Host-versus-graft reaction (HvGR) is a major challenge in allogeneic chimeric antigen receptor (CAR) T cell therapy. To counter host natural killer (NK) cell attacks, we armored allogeneic, human leukocyte antigen (HLA)-I deficient, B-cell maturation antigen (BCMA)-targeting CAR T cells with an NKG2A CAR. In vitro and animal studies demonstrated that allogeneic CAR-NKG2A T cells effectively resisted host NK cell-mediated killing. BCMA and NKG2A dual-targeting allogeneic CAR T cells (CT0590) resisted killing by NK cells and showed robust antitumor activity in preclinical in vivo models. On the basis of these data, a first-in-human study (NCT05066022) enrolled five patients (four with relapsed and refractory multiple myeloma [RRMM] and one with primary plasma cell leukemia [pPCL]). CT0590 was well-tolerated and caused no dose-limiting toxicities, treatment-related death, or graft-versus-host disease. Three patients achieved confirmed responses, including two with stringent complete response (sCR). Notably, sCR in the patient with RRMM was still ongoing (duration of response > 23 months) at the time of data cutoff, and sCR in the patient with pPCL lasted for 20 months. Both patients showed robust expansion of universal CAR (uCAR) T cells (Cmax > 280,000 copies/µg gDNA) and higher baseline NKG2A expression on NK cells than nonresponders. These results suggest that CAR-NKG2A technology may overcome HvGR, especially in patients with elevated NKG2A expression on NK cells. Further studies of CT0590 in RRMM and pPCL are warranted.

NPM1-mutated acute myeloid leukemia (AML) is genetically well-defined, but clinical outcomes remain heterogeneous, suggesting that quantitative clonal features may refine current risk stratification. We analyzed 688 intensively treated NPM1-mutated AML integrating variant allele frequency (VAF), mutation order, and clonal architecture inferred by PyClone and ClonEvol. Co-mutations were present in 97% of patients (median = 3 per case), dominated by DNMT3A (49%), FLT3-ITD (46%), TET2 (22%), and IDH2 (20%). Prognostic modelling of NPM1 VAF identified an optimal cut-off of 31.44%, defining NPM1high and NPM1low groups. NPM1low correlated with splicing-related alterations and independently predicted inferior overall (HR = 1.46; p = 0.037) and relapse-free survival (HR = 1.40; p = 0.036). Gene-specific VAF analyses revealed divergent effects across partners, high DNMT3A, FLT3-OTHER, KRAS, and PTPN11 burdens were adverse, whereas high IDH2 VAF was protective. Combined models showed that patients with NPM1high and favorable co-mutation VAFs had the best outcomes, while dual unfavorable burdens conferred the poorest survival. Mutation ordering inferred from VAFs positioned NPM1 after epigenetic and splicing lesions but before signaling and transcription-factor mutations. Non-canonical orders, such as early FLT3-OTHER/TKD or WT1 prior to NPM1, significantly stratified outcomes. Clonal reconstruction revealed predominantly linear evolutionary trajectories (84.3%), with increased mutational burden and clonal diversity associating with inferior survival. Notably, intra-clonal co-localization of NPM1 with IDH1 or TET2 was associated with improved outcomes, whereas co-localization with WT1 predicted dismal prognosis. These results demonstrate that quantitative and structural dimensions of clonality refine the biological and prognostic landscape of NPM1-mutated AML beyond mutational status alone.

N7-methylguanosine (m7G), a prevalent modification in transfer RNAs (tRNAs), is primarily catalyzed by the methyltransferase METTL1. Although growing evidence supports a role for METTL1 in various tumors, its therapeutic potential and precise function in leukemia stem cell (LSC) homeostasis remain largely unexplored. Here, we identify METTL1 as a key regulator of LSC self-renewal and homing within bone marrow (BM) microenvironment through catalyzing m7G formation on a specific tRNA, tRNAPheGAA, thereby promoting leukemogenesis. Mechanistically, METTL1 loss significantly reduces m7G abundance and steady-state levels of tRNAPheGAA, leading to translation suppression and degradation of transcripts enriched with tRNAPheGAA-related codons, such as hematopoietic cell kinase (HCK). Decreased HCK expression disrupts CXCR4 signaling, impairing LSC self-renewal and BM homing. Therapeutically, we characterized a small-molecule METTL1 inhibitor (M1i; NSC137443), through high-throughput screening. Pharmacological inhibition of METTL1 demonstrated potent antitumor efficacy by reducing tRNA m7G levels and disrupting the tRNAPheGAA/HCK/CXCR4 cascade. Notably, targeting METTL1 significantly reduces LSC frequency, delays leukemogenesis, and prolongs survival in multiple acute myeloid leukemia models. Together, our findings establish a previously unrecognized role for METTL1 and its target tRNAPheGAA in LSC homeostasis and provide compelling proof-of-concept evidence that METTL1 is a druggable epitranscriptomic target for antileukemia therapy.

Drug resistance is a major challenge in cancer therapy, especially in hematologic malignancies in which kinase inhibitors have transformed treatment yet are frequently undermined by drug resistance. Although targeted protein degradation (TPD) offers a mechanistically distinct mode of action compared with inhibition-based therapeutic therapies, the potential value of TPD in drug-resistant blood cancer remains unclear. Here, we report the discovery of cereblon (CRBN)-recruiting molecular glue degraders (MGDs) targeting lymphocyte-specific tyrosine kinase (LCK), an oncogenic kinase in T-cell acute lymphoblastic leukemia (T-ALL). By high-throughput screening and medicinal chemistry optimization, we developed a series of MGDs that induced CRBN-dependent degradation of LCK as well as potent cytotoxicity in T-ALL in vitro. Structure-activity relationship analysis and ternary complex modeling revealed a noncanonical degron at the LCK-CRBN interface involving the G-loop, whose mutation disrupts this interaction. Unlike inhibitors and inhibitor-based proteolysis-targeting chimeras, these MGDs engage LCK in regions distal to the ATP-binding site, and thus their activities in T-ALL are not affected by gatekeeper LCK mutations that drive resistance to inhibitor-based therapeutics. Taken together, our data highlight the potential of LCK-targeting MGDs as a strategy to overcome kinase inhibitor resistance in T-ALL, offering a framework for targeting kinase dependencies in drug-refractory hematologic malignancies more broadly.

Chimeric antigen receptor (CAR) T cells specific for myeloid-associated antigens expressed on the cell surface of acute myeloid leukemia (AML) can cause depletion of normal myeloid progenitor cells. We developed a CAR specific for a human Leucocyte Histocompatibility Antigen (HLA)-A*02:01-restricted peptide of the myeloid-restricted cathepsin-G protein. Cathepsin-G-specific CAR (CG1.CAR) T cells were further engineered to increase their functional avidity. Specifically, we developed CG1.CAR-T cells co-expressing the lymphocyte-specific protein tyrosine kinase (LCK) and duplicated CD3ζ chain, which allows the functional recognition of the CG1 peptide as low as 0.025 mM. Optimized CG1.CAR T cells displayed antileukemia effects in vitro and in vivo in AML patient-derived-xenotransplant (PDX) mouse models and did not cause hematopoietic toxicity in colony assays and humanized mice. Mechanistically, LCK overexpression in CG1.CAR-T cells caused transcriptional modifications characterized by the overexpression of mitochondrial-encoded electron transport chain components that were correlated with increased mitochondrial mass and improved respiratory capacity. Based on these data, CG1.CAR-T cells hold clinical potential for the treatment of AML.

Multiple myeloma (MM), the second most prevalent hematologic malignancy, remains incurable, highlighting the need to identify molecular drivers of disease progression and new therapies. Using a CRISPR-Cas9 library screening approach in MM cells, we identified 22 essential transcription factors (TFs), including members of the interferon regulatory factor (IRF) family. Remarkably, in addition to the well-known IRF4, IRF2 emerged as a critical TF in MM. Cleavage under targets and release using nuclease (CUT&RUN) experiments demonstrated that IRF2 binds extensively to chromatin, both independently and in cooperation with IRF1 and IRF4. Although IRF2-unique regions were predominantly associated with active promoters, regions bound by IRF2/1/4 were biased toward introns. Functionally, IRF2 contributes to MM cell survival by suppressing necroptosis and promoting cell migration. Notably, IRF2-dependent transcriptional dysregulation was evident in precursor conditions such as monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM), suggesting a role in early disease evolution. In addition to its role as an early factor, IRF2 levels also seem to influence disease progression, as MMs with higher expression demonstrated worse progression-free survival (PFS) and overall survival (OS) in both univariate and multivariate analyses, even after adjusting for common MM genetic risk factors. In conclusion, IRF2 constitutes an underappreciated essential TF involved in the pathogenesis and clinical behavior of MM. Its inhibition leads to dysregulation of key signaling pathways in MM pathogenesis, highlighting its potential as a therapeutic target.