruxolitinib after HCT was day +45. The most common grade ≥3 adverse events were neutropenia, thrombocytopenia, and anemia. Seven participants experienced grade ≥3 infectious events. GVHD-free, relapse-free survival at 1 year after HCT, the primary end point, was 70%. Grade 3 to 4 acute GVHD at 6 months was 4.8%, and moderate-severe cGVHD at 2 years was 16%. cGVHD requiring systemic therapy was 9.5% at 1 year and 13% at 2 years. Overall survival and progression-free survival at 2 years were 76% and 68%, respectively. Prolonged administration of ruxolitinib following HCT is associated with low rates of clinically significant cGVHD. The incorporation of JAK inhibition into GVHD prevention approaches warrants further investigation. This trial was registered at www.clinicaltrials.gov as #NCT03286530.

Phosphoinositide 3-kinase gamma (PI3Kγ), the only class IB PI3 kinase, is a cell-extrinsic immunotherapy target in solid tumors. PI3Kγ inhibition reprograms immunosuppressive myeloid cells to acquire immunostimulatory phenotypes, which promote antitumor cytotoxic T-cell activity. Although PI3Kγ inhibition has no direct effect on solid tumor cells, several new studies have nominated PI3Kγ as a cell-intrinsic target in various leukemias, particularly acute myeloid leukemia. Intrinsic dependency on PI3Kγ is present at baseline in leukemias with specific pathological characteristics, is inducible by extrinsic inflammation in others, and may also be acquired with resistance to certain therapies. The discovery of leukemia PI3Kγ dependency has generated enthusiasm for immediate clinical trial evaluation of inhibitor monotherapy and combinations. Parallel laboratory evaluation is needed to develop an improved understanding of leukemia disease features associated with clinical inhibitor sensitivity that might suggest biomarker-directed patient enrichment strategies. In this review, we discuss recent progress credentialing PI3Kγ as a bona fide target in leukemia. We also highlight open questions, including a need to understand the mechanism of acquired resistance to PI3Kγ inhibition, how to optimally prioritize combination therapies to enhance PI3Kγ inhibitor utility, and how cell-extrinsic effects of PI3Kγ inhibition in the leukemia microenvironment might also contribute to clinical activity.

Emerging evidence indicates that CD4+ T cells contribute to antitumor immunity beyond their traditional roles as helpers or regulators. However, the specific subset of CD4+ T cells mediating beneficial outcomes in patients with multiple myeloma remains unclear. Here, we performed single-cell RNA sequencing and T cell receptor sequencing on CD4+ T cells sorted from the bone marrow of patients across the stages of myeloma progression. We identified several distinct states of CD4+ cytotoxic T lymphocytes (CTLs) that were significantly increased and clonally expanded in myeloma patients. CD4+ CTLs displayed transcriptional and phenotypic characteristics indicative of cytotoxicity, demonstrating their ability to directly kill myeloma cells. This cytotoxicity, however, was abrogated by NKG2D blockade. Notably, the abundance of NKG2D+CD4+ CTLs correlated with improved survival in myeloma patients. Our findings suggest that harnessing CD4+ CTLs could lead to novel strategies for enhancing immunotherapy outcomes in multiple myeloma.

The half-life of recombinant human von Willebrand factor (rVWF) expressed in CHO cells (CHO-rVWF; Vonicog alfa; and Vonvendi/Veyvondi) is significantly longer than that of plasma-derived VWF (pdVWF). This finding is intriguing because CHO cells do not generate α2-6 sialylation, which constitutes the majority of human pdVWF sialylation. We hypothesized that glycan differences might regulate the longer half-life of CHO-rVWF. In lectin plate-binding assays and liquid chromatography-mass spectrometry analysis, we confirmed that CHO-rVWF lacked α2-6-linked sialylation. Conversely, however, α2-3-linked sialylation was significantly increased on CHO-rVWF, which also had reduced exposed β-galactose (β-Gal) compared to pdVWF. Consistent with human data, CHO-rVWF clearance was significantly (P < .001) reduced in VWF-/- mice compared to pdVWF. However, clearance of asialo-pdVWF and asialo-CHO-rVWF were identical. In keeping with the in vivo half-life prolongation, CHO-rVWF binding to murine macrophages (P = .012) and HepG2 cells (P = .001) was significantly decreased compared to pdVWF. Furthermore, CHO-rVWF binding to purified macrophage-galactose-type lectin (MGL) receptor and asialoglycoprotein receptor (ASGPR) was also significantly reduced. In contrast to pdVWF, in vivo studies in MGL1-/- mice and Asgr1-/- mice demonstrated that neither MGL nor ASGPR plays significant roles in regulating CHO-rVWF clearance. Together, our findings demonstrate that enhanced α2-3-linked sialylation on CHO-rVWF is responsible for its extended half-life.

We used single-cell genomics to characterize a patient with T-cell acute lymphoblastic leukemia treated in the Children's Oncology Group AALL0434 trial with poor clinical outcome despite favorable genomic features, identifying a STAT1-mediated interferon-related transcriptional signature and inflammatory microenvironment associated with sensitivity to small-molecule JAK inhibition.

The MCL35 gene expression assay encompasses key risk features and stratified older patients with mantle cell lymphoma (MCL) using routine biopsies. In the SHINE trial, high-risk patients had poor outcomes despite adding ibrutinib to bendamustine-rituximab, highlighting an urgent need for novel strategies in high-risk MCL.

Tyrosine kinase inhibitors (TKIs) are the mainstay of treatment for patients with chronic myeloid leukemia. The standard dose has been established for each drug according to the indication for the various stages of the disease and whether as initial therapy or after failure of previous therapies. The recommended doses are fixed for all patients and dose adjustments are mostly recommended for management of adverse events. The standard doses have been derived largely from phase 1 studies, but as we discuss in this review, the current model may not be optimal for this purpose for drugs such as TKIs that are meant to be used for extended periods of time. Subsequent studies have led to changes in the initial recommendations for some drugs. In others, experience and real-world data have led to the use of TKIs using doses and adjustments that may be different than what clinical trials have recommended. In other scenarios, available data suggest that the current standard dose may need to be revisited. It may also be time to reconsider the standard approach of starting therapy with the standard dose and adjusting merely based on adverse events. We propose a flexible model that perhaps reflects more accurately what is being done frequently in the clinic.

G protein-coupled receptor, class C, group 5, member D (GPRC5D) has emerged as a novel target for chimeric antigen receptor (CAR) T-cell therapy, demonstrating promising efficacy in multiple myeloma (MM). However, disease relapse is still common, and the mechanism of resistance remains poorly understood. In this study, we conducted whole-genome sequencing (WGS) and whole-genome bisulfite sequencing (WGBS) on MM samples from 10 patients who relapsed after GPRC5D CAR T-cell therapy. Among these patients, 8 had GPRC5D loss, while 2 presented mixed expression (GPRC5D+/-). Genetic alterations were identified in three cases: one had a homozygous deletion in the GPRC5D gene, another had a biallelic loss in the regulatory regions of GPRC5D, and the third had homozygous deletions in both TNFRSF17 and GPRC5D after sequential anti-BCMA and anti-GPRC5D CAR T-cell therapies. No genetic changes were detected at GPRC5D locus in the remaining 7 cases. However, multiple hypermethylation sites were present in the transcriptional regulatory elements of the GPRC5D gene in 5 post-treatment MM samples. In MM cell lines, GPRC5D expression was inversely correlated with methylation levels in its regulatory regions. Furthermore, azacitidine treatment induced GPRC5D mRNA and protein expression in hypermethylated MM cell lines. Our findings highlight that biallelic genetic inactivation and hypermethylation-driven epigenetic silencing are key mechanisms contributing to GPRC5D loss and treatment resistance.

Rilzabrutinib is a covalent, reversible Bruton tyrosine kinase inhibitor targeting multiple immune thrombocytopenia (ITP)-related mechanisms. The phase 3 LUNA3 study in previously treated adults with persistent/chronic ITP evaluated oral rilzabrutinib 400 mg twice daily (n = 133) vs placebo (n = 69) for 24 weeks. At baseline overall, median age was 47 years, 63% female, 7.7 year median ITP duration, and 28% prior splenectomy. Overall (N = 202), 85 (64%) rilzabrutinib and 22 (32%) placebo patients achieved platelet response (≥50 × 109/L or 30 × 109/L to <50 × 109/L and doubled from baseline) during the first 12 weeks and were eligible to continue. The primary end point, durable platelet response (platelet count ≥50 × 109/L for ≥two-thirds of ≥8 of the last 12 of 24 weeks without rescue therapy), was observed in 31 (23%) rilzabrutinib vs 0 placebo patients (P < .0001). All secondary efficacy end points were significantly superior for rilzabrutinib (P < .05). Median time to first platelet response was 15 days in rilzabrutinib responders. Rilzabrutinib significantly reduced rescue therapy use by 52% (P = .0007) and improved week 25 bleeding scores (P = .0006). Improved physical fatigue was sustained from week 13 (P = .01) through 25 (P = .0003). Treatment-related adverse events were mainly grade 1/2. One rilzabrutinib patient with multiple risk factors had serious treatment-related grade 3 peripheral embolism (lower left leg), and another died from unrelated pneumonia. Rilzabrutinib in patients who failed multiple previous ITP therapies showed rapid and durable platelet response, reduced rescue medication and bleeding, improved physical fatigue, and favorable safety. Trial registration: www.clinicaltrials.gov (#NCT04562766) and www.clinicaltrialsregister.eu (#2020-002063-60).

The CREBBP lysine acetyltransferase (KAT) is frequently mutated in follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) and has been studied using gene knock-out (KO) in murine and human cells. However, the majority of CREBBP mutations encode amino acid substitutions within the catalytic KAT domain (CREBBP KAT-PM) that retain an inactive protein and have not been extensively characterized. Using CRISPR gene editing and extensive epigenomic characterization of lymphoma cell-lines, we found that CREBBP KAT-PM lead to unloading of CREBBP from chromatin, loss of enhancer acetylation and prevention of EP300 compensation. These enhancers were enriched for those that are dynamically loaded by CREBBP in the normal centroblast-to-centrocyte transition in the germinal center, including enhancers activated in response to CD40 signaling, leading to blunted molecular response to CD40 ligand in lymphoma cells. We provide evidence that CREBBP KAT-PM inhibits EP300 function by binding limiting quantities nuclear transcription factor, thereby preventing its compensatory activity. This effect can be experimentally overcome by expressing saturating quantities of transcription factor, or biologically attenuated by strong stimulation of CD40 signaling that increases nuclear transcription factor abundance. Importantly, epigenetic responses to CD40 signaling can be induced by enforcing CD4 T-cell engagement using a bispecific antibody, leading to CD40-dependent restoration of antigen presentation machinery in CREBBP KAT-PM cells and cell death. We therefore provide a mechanistic basis for enhancer deregulation by CREBBP KAT-PM and highlight enforced CD4 T-cell engagement as a potential approach for overcoming these effects.

Chronic granulomatous disease (CGD) is an inborn error of immunity characterized by defective NAD phosphate oxidase function, leading to impaired microbial killing, recurrent infections, and granulomatous inflammation. Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for CGD, particularly effective when a fully HLA-matched donor is available. However, the place of HLA-haploidentical HSCT remains less established. This retrospective multicenter study analyzed outcomes of 64 patients with CGD (53 males; 46 with X-linked CGD) who underwent a first HSCT with HLA-haploidentical family donors, with either in vitro T-cell receptor (TCR)αβ/CD19 depletion or in vivo depletion using posttransplant cyclophosphamide (PTCY). The mean age at transplant was 5.8 years (range, 0-33). Patients exhibited a high disease burden before HSCT, with 45% experiencing infections in the 6 months before HSCT and 67% exhibiting inflammation. Outcomes in the entire cohort showed a 3-year overall survival, event-free survival (EFS), and grade 3 to 4 graft-versus-host disease (GVHD)-free EFS of 75.9%, 70.2%, and 56.1%, respectively, and were not affected by the type of depletion or age. The cumulative incidence (CI) of primary graft failure (PGF) was 20.6%. The CI of grade 2 to 4 acute GVHD was higher in the PTCY group (P = .04), whereas the CI of grade 3 to 4 GVHD was not. These results indicate that HLA-haploidentical HSCT is a feasible transplant option for patients with CGD lacking HLA-matched donors. Further refinement of transplant protocols is necessary to mitigate graft failure and acute GVHD, ultimately improving access and outcomes for this life-saving therapy.

Multiple myeloma (MM) is a complex hematological malignancy characterized by genomic changes and transcriptomic dysregulation. Initial exome sequencing approaches have failed to identify any single frequent (>25%) mutation in the coding genome. However, using whole-genome sequencing (WGS), we found that one of the genomic regions most frequently mutated (62% of the MM patients) was the 5' untranslated (UTR) region and/or intron 1 of the BCL7A gene. RNA-seq data from a large cohort suggests a loss of BCL7A expression in a large majority of MM patients as compared to normal plasma cells. BCL7A loss of function in a panel of MM cell lines led to a highly proliferative phenotype in vitro and in vivo, while its ectopic expression significantly reduced cell viability, suggesting a tumor suppressor function for BCL7A in MM. We studied the cellular and molecular effects of BCL7A loss and observed that it endows myeloma cells with proliferative potential in cooperation with the plasma cell-defining transcription factor IRF4. BCL7A is involved in a direct protein-protein interaction with IRF4, limiting its DNA binding activity. Loss of BCL7A thus enhances the expression of IRF4-associated cytokines and reduces mitochondrial metabolism and ROS levels. Our study therefore suggests that BCL7A loss provides the necessary molecular change to allow IRF4-mediated transcriptional activity and MM cell growth and survival.