Krakow, Elizabeth F.

ABSTRACT Hypomethylating agents (HMA) and allogeneic hematopoietic stem cell transplantation (alloHSCT) have both demonstrated remissions in VEXAS; however, comparative data is lacking. We conducted a multicenter, retrospective analysis of 66 patients diagnosed with VEXAS syndrome treated with HMA ( n = 35) or alloHSCT ( n = 31). Baseline characteristics such as genetics, co‐morbidities, and performance status were balanced between the groups, except older age in the HMA group. Median follow‐up from therapy initiation was 18 months (95% CI: 11–26), and 14 (21%) deaths were reported (alloHSCT n = 3; HMA n = 11). Among all evaluable patients within the alloHSCT cohort, all patients achieved molecular remission, and a substantial proportion of patients discontinued glucocorticoids (58%). In contrast, HMA therapy was associated with lower but meaningful rates of molecular remission (22%) and glucocorticoid discontinuation (6%). In a real‐world setting, HMA therapy was associated with a high discontinuation rate related to toxicity or lack of response. On multivariable analysis adjusted for age and Charlson Comorbidity Index, alloHSCT was associated with improved overall survival (HR = 0.20, 95% CI: 0.05–0.81; p = 0.024). This association remained consistent across multiple ancillary sensitivity analyses, including restriction to transplant‐eligible patients, patients aged ≤ 75 years, 1:1 matching, and propensity score‐based weighted analyses. Although limited by retrospective design, these findings suggest that alloHSCT remains an attractive and potentially curative strategy in selected patients with VEXAS. Prospective validation of these findings is warranted.

Abstract Background: VEXAS (Vacuoles, E1 enzyme, X-linked, Autoinflammatory, Somatic) syndrome is a hemato-inflammatory syndrome due to somatic mutations in UBA1 gene. Recently, DNA methyltransferase inhibitors (specifically, 5-azacitidine) and allogeneic hematopoietic stem cell transplantation (alloHSCT) have shown success in eradication of UBA1 clones and clinical remission in some patients. This study aims to provide a comparative efficacy analysis between DNA methyltransferase inhibitors (hypomethylating agents/HMA) versus alloHSCT in VEXAS syndrome patients. Methods: This is a multi-center, retrospective cohort study. UBA1 mutations were detected either through next generation sequencing [NGS, limit of detection (LOD) 2% variant allele fraction (VAF)] or quantitative droplet digital polymerase chain reaction testing (ddPCR, LOD 0.5% VAF). Outcomes of interest included overall survival (OS), glucocorticoid (GC) discontinuation/reduction in dose (prednisone < 10 mg/day), and complete molecular remission (CMR, defined as an undetectable UBA1 mutation). OS was calculated from the time of diagnosis to death or last follow up. Cumulative incidence of reduction in GC dose was calculated using competing risk analysis after accounting for death. Results: Between years 2020-2024, a total of thirty-nine male patients (median age 67, range 45-82 years) with VEXAS syndrome, necessity for therapy (GC-refractory inflammation and/or progressive marrow failure/myeloid neoplasm) and confirmed UBA1 pathogenic mutation were included. Of these, 18 (46%) received HMA therapy (5-azacitidine 72% and Decitabine 28%) with a median of 4 (range 1-36) cycles. and 21 (54%) underwent alloHSCT (MSD=4, MUD=12, MMUD=2, and haploidentical=3), all received reduced intensity conditioning (Flu/Mel =11, Flu/Bu=5, Flu/Cy/TBI=2, and TBF=3) and 91% received post-transplant cyclophosphamide-based graft-versus-host disease (GVHD) prophylaxis (only 2 patients in alloHSCT group received prior HMA without benefit). Baseline characteristics were well-balanced between HMA and alloHSCT groups; age at treatment (median 70 vs 65 years, p=0.2), and UBA1 M41V subtype (25% vs 40%, p=0.3), cytogenetic and non-UBA1 mutation abnormalities (p=0.4), prior lines of therapy (median 4 in both, p=0.5), time from diagnosis to therapy (median 7 vs 13 months, p=0.15), indication for therapy (p=0.12), Charlson CI scores (median 4 in both, p=0.4) and HCI-CI scores (median 4 in both, p=0.7). At a median follow-up of 45 (range 7-57) months, 11 (28%) deaths (alloHSCT=3 and HMA=8) were documented. Causes of death included infections (n=6), cardiac disease (n=2), poor graft function (n=2) and pulmonary GVHD (n=1). Compared to HMA therapy, alloHSCT group demonstrated higher rates of GC discontinuation (52% vs 6%, p<0.01) and CMR (evaluable= 22, 100% vs 50%, p<0.01). In the HMA group, 50% (n=9) discontinued therapy after a median of 4 months due to infectious complications or lack of benefit. In the alloHSCT group, 3 (14%) patients developed grade 2 acute GVHD (1-skin, 2-gut, no grade 3-4 acute GVHD) and 4 (19%) experienced moderate to severe chronic GvHD (2-lung, 2-mucocutaneous). In multivariable analysis (MVA) adjusted for age and HCT-CI, alloHSCT was identified as the strongest favorable predictor for OS (HR 0.18 95% CI 0.04-0.8) with similar results when analysis was restricted to transplant-eligible patients < 75 years of age (HR 0.1, 95% CI 0.03-0.6). In a 6-month post-treatment landmark analysis (n=31 evaluable), patients who underwent alloHSCT (n=17) exhibited numerically superior GC discontiuation rate (29% vs 14%, p=0.049) and subsequent OS compared to HMA (2-years OS: 84% vs. 61%, median not reached vs 25 months, 95% CI: 0.06–1.7). In a post-treatment competing risk [GC dose reduction (death)] analysis alloHSCT was associated with superior 2-, and 3-year rates of 57% (10%), and 76% (10%), compared to HMA 22% (24%), and 31% (42%) [p<0.01 (0.04)]. AlloHSCT was also associated with higher rate of CMR (evaluable= 21, alloHSCT N=16 and HMA N=5, 100% vs 60%, p=0.01). At the last follow up, none of the patients who achieved CMR had re-emergence of the UBA1 clone (despite early mixed chimerism). Conclusions: This study represents the largest comparative analysis of alloHSCT versus HMA therapy in VEXAS syndrome, and confirms superiority of alloHSCT in achieving molecular remission, GC discontinuation/dose reduction, and overall survival. Prospective clinical trial confirmation is warranted.

Abstract Abstract 1159 Background. Heparin induced thrombocytopenia (HIT) is an immune disorder where platelets are activated by antibodies to a complex of platelet factor 4 antigen and heparin (PF4/H), leading to thrombocytopenia (HIT) and, potentially, thrombosis (HITT). Documentation of anti-PF4/H antibodies in addition to the appropriate clinical findings is essential for making a diagnosis of HIT. In the post-cardiac bypass surgery setting, however, the frequency of elevated anti-PF4/H antibodies is high, whereas the frequency of clinical HIT or HITT is relatively uncommon. Several studies have shown that the presence of anti-PF4/H antibodies may be associated with an increased frequency of adverse outcomes, even in the absence of clinical HIT. The primary objective of this study was to determine the relationship between a positive PF4/H antibody in the postoperative setting with adverse thromboembolic events occurring up to 3 months after cardiac surgery. Methods. Patients undergoing cardiac surgery who were not going to be treated with chronic anticoagulation postoperatively were eligible for this multi-center prospective cohort study. Data were collected daily during hospitalization, and then at 30 and 90 days after surgery using a structured interview format with a standardized questionnaire that included all thrombotic as well as hemorrhagic events, platelet counts, and utilization of antithrombotics in the postoperative setting. The primary outcome variable was a composite endpoint comprising arterial and venous thrombotic events and other miscellaneous events compatible with HIT, as well as death attributable to an event compatible with HIT. Citrated plasma was collected at baseline, pre-discharge (∼4–5 days after surgery), and the 30 day follow-up visit, processed, and stored at −80°C for testing. Laboratory analyses included an anti-PF4/H antibody ELISA (GTI, Waukesha, WI) on all samples, a high-heparin confirmatory test on samples with an OD reading >0.40, and a serotonin release assay (SRA) on all postoperative samples with an OD reading >0.40. A sample size of 800 patients was estimated in order to detect a 3% difference in thromboembolic events assuming a 2 to 10-fold increase risk attributable to seropositivity. Chi-squared testing was used to test the relationship between the primary outcome and postoperative anti-PF4/H levels. Results. Informed consent was obtained from 1030 eligible patients between August 2006 and May 2009, and laboratory and follow-up data were analyzable for 1016 patients. Thirty-day antibody data were available for 888 patients, and fully complete laboratory and 90-day follow-up data were available for 815 patients. The average age was 62 ± 12 years, and 73% of participants were male. A total of 769 patients underwent coronary artery bypass grafting and 237 underwent valve repair or replacement. During the entire study period, there were 17 (1.7%) deaths, 46 thromboembolic events in 44 patients (4.3%), and 25 hemorrhagic events in 24 patients (2.4%). Using an OD cutoff of 0.40 for the ELISA, 339 patients (33.4%) were positive for anti-PF4/H antibodies at the time of discharge, and 630 patients (62%) were positive by day 30. There was no correlation between seropositivity for anti-PF4/H antibodies at the day of discharge or at day 30 and the primary outcome (p=0.47 and 0.73, respectively). Incorporating the high-heparin confirmatory step did not improve the relationship between positive antibody results and the primary outcome. Using a higher cut-off value for the anti-PF4/H antibody ELISA of 1.0 decreased the number of patients with positive results (96 patients at the time of discharge [9.4%] and 221 patients at the 30-day follow-up visit [21.8%]), but this did not improve the relationship between antibody positivity at the day of discharge or day 30 and the primary clinical endpoint, since most patients with the primary endpoint had an ELISA OD below 1.0 (75th percentile of 0.90; 90th percentile of 1.22). Similarly, using the SRA did not identify a relationship between assay results and outcome. Conclusions. The presence of anti-PF4/H antibodies in the postoperative setting following cardiac bypass surgery is not associated with an increased risk for thromboembolic complications. Positive anti-PF4/H results in this clinical setting should be interpreted with caution and only in the context of clinical suspicion for HIT. Disclosures: Ortel: Instrumentation Laboratory: Consultancy; Eisai: Research Funding; GSK: Research Funding. Welsby:CSL Behring: Speaker; CSL Behring: Membership on an entity's Board of Directors or advisory committees; NovoNordisk: Principal Investigator. Heit:Daiichi Sankyo: Honoraria; Ortho-McNeil Janssen: Honoraria; Covidien: Honoraria.