Patients with relapsed acute myeloid leukemia (AML), particularly following allogeneic stem cell transplant (alloHCT), have extremely limited therapeutic options. CD123 is an AML-associated antigen and represents an attractive target for immunotherapy. We report outcomes of a phase 1 trial evaluating CD123-targeting chimeric antigen receptor (CAR) T cells in patients with relapsed/refractory (r/r) AML or blastic plasmacytoid dendritic cell neoplasm (BPDCN). This was a single center, open-label, phase 1 dose escalation study enrolling patients with either CD123-positive r/r AML (Arm 1) or BPDCN (Arm 2). Patients received autologous or donor-derived allogeneic CD123 CAR T cells following lymphodepletion. The co-primary objectives were to examine safety and anti-tumor activity using an activity-constrained for toxicity design and to determine the recommended phase 2 dose. Secondary objectives included assessments of progression-free and overall survival. We enrolled 41 patients, of whom 21 patients (n = 19 on Arm 1 and n = 2 on Arm 2) received CD123 CAR T-cell infusion. The median age of treated AML patients was 45 years (range: 20–71); the two BPDCN patients were aged 24 and 75 years. Among AML patients, 17 (89

Background Pre-metastatic niches composed of mainly myeloid cells are recognized as critical for tumor metastasis. However, whether adaptive immune cells also play an important role in pre-metastatic niche formation remains to be explored.Methods CD4+ T cell accumulation in tumor-free lung tissues from mice bearing subcutaneous mouse tumors was detected by immunofluorescence/confocal microscopy. Tumor-conditioned media (TCM) from MB49-S1pr1high mouse bladder tumor cells or ID8 ovarian tumor cells were administered to tumor-free mice to induce pre-metastatic niche formation. We used mice lacking functional Signal Transducer and Activator of Transcription 3 (STAT3) in T cells and Il17a‒/‒ mice to investigate the roles of STAT3 and interleukin (IL)-17. In vivo time-course experiments were performed to assess whether CD4+ T cell clusters contribute to CD11b+ pre-metastatic clusters. CD4+ T cell migration and chemokine receptor expression assays were employed to identify tumor factors driving CD4+ T cell recruitment. A co-culture system with human MRC-5 lung fibroblasts, healthy donor-derived CD4+ T cells, myeloid cells, and TCM derived from human cancer cells was used to evaluate CD4+ T cell-driven fibroblast activation and IL-17A dependency for myeloid cell migration. Microscopic analyses were performed to confirm CD4+ T cell clusters in tumor-free lymph node tissues from patients with prostate cancer and postmortem lung and liver specimens from patients with ovarian cancer.Results We demonstrate that CD4+ T cells accumulate in tumor-free lungs and promote tumor metastasis in mouse models. CD4+ T-cell pre-metastatic niche formation requires STAT3, which regulates Th17 CD4+ T cells. TCM drives IL-6-dependent CCR4/CCR6 upregulation on naive CD4+ T cells. CD4+ T cell clusters contribute to myeloid cell accumulation, and ablating STAT3 in T cells abrogates both T cell and myeloid cluster formation. IL-17 inhibition reduces myeloid lung infiltration. In human co-cultures, CD4+ T cells amplify TCM-induced fibroblast pre-metastatic niche-like activation and myeloid recruitment in an IL-17A-dependent manner. CD4+ and IL-17+ or p-STAT3+ clusters were also detected in non-metastatic tissues from patients with several cancers.Conclusions CD4+ T cells form pre-metastatic niches through the STAT3-IL-17 axis, contributing to myeloid cell cluster formation, in part through amplifying fibroblast pre-metastatic niche-like activation. STAT3 and IL-17 in CD4+ T cells therefore are important for pre-metastatic niche formation and metastasis.

Transplant-related morbidity remains a major barrier to broader application of allogeneic hematopoietic cell transplantation (HCT) in older adults. The frequency and importance of physical disabilities early after HCT have not been well-characterized. We sought to characterize the incidence and prognostic impact of physical disability complicating HCT in patients ≥60 years of age. We retrospectively analyzed 699 consecutive patients ≥60 years who underwent HCT at our institution. Physical disability post-HCT was defined as one or more of the following: (1) mobility dependence (requiring a person to assist walking); (2) delirium with loss of instrumental activities of daily living; (3) fall; or (4) intensive care unit admission. Disability-free Survival (DiFS) failure events included any of these disability events or death. The median age was 66 years; 20% were age ≥70 years. Melphalan-based conditioning was used in 85%, and 77% had matched donors. By day 30, 38% developed mobility dependence, 25% experienced delirium, 15% required intensive care unit care, and 5% experienced a fall. Day 30 DiFS was 57.2%, with a disability event preceding every death by day 30. One-year NRM landmarked at day 30 was 31.6% for patients with prior disability, versus 9.8% without (P < .001). In multivariable analysis, disability was independently associated with increased landmark NRM (Hazard Ratio [HR] = 2.70, 95% confidence interval [CI]: 2:03 to 3.60) and worse landmark overall survival (HR = 1.86, CI: 1.49 to 2.33), independent of acute graft-versus-host disease by day 30. Disability frequently complicates HCT in older adults and independently predicts higher NRM risk. Day 30 DiFS is a novel endpoint to quantify HCT morbidity and a potential target for trials to circumvent HCT-related complications.

BACKGROUND:Survivors of hematopoietic cell transplantation (HCT) have an increased risk of skin cancer, yet adherence to recommended skin self-examination (SSE) and annual physician skin examinations is low. Scalable strategies to improve screening in this high-risk population are needed. PATIENTS AND METHODS:We conducted a randomized controlled trial of 720 adult survivors of HCT enrolled between October 30, 2020, and December 13, 2023. Participants received remotely delivered print materials and 12 educational text messages over 9 months (patient activation and education [PAE]). In the PAE plus physician activation group (PAE + Phys), providers also received educational materials and guidance on performing skin examinations. Primary outcomes were participant-reported SSE within the prior 2 months and physician skin examination within the prior 12 months, assessed at baseline and 12 months. Secondary outcomes included the number of body regions examined and skin cancer knowledge. RESULTS:Median age at enrollment was 61 years (range, 18-81), and the median time from HCT until enrollment was 3.1 years (range, 1.7-5.3). The proportion of participants reporting both physician skin examination and SSE increased in both groups, from 15.8% to 47.5% in the PAE group (odds ratio [OR], 4.98; 95% CI, 3.54-7.02) and from 18.0% to 52.1% in the PAE + Phys group (OR, 5.49; 95% CI, 4.03-7.50), with no significant between-group difference. SSE increased significantly in both groups, from 34.7% to 81.5% in the PAE group and from 31.5% to 79.0% in the PAE + Phys group, without no significant between-group difference. Physician skin examinations increased from 32.1% to 55.3% in the PAE group and from 33.2% to 64.8% in the PAE + Phys group, with a significantly greater increase in the PAE + Phys group (P=.01). The mean number of body regions examined more than doubled in both groups, and skin cancer knowledge and self-efficacy improved significantly. CONCLUSIONS:Remotely delivered interventions improved skin cancer screening among HCT survivors. Patient activation substantially increased SSE, whereas physician activation provided additional benefit for physician-performed skin examinations. These findings suggest that physician activation enhances clinician-performed screening and supports scalable survivorship care models for high-risk populations. CLINICALTRIALS:gov identifier: NCT04358276.

CD19-directed therapy remains the mainstay treatment for relapsed/refractory B-cell acute lymphoblastic leukemia (ALL). However, treatment patterns and outcomes following CD19-negative (CD19-) relapse remain poorly defined. We retrospectively analyzed 65 adult patients with ALL who developed CD19-relapse after CD19-directed therapy. TP53 mutations and BCR::ABL1-like ALL were each identified in 27.7% (n = 18) of patients. Forty-six patients (70.8%) received one CD19-targeted therapy, whereas 19 patients (29.2%) received ≥ 2 prior to CD19-relapse. Overall, 60 patients (92.3%) received blinatumomab, and 23 (35.4%) received CAR T-cell therapy. The median time from the initiation of the most recent CD19-targeted therapy to CD19-relapse was 155 days (range, 13-1946). The median follow-up of the entire cohort was 32.7 months (IQR, 15.1-90.3). The median event-free and overall survival (EFS and OS) was 3.1 months (95% CI, 2.5-4.5) and 9.9 months (95% CI, 6.8-24.7), respectively. In multivariate analysis, receipt of ≥ 2 CD19-directed therapies was associated with both inferior EFS and OS, HR 2.17 (95% CI, 1.10-4.29; p = 0.03) and HR 3.05 (95% CI, 1.40-6.62; p = 0.005). The complete remission rate following first salvage therapy was 47.5% and 72.1% any time following CD19-relapse. Sixteen (34.8%) of 46 patients evaluated had subsequent CD19 re-expression, 5 of whom subsequently received CD19-directed therapy, and all 5 patients responded. Patients with ALL who develop CD19-relapse after CD19-directed therapy have poor outcomes and limited therapeutic options. However, since this study lacked a comparator cohort of patients with CD19-positive relapse, the independent prognostic impact of CD19 negativity could not be determined.

Tyrosine kinase inhibitor (TKI) therapy has resulted in a significant reduction in chronic myeloid leukemia (CML)-related mortality. However, the impact of TKIs on the health status of long-term CML survivors remains unstudied. We examined the health status of 62 TKI-treated CML patients who did not receive blood or marrow transplantation (BMT) (CML_TKI; median follow-up: 12.5 y) compared with an unaffected population (303 non-CML controls), and CML patients treated with BMT but without TKI exposure (220 CML_BMT; median follow-up 19.4 y). Participants self-reported general health, functional status, activity limitations, and pre-frailty/frailty. Overall, 71.0% of CML_TKI participants had ≥1 adversely-affected domain vs. 42.6% of non-CML and 65.9% of CML_BMT participants. When compared with the non-CML controls, the CML_TKI cohort was more like to have poor general health (aOR = 4.43, 95%CI = 1.8-10.7), functional impairment (aOR=2.84, 95%CI = 1.4-6.0), and activity limitation (aOR=3.37, 95%CI = 1.7-6.7) and more likely to be frail/pre-frail (aOR=3.71, 95%CI = 1.7-8.1). The CML_TKI and CML_BMT cohorts were comparable with respect to poor general health (aOR = 0.95, 95%CI = 0.5-2.0), functional impairment (aOR = 1.59, 95%CI = 0.8-3.0), and pre-frailty/frailty (aOR = 1.92, 95%CI = 0.92-4.0), but the CML_TKI cohort was more likely to report activity limitation (aOR = 2.2, 95%CI = 1.1-4.5). These findings inform a need for long-term monitoring and development of risk mitigation strategies to improve the health status as a treatment goal in CML care.

9552 Background: Lifileucel (Amtagvi), an autologous tumor-infiltrating lymphocyte (TIL) therapy, was FDA approval for unresectable or metastatic melanoma after progression on systemic therapy based on clinical trial data. However, real-world data describing early outcomes with lifileucel remain limited. Methods: We retrospectively reviewed a prospectively maintained database of patients with unresectable/metastatic melanoma who progressed on immune checkpoint inhibitors (and BRAF ± MEK therapy if applicable) and received lifileucel per standard protocol at a single institution April 2024–January 2026. Eligible patients received an in-specification TIL product and had evaluable imaging ≥12 weeks post-infusion unless progression was detected sooner. Responses were assessed per RECIST v1.1. Endpoints included objective response rate (ORR), disease control rate (DCR), duration of response (DoR), progression-free survival (PFS), overall survival (OS), and grade ≥3 treatment-related adverse events (TRAEs), excluding lymphodepletion-related cytopenias. Time-to-event endpoints were estimated using Kaplan–Meier methods. Results: Of 38 patients who underwent surgical TIL harvest, 32 (84%) received lifileucel, including 5 via the Expanded Access Program due to out-of-specification product. Among 27 patients receiving in-specification lifileucel, 20 had evaluable imaging and were included in the analysis. Patients received a mean of 2.2 prior therapies, and 35% had acral lentiginous or mucosal melanoma. All patients had Stage IV disease, including liver (40%) and brain (30%) metastases. 55% received bridging therapy after surgery prior to infusion. Median follow-up was 5.7 months (range, 0.9–16.9). ORR was 30% (3 CR, 3 PR), and DCR was 45%. Among responders, 67% (4/6) have ongoing response and median DoR was not reached. Median PFS was 3.5 months (95% CI, 2.1–5.3) and median OS was 6.1 months, with 6- and 12-month OS rates of 51% and 44%, respectively. Non-cytopenic grade ≥3 TRAEs occurred in 55%. Conclusions: In this early real-world experience, lifileucel demonstrated encouraging antitumor activity with ongoing responses in heavily pretreated patients despite high-risk features such as elevated LDH and liver and brain metastases. Additional studies and longer follow-up are warranted to optimize patient selection and define durability of benefit and survival outcomes. Baseline patient characteristics and safety outcomes. Characteristic/Outcome Overall (N=20) Age, median (range), y 62 (38-80) Male sex, n (%) 12 (60) Acral lentiginous/mucosal subtype, n (%) 7 (35) BRAF V600E mutation, n (%) 4 (20) LDH level > ULN, No. (%) 5 (25) Liver Metastases, No (%) 8 (40) Brain Metastases, No (%) 6 (30) Prior systemic therapies, mean (range) 2.2 (1-5) Patients with grade ≥3 non-hematologic TRAEs, n (%) 11 (55)

Salvage chemoimmunotherapy followed by autologous stem cell transplantation (ASCT) remains a standard therapy for relapsed/refractory (r/r) diffuse large B-cell lymphoma (DLBCL) who relapse > 1 year after frontline treatment. We evaluated the safety and efficacy of polatuzumab vedotin (Pola) combined with R-ICE salvage chemotherapy, followed by post-ASCT Pola maintenance, aiming to improve complete response (CR) rates and enhance post-ASCT outcomes in r/r DLBCL. Notably, the study's accrual period predated the approvals of second-line CAR T cell therapies. Forty-one patients were enrolled and received PolaR-ICE. Adverse effects of the combination were consistent with those observed with Pola and R-ICE chemotherapy with no new toxicity signals observed and were most commonly hematologic and gastrointestinal. The overall response rate after salvage was 88% with a CR rate of 56%. Twenty-two patients (56%) went on to receive autologous stem cell transplant and 16 (39%) received Pola consolidation. At a median follow-up of 25 months (range: 18-21), the 2-year PFS of all patients treated with PolaR-ICE (n = 41) was 49.9% (95% CI: 31.7-65.7) and 2-year OS was 75.0% (95% CI: 58.5-85.8). Patients with relapse ≤ 12 months of initial therapy achieved a 2-year PFS of 36.4% (90% CI: 17.1-56.0) versus 80.0% (95% CI: 40.9-94.6) among patients with relapse ≥ 12 months. Our findings demonstrate that Pola-RICE is a safe and effective salvage regimen for r/r DLBCL, which can be considered for patients with late relapse or in areas where CAR T access may be limited. Trial Registration: ClinicalTrials.gov identifier: NCT04665765.

Tumor-infiltrating lymphocyte (TIL) therapy, which involves extracting, expanding, and reinfusing immune cells to target cancer cells, has shown promise in melanoma treatment, but requires optimization for broader efficacy. The success of TIL therapy depends on the recognition of tumor-associated antigens, but neoantigen-reactive T-cells are often rare and exhausted in less immunogenic malignancies. Isolating T cells enriched in neoantigen reactivity prior to in vitro expansion and reinfusion may improve the response rates. To this end, our proprietary Specific Neo-Antigen Peptides (SNAP™) technology platform improves the accuracy of neoantigen prediction and validation by combining advanced computational modelling and PepSeq, a high-throughput screen for the physical credentialing of putative neoantigens based on their affinity to bind patient-specific HLA class II proteins. This approach allows for the education and enrichment of TILs (SNAP-TILs) with personalized, predefined, highly immunogenic neoantigens prior to expansion. Using the SNAP platform, we consistently achieved, on average, a SNAP-TIL product comprising 96% CD3+ cells, with a mixture of 75% effector and 23% central memory cells. SNAP-TILs exhibited greater efficacy and selectivity in immune infiltration than TIL, which was expanded by the rapid expansion protocol alone using ex vivo models. SNAP-TIL was also reactive in highly and poorly immunogenic tumors, with 70% and 50% tumor growth inhibition in melanoma and pancreatic patient-derived xenograft models, respectively. This study demonstrates the novel benefit of our Personalized Neoantigen Pipeline approach, potentially providing a durable antitumor immune response for a larger proportion of cancer patients.

It remains unclear whether prior chimeric antigen receptor (CAR) T-cell therapy is associated with an increased risk of graft-versus-host disease (GVHD) or nonrelapse mortality (NRM) following allogeneic hematopoietic cell transplantation (HCT). We evaluated the incidence of NRM, acute GVHD, and chronic GVHD in patients who underwent HCT following CAR T-cell therapy compared with matched controls who did not receive CAR T-cell therapy prior to HCT. We conducted a retrospective propensity-score matched case (prior CAR T recipients)-control (no CAR T prior to HCT) study to describe the impact of prior CAR T treatment on HCT outcomes. Day-100 NRM in the case versus control groups were 6.2% versus 8.6% (P = .82). Day-100 CI of grades II to IV and III to IV acute GVHD in the case versus control groups were 43.1% versus 44.8% (P = .83) and 20.0% versus 12.1% (P = .099), respectively. The 1-year CI of any and moderate/severe chronic GVHD in the case versus control groups were 43.8% versus 42.3% (P = .87) and 28.1% versus 20.3% (P = .23), respectively. Overall and GVHD/relapse-free survival were not statistically significantly different after adjusting for DRI, P = .094 and P = .14, respectively. The cumulative incidence of relapse and disease-free survival were not statistically significantly different. Patients who had less than 3 months between CAR T and HCT had improved graft-versus-host disease/relapse-free survival (GRFS), 40% versus 24.4% at 1-year (P = .032), owing to reduced grade III to IV acute GVHD, 5% versus 26.7% at 100-d (P = .030). Prior CAR T-cell therapy was not associated with an increased risk of GVHD or NRM, suggesting that CAR T-cell therapy can be administered without adversely affecting subsequent HCT outcomes.

Abstract CML is defined by evolution from chronic phase (CP) to increased disease burden during blastic phase, but the cellular mechanisms that create these disease states and produce the transition between states is not understood. We previously used state-transition models to show that CML evolution is not encoded in single-cell transcriptional microstates but instead emerges only when gene expression is aggregated into population-level macrostates where distinct phenotypic disease states emerge. Here, we extend this framework to ask how antagonistic teams of genes and their regulatory network defined steady states give rise to these macrostates. Using weekly time-series single-cell RNA sequencing from both CP and blast crisis (BC) inducible CML mouse models, we assessed the origin of phenotypic disease macrostates in each cell type by identifying antagonistic teams of genes. We identified these teams for each cell type lineage by selecting the genes where their eigenvalue in the state-space construction and their observed expression change combine to indicate that the gene either strongly promoted (pro-CML) or strongly opposed (anti-CML) leukemia. To coarse grain the large number of resulting of genes per lineage, we applied weighted gene coexpression network analysis (WGCNA) to define gene modules and module eigengenes that define coordinated transcriptional programs. Each module produced by this process were strongly enriched for either pro- or anti-CML which suggests that they define functional units in leukemia development. We then inferred gene regulatory networks for these modules using Bayesian network inference constrained by prior knowledge from curated interaction and regulatory databases. This produced module-level networks that were unique for each of the B, T, myeloid, and stem cell compartments. For each inferred network, we computed steady states (attractors) and projected the stable transcriptional configurations into the state-space to determine whether the gene derived attractors align with lineage-specific macrostates in the state-space. Preliminary analyses reveal that module networks can reproduce the early, transitional, and late CML macrostates observed from our previous study. Further, we performed in silico perturbations of the networks to predict shifts in attractor occupancy and recapitulate our previous findings that the dominant contributions of B and myeloid compartments to disease progression observed previously. These results support a mechanistic view of leukemia where CML macrostates arise from cell type-specific teams of genes organized into low-dimensional regulatory networks. These network level attractor states could provide a new approach to identify therapeutic targets that are directly related to disease phenotypes and, therefore, new approaches for preventing CML disease evolution. Citation Format: David Eugene Frankhouser, Anupam Dey, Jennifer Rangel Ambriz, Ziang Chen, Denis O'Meally, Yu-Hsuan Fu, Jihyun Irizarry, Tiffany Kanesa Ybarra, Ryan Sathianathen, Jeffrey Trent, Stephen J. Forman, Kathleen M. Sakamoto, Ya-Huei Kuo, Bin Zhang, Adam L. MacLean, Guido Marcucci, Russell Rockne. State-transition model of time-series single-cell RNA-seq identifies gene-level origins of disease microstate stability in chronic myeloid leukemia (CML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6830.

Systematic whole-protein screening and comprehensive profiling of antigen-specific CD4+ T cells are crucial for advancing vaccine design and cancer immunotherapies, yet remain technically challenging. Here, we present a high-throughput platform that utilizes large-scale class II single-chain trimer libraries to detect antigen-specific CD4+ T cells, while simultaneously profiling their antigen specificity, TCRα/β sequences, MHC restriction, whole transcriptomes, and patient/timepoint origins at single-cell resolution. Upon rigorous platform validation, we screened the full SARS-CoV-2 spike receptor binding domain in a longitudinal cohort of 22 participants, identifying 2,188 antigen-specific CD4+ T cells and showing key metrics defining the immunogenicity of class II-restricted viral antigens. We further extended the platform to whole-protein screening of HPV-16 E6/E7 in a cohort of precancerous patients, indicating HPV-specific CD4 TCRs that, upon extensive characterization, demonstrate strong therapeutic potential. By integrating high-throughput antigen screening with high-dimensional, multi-modal cellular characterization, our approach provides detailed insight into CD4+ T cell immunity, potentially guiding vaccine design and next-generation TCR-based cancer immunotherapies.

Abstract Outcomes for high-grade pediatric brain tumors are poor,butthere is optimism that chimeric antigen receptor (CAR) T cell therapycan improve prognosis. We present results from the firsttwo cohorts of a phase I clinical trial of IL13BBζ-CAR T cellsinfused weekly into the cerebral ventricles for children and young adults with recurrent or refractory high-grade neuromalignancies. Results Among the 18 patients (ependymoma =5, DIPG/DMG =9, pHGG=4) treated on trial, patients in cohort 2 (n = 15) received systemic lymphodepletion prior to first infusion; cohort 1 (n = 3) patients did not. The trial met its primary objectives of establishing feasibility, safety, and tolerability. There was one dose-limiting toxicity (Gr3 hypoxia, cohort 2). Secondary objectives included CAR T cell distribution and persistence in CSF and peripheral blood, response rates by RAPNO criteria, and overall survival. Patients received a median of 8 (range: 2-19) infusions. Common adverse events included headache, fever, and fatigue. Patients receiving lymphodepletion also experienced cytopenias. Two patients met protocol criteria for radiographic response, and half experienced radiographic decreases consistent with an anti-tumor response. Median overall survival from diagnosis for patients receiving lymphodepletion was 187m for patients with ependymoma, 20.5m for patients with midline glioma, and 30m for other patients. Median overall survival was 36m from diagnosis for patients not receiving lymphodepletion. Importantly, patients who did not receive lymphodepletion developed anti-CAR humoral and cellular immune responses detectable in the CSF and peripheral blood, and patients receiving lymphodepletion had higher numbers of CAR+T cells detected in CSF over the course of therapy. Conclusions This study demonstrates the safety, tolerability, and biological activity of locoregionally-delivered IL13BBζ-CAR T cells for children and young adults with neuromalignancies. Moreover, we show anti-CAR immune responses in patients not receiving lymphodepletion, but not in patients receiving systemic lymphodepletion. ClinicalTrials.gov:NCT04510051.

Cluster of differrentiation 19 (CD19)-directed therapies have significantly improved outcomes in B-cell malignancies; however, relapse driven by antigen escape remains a major clinical challenge, underscoring the need for alternative therapeutic targets. The B-cell activating factor receptor (BAFF-R), a key regulator of B-cell survival, is highly expressed in mature B-cell neoplasms, but its relevance in B-lymphoblastic leukaemia (B-ALL) remains unclear. We assessed BAFF-R expression in diagnostic and relapsed fresh B-ALL samples using multi-parameter flow cytometry. BAFF-R was consistently expressed in most cases, albeit at lower levels than in mature B cells, and expression was retained in the majority of CD19-negative relapses following CD19-directed therapy. Notably, tumor protein p53 (TP53) alterations were significantly enriched in CD19-negative immune escape disease (68.8% vs. 21.7%; p = 0.0006; OR = 7.9), yet BAFF-R expression remained preserved in this high-risk group. These findings establish BAFF-R as a stable immunotherapeutic target in B-ALL, including in CD19-negative and TP53-altered relapsed disease, and underscore its relevance amid ongoing early-phase clinical trials of BAFF-R-directed chimeric antigen receptor (CAR) T-cell therapy.

BACKGROUND:Total marrow and lymphoid irradiation delivers augmented doses of radiation to the bone marrow and lymph nodes while maintaining low doses to vital organs. We aimed to assess the effectiveness of combining total marrow and lymphoid irradiation (2000 cGy to bone marrow and lymph nodes) with high-dose cyclophosphamide and etoposide as a conditioning regimen before allogeneic haematopoietic cell transplantation (HCT) in patients with relapsed or refractory acute leukaemia. METHODS:This single-centre, open-label, phase 2 trial with an initial six-patient safety lead-in, conducted in the USA, enrolled patients aged between 16 and 60 years with relapsed or refractory acute myeloid leukaemia or acute lymphoblastic leukaemia. Total marrow and lymphoid irradiation was given on days -9 to -5, etoposide 60 mg/kg on day -4, and cyclophosphamide 100 mg/kg on day -2. Bone marrow or peripheral blood stem cells from sibling or matched or one allele mismatched unrelated donors were infused on day 0. Graft versus host disease prophylaxis consisted of tacrolimus and sirolimus. The primary endpoint for the initial safety lead-in segment was toxicity and for the phase 2 study was 2-year progression-free survival. All patients who began treatment were included in the analysis. This trial is registered with ClinicalTrials.gov, NCT02094794, and is closed to accrual. FINDINGS:Between May 9, 2014, and Mar 5, 2024, 107 patients were enrolled and screened for eligibility. One did not meet eligibility criteria (uncontrolled cytomegalovirus). 106 received conditioning radiation and HCT per protocol. Median follow-up was 1·8 years (IQR 0·6-3·0) for all patients and 3·1 years (2·1-4·9) for patients who were alive at last contact. None of the six patients in the safety lead-in experienced unacceptable toxicity. 49 (46%) of 106 patients were female and 57 (54%) were male. 72 (68%) of patients were White and 22 (21%) were Asian or Pacific Islander. The 2-year estimate of progression-free survival in all patients was 34% (95% CI 25-43%). The most common grade 3-4 adverse events were cytopenias 96 (91%), metabolic disorders 83 (78%), oral mucositis 45 (42%), diarrhoea 25 (24%), nausea 21 (20%), and palmar-plantar erythrodysesthesia syndrome 11 (10%). One patient died of sinusoidal obstruction syndrome attributed to the conditioning regimen. INTERPRETATION:Adverse events were few, probably due to organ sparing by total marrow and lymphoid irradiation. Total marrow and lymphoid irradiation 2000 cGy could be safely delivered in combination with high-dose etoposide and cyclophosphamide. The regimen was associated with encouraging 2-year progression-free survival rates. FUNDING:National Institutes of Health and Accuray.

Abstract: Relapse after allogeneic hematopoietic cell transplantation (alloHCT) remains a challenge for patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), and salvage therapy in this setting is not standardized. Given the efficacy of hypomethylating agents and venetoclax (HMA-VEN) in the frontline and relapsed settings, we evaluated the use of this therapy for post-alloHCT relapse. Eighty-three patients with AML (n = 69) or MDS (n = 14) who relapsed after alloHCT were included in this retrospective analysis. The median time to relapse after alloHCT was 7.0 months. Most patients (55%) had prior VEN exposure, and 28% of these patients had previously experienced treatment failure with a VEN-based regimen. HMA-VEN treatment-emergent toxicities were predominantly neutropenia and thrombocytopenia; however, the 30-day mortality was only 3.6%. There were 3 deaths within 30 days because of infectious complications. HMA-VEN led to a complete response (CR) or CR with incomplete hematological recovery in 48% of the patients, with 58% of these patients achieving minimal residual disease negativity. In multivariable analysis, European LeukemiaNet 2024 genetic risk stratification was a predictor of survival outcome. Additionally, prior VEN failure was not a predictor of overall survival. In conclusion, HMA-VEN provides an efficacious and well-tolerated option for post-alloHCT AML or MDS relapse regardless of their prior therapy and may allow responders to undergo a second alloHCT with curative intent.