T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy with a poor prognosis and limited options for targeted therapies. Identifying new molecular targets to develop novel therapeutic strategies is the pressing immediate issue in T-ALL. Here, we observed high expression of WD repeat-containing protein 5 (WDR5) in T-ALL. With in vitro and in vivo models, we demonstrated the oncogenic role of WDR5 in T-ALL by activating cell cycle signaling through its new downstream effector, ATPase family AAA domain-containing 2 (ATAD2). Moreover, the function of a zinc finger transcription factor of the Kruppel family (IKAROS) is often impaired by genetic alteration and casein kinase II (CK2) which is overexpressed in T-ALL. We found that IKAROS directly regulates WDR5 transcription; CK2 inhibitor, CX-4945, strongly suppresses WDR5 expression by restoring IKAROS function. Last, combining CX-4945 with WDR5 inhibitor demonstrates synergistic efficacy in the patient-derived xenograft mouse models. In conclusion, our results demonstrated that WDR5/ATAD2 is a new oncogenic signaling pathway in T-ALL, and simultaneous targeting of WRD5 and CK2/IKAROS has synergistic antileukemic efficacy and represents a promising potential strategy for T-ALL therapy.

BMT CTN (Blood and Marrow Transplant Clinical Trials Network) 1506 ("MORPHO") was a randomized study of gilteritinib compared with placebo as maintenance therapy after hematopoietic cell transplantation (HCT) for patients with FLT3-ITD-mutated acute myeloid leukemia (AML). A key secondary end point was to determine the impact on survival of before and/or after HCT measurable residual disease (MRD), as determined using a highly sensitive assay for FLT3-ITD mutations. Generally, gilteritinib maintenance therapy was associated with improved relapse-free survival (RFS) for participants with detectable peri-HCT MRD, whereas no benefit was evident for those lacking detectable MRD. We conducted a post hoc analysis of the data and found that the level of MRD detected with this approach correlated remarkably with RFS and relapse risk, and that MRD detectable at any level negatively affected RFS. In the placebo arm, 42.2% of participants with detectable FLT3-ITD MRD relapsed compared with 13.4% of those without detectable MRD. We found that 14.8% of participants had multiple FLT3-ITD clones detected as MRD and had worse survival irrespective of treatment arm. Finally, we examined the kinetics of FLT3-ITD clonal relapse or eradication and found that participants on the placebo arm with detectable MRD relapsed rapidly after HCT, often within a few weeks. MRD-positive participants on the gilteritinib arm relapsed either with FLT3 wild-type clones (assessed by capillary electrophoresis), after cessation of gilteritinib with persistent MRD, or on progression of multiclonal disease. These data demonstrate the potential of FLT3-ITD MRD to guide therapy with gilteritinib for this subtype of AML. This trial was registered at www.clinicaltrials.gov as #NCT02997202.

The maintenance of cellular redox balance is crucial for cell survival and homeostasis and is disrupted with aging. Selenoproteins, comprising essential antioxidant enzymes, raise intriguing questions about their involvement in hematopoietic aging and potential reversibility. Motivated by our observation of messenger RNA downregulation of key antioxidant selenoproteins in aged human hematopoietic stem cells (HSCs) and previous findings of increased lipid peroxidation in aged hematopoiesis, we used selenocysteine transfer RNA (tRNASec) gene (Trsp) knockout (KO) mouse model to simulate disrupted selenoprotein synthesis. This revealed insights into the protective roles of selenoproteins in preserving HSC stemness and B-lineage maturation, despite negligible effects on myeloid cells. Notably, Trsp KO exhibited B lymphocytopenia and reduced HSCs' self-renewal capacity, recapitulating certain aspects of aged phenotypes, along with the upregulation of aging-related genes in both HSCs and pre-B cells. Although Trsp KO activated an antioxidant response transcription factor NRF2, we delineated a lineage-dependent phenotype driven by lipid peroxidation, which was exacerbated with aging yet ameliorated by ferroptosis inhibitors such as vitamin E. Interestingly, the myeloid genes were ectopically expressed in pre-B cells of Trsp KO mice, and KO pro-B/pre-B cells displayed differentiation potential toward functional CD11b+ fraction in the transplant model, suggesting that disrupted selenoprotein synthesis induces the potential of B-to-myeloid switch. Given the similarities between the KO model and aged wild-type mice, including ferroptosis vulnerability, impaired HSC self-renewal and B-lineage maturation, and characteristic lineage switch, our findings underscore the critical role of selenoprotein-mediated redox regulation in maintaining balanced hematopoiesis and suggest the preventive potential of selenoproteins against aging-related alterations.

Philadelphia chromosome-like B-cell acute lymphoblastic leukemia (Ph-like ALL) is driven by genetic alterations that induce constitutive kinase signaling and is associated with chemoresistance and high relapse risk in children and adults. Preclinical studies in the most common CRLF2-rearranged/JAK pathway-activated Ph-like ALL subtype have revealed variable responses to JAK inhibitor-based therapies, suggesting incomplete oncogene addiction and highlighting a need to elucidate alternative biologic dependencies and therapeutic vulnerabilities, whereas the ABL-class Ph-like ALL subtype seems preferentially sensitive to SRC/ABL- or PDGFRB-targeting inhibitors. Which patients may be responsive vs resistant to tyrosine kinase inhibitor (TKI)-based precision medicine approaches remains a critical knowledge gap. Using bulk and single-cell multiomics analyses, we profiled residual cells from CRLF2-rearranged or ABL1-rearranged Ph-like ALL patient-derived xenograft models treated in vivo with targeted inhibitors to identify TKI-resistant subpopulations and potential mechanisms of therapeutic escape. We detected a specific MYC dependency in Ph-like ALL cells and defined a new leukemia cell subpopulation with senescence-associated stem cell-like features regulated by AP-1 transcription factors. This dormant ALL subpopulation was effectively eradicated by dual pharmacologic inhibition of BCL-2 and JAK/STAT or SRC/ABL pathways, a clinically relevant therapeutic strategy. Single cell-derived molecular signatures of this senescence and stem/progenitor-like subpopulation further predicted poor clinical outcomes associated with other high-risk genetic subtypes of childhood B-ALL and thus may have broader prognostic applicability beyond Ph-like ALL.

Monoclonal antibodies (mAbs) improve survival of patients with mature B-cell malignancies. Fcγ receptor-dependent effector mechanisms kill tumor cells but can promote antigen loss through trogocytosis, contributing to treatment failures. Cell-bound mAbs trigger the complement cascade to deposit C3 activation fragments and lyse cells. Within 24 hours after ofatumumab administration to patients with chronic lymphocytic leukemia (CLL), circulating tumor cells had lost CD20 and were opsonized with C3d, the terminal covalently bound form of complement protein C3. We hypothesized that C3d provides a target to eliminate residual CD20- tumor cells. To test this hypothesis, we generated C8xi, a mouse/human chimeric immunoglobulin G1 (IgG1) that reacts with human but not mouse C3d. C8xi was effective in a patient-derived xenograft model against CD20-, C3d opsonized CLL cells from patients treated with ofatumumab. We also generated rabbit mAbs, 2 of which were chosen because they bound mouse and human C3d with low nanomolar affinity but were minimally cross-reactive with full-length C3. Anti-C3d rabbit/human chimeric IgG1 in combination with ofatumumab or rituximab prolonged survival of xenografted mice that model 3 different types of non-Hodgkin lymphoma (NHL). For example, in a diffuse large B-cell lymphoma model (SU-DHL-6), median survival with single-agent CD20 mAb was 114 days but was not reached for mAb combination treatment (P = .008). In another NHL model (SU-DHL-4), single-agent and combination mAb therapy eradicated lymphoma in most mice. In long-term survivors from both cohorts, there was no evidence of adverse effects. We propose that C3d mAbs combined with complement-fixing CD20 mAbs can overcome antigen-loss escape and increase efficacy of mAb-based therapy.

One of the most remarkable achievements of the TKI era has been the capacity to induce deep molecular remissions that are sustainable off therapy in chronic myeloid leukemia (CML) patients - treatment-free remission (TFR). TFR was first described in a handful of patients within 3-4 years of imatinib approval. In 2004 TFR was tested in a small French pilot study, followed soon after by the French STIM and Australasian TWISTER studies. These early trials demonstrated that TFR was achievable, but also showed that rapid relapse was equally likely. Perhaps the most critical observation was that relapsing patients could be rapidly and safely returned to deep molecular remission after restarting therapy, minimising the risk associated with TFR attempts. Consensus criteria for TFR eligibility were established soon after those studies were reported. Over the past decade TFR criteria have been broadened, key predictive markers of success identified, and overall safety of TFR in the wider clinical community confirmed. Despite this progress, TFR is still only achieved in a fraction of CML patients globally. Over the next decade the focus will be making TFR the mainstream pathway for as many patients as possible as well as scaling back the duration of therapy required. More potent, better targeted TKIs, and immune modulation will likely have a significant impact. Predictive assays should enable most patients who attempt TFR to do so with a high probability of success. Ultimately TFR should be seen as the first step on an ambitious pathway towards cure for CML patients.

High-dose methotrexate (MTX) results in high rates of acute kidney injury (AKI), neutropenia, and hepatotoxicity. Glucarpidase is a recombinant enzyme that cleaves MTX, but clinical data supporting its use are scarce. We examined the association between glucarpidase administration and outcomes in adults with MTX-AKI from 28 cancer centers across the United States using a sequential target trial emulation framework. The primary end point was kidney recovery at hospital discharge, defined as survival to discharge with serum creatinine <1.5-fold baseline and without dialysis dependence. Key secondary end points were time to kidney recovery, neutropenia, and transaminitis on day 7, and time to death. Using multivariable logistic and Cox regression models, we compared outcomes in patients who received glucarpidase within 4 days following MTX initiation with those in patients who did not. Among 708 patients with MTX-AKI, 209 (29.5%) received glucarpidase. Overall, 183 (25.8%) had a primary end point event. Glucarpidase receipt was associated with a 2.70-fold higher adjusted odds of kidney recovery (95% confidence interval [CI], 1.69-4.31) compared with no glucarpidase receipt. Patients treated with glucarpidase also had faster time to kidney recovery (adjusted hazard ratio [aHR], 1.88; 95% CI, 1.18-3.33) and lower risks of grade ≥2 neutropenia (adjusted odds ratio [aOR], 0.50; 95% CI, 0.28-0.91) and grade ≥2 transaminitis (aOR, 0.50; 95% CI, 0.28-0.91) on day 7. There was no difference in time to death (aHR, 0.76; 95% CI, 0.49-1.18). These data suggest glucarpidase may improve both renal and extrarenal outcomes in patients with MTX-AKI.

Starting with imatinib, tyrosine kinase inhibitors (TKIs) have turned chronic myeloid leukemia (CML) from a lethal blood cancer into a chronic condition. As patients with access to advanced CML care have an almost normal life expectancy, there is a perception that CML is a problem of the past, and one should direct research resources elsewhere. However, a closer look at the current CML landscape reveals a more nuanced picture. Most patients still require life-long TKI therapy to avoid recurrence of active CML. Chronic TKI toxicity and the high costs of the well-tolerated agents remain challenging. Progression to blast phase still occurs, particularly in socioeconomically disadvantaged parts of the world, where high-risk CML at diagnosis is common. Here, we review the prospects of further improving TKIs to achieve optimal suppression of BCR::ABL1 kinase activity, the potential of combining different classes of TKIs, and the current state of BCR::ABL1 degraders. We cover combination therapy approaches to address TKI resistance in the setting of residual leukemia and in advanced CML. Despite the unprecedented success of TKIs in CML, more work is needed to truly finish the job, and we hope to stimulate innovative research aiming to achieve this goal.