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Abstract INTRODUCTION Allogeneic hematopoietic cell transplantation (alloHCT) is indicated in patients (pts) with FLT3-ITD mutated AML. The randomized BMT CTN 1506 trial (Levis et al. JCO) demonstrated that maintenance with FLT3 inhibitor gilteritinib (gilt) significantly improved relapse-free survival (RFS) among pts with detectable peri-alloHCT minimal residual disease (MRD) but was also associated with a greater degree of myelosuppression and infections. In older pts, aged >60 years, increasing post-HCT toxicity may adversely impact outcomes. On this basis, we performed a post-hoc analysis of pts aged > 60 years enrolled onto BMT CTN 1506 to examine the impact of gilteritinib maintenance in older pts. METHODS Pts ≥60 years randomized on BMT CTN 1506 (gilt=47, placebo=57; N=104) were included. The primary endpoint of this post-hoc analysis was RFS. We additionally assessed overall survival (OS), incidence of relapse, non-relapse mortality (NRM) in all pts and in pts with detectable MRD. RESULTS Baseline characteristics were balanced. Age was similar (65.2 vs 64.7 years; p = 0.12), as was prior TKI exposure, and NPM1 mutation status. Myeloablative conditioning (MAC) was used in 8 (17%) pts randomized to gilt and 18 (32%) pts randomized to placebo (p=0.08). Median f/u of survivors was 43.8 months (range:1-61 mo.). Estimated RFS and OS at 48 months were not different between groups (RFS: gilt: 57.0%, 95%CI 44.1-73.7%, placebo: 57.1%, 95%CI 45.4-71.8%; OS: gilt: 56.9%, 95%CI 42.9-46.7%, placebo: 58.4%, 95%CI 46.7-73.1%). While gilt assignment did not affect survival, several predictors of poorer survival were identified including use of reduced intensity conditioning (RIC) (HR = 3.46; p = 0.014), use of calcineurin inhibitor/MTX for graft-vs-host disease (GVHD) prophylaxis (HR = 2.29; p = 0.041), high-risk cytogenetics (HR = 2.64; p = 0.021), and MRD (+) pre-HCT (HR = 2.29; p = 0.018). Finally, relative to gilt assignment, opposing rates of relapse and NRM were observed. The incidence of relapse was lower with gilt (16%, 95%CI 6.8-28% vs 32%, 95%CI 20-45%, p=0.046) but NRM was higher (27%, 95%CI 15-41% vs 11%, 95% CI 4.3-21%, p=0.033). We next analyzed the 49 pts (gilt=22, placebo=27) with detectable peri-HCT MRD. RFS and OS again were not different (RFS: gilt: 44.4%, 95%CI 27.1-72.7%, placebo: 43.8%, 95%CI 28.4-67.5%, OS: gilt: 49.2%,95%CI, 31.3-77.4%, placebo: 55.6%, 95%CI 39.4-77.8%). The incidence of relapse trended lower in gilt pts (25%, 95%CI, 5.3-44.7% vs 45% (95%CI, 25-63%), p=0.2) while NRM trended higher (31%, 95%CI 12-52% vs 11%, 95%CI, 2.7-26%, p=0.12). Seventeen (36%) patients completed planned 2 year maintenance with gilt compared to 29 (51%) completing therapy with placebo. Median time on gilt was 13.2 months. The most common reason for discontinuation was adverse events (n=19, 40%), of which cytopenias (n=8) and infections (n=4) were most frequent. Non-relapse causes of death among gilt treated pts included infections (n=8), intracranial hemorrhage related to thrombocytopenia (n=1), second cancer (n=1), and Guillain-Barre syndrome (n=1). Most infections (n=5) were attributed to GVHD as an underlying cause. CONCLUSION Among pts aged ≥60 years, gilt maintenance did not improve RFS or OS. Gilt use was associated with reduced relapse regardless of peri-HCT MRD status demonstrating disease effect; however, higher NRM limited overall benefit. In older FLT3 mutated pts, employing strategies to mitigate HCT related toxicity, e.g. alternative GVHD prophylaxis strategies, may better accommodate use of maintenance therapy including gilt. Lower doses of gilt (particularly with azole co-use) may be worth exploring to mitigate drug AEs, improve compliance, thus further improving benefit.

Abstract Background Hairy cell leukemia (HCL) is a rare, indolent B-cell malignancy accounting for ~1% of all lymphoid neoplasms. While purine analogs remain the standard first-line therapy, the increasing use of combination regimens and targeted agents has expanded the therapeutic landscape. Data on long-term outcomes in real-world practice remain limited. Methods This is a retrospective, multicenter cohort study. We included 104 patients aged ≥18 years with a diagnosis of HCL who had at least one oncology visit from January 1, 2010, to July 17, 2025. Patients diagnosed prior to 2010 were left-truncated to account for survivorship bias. Data were abstracted from electronic medical records. Key outcomes included treatment patterns, response rates, overall survival (OS), and progression-free survival (PFS). Results The median age at diagnosis was 56.9 years (range 32.1–83.8), and 80% were male. Most patients (77%) were diagnosed during or after 2010. The most frequent frontline therapies were cladribine (63%), cladribine with rituximab (12%), rituximab monotherapy (9.7%), vemurafenib-based regimens (7.7%), splenectomy with or without interferon (3.8%), interferon monotherapy (2.9%), and other (1.9%). The overall complete response (CR) rate to first-line therapy was 63%, with 15% achieving a partial response (PR) and 22% having stable or no response. For patients receiving cladribine with rituximab first-line (n = 12), 92% had a CR. For patients receiving cladribine monotherapy first-line (n = 65), 63% had a CR and 12% had a PR. For patients receiving rituximab monotherapy first-line (n = 10), 50% had a CR and 20% had a PR. For patients receiving vemurafenib-based regimens first-line (n = 8), 75% had a CR. Among the 39 patients who received second-line therapy, the most common regimens included cladribine (31%), rituximab (26%), cladribine plus rituximab (18%), and vemurafenib-based regimens (13%). The CR rate after second-line therapy was 72%. For patients receiving cladribine with rituximab second-line (n = 7), 86% had a CR and 14% had a PR. For patients receiving cladribine monotherapy second-line (n = 12), 67% had a CR. For patients receiving rituximab monotherapy second-line (n = 10), 80% had a CR and 10% had a PR. For patients receiving vemurafenib-based regimens second-line (n = 5), 40% had a CR and 20% had a PR. Among the 17 patients who received third-line therapy, the most common regimens included rituximab (41%), cladribine (18%), and vemurafenib-based regimens (18%). The CR rate after third-line therapy was 50%. For patients receiving rituximab monotherapy third-line (n = 7), 43% had a CR and 14% had a PR. For patients receiving cladribine monotherapy third-line (n = 3), 33% had a CR. For patients receiving vemurafenib-based regimens third-line (n = 3), 67% had a CR and 33% had a PR. Overall, treatment-related hospitalizations for first-line therapy occurred in 27% of patients. 50% of patients receiving first-line cladribine with rituximab had treatment-related hospitalizations. 25% of patients receiving first-line vemurafenib-based treatment had treatment-related hospitalizations. 23% of patients receiving first-line cladribine monotherapy had treatment-related hospitalizations. 20% of patients receiving first-line rituximab monotherapy had treatment-related hospitalizations. Overall, after a median follow-up of 6.6 years (range 0.1–46), estimated OS was 96.6% at 5 years, 85.7% at 10 years, and 80.3% at 15 years. The median OS was 24.5 years [95% CI: 18.3, not reached]. Estimated PFS was 95.1% at 1 year, 89.9% at 3 years, 74.8% at 5 years, and 50.8% at 10 years. Median PFS was 12.2 years [95% CI: 7.0, not reached]. Estimated OS for first-line cladribine monotherapy was 100% at 5 years and 86.5% at 10 years. Estimated OS for first-line vemurafenib-based treatment was 85.7% at 5 years and 85.7% at 10 years. Conclusions This large real-world cohort provides important insights into the long-term management of HCL. Cladribine-based regimens remain the predominant first-line approach, with high response rates and durable remissions. However, treatment-related toxicity is common. Outcomes in later lines remain favorable, particularly with re-treatment using purine analogs or combination regimens. These findings underscore the importance of individualized treatment planning and the continued need for real-world evidence to inform care in rare hematologic malignancies.

4545 Background: The treatment landscape of front-line nccRCC has evolved with recent trials demonstrating the efficacy of combination systemic therapy. However, the efficacy of treatment after combination therapy is unknown. This study evaluates the efficacy of VEGF-based regimens in nccRCC patients (pts) previously treated with combination regimens. Methods: ORACLE is a real-world, multi-center, retrospective database that includes nccRCC patients that received combination systemic therapies (IO+IO, IO+VEGF and VEGF+ mTOR) in any line. Subsequent treatments were categorized as VEGF only regimens (cabozantinib vs other VEGF), IO+ VEGF and VEGF+ mTOR. The primary endpoint was objective response rate (ORR) assessed by investigator review using RECIST 1.1. Secondary endpoints included disease control rate (DCR), defined as the proportion of patients achieving complete or partial responses or stable disease, time to treatment progression (TTP), calculated from the date of VEGF-based initiation to progression or last follow-up using the Kaplan-Meier method. Differences between groups were estimated with the log-rank test, and categorical outcomes were compared with the chi-square test. Results: 105 pts who received VEGF – based regimens after combination therapy were included in the analysis. Baseline characteristics: median age: 59years, 71 % male, 58% white, 25% black, 87% ECOG 0-2. IMDC-risk categories included:21% favorable, 59% intermediate and 20% poor risk. Histology included papillary (40%), unclassified (32%), chromophobe (16%) and other rare subtypes (12%). Prior combination therapies included IO+IO: 62%, IO+ VEGF: 34% and VEGF+ mTORi:4%. 70% pts received combination therapy in the first line setting while the remainder received combination therapy in a second or later line. Outcomes with subsequent treatments are described in Table1. IMDC risk score correlated with TTP. Conclusions: Modest antitumor activity was observed with VEGF- based approaches in combination therapy refractory nccRCC. Optimal management of nccRCC remains an unmet need. Outcomes of nccRCC patients by treatment and histologic type. Outcomes per Treatment n ORR (%) DCR (%) mTTP (mo.) Cabozantinib 56 18 47 3.6 VEGF/mTOR 19 16 42 9.3 IO+VEGF 17 29 47 5.6 Other VEGF 13 15 46 5.5 Outcomes per Histology Papillary 42 19 43 6.5 Unclassified 33 21 42 6.1 Chromophobe 17 29 59 8.9 Other * 13 0 46 NR

Background Polyclonal autologous T cells that are epigenetically reprogrammed through mTOR inhibition and IFN-α polarization (RAPA-201) represent a novel approach to the adoptive T cell therapy of cancer. Ex vivo inhibition of mTOR results causes a shift towards T central memory (TCM) whereas ex vivo IFN-α promotes type I cytokines, with each of these functions known to enhance the adoptive T cell therapy of cancer. Rapamycin-resistant T cells polarized for a type II cytokine phenotype were previously evaluated in the allogeneic transplantation context. Methods The clinical trial (NCT04176380) evaluated RAPA-201 therapy in combination with fludarabine-sparing low-dose host conditioning for the treatment of patients with relapsed, refractory multiple myeloma (RRMM). Results From December 2020 to December 2022, 14 patients with RRMM received a median of three RAPA-201 infusions (median dose, 80×106 cells). RAPA-201 drug products (DPs) were: polyclonal; enriched for TCM cells; reduced for immune checkpoint expression, including PD1, CD73, and LAIR1; and preferentially secreted Th1 cytokines. The median chemotherapy dose administered per cycle was 1,817 mg total for cyclophosphamide (range, 1,100–2,200) and 2.35 mg/M2 for pentostatin (range, 0–16). Nine of 14 patients (64%) achieved disease remission, with eight partial responses and one stringent complete response. Median progression-free survival was 6.0 months (range, 2.1 to>16.8 months). There were no toxicities of any grade attributable to RAPA-201, including no cytokine release syndrome and no immune effector cell-associated neurotoxicity syndrome. Only 4 of 14 patients (29%) had a serious adverse event (≥ grade 3) of any attribution. Conclusions Consistent with our hypothesis, ex vivo manufacturing using mTOR inhibition and IFN-α polarization consistently yielded a novel RAPA-201 DP that possessed a desirable phenotype relative to cytokine phenotype, memory status, and checkpoint expression. RAPA-201 recipients had preservation of T cell counts and Th1 cytokine secretion yet had increased T cell receptor clonality that associates with antitumor responses in the setting of monoclonal antibody checkpoint therapy. RAPA-201 therapy overcomes previous barriers to effective autologous polyclonal T-cell therapy, as it is feasible to manufacture, exquisitely safe to administer, and mediates remission in patients with RRMM. Trial registration number ClinicalTrials.gov: NCT04176380.

Background: Hypomethylating agents (HMA) with venetoclax (VEN) have shown encouraging clinical efficacy in single arm clinical trials for patients with myelodysplastic syndrome (MDS) (Garcia JS et al. ASH 2023, Zeidan AM et al. Am J Hematol. 2023). Many centers have started utilizing HMA-VEN in the clinical management of MDS due to unmet need, pending results of the ongoing phase 3 randomized clinical trial (VERONA) using this combination. However, real world studies with large sample size investigating the use of these agents in MDS, practice patterns and clinical outcomes are lacking. Methods: This is a multicenter retrospective study of 13 US academic medical centers. We included contemporary cohorts of adults (age≥18 years) with MDS who were treated with upfront combination of HMA-VEN, upfront HMA monotherapy, or VEN added after inadequate response or progression on HMA (post-HMA failure VEN). Outcomes analyzed includes clinical response, adverse events (AE) of interest, dose administration and survival. Descriptive statistics were used for baseline characteristics. Overall survival and event free survival (EFS: progression, leukemic transformation, death as events) analysis was conducted using Kaplan-Meier method. Determinants of outcomes were analyzed using multivariable regression models. All analyses were conducted at a significance level of p<0.05. Results: Among 454 patients included, 258 patients received VEN in combination with HMA [upfront HMA-VEN (n=175), post-HMA failure VEN (n=83)] and 196 patients received HMA monotherapy. Median age was 69 (59-77) years and majority of patients had MDS with excess blasts (75%), high risk (31.9%) or very-high (41.8%) risk disease by IPSS-R, 23.7% had therapy related disease, 33% had deletion17p or TP53 mutation and 40.9% underwent allogeneic stem cell transplantation. VEN was predominantly started in outpatient setting (78.6%) with tumor lysis syndrome (TLS) prophylaxis and VEN doses ranged from 70-400mg, adjusted for concomitant antifungal drugs. Incidence of TLS was minimal (No TLS- 92.9%, lab-only TLS 6.2%, 1 pt with clinical TLS). Neutropenic fever was the main AE noted [upfront VEN-HMA (34.2%), HMA monotherapy (22.5%), post-HMA VEN (44.5%)]. In the upfront setting, response rate was significantly higher with HMA-VEN than HMA monotherapy (CR: 33% vs 12%; marrow CR: 40% vs 27%, p<.001). VEN given in the post HMA failure setting also resulted in encouraging response rates (CR 10%, marrow CR 32%). After adjusting for covariates in multivariable analysis, patients treated with HMA-VEN in the upfront setting had significantly improved event free survival as compared to HMA monotherapy (HR 0.59, HR 0.44-0.78, p<0.01), but overall survival did not reach statistical significance (overall survival HR 0.77, 95%CI 0.57-1.04, p=0.08). Conclusions: In this large multicenter retrospective analysis from US academic medical centers, we found that VEN in combination with HMA resulted in encouraging clinical outcomes and was effectively administered in the outpatient setting with minimal TLS. Infection risk management and supportive measures would be important to improve the ability to use this treatment widely, pending results of the ongoing phase 3 randomized clinical trial. Updated results with additional variables will be available at the main meeting.

Background: Acute promyelocytic leukemia (APL) is one of the most treatable leukemias in the current era, with cure rates upwards of 90%. Early mortality due to coagulopathies often seen at diagnosis is a major driver of adverse outcomes. Prompt initiation of all-trans retinoic acid (ATRA) is crucial for suspected APL, as it is known to reverse these coagulopathies. Chemotherapy-free protocols consisting of arsenic trioxide (ATO) and ATRA have become the standard of care for low-risk APL with high cure rates and reduced hematologic toxicities. For high-risk disease, there are multiple treatment options that have not been compared. Since APL is rare, there is a lack of real-world data for this disease. This retrospective review aimed to assess the outcomes of APL patients (pts) across multiple institutions and to examine the most common induction regimens, characteristics linked to early (30-day) mortality, and supportive care strategies. Methods: This retrospective study involved 9 institutions in the US and was conducted through the Consortium on Myeloid Malignancies and Neoplastic Diseases (COMMAND). Data included pts admitted from 8/5/2006 through 2/3/2024 with a confirmed diagnosis of APL. Each institution received a data-collection form and contributed data on APL pts from presentation to last follow-up. Key data categories included patient demographics, presenting laboratory and molecular data, treatment regimen, supportive care, and patient outcomes. Results: Data for 412 pts were identified with a median age of 51 (range 17-90) and 49% were female. Cardiovascular comorbidities were present in 44% of pts and 16% had a known pulmonary comorbidity. At presentation 109 (27%) had high risk-disease, defined as a white blood cell count (WBC) greater than 10 x 109/L. A FLT3 mutation was seen in 50% of tested pts, WT1 (22%), KRAS (3.6%), and NRAS (6.5%). The median WBC at presentation was 2 x 109/L (range: 0-166 x 109/L) and the median platelet count was 27 x 109/L (range: 2.0-315 109/L). Twenty-six percent presented with grade 2+ thrombosis, bleeding, or both. A higher percentage of pts with high-risk vs. low-risk disease presented with grade 2+ thrombosis, bleeding, or both (43% vs. 20%), DIC (60% vs. 36%), and mutated FLT3 (81% vs. 37%). The majority of pts received a chemotherapy-free induction regimen consisting of ATRA plus ATO. It was determined that 36 (8.7%) pts received induction with intermittent ATO plus ATRA (Burnett AK, Lancet Oncol 2015), 276 (67%) received daily ATO plus ATRA (Ravandi F, J Clin Oncol 2009 and Lo Coco, NEJM 2013), and 70 (17%) received a regimen inclusive of an anthracycline plus ATRA. Eleven pts did not start an induction regimen other than single-agent ATRA due to early death, while 19 had their regimen classified as “other” because they did not follow a conventional induction path. In total, 295/358 (82%) received ATRA within 24 hours of admission. At least 1 dose of gemtuzumab ozogamicin was given to 58 (14%) pts, of which 35 (60%) were considered high risk. The incidence of differentiation syndrome (DS) was 37% (n=154). Among the 243 pts who received steroid prophylaxis, 30% developed DS, compared to 52% of those who did not receive prophylaxis. Among the 360 pts with at least 1 available PCR result after starting induction, 94% achieved PCR-negativity. The 30-day mortality rate was 6.6%. On univariate analysis, presenting variables associated with a higher 30-day mortality include older age, diabetes, cardiovascular comorbidities, thrombosis or bleeding, DIC, eGFR < 60, elevated total bilirubin and D-dimer levels, and high-risk disease. The median overall survival (OS) of the cohort was not reached, and the 5- and 10-year OS was 88% (95% CI: 84-91%) and 79% (95% CI: 72-87%) respectively. The cumulative incidence of relapse at 3 years was 2.7% (95% CI: 1.4 - 5.1%), with no additional relapses observed. The incidence of CNS relapse at 3 years was 0.9% (95% CI: 0.3% - 2.8%), with 2 of the 4 pts classified as high-risk. Conclusion: This is the largest real-world evidence data collection in the US evaluating the outcome of pts with APL in the current era, inclusive of ATO as front-line induction. Outcomes for this disease remain extremely positive, with low 30-day mortality rates noted in this study along with durable OS rates and low incidence of relapse. Additional information on outcomes, safety, and supportive care will be presented at the meeting.

Summary Chimeric antigen receptor T‐cell (CAR‐T) therapy and bispecific T‐cell engagers (BsAb) have emerged as promising immunotherapeutic modalities in patients with relapsed and/or refractory multiple myeloma (RRMM). However, there is limited data on the safety and efficacy of CAR‐T and BsAb therapies in MM patients with a prior history of allogeneic transplantation (allo‐HCT). Thirty‐three MM patients with prior allo‐HCT received CAR‐T ( n = 24) or BsAb ( n = 9) therapy. CAR‐T therapy demonstrated an ORR of 92% (67% ≥ CR), and 73% were MRD negative. BsAb therapy resulted in an ORR of 44% (44% ≥ CR) and 44% MRD negative. Safety analysis showed grade ≥3 AEs in 92% of CAR‐T and 56% of BsAb patients. Cytokine release syndrome (CRS) occurred in 83% of CAR‐T and 78% of BsAb recipients, while immune effector cell‐associated neurotoxicity syndrome (ICANS) was observed in three CAR‐T patients. Infections of grade ≥3 were reported in 50% of CAR‐T and 44% of BsAb recipients. No exacerbation of graft‐versus‐host disease occurred except in one BsAb recipient. CAR‐T and BsAb therapies appear to be feasible, safe and provide deep and durable responses in MM patients with prior allo‐HCT.