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Key Points The kidney microvasculature was quantified reliably in human autosomal dominant polycystic kidney disease early on, using super-resolution ultrasound localization microscopy. Microvascular parameters correlated with structural and functional indices, constituting promising biomarkers to evaluate noncystic parenchyma. Microvascular parameters may serve to assess disease severity and monitor progression from the early stages of the disease. Background In vitro studies in individuals with autosomal dominant polycystic kidney disease (ADPKD) have shown extensive intrarenal microvascular remodeling. However, analyses have been limited to the time of kidney failure because of the invasive nature of current methodologies to assess the intrarenal microvasculature. We hypothesized that super-resolution ultrasound microvascular imaging, known as ultrasound localization microscopy, enabled by high-framerate ultrasound imaging and microbubble localization and tracking postprocessing techniques, would safely, reliably, and reproducibly assess the intrarenal microvasculature in individuals with ADPKD at an early stage of the disease. Methods We prospectively enrolled young (<40 years of age), well-characterized, early-stage (eGFR >90 ml/min per 1.73 m 2 ) individuals with ADPKD, and sex–age 1:1 matched controls ( n =17 each) and assessed the intrarenal microvasculature using ultrasound localization microscopy. We determined the intersonographer reliability, intraobserver repeatability, and interobserver reproducibility of microvascular parameters in both groups, and the day-to-day variability in the control group. Microvascular parameters were correlated with structural (total kidney volume) and functional (eGFR) markers in individuals with ADPKD. Results Ultrasound localization microscopy provided a super-resolved map of the intrarenal microvasculature in ADPKD and matched controls. Intrarenal microvascular parameters ( e.g ., vessel density) were quantified in a safe, reliable (intraclass correlation coefficients, 0.96; 95% confidence interval, 0.91 to 0.98), reproducible (intraclass correlation coefficient, 0.96; 95% confidence interval, 0.93 to 0.98), and repeatable (coefficient of variations, 3.6%) manner. In control individuals, the day-to-day variability of most parameters was low, with coefficient of variation ranging from 1.8% to 10.7%. Microvascular parameters differed in individuals with ADPKD compared with controls, despite preserved eGFR. Interestingly, cortical vessel density and its derived perfusion correlated directly with eGFR, whereas tortuosity indices presented an inverse correlation. Conclusions Ultrasound localization microscopy provided a safe and reliable in vivo assessment of the human intrarenal microvasculature.

Abstract Venetoclax (Ven) in combination with hypomethylating agents (HMA) is widely used as frontline treatment in older or unfit patients with acute myeloid leukemia (AML). Liposomal cytarabine and daunorubicin (CPX-351) is FDA-approved for the treatment of secondary AML, including therapy-related (t-AML) and AML with myelodysplasia-related changes (AML-MR). The current study aimed to provide a comprehensive comparison between the two treatment strategies to better inform clinical decisions. Methods The current retrospective analysis was performed under an institutional review board approved minimal risk protocol at Mayo Clinic (MN, AZ, FL). AML-MR gene mutations or cytogenetic abnormalities were categorized according to the International Consensus Classification (Arber et al. Blood 2022;140:1200). Treatment response was assessed according to the 2022 European LeukemiaNet (ELN) criteria (Dohner et al. Blood 2022;140:1345). Overall survival (OS) analysis was censored for allogeneic stem cell transplant (ASCT). Statistical analyses were performed using JMP Pro (Version 18.0.0). Results A total of 600 patients with newly diagnosed AML (ND-AML) treated with CPX-351 (N-112, 19%), or Ven-HMA (N=488, 81%) were included. AML subtypes included de novo (N=277, 46%), post-myelodysplastic syndrome (post-MDS, N=114,19%), post-myeloproliferative neoplasm (post-MPN, N=70, 12%), post-MDS/MPN (N=36, 6%), t-AML (N=103, 17%) and AML-MR (N=274, 46%). Compared with those treated with Ven-HMA, patients receiving CPX-351 were younger (median age 65 vs 73 years; p&lt;0.01), more likely to be female (50% vs 38%; p=0.02), more frequently diagnosed withsecondaryAML (68% vs 51%; p&lt;0.01), and less likely to have NPM1MUT (5% vs 12%; p=0.02) whereas ELN 2022 cytogenetic risk distribution was similar between the two (adverse risk; 43% vs 40%; p=0.5). Comparison of treatment response and survival Complete response rates with (CR) or without (CRi) count recovery were similar between CPX-351 and Ven-HMA overall (55% vs 60%) as well as specifically in patients with AML-MR (60% vs 63%), adverse karyotype (44% vs 44%), NPM1MUT (100% vs 89%), TP53MUT(32% vs 45%), IDH1MUT (60% vs 76%), IDH2MUT (63% vs 77%), SF3B1MUT(71% vs 45%), and CBLMUT (33% vs 69%) [p&gt;0.05 in all instances]. Compared to those with CPX-351, CR/CRi rates with Ven-HMA were superior in males (60% vs. 45%; p=0.04) and in patients with de novo AML (68% vs. 50%; p=0.03), STAG2MUT (86% vs. 44%; p=0.02), or CEBPAMUT (88% vs. 50%; p=0.03); infectious complications were significantly more frequent with CPX-351 (83% vs 62%, p&lt;0.01). At a median follow-up of 12 months (range; 1-88), 416 (69%) deaths, 179 relapses (44% in CPX-351 and 52% in Ven-HMA responders) and 149 ASCTs (53% in CPX-351 and 18% in Ven-HMA) were documented. OS rates were similar between CPX-351 and Ven-HMA, in general (median 10 vs 13 months), as well as in patients with adverse karyotype, TP53MUT, IDH1MUT, and IDH2MUT (p&gt;0.05 in all instances). By contrast, OS was superior in Ven-HMA-treated patients with post-MDS AML (median 12 vs. 7 months; age-adjusted p=0.02) and in CPX-351-treated patients harboring SF3B1MUT(median not reached vs 14 months; age-adjusted p&lt;0.01). In addition, a borderline-significant OS advantage for CPX-351 was apparent in patients with PTPN11MUT (13.5 vs 8 months; p=0.08). Comparison in ICC defined AML-myelodysplasia-related CR/CRi and OS rates were comparable between patients treated with CPX-351 (N=57) or Ven-HMA (N=217), with response rates of 60% vs 63% (p=0.68) and median OS of 10 vs 14 months (p=0.61), respectively. However, OS was superior with Ven-HMA in patients with post-MDS AML (15 vs 8 months; age-adjusted p=0.02) and with CPX-351 in those with SF3B1MUT (NR vs 14 months; age-adjusted p=0.02). Conclusions: The current study suggests that Ven-HMA was as effective and possibly less toxic than CPX-351 for the treatment of ND-AML, including AML-MR, despite the bias for younger and fitter patients treated with the latter regimen. Observed differences involving patients with SF3B1MUT or post-MDS AML require validation in prospective studies and provide parameters for developing treatment-specific predictive models that will be presented at the meeting.

Abstract Background: TP53-mutated myeloid neoplasms (MNs) represent one of the most lethal subgroups of blood cancers. The World Health Organization (WHO-5) recognize TP53-mutated (TP53mut) myelodysplastic syndrome (MDS) and International Consensus Classification (ICC) recognize TP53mut MDS and acute myeloid leukaemia (AML) as distinct disease entities, acknowledging their dismal prognosis and the urgent need for novel therapeutic strategies. However, key discrepancies exist between the classifications, creating uncertainty in diagnosis, influencing therapeutic decisions, and complicating clinical trial enrolment for patients with uniformly poor survival. Importantly, neither classifications included TP53-mutated myelofibrosis (MF), other myeloproliferative neoplasms (MPN), and MDS/MPN overlap syndromes, despite growing evidence that these cases carry similar adverse outcomes. To address these critical gaps, we conducted a comprehensive analysis across the full spectrum of TP53-mutated MN. Methods: We included TP53mut cases with variant allele frequency (VAF ≥2%) of AML, MDS, MDS/MPN overlap, myelofibrosis and other MPN managed at the Mayo clinic (Rochester, USA) and Local Health Network in South Australia (Australia). Cases were classified according to the revised 4th edition WHO classification (WHO-4R). Biallelic TP53 loss was defined as: (i) ≥2 mutations with VAF ≥2%; (ii) single TP53mut with VAF ≥2% plus 17p loss on karyotype, FISH, or SNP array; or (iii) single TP53mut with VAF ≥50% with or without 17p loss. Monoallelic loss was defined as a single TP53mut with VAF &lt;50% without 17p loss or copy neutral loss of heterozygosity. The primary endpoint was overall survival (OS) from diagnosis, censored at allogeneic transplantation. Conditional inference tree analysis was performed to define the effect of individual predictors on OS. Results: We identified 853 TP53mutMN cases including WHO-4R-defined AML (BM/PB blasts ≥20%, n=314; 36.8%), MDS with excess blasts-2 (EB-2; BM 10–19% or PB 5–19%, n=129; 15.1%), MDS-EB-1 (BM 5–9% or PB 2–4%, n=100; 11.7%), and MDS with low blasts (LB; BM &lt;5% and PB &lt;1%, n=228; 26.7%). MF included chronic phase (MF-CP, n=48; 5.6%), accelerated phase (MF-AP, n=7; 0.8%), and blast phase (MF-BP, n=17; 2.0%). Additional cases comprised other MPN-chronic phase (n=3, 0.4%) and MDS/MPN overlap syndromes (n=7, 0.8%). Of 848 evaluable TP53mut MN, 616 (72.6%) harbored biallelic TP53 loss and 232 (27.4%) had monoallelic loss, with 42.4% (n=98) of monoallelic cases harboring a complex karyotype (CK). Biallelic loss was highly prevalent in AML (83.1%), MDS (70.4%), and MDS/MPN overlap (71.4%), but was less frequent in cases with MPN (33.3%) and MF-chronic phase (25.0%). Across the spectrum, the frequency of biallelic loss increased stepwise with disease progression, rising from MDS-LB (62.8%) to MDS-EB1 (76.0%), MDS-EB2 (79.5%), AML (83.1%), and MF-AP/BP (79.2%) (P&lt;0.0001). In multivariable analysis, WHO-4R category, TP53mut VAF, biallelic loss and CK were independent predictors of poor survival in TP53mut MN. Conditional inference tree analysis stratified the cohort into seven prognostic groups with distinct median OS: (1) AML, MF-BP/AP, and MDS/MPN overlap regardless of mono/biallelic and CK status (n=335, 39.7%; median OS 4.0 months); (2) MDS-EB1/EB2 with biallelic loss or monoallelic plus CK (n=212, 25.1%; 7.2 months); (3) MDS-LB, MF-CP and MPN with CK (n=156, 18.5%, OS 10.2 months); (4) biallelic MDS-LB (n=28, 3.3%; OS 15.6 months), (5) monoallelic MDS-EB1/EB2 without CK (n=20, 2.4%; OS 26.2 months), (6) monoallelic MDS-LB without CK (n=57, 6.7%; OS 33.4 months), and (7) MF-CP and other MPN without CK (n=36, 4.3%; OS 37.0 months). This analysis defines a clear stepwise risk gradient, identifying subsets with extremely poor prognosis versus a relatively indolent disease. Conclusions: This is the first study to evaluate the prognostic impact of TP53mut MN across the entire MN spectrum, providing a framework for future refinement of TP53-driven disease classification. Key findings include: (i) MF-AP/BP and MDS/MPN overlap exhibit survival outcomes as dismal as AML, irrespective of the TP53 allele status; and (ii) complex karyotype is a surrogate for “biallelic equivalent”, refining risk interpretation in monoallelic cases. Overall, our study defines seven prognostic subgroups spanning all TP53mut MN, offering a foundation for risk-adapted clinical trial design and future classification updates.

Abstract Introduction Matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS, mass fix) represents a sensitive and specific alternative to electrophoresis and immunofixation for quantifying monoclonal antibodies in patients with multiple myeloma (MM). Here we report real world data utilizing mass fix and compare its test characteristics to a gold standard of minimal residual disease (MRD) quantification utilizing next generation sequencing (NGS). Results All patients who had obtained mass fix and MRD testing by NGS as part of routine clinical care at Mayo Clinic Arizona were screened for this study. In total, 343 pairs of mass fix and NGS testing within 50 days of each other representing 269 unique patients with secretory multiple myeloma were included. Cases of IgD myeloma and those secreting only free light chains were excluded. The threshold of MRD negativity was set at &lt;1x10-6(less than one malignant cell in one million) and was assessed utilizing the clonoSEQ NGS assay. The median age of our cohort is 67, it is 44% female, and primarily Caucasian (88%) with a median follow-up of 7.3 months from testing date. FISH testing was performed in 96% of patients and at least one high risk cytogenetic abnormality (t(4;14), t(14;16), del(17p)) was found in 23% of patients. The t(11;14) translocation was found in 18%, +1q in 26%, and amp(1q) in 6% of evaluated patients. Notably, patients at all stages of treatment or disease status were included in our study. Induction treatment for newly diagnosed MM (NDMM, 133 patients) was mostly daratumumab-containing quadruplet (63%) or triplet drug regimens (36%). Autologous stem cell transplant (ASCT) was performed in 79% of NDMM and 80% of relapsed refractory MM patients (RRMM, 138 patients). Of the RRMM patients, 94% were triple class exposed and 41% were penta-exposed. Overall agreement between NGS and mass fix results was 65% (Kappa statistic: 0.31, 95% CI: 0.22 – 0.41). Most discordant cases were instances of mass fix negativity and NGS positivity (n = 89, 26% of all testing pairs). Only 7% of cases (n= 30) represented mass fix positivity with NGS negativity. Mass fix was able to define therapeutic monoclonal antibody by its unique mass spectrometric profile in 38 of the total test pairs that otherwise would have been considered disease associated. Of the 30 patients testing mass fix positive and NGS negative, 25 (83%) represent post-treatment evaluations. Thus, ongoing mass fix positivity represents monoclonal protein washout kinetics. All of these cases are noted to have declining mass fix levels at last follow up and 40% had undetectable monoclonal protein. The discordant mass fix negative and NGS positive cases were evenly distributed across NDMM and RRMM representing 32% and 20% of test pairs in each group, respectively. Amongst these 89 total test pairs, the median abundance of malignant clone by NGS was 10 cells per million (range 0.06 to 297,895). This is in contrast to 136 concordantly positive test pairs where the median was 2960 cells per million (range 0.353 to 1,017,360). The median monoclonal protein identified (in those with a quantifiable M-spike) was 0.30 g/dL. Receiver operating characteristic curves using NGS as gold standard found the optimal mass fix threshold to be 0.010g/dL (specificity 95%, sensitivity 51%) for NDMM patients and 0.046g/dL (specificity 84%, sensitivity 55%) in RRMM patients. Conclusions Development of a MRD assay based on peripheral blood sampling could greatly improve the ease and speed of obtaining these assessments. Our experience highlights both the great potential and need to identify appropriate clinical contexts for optimal use of mass fix MRD assessment. A significant limitation of our data is that low level monoclonal proteins without a previous reference above a threshold of 20mg/dL are not reported as positive and may account for a significant fraction of discordant cases reported here. All clonoSEQ NGS samples are referenced to a positive control greatly increasing specificity. The currently reported dataset is biased against mass fix as not all test pairs reported are known to have a positive reference. Further delineation of these cases is forthcoming. Previous reports have also noted that mass fix test characteristics can improve with time from treatment which will be assessed with future follow-up.

Abstract Background: KMT2A-rearranged acute myeloid leukemia (KMT2Ar AML) is characterized by chromosomal translocation involving KMT2A gene at 11q23, resulting in fusion with variety of partner genes. It is usually associated with poor outcomes, high risk of relapses and suboptimal responses to conventional therapies. While NPM1-mutated (mt) AML is considered favorable risk, they are equally dismal in relapse refractory (RR) setting. Menin inhibitors have emerged as a promising therapeutic strategy, particularly in RR AML patients (pts) with KMT2Ar and NPM1-mt genotypes. While revumenib, a menin inhibitor approved for managing RR KMT2Ar acute leukemia, no menin inhibitor is currently approved for NPM1-mt AML. In this study, we evaluated clinical outcomes of adults with KMT2Ar AML and performed a comparative analysis of pts with RR KMT2Ar and NPM1-mt AML using data from the Mayo Clinic. Methods: After screening 102 AML pts with reported KMT2A abnormalities, we identified 33 adults with confirmed KMT2Ar diagnosed between 2012 and 2024 for retrospective analysis. Clinical and molecular/cytogenetics data, induction type (intensive chemotherapy [IC] vs non-intensive chemotherapy [NIC]), response, transplant use, and survival outcomes were reviewed. A separate analysis was performed comparing 20 RR KMT2Ar AML pts with 20 propensity score matched RR NPM1-mt AML pts from a pool of 125 NPM1-mt RR pts. Results: The median age was 50 years (yrs) (range [R], 19.0-75.0), and 60.6% were &lt; 60 yrs. Most cases were de novo AML (64%), and the most frequent translocation was t(6;11)(q27;q23)/MLLT4 (27%), followed by t(10;11)(p12;q23)/MLLT10 (21%), t(9;11)(p21.3;q23.3)/MLLT3 (15%), and t(11;19)(q23;p13.1)/ELL (12%). Other KMT2A fusion partners were rare and collectively accounted for the remaining cases. The median follow-up was 57 months (mo) (R, 7.0-109.0). The overall response rate (ORR) was 91%, and composite complete remission (CRc, , including CR, CRi, and CRh) was 73%. The CRc rates were comparable between IC and NIC (80% vs 62%, p=0.24). CRc were not significantly different by disease type (de novo [71.4%] vs secondary [sAML] [75%], p= 0.82) or KMT2A fusion partner gene (60% for t[9;11]/MLLT3 vs. 57.1% for t[10;11]/MLLT10 vs 55.6% for t[6;11]/MLLT4, p=0.069). Seventeen (52%) pts received an allogeneic stem cell transplantation (allo-HCT). The median overall survival (mOS ) for the entire cohort was 16 mo (R, 11.0-34.0). In subset analysis, IC compared to NIC was associated with significantly longer mOS (30 vs 11 mo, p=0.014). The mOS was also superior in pts &lt;60 vs ≥60 yrs (32 vs 8 mo, p=0.005). Similarly, de novo cases had better mOS than sAML (22.0 vs 9.5 mo, p=0.052). Among KMT2Ar subtypes, t(6;11)/MLLT4 showed the longest mOS (54 mo [R, 30.0-not reached (NR)]), while t(9;11)/MLLT3 had the shortest (11.0 mo, [R 9-NR]), but differences were not statistically significant (p=0.32). The mOS was significantly longer among allo-HCT pts (30 vs 11 mo, p=0.005). Among 29 pts who experienced RR disease, the median relapse free survival (RFS) was 3 mo (R, 2.0-10.0). First salvage therapy yielded a CRc of 43.8% in 16 evaluable pts. When compared to a propensity matched cohort of 20 RR NPM1-mt AML pts, the CRc rates was 57.9% vs 50% in RR NPM1-mt and KMT2Ar AML (p= 0.68). The mRFS was not significantly different between RR KMT2Ar and NPM1-mt AML, (3 vs 4 mo, p=0.9). However, KMT2Ar pts had inferior mOS compared to NPM-mt AML (12 vs 65 mo, p=0.004). We further compared survival between NPM1-mt and KMT2Ar pts stratified by allo-HCT status. Among those who underwent allo-HCT, NPM1-mt pts had longer mOS (NR vs 22 mo, p=0.037). Among non-allo-HCT pts, mOS was numerically higher in NPM1-mt vs KMT2Ar (19 vs 8 mo, p=0.11). Conclusions: This single institusion cohort of adult AML with KMT2Ar underscores the biological and clinical heterogeneity of this high-risk group. IC was associated with a survival benefit, particularly among younger and fit patients. However, the outcomes following relapse remained poor, highlighting the urgent need for improved post-remission and salvage therapies. Comparative analysis with matched RR NPM1-mt AML pts revealed similarly dismal survival outcomes. Emerging data from single-arm studies of menin inhibitors in both frontline and RR settings among pts with NPM1-mt and KMT2Ar AML are encouraging and may represent a paradigm shift in treatment.

Abstract Introduction: Primary central nervous system T-cell lymphoma (PCNSTL) is a rare form of PCNSL, comprising 2–8% of cases. Prognostic factors remain undefined, and no standard treatment protocol currently exists. Prior studies have been limited by small sample sizes, incomplete molecular profiling, and poor representation of novel treatment modalities. In this study, we aimed to identify clinicopathologic factors associated with patient (pt) outcomes and delineate the spectrum of treatment regimens used to inform future clinical practice. Methods A multicenter retrospective study was conducted across 15 North American academic institutions. Pts aged ≥18 years with biopsy-confirmed PCNSTL between 2009 and 2025 with no evidence of systemic disease were included. Cases with CNS relapse of systemic T-cell lymphoma were excluded. Baseline characteristics were analyzed using independent t-tests, Fisher's exact tests, or Pearson's chi-square tests. Primary endpoints were overall survival (OS) and progression-free survival (PFS), evaluated by Kaplan–Meier, log-rank tests, and Cox regression. Results: Forty-two pts met inclusion criteria. Median age was 57 (range 19–77), 69% were male, and 79% were white. Most (69%) had ECOG 0–1. No patients had HIV, hepatitis B or C, or a history of solid organ transplant. LDH was elevated at diagnosis in 38%, and 24% had B-symptoms. Mean absolute lymphocyte count at diagnosis was 1.82/µL. The most common histologic subtypes were PTCL-NOS (76%), followed by ALK-negative ALCL (12%) and γδ T-cell lymphoma (5%). All patients had parenchymal brain lesions with 57% having multifocal disease. Additionally, CSF involvement was seen in 21%, vitreoretinal involvement in 3%, and deep brain involvement in 34%. Next-generation sequencing was performed in seven pts (17%), with disease-associated variants identified in three cases. Among these, two pts had mutations in TP53, and one had a mutation in DNMT3A. Cytogenetics were obtained in 7 pts with only one exhibiting a complex karyotype. Only one pt was EBV positive by EBER-ISH. Overall, 79% received HD-MTX-based therapy. First-line treatments were mainly HD-MTX alone (38%), HD-MTX + temozolomide (17%), or vincristine + procarbazine (12%). No patients were treated on clinical trials. Median treatment duration was 78 days and median number of treatment cycles was 4 (range 1–9 cycles). One patient received radiation alone; 5% received radiation with systemic therapy. A steroid pre-phase was used in 60%, with 44% exhibiting a clinical response. Overall response rate to first-line treatment was 63% (13 CR, 12 PR). Imaging alone was used in determining response in all patients. Repeated biopsy was not performed. Twelve patients (29%) underwent consolidative autologous transplant, most commonly with thiotepa/carmustine (TT/BCNU, 69%) or BEAM conditioning (25%). Median duration of follow-up was 10.4 months. Sixty-two percent of pts progressed during the study period, with 7% experiencing extra-CNS relapse. Median PFS was 8.2 months. Improved PFS was associated with &gt;3 cycles of therapy (p=0.03) and transplant with TT/BCNU (p=0.0004). At last follow-up, 43% were in remission and 52% were deceased, mostly due to disease progression (77%). Median OS was 17.6 months. One- and two-year OS rates were 58% and 42%, respectively. OS was associated with Nottingham/Barcelona score &lt;2 (p=0.02), &gt;3 treatment cycles (p=0.0008), response to first-line therapy (p=0.0007), and TT/BCNU-based transplant (p=0.0001). IELSG, Taipei, and MSKCC risk scores were not significantly associated with survival, though IELSG approached significance (p=0.09). Discussion: This study is among the largest cohorts of PCNSTL pts compiled to date. PCNSTL remains rare and heterogenous. Treatment across centers largely mirrors management of B-cell PCNSL with high utilization of HD-MTX regimens and TT/BCNU conditioning autologous transplant. Survival outcomes within our cohort are consistent with those previously reported within the literature. Receipt of &gt;3 cycles of therapy, TT/BCNU conditioning and Nottingham/Barcelona scores were associated with longer survival within our cohort. Limitations of our study include its retrospective design and heterogeneity within pt disease characteristics, treatments utilized and disease assessment intervals. Further exploration into pathophysiology and optimal management of this unique entity is needed.

Abstract Introduction: T-PLL is a rare, aggressive leukemia with poor prognosis and limited therapies. Previous studies on T-PLL patients receiving an allogeneic stem cell transplant (alloSCT) are limited by small numbers with limited data on disease and transplant characteristics. Further, recent data from our large national cohort of patients demonstrated significant survival difference between TCL1A+ and TCL1A- T-PLL, and CD8+ T-PLL vs CD8- T-PLL. In this large multi-center series, utilizing comprehensive disease subtype and alloSCT clinical data, we evaluated prognostic and survival therapeutic outcomes in T-PLL patients that had an alloSCT with a particular focus on T-PLL disease subtypes. Methods: We retrospectively evaluated 572 diagnosed with T-PLL at 21 academic cancer centers throughout the USA between 2000-2023, of which we performed a further evaluation on the169 that proceeded with alloSCT. Overall survival (OS) and progression-free survival (PFS) were assessed using Kaplan-Meier methods and Cox proportional hazard models. Results: Among n=169 alloSCT recipients with T-PLL, the median follow-up time was 20.9 months post-alloSCT (range: 0.2-182.9), the median age at transplant was 59 years (range: 35-77) and 52% were male. In evaluated patients (n=109), TCL1A was positive by cytogenetics or FISH in 69%. As our recent analysis demonstrated significant differences in survival among specific subtypes of T-PLL, we evaluated outcomes in patients with CD4+CD8- T-PLL (n=90, 53%), CD4-CD8+ (n=17, 10%) T-PLL, and CD4+CD8+ T-PLL (n=52, 31%). 53% (87/164) had known nodal involvement at diagnosis identified by PET or CT scan and 45% (43/96) of known patients had minimal residual disease (MRD) at the time of transplant [defined as &lt;5% T-PLL in marrow by flow, or +cytogenetics (e.g. TCL1A)] prior to alloSCT. At the time of alloSCT, 136 (80%) patients were in CR and 23 (14%) patients were in PR. Forty-nine (30%) had a myeloablative (MAC)conditioning regimen and 114 (70%) had a reduced intensity chemotherapy (RIC) conditioning regimen. Eighty (49%) patients had TBI as part of their regimen. The most common regimens were fludarabine (flu)/melphalan based regimens (n=44; 26.0%), flu/cyclophosphamide (cy) based regimens (n=33; 19.5%), flu/busulfan based regimens (n=22; 13.0%), flu/total body irradiation (TBI) (n=8; 4.7%), and cy/TBI (n=4; 2.4%). Across the whole cohort, the median OS and PFS post-alloSCT was 32.6 months (95% CI: 21.0-41.9) and 20.8 months (95% CI: 14.4-30.5) months while the 1-year cumulative incidences (CI) of NRM and relapse were 17% and 20%, respectively. The incidences of grade II-IV acute GVHD and cGVHD were 19% and 23%. There was no difference between patients with myeloablative conditioning (MAC) (n=49, 29%) when compared to patients that received reduced intensity conditioning (RIC) (n=114, 67%) in OS (33.1 vs 29.2; p=0.68) and PFS (20.2 vs 20.8; p=0.97). Patients that were MRD+ (n=31) had worse OS (22.2 vs 48.6; p=0.1) and PFS (14.1 vs 32.5; p=0.04) and higher rates of relapse (1-year relapse 20% vs 8%; p=0.08) than patients that were MRD- (n=50). PFS was improved in those who received alloSCT though only trended towards significance due to low numbers (HR 0.76, p=0.09). In subtype analysis, TCL1A+ T-PLL had significantly worse outcomes compared to TCL1A negative T-PLL. TCL1A+ disease had significantly worse OS (21.6 vs 63.1; p=0.01) and PFS (12.4 vs 50.7; p=0.01) compared to TCL1A-. Additionally, in TCL1A+ disease CI of NRM (24% vs 3%; p=0.02) and relapse (25% vs 12%; p=0.86) was higher vs TCL1A- PLL. CD4+CD8-, CD4-CD8+, and CD4+CD8+ disease had no difference in survival via either OS (28.0 vs 34.4 vs 21.0; p=0.17) or PFS (29.4 vs 23.5 vs 13.6; p=0.09) as well as no difference 1-year CI of NRM ( 11.6 vs 23.5 vs 26.2; p=0.35) and relapse (18.5 vs 23.5 vs 20.0; p=0.67).Conclusions: AlloSCT significantly improved outcomes for patients with T-PLL compared to those who did not proceed to alloSCT and remains he only curative therapy for those with T-PLL. OS, PFS, and CI relapse were significantly worse for patients with TCL1A+ subtype of T-PLL, or those with MRD positivity or PR prior to alloSCT. Novel strategies to decrease relapse such as post-alloSCT maintenance therapy to improve outcomes are urgently needed in these patients.

Abstract Background: TP53-mutated (TP53mut) myeloid neoplasms (MN) are a biologically and clinically distinct subgroup of blood cancers associated with extremely poor outcomes and limited response to conventional therapies. In some patients, MN are preceded by clonal cytopenia of undetermined significance (CCUS). Prior cytotoxic exposure (treatment related, TR) is an independent predictor for survival in CCUS (Li et al, Blood Adv. 2024). As TP53mut CCUS and MN are enriched in TR cases, the interaction between cytotoxic exposure and TP53mut status on the risk of progression and survival remains unclear. Methods: Adult patients with CCUS who were evaluated at the Mayo Clinic or South Australian myelodysplastic syndrome (MDS) Registry (Adelaide, Australia) were included. CCUS and MDS were defined according to the 5th edition of the WHO classification for MN (Khoury et al, 2022), except for the exclusion of cases harboring MDS-defining cytogenetics. Next-generation sequencing was performed using a targeted panel covering genes commonly mutated in MN. In cases with &gt;1 TP53mut, VAFs were summed. Survival outcomes were assessed by Kaplan-Meier with log-rank testing. Univariate and multivariate analyses were estimated using Cox proportional hazards regression. Results: Of 320 CCUS cases, 50 (15.6%) harbored TP53mut (TP53mut CCUS), whereas 270 (84.4%) were wild-type (TP53wt CCUS). Median age at diagnosis was 71 years (range 16-99). TP53mut CCUS had a greater proportion of females (60% vs 33.7%, p&lt;0.001) and TR (66% vs 23%, p&lt;0.001) compared to TP53wt. Hematologic parameters including hemoglobin, red cell distribution width, mean corpuscular volume, white blood count, absolute neutrophil count, platelets, and bone marrow blasts were comparable between the two groups. Almost all TP53mut (n=48, 96%) were located in the DNA-binding domain and the median variant allele frequency (VAF) was 9% (range 2-46%). Five (10%) cases harbored 2 TP53mut. The distribution of TP53mut VAF among patients was as follows: ≤2.5% (n=2), 2.5-5% (n=10), 5-10% (n=19), 10-20% (n=11), and ≥20% (n=7). The proportion of cases with cytogenetic abnormalities was smaller in TP53mut compared to TP53wt CCUS(12% vs 25.9%, p=0.035). Both cohorts had a comparable median number of mutations: 2 (range 0-7) in TP53mut and 2 (range 0-5) in TP53wt. The most common co-mutations in TP53mut CCUS were TET2 (n=8, 17.8%), PPMD1 (n=7, 15.6%), DNMT3A (n=6, 13.3%), ASXL1 (n=6, 13.3%), and SRSF2 (n=4, 8.9%). At last follow up, the rate of progression was comparable between TP53mut and TP53wt CCUS (12% vs 22%, p=0.13). Median time to MN progression was not reached in TP53mut and 6.25 months in TP53wt CCUS (p=0.5197). A significantly higher proportion of TP53mut cases acquired complex cytogenetics compared to TP53wt cases (33% vs 2%, p=0.024) at MN progression. Of 20 deaths observed in the TP53mut cohort, non-myeloid hematologic malignancies (n=6, 30%), infections (n=5, 25%), and TP53mut MN (n=4, 20%) were the 3 most common causes. With a median follow-up of 4 years (IQR 1.2-4.8), median OS was longer in de novo (dn) cases (8.7 years for dn TP53wt; not reached for dn TP53mut) and shorter in TR cases (3.3 years for TR TP53wt; 4.8 years for TR TP53mut). Notably, TP53mut showed no independent prognostic impact in the entire cohort, or when stratified by TR vs dn CCUS. On multivariate analysis that included TP53mut status, factors independently associated with inferior OS included prior therapy (HR 2.21, 95% CI 1.41-3.45, p&lt;0.001), anemia (HR 4.1, 95% CI 1.88-8.99, p&lt;0.001), and thrombocytopenia (HR 2.38, 95% CI 1.43-3.95, p&lt;0.001). Similarly, TR CCUS (HR 1.6, 95% CI 1.06-2.4, p=0.03) and anemia (HR 2.15, 95% CI 1.25-3.7, p=0.006) were independently associated with inferior progression free survival. Conclusion: TP53 mut in CCUS did not independently predict inferior survival or increase leukemic transformation. While TP53mut CCUS were less likely to harbor cytogenetic abnormalities at diagnosis, significantly more cases harbored genomic instability at leukemic transformation. The poor outcomes attributed to TP53mut CCUS were driven by prior cytotoxic exposure, cytopenia – particularly anemia, and non-leukemic causes of death. These findings suggest risk stratification in CCUS should prioritize clinical context over TP53mut status alone.

Abstract Background In patients with myelofibrosis (MF) undergoing allogeneic hematopoietic cell transplantation (allo-HCT), graft-versus-host disease (GVHD) prophylaxis has traditionally included a calcineurin inhibitor (CNI) plus methotrexate (MTX). We conducted a retrospective study comparing the safety and efficacy of post-transplant cyclophosphamide (PTCy)-based GVHD prophylaxis to CNI-based regimens. Methods This study was approved by the Mayo Clinic IRB. Patients with myelofibrosis who underwent allo-HCT after 2016 at Mayo Clinic in Arizona and Florida were included. Categorical variables were compared using Chi-square or Fisher's exact tests. Overall survival (OS) was defined from transplant to death, and progression-free survival (PFS) from transplant to relapse or death. OS and PFS were estimated using Kaplan-Meier methods; univariate differences were assessed with log-rank tests. The cumulative incidence of acute and chronic GVHD and time to neutrophil and platelet engraftment were analyzed using competing risk models, with death as a competing event; differences were tested using Gray's test. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs). Results A total of 110 patients were included. 53 patients received PTCy-based prophylaxis (43 PTCy/Tac/MMF, 1 PTCy/CSA/MMF, 9 PTCy/Siro/MMF), while 57 received non-PTCy regimens (54 Tac/MTX +/- 39 T-cell depletion, 2 CSA/MMF, 1 Tac/MMF). Median age at transplant was 63 (range: PTCy 40-76; others 38-74) years in both groups; 59 were male (58.5% PTCy vs 49.1% others). Median Karnofsky Performance Status (KPS) and HCT–Comorbidity Index (HCT-CI) in patients receiving PTCy vs non-PTCy were 90 vs 80 and 1 vs 3, respectively. Conditioning intensity was similar: 22.6% myeloablative vs 21.7%, and 77.4% reduced-intensity vs 76.7% in PTCy and non-PTCy, respectively (p=1.000). Stem cell source was peripheral blood in all patients except one in the non-PTCy group who received bone marrow. 58 patients had primary MF (54.7% PTCy vs 50.9% others), and 52 had secondary MF (45.3% PTCy vs 49.1% others), including essential thrombocythemia (28.3% PTCy vs 31.6% others), polycythemia vera (17.0% vs 15.8%), and MPN-NOS (0% vs 1.8%). Median follow-up was 26.2 months (95% CI: 20.7-52.7) in the PTCy and 60.6 months (95% CI: 53.1-70.6) in the non-PTCy cohort. CD3 and CD33 donor chimerism ≥95% at day +100 was 66.7% and 86.7% in PTCy vs 63.6% and 92.7% in others, respectively (p=0.50); day +100 driver molecular mutations were present in 32.1% of PTCy and 32.0% of others (p&gt;0.99). Rates of acute GVHD grades ≥2 and ≥3 were not statistically significant, in the PTCy group (37.7% vs 49.1% p=0.229 and 17.0% vs 22.8% p=0.445, respectively). Chronic GVHD (any grade) occurred in 42.3% of PTCy vs 38.2% of others (p=0.664), while moderate-to-severe cGVHD was lower with PTCy (21.2% vs 27.3% p=0.461). Platelet engraftment was significantly delayed in the PTCy group (median 33 vs 21 days, p=0.030). Median time to neutrophil engraftment was also delayed in the PTCy group (20 vs 17 days, adjusted p=0.025). Age-adjusted HR for time to platelet engraftment was 0.60 (95% CI: 0.41–0.90; p=0.014), and for neutrophil engraftment 0.65 (95% CI: 0.44–0.95; p=0.025), indicating significantly delayed hematopoietic recovery with PTCy. Graft failure occurred in 9.4% vs 5.3% (p = 0.48); primary 7.5% vs 3.5%, secondary 1.9% vs 1.8% in PTCy vs non-PTCy groups, respectively. Relapse or progression occurred in 11.3% of PTCy vs 17.5% of others (p=0.355); four patients in the non-PTCy group progressed to AML post-transplant, versus none in the PTCy group (p=0.119). 1-year TRM was 22.6% in the PTCy group and 14.0% in the non-PTCy group, p = 0.324. Median OS was 72.8 months in the PTCy group (95% CI: 49.9 months, upper limit not estimable [NE]) and 93.4 months in the non-PTCy group (95% CI: 48.5 months, upper limit NE), although the difference was not statistically significant (p=0.739). After adjusting for age and HCT-CI, there were no significant differences in PFS (adjusted HR 1.37; 95% CI: 0.73–2.56; p=0.331) or OS (adjusted HR 1.27; 95% CI: 0.64–2.51; p=0.498). Conclusions In myelofibrosis patients undergoing allo-HCT, PTCy-based GVHD prophylaxis showed similar rates of grade ≥2 acute and moderate-severe chronic GVHD compared to non-PTCy regimens. Engraftment was significantly delayed, while OS and PFS were comparable. PTCy appears to be a safe and viable alternative to CNI-based prophylaxis.

Abstract Background: Systemic mastocytosis (SM) comprises a spectrum of subtypes characterized by neoplastic mast cell (MC) infiltration of tissues and release of MC mediators. Non-advanced SM (NonAdvSM), including indolent SM (ISM), smoldering SM (SSM), and bone marrow mastocytosis (BMM) subtypes, is the most prevalent form of SM. NonAdvSM can be associated with debilitating symptomology which can significantly impair quality of life. The gain-of-function somatic KIT c.2447 C&gt;T (p.D816V) mutation is found in up to 95% of patients with SM. Bezuclastinib (CGT9486) is an oral, potent, and selective type 1 tyrosine kinase inhibitor with activity against KIT D816V. Results from Summit (NCT05186753) Part 1 informed the recommended phase 2 dose (100 mg QD bezuclastinib) for Part 2. We report topline results from the 24-week assessment of Summit Part 2. Methods: Summit is a multi-center, randomized, double-blind, placebo (PBO)-controlled Phase 2 trial of bezuclastinib in patients with NonAdvSM who had inadequate symptom control despite best supportive care (BSC) medications. The primary endpoint was 24-week mean change from baseline in Mastocytosis Symptom Severity Daily Diary (MS2D2) total symptom score (TSS) (range 0–110), which is a fit-for-purpose patient-reported outcome measure of NonAdvSM symptom severity. Key secondary endpoints included the proportion of patients with ≥50% reduction in serum tryptase, KIT p.D816V variant allele frequency (VAF), bone marrow (BM) MC burden, and MS2D2 TSS, ≥30% TSS reduction. Patients were randomized 2:1 to receive 100mg QD bezuclastinib + BSC or PBO + BSC. Results: As of May 22, 2025, 179 patients were enrolled in Part 2: 119 were randomized to receive bezuclastinib and 60 to placebo. Patients enrolled were representative of the NonAdvSM population with moderate to severe symptoms. Median age (range) was 51 (23-78) years; 65.9% female; mean (SD) baseline MS2D2 TSS 55.6 (19.8); 82% of patients had ISM, 11% had BMM, and 7% had smoldering SSM. At baseline, median (range) KIT p.D816V VAF in whole blood, BM MC burden, and serum tryptase was 0.25% (0-34%), 10% (1-75%), and 40 (6-692) ng/mL, respectively. Bezuclastinib demonstrated statistically significant superiority to placebo on all primary and key secondary endpoints. At Week 24, bezuclastinib led to significantly greater symptom improvement vs placebo (LS mean [95% CI] MS2D2 TSS change: –24.3 [–27.6 to –21.1] vs –15.4 [–19.6 to –11.2]; placebo-adjusted difference: –8.9 points; P=0.0002). A ≥50% reduction in serum tryptase was achieved in 87.4% of bezuclastinib-treated patients vs 0% on placebo (P&lt;0.0001). Significantly more patients receiving bezuclastinib achieved ≥50% reductions in KIT D816V VAF, serum tryptase, BM MCs (P&lt;0.0001), MS2D2 TSS (P=0.01), and ≥30% reduction in MS2D2 TSS (P=0.0004). Most treatment-emergent adverse events (TEAEs) were low grade (gr; 70% Gr 1) and reversible. The most common TEAEs (≥10%) in any treatment group and occurring in greater frequency in the bezuclastinib arm were hair color changes (69.5% vs 5.0%), altered taste (23.7% vs 0%), nausea (22.0% vs 13.3%), increased ALT/AST (22.0% vs 6.6%), headache (17.8% vs 11.7%), alopecia (11.9% vs 3.3%), and increased ALP (10.2% vs 3.3%). TEAEs (≥10%) that occurred more often in the placebo group were diarrhea (13% vs 18%), dizziness (10% vs 12%), fatigue (7% vs 12%), and arthralgia (6% vs 15%). ALT/AST elevations ≥Gr 3 were experienced by 5.9% of patients. The only hepatic adverse events (AEs) reported were transient lab abnormalities; none required hospitalization. Treatment-related AEs requiring dose reductions occurred in 11% of patients receiving bezuclastinib. All discontinuations (5.9%) due to treatment-related AEs were due to transaminase elevations; all fully resolved. Conclusions: At 24-weeks, bezuclastinib 100 mg QD demonstrated statistically and clinically significant improvements in symptom burden and biomarkers of disease vs placebo in patients with NonAdvSM. The treatment was generally well-tolerated and effective across a population that is representative of the real-world NonAdvSM population, including SSM. These results support the use of bezuclastinib to reduce SM burden and symptoms in pts with NonAdvSM, and a potentially disease-modifying impact.