Over the last decade significant advances have been made by honing the diagnostic evaluation and the significance of molecular profiles in patients with nonadvanced and advanced systemic mastocytosis (AdvSM). This is reflected in the 2022 iterations of the World Health Organization edition 5 and International Consensus Criteria classifications. The impact of targeted KIT inhibitor therapies on patients treated within global trials has demonstrated significant improvements in the prognosis and overall survival for patients, leading to a change in the treatment paradigm. Patients with SM and an associated hematologic neoplasm (AHN) comprise up to 70% of those in the advanced SM category, posing varying challenges in diagnosis and clinical heterogeneity because of the occupation of the bone marrow niche by 2 hematologic neoplasms. We are constantly learning about the complex, heterogenous genotypic and phenotypic spectrum of these patients with a view to provide personalized treatment options, aiming to improve outcomes, quality of life, and ultimately a cure. This paper focuses on the management of patients with AdvSM with an AHN and is a personal perspective using some illustrative patient cases treated at our center, Guy's and St Thomas' Hospitals, London, UK center of excellence in mastocytosis.

Robust genetic characterization of pediatric acute myeloid leukemia (AML) has demonstrated that fusion oncogenes are highly prevalent drivers of AML leukemogenesis in young children. Identification of fusion oncogenes associated with adverse outcomes has facilitated risk stratification of patients, although successful development of precision medicine approaches for most fusion-driven AML subtypes have been historically challenging. This knowledge gap has been in part due to difficulties in targeting structural alterations involving transcription factors and in identification of a therapeutic window for selective inhibition of the oncofusion without deleterious effects upon essential wild-type proteins. Herein, we discuss the current molecular landscape and functional characterization of 3 of the most lethal childhood AML fusion-oncogene driven subtypes harboring KMT2A, NUP98, or CBFA2T3::GLIS2 rearrangements. We further review early-phase clinical trial data of novel targeted inhibitors and immunotherapies that have demonstrated initial success specifically for children with these poor-prognosis genetic subtypes of AML and provide appreciable optimism to improve clinical outcomes in the future.

Myelodysplastic syndromes/neoplasms (MDS) are a widely heterogenous group of myeloid malignancies characterized by morphological dysplasia, a defective hematopoiesis, and recurrent genetic abnormalities. The original International Prognostic Scoring System (IPSS) and revised IPSS have been used to risk-stratify patients with MDS to guide treatment strategies. In higher-risk MDS, the therapeutic approach is geared toward delaying leukemic transformation and prolonging survival. For more than a decade, the hypomethylating agents azacitidine and decitabine have been the standard of care and, when feasible, an allogeneic hematopoietic stem cell transplantation should be considered. However, the IPSS scoring systems solely rely on clinical, morphological, and cytogenetic features and do not account for somatic mutations present in >80% of cases. These genetic abnormalities have been shown to play a crucial role in prognostication, prompting the development of molecular IPSS, and the integration of genomic features into MDS classification systems in recent years. In this review, we delineate our approach to higher-risk MDS in the context of updated classifications and the latest prognostication tools. We use illustrative clinical cases to support our discussion and share insights from recent clinical trials, highlighting lessons learned.

Bruton tyrosine kinase inhibitors (BTKis) are an established standard of care in chronic lymphocytic leukemia. The covalent BTKis ibrutinib, acalabrutinib, and zanubrutinib bind to BTK C481 and are all susceptible to the C481S mutation. Noncovalent BTKi, including pirtobrutinib, overcome C481S resistance but are associated with multiple variant (non-C481) BTK mutations, including those associated with resistance to acalabrutinib and zanubrutinib (T474 codon and L528W mutations). We review the current knowledge on variant BTK mutations, discuss their clinical implications, and consider their impact on clinical trials.

Sclerosis is a highly morbid manifestation of chronic graft-versus-host disease (cGVHD), associated with distressing symptoms and significant long-term disability. A patient-reported outcome (PRO) measure for cGVHD-associated sclerosis is essential to advance therapeutic trials. We aimed to develop a PRO for adults with cGVHD-associated sclerosis and evaluate and refine its content validity. Adults aged ≥18 years with cGVHD-associated sclerosis participated in semistructured interviews to identify salient symptoms and functions. Sclerosis-relevant symptoms and functions from existing PROs were also used to prompt discussion of topics not spontaneously mentioned. Symptoms and functions (subcodes) of importance were clustered and mapped to overarching domains (codes) using inductive analysis, and candidate items were developed. Cognitive interviews were used to evaluate content validity of the items, response options, recall period, and respondent instructions. Thirty-six open-ended interviews, conducted to saturation, revealed the breadth of the patient experience with cGVHD-associated sclerosis including 5 overarching domains: (1) skin changes, (2) symptoms, (3) emotional and social functioning, (4) mobility restrictions, and (5) activity limitations. A pool of 54 items was tested and iteratively refined through cognitive debriefing interviews (n = 25). Phrasing changes were made to improve relevance and comprehension. One item was removed, and 2 items were added to address respondent feedback, resulting in 55 items. Results support the relevance, comprehensibility, and comprehensiveness of the provisional Lee Symptom Scale-Skin Sclerosis. Concept elicitation and cognitive interviewing have informed the development of the Lee Symptom Scale-Skin Sclerosis. Psychometric testing and determination of minimal clinically important differences are underway in an external cohort to validate the PROs.

The multicenter, phase 3 German-Speaking Myeloma Multicenter Group (GMMG) ReLApsE trial randomized patients with relapsed and/or refractory multiple myeloma (RRMM) equally to lenalidomide/dexamethasone (LEN/DEX; 25 mg days 1-21, DEX 40 mg weekly, in 4-week cycles) reinduction, salvage high-dose chemotherapy (sHDCT; melphalan 200 mg/m2), autologous stem cell transplantation (ASCT), and LEN maintenance (10 mg/d; transplant arm, n = 139) vs continuous LEN/DEX (control arm, n = 138). Ninety-four percent of patients had received frontline HDCT/ASCT. We report an updated analysis of survival end points with a median follow-up of 99 months. Median progression-free survival (PFS) was 20.5 and 19.3 months in the transplant and control arm, respectively (hazard ratio [HR], 0.98; P = .9). Median overall survival (OS) was 67.1 and 62.7 months, respectively, (HR 0.89; P = .44). Landmark analyses from sHDCT and the contemporaneous LEN/DEX cycle 5 were performed because of 29% dropout of patients before sHDCT/ASCT in the transplant arm but did not reveal significant differences in PFS/OS. Time to progression after frontline HDCT/ASCT was a prognostic factor but did not predict benefit from sHDCT/ASCT. The GMMG ReLApsE trial does not support use of sHDCT/ASCT in RRMM after frontline HDCT/ASCT. This trial was registered at www.clinicaltrialsregister.eu as #EudraCT2009-013856-61.

Anemia is a common consequence of myelofibrosis. The treatment of myelofibrosis-associated anemia is complicated by a multifactorial pathobiology and a lack of therapies that result in normalization of the bone marrow and complete restoration of its function. Established agents that are used to treat anemia in other bone marrow failure states, such as myelodysplastic syndromes and aplastic anemia, are used for the treatment of myelofibrosis-associated anemia. However, there has been rapid development of new anemia-directed therapies, some of which have garnered regulatory approval. In addition to adopting therapies from other disease states, better understating of the root causes of myelofibrosis-associated anemia has positioned the field to be on the cutting edge of new anemia treatments, spearheading the advancement of agents that work on the hepcidin pathway to improve red cell production.

Natural killer (NK) cells have proven to be safe and effective immunotherapies, associated with favorable treatment responses in chronic myeloid leukemia (CML). Augmenting NK-cell function with oncological drugs could improve NK-cell-based immunotherapies. Here, we used a high-throughput drug screen consisting of >500 small-molecule compounds, to systematically evaluate the effects of oncological drugs on primary NK cells against CML cells. We identified second mitochondrially derived activator of caspases (SMAC) mimetics as potent enhancers of NK-cell cytotoxicity in both cell lines and primary patient samples. In contrast, several drug classes, including glucocorticoids and tyrosine kinase inhibitors such as dasatinib, inhibited NK-cell cytotoxicity. Single-cell RNA sequencing revealed drug-induced transcriptomic changes in both NK and target CML cells. SMAC mimetics upregulated NF-κB target genes in NK cells, potentially contributing to their enhanced cytotoxicity. Inhibitory drugs dexamethasone, dasatinib, and sotrastaurin prevented NK-cell transition to an activated state and suppressed the expression of interferon gamma (IFN-γ) by NK cells, thus preventing IFN-γ-mediated target cell transcriptomic response. In conclusion, we discovered that SMAC mimetics sensitize cancer cells to NK-cell-mediated killing, with potential clinical applications especially in patients with advanced phase CML.

Allogeneic hematopoietic cell transplantation is a curative therapy limited by graft-versus-host disease (GVHD). In preclinical studies and early-phase clinical studies, enrichment of donor regulatory T cells (Tregs) appears to prevent GVHD and promote healthy immunity. We enrolled 44 patients in an open-label, single-center, phase 2 efficacy study investigating if a precision selected and highly purified Treg therapy manufactured from donor-mobilized peripheral blood improves 1-year GVHD-free relapse-free survival (GRFS) after myeloablative conditioning. We compared this study arm with a concomitant standard-of-care (SOC) cohort. All donor Treg products were successfully manufactured and administered without cryopreservation within 72 hours. Participants had a 1-year incidence of acute grade 3 to 4 GVHD of 7%, moderate to severe chronic GVHD of 11%, and nonrelapse mortality rate of 4.5%. The primary end point of significantly improved 1-year GRFS was achieved at 64% evaluated against a predicted incidence of 40% (P = .002) with a realized incidence of 36% in the SOC comparator. For those trial patients who developed grade 2 to 4 acute GVHD, 91% responded to front-line corticosteroid therapy, whereas 50% responded in the SOC comparator group. Trial participants had a reduced incidence and burden of GVHD and improved GRFS, compared with rates common to highly variable unmanipulated donor grafts and multiagent immune suppression. This trial was registered at www.clinicaltrials.gov as #NCT01660607.

Differentiation of antigen-activated B cells into proproliferative germinal center (GC) B cells depends on the activity of the transcription factors myelocytoma (MYC) and B-cell lymphoma 6 (BCL6), and the epigenetic writers disruptor of telomeric silencing 1-like (DOT1L) and enhancer of zeste homolog 2 (EZH2). GCB-like diffuse large B-cell lymphomas (GCB-DLBCLs) arise from GCB cells and closely resemble their cell of origin. Given the dependency of GCB cells on DOT1L and EZH2, we investigated the role of these epigenetic regulators in GCB-DLBCLs and observed that GCB-DLBCLs synergistically depend on the combined activity of DOT1L and EZH2. Mechanistically, inhibiting both enzymes led to enhanced derepression of polycomb repressive complex 2 target genes compared with EZH2 single treatment, along with the upregulation of BCL6 target genes and suppression of MYC target genes. The sum of all these alterations results in a "cell identity crisis," wherein GCB-DLBCLs lose their proproliferative GC identity and partially undergo plasma cell differentiation, a state associated with poor survival. In support of this model, combined epidrugging of DOT1L and EZH2 prohibited the outgrowth of human GCB-DLBCL xenografts in vivo. We conclude that the malignant behavior of GCB-DLBCLs strongly depends on DOT1L and EZH2 and that combined targeting of both epigenetic writers may provide an alternative differentiation-based treatment modality for GCB-DLBCL.

Patients with relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL) have poor outcomes (complete response [CR] rates with standard salvage therapy gemcitabine plus oxaliplatin [GemOx], ∼30%; median overall survival [OS], 10 to 13 months). Patients with refractory disease fare worse (CR rate with salvage therapy, 7%; median OS, 6 months). Epcoritamab, a CD3×CD20 bispecific antibody approved for R/R DLBCL after ≥2 therapy lines, has shown promising safety and efficacy in various combinations. We report results from the phase 1b/2 EPCORE NHL-2 trial evaluating epcoritamab plus GemOx in autologous stem cell transplant (ASCT)-ineligible R/R DLBCL. Patients received 48 mg subcutaneous epcoritamab after 2 step-up doses until progression or unacceptable toxicity; GemOx was given once every 2 weeks for 8 doses. The primary end point was overall response rate (ORR). As of 15 December 2023, 103 patients were enrolled (median follow-up, 13.2 months; median age, 72 years). Patients had challenging-to-treat disease: ≥2 prior therapy lines, 62%; prior chimeric antigen receptor T-cell therapy, 28%; primary refractory disease, 52%; refractory to last therapy, 70%. ORR and CR rate were 85% and 61%, respectively. Median duration of CR and OS were 23.6 and 21.6 months, respectively. Common treatment-emergent adverse events were cytopenias and cytokine release syndrome (CRS). CRS events had predictable timing, were primarily low grade (52% overall, 1% grade 3), and resolved without leading to discontinuation. Epcoritamab plus GemOx yielded deep, durable responses and favorable long-term outcomes in ASCT-ineligible R/R DLBCL. This trial was registered at www.clinicaltrials.gov as #NCT04663347.

Cullin-5 (Cul5) coordinates the assembly of cullin-RING-E3 ubiquitin ligase complexes that include the suppressors of cytokine signaling (SOCS)-box-containing proteins. The SOCS-box proteins function to recruit specific substrates to the complex for ubiquitination and degradation. In hematopoiesis, SOCS-box proteins are best known for regulating the actions of cytokines that utilize the JAK-STAT signaling pathway. However, the roles of most SOCS-box proteins have not been studied in physiological contexts and any actions for Cul5/SOCS complexes in signaling by several hematopoietic cytokines, including thrombopoietin (TPO) and interleukin-3 (IL-3), remain unknown. To define additional potential roles for Cul5/SOCS complexes, we generated mice lacking Cul5 in hematopoiesis; the absence of Cul5 is predicted to impair the SOCS-box-dependent actions of all proteins that contain this motif. Here, we show that Cul5-deficient mice develop excess megakaryopoiesis and thrombocytosis revealing a novel mechanism of negative regulation of megakaryocyte-committed stem cells, a distinct population within the hematopoietic stem cell pool that have been shown to rapidly, perhaps directly, generate megakaryocytes, and which are produced in excess in the absence of Cul5. Cul5-deficient megakaryopoiesis is distinctive in being largely independent of TPO/myeloproliferative leukemia protein and involves signaling via the β-common and/or β-IL-3 receptors, with evidence of deregulated responses to IL-3. This process is independent of the interferon-α/β receptor, previously implicated in inflammation-induced activation of stem-like megakaryocyte progenitor cells.

Inotuzumab ozogamicin (InO) is an antibody-calicheamicin conjugate with striking efficacy in B-cell acute lymphoblastic leukemia (B-ALL). However, there is wide interpatient variability in treatment response, and the genetic basis of this variation remains largely unknown. Using a genome-wide CRISPR screen, we discovered that the loss of DNA nucleotidylexotransferase (DNTT) is a primary driver of InO resistance. Mechanistically, the downregulation of DNTT attenuated InO-induced DNA damage response, cell cycle arrest, and mitochondrial apoptotic priming, thereby ultimately leading to leukemia resistance to InO. Ex vivo leukemia InO sensitivity was highly associated with DNTT expression in ALL blasts with substantial intraleukemia heterogeneity as revealed by single-cell RNA sequencing. Among patients with B-ALL enrolled in the Children's Oncology Group trial AALL1621, we observed consistent DNTT downregulation in residual blasts following InO treatment. The selection of DNTT-low blasts by InO therapy was also recapitulated in vivo using patient-derived xenograft models. Collectively, our data indicate that DNTT is a key regulator of calicheamicin response in leukemia and thus a potential biomarker for individualizing InO therapy in B-ALL.

Aging and chronic inflammation are associated with overabundant myeloid-primed multipotent progenitors (MPPs) among hematopoietic stem and progenitor cells (HSPCs). Although hematopoietic stem cell (HSC) differentiation bias has been considered a primary cause of myeloid bias, whether it is sufficient has not been quantitatively evaluated. Here, we analyzed bone marrow data from the IκB- (Nfkbia+/-Nfkbib-/-Nfkbie-/-) mouse model of inflammation with elevated NFκB activity, which reveals increased myeloid-biased MPPs. We interpreted these data with differential equation models of population dynamics to identify alterations of HSPC proliferation and differentiation rates. This analysis revealed that short-term HSC differentiation bias alone is likely insufficient to account for the increase in myeloid-biased MPPs. To explore additional mechanisms, we used single-cell RNA sequencing (scRNA-seq) measurements of IκB- and wild-type HSPCs to track the continuous differentiation trajectories from HSCs to erythrocyte/megakaryocyte, myeloid, and lymphoid primed progenitors. Fitting a partial differential equations model of population dynamics to these data revealed not only less lymphoid-fate specification among HSCs but also increased expansion of early myeloid-primed progenitors. Differentially expressed genes along the differentiation trajectories supported increased proliferation among these progenitors. These findings were conserved when wild-type HSPCs were transplanted into IκB- recipients, indicating that an inflamed bone marrow microenvironment is a sufficient driver. We then applied our analysis pipeline to scRNA-seq measurements of HSPCs isolated from aged mice and human patients with myeloid neoplasms. These analyses identified the same myeloid-primed progenitor expansion as in the IκB- models, suggesting that it is a common feature across different settings of myeloid bias.

Perturbations in intermediary metabolism contribute to the pathogenesis of acute myeloid leukemia (AML) and can produce therapeutically actionable dependencies. Here, we probed whether α-ketoglutarate (αKG) metabolism represents a specific vulnerability in AML. Using functional genomics, metabolomics, and mouse models, we identified the αKG dehydrogenase complex, which catalyzes the conversion of αKG to succinyl coenzyme A, as a molecular dependency across multiple models of adverse-risk AML. Inhibition of 2-oxoglutarate dehydrogenase (OGDH), the E1 subunit of the αKG dehydrogenase complex, impaired AML progression and drove differentiation. Mechanistically, hindrance of αKG flux through the tricarboxylic acid (TCA) cycle resulted in rapid exhaustion of aspartate pools and blockade of de novo nucleotide biosynthesis, whereas cellular bioenergetics was largely preserved. Additionally, increased αKG levels after OGDH inhibition affected the biosynthesis of other critical amino acids. Thus, this work has identified a previously undescribed, functional link between certain TCA cycle components and nucleotide biosynthesis enzymes across AML. This metabolic node may serve as a cancer-specific vulnerability, amenable to therapeutic targeting in AML and perhaps in other cancers with similar metabolic wiring.