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Abstract Pseudouridine (Ψ) is the most prevalent RNA modification in human cells. Although Ψ was among the first post-transcriptional modifications discovered (1951), its biological functions remain poorly understood. More recently, Ψ was incorporated into COVID-19 mRNA vaccine, where it enhances RNA stability and reduces innate immune sensing. However, the precise roles of RNA Ψ in cancer, including leukemia, are largely unknown. Here, we identify RNA Pseudouridine Synthase D4 (RPUSD4) as a novel vulnerability in acute myeloid leukemia (AML) via directly catalyzing mitochondrial RNA (mt-RNA) Ψ formation. We further provide proof-of-concept evidence that targeting RPUSD4 suppresses leukemogenesis and stimulates anti-leukemia immunity. To investigate whether RNA Ψ dysregulation is involved in leukemia, we first compared RNA Ψ levels between primitive CD34+ cells (LSC-enriched) and CD34- bulk cells from multiple primary AML specimens. CD34+ AML cells exhibited significantly elevated RNA Ψ levels. We also examined Ψ levels across various RNA types in AML cells, identifying that mt-RNA contained much higher Ψ levels than other RNA types. These findings imply that RNA Ψ, particularly mt-RNA Ψ, may play a role in LSC biology and leukemogenesis. Further unbiased CRISPR screening revealed RPUSD4 as the most critical Ψ synthase for LSC maintenance. Large-scale transcriptomic and patient data analyses showed that RPUSD4 is highly expressed in AML specimens (P = 3.5 × 10-9), particularly within LSCs (P = 1.4 × 10-18). RPUSD4 knockout (KO) significantly suppressed AML proliferation, reduced mitochondrial OxPhos, and decreased LSC frequency in vitro and substantially delayed AML progression in vivo (MLL-r and FLT3ITD models). Of note, RPUSD4 KO-mediated anti-leukemia effects could be fully rescued by wild-type but not catalytically inactive RPUSD4 both in vitro and in vivo, demonstrating that Ψ synthase activity is essential for its function in leukemia. To profile RPUSD4-dependent Ψ sites, we applied two orthogonal technologies, direct nanopore sequencing and PRAISE sequencing (PMID: 36997645), both capable of detecting Ψ at single-base resolution. These approaches converged on a single RPUSD4-dependent Ψ at position 3,067 on mt-16S rRNA. This Ψ site is essential for maintaining rRNA stability. RPUSD4 KO induced mt-16S rRNA decay, thereby suppressing mitochondrial translation. This led to OxPhos inhibition, growth suppression, and LSC eradication in AML. Mechanistically, RPUSD4 is exclusively localized in mitochondria, where it directly interacts with the mt-RNA exonuclease PNPase. Under physiological conditions, PNPase resides within mitochondria and degrades mt-RNA to prevent accumulation of mitochondrial double-stranded RNA (mt-dsRNA). Upon RPUSD4 depletion, PNPase translocates from mitochondria to the cytosol, resulting in two major consequences: (i) mRNA decay:Cytosolic PNPase degrades mRNAs, particularly the nuclear-encoded mitochondrial mRNAs, such as DHODH(Dihydroorotate dehydrogenase). By retrogradely upregulating DHODH, RPUSD4 promotes de novo pyrimidine synthesis in AML. (ii) Aberrant mt-dsRNA accumulation: The buildup and cytoplasmic release of mt-dsRNA activates “viral mimicry” response that sensitizes AML cells to T cell cytotoxicity. Finally, to therapeutically target RPUSD4, we developed an RNA-based inhibitor, CpG-siRNARPUSD4, by conjugating a specific RPUSD4 siRNA to a Toll-like receptor (TLR9) ligand. CpG-siRNARPUSD4 is specifically internalized by TLR9+ cells, including AML cells, thereby maximizing selectivity and minimizing toxicity. Preclinical studies demonstrate that pharmacologically targeting RPUSD4 significantly prolonged survival across multiple AML models, including patient-derived xenograft (PDX) models, and rendered AML cells more susceptible to T cell–mediated cytotoxicity. Furthermore, the RPUSD4 inhibitor exhibited a promising synergistic effect with DHODH inhibitor in treating relapsed AML in vivo. For instance, in a representative relapsed PDX model, median survival times (in days) were: Ctrl – 28, RPUSD4 inhibitor – 36, DHODH inhibitor – 39, and combination – over 60. In conclusion, our findings uncover a previously unrecognized role of RPUSD4 and mt-RNA Ψ in leukemic metabolism, anti-leukemia immunity, and LSC maintenance. This study also bridges a critical knowledge gap regarding the role of RNA Ψ in leukemogenesis.

Abstract Introduction: Brexucabtagene autoleucel (Brexu-cel) is a CD19-targeted chimeric antigen receptor (CAR-)T cell therapy approved for treatment of relapsed/refractory (r/r) B-ALL. Brexu-cel's approval was founded on data from the ZUMA-3 trial, in which 78 patients (pts) were treated at the pivotal dose of 1x10e6 CAR-T cells/kg, resulting in a complete remission (CR) rate of 73%. Three-year follow-up from ZUMA-3 demonstrated median relapse-free and overall survival (RFS/OS) of 11.6 and 25.6 months (mos) for all treated pts. Amongst responders, the median OS was 60.4 mos for those who did not receive a subsequent allogeneic hematopoietic cell transplant (HCT) (n=43), but only 36.3 months for those who did (n=14). This has led some to conclude that HCT may not be beneficial following brexu-cel therapy for r/r B-ALL; however, it must be noted that 29 (37%) of the pts treated on ZUMA-3 received brexu-cel for post-HCT relapse. T cells collected from individuals who relapse in the post-HCT setting are largely of donor origin, making the CAR-T product comparable to a genetically modified donor lymphocyte infusion (DLI). The immunology at play in this scenario may be different from that in which CAR-T cells are of truly autologous origin. Methods: The Real-World Outcomes Collaborative for CAR-T in ALL (ROCCA) consortium database includes pt characteristics and outcomes of brexu-cel therapy given as standard-of-care across 41 US institutions. We identified pts who achieved an MRD negative (neg) CR by either flow cytometry (minimum sensitivity 10e-4) or NGS following brexu-cel for r/r Ph neg B-ALL and categorized them into three groups with regard to use of HCT: Never HCT, Pre-CAR HCT, or Post-CAR HCT. Pts who received second HCT following brexu-cel for post-HCT relapse (n=9) were excluded. Pt/disease characteristics, RFS, and OS were assessed for each group, landmarked at 73 days after brexu-cel infusion (the median time to consolidative allogeneic HCT). Results: In the ROCCA database we identified 165 pts who achieved MRD neg CR following brexu-cel, amongst whom 69 never underwent HCT, 49 were transplanted pre-CAR (ie, brexu-cel served as a genetically modified DLI), and 47 underwent post-CAR consolidative HCT while in CR. The median follow-up is 373 days. The median age was higher in the Never HCT group (49, range 19-83) in comparison with the Pre-CAR HCT (40, 24-72) and Post-CAR HCT (34, 18-70) groups. Thirty-five percent were >60yo in the Never HCT group vs 20% in the Pre-CAR HCT and 9% in the Post-CAR HCT groups. Ph-like disease was present in 38%, 29%, and 43% of the Never HCT, Pre-CAR HCT, and Post-CAR HCT groups, respectively (p=0.35). No significant differences were observed in pre-apheresis bone marrow blasts, presence of CNS disease at apheresis, prior blinatumomab or inotuzumab treatment, or use of bridging therapy across the groups, though there was a higher prevalence of non-CNS extramedullary disease in the Pre- and Post-CAR HCT groups (32, 39%) vs the Never HCT group (13%) (p=0.004). A minority of pts in all groups were deemed to be in MRD neg CR prior to apheresis (6-20%). Median RFS was 260 days in the Never HCT group and not reached in the Pre- and Post-CAR HCT groups (p=0.002), with respective 1-yr RFS of 38%, 64%, and 67%. Median OS was not reached in any group and was similar for all at 1-yr at 68-79% (p=0.13). Characteristics of those in the Never HCT group who were least likely to relapse included age >60 (OR 0.22, CI 0.07-0.73 vs age 18-39, p=0.024) and those with non-Ph-like B-ALL (OR 0.33, CI 0.12-0.94, vs Ph-like, p=0.037) in univariate analyses. Conclusions: Real-world data regarding outcomes following brexu-cel therapy allow evaluation of the role for consolidative allogeneic HCT, which remains one of the most important unresolved questions in the use of CAR-T therapy for r/r B-ALL. This analysis demonstrates that a first consolidative HCT after achieving MRD neg CR with brexu-cel is associated with a significant decrease in relapse. Additionally, use of brexu-cel for post-HCT relapse is also associated with a significantly lower risk of relapse compared with those who never received an allogeneic HCT. With the current duration of followup, OS is not significantly different across the three groups. These data suggest there is a benefit for relapse-free survival in pts receiving an allogeneic HCT at some point in the course of treatment for r/r Ph neg B-ALL.

Abstract INTRODUCTION The ECHELON-2 trial for newly diagnosed CD30+ peripheral T-cell lymphomas (PTCL) demonstrated superior overall survival with brentuximab vedotin plus chemotherapy (BV-CHP) compared to CHOP. However, total enrollment was restricted to only 30% of patients with non-anaplastic large cell lymphoma (ALCL) histologies and was not powered to analyze survival benefits in this cohort. Thus, the benefit of BV-CHP in non-ALCL patients remains less clear. Adding to this uncertainty, CHOP plus etoposide (CHOEP) remains a standard regimen for many non-ALCL PTCL histologies for patients <60 years of age. Which of these three regimens offers superior outcomes for patients with CD30+ non-ALCL PTCL remains to be determined, is a critical knowledge gap in this area, and could meaningfully inform the management of these patients. METHODS We conducted a retrospective analysis of chemotherapy-naïve CD30+ (≥1%) PTCL from 7 centers in the United States. Histologies were limited to PTCL-NOS and PTCL with a T follicular helper phenotype (PTCL-TFH). Frontline regimens were defined as BV-based (BV-CHP), etoposide-based (CHOEP/EPOCH), novel-CHOP (CHOP/CHOEP + novel drug on a clinical trial), or CHOP. CD30 was considered positive if any expression was reported, and when available, stratified as ≥10% or <10% of the total lymphocyte population. RESULTS The CD30+ PTCL cohort consisted of 194 patients with a median age of 68 years at diagnosis and a male (65%) predominance. Nodal PTCL-TFH (65%) was the most common histology. Most had stage III-IV disease (89%) with a high-intermediate to high-risk IPI score of 3-5 (54%). 18% had an ECOG of ≥2, 45% had ≥2 extranodal sites, and 43% had bone marrow involvement, although biopsies were not performed in all patients. CD30 expression in ≥10% of malignant T cells was observed in 55% of all quantitatively reported cases. Frontline therapy consisted of BV-based (36%), etoposide-based (30%), CHOP (27%), and novel-CHOP (7%). Baseline characteristics and CD30 expression were similar between treatment groups. The ORR was 72% (64% CR, 8% PR), with no differences observed by treatment or histology. On multivariate analysis (MVA), a high LDH was associated with lower CR (OR 2.84, p=0.003). For the patients who demonstrated a CR to frontline therapy, 61% underwent ASCT. With a median follow-up of 26.1 months (IQR 12.3-51.6), the median PFS and OS were 11.4 (9.8-14.2) and 47 (32-60.3) months, respectively. The 2-year PFS and OS were 34.9% (28.1-41.7) and 62% (54.5-68.6), respectively. PFS and OS were similar for PTCL-NOS compared to PTCL-TFH, and AITL fared similarly to non-AITL PTCL-TFH. By treatment, novel-CHOP demonstrated the most favorable PFS (median 41.9 months) and OS (median 68.1 months). Survival curves overlapped continuously with all other treatment regimens and was not statistically significant. For patients <60, PFS and OS were equivocal with BV-based (n=17) compared to etoposide-based (n=26) regimens. On MVA, stage III/IV disease conferred an inferior PFS (HR 2.00, p=0.018) as did an IPI score of 3-5 for OS (HR 2.15, p=0.001). Neither histology nor frontline treatment impacted PFS or OS. The chosen frontline treatment also had no survival impact in key subgroup analyses including patients <60 (n=56) or with CD30-expression ≥10% (n=43). For patients with CR to frontline therapy, ASCT demonstrated a significant PFS benefit (HR 0.59, p=0.028) but no statistically significant difference in OS benefit (HR 0.58, p=0.073). CONCLUSION These data provide valuable insight into the lesser-represented patient population from the pivotal ECHELON-2 trial. In this cohort of CD30+ (≥1%) non-ALCL PTCL, there was no clearly superior standard frontline regimen. The number of patients with quantitively reported CD30 expression was too small for definitive conclusions in the ≥10% CD30+ cohort and retrospective pathology review is ongoing. ASCT for patients in CR offered superior outcomes, supporting this strategy regardless of the frontline regimen, recognizing the limitations of non-randomized, retrospective analyses. Novel-CHOP regimens demonstrated encouraging survival, and clinical trials should maintain priority over standard regimens for patients with CD30+ (1-10%) PTCL-NOS and PTCL-TFH.

Abstract Copy Number Alterations (CNAs), including chromosomal gains and losses, shape the genetics and clinical management of acute myeloid leukemia (AML), particularly in complex karyotypes (e.g. CK-AML). Traditionally, AML associated CNAs have been studied using cytogenetic approaches, i.e., karyotyping, that are limited in resolution and sensitivity. Here, low-coverage, sparse whole genome sequencing followed by machine learning applied to over 600 AML patient samples (ECOG-ARCIN trials: E1900, E3999) reveals novel genetic, biologic, and clinical correlates in AML disease. We find that multi-variate Cox-regression analysis applied to the data identifies select patients exhibiting focal and cryptic hemizygous deletions at 17q, 21q, and 3p, in otherwise diploid genomes, associate with inferior survival compared to other patients (median overall survival; OS = 65.5 compared to 421 days, Chi-square test pval=6x10-11), independent of factors such as age, treatment, and karyotype complexity status. In addition, we confirm that amplifications at 11q23, encoding the KM2TA gene, are associated with inferior outcome, and further identify unique breakpoint event features as well as transcriptional signatures suggestive of distinctive KM2TA-translocation independent biology. Applying machine learning approaches to the data, more specifically Non-negative Matrix Factorization (NMF), we develop a prognostic model that captures clinically adverse, cryptic variation such as focal 5q deletions, missed by conventional chromosome analysis and thereby, adds novel, complementary information to traditional, cytogenetic based risk-stratification (e.g. ELN). The model also associates gain of chromosome 8 in Intermediate risk patients with worse outcome compared to other Intermediate risk patients (median OS = 186 compared to 446 days, Chi-square test pval=0.005) and identifies a subgroup of patients within the adverse risk category that lack deletions on chromosomes 5, 7, and 17, and that fare better than the rest of the adverse risk patients (median OS = 188 compared to 97.5 days, Chi-square test pval=0.02), likely reflecting previously identified “atypical” CK-AML patients. Last, we develop a prognostic classifier based on a combination of Neural-Network and Random-Forest based learning, that predicts disease outcome with high accuracy and is based on a three genomic feature list on chromosome bands 5q31.2, 7q31.33, and 8q24, suggesting potential for clinical implementation. Altogether, our results show that low coverage, sparse whole genome sequencing combined with advanced learning methods can be applied clinically to support the diagnosis and clinical management of AML disease as well as serve as a powerful tool to further a basic understanding of the genetics and biology of CNAs in myeloid neoplasms and other cancers.

Abstract Background: As mounting numbers of patients receive allogeneic hematopoetic stem cell transplantation (allo-SCT) for hematologic malignancies, focus on survivorship and post-transplant complications is increasing. 30-60% of patients develop pulmonary complications, making the lungs the most affected organ post-transplant. While obstructive lung disease post-allo-SCT has been studied as a manifestation of graft-versus-host-disease (GVHD) in the form of bronchiolitis obliterans syndrome, many patients' post-transplant pulmonary function tests (PFTs) reveal restrictive patterns of disease which have been understudied. The pathophysiology, risk factors, and clinical course of restrictive lung disease (RLD) post-allo-SCT have not been fully elucidated. This retrospective study sought to characterize baseline characteristics, imaging findings, and possible risk factors of patients with RLD post-allo-SCT. Methods: The study included all patients receiving allo-SCT at our institution between 2005 and 2021 with at least one screening PFT with a restrictive pattern. Restriction is defined as normal forced expiratory volume in one second (FEV1) to forced vital capacity (FVC) ratio and total lung capacity (TLC) less than the lower limit of normal. Data collected via chart review included demographic information; indication for and type of transplant; myeloablative or nonmyeloablative conditioning; pre-existing lung disease; history of lung or chest-wall irradiation; acute post-transplant complications; documented acute or chronic graft-versus-host-disease (GVHD) of the lungs, skin, or other organs; and chest imaging findings on x-ray or computed tomography. For patients with at least two PFTs (n=168), average rate of change of TLC since transplant was calculated. Average monthly change in TLC post-transplant was compared between multiple groups detailed under Results. Analysis of variance or unpaired t-test and linear regression were used for comparison of categorical and continuous variables, respectively. Statistical analyses were completed using BlueSky Statistics 10.3.4, R version 4.1.3. Results: 234 patients were included. Median age at transplant was 51 years (range 18-74), and 163 (70%) were male. Average BMI at transplant was 29.6 (17.9–51.4). 107 (46.3%) underwent myeloablative conditioning, and 124 (53.2%) underwent reduced intensity or nonmyeloablative regimens. The most common indications for transplant were AML (n=87), MDS (n=41), and ALL (n=40). Most had no pre-existing lung disease (n=131, 56.2%), and 61 (26.1%) had evidence of restriction on pre-transplant PFTs. About half (n=119, 51.1%) had a history of lung or chest-wall irradiation. Within 30-days post-transplant, 55 (23.5%) had pulmonary complications (pneumonia or other hypoxic respiratory failure). 151 (64.8%) had either acute or chronic skin GVHD; 91 (39.1%) carried diagnoses of pulmonary GVHD. Most common associated imaging findings were infiltrates (n=120), scarring/atelectasis (n=73), pleural effusion (n=62), and air-trapping (n=50). Mean rate of change in TLC following transplant among all subjects was -0.0473 L/month. Comparative analysis revealed no statistically significant differences in mean values of average change in TLC between those with myeloablative and nonmyeloablative regimens (-0.0733 vs -0.0227 L/month, p = 0.176); pulmonary GVHD or not (-0.0752 vs -0.0203 L/month, p=0.141); GVHD or not (-0.0514 vs -0.0373 L/month, p=0.731); or with or without prior chest irradiation (-0.0234 vs -0.0687 L/month, p=0.226). Women had, on average, positive change in TLC compared to men (+0.00963 vs -0.0709 L/month, p=0.049). Decline in TLC was faster in overweight or obese patients (p=0.006). Conclusion: Our study establishes and describes a cohort of patients with restrictive lung disease post-allo-SCT, a poorly understood and incompletely characterized, yet highly morbid, set of diverse entities into which our findings provide insight. Based on the descriptive analysis we completed, patients experience decline in TLC due to a variety of processes – infiltrative pathology, pleural effusions, and chest wall weakness/restriction. Rate of decline increases with BMI and male gender. Diagnosis of pulmonary GVHD does not seem related to progression of restriction. As more long-term data is obtained from screening PFTs, examining larger datasets may allow for more granular analysis of the numerous possible etiologies.

Abstract Background: For patients with B-cell acute lymphoblastic leukemia (B-ALL), extramedullary relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) carries an extremely unfavorable prognosis. As a new immunotherapy, chimeric antigen receptor T (CAR-T) cell therapy has shown remarkable effects in refractory or relapsed B-ALL (r/r B-ALL). However, there is still a lack of evidence for its efficacy and safety in patients with extramedullary relapse after allo-HSCT. The aim of this study was to evaluate the safety and efficacy of allogeneic CAR-T in such high-risk populations. Method: We conducted a prospective clinical study, during which 7 patients with B-ALL who experienced extramedullary relapse after allo-HSCT were enrolled between October 2019 and January 2025. These patients all received allogeneic CD19 CAR-T cell therapy. We prospectively evaluated the safety, efficacy, and survival outcomes following CAR-T treatment. This study was registered at www.chictr.org.cn (No. ChiCTR2000036350). Results: This study included 7 patients with extramedullary relapse after allo-HSCT. Median age was 21 years (range: 15 - 46 years), and the median follow-up time was 415 days (range: 130 - 1320 days). The last follow-up was conducted until July 5, 2025. All the patients were classified as high-risk patients before transplantation. Four of them were Philadelphia chromosome/BCR-ABL positive (Ph+). The sites of extramedullary relapse included: 5 cases of central nervous system (among which 2 cases were accompanied by BCR-ABL molecular relapse in the bone marrow), 1 case of testicular relapse, and 1 case of extensive extramedullary relapse. The median interval from transplantation to extramedullary relapse was 628 days (44 - 1225 days). All patients received chemotherapy, radiotherapy or targeted therapy to reduce tumor burden before infusion. The infusion dose of CAR-T cells was 4 - 10 × 10⁶/kg. After infusion, one patient developed grade 3 cytokine release syndrome (CRS) and grade 4 immune effector cell-related neurotoxicity syndrome (ICANS), while the remaining patients did not experience grade 2 or higher CRS or ICANS. No patients developed graft-versus-host disease (GVHD), and all adverse events were resolved. In terms of therapeutic efficacy, one patient was considered unresponsive at the first assessment after infusion (54 days after infusion). The remaining 6 patients all achieved complete remission (CR) efficacy. The median duration of CR was 275 days (range: 120 - 1305 days). During the follow-up period, one patient suffered from central nervous system relapse again at 275 days post-infusion, while the other 5 maintained a continuous CR. The expansion of CAR-T cells in peripheral blood peaked between days 8 to 15 post-infusion, with a median peak of 1.90E+05 copies/μg DNA (range: 1.78E+04 – 3.18E+05 copies/μg DNA), and the longest duration of detectable expansion was 1320 days. Furthermore, CAR-T cells were detected in the cerebrospinal fluid of three patients, indicating their capability for targeted migration and central nervous system infiltration. Conclusion: Overall, allogeneic CAR-T therapy has demonstrated excellent safety and durable anti-leukemia effects in high-risk ALL patients with extramedullary relapse after transplantation.

Abstract Background: The addition of the CD19/CD3 bispecific T-cell engager, blinatumomab, to standard consolidation chemotherapy in adults with ALL who achieved a measurable residual disease negative (MRDneg) remission (CR), demonstrated an improvement in 3-year overall survival (OS, 85% vs 68%, HR 0.41, P=0.002) and 3-year relapse-free survival (RFS, 80% vs 64%, HR 0.53) compared to conventional chemotherapy in the ECOG-ACRIN E1910 study (Litzow et al, NEJM 2024). Given the complex therapy in this study, treatment delays and modifications are expected. We herein explored the impact of such delays on patient outcomes. Methods: In the phase 3 ECOG-ACRIN E1910 trial (NCT02003222), adults aged 30-70 years with newly diagnosedALL who had achieved MRDneg CR following induction and intensification were randomized to consolidation chemotherapy with blinatumomab (blina arm) or chemotherapy alone (chemo arm). We examined the association between the timing of the initiation of maintenance therapy and OS and RFS. The expected duration of consolidation was 252 days vs 126 days for patients on the blina and chemo arms, respectively. For this analysis, participants were classified into two groups (no/short delay or long delay) depending on whether they started on time/before or after the median time between the beginning of consolidation and start of maintenance therapy for their treatment group (medians: 335 days, range, 181-457 days vs 176 days, range, 139-265 days for blina and chemo arms, respectively). Multivariate analyses of OS and RFS were performed to examine the effect of no/short delay vs. long delay in starting maintenance. Patients were stratified according to their assigned consolidation treatment arm, and the models were further adjusted for age, sex, white blood cell count, platelets, hemoglobin, peripheral blood blasts, bone marrow blasts, performance status and genetic-genomic risk at diagnosis. Results: Of the 488 patients enrolled, 224 MRDneg patients were randomized to consolidation chemotherapy with or without blinatumomab and 135 of the 224 went on to maintenance therapy on study (N= 66 on blina arm and 69 on chemo arm, respectively). The median follow-up from the time of maintenance registration was 43.4 months. There were no significant differences in baseline characteristics between patients in either arm who experienced no/short delay or long delay. In the blina group, 60 of 66 patients (90.9%) received all 8 cycles of consolidation therapy of which 31 (45.6%) had long delays. Sixty-eight of 69 patients on the chemo arm (98.5%) received all cycles of consolidation therapy, of which 34 (50%) had a long delay. Strikingly, patients who had a long delay before initiation of maintenance had a significant improvement in OS in multivariate analysis compared to patients who had no/short delay (HR 0.31, 95% CI: 0.11-0.91; P =0.03). However, within each treatment group, OS benefit did not reach statistical significance (blina arm: HR 0.04, 95% CI: 0.001-1.64; P =0.09; chemo arm: HR 0.32, 95% CI: 0.08-1.38; P =0.13). Similar results were observed for RFS in multivariate analysis (HR 0.40, 95% CI: 0.16-1.01; P =0.05), though this impact on improved RFS was noted in the chemo arm but not in blinatumomab treated patients (blina arm: HR 0.56, 95% CI: 0.10-3.24; P =0.52; chemo arm: HR 0.19, 95% CI: 0.04-0.83; P=0.03). Additionally, patients who had no/short delay before starting maintenance experienced a longer median duration of maintenance treatment (blina arm, 548 days; chemo arm, 708 days) compared to patients who had a long delay (blina arm 488 days; chemo arm 598 days) before initiation of maintenance (P=0.0008). Conclusion: In the phase 3 randomized ECOG-ACRIN E1910 clinical trial, long delays between initiation of consolidation therapy and start of maintenance therapy were associated with improved OS compared to no/short delays. However, within each treatment group (blina or chemo), no significant difference of OS was observed. We postulate that these longer delays allowed more patients to receive all of the recommended protocol-assigned therapy thereby resulting in improved survival. Furthermore, patients who had no/short delays had a significantly longer duration of maintenance therapy. These data indicate that treatment delays during consolidation do not worsen survival. Further studies are being done to better understand why patients with long delays had better overall survival.

Abstract Introduction: IRAKLIA is an international, open-label, non-inferiority (NI) trial (NCT05405166) investigating isatuximab (Isa) subcutaneous (SC) vs intravenous (IV) administration, plus pomalidomide-dexamethasone (Pd) and the first Phase 3 multiple myeloma (MM) trial using an on-body injector (OBI). IRAKLIA demonstrated NI in its co-primary endpoints: overall response rate (ORR) and steady state trough concentration (Ctrough; Cycle(C) 6 Day(D) 1 predose). IsaOBI offers hands-free administration of flat-dose Isa, a small, hidden, retractable needle to prevent sharps injury and low-pressure delivery. Here, we examine the effect of body weight (BW) on pharmacokinetics (PK) as well as efficacy and safety outcomes with flat-dose IsaOBI vs IV + Pd in IRAKLIA. Methods: Patients (pts) with relapsed/refractory MM ≥18 years (yr) with ≥1 prior line of therapy (LOT) were randomized 1:1 to IsaOBI (1400mg; n=263) or IV (10mg/kg; n=264 weekly in C1, then every 2 weeks + P (4mg/day, D1–21) + d (40mg [20mg if ≥75yr] weekly) in 4-week cycles. This analysis is run by BW (≤65kg, >65–≤85kg, >85kg) which was a stratification factor, and extreme BW (≤50kg, >50–≤100kg, >100kg). Results: Number of pts per BW group were: ≤50kg [OBI n=16, IV n=14], ≤65kg [OBI n=84, IV n=85], >65–≤85kg [OBI n=117, IV n=118], >85kg [OBI n=62, IV n=65], and >100kg [OBI n=22, IV n=22]. Baseline (BL) demographic and disease characteristics were generally balanced across BW groups for IsaOBI vs IV, including age (median 66yr) and prior LOT (median 2). However, in the >100kg group, more IsaOBI vs IV pts exhibited poor prognostic characteristics including plasmacytoma, International Staging System Stage II/III disease, beta 2-microglobulin level ≥5.5mg/L, estimated glomerular filtration rate <60mL/min/1.73m2 and a lower very good partial response (VGPR) rate as best overall response at last regimen. Flat-dose IsaOBI showed adequate exposure (C2D1 Ctrough) for all BW groups, with geometric mean ratios (90% CI) vs IV >1: ≤65kg (1.628 [1.294–2.048]), >65–≤85kg (1.303 [1.089–1.560]) and >85kg (1.006 [0.817–1.239]). IsaOBI ORRs were comparable to IV across BW: ≤65kg, 66% vs 71% (relative risk [RR]: 0.928), >65–≤85kg, 70% vs 70% (RR: 1.009), and >85kg, 81% vs 72% (RR: 1.115). For extreme BW groups, ORRs (95% CI) were similar between IsaOBI and IV for ≤50kg group [56% vs 60%] and for >50–≤100kg [72(66–78)% vs 70(63–76)%] but lower [68% vs 86%] in >100kg group. An exposure-response (E-R) analysis showed the impact of BW on response: IsaOBI pts ≤50kg tended to respond less vs IsaOBI pts >50kg despite correct exposure because they were confounded by BL disease characteristicsincluding a higher proportion of high-risk cytogenetics and plasma cells in the bone marrow vs other BW group pts. For IsaOBI and IV, Grade (Gr)≥3 treatment-emergent adverse events (TEAEs) and Gr≥3 treatment-related TEAEs decreased with increasing BW. They were similar between arms in ≤65kg group (OBI vs IV, Gr≥3 TEAEs: 87% vs 88%; Gr≥3 treatment-related TEAEs: 73% vs 77%). A similar trend was observed in extreme BW groups along with similar incidences between arms in ≤50kg group. While TE serious AEs (TESAEs) and treatment-related TESAEs decreased with increasing BW for IsaIV, incidence was stable in the IsaOBI arm. OBI arm OBI Gr5 TEAEs were similar between groups and arms, except for higher incidence in ≤65kg group (12% vs 5%) with OBI vs IV that was not reflected in ≤50 or >50–≤100kg groups. Treatment discontinuation rates for all drugs with IsaOBI vs IV were 14% vs 6% (≤65kg), 8% vs 10% (>65–≤85kg), and 2% vs 10% (>85kg). Similar incidence of Gr≥3 laboratory (lab) neutropenia was observed across BW in IsaOBI: 86.9% (≤65kg), 83.5% (>65–≤85kg) and 83.9% (>85kg). Higher rates of Gr≥3 lab neutropenia were observed in ≤50kg group (93.8%, IsaOBI vs 71.4%, IsaIV), which did not translate into higher rates of neutropenic complications (18.8% vs 14.3%). The E-R analysis revealed no relationship between Isa PK exposure and safety for OBI and IV arms. Conclusions: No notable impact from IsaOBI flat dosing was observed across BW groups. Flat-dose Isa OBI showed consistent safety and efficacy across different BW groups, with differences likely linked to BL disease characteristics according to the E-R analysis. The IsaOBI C2D1 Ctrough, a time-independent predictor of efficacy, was similar to, or higher vs IsaIV in each BW group, supportive of a flat dose providing adequate exposure without need for adjustment.

Abstract Introduction: IRAKLIA (NCT05405166) is an ongoing, global, non-inferiority trial of isatuximab (Isa) subcutaneous (SC) administration plus pomalidomide-dexamethasone (Pd), and the first Phase 3 multiple myeloma (MM) trial using an on-body injector (OBI) for SC administration. In IRAKLIA, Isa SC OBI demonstrated non-inferiority in the 2 co-primary endpoints of efficacy and pharmacokinetics compared with Isa intravenous (IV). Significantly more patients expressed higher satisfaction with Isa SC OBI vs Isa IV in IRAKLIA, and more patients and health care providers (HCPs) preferred Isa SC OBI over Isa SC manual push in the Phase 2 IZALCO trial (NCT05704049). The Isa OBI is a wearable, automated injector that adheres to the skin of the abdomen and administers Isa SC with the push of a button without any batteries or electronics. The Isa SC OBI offers hands-free administration; a small, hidden, retractable needle to prevent sharps injury and reduce patient anxiety; low-pressure delivery; a simplified user interface; and flexible administration in either outpatient or home settings. Here, we examine the safety of Isa SC OBI administered by trained nursing professionals during at-home patient visits in IRAKLIA. Methods In IRAKLIA, patients with relapsed/refractory MM (RRMM) aged ≥18 years with ≥1 prior line of therapy (LOT) were randomized 1:1 to Isa SC OBI (1400 mg; n=263) or IV (10 mg/kg; n=264) weekly in Cycle (C)1, then every 2 weeks + P (4 mg/day, Day [D]1–21) + d (40 mg [20 mg if age ≥75 years] weekly) in 4-week cycles. Home administration by a HCP was proposed as an option after 5 cycles for Isa OBI arm patients on D15 from C6 onward, and D1 visits from C6 remained clinic based. Eligibility for home-administration depended on an absence of infusion reactions (IRs) at C4 and C5, hematology test results at D1 of each cycle, investigator judgement, and patient willingness. During at-home visits, providers prepared and applied Isa SC OBI and safely disposed of the device upon completion. Following at-home administration, providers evaluated the injection site for reactions, took vitals, and completed documentation. No specific monitoring was planned after the end of injections. At-home administration was not allowed in some countries due to local regulations. Results In the ongoing IRAKLIA trial, 202 patients were treated with Isa SC OBI within countries where at-home administration was permissible. 11 (5.4%) of these patients from 5 different countries [Australia (n=6), Hungary (n=2), Italy (n=1), Norway (n=1), and Spain (n=1)] have participated in home administration as of the cutoff date (06-Nov-2024), with additional sites and countries initiated after the cutoff date. First at home administrations started at Cycle 6 for the majority of patients (n =7) and at Cycle 7 (n =1), Cycle 8 (n =2), and Cycle 10 (n =1) for the remaining patients. Among the 11 patients participating in at-home visits, more than half switched to at-home administration and have not returned to the hospital for their next Day 15 cycle visit. 55 injections were performed at home. The median injection duration was the same between clinic and at-home administration (13 minutes). Similar to Isa SC OBI use in the clinic, home administration was well tolerated with no new safety signals and a 100% completed injection rate. No at-home Isa OBI administration was omitted or interrupted during the injection. At-home administration had a very low rate of injection-site reactions (ISR; n=1). The single ISR was a Grade 1 episode consisting of injection swelling, which resolved within the same day, and most subsequent Day 15 administrations were performed at home for this patient. No other adverse events (AEs), including no IRs, were linked to at-home visits. No device event linked to at-home visits was reported. Conclusions Initial data from the ongoing IRAKLIA trial support the safety of at-home administration of Isa SC OBI for the treatment of patients with MM. Home administration was well tolerated, with no safety concerns and a median injection time of 13 minutes consistent with in-clinic use of Isa SC OBI. The option of either home or outpatient administration of Isa SC OBI for patients with MM allows for greater flexibility and accessibility of treatment, with the potential to improve patient care and reduce common barriers to patient retention and therapy compliance.

Abstract Background: Follicular lymphoma (FL) is a germinal center–derived B cell malignancy characterized by the clonal expansion of a dominant malignant B cell population. While prior studies have identified transcriptional subtypes across patients, most analyses have treated B cells within individual tumors as a transcriptionally uniform population. However, this assumption has not been systematically tested using high-resolution, clonotype-resolved transcriptomic data. The broader landscape of intratumoral B cells—including those not belonging to the dominant clone—remains poorly defined, and their roles in disease biology are not well understood. These unexpanded, intratumoral B (ITB) cells may include residual non-malignant populations, early-stage malignant cells, or immune-modulating cells with distinct roles in the tumor microenvironment. It is also unknown whether their presence varies across patients or correlates with clinical features or immune microenvironmental interactions. Methods: We performed integrated single-cell 5′ RNA sequencing and B cell receptor (BCR) repertoire sequencing on 7 newly diagnosed FL 1-3A fresh-frozen lymph node biopsies (Dasari et al., Blood Cancer Discov 2025). Using a high-confidence approach that incorporates heavy and light chain pairing, V and J gene usage, and CDR3 nucleotide junction identity, we classified B cells into two groups: (1) cells belonging to the dominant expanded clone (FL B cells) and (2) all other B cells with detectable and non-expanded BCRs (ITB). These clonal identities were then integrated with single-cell transcriptomic profiles using Seurat and Immcantation pipelines. Differential expression analysis was conducted using edgeR to compare FL B cells to ITB cells across all FL biopsies. Results: After quality filtering, a total of 44,637 single cells were retained across all 7 samples (minimum per sample: 3,847 cells), including malignant and non-malignant B cells as well as diverse tumor microenvironment populations. The proportion of B cells assigned to the dominant FL clone varied substantially across tumors, ranging from 22% to 89%, indicating that some tumors contain a substantial population of ITB cells. In one tumor, we identified two expanded malignant B cell clones comprising 40.6% and 34.4% of all cells. These clones exhibited non-overlapping V and J gene usage (IGHV3-11/IGHJ5 vs. IGHV3-72/IGHJ3), distinct CDR3 junctions, and different immunoglobulin isotypes (IGHG1 vs. IGM). BCL2 was expressed in most cells within both clones (Clone 1: 87.8%, Clone 2: 67.0%), with mean log-normalized expression levels of 1.79 and 0.95, respectively. Both clones formed distinct UMAP clusters and showed transcriptional divergence from ITBs, with 453 differentially expressed genes (DEGs) identified for Clone 1 and 98 for Clone 2 (adjusted p<0.01, |log₂FC|>1, min.pct≥0.25). Additionally, 748 DEGs were identified between the two clones. This evidence of clonal divergence within a single FL tumor reinforces the need to reconsider intratumoral homogeneity in FL and suggests that multiple malignant clones may sometimes coexist. When comparing FL clones to ITB cells across tumors we found that FL clones exhibited a transcriptional program enriched for proliferation and cell cycle regulators, including MKI67 (p<0.005), E2F1 (p<0.0001), CDKN2A (p<0.0001), and CDKN2B (p<0.01), as well as elevated expression of AICDA (p<0.01), EZH2 (p<0.0001), and PD-L1 (p<0.05). As expected, the malignant cells also had higher expression of BCL2 (p<0.01) and CD10/MME (p<0.0001). In contrast, ITB cells demonstrated relatively higher expression of SELL (p<0.0001) and TNFRSF14 (p<0.05), which were significantly downregulated in the FL clone. Conclusions: Together, these findings challenge the prevailing notion that FL tumors are defined by a single homogeneous malignant B cell population. Instead, our data support a model in which multiple transcriptionally and functionally distinct B cell populations coexist within tumors, including dominant clones and a diverse population of ITB cells. This is, to our knowledge, the first study to comprehensively characterize these populations using integrated, lineage-aware single-cell multiomic profiling across FL patients. These insights may ultimately inform new strategies for understanding tumor evolution, immune evasion, and therapeutic targeting in follicular lymphoma.