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Abstract Background: Monoclonal B-cell lymphocytosis (MBL), a precursor to chronic lymphocytic leukemia (CLL), is an understudied yet common premalignant condition present in ~8 million adults in the United States. Based on flow cytometry, MBL can be classified into two immunophenotypes: CLL-type (CD5, CD23, and CD20 co-expression) and non-CLL-type (CD5-negative). While the majority of the data to date pertains to CLL-type MBL, the available evidence indicates non-CLL-type MBL is also associated with an increased risk of hematologic malignancies. Clonal hematopoiesis of indeterminate potential (CHIP) is another precursor condition associated with hematologic malignancies. The relationship between non-CLL-type MBL and CHIP and their combined effect remains unknown. Herein, we report findings on these two precursor conditions in the largest screening cohort to date. Methods: Using flow cytometry, we screened for MBL in the Mayo Clinic Biobank participants who were 40 years or older with no prior history of hematologic cancers. Using whole-exome sequencing of whole-blood DNA, CHIP was screened on 291 genes related to myeloid (56 genes) or lymphoid malignancies (235 genes). Incident hematologic malignancies were detected during follow-up using International Classification of Diseases (ICD) codes in the medical record. All diagnoses were manually reviewed for confirmation. Multivariable logistic regression was used to evaluate the association between non-CLL-type MBL and CHIP. Time to incident hematologic malignancy was calculated from date of MBL screening to the earliest date of incident malignancy, withdrawal, death, last medical visit, or study end. Overall survival (OS) was calculated from date of MBL screening to date of death or last known alive. Multivariable Cox regression, adjusted for age, sex and residency, was used to investigate associations between non-CLL-type MBL and CHIP with clinical outcomes; with results reported using hazard ratios (HR) and 95% confidence intervals (CI). Results: In total, 8,802 individuals with MBL screening and CHIP data were analyzed. Non-CLL-type MBL was detected in 249 (2.8%) individuals; 121 (49%) were male, and median age was 78 years (range, 47-95). We identified 757 (8.6%) individuals with CHIP in at least one of the 291 genes tested. The most frequently mutated CHIP genes were DNMT3A, TET2, ASXL1, PPM1D, and TP53. A total of 47 (0.5%) individuals had both non-CLL-type MBL and CHIP; the four genes with the highest number of CHIP variants in these individuals were DNMT3A (n=16), TET2 (n=10), ASXL1 (n=3), and ATM (n=3). An association between non-CLL-type MBL and any CHIP (OR=1.6, 95%CI:1.2-2.3, P=0.006) was observed. When analyzing CHIP in genes related to myeloid malignancies, the association with non-CLL-type MBL was also significant (OR=1.6, 95%CI:1.1-2.3, P=0.012); however, the association was not statistically significant for genes related to lymphoid malignancies (OR=1.6, 95%CI:0.8-3.3, P=0.165). With a median follow-up of 5.4 years, 104 individuals developed incident hematologic malignancies (66 lymphoid and 38 myeloid malignancies). Non-CLL-type MBL (HR=3.5, 95%CI:1.9-6.5, P<0.001) and CHIP (HR=3.2, 95%CI:2.1-5.1, P<0.001) were each associated with increased risk of incident hematologic malignancies. Co-existence of both precursor conditions was associated with a substantially higher risk of incident hematologic malignancies (HR=10.3, 95%CI:4.0-26.2, P<0.001) compared to individuals with neither precursor condition. Among individuals with non-CLL-like MBL, any CHIP was a borderline significant predictor for incident hematologic malignancy (HR=3.6, 95%CI:1.0-12.9, P=0.049). Compared to individuals with no precursor conditions, OS was not significantly different in those with non-CLL-type MBL-only (HR=1.1, 95%CI:0.8-1.5, P=0.40), those with CHIP-only (HR=1.2, 95%CI:0.99-1.4, P=0.06), or those with both CHIP and non-CLL-type MBL (HR=1.3, 95%CI:0.8-2.1, P=0.39). Conclusions: In the largest screening cohort to date evaluating the relationship of CHIP and non-CLL-type MBL, we found that non-CLL-type MBL and CHIP are associated with each other. Individuals with non-CLL-type MBL were more likely to have CHIP variants in DNMT3A, TET2, ASXL1, and ATM. Among individuals with non-CLL-type MBL, the presence of any CHIP was associated with increased risk of developing hematologic malignancy.

Abstract Introduction Obecabtagene autoleucel (obe-cel) and brexucabtagene autoleucel (brexu-cel) are CD19 targeted chimeric antigen receptor T cell (CAR-T) therapies, approved for the treatment of adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (ALL). Mechanistic differences between obe-cel and brexu-cel including differing costimulatory domains (4-1BB vs. CD28), CD19 binding domains (intermediate vs. high affinity) and split dose (Days 1 and 10) vs. single infusion may impact in-vivo cellular kinetics that translate into variant clinical outcomes. In pivotal trials, obe-cel resulted in lower rates of severe cytokine release syndrome (CRS) and immune effector cell associated neurotoxicity syndrome (ICANS) compared to brexu-cel with comparable efficacy (Roddie et al., NEJM 2025; Shah et al., Lancet 2021). Real-world utilization and outcomes with obe-cel are unknown given the relatively recent approval. Methods The ROCCA database, comprising real world data from patients (pts) with r/r ALL treated at 40 North American institutions was utilized in this analysis. Pts with r/r ALL were eligible if they were apheresed for obe-cel since its approval (11/8/2024) or brexu-cel over a comparable period (since 8/1/24) and had at least 30 days of follow up. Data cut off was 7/15/2025. CRS/ICANS were graded per ASTCT criteria. Measurable residual disease (MRD) was assessed by flow cytometry and/or next generation sequencing per institutional standards. Results 38 pts have undergone apheresis for obe-cel (36 infused, all received both infusions) and 54 (53 infused) for brexu-cel over the study period. Pts in the obe-cel and brexu-cel cohorts had the following baseline characteristics: median age, 47 vs. 39 years; ECOG 2+, 15% vs. 26%; Ph+ disease, 24% vs 13%; KMT2Ar, 0 vs. 4%; TP53m, 11% vs 11%, and hypodiploid karyotype, 5% vs 6%. The following prior treatment patterns were observed: median lines of therapy before CAR-T 3 vs. 3; prior SCT 24% vs. 30%, prior blinatumomab 68% vs. 46%, prior inotuzumab 45% vs. 30%. At apheresis, active disease (>5% bone marrow blasts) was present in 47% vs. 55% of obe-cel and brexu-cel pts, respectively; the remainder were in CR (with 18% vs. 22% in MRD- CR, respectively). Among obe-cel (n= 35 [92% of cohort]) and brexu-cel (21 [38% of cohort] pts with disease re-assessment prior to lymphodepletion (LD), 31% vs. 43% had active BM disease, respectively; few pts (24% vs. 17%) had >20% marrow disease burden prior to LD. CAR-mediated toxicity differed significantly between the cohorts. CRS occurred in 56% of obe-cel pts compared to 94% of brexu-cel pts (p < 0.0001). There were no Gr3+ CRS events among the obe-cel pts; 3 (6%) brexu-cel pts had Gr3+ CRS (p = 0.27). ICANS occurred in 17% of obe-cel pts vs. 51% of brexu-cel pts (p = 0.001). Gr3+ ICANS occurred in 6% of obe-cel vs. 32% of brexu-cel pts (p = 0.0027). Among the obe-cel pts, CRS occurred in 31% after the first infusion and 46% after the second; ICANS occurred in 3% after the first infusion and 15% after the second. Prolonged Gr4 neutropenia (ANC < 500 cells/uL beyond day 30 from infusion) occurred in 24% of obe-cel vs. 28% of brexu-cel pts (p = 0.73). Deaths within the first 28 days of infusion occurred in 0 obe-cel pts and 4 brexu-cel pts (2 of infection, 1 of infection/brain bleed, and 1 of liver failure in the setting of Gr4 CRS and HLH). Response rates were high and did not significantly differ between cohorts (p = 0.85). Among the 31 obe-cel pts with available response data, 25 (81%) achieved an MRD- CR/CRi, 3 (10%) had an MRD+ CR/CRi, 2 (6%) had a CR/CRi with unknown MRD, and 1 (3%) did not respond. Among 41 brexu-cel pts with available response data, 33 (80%) had an MRD- CR/CRi, 4 (10%) an MRD+ CR/CRi, and 4 (10%) CR/CRi with unknown MRD. Conclusion Pts selected for obe-cel apheresis were similar to those for brexu-cel over the study period (noting that not all centers had access to obe-cel during this time). Similar to clinical trial results, obe-cel was associated with lower rates of CRS/ICANS. Rates of MRD-negative CR were high and did not differ between cohorts. A larger sample and longer follow up are required for further analyses; we anticipate a cohort of ~75 obe-cel treated pts by the annual meeting and will provide updated data.

Abstract INTRODUCTION Immune checkpoint inhibitors (ICIs) have emerged as a cornerstone of cancer therapy. However, despite their efficacy, ICIs can cause a unique spectrum of autoimmune toxicities known as immune-related adverse events (irAEs). In contrast to irAEs involving other organ systems, hematologic irAEs such as ICI-associated immune thrombocytopenia (ICI-ITP) are less common. As a result, existing data on ICI-ITP are largely confined to isolated case reports, single-center case series, and pharmacovigilance databases lacking granular clinical data. To address this key knowledge gap, we sought to comprehensively characterize the incidence, risk factors, clinical features, treatments, and outcomes associated with ICI-ITP. METHODS We performed a multicenter cohort study of adult patients who initiated ICI therapy at 29 hospitals across 7 major cancer centers in 11 geographically diverse states in the US between 2016-2023. ICI-ITP was defined as a decline in platelet count to <100 x109/L in the absence of an alternative more plausible etiology of thrombocytopenia. Patients with hematologic malignancies were excluded, as were those who received cytotoxic chemotherapy within 30 days prior to thrombocytopenia onset. For each patient identified as having ICI-ITP, we collected data on demographics, comorbidities, medications, laboratory values, treatments, and outcomes. All data were extracted by manual chart review. To identify risk factors for ICI-ITP and to examine its association with death, for each case of ICI-ITP we also collected data on two control patients who initiated ICI therapy at the same site and in the same year but without development of ICI-ITP. We used multivariable logistic regression to identify independent risk factors for ICI-ITP and its recovery (the latter defined according to criteria established by the ITP International Working Group). We used a multivariable Cox model to examine the association between ICI-ITP and its severity with all-cause mortality. RESULTS We identified a total of 214 patients who developed ICI-ITP among 86,648 examined (0.25%). The incidence was highly consistent across sites (range, 0.15–0.30%). Risk factors for ICI-ITP included simultaneous receipt of two different classes of ICIs, additional irAEs, and a lower baseline platelet count. ICI-ITP developed at a median of 8 weeks (IQR, 4–18) following ICI initiation. The median nadir platelet count was 41 x109/L (IQR, 17–64). Six out of 214 patients (2.8%) developed a major bleed, and 16 patients (7.5%) developed a clinically relevant non-major bleed. Cell-bound anti-platelet antibody testing was positive in 6 of 8 patients (75.0%) for whom it was assessed, and median circulating thrombopoietin levels (201 pg/mL [IQR, 178–295]) were similar to those seen in primary ITP. Treatments used included glucocorticoids (49.5%), immune globulin (18.2%), and thrombopoietin receptor agonists (13.6%). Overall, 161 patients (75.2%) recovered from ICI-ITP at a median of 2 weeks (IQR, 1–5) following ICI-ITP onset. Predictors of recovery included additional irAEs and a higher nadir platelet count. Treatment response was observed in 57.0%, 56.4%, and 58.3% of patients within 60 days following initiation of glucocorticoids, immune globulin, and thrombopoietin receptor agonists, respectively. Of 76 patients rechallenged with an ICI, 23 (30.3%) developed recurrent ICI-ITP at a median of 9 weeks (IQR, 2–15); 17 of these 23 patients (73.9%) recovered. Finally, ICI-ITP and its severity were monotonically associated with a higher risk of death (adjusted hazard ratio 2.96 [95% CI, 2.14–4.08] for those with severe ICI-ITP compared to those without ICI-ITP). CONCLUSION In this multicenter study involving patients treated with ICIs at 29 hospitals across the US, we identified 214 patients with ICI-ITP. For the first time, we characterize in detail the incidence, risk factors, clinical features, treatments, and outcomes of ICI-ITP, a relatively novel disease entity. We found that more than half of patients responded to conventional ITP-directed therapies, and that most patients rechallenged did not develop recurrent ICI-ITP. We also found that ICI-ITP was independently associated with an increased risk of death, including a nearly 3-fold increased risk in those with severe ICI-ITP. These findings highlight ICI-ITP as a rare but clinically significant complication of ICI therapy that hematologists must be equipped to recognize and manage.

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 Background Acute graft-versus-host disease (GVHD) is a major cause of non-relapse mortality (NRM) after allogeneic hematopoietic cell transplantation (HCT). High-dose steroids are standard first-line therapy for grade II–IV acute GVHD, whereas systemic treatment (tx) is generally not recommended for grade I. However, in practice many patients (pts) with grade I GVHD receive systemic steroids. A prior GITMO randomized trial (n=173) of grade I GVHD to either systemic steroid tx or “watch and wait” found that preemptive steroid tx reduced progression to grade II but not grade III/IV GVHD, increased serious infections, and resulted in similar chronic GVHD, NRM and survival (Bacigalupo, Haematologica 2017). In this study we analyzed real world evidence for early systemic steroid use and the potential impact of serum biomarkers in grade I GVHD. Methods We analyzed clinical data and serum samples from pts with grade I acute GVHD at 24 Mount Sinai Acute GVHD International Consortium (MAGIC) centers between 2014 and 2022 who were treated according to physician discretion. Pts were divided into a preemptive steroid tx group or a watch-and-wait group (systemic steroids administered only if progression to grade II–IV GVHD). Preemptive steroid use was treated as a time-dependent covariate and a frailty proportional hazards model with random effects was used to adjust for center effects to account for possible heterogeneity in clinical practices across transplant centers. Serum samples collected at the diagnosis of grade I GVHD were analyzed for ST2 and REG3α to calculate validated Ann Arbor (AA) scores (1, 2, 3). Results Grade I GVHD was diagnosed in 1143 pts; 591 (52%) received preemptive tx and 552 (48%) were treated by a watch-and-wait strategy. In the preemptive tx group, steroids were initiated at a median of 0 days and within 7 days for >90%. The median initial dose of steroids was 1 mg/kg of prednisone or its equivalent. In the watch and wait group, only 184 pts (33%) required systemic steroids for progression to grade II-IV GVHD at a median of 14 days from grade I diagnosis. Preemptive steroid tx reduced the risk of grade II–IV acute GVHD (HR, 0.71; 95% CI, 0.56–0.89; P=0.003), but not the risk of grade III/IV acute GVHD (HR, 1.03; 95% CI, 0.69–1.52; P=0.899) or chronic GVHD (HR, 1.03; 95% CI, 0.69–1.52; P=0.899), consistent with the GITMO trial. The 12-month incidence of NRM was higher for preemptive tx vs. watch and wait (13% vs 7%, P=0.002). In multivariate analysis preemptive steroid use independently predicted an increased risk of NRM (HR, 1.63; 95% CI, 1.06–2.50; P=0.026) as did several other known risk factors (older recipient age, umbilical cord blood donor, HCT-CI ≥3, and myeloablative conditioning). Greater NRM in the preemptive tx group was driven primarily by 3-fold more infectious deaths; deaths due to uncontrolled GVHD were similar for both tx groups. The risk for relapse was unexpectedly lower in the preemptive tx group (HR 0.64; 95% CI 0.47-0.88; P=0.006) and overall survival was therefore not different between groups, but risk factors for relapse such as minimal residual disease status were not available precluding further analysis of this finding. Serum was collected in 871 (76%) pts at onset of grade I GVHD for retrospective biomarker analysis. AA scores were AA1 (80%), AA2 (15%), and AA3 (5%). AA scores were highly predictive of progression to grade III/IV GVHD (AA1 vs AA2 vs AA3: 9% vs 14% vs 44%, all P<0.001) and the risk of 12-month NRM (8% vs 16% vs 39%, all P<0.001); this pattern was observed in both tx groups. The negative effect of preemptive steroid tx was most pronounced in pts with grade I/AA1 GVHD who experienced 5-fold more infectious related deaths compared to pts managed with a watch and wait approach. Conclusion Treatment of grade I GVHD with systemic steroids did not reduce the incidence of grade III/IV GVHD or deaths due to uncontrolled GVHD and instead increased the risk of NRM from infections compared to pts who were treated only after GVHD progressed. Importantly, 2/3 of the watch and wait pts never needed systemic steroid tx. These findings remained robust after adjusting for multiple confounders, including center effects, and were consistent with the GITMO trial. MAGIC biomarkers at the onset of grade I GVHD predicted outcomes and a watch and wait strategy may be best for the 80% of pts with AA1 GVHD. Better treatment options are needed for the 20% of pts with grade I and AA2/3 GVHD.

Abstract Background: Undetectable minimal residual disease (uMRD) at the end of first-line (1L) treatment (tx) with 12-cycles (C) of venetoclax (ven) + obinutuzumab (obin) is associated with prolonged survival for patients (pts) with chronic lymphocytic leukemia (CLL, Al Sawaf et al. Blood 2024). We hypothesized that MRD may be used to guide ven tx duration for CLL pts treated with 1L ven + obin. Methods In this ongoing phase II, multicenter investigator-initiated study, pts receive ven + obin for 1L tx of CLL/small lymphocytic lymphoma (NCT04447768). Eligible pts have a CIRS score of ≤ 6 and require 1L tx per iwCLL 2018 criteria. Pts receive 6 x 28-day C of obin and initiate ven on C1D22. Ven duration is dependent on peripheral blood (PB) MRD status measured by ClonoSeq next generation sequencing. At C7, pts undergo MRD testing. Pts uMRD6 (<10-6 sensitivity) at both C7 and C9 dc ven after 9C and enter treatment free observation (TFO). Pts with detectable MRD6 (dMRD6) at C7 undergo repeat testing at C12; if uMRD5 (<10-5) pts dc ven after 12C. Pts dMRD5 at C12 continue ven for an additional 12C (24C total) prior to TFO. The primary study endpoint is 36-month PFS; the unpromising rate is set at 82% and will be tested by a nonparametric survival estimate (Kaplan-Meier) along with Greenwood's formula. RNA sequencing (RNAseq) was performed pre-tx on patient bone marrow (or PB if inaspirable) samples. Unsupervised clustering using machine learning (ML) based on consensus nonnegative matrix factorization was applied to the most variable genes to identify patient clusters. Clusters were then biologically characterized by gene signature scoring using xCell algorithm and assessed for association with uMRD6 at C7 using a Fisher exact test. Results Baseline characteristics of the 100 pts who initiated tx include: median age 58 (range 34-81); 71% male, 90% White, 3% Black and 2% Asian, 5% unknown; 49% IGHV unmutated, 16% TP53 mutation, 8% del17p (previously reported, Roeker et al. ASH 2024). 3 pts stopped tx prior to C7. 51 pts were uMRD6 at C7 and C9 and completed 9C ven. 46 pts were dMRD6 at C7; 6 pts stopped tx outside of meeting protocol requirements and are included in intention-to-treat (IIT) analyses. 32 pts were uMRD5 at C12 and dc ven after 12C. 8 pts were dMRD5 at C12: 5 continued ven per protocol (3 completed 24C ven, 2 ongoing tx as of 15 May 2025 data cut-off), 2 stopped ven outside of protocol requirements (included in ITT analyses), and 1 pt withdrew consent. At a median follow-up of 35 months, the 36-month PFS rate is 90% (95% CI: 84%, 97%). 36-month OS is 94% (95% CI: 89%, 99%). Landmark PFS analyses from EOT were performed for pts who dc ven after 9C due to uMRD6 (24-month PFS 92%, 95% CI: 85, 100%, n=51) and pts who dc ven after 12C due to uMRD5 (24-month PFS 96%, 95% CI: 89%, 100%, n=32). For pts dc ven after 9C due to uMRD6 (n=51), PB MRD at 12C after EOT was: 59% uMRD6, 12% uMRD5, 4% uMRD4, 8% dMRD4 and 18% unknown. For pts dc ven after 12C due to uMRD5 status (n=32), PB MRD at 12C following EOT was: 9% uMRD6, 31% uMRD5, 9% uMRD4, 25% dMRD4 and 25% unknown. Of the 5 pts with PD, 3 pts have had Richter Transformation to diffuse large B-cell lymphoma (all uMRD6 at C7 / 9). Two pts with PD have not met iwCLL tx criteria and remain in TFO. Five pts have died (suicide, West Nile encephalitis, COVID-19, complications of glioblastoma and RT DLBCL). Five C12 dMRD5 pts who continued ven have reached C18, with only 1 of 5 converting to uMRD5 in PB. However, all 5 maintained uMRD4 (<10-4). Of 3 pts that completed 24C ven (2 ongoing tx), 1 pt had deepening of response to uMRD5 at C24, and 2 pts had rising MRD on ven (dMRD4 at C24). To investigate patient heterogeneity at baseline and its relationship to uMRD, we clustered patient RNAseq samples into two clusters using artificial intelligence/ML based unsupervised clustering. The clusters associated with uMRD6 at C7 (Fisher exact test p=0.038), and patients in the cluster with significantly higher immunosuppressive cells such as T-regulatory cells and M2 macrophages were less likely to be uMRD6 at C7. Conclusions At a median follow-up of 35 months, the estimated 36-month PFS rate is 90%. RNAseq transcriptomic analyses identified that patients with enriched immunosuppressive cells were less likely to be uMRD6 at C7. Additional follow-up is required to confirm the durability of this MRD-guided ven + obin tx strategy.

Abstract Background Hepcidin, a central regulator of iron homeostasis, is pathologically elevated in patients with myelofibrosis (MF) and anemia. Chronic hepcidin elevation limits iron availability for red blood cell production and contributes to the onset and severity of anemia, for which there is a large unmet need for safe and effective treatments. DISC-0974 is an investigational, first-in-class, monoclonal antibody that blocks hemojuvelin, a co-receptor in the bone morphogenetic protein-signaling pathway driving hepcidin expression. In studies involving healthy volunteers (Novikov, et al, J Clin Pharmacol 2024:64(8):953-962) and participants with MF (Gangat et al, Blood 2024;144(Suppl1):657), DISC-0974 dosing resulted in reduced serum hepcidin levels and increased serum iron, with a favorable safety profile. Clinically meaningful improvements in anemia were also observed: 50% of non–transfusion-dependent (nTD) participants achieved a mean hemoglobin increase of ≥1.5 g/dL for at least 12 weeks, while 80% of participants with low transfusion burden (TD low) and 40% of participants with high transfusion burden (TD high) achieved transfusion independence (TI) for ≥16 and ≥12 consecutive weeks, respectively. Aims This Phase 2, open-label, multiple-ascending dose study (NCT05320198) assesses efficacy, safety, pharmacokinetics (PK), and pharmacodynamics (PD) in participants with MF. Methods Participants were enrolled into 3 primary cohorts (n=30 per cohort), categorized by the units of red blood cells transfused in the 84 days prior to screening: nTD (hemoglobin <10 g/dL with 0 units), TD low (1-2 units), and TD high (3-12 units transfused). Additionally, an exploratory cohort of participants receiving concomitant treatment with momelotinib or pacritinib (n=10) was included. Eligible participants were ≥18 years of age with hemoglobin <10 g/dL or a transfusion requirement meeting World Health Organization diagnostic criteria for primary or secondary MF. A stable dose of concomitant hydroxyurea and/or Janus kinase (JAK) inhibitor (ruxolitinib and fedratinib for primary cohorts; momelotinib and pacritinib for exploratory cohort) was allowed. Major exclusion criteria included liver iron concentration ≥7 mg/g dry weight (TD high only) and nutritional, genetic, infectious, or autoimmune anemia. DISC-0974 was administered subcutaneously at a dose of 50 mg once monthly for a total of 6 doses. Dose escalation to 75 mg was required for inadequate or loss of response. Primary endpoints included evaluating hematologic response defined for TD low and TD high as TI during any 16- and 12-week consecutive period, respectively, and for nTD as a mean hemoglobin increase of ≥1.5 g/dL from baseline for at least 12 weeks. Secondary endpoints included PK/PD markers of iron regulation and safety assessments. Data were summarized using descriptive statistics. Results As of 01 July 2025, enrollment of the exploratory cohort of momelotinib was complete (n=10). Baseline hepcidin values in the exploratory cohort were similar (mean (SD) of 83.6 (62.8) ng/mL) to baseline hepcidin values from the DISC-0974 Phase 1b study (mean (SD) of 85.8 (71.0) ng/mL, n=35), and sustained hepcidin reduction was observed after DISC-0974 dosing. Early hematologic responses observed after 1 to 3 doses in the exploratory cohort were comparable to those reported in the Phase 1b study (Gangat et al, Blood 2024;144(Suppl1):657). Based on these initial data, the protocol was amended to allow concomitant momelotinib or pacritinib in all cohorts. Preliminary results, including baseline characteristics, PD, and hematologic responses across all cohorts, will be presented.

Abstract Background Myeloproliferative neoplasms (MPNs) can progress from chronic phase to accelerated or blast phase (MPN-AP/BP), a transition with poor prognosis and limited treatment options. While some abnormalities have been described, the genomic and clonal drivers of transformation remain poorly defined. We characterized mutational and structural alterations in MPN-AP/BP, leveraging paired samples to trace clonal evolution. Methods We profiled 186 samples from 160 individuals, including 159 MPN-AP/BP and 27 chronic-phase MPN samples (26 MF, 1 PV), using targeted sequencing of a 588 gene panel (mean depth: 709x). Paired pre- and post-transformation samples were available for 26 patients (n= 52). A consensus pipeline was used to detect somatic mutations, copy number variations (CNVs), and copy-neutral loss of heterozygosity (cnLOH). Clinical cytogenetic data were integrated when available. Single-cell validation is ongoing. Results Genomic complexity was widespread: 99% of patients harbored ≥1 oncogenic mutation (median 4; range 1–10). In total, 859 mutations were identified, most commonly in JAK2 (68%), ASXL1 (28%), TET2 (26%), SRSF2 (24%), TP53 (22%), and RUNX1 (22%). 684 structural alterations were identified in 86% of patients (median 3; range 1-20), including arm-level (22.5%), segmental (>5 Mb; 60%), and focal (<2 Mb; 9%) alterations. Recurrent events included 9p cnLOH (16%), del(5q) (13%), del(17p) (10%), and focal deletion of 21q22.12 involving RUNX1 (10%). Complex karyotypes (≥3 abnormalities) were observed in 55% of patients. Biallelic mutations accounted for 21% (183/859) of mutations, affecting 58% of patients across 21 genes, most frequently JAK2 V617F (28%), TP53 (17%) and TET2 (14%). Patients with biallelic mutations in these genes had significantly higher blast percentages compared to those with monoallelic mutations (p<0.05), highlighting an association with aggressive disease. In 26 patients with longitudinal samples (chronic phase MPN and MPN-AP/BP), 87% (125/144) of mutations were already detectable during the chronic phase, on average more than 7 years prior to transformation. Only 11% (16/144) of mutations were newly acquired, including additional RUNX1 and TP53 hits, or structural changes that converted pre-existing JAK2 V617F and TP53 R248Q mutations from monoallelic to biallelic via 9p cnLOH or 17p loss, respectively. These findings suggest transformation is often driven by outgrowth of pre-existing high-risk clones, indicating that these clones likely have a competitive advantage and that the mutations within these clones have a cooperative biological interaction which underlies this competitive advantage. To investigate this hypothesis, we examined whether patterns of recurrent co-mutations were identifiable in this cohort. We identified recurrent co-occurring mutations in SRSF2-IDH2, ASXL1-SRSF2, and ASXL1-EZH2, which were enriched at transformation (p < 0.05; Fisher exact test). Importantly, presence of these co-mutations was consistently associated with a higher transformation risk in two independent cohorts of MF patients from Mayo Clinic (n= 405) and University of Florence (n= 518). Clonal architecture analysis revealed that these co-mutations frequently arose within the same malignant clone: 100% for SRSF2-IDH2, 80% for ASXL1-SRSF2, and 85% for ASXL1-EZH2, and are often within the dominant clone. Prior studies have demonstrated mechanistic interplay between SRSF2 and IDH2 (Yoshimi et al.), as well as ASXL1 and SRSF2 (Sui et al.) mutations in myeloid malignancies. We assessed functional synergy of ASXL1-EZH2 using a murine model and identified that dual deletion caused a rapidly fatal myeloid neoplasm with shorter survival than single-gene loss. These results reinforce that functional synergy emerges within a shared cellular context, supporting clonal co-dependence as a driver of progression. Single-cell RNA sequencing of ASXL1-EZH2 mutant cases is ongoing and will be presented. Conclusions Transformation to MPN-AP/BP is driven by gradual clonal remodeling and expansion of pre-existing high-risk abnormalities. Biallelic and multi-hit alterations in TP53, JAK2, TET2, and RUNX1 promote clonal dominance and blast progression. Recurrent co-mutations such as IDH2-SRSF2 and ASXL1-EZH2 arise within the same clone, exhibit functional synergy, and are linked to poor outcomes. These findings support the clinical utility of early clonal and co-mutational profiling to guide risk-adapted intervention.

Abstract Background and Significance: Polycythemia vera (PV) is a myeloproliferative neoplasm associated with pathologic erythrocytosis, most often driven by somatic mutations in the JAK2 gene. A key treatment goal is maintaining hematocrit (HCT) below 45% to reduce thromboembolic complications. Current standard of care for patients diagnosed with PV, including phlebotomy (PHL) and cytoreductive therapies (CRT), can be burdensome, may lead to intolerable adverse effects, and often are associated with symptoms of iron deficiency. DISC-3405 is an investigational, novel, humanized immunoglobulin (Ig)G1 monoclonal antibody that targets transmembrane serine protease 6 (TMPRSS6, also known as matriptase 2) to stimulate endogenous production of hepcidin, a peptide hormone secreted by hepatocytes and the key regulator of iron homeostasis. In a randomized, placebo-controlled study in healthy volunteers (DISC-3405-101), DISC-3405 administered subcutaneously at doses between 37.5-300 mg was well-tolerated, resulted in dose-dependent pharmacokinetic (PK) profiles, significantly increased hepcidin production with corresponding reductions in serum iron levels, and reduced HCT (Liu et al, EHA 2025, PS2207). DISC-3405 is being developed as a potential treatment for patients with PV requiring HCT reduction, regardless of baseline risk or concurrent CRT. Study Design and Methods: This is a multi-center, open-label, 52-week Phase 2 study enrolling up to 20 patients with PV in the United States to assess the safety, tolerability, PK, pharmacodynamics (PD), and therapeutic effect of DISC-3405 on PV disease control as evidenced by HCT reduction and PHL requirements. After an observation period of 4-12 weeks, participants will be treated and followed for 52 weeks and dosed up to 300 mg every 2 weeks. After 52 weeks, participants can continue in an optional 2-year continuation phase where long-term safety and efficacy will continue to be assessed. The main efficacy endpoints of the study include the proportion of participants achieving therapeutic response, defined as absence of PHL eligibility; number of PHLs during the treatment period; and proportion of participants with HCT values <45% throughout the study. PHL eligibility is defined as (1) HCT ≥45% and ≥3% (absolute change) of pre-treatment values or (2) HCT >48%. Eligible participants include adults 18 or older who meet the 2022 World Health Organization diagnostic criteria for PV. Clinically acceptable laboratory values include HCT <45% prior to Day 1 (dosing) or HCT <48% if followed by a PHL within 2 weeks prior to first dose of study drug, white blood cells 4000/μL to 20,000/μL (inclusive), and platelets 100,000/μL to 1,000,000/μL (inclusive). Participants should have at least 3 PHL in 26 weeks or 5 PHL in the 52 weeks prior to screening, and at least 1 PHL within 12 weeks prior to screening. Participants receiving CRT must have been on the therapy for at least 6 months and on a stable PV treatment regimen, including hydroxyurea, interferon, or ruxolitinib, for at least 2 months. Participants treated with only PHL must have stopped CRT 6 months before screening. Key exclusion criteria include participants that require PHL at HCT levels <45%, clinically significant thrombosis within 2 months prior to study treatment, active or chronic bleeding, estimated glomerular filtration rate of <30 mL/min/1.73 m2, and history of invasive malignancies within the last 5 years, except localized cured prostate cancer and cervical cancer, or other malignancies deemed acceptable in discussion with the Sponsor. The study will enroll participants from approximately 15-20 sites in the United States. Additional details can be found at https://clinicaltrials.gov/study/NCT06985147.

Abstract Introduction: While the incidence of multiple myeloma (MM) is 2-3 fold higher in Black compared to white individuals, the impact of racial differences on treatment outcomes remains unclear due to the confounding effect of socioeconomic barriers and disparities in access to effective therapies and clinical trials. In this study, we explored the relationship between race, social deprivation, and outcomes in newly diagnosed MM (NDMM) patients (pts) receiving modern therapies with triplet or quadruplet regimens. Methods: Pts with NDMM diagnosis, who received first line treatment between 2015-2025, and had data available on response and survival outcomes were identified through the ASH Research Collaborative MM Data Hub (a real-world database with pts across 11 U.S. institutions). Data on patient demographics (age, race, ethnicity, sex), disease risk status (ISS/R-ISS stage, FISH cytogenetics), treatment regimens (triplet vs quadruplet, anti CD38 monoclonal antibody-based vs not), and disparity measures were abstracted from electronic medical records. Race and ethnicity were self-reported by pts. Social Deprivation Index (SDI) score was calculated based on ZIP code, where higher scores reflect greater deprivation. Progression free survival (PFS) was defined as time from start of treatment until progression or death. Overall survival (OS) was defined as time from start of treatment until death from any cause. Kaplan-Meier methods were used to compare PFS and OS between groups, and cox regression models with log-rank tests were used to evaluate the influence of various factors on outcomes. Results: A total of 1,743 patients were identified; 1,116 (63.8%) identified as non-Hispanic White (NHW) and 402 (23.3%) as non-Hispanic Black (NHB) [note: 85 pts (4.9%) were Hispanic but not included due to limited numbers]. The median age (years) at the start of treatment (61.8 vs. 65.6) was lower for NHB compared to NHW pts (p<0.001). The proportion of females was greater in NHBthan NHW pts(53.5% vs. 41.1%, p=0.0016). Median SDI scores were significantly higher for NHBcompared to NHW pts (68.4 vs. 39.4; respectively; p<0.001), reflecting significantly higher rates of social deprivation. While NHB ptshad higher rates of advanced stage disease (ISS III 26.9% vs. 20.9%, p=0.009), lower rates of autologous stem cell transplant (ASCT) (56.7% vs. 63.6%, p=0.014), and longer median time from treatment initiation to ASCT (6.5 vs. 5.9 months, p=0.043), the rates of standard risk cytogenetics on FISH (72.3% vs. 77.6%), and utilization of CD38 monoclonal antibody-based regimen (29.9% vs. 27.7%) were similar between the two groups. Best response after treatment initiation was similar between the NHB and NHW pts (p=0.12) with complete response 45.7% vs. 52.6% and very good partial response 37.3% vs 34.7%; respectively. However, time to best response (months) was longer in NHB pts (7.2 vs. 6.5, p=0.005). Median follow-up for OS was 4.2 years (95% CI 3.9-4.4; 182 OS events) and for PFS was 1.3 years (95% CI: 1.1-1.6; 302 PFS events) across the two groups. Unadjusted PFS was similar for NHB vs NHW pts (HR=1.05, 95% CI: 0.81- 1.36; median: 5.0 vs 4.9 years; 3-year PFS: 66% vs. 71%). Similarly, unadjusted OS was not significantly different in NHB vs NHW pts (HR=1.12, 95% CI: 0.79-1.59; 5-year OS: 86.4% vs 85.6%). Higher SDI scores were significantly associated with worse OS (HR=1.07, 95% CI: 1.02-1.12; p=0.0065) but not PFS (HR=0.99, 95% CI: 0.95-1.02; p=0.46). Though not statistically significant, univariate analyses indicated a greater impact of high SDI scores (≥70, 75th percentile across all pts) in NHW (HR=1.45, p=0.068) than in NHB pts (HR=0.78, p=0.35) for OS. Adjusting for age, sex, ISS stage, and SDI, NHB did not appear to have worse OS (HR=0.75, 95% CI: 0.35-1.60; p=0.46) or PFS (HR=1.23, 95% CI: 0.78-1.96; p=0.37) compared to NHW pts. Conclusions: Our study represents a diverse population enriched for pts who received modern day standard of care frontline therapies including triplet and quadruplet regimens with or without ASCT. Based on SDI scores, higher social deprivation levels were seen in NHB compared to NHW pts without a difference in outcomes between the two races. Our analysis supports that higher social deprivation among different races rather than race and ethnicity alone may drive differential outcomes and adjustment for factors like SDI is critical to interpretation of survival outcomes by race.