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Abstract Introduction Ph-like B-ALL is a poor-risk B-ALL subtype defined by gene expression signatures that resemble the BCR::ABL1-associated transcriptional program in the absence of the BCR-ABL1 oncoprotein. Recent studies have demonstrated that up to 80% of Ph-like B-ALLs have recurrent gene fusions involving cytokine receptors or tyrosine kinases that can be identified via cytogenetics, fluorescence in situ hybridization (FISH) or RNA sequencing. However, the inability to rapidly and accurately identify these alterations in the clinical setting is a major impediment to developing therapeutic strategies that may have efficacy in this B-ALL subtype. Here we used 88 patient (pt) samples to validate a rapid, streamlined clinical WGS assay (ChromoSeq) for B-ALL and assessed the diagnostic yield for Ph-like-associated SVs in 136 pts enrolled in the Alliance A041501 clinical trial. Methods ChromoSeq is a clinical WGS assay for hematologic malignancies that uses rapid laboratory workflows and focused analysis methods to identify clinically relevant SVs, copy number alterations and gene-level mutations. We updated the ChromoSeq pipeline for use in B-ALL pts and validated it using 88 retrospective B-ALL samples (80 adult/young adult and 8 pediatric from Washington University School of Medicine and St. Louis Children's Hospital), 54 of which were analyzed via RNAseq for gene fusions and a 6-gene Ph-like B-ALL signature (CA6, SPATS2L, MUC4, JCHAIN, BMPR1B, ADGRF1, NRXN3 and CRLF2). The “ChromoSeqV2” assay was then used to analyze 136 pretreatment blood or bone marrow samples from the Alliance A041501 (trial NCT03150693). These results were compared to data from RNAseq obtained for research purposes (N=35), clinical cytogenetics (N=69) and Ph-like classification via low-density microarray (LDA) card analysis (all pts). Results ChromoSeqV2 was validated in a CLIA-licensed setting using cohort of 88 retrospective B-ALL samples, 45 of which had ICC and WHO class-defining SVs based on G-banded karyotyping, FISH or RNAseq. ChromoSeqV2 detected 100% of the non-Ph-like SVs (37/37), including BCR::ABL1 (N=20), KMT2Ar (N=9), ETV6::RUNX1 (N=3), TCF3::PBX1 (N=1), and rearrangements involving MYC (N=2) or MEF2D (N=2). Fifteen patients met criteria for Ph-like B-ALL via cytogenetics or RNAseq either due to rearrangements of CRLF2 (N=5), JAK2 (N=2) or ABL2 (N=1) or high expression of a 6-gene Ph-like signature (N=7). ChromoSeqV2 detected a Ph-like SV in 93% of these cases (14/15) with 100% specificity in samples negative by RNAseq (N=23). ChromoSeqV2 was then used to profile 136 samples from the Alliance A041501 trial, where it identified ICC and WHO class-defining SVs in 87 pts (64%; 95% CI: 55-72%), including Ph-like SVs (56/136, 41%), KMT2A rearrangements (N=5), TCF3::PBX1 (N=3) and SVs involving MYC (N=3), MEF2D (N=2), DUX4 (N=2), and ZNF384 (N=1). Ph-like SVs were dominated by CRLF2 rearrangements (N=45) and included SVs involving EPOR (N=4), JAK2 (N=3), ABL1/ABL2 (N=2) and PDGFRB (N=1). IGH was the most common CRLF2 partner (N=32), followed by P2RY8::CRLF2 (N=7) and other genes (N=5). Multiple CRLF2 SVs were detected in 4 pts, and 33% (15/45) of pts with a CRLF2 rearrangement had a co-occurring CRLF2 gene mutation. The yield of ChromoSeqV2 for SVs in pts with the Ph-like expression signature via LDA card analysis was 66% (54/82; 95% CI 55%-76%) compared to 24% (11/45; 95% CI 13%-40%) by cytogenetics when these studies were successful and 70% (12/17; 95% CI 44%-90%) vs RNAseq in pts with available data. The sensitivity of ChromoSeqV2 for Ph-like SVs identified by either cytogenetics, FISH or RNAseq was 100% (21/21; 95% CI 84%-100%) and the positive predictive value of Ph-like SVs for the Ph-like expression signature by the LDA card assay was 96% (54/56; 95% CI 88%-99%). Conclusions Genomic assessment of 136 B-ALL pts from the Alliance A041501 trial using the ChromoSeqV2 rapid clinical WGS assay was 100% sensitive for Ph-like SVs identified by other molecular methods and had a 96% PPV for the Ph-like expression signature via LDA card analysis. The diagnostic yield of SV pts with the Ph-like signature was 66% using ChromoSeqV2, which was similar to RNAseq and superior to cytogenetics. These results demonstrate that ChromoSeqV2 is an effective approach for identifying potentially targetable rearrangements in B-ALL pts suspected of having the Ph-like phenotype. Support: U10CA180821, U10CA180882; . Servier; Pfizer.

Abstract Background: Recent approvals and clinical trials have established covalent BTK inhibitors (BTKis), including ibrutinib, acalabrutinib, and zanubrutinib, as effective agents for the treatment of mantle cell lymphoma. Multiple BTKi-based regimens are recommended by experts and clinical guidelines in both the first-line and later-line settings. Additional approvals of the noncovalent BTKi pirtobrutinib and multiple CAR T-cell therapies have also advanced the management of patients who have progressed on covalent BTKi therapy. In light of these developments in treatment strategies for mantle cell lymphoma (MCL), this study compares trends in treatment choice among experts and healthcare professionals (HCPs) in an online treatment decision support tool. Methods: An online decision support tool, developed with 5 US-based experts in MCL, was launched in April 2023 and updated in April 2025. The tool provided treatment recommendations for various clinical scenarios involving newly diagnosed (ND) or relapsed/refractory (R/R) MCL, incorporating factors such as age, fitness, previous therapies, and response duration. HCPs entered specific patient characteristics along with their intended treatment choice. The tool then displayed expert recommendations for that scenario, and HCPs were asked whether these recommendations influenced their treatment decision. HCP-entered data and expert recommendations were analyzed to identify common trends and divergence in current BTKi therapy use. Results: The 2023 online tool was used by 119 HCPs who entered 148 patient scenarios, and the 2025 online tool was used by 69 HCPs who entered 96 patient scenarios. In 2023, for patients with ND MCL who had later-stage disease or were not eligible for radiation therapy (n = 75), 64% of expert-recommended treatments included BTKis, with the ECHO and TRIANGLE regimens representing 12% and 17% of recommendations, respectively. In 2025, 81% of expert recommendations were BTKi-based regimens, with ≥3 experts recommending a BTKi regimen in 66 of 67 unique ND case scenarios. The ECHO and TRIANGLE regimen each represented 28% to 29% of expert recommendations. In addition, 51% of recommendations for patients with 17p deletions or TP53 mutations consisted of the BOVen regimen. The percentage of HCPs who indicated that they were considering a BTKi-based regimen in the setting of ND MCL was 17% (13 of 75 ND cases) in 2023 and 66% (44 of 67 ND cases) in 2025. The use of both the ECHO and TRIANGLE regimens by HCPs increased from 5% and 4%, respectively, in 2023 to 19% for each in 2025. In 2025, 6% of HCPs considered the BOVen regimen for patients with TP53 mutation (n = 17). In 2023 and 2025, approximately 50% of the HCP-entered patient cases for previously treated MCL had not received a BTKi (n = 48 and n = 18, respectively). For these scenarios, 94% and 98% of expert recommendations consisted of covalent BTKis in 2023 and 2025, respectively. HCPs selected covalent BTKis for 68% of cases in 2023 and 89% of cases in 2025. For patients with R/R MCL previously treated with a BTKi, CAR T-cell therapy represented 36% of expert recommendations in 2023 (23 scenarios) and 60% in 2025 (18 scenarios). By contrast, 4% and 11% of HCPs considered CAR T-cell therapy for these patients in 2023 and 2025, respectively. For HCPs reporting on the tool's clinical impact (n = 96), 35% indicated expert recommendations changed their intended therapy, 41% stated their treatment plan matched the recommendations, 10% cited barriers to implementing recommendations, and 14% remained undecided on optimal treatment. Conclusions:This analysis highlights the ongoing adoption of expert-recommended treatments into real-world clinical practice. Our data suggest that expert and HCP use of BTKi therapy in the ND MCL setting has increased in recent years. In R/R MCL, CAR T-cell therapy appears to be considered infrequently by HCPs. Barriers to implementation of expert recommendations warrant further investigation. Enhanced decision support tools and targeted educational initiatives could help increase the use of expert treatment recommendations and potentially improve patient outcomes.

Abstract Introduction: The prognosis of patients (pts) with histological transformation (HT) of Waldenström macroglobulinemia (WM) remains dismal with standard chemoimmunotherapy. CD19-targeted chimeric antigen receptor T-cell therapies (CAR-T) can lead to durable responses in relapsed/refractory (R/R) large B-cell lymphoma (LBCL) and are approved in the second or third line settings. Pts with HT-WM were largely excluded from CAR-T trials. We previously reported high response rates in a series of 23 pts. The aim of the present study was to evaluate a larger cohort of pts with R/R HT-WM treated with CAR-T with a longer follow-up. Methods: We performed a multicenter retrospective study of pts with biopsy-proven transformed WM/lymphoplasmacytic lymphoma treated with CAR-T in the French DESCAR-T registry (NCT04328298), 4 centers from ECWM and 4 US centers. This study includes updated data from previously published cases (Durot et al, Blood, 2024). Responses were assessed according to the Lugano 2014 criteria. Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were graded according to the ASTCT 2019 consensus criteria. Hematological toxicity and infections were graded according to the NCI CTCAE (version 5.0). Progression-free survival (PFS) and overall survival (OS) were calculated from the date of CAR-T infusion and estimated using the Kaplan-Meier method. Results: 50 pts were included (39 from DESCAR-T centers, 7 from US centers and 4 from ECWM centers). Median age was 60 (range: 32-72) and 68 (range: 42-82) years at WM diagnosis and CAR-T infusion, respectively. MYD88L265P and CXCR4 mutations were present in 79% (23/29) and 15% (2/13) of patients with available data, respectively. The median time from WM to HT diagnosis was 5.3 years (range: 0-32). Median prior lines of therapy was 1 (range: 0-9) for WM and 2 for HT (range: 0-4). Twenty (40%) pts previously received a BTK inhibitor for WM or HT, 12 (24%) underwent prior autologous SCT and 1 pt allogeneic SCT. 40% of pts presented primary refractory disease and 44% were refractory to last treatment before CAR-T. 40 pts (80%) received bridging therapy, of whom 17 (44%) responded (7 complete responses (CR)). 35 (70%), 10 (20%), and 5 (10%) pts received axicabtagene ciloleucel (axi-cel), tisagenlecleucel (tisa-cel), and lisocabtagene maraleucel (liso-cel), respectively. The best overall response rate (ORR) was 94%, with 44 (88%) pts reaching CR. With a median follow-up of 25.7 months (range: 1-69) from CAR-T infusion, the median PFS was 1.2 years (95% CI: 0.5-4.5) and median OS was 4.2 years (95% CI: 1.2-not reached). Median duration of response was 1.5 years (95% CI: 0.4-4.4), with a median of 4 years (95% CI: 1.5-NR) for pts still in CR at 6 months after CAR-T. 22 pts experienced relapse/progression after CAR-T, 19 related to LBCL and 3 to WM. Median survival after relapse was 7.9 months (95% CI: 3.8-25.3). At LBCL relapse after CAR-T, salvage therapy consisted of CD20xCD3 bispecific antibodies for 9 pts, lenalidomide +/- anti-CD20 or anti-CD19 antibody for 6 pts, and BTKi for 3 pts. Among 19 pts who died, 14 (74%) were due to progressive disease and 5 (26%) from infections. 37 (76%) pts experienced CRS, including 2 (4%) grade 3 events, and 22 (45%) had ICANS, with 2 (4%) ≥ grade 3 events. 17 (35%) pts presented infections, including 12 ≥ grade 3. 21 (43%) pts developed ≥ grade 3 prolonged cytopenias (ie, not resolved within 30 days post infusion). CNS involvement due to LBCL was present in 11 pts (22%) at the time of CAR-T. 6 of them had ICANS, with 1 grade 4. The best ORR was 91% (best CR 91%). Only 1 patient did not obtain a response, with stable disease at 1 month and progression at 3 months. The median PFS was 1.2 year (95% CI: 0.2-NR) and median OS was NR (95% CI: 0.5-NR). On univariate analysis, only elevated LDH was correlated with worse PFS (HR 2.5, p=0.04) and OS (HR 3.3, p=0.04). Other variables, including number of prior lines of therapy, MYD88 mutation status, primary refractory disease, refractory to last treatment, CNS involvement before CAR-T, response after bridging therapy and type of CAR-T received, were not associated with inferior PFS or OS. Conclusion: This cohort represents the largest series of pts with transformed WM treated with anti-CD19 CAR-T. We confirm the high efficacy previously reported with an acceptable safety profile, including for pts with CNS involvement due to LBCL at CAR-T infusion.

Abstract Introduction Blast transformation (BT) in CMML occurs in 15-30% of patients (pts) with a median overall survival (OS) <6 months (mo). While clonal evolution can be observed, biological mechanisms of BT remain unknown for many pts. Using paired samples from chronic phase (CP) and at BT, this study defines the cytogenetic and molecular landscape of BT-CMML. Methods BT-CMML pts from Mayo Clinic (n=153, 31%), MD Anderson (n=195, 40%), and 7 centers of the Groupe Francophone des Myélodysplasies (n=145, 29%) were included after IRB approval. ICC 2022 criteria defined CMML and AML. Pt data were collected at initial diagnosis or referral at CP and again at BT. Clonal dominance was inferred from a natural log-fold difference of mutation variant allele fractions (VAF). OS was censored at allogeneic stem cell transplant (alloSCT). Single-cell multiomic analyses used the Tapestri platform (Mission Bio). Statistics used R. Results Among 1,883 cases of CMML with a median follow up of 96 mo, 493 (26%) underwent BT. The median age at CP and BT was 69 and 71 years, respectively. BT-CMML pts were predominantly male (69%) and had proliferative CMML (53%) or CMML-1 (69%) in CP; 39% and 33% were considered high-risk by CPSS-Mol and BLAST-Mol criteria, respectively. The median time to BT was 16 mo (interquartile range 7-35 mo) and was not different in males vs females (p=0.60). Compared to their CP parameters (p<0.001 each), pts at BT had lower median hemoglobin (10.8 vs 9.2 g/dL) and platelets (100 vs 44 x109/L) but higher leukocytes (13.9 vs 16.3 x109/L), peripheral blasts (0% vs 14%), and bone marrow blasts (6% vs 32%). Blasts exhibited mostly monocytic (57%) or immature myeloid (40%) differentiation. Abnormal karyotypes (AK) were more prevalent at BT (25% vs 62%, p<0.001). Among 318 pts with paired karyotype data, 221 (69%) had a normal karyotype (NK) in CP, of which 123 (56%) remained normal at BT and 98 (44%) acquired new abnormalities. Conversely, 97 (31%) pts had an AK in CP, of which 67 (69%) acquired abnormalities or increased clonal metaphases (6%), 23 (24%) remained stable, and 7 (7%) reverted to a NK at BT. Overall, 46% acquired and 8% lost a clonal cytogenetic abnormality, while 46% remained unchanged. Numeric (37%) and structural (30%) changes were most common. Complex (12% vs 3%) and monosomal (5% vs 2%) karyotypes were more frequent at BT than in CP. Only 6 (2%) pts acquired an AML-defining rearrangement at BT. Mutational data were available for 248 paired cases. The number of somatic mutations was higher at BT (median 3 vs 4, p<0.001). Mutations in RUNX1 (27% vs 39%), NRAS (23% vs 33%), KRAS (11% vs 17%), FLT3 (6% vs 15%), NPM1 (0% vs 11%), IDH2 (5% vs 11%), and CEBPA (3% vs 10%) were more frequent at BT (all p<0.05). At BT, the average VAF of the dominant clone increased in 32%, decreased in 35%, and remained unchanged (delta ≤5%) in 33%. The most frequent dominant clones both in CP and at BT had mutations in TET2 (8% vs 4%) or co-dominant mutations involving SRSF2-TET2 (7% vs 3%). Mutational clonal evolution was observed in 72%, with mutations gained in 45% and lost from the dominant clone in 19%. The most gained mutations at BT were in NRAS (15%) and RUNX1 (13%). Single cell proteogenomic analyses in 4 selected CP and BT pts shed light on the impact of NRAS and RUNX1 mutations on clonal hierarchies and differentiation. Among 196 fully evaluable cases, a new cytogenetic and/or molecular aberration was uniquely gained in 106 (54%) cases and lost in 9 (5%), with 40 (20%) both gaining and losing a genetic alteration. Forty-one (21%) patients had no identifiable genetic change between CP and BT, suggesting driver alterations outside of that detected by routine analyses. Median OS was 31 mo from CMML diagnosis and 5.6 mo from BT. Compared to supportive care, treatment in CP did not prolong median time to BT (14 vs 17 mo, p=0.91) or OS (35 vs 29 mo, p=0.05), regardless of intensity. After BT, median OS was 1.2 mo with supportive care (n=83), 8.7 mo with a hypomethylating agent (HMA, n=39), 10 mo with HMA plus venetoclax (n=37), 7.8 mo with chemotherapy (n=91), and 31 mo in pts who underwent alloSCT (n=57). Conclusions In this large BT-CMML cohort, cytogenetic (46% gained, 8% lost) or mutational (45% gained, 19% lost) driver events were identified in 79% of pts, with 21% having no identifiable changes by conventional testing. Whole genome/transcriptome analyses are underway in this subgroup to identify novel drivers of BT.

Abstract INTRODUCTION: Warm autoimmune hemolytic anemia (wAIHA) is a rare, autoimmune-mediated hematologic disorder associated with significant morbidity and mortality and may occur as a primary condition or secondary to an underlying disorder. It is the most common subtype of autoimmune hemolytic anemia (AIHA), accounting for 75-80% of AIHA cases. Older adults with wAIHA are particularly vulnerable, as they often have multiple comorbidities and are already at elevated risk of death. This study aimed to assess mortality associated with wAIHA. METHODS: Adults with wAIHA (wAIHA cohort) and without AIHA (non-AIHA cohort) were identified from the 100% Medicare Fee-for-Service database (10/01/2019–12/31/2023). Evidence of wAIHA was defined as one of the following: 1) a primary wAIHA diagnosis (International Classification of Diseases, Tenth Revision, Clinical Modification [ICD-10-CM]: D59.11) in the inpatient setting (first instance of wAIHA diagnosis defined the index date), 2) ≥2 wAIHA diagnosis in any setting ≥30 days apart (second instance of wAIHA diagnosis defined the index date), or 3) a wAIHA diagnosis preceded ≥30 days by any AIHA diagnosis (ICD-10-CM: D59.10, D59.19, D59.8, D59.9; first instance of wAIHA diagnosis defined the index date). Patients in the wAIHA cohort were excluded if they had a diagnosis for cold or mixed-type AIHA (ICD-10-CM: D59.12, D59.13) during the baseline period (12 months before index). The non-AIHA cohort had no diagnoses for any AIHA during the study period; a random index date during continuous Medicare eligibility was selected and patients were matched 1:10 with the wAIHA cohort based on age on index date. Using overlap weighting, age-matched cohorts were further weighted on sex, race, region, index year, and baseline comorbidities associated with mortality, excluding conditions defining secondary wAIHA. Mortality during the follow-up period was evaluated between the weighted cohorts using the Kaplan-Meier method and Cox proportional hazard models. Patients whose death was not observed were censored at the earlier of the end of continuous Medicare eligibility or data availability. RESULTS: 3,112 and 31,120 patients were included in the wAIHA and non-AIHA cohorts, respectively. After weighting, among the wAIHA vs non-AIHA cohorts, mean [standard deviation; SD] age was 74.4 [11.6] vs 74.6 [11.2] years, the proportion of female were 56.1% vs 56.1%, mean [SD] Quan-CCI without secondary wAIHA-defining conditions was 1.9 [2.0] vs 1.9 [2.1], and mean [SD] follow-up time was 17.2 [11.7] vs 14.9 [11.4] months, respectively. In addition, 53.7% of the wAIHA cohort had secondary wAIHA. The most common secondary wAIHA-defining conditions were autoimmune and inflammatory diseases (wAIHA cohort: 27.8%; non-AIHA cohort: 11.0%), hematologic and lymphoproliferative disorders (wAIHA cohort: 23.8%; non-AIHA cohort: 1.3%), and solid tumors (wAIHA cohort: 16.8%; non-AIHA cohort: 12.6%). The most common comorbidities for both cohorts were hypertension (wAIHA cohort: 77.4%; non-AIHA cohort: 78.3%) and dyslipidemia (wAIHA cohort: 72.2%; non-AIHA cohort: 74.7%). Survival rates in the wAIHA and non-AIHA cohorts were 80.3% vs 84.0% at 12 months, 70.7% vs 77.6% at 24 months, and 63.7% vs 73.1% at 36 months, respectively (all p<0.001). Patients with wAIHA were at 20%, 27%, and 30% higher risk of death at 12, 24, and 36 months, respectively, compared to patients without AIHA (hazard ratios: 1.20, 1.27, and 1.30; all p<0.001). CONCLUSIONS: This large retrospective study is the first to assess real-world incremental mortality associated with wAIHA among Medicare beneficiaries. Patients with wAIHA were at significantly greater risk of death following the initial diagnosis. These results may point to potential gaps in early diagnosis and effective disease management, which could contribute to increased mortality. Future research should focus on specific subgroups within the wAIHA cohort to identify differences in mortality as well as characteristics that may be associated with death.

Abstract Introduction: The real-world outcomes in patients (pts) with PCALCL in the era of targeted therapies like Brentuximab Vedotin (BV) is not well defined due to lack of large multicenter studies. We conducted a multicenter retrospective analysis (RWA) to assess patient and disease characteristics, treatment patterns, survival outcomes and impact of novel therapies in this rare type of cutaneous T cell lymphoma (CTCL). Methods: The analysis included 167 adult (≥18 years) patients (pts) with PCALCL across 9 academic institutions in the United States diagnosed between 01/2012 to 06/2022. The study was approved by the Institutional Review Boards at the respective sites. Demographic and disease factors were summarized using descriptive statistics. Overall survival (OS) and relapse-free survival (RFS) were estimated using Kaplan-Meier method and compared via log rank tests. Prognostic models included factors such as age, sex, race, performance status (PS), disease stage, type of initial lesion, presence of B symptoms, previous history of lymphomatoid papulosis and prior transplant. Prognostic factors for survival were assessed using both univariable and multivariable Cox proportional hazard models. Results: The median age at diagnosis was 61 (range 18-93) years. The majority of pts were male (55%) and white (82%), with good PS as indicated by an ECOG 0-1 (71%). The initial skin presentation consisted of tumors in 62% of the pts, while 34% presented with plaques or patches. Notably, no pts presented with erythroderma. Most pts underwent PET scan for staging at initial diagnosis (83%) with the majority having early-stage (IA-IIA) disease (86%). Furthermore, palpable lymph nodes (11%) and the presence of B symptoms (4%) were rare at diagnosis, and no pts had blood involvement. The most common sites of involvement were extremities (33%) followed by the head and neck (H&N) and trunk (31% each). Immunophenotyping revealed CD4 positivity in 59% of pts and CD8 positivity in 25%. The T cell receptor (TCR) rearrangement was positive in 28% of pts, though it was not completed in the majority of cases (72%). Most common initial treatments included localized radiation (61%) and surgical excision (19%). A small subset of pts received frontline systemic chemotherapy regimens such as cytotoxic chemotherapy (11%), BV (8%) and oral methotrexate (MTX) (8%). Approximately 7% of the pts had a stem cell transplant. Overall response rate (ORR) for radiation, oral MTX, BV and cytotoxic chemotherapy were 78% (CR:78% 74/100), 42% (CR:63% 6/12) and 39% (CR:67% 6/12), 89% (CR: 88% 15/18) respectively. At a median follow-up of 3.8 years (range 0.04-10.23), the median RFS and OS were 2.7 years (95% CI:1.86, 3.43) and 12 years (95% CI:10.6- NA) respectively. The estimated 3- and 5-year RFS are 46% (95% CI:0.38, 0.55) and 37% (95% CI:0.28, 0.46) respectively. The estimated 3- and 5-year OS were 89% (95% CI:0.82, 0.93) and 82% (95% CI:0.73, 0.88) respectively. At the time of the last follow-up, 79% were alive, while 21% were deceased. The cause of death (COD) was unknown in 50% of the cases and only 10% (3/of deaths were attributed to lymphoma. Other known CODs included infection (20%) and second malignancies 7%. On univariate analysis (UVA), age (p=.007), female sex (p=.04), ECOG PS 1-2 compared to 0 (p=.007) and prior transplant (p=.009) predicted for worse RFS. On multivariate analysis (MVA), only ECOG PS 1-2 (HR 2.31, 95 CI:1.06, 1.18, p=.009) and prior transplant (HR 5.38, 95 CI:2.30, 12.57, p=.0001) had a significant impact on RFS. Age and presence of B symptoms were strong predictors of OS on both UVA (age p=<.0001; B symptoms p=<.0001) and MVA (age: HR 1.12, 95 CI:1.06, 1.18, p=<.0001; B symptoms: HR 16.48, 95 CI: 3.69, 73.60, p=.0002). However, the impact of B symptoms should be interpreted with caution as only 4% of pts presented with this at baseline. On UVA, each one-year increase in age was associated with an 8.5% rise in the risk of death. ECOG PS 1-2 was associated with worse OS on univariate analysis (HR 2.62, 95% CI 0.99, 6.93, p=.05), but was not significant on MVA (HR 1.05, 95% CI 0.368, 2.974, p=.93). Conclusions: In this large RWA of PCALCL, excellent long-term survival was observed with predominantly skin directed frontline therapies. The use of systemic treatments, including BV, was infrequent as first line therapy. Older age and poor PS were significant predictors for reduced survival.

Abstract Background Previous studies in aggressive B-cell lymphoma demonstrate that patients with shorter diagnosis-to-treatment intervals (DTI) represent those with higher risk disease. This suggests that patients enrolled in clinical trials may carry a selection bias as they often have longer DTI than patients in the general population. This has important implications for clinical research design and the generalizability of clinical trials in aggressive lymphomas. However, the prognostic implications of DTI have not been evaluated in peripheral T-cell lymphomas (PTCL). Therefore, we examined DTI and its association with clinical factors and outcomes in a prospective observational cohort of patients with PTCL from the United States within the LEO (Lymphoma Epidemiology and Outcomes) and MER (University of Iowa and Mayo Clinic Specialized Programs of Research Excellence Molecular Epidemiology Resource). Patients and Methods We evaluated patients enrolled to the MER (2002-2015) and LEO (2015-2020) cohorts with the following forms of PTCL: PTCL-not otherwise specified (PTCL-NOS, n=217), nodal T-follicular helper (TFH) cell lymphoma (nTFHL, n=153), anaplastic large cell lymphoma (ALCL), ALK positive (ALCL, ALK+, n=74), ALCL, ALK negative (ALCL, ALK-, n=95), enteropathy associated T-cell lymphoma (n=18), and monomorphic epitheliotropic intestinal T-cell lymphoma (n=2). Associations of DTI with clinical factors and outcomes were examined using Kaplan Meier and Cox models. Event free survival (EFS) was defined as the time from start of treatment to relapse/progression, start of 2nd line therapy, or death from any cause. Overall survival (OS) was defined as the time from start of treatment until death from any cause. DTI was defined as the number of days between the first diagnostic biopsy and the start of therapy. Patients who were initially observed or had DTI > 100 days were excluded. Results In 559 patients (229 MER and 330 LEO), median age was 60, 34% had IPI>2 and 71% were stage III/IV. 472 (84%) patients initially received anthracycline-based chemotherapy. Median DTI was 23 days (interquartile range (IQR): 12-39) and was similar in MER (21 days, IQR: 11-33) and LEO (25 days, IQR: 14-42). 168 (30%) patients had DTI 0-14 days, 178 (32%) 15-28 days, and 213 (38%) 29-100 days. Overall in the cohort, shorter DTI was associated with a worse 5-year OS (DTI 0-14 days: 43%; DTI 15-28 days: 53%; DTI 29-100 days: 58%, p<0.001) and 5-year EFS (DTI 0-14 days: 31%; DTI 15-28 days: 39%; DTI 29-100 days: 45%, p<0.001). In multivariable analyses, the association of DTI with outcomes remained consistent after adjusting for age and International Prognostic Index (IPI). Shorter DTI was strongly associated with adverse clinical factors, including elevated lactate dehydrogenase levels, poor performance status, B-symptoms, and higher IPI in both cohorts (all P < .003). DTI was not associated with age, sex, or distance from the LEO/MER center (all p>0.3). 6% patients with DTI of 0-14 days received 1L treatment on a clinical trial, compared to 11% with DTI 15-28 days and 13% with DTI 29-100 days, underscoring that patients with lower DTI may be underrepresented in clinical trials. When examining within PTCL subtypes, the association between short DTI (0-14 days) and inferior outcomes was most prominent in PTCL, NOS (OS HR=2.13, 95% CI: 1.52-2.94; EFS HR =1.49, 95% CI: 1.19-1.85). Associations between short DTI and outcomes were weaker in other subtypes: nTFHL (OS HR=1.28, 95% CI: 0.83-2.00; EFS HR =1.22, 95% CI: 0.82-1.81), ALCL, ALK-, (OS HR=1.30, 95% CI: 0.59-2.86; EFS HR =1.32, 95% CI: 0.68-2.56), ALCL, ALK+, (OS HR=1.05, 95% CI: 0.26-4.17; EFS HR =2.12, 95% CI: 0.84-5.26). Conclusion Shorter DTI is associated adverse prognostic clinical factors (LDH, stage, high IPI) and inferior EFS and OS in newly diagnosed PTCL. Patients with DTI ≤ 14 days, which represents approximately 1/3 patients with PTCL, may be underrepresented in clinical trials. Understanding of this selection bias should inform clinical trial design and interpretation. Future studies should consider strategies to minimize barriers to enrollment for patients with low DTI.

Abstract Myeloproliferative neoplasms (MPNs) are typically ascribed to hyperactive JAK-STAT signaling via mutations in JAK2, CALR, or MPL. Here, we characterize how activating mutations in the calcium sensor STIM1, previously established as the cause of Stormorken Syndrome (SS), a rare congenital disorder, are sufficient to drive development of myelofibrosis (MF). We further uncover distinct interactions between STIM1 activity and JAK2 versus CALR driven MPNs. We initially identified two SS patients with activating mutations in STIM1 (R304W and S88G) and features of MF, including marked reticulin fibrosis with megakaryocytic hyperplasia and atypia. This led us to hypothesize that altered calcium signaling may play a role in the development of MF in both SS and MPNs. Single cell RNA sequencing performed on samples from both patients demonstrated elevated NFκB inflammatory signaling in monocyte populations, suggesting a link between altered STIM1 and store operated calcium entry (SOCE) activity and aberrant inflammation, thereby contributing to MF development. To corroborate these findings from our SS patients, we generated a knock-in mouse model of the heterozygous R304W mutation. Induction of hematopoietic-specific expression of mutant Stim1 with Vav-Cre recapitulated the hematological features of SS, including elevated SOCE activity and thrombocytopenia. We also recapitulated MF features including the development of bone marrow fibrosis and severe osteosclerosis, with the mice developing splenomegaly as young as 9 weeks old. In ex vivo megakaryocyte differentiation assays with our Stim1 R304W knock-in mice, we also observed aberrant cytoskeletal organization and elevated TGFβ mRNA expression. When induction was driven universally through CMV-Cre, we also validated that mice recapitulated multiple SS features, including thrombocytopenia, tubular aggregate myopathy, growth deficiency, and the development of bone marrow fibrosis as young as 10 weeks. We additionally identified a separate cohort of 9 related individuals with SS and STIM1 mutations (L92V) as well as a separate patient with the R304W mutation. In ex vivo megakaryocytic differentiation assays, cells from SS patients demonstrated defective thrombopoiesis with significantly decreased proplatelet formation, and displayed aberrant cytoskeletal formation within the pro-platelet termini, in conjunction with increased expression of TGFβ. Further supporting a role for STIM1 in MPNs, we identified upregulation of STIM1 expression in MPN patient CD34+ hematopoietic stem/progenitors' cells (HSPCs), we well as megakaryocyte progenitors and platelets, including those with CALR or JAK2 mutations. To evaluate the functional role of STIM1 in MPNs, we generated patient-derived xenograft (PDX) models with CALR and JAK2-mutantpatient samples subjected to CRISPR ablation of STIM1. In an initial CALR-mutant PDX experiment, abrogation of STIM1 led to decreased human CD45+ cell engraftment in conjunction with prolonged survival. In a second CALR-mutant PDX experiment, STIM1 targeting did not overtly impact engraftment or survival. In contrast, CRISPR ablation of STIM1 in JAK2-mutant PDX models led to exacerbated disease phenotypes, including increased human CD45+ cell engraftment, increased splenomegaly, and early lethality. Altogether, this study represents the first demonstration of MF development in patients with Stormorken Syndrome and reveals a previously unrecognized role of aberrant SOCE underlying SS and MPNs. We recapitulated these findings in a novel conditional mouse model. These findings also illustrate unique interactions between STIM1 and JAK2 and CALR driven MPNs. These observations have important implications for the development of targeted therapeutic approaches for these disorders.

Abstract Introduction:A comprehensive integration of significantly mutated genes and pathways with molecular subgroups is lacking in adult B-ALL. Furthermore, the genomic drivers underlying each subgroup remain to be identified.We aimed to perform genomic analysis on a large cohort of patients with adult B-ALL, and to correlate genomic markers with achievement of MRD negativity enabling blinatumomab randomization, and with subsequent response to blinatumomab. Methods:For genomic analysis, we studied 569 adults with newly diagnosed B-ALL registered for initial screening on the ECOG-ACRIN-led E1910 trial (NCT02003222), which evaluated the addition of blinatumomab to standard consolidation chemotherapy. The median age was 52 yrs (range 30 to 71 yrs), with 52% males. Analysis was performed on tumor and matched-normal samples using whole transcriptome sequencing (RNA-seq; tumor only; n=569), whole exome sequencing (n=490), whole genome sequencing (n=131), and single nucleotide polymorphism array (n=445). B-ALL cases were classified into 22 molecular groups. Outcome analysis was limited to patients enrolled and treated on E1910 (n=319). Results: Driver genes (n=268) were identified by the mutation-significance detection tool dNdScv or by the presence of pathogenic variants in known cancer genes, with NUP188 identified as a novel driver gene. Recurrently mutated pathways included: B-cell development (46%), cell cycle (44%), epigenetic regulation (30%), other transcriptional regulation (27%), Ras signaling (25%), RNA machinery (17%) and JAK-STAT signaling (8%). A high frequency of high-risk subtypes was observed including BCR::ABL1 (20%), BCR::ABL1-like (18%), low hypodiploid (14%) and KMT2A (12%). Using tSNE analysis, we identified a new cluster of cases (n=20, 3.5%) lacking a known subgroup driver, with overexpression of CEBPA (n=13) or CEBPB (n=7), distinct from CEBPE/ZEB2, termed “CEBP-altered” ALL (CEBPalt). Five of 13 cases with high CEBPA expression harbored an IGH::CEBPA rearrangement and one harbored a RXRA::CEBPA enhancer hijacking alteration. Of the 7 cases with high CEBPB expression, 5 harbored IGH::CEBPB, and two of these had concomitant clonal BCR::ABL1 fusions. To identify additional mechanisms of CEBP deregulation, in situ Hi-C coupled to H3K27 acetylation immunoprecipitation (HiChIP) was performed on 5 cases. Four cases showed evidence of de novo CEBPA enhancer activity. In two cases, we identified novel insertions (12 and 34nt) ~2kb downstream of CEBPA. A novel translocation and enhancer hijacking event between LINC00426 and the 5' UTR of CEBPB was identified in the remaining case. Overall, we confirmed genomic alterations of CEBPA or CEBPB in 16 of 20 cases with available material. Thus, we have identified a new molecular subgroup of adult B-ALL characterized by genomic alterations that drive enhancer hijacking and oncogenic deregulation of CEBPA/CEBPB. Several subgroups were enriched in patients that failed induction chemotherapy (n=62) or were MRD-positive (n=63) compared to those that achieved MRD-negative status (n=194): BCR::ABL1-like (30 vs 14%, p<0.001), KMT2A (18 vs 9%, p=0.03) and BCL2/MYC (5 vs 1%, p=0.06). Conversely, the following subgroups were enriched in patients that achieved MRD-negativity: PAX5alt (6 vs 18%, p=0.002), TCF3::PBX1 (0 vs 5%, p=0.01) and ZNF384 (2 vs 6%, p=0.08) Within each molecular subgroup we compared the survival of patients who achieved MRD-negative status after induction and were randomized to receive blinatumomab plus chemotherapy (n=93) or chemotherapy only (n=91). Although numbers were low, blinatumomab improved relapse-free survival for patients with hyperdiploid, PAX5alt, BCR::ABL1-like and KMT2A ALL compared to chemotherapy alone. Clonal hematopoiesis of indeterminate potential (CHIP)-related gene mutations were identified in 121 of 417 cases analyzed (29% total: somatic 74%, remission 31%, both 5%). TP53 mutations were most frequent (n=65 patients), with the majority identified in patients with low hypodiploid (n=52). Interestingly, patients with CRLF2 rearrangements collectively harbored the highest number of other CHIP gene mutations (n=13), including DNMT3A (n=4), TET2 (n=3) and ASXL1 (n=3). Conclusions:We provide a comprehensive landscape of genomic alterations in adult B-ALL and identify a new group characterized by deregulation of CEBPA/CEBPB (CEBPalt). We also provide insights into the efficacy of blinatumomab in different molecular subgroups of adult B-ALL.

Abstract Introduction Understanding the tumor immune microenvironment (TIME) in multiple myeloma (MM) is critical for identifying prognostic biomarkers and therapeutic targets. We hypothesized that specific immune cell populations within the bone marrow TIME are associated with clinical outcomes and could enhance patient stratification. To this end, we conducted the largest CyTOF-based immune profiling study to date in MM, profiling >300 million bone marrow immune cells from patients enrolled in the CoMMpass study. Methods We analyzed >1,000 bone marrow samples from ~700 newly diagnosed MM patients enrolled in the MMRF CoMMpass study (NCT01454297), using a harmonized protocol and 41-antibody CyTOF panel at five academic centers. The majority were baseline samples (n=671), with additional samples spanning up to 3.5 years post-diagnosis (n>300). Each site contributed ~200 samples on average. The cohort included 40% females, with a median age of 63 years and BMI of 27.8. ISS stages were evenly distributed (I: 36%, II: 36%, III: 29%), and 84% had ECOG 0-1. Autologous stem cell transplant was performed in 58% of patients, and 22% received maintenance therapy. Results We profiled 311 million single cells across the cohort, identifying major immune compartments: Neutrophils (36.0%), CD4 T cells (19.7%), NK cells (9.9%), monocytes (7.6%), B cells (5.7%), and CD8 T cells (5.6%). Less abundant populations included dendritic cells, γδ T cells, plasmablasts, and pDCs. In our preliminary analysis with multivariate cox regression modeling, we identified clinical factors including stem cell transplant, ISS stage, and ECOG status, as independent predictors of overall survival (OS). After adjusting for age and sex, higher proportions of naïve B cells, pDCs, and γδ T cells were independently associated with improved OS, while CD4+ T cell abundance was positively associated with prolonged progression-free survival (PFS). In contrast, elevated neutrophil proportions were significantly linked to inferior OS and demonstrated a trend toward shorter PFS. Longitudinal immune profiling in more than 200 patients identified a gradual accumulation of naïve B cells and a pronounced post-treatment rise in CD45+ plasmablasts, highlighting persistent B cell activity as a candidate mechanism for sustained therapeutic efficacy. Conclusion This study presents the largest immune proteomic atlas in MM to date, linking TIME composition to clinical outcomes. A favorable immune landscape was marked by preserved humoral immunity (naïve B cells, plasmablast expansion), enrichment of pDCs and γδ T cells, and lower neutrophil abundance, collectively associated with improved survival outcomes. These findings lay the groundwork for immune-guided prognostication and highlight new opportunities for therapeutic targeting in MM. Ongoing analyses aim to further resolve baseline and longitudinal immune dynamics in relation to treatment response.