Journal of Hematology & Oncology

Chimeric antigen receptor T-cell (CAR-T) therapy targeting CD19 has transformed outcomes for children with relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL), yet the influence of molecular subtype on outcomes remains unclear. We evaluated the impact of cytogenetic and molecular signatures on complete response (CR), overall survival (OS), and leukemia-free survival (LFS) after CD19 CAR-T therapy in eighty-six pediatric patients with R/R B-ALL treated with tisagenlecleucel. CR was assessed 30 days after infusion. Cytogenetic data were available for 84 patients and molecular profiling for 62. Survival analyses included 72 patients who received CD19 CAR-T as the sole cellular therapy. Seventy-seven patients achieved CR (89.5%). Pre-infusion bone marrow blasts of [&ge;]20% were associated with lower CR rates (53.8% vs 95.9%, p<0.0001) and significantly reduced OS and LFS (both p<0.0001). Among molecular markers, RAS mutations correlated with inferior OS (p=0.0222) and LFS (0.0402). In multivariate analysis, bone marrow blasts >20% and RAS mutations independently predicted inferior OS. Post CAR-T, CD19 negative relapses showed almost twice higher prevalence of RAS mutations (66% vs 37.5%). These findings highlight RAS mutations as a key molecular predictor of outcome after CD19 CAR-T therapy and suggest emergence of unique risk stratification for patients receiving CD19-targeting therapy.

Children with acute lymphoblastic leukemia (ALL) are treated with multiagent chemotherapy that causes profound changes to the immune system. There are limited data on how disease and therapy impact antigen-specific immune memory, leading to inconsistent guidelines on best practices for revaccination of this population. Here, to inform vaccine guidance, we investigated whether immunity derived from routine childhood measles and varicella zoster virus (VZV) vaccines is maintained during and after therapy for childhood ALL. We report that antibodies against measles and VZV were significantly reduced in children with ALL (n=45) compared to healthy controls (n=13), particularly in older children in whom a longer time had passed since their most recent vaccine dose. However, the avidity of the measles and VZV-specific antibodies was indistinguishable between groups. Despite changes to the composition of the T cell compartment, both overall and antigen-specific T cell function were preserved in children with ALL. These data provide compelling evidence for revaccination of children following ALL treatment. Intact T cell responses suggest that post-treatment revaccination would be effective.

CAR-T immunotherapy has achieved remarkable efficacy in hematologic malignancies. However, the widespread clinical adoption of autologous CAR-T products remains constrained by high costs, lengthy manufacturing process, and limited accessibility. Universal or off the shelf CAR-T (UCAR-T) cells derived from healthy donors offer a promising alternative, enabling immediate treatment at a lower cost. However, the allogeneic nature of UCAR-T cells triggers immune rejection by the host immune system after infusion, thereby compromising their persistence and therapeutic efficacy. Current strategies to circumvent this rejection focus on disrupting HLA class I expression. Although this modification allows UCAR-T cells to successfully evade T cell mediated elimination, the loss of HLA class I molecules renders them vulnerable to attack by host natural killer (NK) cells. In contrast to previous approaches that attempt to retain certain non-classical HLA molecules (such as HLA-E or HLA-G) to inhibit NK cells, we directly focused on editing the ligands that mediate NK cell rejection. Through transcriptomic and in vitro validation analyses, we found that UL16 binding proteins (ULBP) 2/5/6 were substantially upregulated in UCAR-T cells compared with nontransduced donor T cells. Elevated ULBP expression effectively activates the NKG2D receptor on allogeneic NK cells and leads to killing of UCAR-T cells, thereby impairing UCAR-T function. To test whether abrogating this NK activating signal could improve UCAR-T persistence and antitumor efficacy, we generated ULBP knockout UCAR-T cells using CRISPR-Cas9 editing. Deletion of ULBP2/5/6 significantly reduced NK cell mediated killing in vitro without affecting CAR expression or T cell effector function. Compared with wild type UCAR-T cells, ULBP deficient UCAR-T cells exhibited enhanced tumor killing efficacy in the presence of NK cells. Collectively, our findings identify ULBP upregulation as one of the mechanisms underlying NK cell mediated rejection of HLA deficient UCAR-T cells. Targeted ablation of ULBP molecules provides a novel strategy to confer resistance to host NK cells, thereby improving the therapeutic potential of universal CAR T products.

Chimeric antigen receptor (CAR) T-cell therapy has transformed treatment for relapsed /refractory(r/r) lymphoid malignancies. Yet, these cellular immunotherapies are often associated with immune-related adverse events (irAEs), namely cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS), that pose significant risks to patient safety and limit broader clinical implementation of CAR T-cell therapies. In the current study, we used proteomics technology to establish circulating protein signatures that would predict severe CRS and ICANS in r/r lymphoma patients that subsequently received CAR T-cell therapy. Initial discovery was performed using plasma samples collected preceding CAR T-cell infusion from 39 r/r lymphoma patients at MD Anderson Cancer Center. A 5-marker and 8-marker protein panel was developed for predicting Grade [&ge;] 2 CRS and ICANS respectively, yielding respective AUCs of 0.85 [95% CI: 0.72-0.98] and 0.91 [95% CI: 0.81-1.00]. Independent testing of the CRS and ICANS panel was performed in a cohort of 59 r/r lymphoma patients from the Moffitt Cancer Center, with resultant AUCs of 0.76 [95% CI: 0.63-0.89] and 0.67 [95% CI: 0.51-0.84] for the CRS and ICANS panel, respectively. Patients were further classified into low-, intermediate-, and high-risk groups based on panel score tertiles. In the combined dataset (MDACC + Moffitt), compared to patients in the low-risk group (reference), patients in the intermediate- and high-risk groups were 3.15 [95% CI: 0.92-12.71] and 13.84 [95% CI: 4.21-56.26] more likely to have Grade [&ge;] 2 CRS, and 1.21 [95% CI: 0.36-4.23] and 8.59 [95% CI: 2.87-29.09] more likely to have Grade [&ge;]2 ICANS. The protein biomarker panels provide a means to risk stratify patients who are at high risk for developing severe CRS and ICANS, to inform on the need for prophylactic interventions and improve patient outcomes.

Post-treatment measurable residual disease (MRD) in acute myeloid leukemia (AML) patients is associated with adverse clinical outcomes. Validated molecular methods for AML MRD are preferable to flow cytometry assays but are not available for all patients. The limit of detection (LOD) of next-generation sequencing (NGS) assays for single nucleotide variants is restricted by technical error rates. Structural alterations are common genetic features of AML, but MRD approaches for detecting this class of variants have primarily relied on RNA. However, RNA has suboptimal stability, not all structural alterations are expressed as transcripts, and the impact of anti-leukemic therapy on transcription may make leukemic disease burden quantification inaccurate. In this study, we demonstrate a whole genome sequencing (WGS)-based approach to identify genomic DNA breakpoints of chromosomal rearrangements that allowed design of highly sensitive patient-personalized digital droplet PCR (ddPCR) MRD assays. Acute myeloid leukemia (AML) is an aggressive malignancy of the hematopoietic precursor cells that predominantly affects older individuals. Oncogenic transformation occurring through the acquisition of structural chromosomal aberrations is noted in 35% of AML cases, and can result in the formation of fusion proteins that confer proliferation and survival advantages (1). When compared to classical cytogenetics for the identification of structural variants at diagnosis, newer techniques such as optical genome mapping can identify clinically pertinent aberrations that may be cryptic or smaller than the resolution of conventional karyotyping and FISH (2). Similarly, short-read whole genome sequencing (WGS) has been shown to increase diagnostic yield and better refine risk stratification when compared to traditional cytogenetic testing in myeloid malignancies (3). Additionally, WGS can be utilized to identify genomic breakpoints of chromosomal rearrangements at a basepair (bp) resolution.

Abstract/SummaryImmune checkpoint blockade can produce long-lasting responses in patients with metastatic melanoma; notably, combined CTLA-4/PD-1 blockade has been associated with approximately 52% melanoma specific 10-year survival (1). Yet, nearly half of patients experience minimal clinical benefit, and intensified regimens come with substantial risk of severe immune-related toxicity. The precise determinants of immunotherapy response are incompletely defined, reflecting a complex interplay between tumor biology and host immunity. This is especially consequential for patients whose disease progresses on checkpoint blockade, for whom effective salvage options are limited. In a series of patients with NRAS-mutated melanoma refractory to checkpoint inhibitors, we found that intratumoral administration of talimogene laherparepvec (T-VEC) combined with MEK inhibitor binimetinib induced exceptional clinical responses by amplification of pre-existing T cell responses and induction of de novo tumor-reactive immunity.

Chronic myelomonocytic leukemia (CMML) is a clonal myelodysplastic/myeloproliferative neoplasm characterized by persistent monocytosis and heterogeneous risk of progression to acute leukemia. Mutations within the RAS/MAPK signaling pathway, particularly involving KRAS, are linked to a proliferative disease phenotype and adverse prognosis. We report the first Colombian CMML case harboring two concurrent activating KRAS mutations (p.G12S and p.G13D). Both variants were detected at variant allele frequencies of 17% and 21% in a female patient in her late 50s presenting with marked leukocytosis, anemia, and thrombocytopenia. The coexistence of these mutations suggests synergistic hyperactivation of the RAS/MAPK pathway, likely driving clinical aggressiveness and therapeutic resistance. This case delineates a rare molecular subgroup within CMML and highlights the critical role of comprehensive genomic profiling to improve prognostic accuracy and inform precision medicine approaches.

Immune effector cell-associated neurotoxicity syndrome (ICANS) is a common and life-threatening complication of chimeric antigen receptor (CAR) T-cell therapy, with early detection being critical for timely intervention and improved outcomes. Cytokines such as interleukin-6 (IL-6) are key mediators of the inflammatory cascade underlying ICANS pathogenesis, but prospective clinical evidence for their predictive value is limited. Here we quantify IL-6 levels in a prospective cohort of 40 CAR-T patients (270 serum samples), using a simple in-house microfluidic bead immunoassay. IL-6 levels measured by our assay were significantly associated with ICANS onset. Specifically, each [~]3.4-fold increase in IL-6 levels was linked to a 74% increase in the odds of developing ICANS the following day, independent of other clinical variables. Overall, we show the prognostic value of IL-6 for next-day ICANS, demonstrate the potential of frequent cytokine measurement to guide CAR-T patient management, and develop a simple experimental method to perform such monitoring.

Children with relapsed or refractory acute lymphoblastic leukemia (ALL) require more effective and less toxic therapies. We established a prospective, multicenter Drug Response Profiling (DRP) registry (NCT06550102) integrating functional testing into precision-guided treatment. DRP was performed for 340 patients from 17 European countries with a turn-around time of two-weeks. Image-based drug screening with over 135000 unique perturbations revealed a heterogeneous landscape of ex vivo responses to 88 drugs on average. Ranking drug responses across the patient cohort defined individual drug fingerprints, identifying "DRP twins" by similarity in sensitivity and resistance independent of genetic ALL subtypes. Of 239 high-risk patients with follow-up, DRP-informed interventions were reported for 63 patients (26%). Patients received combination therapies based on venetoclax, tyrosine kinase inhibitors, trametinib, bortezomib or selinexor, resulting in objective clinical responses in 43 cases (68%). Precision-guided treatments allowed bridging to cellular therapies in 42 patients among whom 28 (67%) were still alive with a median follow-up of 21 months after DRP (IQR: 14.7-26.6 months). Top responders to venetoclax, ranked within the first tertile of the cohort, had superior 1-year event-survival compared to venetoclax non-responders (0.57 [95% CI, 0.39-0.85] vs. 0.25 [95% CI, 0.11-0.58]). Collectively, these findings demonstrate the feasibility and clinical relevance of functional profiling within an international network. This scalable framework enables individualized therapy selection for enrolment in adaptive precision trials for high-risk pediatric ALL.

BackgroundImmune checkpoint inhibition has transformed cancer therapy; however, many patients fail to respond to single-agent blockade, and combination strategies are often limited by toxicity. Central nervous system tumors exploit multiple immunosuppressive pathways, including the CD200 and PD-1/PD-L1 axis to evade anti-tumor immunity and support tumor aggressiveness. MethodsWe investigated ARL200, a peptide ligand targeting the CD200 activation receptor (CD200AR) using in vitro immune assays, murine syngeneic tumor models, phosphoproteomics, and correlative studies from a first-in-human trial in recurrent glioblastoma. ResultsARL200 exposure activated DAP10/12-dependent signaling and downregulated multiple inhibitory immune checkpoint receptors, including CD200R1, PD-1, and CTLA-4, and checkpoint ligands, CD200 protein and PD-L1, through suppression of the JAK1/3-SHP-STAT-IKK/{beta}-NF{kappa}B pathway. Distinct ARL200 variant peptides elicited unique immune responses. In patients with recurrent glioblastoma, ARL200 treatment was associated with immune activation, reduced inhibitory checkpoint expression, and evidence of antigen-specific memory responses without treatment-related toxicity. ConclusionsTargeting CD200AR enables coordinated modulation of multiple immune checkpoints with a single agent, representing a next-generation immunotherapeutic strategy opening a new pathway for treating aggressive malignancies. Key PointsO_LIARL200 elicits an active immune response for the development of a potent and durable anti-tumor response C_LIO_LIARL200 abolishes the suppressive effects of multiple immune checkpoint blockades C_LIO_LIDifferent ARL200 sequences drive alternative immune responses. C_LI Importance of the StudyTumors exploit multiple immune checkpoint pathways to suppress antitumor immunity, particularly within the immunosuppressive microenvironment of the central nervous system. Current immune checkpoint inhibitors often require combination therapy to achieve clinical efficacy, frequently at the cost of increased toxicity. In this study, we demonstrate that targeting the CD200 activation receptor (CD200AR) with a peptide ligand provides a novel strategy to simultaneously downregulate multiple inhibitory immune checkpoints, including CD200R1, PD-1, PD-L1, and CTLA-4, through a shared intracellular signaling pathway. ARL200 engagement activates DAP10/12-dependent signaling while suppressing the JAK1/3-SHP-STAT-IKK/{beta}-NF{kappa}B axis, thereby overriding tumor-mediated immunosuppression. Importantly, this multi-checkpoint modulation is achieved with a single therapeutic agent and translates to immune activation and clinical responses in patients with recurrent glioblastoma, with minimal treatment-related toxicity. These findings establish CD200AR targeting as a next-generation immunotherapeutic approach with the potential to improve the safety and efficacy of immune-based therapies for aggressive CNS malignancies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/26345679v1_ufig1.gif" ALT="Figure 1"> View larger version (80K): org.highwire.dtl.DTLVardef@17a5010org.highwire.dtl.DTLVardef@11e67eborg.highwire.dtl.DTLVardef@1387c07org.highwire.dtl.DTLVardef@156d418_HPS_FORMAT_FIGEXP M_FIG C_FIG

Long-term follow-up of the CASSIOPEIA trial (NCT02541383) demonstrated superior progression-free survival (PFS) with daratumumab, both in combination with bortezomib, thalidomide, and dexamethasone during induction and consolidation, and during maintenance therapy, in transplant- eligible patients newly diagnosed with multiple myeloma (MM). However, outcomes among CASSIOPEIA patients remain heterogeneous across treatment groups. Measurable residual disease (MRD) is a strong indicator of the depth and duration of therapeutic response and is independently associated with both PFS and overall survival (OS), but it does not fully capture the biological diversity of MM. We performed a risk prediction analysis based on transcriptomic subgroups in CASSIOPEIA patients. A subset of 628 patients was characterized using RNA sequencing and consensus clustering identified five transcriptomic subtypes of MM. Long-term follow-up allowed the definition of three transcriptomic risk categories, with estimated 72-month PFS rates of 70%, 51%, and 27% for low, intermediate, and high-risk groups, respectively, among patients who received daratumumab in at least one treatment phase. In these patients, MRD negativity rates after consolidation and six months later were significantly higher in the low and high-risk groups compared with the intermediate-risk group. In the high-risk group, MRD status was not associated with PFS or OS. This suggests that, although daratumumab administered during both the induction/consolidation and maintenance phases improves the clinical outcomes of patients with activation of NSD2 or overexpressing members of the MAF family, highly aggressive minor clones may rapidly expand. These findings emphasize the need for novel therapeutic strategies in this high-risk population.

The phase 1b TICIMEL clinical trial evaluated the safety, tolerability, and anti-tumor activity of combining the immune checkpoint inhibitors (ICI), ipilimumab and nivolumab, with tumor necrosis factor (TNF) blockers, certolizumab or infliximab, to treat advanced melanoma patients. A higher proportion of responses was observed in patients receiving ICI and certolizumab, while patients treated with ICI and infliximab demonstrated superior tolerability. Moreover, CITE-Seq analyses of circulating CD8 T cells showed that ICI plus certolizumab promoted an IFN signature, whereas ICI plus infliximab reduced the induction of genes associated with T cell activation. In preclinical models, ICI and TNF blockade with certolizumab increased IFN-{gamma}+ CD8 T cells and reduced regulatory T cells in tumors. The IgG1 Fc fragment of infliximab was identified as counteracting the benefits of TNF blockade. These findings underscore the importance of selecting the optimal TNF blocker to combine with ICI to enhance therapy efficacy in melanoma patients. ClinicalTrials.gov identifiers: NCT03293784; NCT05867004.

Allogeneic hematopoietic cell transplantation is the only curative option for many patients with acute myeloid leukemia (AML). In the current study, we designed and implemented a personalized assay, called v96, incorporating up to 96 mutations in 30 AML patients undergoing transplantation. The assay was performed on DNA derived in cells from the bone marrow as well as in cell-free plasma. All 30 (100%) of patients harbored molecular evidence of residual leukemia during remission that was detectable by the v96 assay, while only 6 (20%) had evidence of disease as assessed by conventional clinical assays. Furthermore, cell-free DNA from plasma proved to be more sensitive than DNA from cells of the bone marrow for identifying residual leukemia. The median number of mutants was 352-fold higher in plasma taken prior to transplantation for patients who relapsed compared to those who did not relapse. At two months post-transplantation, 27 of the 30 patients still harbored detectable leukemia as assessed by the v96 assay. Twenty-two of these patients had a subsequent decrease in leukemic burden assessed by the v96 assay, usually only after immunosuppression was discontinued and supporting a graft-versus-leukemia effect. These results document the feasibility of using a relatively large panel of carefully chosen mutations and a highly specific assay as non-invasive markers of therapeutic response in AML patients, minimizing the need for multiple bone marrow biopsies. STATEMENT OF SIGNIFICANCEWe report a blood test that tracks up to 96 patient-specific mutations and applied it to patients with AML who had undergone bone marrow transplantation. Using this test to evaluate cell-free plasma DNA, we found evidence of residual leukemia cells both during remission (prior to transplantation) in all patients, and two months following transplantation in 90% of patients. This test can mitigate the need for invasive bone marrow biopsies to follow patients with leukemia. Moreover, the test appears to be more accurate than standard assays for detecting residual leukemia, and has the potential to guide the timing of transplantation and subsequent therapeutic measures, thereby laying the foundation for future prospective studies.

Anti-CD19 chimeric antigen receptor (CAR) T-cell therapy can induce durable remissions in patients with large B-cell lymphoma (LBCL), yet outcomes remain variable. Reliable pre-treatment predictors of durable response remain limited, leaving a critical gap in patient management. To address this, we profiled pre-treatment plasma cell-free RNA (cfRNA) from 91 LBCL patients treated with axicabtagene ciloleucel (axi-cel, Yescarta) across three independent cohorts. We first demonstrated that signatures of "lymph node-like" tumor microenvironments (TMEs), previously identified in tumor biopsies and shown to correlate with favorable outcomes, are specifically elevated in the pre-treatment plasma cfRNA of responders, but not in matched peripheral blood mononuclear cells (PBMCs). These observations indicate that cfRNA captures TME tissue-derived signals not reflected in circulating immune cells. Next, using unbiased approaches, we identified additional cfRNA signatures associated with one-year clinical outcomes that capture the underlying biological landscape of treatment response. Collectively, these findings support pre-treatment plasma cfRNA as a minimally invasive surrogate of TME state to prospectively inform durable CAR T-cell therapy outcomes and guide risk stratification and TME-modulating adjunct therapies.

The pivotal role of tumor infiltrating myeloid cells in lung cancer composition and response to therapy is universally recognized. Nevertheless, their main cradle being the bone marrow (BM), remains vastly understudied owing to the spatiotemporal complexity of hematopoiesis and its hard to access anatomical location. Therefore, the BM niche of lung cancer subjects remains understudied which is why we integrated transcriptional and translational single-cell profiling, ELISA and two-photon microscopy to characterize the medullary hematopoietic compartment in orthotopic lung cancer-bearing mice with validation in human non-small cell lung cancer (NSCLC) samples. In brief we found that lung cancer remotely alters the entire hematopoietic process resulting in higher levels of hematopoietic stem cells (HSCs), myeloid and lymphoid multipotent progenitors (MPPs) and downstream predominance of Granulocyte Monocyte Progenitors (GMP), early Granulocyte Progenitors (GP) and Common Monocyte Progenitors (cMoP) at the expense of mature neutrophils and B cells. Furthermore, a significant increase in the expression and secretion of S100A9 and Lipocalin-2 (LCN2), was characteristic across the entire hematopoietic trajectory in lung cancer-bearing mice and patients. In vivo inhibition of S100A9 with Tasquinimod reduced tumor growth, irrespective of its combination with immunotherapy. In addition, it altered the secretion profile of S100A9 but also LCN2 in the BM, suggesting that S100A9 serves as an upstream regulator of LCN2 and holds therapeutic premise to treat immunotherapy refractory lung cancer.

BackgroundChimeric antigen receptor (CAR)-T cells are therapeutic breakthroughs against advanced non-Hodgkin lymphomas and myelomas. On the other hand, no CAR-T cell product has been so far clinically approved for therapy of Hodgkin Lymphoma (HL), T cell lymphoma (TCL), or Epstein-Barr-Virus (EBV)-associated lymphoproliferative diseases (EBV-LPDs). CD30 (TNFRSF8) is commonly expressed on HL and on subsets of TCL and EBV-LPDs. CD30CAR-T cells generated via transduction with viral vectors have been tested in clinical trials, showing overall good responses against HL. CAR-T cells produced entirely with locus-specific gene editing methods are emerging as attractive next-generation engineered cell products for ease of multiple seamless cell modifications. MethodsUsing CRISPR/Cas9-mediated techniques, we optimized homology-directed repair templates (HDRTs) and performed all-in-one multiplex editing to knock-in (KI) CD30CAR within the TCR constant (TRAC) locus and to simultaneously knock-out (KO) PD-1 or/and {beta}2M. CD30CAR-T cells were tested in CD30+ cell models of HL, TCL, and EBV-LPDs. ResultsWe compared mouse versus human anti-CD30 scFv designs in HDRTs incorporating TRAC homology arms, FcIg spacer/detection domain, and CD28 / CD3{zeta} signaling domains. We obtained an average of 30% TRACKICD30CAR-T cells and efficient in vitro cytotoxicity with CD30+ cell targets. CARs incorporating the high-affinity humanized 5F11 scFv showed the highest CAR expression, and the editing templates were further modified to incorporate a truncated CD34 (tCD34) spacer/detection domain. 5F11-CD30CAR-tCD34-T cells showed high CAR-KI rates (approx. 50-80% 12-14 days after editing) and potency in vitro and in vivo. Subsequently, we tested all-in-one CAR KI with additional KOs by co-electroporation of guide RNAs (gRNAs) targeting the genes encoding PD-1 or /and {beta}2M to improve function and allow for improved cell persistence in allogeneic recipients, respectively. Compared with CD30CAR-T cells, CD30CAR-{beta}2MKO-T cells were similarly viable and functional and showed low risk of translocations. PD1KO enabled CD30CAR-T cells to produce higher levels of cytotoxic features upon exposure to targets. However, simultaneous {beta}2MKO and PD-1KO compromised the expansion capacity of CD30CAR-T cells and resulted in detectable translocations. ConclusionsNon-virally engineered 5F11-CD30CAR-T cells represent a novel cell therapy modality against CD30+ lymphomas. Multiplex editing remains to be optimized to avoid unwanted genomic alterations and chromosomal translocations.

PurposeTarlatamab is a DLL3-directed bispecific T-cell engager demonstrating clinically meaningful activity in relapsed small cell lung cancer (SCLC) in the phase II DeLLphi-301 trial. Determinants of tarlatamab sensitivity and resistance are incompletely understood, and thus we sought to identify genomic and transcriptional correlates of tarlatamab sensitivity using a clinical sequencing pipeline at a single comprehensive cancer center. Experimental DesignWe performed a retrospective, single-institution analysis of 12 patients with SCLC treated with tarlatamab. Whole-exome sequencing (WES) and exome-capture whole-transcriptome sequencing (WTS) were performed on 12 samples, and two matched samples after treatment with tarlatamab. Integrative analysis examined correlation between molecular features and clinical outcomes. ResultsThe overall response rate was 50%, which was consistent with outcomes reported in the DeLLphi-301 trial. Differences between SCLC driver alterations and tumor mutational burden were not significant between responders and non-responders, but homologous recombination deficiency scores were higher in responsive tumors. DLL3 expression was significantly greater in responders and demonstrated predictive discrimination for clinical response (AUC 0.83). Tumors responsive to tarlatamab were predominantly ASCL1-driven (SCLC-A) and demonstrated increased immune activation, such as enrichment of cytotoxic T-cell, NK-cell, and T cell transcriptional programs. Transcriptional subtype and a composite metric consisting of DLL3 expression and immune activity (DLI score) further discriminated between responders and non-responders (sensitivity 0.83, specificity 1). Paired post-treatment sample analysis identified loss of ASCL1 lineage and emergence of YAP1 expression and downregulation of DLL3, consistent with lineage plasticity as a mechanism of acquired resistance. ConclusionsSensitivity to tarlatamab is correlated with a combination of increased DLL3 expression, ASCL1-driven lineage, and an increased immune activation. Lineage state reprogramming and decrease in DLL3 expression accompany acquired resistance to tarlatamab. These findings highlight the utility of RNA based biomarkers which integrate target expression, lineage state, and immune context to guide tarlatamab therapy in SCLC. Prospective validation of the whole-transcriptome DLI score and transcriptional subtype will inform tarlatamab response prediction.

Somatic mutations in the RAS pathway are highly prevalent in B-Cell Acute Lymphoblastic Leukemia (B-ALL), yet their impact on the bone marrow immune microenvironment and response to immunotherapy remains poorly defined. In this study, we integrated bulk RNA-sequencing, single-cell RNA-sequencing (scRNA-seq), and spectral flow cytometry to characterize the immune landscape of RAS-mutant B-ALL. We identified pathogenic mutations in KRAS, NRAS, PTPN11, or BRAF in 42% of the cohort, predominantly as clonal events. Despite similar T-cell frequencies by flow cytometry, bulk transcriptomes from RAS-mutant samples showed suppression of immune-response and T-cell-activation pathways, and T cells from RAS-mutant patients exhibited impaired proliferation ex vivo. Single-cell analysis revealed higher CD8 dysfunction scores and enrichment of regulatory T cells (Tregs) in RAS-mutant bone marrow. These findings were validated by spectral flow cytometry and by CIBERSORTx deconvolution of bulk data. Trajectory analysis supported a higher CD4 to Treg differentiation in the RAS-mutant niche, and CellChat mapping identified contact-dependent and checkpoint interactions (including TIGIT-NECTIN2 and CTLA-4-CD86/ICOSL) enriched in RAS-mutant samples. Functionally, blinatumomab produced limited leukemic-cell killing ex vivo overall, but addition of CTLA-4 blockade (ipilimumab) selectively restored blinatumomab efficacy in RAS-mutant samples. Together, these results indicate that RAS-pathway activation associates with a Treg-enriched, immunosuppressive bone-marrow microenvironment and point to CTLA-4-targeted strategies to enhance T-cell-engager efficacy in this subgroup.

Carbohydrates are classically catabolized by fermentation or oxidation, a choice that impacts many cellular functions including proliferation. Proliferating cells including somatic stem and progenitor cells are thought to favor fermentation over oxidation, and most proliferating cells in vitro depend on lactate production. However, it has not been tested if fermentation and oxidation are the universal obligatory terminal fates for carbohydrates in vivo because the key enzymes, lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH), have not been simultaneously deleted in any cell type. Here we show that both fermentation and oxidation are dispensable for the survival and function of hematopoietic stem cells (HSC). Combined LDHA and LDHB deletion to ablate LDH did not impair HSC function, suggesting that HSCs and rapidly proliferating hematopoietic progenitors surprisingly do not require fermentation. Combined LDHA, LDHB, and PDH deletion abolished both glucose oxidation and fermentation, but did not impair HSC function. Glycolysis was preserved, suggesting the operation of an alternative endpoint. LDH/PDH-deficient HSCs terminated glycolysis through pyruvate export. Pyruvate export by HSCs and progenitors was a physiological response to changing nutrient levels. Quadruple deletion of LDHA/B, PDH, and the pyruvate transporter MCT1 impaired HSC function. This suggested that an essential role of glycolysis termination is not to produce acetyl-CoA or lactate but to remove pyruvate. Therefore, in contrast to classical theories and to in vitro metabolism, carbohydrate metabolism in vivo does not require oxidation or fermentation but can terminate directly in pyruvate export, and this alternative pathway is sufficient to support stem cell function.

Children diagnosed with cancer typically receive standardized treatment regimens. Despite highly protocolized care, children living in poverty experience a greater risk of cancer relapse and higher mortality compared to their more affluent peers.1,2 Acute lymphoblastic leukemia (ALL) is the most prevalent childhood cancer, and children with ALL exposed to poverty are more likely to experience early relapse.3 Using single-cell RNA sequencing to analyze leukemic blasts and their microenvironment at diagnosis we found that poverty-exposed patients with standard-risk B-ALL exhibit transcriptional signatures of steroid resistance at time of diagnosis. Additionally, we observe increased expression of inflammatory signatures in myeloid cells and reduced effector signatures in CD8+ T-cells in children with B-ALL living in poverty. Further investigation of the mechanisms underlying these associations may identify opportunities for risk-adapted therapeutic strategies to improve disease outcomes in pediatric ALL.