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In a real-world analysis of brexucabtagene autoleucel (brexu-cel) recipients with relapsed/refractory B-ALL (n = 278), lack of response to prior blinatumomab correlates with significantly worse post CAR-T outcomes.

Abstract: Acquired resistance to targeted, nonintensive therapies is common in myeloid malignancies. However, the kinetics of selection, the hematopoietic cell compartments in which selection occurs, and the molecular mechanisms underlying selection remain open questions. To address this, we studied the kinetics of clonal and transcriptional responses to combinational therapy with ivosidenib plus venetoclax, with or without azacitidine, across hematopoiesis in 8 patients with IDH1-mutant myeloid malignancy. All 8 patients initially responded to treatment, but 6 relapsed, whereas 2 remained in sustained remission for >4 years. We performed combined high-sensitivity single-cell genotyping and scRNA sequencing in index-sorted sequential patient samples. In all patients, clonal selection occurred rapidly, within 1 to 3 treatment cycles. Clonal selection preceded treatment failure by months to years. Relapse was associated with expansion of either clones harboring newly detected myeloid driver mutations or preexisting minor clones that underwent differentiation delay upon treatment exposure. In both cases, clonal selection occurred within immature cell populations previously shown to contain leukemic stem cell potential. Different genetic alterations within relapse-associated clones converged onto common upregulated transcriptional programs of stemness, branched-chain amino acid catabolism, and genes sensitive to menin inhibition. Importantly, this relapse-associated transcriptional signature was selected within 3 cycles of therapy. In contrast, in both patients remaining in remission, leukemic clones were rapidly eradicated, and replaced by clonal and wild-type hematopoiesis. Overall, in patients treated with ivosidenib combination therapy, rapid clonal selection occurs within the first treatment cycles. In those patients destined to relapse, genetically heterogeneous resistant clones are characterized by common transcriptional programs.

Abstract: We previously reported a chemogenomics screen that unexpectedly identified phosphatidylinositol-3-phosphate 5-kinase (PIKfyve) as a vulnerable target in multiple myeloma (MM). PIKfyve is an essential regulator of lysosomal function and autophagy. Given the high basal requirement for autophagy in MM for sustainable immunoglobulin synthesis, targeting autophagy holds clinical potential as a novel therapeutic avenue. Here, we report the development and characterization of PIK001 and analogs, potent and selective novel small-molecule inhibitors of PIKfyve. PIK001 demonstrated potent anti-MM activity in vitro, as well as synergistic activity with established anti-MM agents (including venetoclax and selinexor), while retaining efficacy in lenalidomide-resistant models. Multiomic characterization of isogenic cell lines sensitive and resistant to PIK001 identified a catalytic domain mutation (PIKFYVE N1939K) and heterogenous alterations in autophagy capabilities. Importantly, we noted that PIK001 exposure also resulted in significantly increased cholesterol metabolism and upregulation of major histocompatibility complex (MHC) class I expression, with potential implications in tumor immunity. Beyond MM, PIKfyve inhibition also shows selective cytotoxicity in acute myeloid leukemia, melanoma, and renal cancer, highlighting broader therapeutic potential. These findings establish PIKfyve inhibition as a valid target for MM and other hematologic malignancies, provide insights into mechanisms of sensitivity and resistance, and lay the foundation for further preclinical (particularly the role of cholesterol metabolism and tumor immunity) and clinical development.

NXT007 is a next-generation, activated factor VIII (FVIIIa)-mimetic bispecific antibody under investigation in the phase 1/2 NXTAGE trial (jRCT2080224835). Here, we report the primary analysis of the multiple-ascending-dose Part B in people with hemophilia A (PwHA). Eligible participants were men with severe HA without FVIII inhibitors. Four dose cohorts (B1-B4) were planned, with NXT007 administered subcutaneously at maintenance doses of 0.072 mg/kg, 0.28 mg/kg, 0.70 mg/kg, and 1.08 mg/kg, respectively, every 4 weeks. Primary endpoints were safety (adverse events [AEs] and serious AEs [SAEs]), tolerability, pharmacokinetics, pharmacodynamics, and efficacy; secondary endpoints included incidence of anti-NXT007 antibodies (ADAs). Participants in cohorts B1 (n=10), B2 (n=6), B3 (n=6), and B4 (n=8) had received NXT007 for a median (minimum-maximum) of 114.1 (29-140), 96.4 (88-112), 58.1 (52-72), and 22.2 (4-28) weeks, respectively. Two participants discontinued treatment: NXT007-unrelated AE (n=1) and complete loss of NXT007 exposure due to ADAs (n=1). Participants' plasma NXT007 concentration showed a dose-dependent increase, and predicted FVIII-equivalent activity reached a non-hemophilic level (≥40 IU/dL) in B2 onwards. NXT007 had a favorable safety profile at all doses. Most AEs were mild/moderate and all three SAEs were considered unrelated to NXT007. Mean annualized treated bleed rates were 1.48 (B1), 0.28 (B2), 0.00 (B3), and 0.00 (B4). Pharmacokinetics-affecting NXT007 ADAs were observed in two participants, including the participant in B1 who discontinued. NXTAGE Part B demonstrates that NXT007 could provide non-hemophilic coagulation activity in PwHA, with a less burdensome dose regimen than currently available therapies.

VCAR33, a donor-derived CD33-directed chimeric antigen receptor (CAR) T cell product, was developed to decrease relapse of high-risk acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) after allogeneic hematopoietic cell transplantation (alloHCT). We describe pre-clinical characterization of the VCAR33 construct, which was optimized for long-term anti-tumor surveillance based on killing and persistence assays. Prior to its use in post-alloHCT maintenance, we evaluated safety and efficacy of VCAR33 in a phase 1/2 clinical study for adults with relapsed or measurable residual disease (MRD)-positive CD33+ AML/MDS after alloHCT. Fifteen patients received VCAR33 across 2 arms stratified by disease burden: 7 patients in Arm A (bone marrow blasts ≥ 5%) at dose level 1 (DL1; 1 x 106 CAR+ T cells/kg) and 8 patients in Arm B (bone marrow blasts < 5%) at DL1 (n=5) and DL2 (3 x 106 CAR+ T cells/kg; n=3). The study ended for non-safety reasons before escalation to DL3 (1 x 107 CAR+ T cells/kg) and maximum tolerated dose was not determined. The most common treatment-related adverse event was cytokine release syndrome (93.3%; all < grade 3). Four patients (26.7%) experienced immune cell-associated neurotoxicity syndrome (1 ≥ grade 3) and 1 patient (6.7%) had grade III acute graft-versus-host disease within 28 days of VCAR33 infusion. Fourteen patients (93.3%) had transient VCAR33 expansion. Overall response rate was 20%: 2 patients had complete remission with incomplete count recovery in Arm A and 1 Arm B patient achieved MRD clearance. This allogeneic CAR T product demonstrated acceptable safety and preliminary anti-leukemic activity. ClinicalTrials.gov: NCT05984199.

Immune thrombocytopenia (ITP) is associated with a variable and unpredictable clinical course in children, including a spectrum of bleeding and systemic symptoms in the months following diagnosis. Although many children will have spontaneous resolution of disease prior to 1 year, up to 30% will go on to develop chronic disease. Known predictors for developing chronic ITP are limited, making clinical management and guidance during this early course of disease very challenging. Additionally, the pathophysiology of immune dysregulation in ITP is complex, with multiple variables likely contributing to the development of chronic disease. We aimed to create a statistical model to predict development of chronic ITP. Utilizing a retrospective training cohort of 611 children with ITP from two institutions and two validation cohorts comprised of 161 children, we developed and validated a multivariable logistic regression model and found that age, sex, IgG, IgA, IgM, presenting platelet count, presenting lymphocyte count, known secondary cause at diagnosis, and DAT positivity were useful in predicting chronic ITP. The external validations demonstrated consistent discriminative performance and clinical utility. The model is available for use at https://opal.shinyapps.io/citp-rm/. A chronicity prediction tool to use at the time of ITP diagnosis will better equip hematologists to counsel patients and families and engage in appropriate treatment strategies for individual patients earlier in their course.