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Abstract Background: MyeloMATCH is an NCI-sponsored initiative for acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) employing a Master Screening and Reassessment Protocol (MSRP) to assign patients (pts) to a pt and disease biology-specific clinical trial. Several trials evaluating initial therapies are currently open, while subsequent trials dedicated to eradicating measurable residual disease during consolidation and including stem cell transplant are being developed. A pt enrolled at diagnosis may be followed longitudinally and be eligible for trials in sequential tiers throughout the treatment course. We report key data concerning the first cohort of pts enrolled on the MSRP. Methods: After pts with suspected AML or MDS consent for the MSRP, blood and marrow are sent to the myeloMATCH Molecular Diagnostics Network (MDNet) of central CLIA labs operating under a single Investigational Device Exemption to rapidly define molecular, cytogenetic, and immunophenotypic characteristics. These data are catalogued by a bioinformatics team (MATCHBox) and reviewed daily to assign participants to an available trial based on pt and disease features. A Tier Advancement Pathway (TAP) allows standard of care therapy with potential for assignment to subsequent myeloMATCH trials. Since activation in May 2024, 550 patients age≥18 were enrolled on the MSRP from 76 institutions: 48 Academic, 14 NCORP, 11 community, 3 VA. There are currently 4 open randomized AML trials (≥age 60 or unfit with mutant FLT3, ≥age 60 IDH2 mutant AML, fit age<60 ELN 2017 intermediate-risk AML, fit age<60 ELN 2017 adverse risk) and 1 MDS trial(IDH2 mutant). Patients not eligible for an open protocol were assigned to TAP. Results: Of the 550 pts consented, 491 completed screening assays; 49 had no or incomplete samples; 10 withdrew before completed analysis. Median cytogenetic turnaround time (TAT) was 69 hours (91% within 72 hours), and median Next Generation Sequencing (NGS) TAT from receipt was 49 hours (95% within 72 hours). Seventy-six pts (of 491 with assay data) were not assigned due to non-AML or non-MDS diagnoses, the most common being: B-ALL [n=11], MPN [9], benign marrow [9], APML [7], and MPAL [6]. The AML/MDS verified cohort was 415 pts, 366 (89.2%) patients with AML (45% age <60) and 49 (11.8%) with MDS. The median age at screening was 63 years (range:18-95) and 186 (45%) were female. Eighty-two percent identified as White, 7.5% Black, 3% Asian, 7% unknown, and 9% as Hispanic. The most frequent mutations in the AML pts were NPM1 (24.0%), DNMT3A (22.7%), TET2 (19.9%), NRAS (18.0%), FLT3 (18.0% ITD, TKD 7.1%), TP53 (14.5%), and CEBPA (8.7%); IDH1/2 mutation rates were 8.2% and 13.7%, respectively. Co-mutations include FLT3/NPM1 (9.8%), NPM1/IDH2 (4.4%), IDH1/2 and any RAS (3.8%). Karyotypes were normal in 40.4%, complex 20.8%, inv(16) 6.0%, MLL/KMT2A 4.6% and t(8;21) 1.9%. 29% had favorable risk disease, 29% intermediate, and 42% adverse (ELN 2017). In MDS, mutations included: TP53 (36.7%), RUNX1 (20.4%) ASXL1 (20.4%), TET2 (18.4%), spliceosome mutations (SRSF2, SF3B1, U2AF1 and ZRSR2, 28.6%) andIDH1/2 in 4.1% and 6.1%, respectively. Karyotypes were normal in 24.5%; complex in 40.8%. By IPSS-R, 2.4% were low, 73.8% intermediate, 2.4% high, and 21.4% very high risk. 82/415 (20%) pts were assigned to initial therapy protocol, with an increase in assignment rate to 44% in the most recent two months. 71/415 pts (16%) were enrolled in one of the MyeloMATCH studies. Three-hundred forty-four pts (80%) were assigned and enrolled to TAP (296 AML, 48 MDS) for potential assignment to subsequent tier trials. In the TAP AML pts, 99 (33%) have completed initial treatment, including intensive chemotherapy (IC) in 62% of pts and hypomethylating agents/venetoclax (HMA/VEN) in 38%. In pts <60 years of age, 87% received IC v. 13% with HMA/VEN, in >60 34% IC v. 66% HMA/VEN and in age 60-75 42% IC v. 58% HMA/Ven. Conclusion: MyeloMATCH has screened over 500 pts from academic and community sites in the US and Canada in 14 months, meeting the TAT goal of sample acquisition to results of <72 hours. Assignment to treatment protocols has substantially increased recently. As additional trials open (12 in development) we expect the percentage of pts enrolled on MSRP who go on to therapeutic trials will markedly increase, thereby allowing a personalized medicine approach for a broad group of US and Canadian adult pts with AML and MDS.

Abstract Over the past decade, classification systems using high-throughput genetic data have been developed to identify molecular subtypes of DLBCL. Although not a primary goal, these classifiers were also proposed as prognostic factors in their respective publications. To date, however, no study has directly compared these classifiers' ability to predict overall (OS) and event-free survival (EFS) in the same cohort. Herein, we sought to systematically compare predictive performance, benchmarked against the IPI, of several current established molecular classifiers and evaluate if any add significant independent prognostic information beyond the IPI. WES (including paired germline filter) and RNAseq data from newly diagnosed DLBCL patients (N=432; 2018 WHO criteria) in the Mayo Clinic/University of Iowa Lymphoma Molecular Epidemiology Resource (MER) were available for analysis (WES n=112, RNAseq n=40, or both n=280). The number of cases able to be classified (including as unclassified) for each classifier was as follows: IPI (432, 100%), cell-of-origin (COO, by Hans algorithm; 346, 80.1%), refined COO (by gene expression with Dark Zone Signature; 320, 100%), Haematological Malignancy Research Network (HMRN; 349, 89.0%), B-cell state (320, 100%), Lymphoma Ecotype (320, 100%), Lymphoma Microenvironment (LME; 320, 100%), Tumor microenvironment (TME26; 320, 100%), SubLymE (312, 97.5%), LymphGen (358, 91.3%), and DLBclass (223, 58.2%). OS was defined as time from diagnosis to all-cause death while EFS was defined as time from diagnosis to disease progression, initiation of second-line treatment, or all-cause death. We calculated Harrell's c-statistics for each Cox proportional hazards model evaluating the discriminative performance of each classifier in predicting OS/EFS. Using bootstrap validation, we obtained optimism-corrected c-statistics, which we report in the results. We performed likelihood ratio tests (LRT) comparing a univariable Cox model with IPI alone and models including both IPI and a given classifier to assess if a classifier provided independent prognostic information beyond the IPI. All patients were treated with immunochemotherapy (IC) with curative intent, 247 (57%) were male, median age at diagnosis was 65 years (IQR 55-72 years), 390 (96%) were White, 209 (60%) had GCB subtype by Hans, 22 (5.1%) had MYC double-hit by FISH (MYC and BCL2 or BCL6), and 162 (37.9%) had an IPI ≥ 3. The median follow-up was 7.0 years, 167 (39%) experienced an event, and 137 (32%) died. In a univariable Cox model, the c-statistic for IPI predicting OS was 0.66 (95% confidence interval [CI] 0.61-0.70). All other classifiers had c-statistics of ≤0.56. The c-statistic for IPI predicting EFS was 0.64 (95% CI 0.60-0.69), and all other classifiers had c-statistics of ≤0.58. The univariate DLBclass results for OS and EFS were not significantly impacted when restricted to cases with confidence >0.7 (n=136). In Cox models of IPI alone versus IPI plus an individual classifier, the only classifier that provided statistically significant, independent information for OS was TME26 (LRT p=0.02). Adjusting for IPI, patients who were TME26-negative had significantly inferior OS compared to TME26-positive cases (HR 1.63, 95% CI 1.07-2.47; p=0.02). For EFS, DLBclass (restricted to confidence >0.7) added significant prognostic information beyond IPI (LRT p=0.02). This finding was largely driven by C5 subtype; relative to C1 subtype and adjusting for IPI, C5 subtype had significantly inferior EFS (HR 5.53, 95% CI 1.81-17.0; p=0.003). In summary, we compared prognostic performance of multiple DLBCL molecular classifiers with respect to OS and EFS in a single real-world, prospective cohort of newly diagnosed, IC-treated DLBCL. Our data supports two key findings: all classifiers had modest performance for prognosis, and none individually outperformed the IPI in predicting OS nor EFS. Second, only TME26 and DLBclass (confidence >0.7) provided additional prognostic information beyond that captured by the IPI for OS and EFS, respectively. This finding suggests that the tumor immune microenvironment and characteristics of C5 DLBCLs (ABC-subtype, CD79B mutations) can potentially offer significant independent information for predicting survival and response to front-line immunochemotherapy. If replicated, these findings could inform risk-adapted treatment approaches and aid in identifying high-risk patients for enrollment in genomically-informed clinical trials.

Abstract Introduction: Clinical outcomes for patients (pts) with Philadelphia chromosome positive (Ph+) B-cell precursor Acute Lymphoblastic Leukemia (B-ALL) have significantly improved with the incorporation of tyrosine kinase inhibitors (TKI) and immunotherapy. Although the incidence of central nervous system (CNS) relapse in Ph+ B-ALL is rare, it has become an emerging challenge with chemotherapy-free approaches. While IKZF1, CDKN2A/B and emergence of T315I kinase domain mutations in ABL1 have been associated with worse outcomes (Foà R, JCO, 2024),further characterization of patients with CNS relapse could prove useful in risk stratification and optimizing treatment intensification. Currently, high white blood cell count (WBC) is being assessed as a marker to identify pts who may benefit from addition of CNS penetrant chemotherapy (ex. cytarabine or high-dose methotrexate (HD-MTX)) to TKI and immunotherapy protocols (Short NJ, J Hematol Oncol, 2025). Methods This is a multicenter retrospective study of relapsed/refractory Ph+ B-ALL pts under the COMMAND consortium. Age, gender, induction regimen and TKI of choice during induction were descriptively reported for the entire cohort. Categorical variables were compared, using Fisher's exact test, between pts with CNS relapse and pts with systemic relapse. Variables of interest were the presence of IKZF1 or CDKN2A/B alterations, emergence of T3151 mutation, CNS disease at diagnosis (dx), WBC >70K/microliter at dx, use of high-dose methotrexate (HD-MTX) during induction or consolidation, and use of TKI as part of the induction regimen. Odds ratio (OR) and 95% confidence intervals (CI) were reported for each variable. Results A total of 654 Ph+ B-ALL pts were initially identified across multiple centers in the United States, of whom 20 (3%) experienced a CNS relapse and 157 (24%) experienced a systemic relapse on median follow up of 29 months (range, 0-207). A total of 15 pts with CNS relapse and 114 pts with systemic relapse were used for this analysis after exclusion of pts without molecular data. The median age for the 129 pt cohort was 55 years (range 22-85), of whom 65 pts (50%) were male. Induction regimens used were intensive chemotherapy (IC)+TKI for 79 pts (61%), low-intensity chemotherapy or steroids (LDC-S)+TKI for 40 pts (31%), IC without TKI during induction for 5 pts (4%) and blinatumomab+TKI for 1 pt (1%). TKI of choice during induction included second-generation TKIs (dasatinib, nilotinib) for 77 pts (60%), imatinib for 30 pts (23%), ponatinib for 15 pts (12%) and none during induction for 5 pts (4%). CNS disease at dx was found in 6/15 pts (40%) with CNS relapse and 9/114 pts (8%) with systemic relapse, which was a statistically significant difference (p=0.002, OR= 7.57, 95% CI= 1.81 - 31.08). The systemic treatment regimens for the 15 pts with CNS disease at x were IC+TKI for 10 pts (66%) and LDC-S+TKI for 5 pts (33%), 9 of the pts (60%) received HD-MTX during induction. Intrathecal (IT) chemotherapy administration data at dx was available for 8 pts (53%) with CNS disease at dx, of whom 2 pts received <9 doses, 4 pts received 9-12 doses and 2 pts received >12 doses of IT chemotherapy. Although not statistically significant, pts with CNS relapse were more likely to have IKZF1 or CDKN2A/B alterations (p = 0.648, OR= 1.44, 95% CI= 0.14-7.78), WBC >70K/mcl (p = 0.472, OR= 1.73, 95% CI= 0.34-7.41), emergence of T3151 mutations (p = 0.123, OR= 2.54, 95% CI= 0.72-8.84) and use of HD-MTX during induction or consolidation (p = 0.262, OR= 2.15, 95% CI= 0.61-8.61); while they were less likely to have received a TKI during induction (p = 0.106, OR= 0.18, 95% CI= 0.02-2.34). Conclusion This data confirms that the presence of CNS disease at dx is associated with CNS relapse. Despite recent incorporation into clinical trials, WBC≥70K/mcl and omission of HD-MTX were not seen more frequently in pts with CNS relapse in this cohort. However, this analysis is limited by the small number of pts who experienced CNS relapse. With the rising use of chemotherapy-free regimens, prospectively trialing treatment intensification, such as with additional IT chemotherapy or HD-MTX, could be prospectively trialed in pts with CNS disease at dx to potentially improve outcomes for this subset of pts. The impact of increasing IT chemotherapy doses or additional cycles of systemic chemotherapy in this pt population is yet to be elucidated.

Abstract Background: Despite recent therapeutic advances in AS cHL, PET-adaptive chemotherapy-based regimens remain a first-line treatment option, especially for patients (pts) without access to novel agents. Most PET-adaptive regiments start with either 2 cycles of escBEACOPP (escBEACOPP2) or ABVD (ABVD2) prior to interim PET assessment (iPET), followed by treatment de-escalation or intensification by iPET result. There have been no direct comparisons of escBEACOPP2 vs ABVD2 PET-adaptive regimens. Additionally, the AS-Hodgkin Lymphoma International Prognostication Index (A-HIPI) score (Rodday JCO 2023) has not been fully explored in escBEACOPP2 regimens. Therefore, we utilized multiple analytic approaches to compare outcomes of PET-adaptive escBEACOPP2 and ABVD2 regimens, while adjusting for and assessing the effect of the baseline A-HIPI score. Methods: Through the global HoLISTIC Consortium (www.hodgkinconsortium.com), we obtained individual patient data from 4 AS clinical trials of newly diagnosed cHL pts treated with PET-adaptive escBEACOPP2 (AHL2011) or ABVD2 (SWOG0816, RATHL, HD0607) regimens. Pts were restricted to age 18 to 65 years (y), stage IIB-IV, and PET-adapted treatment arms. Positive iPET was based on Deauville score >3. Treatment effects of escBEACOPP2 vs ABVD2 (reference) on 5y progression-free survival (PFS) and overall survival (OS) were first evaluated using Cox models. Importantly, baseline disease risk was adjusted for using the 5y PFS or OS A-HIPI score (including stage, sex, age, bulk, lymphocyte count, albumin, white blood cell count), where higher scores indicate higher predicted risk (scale 1-100). The A-HIPI was modeled per 1 standard deviation (SD) increase. Our multistate model (MSM) comprised 4 health states: diagnosis, sustained remission at 1yr, treatment failure, and death from any cause. Pts all started in the diagnosis state and transitioned to other states without return to prior states. We assessed the impact of treatment on transitions (except binary sustained remission at 1y) that involved ≥5 pts per treatment group, adjusting for A-HIPI for all transitions. All effects are reported as adjusted hazard ratios (aHRs) with 95% confidence intervals (CI). Results: 2,381 AS cHL pts were included (n=372 for escBEACOPP2, n=2009 for ABVD2). For escBEACOPP2 and ABVD2 groups (median follow-up 60 and 56 months), respectively, the mean baseline A-HIPI scores (i.e., predicted 5y PFS event rate) were 25.1 (SD=6.3) and 22.9 (SD=6.5), the rates of positive iPET were 11.3% and 17.0%, 5y PFS was 87.0% and 79.5%, and 5y OS was 96.3% and 94.6%. In Cox models, escBEACOPP2 was associated with significantly improved PFS compared to ABVD2 (aHR=0.54, 95% CI=0.39-0.73); the aHR for OS was 0.67 (95% CI=0.37-1.19). Notably, higher risk A-HIPI score was associated with significantly worse PFS (aHR=1.42, 95% CI=1.31-1.54) and OS (aHR=1.60, 95% CI=1.47-1.76), independent of treatment. In the MSM, the effect of escBEACOPP2 compared to ABVD2 regimens was modeled in 3 transitions with adjustment for A-HIPI score: those treated with escBEACOPP2 had lower likelihood of treatment failure with (aHR=0.38, 95% CI=0.22-0.66) or without (aHR=0.61, 95% CI=0.40-0.92) sustained remission at 1y; the aHR for treatment failure to death was 0.55 (95% CI=0.25-1.22). Higher risk baseline A-HIPI score was associated with higher likelihood of treatment failure and death without sustained remission at 1y (aHR=1.43, 95% CI=1.28-1.61 and aHR=2.50, 95% CI=1.80-3.49, respectively). Furthermore, higher risk baseline A-HIPI score was associated with higher likelihood of treatment failure after achieving sustained remission at 1y (aHR=1.29, 95% CI=1.12-1.48) as well as death after treatment failure (aHR=1.54, 95% CI=1.27-1.86). Conclusions: Comparing newly diagnosed adult AS cHL PET-adaptive regimens with adjustment for baseline A-HIPI score, we found pts treated with escBEACOPP2 on AHL2011 had improved PFS versus pooled pt data from 3 ABVD2 trials. Using MSM, we further demonstrated that escBEACOPP2 was associated with a lower likelihood of treatment failure with or without achieving sustained remission at 1yr. In addition, baseline A-HIPI score was associated with PFS and OS, which was independent of treatment. Finally, higher baseline A-HIPI scores maintained prognostic impact throughout the disease course, including increased risk of treatment failure for pts in remission at 1yr and death after treatment failure.

Abstract Introduction: Lisocabtagene maraleucel (liso-cel) was approved in the United States for the treatment of CLL in 3/2024 for patients who have received two prior lines of therapy including a covalent BTK inhibitor and a BCL-2 inhibitor. Data regarding outcomes of liso-cel is limited to reports from the registrational TRANSCEND-CLL 004 clinical trial which had strict inclusion and exclusion criteria. This work investigates the real-world efficacy and safety of liso-cel for patients with CLL and its efficacy in specific sub-populations. Methods: This is a multi-institutional retrospective study (Collaborative Assessment of Real-World Evidence of Lisocabtagene Maraleucel in Patients with Relapsed/Refractory CLL/SLL [CARE CAR-T CLL]) of patients with CLL who received commercial liso-cel in the United States. Patients with Richter transformation were excluded. Response was defined by iwCLL criteria. Patients who did not undergo a marrow biopsy but met other criteria for a complete response (CR) were categorized as unconfirmed CR (CRu). CRS and ICANS were graded per ASTCT criteria. Results: A total of 30 patients were identified with a median age of 67 years (range 44 – 80). Twenty of thirty patients (67%) had either del17p and/or mutated TP53, and 8/30 (27%) had complex karyotype (≥ 3 abnormalities) at time of liso-cel infusion. Patients received a median of 6 prior lines of therapy (range 1 - 12), and 24 (80%) were previously treated with chemotherapy. All patients had previous exposure to a covalent BTK inhibitor and a BCL-2 inhibitor. Twenty-seven (90%) of patients had prior exposure to pirtobrutinib. Twenty-nine patients (96.7%) received bridging treatment that was stopped after leukapheresis with 1 patient in CR and 25 patients in PR at time of liso-cel. Eighteen patients (60%) were treated with pirtobrutinib as the last line of treatment prior to liso-cel. Median length of time on pirtobrutinib prior to liso-cel infusion was 4 months (interquartile range [IQR], 2 – 8 months). Twelve (66.7%) patients stopped pirtobrutinib between leukapheresis and lymphodepletion, and 6 continued after liso-cel. Best CR/CRu rate was 60.0% (CR, n = 17/30; CRu, n = 1/30), and best overall response rate (ORR) was 83.3% (25/30) with median time to best response of 30 days (IQR, 28 – 30 days). Of the 18 patients who received pirtobrutinib as their last line of therapy, 13 (72%) achieved a CR/CRu. Meanwhile, of the 12 patients who did not receive pirtobrutinib as their last line of therapy, only 5 (28%) achieved a CR. Measurable residual disease testing (MRD) by flow cytometry was done in 14/30 patients, and 9 patients (64%) had achieved undetectable MRD (uMRD). MRD by next generation sequencing (NGS) was done in 17 patients, and 7 (41%) patients had uMRD. Twenty-seven of 30 patients (90%) were alive at time of data collection. Median follow-up was 3.3 months (IQR, 1.2 – 8.9 months). Twenty-six patients (87%) experienced any grade cytokine release syndrome (CRS), and 3 patients experienced grade 3 CRS (10%). Twelve patients (40%) experienced any grade immune effector cell-associated neurotoxicity syndrome (ICANS), and 4 patients (13%) experienced grade 3 ICANS. There were no grade 4 or 5 CRS or ICANS. One patient experienced grade 3 immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS). At day 30, patients had a median absolute neutrophil count of 1.7K/μL (IQR, 0.8 – 3.6K/μL), hemoglobin of 11.7 g/dL (IQR, 8.6 – 13.1 g/dL), and platelet count of 72K/μL (IQR, 29 – 119K/μL). Conclusion: Real-world analysis of liso-cel for patients with relapsed/refractory CLL showed CR and ORR of 60.0% and 83.3%, respectively. Despite having a heavily pre-treated and chemotherapy-exposed population and with over half the patients having high-risk features, these response rates are higher than what was described in the TRANSCEND-CLL 004 clinical trial. These results are limited by the short follow-up period and the variability in response assessment typical of a retrospective study. As we increase our sample size, we will also be interested if the use of the non-covalent BTK inhibitor pirtobrutinib prior to liso-cel is associated with a higher CR rate, mimicking the findings of the sub-cohort analysis of TRANSCEND-CLL 004 where the concurrent use of ibrutinib led to higher CR rates. Further updates and patients from additional collaborators will be presented at the meeting.

Abstract Background: A randomized multicenter trial (BMT CTN 1703) demonstrated that after reduced intensity conditioning HCT, PT-Cy-based GVHD prophylaxis led to significant reductions in acute and chronic GVHD, but was associated with significantly more Grade 2 (moderate) infections and similar overall survival vs Tac/MTX. A linked mechanistic study (BMT CTN 1801) found that PT-Cy led to pan-T cell depletion and reduced T cell receptor (TCR) repertoire diversity vs Tac/MTX. To discover the molecular mechanisms driving the association of PT-Cy with increased infections, we examined pathogen-specific T cell reconstitution in BMT CTN 1801 patients (n=165 PT-Cy, n=159 Tac/MTX). Methods: We performed deep TCR sequencing on 2,369 blood samples collected pre-HCT (recipient baseline) and on Days +7, 14, 28, 63, 100, 180, 270, 365, 730, and from the graft infusion product. We then applied a novel set of TCR classifiers (Adaptive Biotechnologies) capable of identifying pathogen-specific clones associated with CMV, EBV, SARS-CoV-2, HSV-1, HSV-2, parvovirus, RSV, influenza A, rhinovirus, adenovirus, HHV-6B, norovirus and Toxoplasma. Single-cell (sc) TCR/RNA-sequencing on a sample subset (n=26) was performed to determine the phenotype of pathogen-specific T cells. Results. By linking scRNA-seq with pathogen-specific TCR barcoding, we identified CD4 and CD8 memory T cells as their predominant T cell reservoir. We found that the total number of pathogen-specific singleton TCRs was significantly lower with PT-Cy, starting early post-HCT and persisting through 2 years. For example, at Day +14, PT-Cy patients had 7.8-fold fewer pathogen-specific singleton TCRs vs Tac/MTX (mean of 6.9 vs 54.1, p<0.001). Consistent differences between PT-Cy and Tac/MTX were observed for TCRs specific for each pathogen individually. Patients who developed Grade 3 (severe) viral infections had significantly fewer pathogen-specific singleton TCRs at Day +14 compared to those who had no viral infections (mean of 4.0 vs 32.5, p=0.03). Leveraging intrinsic TCR barcoding of the HCT infusion (“graft”) and of the patient's baseline samples (“recipient”), we could assign the graft/recipient origin of the pathogen-specific cells with high fidelity. This analysis revealed pronounced differences in the origin of pathogen-specific T cells with PT-Cy vs Tac/MTX, especially prior to Day +100. The absolute number of pathogen-specific TCRs originating from the graft was significantly higher with Tac/MTX vs PT-Cy. This difference was observed from day +7 through 6 months post-HCT, with up to 7.1-fold more graft-derived pathogen-specific TCRs in Tac/MTX vs PT-Cy (p<0.001 at each timepoint before day +100). Within patients who received Tac/MTX, the balance of graft vs recipient pathogen-specific clones significantly favored graft clones (for example, a mean of 14.9 graft vs 8.6 recipient pathogen-specific TCRs at Day+14, p=0.02). By contrast, with PT-Cy, in addition to having substantially fewer pathogen-specific TCRs overall, the proportion of these TCRs was not significantly different between graft and recipient clones (mean of 2.1 graft vs 3.3 recipient pathogen-specific TCRs at Day+14, p=0.42). These data uncover that, in addition to the reduction in pathogen-specific T cells with PT-Cy, there was a relative skewing of the anti-microbial T cell reservoir towards recipient cells that persisted after conditioning. Conclusions: PT-Cy led to in vivo T cell depletion across all T cell subsets, which prominently included clones tracked from the allograft itself into the HCT recipient, with a relative sparing of recipient T cell clones that survived transplant conditioning. While the mechanism for relative sparing of recipient cells has not yet been determined, these conditioning-exposed cells may be less proliferative than newly infused graft T cells. The depletion of graft T cells included CD4 and CD8 memory cells specific for infections, which may have contributed to relative deficits in protective immunity against infection in patients receiving PT-Cy. Importantly, these data suggest that with PT-Cy, persisting recipient TCRs may play a key role in preserving anti-infectious immunity. Taken together, these results provide a mechanistic basis for key post-transplant clinical outcomes of the landmark BMT CTN 1703 study. They also underscore the importance of recipient immune status with PT-Cy, creating the opportunity for targeted infection risk assessment in these patients.

Abstract Introduction: Outcomes for FL have markedly improved, and the 10-year (yr) overall survival (OS) for patients (pts) diagnosed in the rituximab era is about 80%. Historically, FL is the leading cause of death in the first decade after diagnosis (dx); however, modern outcomes beyond 10 yrs after dx remain unknown. Here we report long-term outcomes of FL from a large prospective cohort of pts with FL from the rituximab era. Methods: Pts with biopsy-proven FL 1-3A at dx were prospectively enrolled within 9 months of dx from 2002-2015 in the MER. Outcomes of interest were OS, event-free survival (EFS), histologic transformation (HT), and cause of death. HT was defined as subsequent biopsy-proven FL 3B, diffuse large B cell lymphoma, or high-grade B cell lymphoma. Analyses were performed using Cox models and KM curves; cause of death was evaluated using a competing risk approach. A subset analysis was performed in younger (18-59 yrs) vs older (60+ yrs) pts. A landmark analysis was conducted in pts alive at 10 yrs. Results: 1,155 pts with FL 1-3A were enrolled in the MER from 2002-2015. Median age at dx was 60 yrs (IQR 51-69). Clinical characteristics were: 67% stage III/IV, 12% grade 3A, 4% ECOG PS 2-4, and 19% elevated LDH. Initial management was 35% observation (obs), 12% R-monotherapy (R-mono), 39% immunochemotherapy (IC; 43% R-CHOP, 28% R-CVP, 27% BR), and 14% other. FLIPI scores were 40% low, 33% intermediate (int), and 27% high; FLIPI24 risk categories were 49% low, 25% int, and 26% high. At a median follow-up of 14 yrs (IQR 11-18 yrs), 751 events, 148 HTs, and 402 deaths were observed. EFS estimates (95% CI) were: 10-yr: 40% (37-43), 15-yr: 31% (28-35), and 18-yr: 27% (24-31). 15 yr & 18 yr EFS by initial txs were 22% (18-27) & 18% (14-25) for obs, 30% (23-40) & 18% (11-30) for R-mono, and 40% (35-46) & 38% (33-45) for IC. The incidence (95% CI) of HT was 12% (10-14) at 10 yrs, 13% (11-16) at 15 yrs, and 14% (12-17) at 18 yrs. OS (95% CI) for the entire cohort was 77% (75-80%) at 10 yrs, 63% (60-66) at 15 yrs, and 55% (51-59) at 18 yrs. The incidence of non-lymphoma-related death (non-LRD) surpassed lymphoma-related death (LRD) after 12 yrs in pts with known cause of death. Estimates (95% CI) for LRD were 11% (10-13) at 10 yrs, 14% (12-17) at 15 yrs, and 16% (14-19) at 18 yrs, while estimates for non-LRD were at 8% (7-10) at 10 yrs, 17% (15-20) at 15 yrs, and 22% (19-26) at 18 yrs. Among pts diagnosed before age 60, LRD remained the predominant cause of mortality into the second decade following dx, with incidences (95% CI) of LRD vs. non-LRD of 7% (5-9) vs 3% (2-4) at 10 yrs, 10% (8-13) vs 5% (3-8) at 15 yrs, and 13% (9-17) vs 6% (4-10) at 18 yrs, respectively. In patients age >60 non-LRD was the predominant cause of mortality in the second decade. Incidence of LRD vs. non-LRD in those aged ≥60 at dx were 15% (13-19) vs 13% (10-16) at 10 yrs, 18% (15-22) vs 28% (24-32) at 15 yrs, and 20% (16-24) vs 35% (31-41) at 18 yrs, respectively. In the landmark analysis of pts alive at 10 yrs from dx (n=720), median age was 69 yrs (IQR 60-77). 63 pts (9%) had HT prior to landmark. The median number of prior treatments was 1 (IQR 1-2, range 1-8). Risk of death (95% CI) was 19% (15-22) in the next 5 yrs (i.e. 15 yrs from dx) and 29% (24-33) in the next 8 yrs (18 yrs from dx). The risk of LRD vs non-LRD was 4% (3-6) vs 12% (9-15) at 5 yrs and 7% (3-9) vs 18% (10-23) at 8 yrs.Conclusions: Long-term outcomes for pts with FL remain excellent into the second decade from dx. HT risk decreases significantly after 10 yrs, though late HTs still occur. At 15 yrs from dx, 40% of pts remained alive and event-free after 1L IC. Nearly a quarter of pts observed at dx remained treatment-free. The most common cause of death after 10 yrs from dx was from non-lymphoma causes, notably in older pts aging into their 70s and 80s. While younger pts have a lower overall risk of LRD compared to older pts, FL represents the leading cause of death in this population during the second decade following dx. These results provide critical insights into the natural history of FL diagnosed in the modern era.

Abstract Introduction Heterozygous germline pathogenic variants (PVs) in the 5' untranslated region of ANKRD26 cause inherited thrombocytopenia and predisposition to hematologic malignancy (HM). The estimated lifetime HM risk is ~10% based on families ascertained from an inherited thrombocytopenia cohort. However, the malignancy spectrum, molecular features, precursor states, and overall clinical outcomes remain poorly defined. Methods We established an international, multicenter cohort of individuals with ANKRD26-related thrombocytopenia diagnosed after undergoing genetic evaluation due to a personal and/or family history of thrombocytopenia and/or HM. Clinical, pathologic, and molecular data were collected for 27 individuals with germline ANKRD26 PVs from 21 unrelated families treated at 11 institutions across 5 countries. Statistical analyses were performed using R (v4.4.2). Results Patients were predominantly male (18/27) and white (25/27). Thrombocytopenia was typically identified in childhood (median age 10 years, range 0-48) with a genetic diagnosis made later (median age 53 years, range 2-80). The mean (+/- SD) pre-malignancy platelet count was 45 +/- 24 K/uL (range 5-87). ANKRD26 PVs observed in each family included: c.-126T>C (n=9), c.-128G>A (n=3), c.-134G>A (n=3), c.-116C>T (n=3), c.-118C>T (n=2), and c.-118C>A (n=1). Thirteen HMs were diagnosed in 11 of 27 (41%) patients, including myelodysplastic neoplasm/syndrome (MDS, n=5), acute myeloid leukemia (AML, n=3), chronic myeloid leukemia (CML, n=2), MDS/myeloproliferative neoplasm (MPN) overlap (n=2), and Langerhans cell histiocytosis (n=1). The median age at first HM diagnosis was 63 years (range 49-80). Recurrent somatic features in myeloid malignancies included complex karyotype (4/11, 36%) and TP53 mutations (5/10, 50%). Of the 3 patients with AML, 1 achieved a partial remission (PR) with venetoclax combined with cladribine, idarubicin, and cytarabine but relapsed, 1 achieved a PR with azacitidine but relapsed <100 days after haploidentical allogeneic stem cell transplantation (alloSCT), and 1 had primary refractory disease. Among 5 patients with MDS, 1 was refractory to decitabine, 1 underwent alloSCT but relapsed 2 years post-transplant, 1 remains in remission post-alloSCT with 1 year of follow-up, 1 is undergoing alloSCT evaluation, and 1 was lost to follow-up. Both patients with CML achieved durable major molecular remissions with imatinib. To better estimate HM risk, we assumed 100% penetrance of thrombocytopenia for ANKRD26 PV carriers and included family members with chronic thrombocytopenia who had not had germline genetic testing. In this expanded series (n=62), 16 individuals developed a HM (26%). Additional diagnoses included MDS with progression to AML (n=1), AML (n=1), CML (n=1), and leukemia of unknown type (n=2). Cumulative incidence of HM was 0% by age 40 years, 17% by age 60 years, and 60% by age 80 years. Somatic sequencing of peripheral blood was performed in 5 HM-unaffected ANKRD26 PV carriers. One individual was found to have clonal hematopoiesis driven by TET2 (c.1648C>T, p.Arg550*) with a variant allele frequency (VAF) of 9% at age 55. Bone marrow biopsy showed mild megakaryocytic atypia and 4% blasts without overt evidence of malignancy. To assess the prevalence of ANKRD26-related HM, we assessed the frequency of ANKRD26 PVs in 2 large MDS/AML cohorts. In the ARUP database (9662 AML, 6397 MDS), 2 individuals (0.01%) had an ANKRD26 PV with a VAF consistent with germline origin. In the MSK-IMPACT Heme Germline MDS/AML cohort (n = 284), no ANKRD26 P/LP variants were identified. Conclusions Germline ANKRD26 PVs underlie <1% of MDS/AML diagnoses but may represent a high-risk subtype characterized by complex karyotype, TP53 mutations, and high risk of relapse. Among our series, the incidence of HM was low early in life but increased substantially with age, reaching 60% by 80 years. This exceeds prior estimates, which were derived from individuals ascertained from thrombocytopenia-based registries. Together, our findings suggest that ANKRD26-associated HM may represent a high-risk clinical entity, and that age and family history should inform surveillance strategies. More studies are needed to define genetic and environmental modifiers of HM risk as well as precursor states to enable early detection and disease interception.

Abstract Introduction FD Ibr+Ven is approved as first-line (1L) treatment (tx) for CLL/SLL in 78 countries across Asia, Europe, the Middle East, and South America, plus Australia, Canada, and New Zealand. Clinical trials with up to 5.5 years (yrs) of follow-up have demonstrated progression-free and overall survival benefits of 1L FD Ibr+Ven in pts with CLL/SLL (Wierda WG, ASH 2024; Jacobs R, EHA 2024). Despite established clinical benefits, there is a lack of RW evidence on the effectiveness and tolerability of FD Ibr+Ven outside of clinical trial settings. Here we present pooled data from REALITY-WW and REALITY-2 to understand the usage, factors for therapy decision, clinical response, and safety of FD Ibr+Ven in routine clinical practice. Methods REALITY-WW and REALITY-2 are prospective observational cohort studies. REALITY-WW is an international study; REALITY-2 is conducted in Germany. Both included previously untreated pts with CLL/SLL from hospitals and medical institutions where Ibr+Ven was routinely used. The decision to start FD Ibr+Ven was made prior to and independent of pt enrollment. Pts aged ≥18 yrs with a confirmed diagnosis of CLL/SLL requiring 1L tx per iwCLL 2018 criteria received 3 cycles of Ibr, followed by 12 cycles of FD Ibr+Ven orally (Ibr, 420 mg/d; Ven, 5-week ramp-up to 400 mg/d). Primary end point was overall response rate (ORR) per iwCLL 2018 criteria. Secondary end points and outcomes of interest included tx-emergent adverse events (TEAEs), tumor lysis syndrome (TLS) risk, and factors associated with physician decision to initiate FD Ibr+Ven in routine clinical practice. Results At data cutoff (REALITY-WW: May 2025; REALITY-2: March 2025), 129 pts from both studies received FD Ibr+Ven (REALITY-WW, 81; REALITY-2, 48). The median (range) time on study was 6.4 (0.1-19.0) months (mo). Median (range) age was 65.0 (37.0-87.0) yrs, with 46.5% of pts aged <65 yrs and 53.5% of pts aged ≥65 yrs; 62.8% were male. Median (range) time from diagnosis to FD Ibr+Ven initiation was 38.1 mo (0.1-238.0) and median (range) duration of tx was 6.0 mo (0.1-15.9) for Ibr and 3.2 mo (0.1-8.4) for Ven. A Cumulative Illness Rating Scale score of >6 was observed in 12.6% of pts, with a higher score in pts aged ≥65 vs <65 yrs (18.0% vs 6.9%). TP53 mutations were seen in 7.4% of pts; 52.8% had an unmutated IGHV status. ORR was assessed in the 44 pts with ≥ 1 post-baseline assessment in REALITY-WW. Of these, 39 showed a response by the end of 6 tx cycles (3 cycles of Ibr + 3 cycles of FD Ibr+Ven) and 5 had stable disease. ORR at 6 mo per iwCLL 2018 criteria (partial response [PR] with lymphocytosis [PR-L] or better) was 88.6% (95% CI, 79.3-98.0), including complete responses in 29.5%, PR in 34.1%, and PR-L in 25.0% pts. Among 129 treated pts, TEAEs were reported in 61.2%; diarrhea was the most common TEAE (14.0%). Serious TEAEs and grade 3/4 TEAEs were reported in 12.4% and 8.5% of pts, respectively. The most common grade 3/4 TEAE was myocardial infarction (1.6%). Dose reduction was observed in 13.2% (Ibr) and 2.3% (Ven) of pts, mainly due to tx-associated TEAE/toxicity/TLS. Rates of TEAEs leading to discontinuation, dose reduction, and interruption of ≥1 study tx were 4.7%, 10.9%, and 20.9%, respectively. At baseline (n=129), 18.6%, 45.0%, and 14.7% of pts had high, intermediate, and low TLS risk, respectively, while 20.2% were not assessed and 1.6% had missing data. After the 3-cycle Ibr lead-in, the distribution shifted to 9.3%, 24.8%, and 24.0%, respectively, with 14.7% not assessed and 27.1% missing. There were no TEAEs of TLS and no hospitalizations due to TLS. Seven pts (6 aged ≥65 yrs and 1 <65 yrs) were hospitalized prophylactically for TLS. Prophylactic hospitalization was observed in 8.5% (11/129) of pts with high or medium TLS risk and impaired renal function for whom the Ven ramp-up was initiated; no pts were hospitalized due to laboratory/clinical TLS during the Ven ramp-up period. Physician questionnaire responses (n=126) indicated the most common factors associated with decision to initiate FD Ibr+Ven were administration route advantage (91.3%), overall health status (87.3%), anticipated superior efficacy of tx (84.1%), and general risk factors such as high tumor burden/genetic risk factors (81.0%). Conclusions Overall findings suggest that FD Ibr+Ven is an effective and safe tx for pts with CLL/SLL in a RW population, including those aged ≥65 yrs. Data with longer follow-up will be presented at the meeting.