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Abstract Introduction: DDX41 (DEAD-box helicase 41) mutations (mt) represent the most prevalent germline predisposition syndrome (GPS) in adult patients (pts) with myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). This molecular subtype is typically associated with late-onset disease, runs an indolent clinical course, with a relative absence of high-risk co-mutations. While several retrospective studies have reported favorable responses to venetoclax (VEN)-based therapies, anecdotal observations suggest variable outcomes. We aimed to evaluate the clinical characteristics and treatment outcomes of patients with DDX41-mt MDS/AML treated at the Mayo Clinic. Methods: We conducted a retrospective study of pts diagnosed with DDX41-mt germline predisposition syndrome with concurrent myeloid neoplasms at our institution. Germline testing was conducted under an IRB approved protocol (Mayo Clinic IRB# 16-004173; clinical-trials gov. Identifier: NCT02958462). Of 198 pts with DDX41-mt myeloid neoplasms, 77 had high-risk disease—43 with MDS with increased blasts (MDS-IB1, n = 11; IB2, n = 32) and 34 with AML (WHO 2022). We assessed how clinical, and disease features influenced outcomes in this subgroup. Among these pts, 69 (90%) pts had likely pathogenic/pathogenic variant (DDX41path) variants and 8 (10%) pts had variant of undetermined significance (DDX41VUS) according to variant classification criteria from the American College of Medical Genetics/ the Association of Medical Genetics/ the Association for Molecular Pathology (ACMG/AMP) guidelines. Results: The median age was 68 years (yrs) (range [R],34-92), 70% were male and the median bone marrow blast % was 15 (R,5-60). The most common DDX41 germlinevariants (> 5% cases) included p.D140fs (26%), p.M1I (22%), and p.P258L (6.5%). 74% had DDX41 truncating variants. Thirty-one (40%) acquired a somatic DDX41-mt (R525H [81%]) and 43 (56%) had other somatic mutations. Among these, the most frequent were ASXL1 (n= 9, 21%), TP53 (n= 8, 10%), splicing factor (n= 7, 9%), and DNMT3A (n= 5, 6%). Twenty-six, (34%), 26 (34%), 15 (19%) and 9 (12%) pts were treated with hypomethylating agents (HMA), HMA+VEN, intensive chemotherapy (IC) and active surveillance/supportive care, respectively. Overall, the composite complete remission rate (cCR) in high-risk MDS and AML was 56%. The cCR rates (41%, 59% and 68.7%, p= 0.10) and median duration of response (DOR; 43.7, 44.9 and 28.9 months [mo], p= 0.46) were not significantly different with HMA, HMA+VEN, and IC induction. Thirty-one (40%) pts received allogeneic stem cell transplantation (allo-HCT); 4 (36%), 15 (47%) and 12 (35%) in MDS-IB1, MDS-IB2 and AML groups, respectively (p= 0.56). With a median follow up of 34.7 mo (R, 0.7-136.7), the median overall survival (OS) from the time of diagnosis was 56.9 mo (95% CI, 50.7-63.0) and was not significantly (NS) different between MDS-IB1 (not reached, 70% at 3 yrs), MDS-IB2 (56.9 mo, 86% at 3 yrs) and AML (55.7 mo, 60% at 3 yrs) groups, p= 0.16). The median OS was NS different between DDX41path and DDX41VUS (58.6 vs 55.7 mo, p= 0.50), respectively. We conducted a multivariable analysis for OS using variables that showed significance or trend towards significance in univariable analysis. Concurrent splicing factor mutations (HR; 5.29, 95% CI: 1.29-21.6, p= 0.02) remained negatively prognostic, while there was a trend towards better survival outcomes with allo-HCT (HR; 0.48, 95% CI: 0.21-1.07, p= 0.07). Bone marrow blast ≥ 20% (HR; 1.87, p= 0.12) and TP53-mt (HR; 2.14, p= 0.12) did not retain significance. Conclusion: In our cohort of patients with germline DDX41-mt high-risk MDS and AML, VEN-based regimens were not superior to HMA alone or IC, in terms of response rates and outcomes. On multivariable analysis, the presence of concurrent splicing factor mutations independently and negatively impacted survival with a trend towards better outcomes with allo-HCT. These findings highlight the heterogeneity within DDX41-mt myeloid neoplasms and underscore the need for future studies in larger cohorts to better define predictors of response and survival.

Abstract Introduction Acute chest syndrome (ACS) is a life-threatening complication of sickle cell disease that often requires hospitalization and urgent intervention. Hospitalized patients may present with multiple acute conditions necessitating glucocorticoid therapy. Although glucocorticoids are well known for their anti-inflammatory effects, their use in ACS remains controversial due to concerns about worsening of underlying infection, progression to sepsis, and subsequent respiratory failure. This study aims to evaluate the impact of concomitant glucocorticoid use on clinical outcomes in patients with ACS. Methods A retrospective cohort study was conducted using the US Collaborative Network TriNetX, covering January 2000 to December 2023, encompassing data from 105 global healthcare organizations. Adult patients aged 18 and above with acute chest syndrome were identified and then stratified into two groups based on treatment with glucocorticoids during the index hospitalization or not. The two groups were then propensity-matched based on age, sex, race, and comorbidities. We followed these patients for 5 years to assess outcomes, including overall mortality, simple transfusions, exchange transfusions, need for mechanical ventilation, incidence of pneumonia, influenza, sepsis without shock, sepsis with shock, and need for hemodialysis. Results We identified 4197 patients in the acute chest syndrome with glucocorticoids cohort and 8211 patients in the acute chest syndrome without glucocorticoids cohort. After propensity matching, each cohort consisted of 4111 patients with similar baseline characteristics. Our analysis found that over 5 years, patients with acute chest syndrome who received glucocorticoids during the index hospitalization had a significantly higher risk of overall mortality (Hazard Ratio (HR): 1.361, 95% CI: 1.158 to 1.599, p-value <0.001), simple transfusions (HR: 2.191, 95% CI: 2.015 to 2.381, p-value =0.009), exchange transfusions (Risk difference: 0.008, 95% CI: 0.003 to 0.013, p-value =0.001), need for mechanical ventilation (Risk difference: 0.024, 95% CI: 0.016 to 0.032, p-value <0.001), pneumonia (HR: 1.190, 95% CI: 1.111 to 1.276, p-value =0.004), influenza (Risk difference: 0.044, 95% CI: 0.029 to 0.059, p-value <0.001), sepsis without shock (Risk difference: 0.016, 95% CI: 0.007 to 0.024, p-value <0.001), and sepsis with shock (Risk difference: 0.026, 95% CI: 0.018 to 0.034, p-value <0.001). There was no statistically significant difference in the need for hemodialysis between the two subgroups. Conclusion Our study found that patients with acute chest syndrome who were exposed to glucocorticoids during the index hospitalization had a significantly increased risk of overall mortality, simple transfusions, exchange transfusions, need for mechanical ventilation, incidence of pneumonia, influenza, sepsis without shock, and sepsis with shock. Further longitudinal cohort studies are imperative to better understand these associations and guide evidence-based clinical practice in this population.

Abstract Background: Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma (NHL), accounting for approximately 30% of all NHL cases. DLBCL diagnosis relies on histologic examination, immunophenotyping, molecular and fluorescence in situ hybridization (FISH) analysis to differentiate it from similar NHL subtypes with overlapping morphological features, including more high-grade lymphomas like double-hit lymphoma. Because FISH is performed in a panel of single- or dual-target test format and analyzed through microscopy and manual image analysis, assessment of multiple target biomarkers can be cumbersome and expensive. As additional biomarkers for diagnosis, subtyping, prognosis, and therapeutic decision-making become available, target panels will become larger, posing additional challenges to clinical laboratories. Patients and Methods In this study, Hi-C sequencing of FFPE samples was performed to identify all genomic rearrangements by a single sequencing analysis for an unselected DLBCL case series of 159 patients, and the results were compared to FISH for the detection of clinically important variants. Results Hi-C sequencing showed superior performance compared to FISH: standard FISH for DLBCL includes testing for MYC, BCL2, and BCL6. Between FISH and Hi-C, these biomarkers were detected 105 times, of which, FISH detected 80/105 (76%) and Hi-C detected 102/105 (97%). The cohort included 4 double-hit lymphomas by FISH but Hi-C sequencing detected five. Besides DLBCL diagnostic biomarkers (MYC, BCL2, BCL6), many additional biomarkers were detected by Hi-C sequencing including variants not tested by FISH because the clinical suspicion was ambiguous and the relevant FISH probes were not used, and those not tested because the biomarkers were not thought to be common and, hence, left out of the FISH panel. In total, Hi-C sequencing detected additional biomarkers in 42 (26%) cases, including (1) variants targeted by FISH (i.e. MYC, BCL2, BCL6) but negative, (2) classification biomarkers for other lymphomas (CCND1, MALT, IRF4), and (3) those not tested because the biomarkers are not common and not included in the FISH panel. These additional biomarkers were supportive of suspected diagnosis of DLBCL versus double-hit lymphoma (24 cases), prompted reconsideration of a different diagnosis that may have led to different treatments (6 cases, e.g. mantle cell lymphoma), or biomarkers such as PDL1, ALK, and ATM which have implications for targeted therapies and/or inclusion in clinical trials (5 cases). Conclusion The Hi-C FFPE sequencing technology has the potential to improve the workflow of pathology labs for detection of a wide range of structural variants informing precision diagnosis and treatment for lymphomas.

Abstract Background: Waldenström Macroglobulinemia (WM) is an indolent B-cell lymphoplasmacytic lymphoma characterized by heterogeneous clinical behavior and variable progression patterns. While MYD88L265Pand CXCR4 mutations are frequently encountered, the broader genomic landscape underpinning disease evolution from smoldering WM (SWM) to active treatment naïve WM (TNWM), post-treatment remission WM (PTWM) and relapsed/refractory WM (RRWM) remains incompletely understood. To address this gap, we studied the mutational profile across the WM disease spectrum. Methods We performed whole exome sequencing (WES) on sorted (CD19 and/or CD138) bone marrow aspirates of patients across the spectrum of WM. Paired germline sequencing was performed using peripheral blood mononuclear cells (PBMCs). Unique molecular identifier-tagged reads were deduplicated using fgbio. WES data were processed through the Sarek pipeline. Any valid mutation from either caller, present on the index or in COSMIC was considered. Copy number variations (CNVs) were inferred via CNVkit and summarized at the gene and arm level (≥50% directional change). Mean tumor and germline coverages were 174X and 74X, respectively. Fisher's exact test was used for enrichment and hypergeometric test for overlap analyses. Results A total of 78 high-quality WM samples [15 SWM, 44 TNWM, 13 RRWM, 6 PTWM in remission (all with paired TNWM samples)] were sequenced. The mutational burden varied across disease states (median SWM=1.48 m/Mb, TNWM= 1.12 m/Mb, RRWM = 1.59 m/Mb; p=0.04). Density plots revealed bimodal VAF distributions, consistent with clonal and subclonal architectures in WM. Overall, 77% harbored a MYD88L265P mutation by WES. Among MYD88^WT^ patients, AS-PCR identified MYD88L265P in 4 (25%) not detected by WES, raising the overall mutation rate to 83%, plus one with a non-L265P variant. Low VAF (<10%) MYD88L265P mutations were seen in 6% of matched PBMCs. MYD88 copy number gain was seen in 2 (17%) MYD88WT TNWM patients. CXCR4 mutations were detected in 38% by WES (18% each frameshift and nonsense). Two (4%) CXCR4WT samples were positive by PCR, giving an overall rate of 40%. CXCR4 mutations were more frequent in RRWM (54%) vs TNWM (41%) and SWM (27%), though not statistically significant. Del(6q) and Del(17p) were noted in 16% (n=12) and 7% (n=5) of patient samples. All del(17p) events were noted in TNWM samples and in one paired post-treatment sample. Overall rate of del(17p) and TP53 mutation was 14% (n=11). RRWM was enriched in ARID1A alterations, a gene implicated in chromatin remodeling and plasma cell identity formation [38% (n=5) in RRWM vs. 11% (n=6) in TNWM and SWM], compared to TNWM and SWM p=0.03]. Alterations in NF-kB signaling gene MAP3K14 were more frequent in RRWM (31%, n=4) compared to the SWM/TNWM cohort [(7%), n=4; p=0.036). We noted an enrichment in the TP53 mutation rate in RRMW [n=3, 23%, OR 7.7] compared to TNWM and SWM cohorts [n=2, 4%), p=0.04]. Mutations in FUBP1 (p=0.03), an upstream regulator of MYC, and CARD11 (p=.043), a B-cell signaling scaffold protein were also more frequent in RRWM. Notably, none of the SWM patients harbored an ARID1A alteration (p=0.057), suggesting acquisition during progression. CNV analysis revealed that MAP3K14 amplifications were frequent in RRWM (n=3, 23%) compared to SWM/TNWM [n=2 (4%), p=0.043]. RRWM samples showed increased CD79B mutations (15%) and significant overlap with the C5/ABC diffuse large B-cell lymphoma (DLBCL) genomic cluster (Chapuy et al., Nat. Med. 2018; p=0.007). This overlap remained significant after excluding MYD88L265P (p=0.019), driven by CARD11, CD79B, and IGLL5, suggesting that a subset of RRWM may acquire an ABC DLBCL-like mutational profile. These findings warrant further investigation using transcriptional profiling. Conclusions This study provides a genomic map of WM evolution from precursor to relapse. Increasing somatic mutations and CNVs support stepwise progression. Enrichment of genes involved in chromatin remodeling and plasma cell identity formation (ARID1A), NF-kB or BCR signaling (CARD11, MAP3K14), and DNA damage repair (TP53) were noted at relapse, all of which have been shown to drive aggressive disease biology. Emergence of an ABC-like genotype in a proportion of RRWM indicates convergent evolution with aggressive lymphomas. Transcriptional studies are warranted to explore this further.

Abstract Background: Renal allograft thrombosis, though commonly attributed to surgical or anatomical causes, is increasingly linked to inherited thrombophilia, including Factor V Leiden, prothrombin gene mutations, and deficiencies in protein C, protein S, or antithrombin III. These conditions raise the risk of early graft thrombosis and may impair graft survival. While therapeutic anticoagulation has been proposed as a preventive strategy, there are no established guidelines to direct its use in transplant recipients with thrombophilia. Methods: We systematically searched PubMed, Embase, and the Cochrane Library from inception to July 2025 to assess the role of therapeutic anticoagulation in kidney transplant recipients with thrombophilia. Two reviewers independently screened 275 titles and abstracts, as well as 35 full-text articles, using Covidence. Eligible studies included observational cohorts and case series (with≥2 patients) that reported anticoagulation outcomes in adult transplant recipients with thrombophilia. Case reports (n=1), reviews, pediatric studies were excluded. No randomized controlled trials were identified. Eleven observational studies met our inclusion criteria. Results: Type of anticoagulation medication, timing of use, and outcome reporting were heterogeneous. Only one retrospective cohort study directly compared anticoagulated and non-anticoagulated patients, reporting no thrombotic events in the anticoagulated group versus two in the control group. Several studies suggested benefits of anticoagulation, particularly in patients with antiphospholipid syndrome or lupus anticoagulant. Bleeding complications were reported in some of the studies, with major bleeding rates ranging from 20% to 30% in some cohorts. One study noted a 30% rate of perinephric hematomas in patients receiving perioperative heparin. Due to significant heterogeneity in study design, anticoagulation protocols, thrombophilia, and outcomes reported, meta-analysis was not feasible. Conclusion: Therapeutic anticoagulation may reduce thrombotic risk in kidney transplant recipients with thrombophilia, but bleeding complications and limited comparative evidence preclude general recommendations. Randomized and controlled studies are needed to better define indications and safety. Until then, anticoagulation decisions should be individualized based on patient risk factors and clinical context.

Abstract Background: Prophylactic-dose or low-dose apixaban and rivaroxaban have been studied in randomized controlled trials for the extended prevention of venous thromboembolism (VTE) after 6 months of treatment with therapeutic anticoagulation. However, the optimal timing of dose adjustment has not been fully explored, and the rationale for a precise transition at the 6-month mark is lacking. Aim: Evaluate the clinical outcomes and demographic differences between transition to low-dose DOAC before or after the previously studied 6-month timeframe. Methods: Consecutive patients with VTE were identified using the Mayo Clinic VTE Registry from March 1st, 2013 to December 31st, 2021. Patients with recurrent VTE or bleeding during the first 3 months were excluded. Patients were followed prospectively for outcomes of VTE recurrence, major bleeding, and clinically relevant non major bleeding (CRNMB), either in person or by survey. After completion of anticoagulation treatment for 3 months, the cohort of patients continuing anticoagulation with eventual transition to low-dose rivaroxaban or apixaban were evaluated. Results: A total of 466 patients were included with 167 (36%) undergoing transition to low dose prior to 6 months and 299 (64%) after 6 months of treatment. The average time to low-dose transition in the total population was 7.8 months (5.9, 3.0-55.8). The early transition group had less PE (82 versus 191, p=0.017) and significantly fewer patients with concurrent DVT and PE (32 versus 101, p=0.004). There was nearly equal representation of cancer in the two groups (34.7% versus 35.8%). Evaluation of clinical outcomes from transition time forward in the groupings before and after six months revealed no significant differences (VTE recurrence p=0.233, MB p=0.114, CRNMB p=0.745). Conclusions: This real-world patient population demonstrates that anticoagulant prescribers transition to low-dose DOACs ahead of the historically studied 6-month time point. The results of this study do not indicate a significant difference in clinical outcomes of VTE recurrence or bleeding complications based on time of transition to low-dose DOACs either before or after 6 months.

Abstract Background Iron deficiency anemia (IDA) is the most common nutritional disorder worldwide and a leading cause of anemia in the United States. Anemia accounts for over 800,000 Emergency department (ED) visits annually in the United States, many of which are for blood transfusions. Despite its burden, IDA remains underdiagnosed and undertreated. This study sought to characterize the incidence of iron deficiency in patients receiving a blood transfusion in the ED at a large academic medical center and to identify areas for improvement in diagnosis management.Methods We conducted a retrospective cohort study of adult patients with severe anemia who received at least one PRBC transfusion in our ED between January 1stand December 31st, 2021. Patients considered at risk for iron deficiency included those with a mean corpuscular volume (MCV) < 80 fL on the day of the ED visit, a ferritin < 40 ng/mL on the day of or with any recorded value prior to the ED visit, or an iron saturation < 20% on the day of or with any recorded value prior to the ED visit. Patients with confirmed iron deficiency included those with ferritin levels < 40 ng/mL or iron saturation < 20% within 90 days prior to the ED visit. This 90-day period included labs checked on the day of the ED visit. We also collected B12 and folate levels to determine the incidence of B12 deficiency and folate deficiency, respectively, within 90 days prior to the ED visit. We defined B12 deficiency and those at risk for B12 deficiency as those with a B12 level < 200 ng/L or with a B12 level 200-399 ng/L, respectively. We defined folate deficiency as having a folate level < 4 mcg/L.Results: Four hundred and sixty-two patients accounted for 558 ED encounters for severe anemia requiring at least one PRBC transfusion. The median age of the cohort was 68 years. Within this cohort, we identified 210 (45%) patients at risk of iron deficiency and 136 (29%) patients with confirmed iron deficiency based on ferritin or iron saturation levels within 90 days of the ED visit. Among these patients with iron deficiency, 44/136 (32.5%) presented with an MCV < 80 fL, 88/136 (65%) presented with an MCV 80-100 fL, and 10/136 (7.5%) presented with an MCV > 100 fL. These findings show that iron deficiency does not always present with microcytosis. Fifteen (3%) of 462 patients had B12 deficiency and another 38/462 (8%) were at risk for B12 deficiency based on levels within 90 days of the ED visit. Two patients had folate deficiency based on levels within 90 days of the ED visit.Conclusions This study highlights the high prevalence of iron deficiency in patients presenting to the ED at a large academic medical center. Furthermore, relying on a low MCV level alone may lead to underdiagnosis of iron deficiency, underscoring the importance for a comprehensive assessment of iron stores when working up a patient with severe anemia. This study also suggests the need for further research to determine whether early identification and treatment of iron deficiency can reduce the frequency of ED visits for blood transfusions, decrease the number of PRBC units transfused, lower hospital admission rates, improve patient outcomes and reduce healthcare cost in our patient population.

Abstract Background: Until 2022, the United Arab Emirates (UAE) lacked in-country allogenic hematopoietic stem cell transplant (allo-HSCT) services, forcing patients abroad for curative treatment while local hematologists managed pre- and post-transplant care. This fragmented model created unique challenges in graft-versus-host disease (GVHD) monitoring and survival tracking. We present the first analysis of outcomes in this underserved population. Aims: To evaluate overall survival (OS) and GVHD rates in adults receiving allo-HSCT abroad with UAE-based follow-up, establishing benchmarks for emerging local transplant programs. Methods: Retrospective multicenter study of adults undergoing allo-HSCT outside the UAE (2009–2023) with follow-up at three tertiary centers (SSMC, SKMC, Tawam). Of 454 screened patients, we excluded pediatric cases (n=245), autologous HSCT (n=76; excluded due to distinct indications/outcomes), and rare allo-HSCT indications (n=33), focusing on the most common diagnoses: acute myeloid leukemia (AML, n=54), B/T-acute lymphoblastic leukemia (B/T-ALL, n=38), and sickle cell disease (SCD, n=8). Kaplan-Meier (KM) analysis estimated 1/3/5-year OS. Observed median survival was calculated for deceased patients. GVHD grading followed NIH consensus criteria. Log-rank tests compared subgroups (donor type). Results: Survival: AML 1/3/5-year OS: 96%/79.3%/55.5% (95% CI 48–63). KM-estimated median not reached; observed median in deceased patients: 20 months. Matched unrelated donor (MUD) recipients had inferior survival vs. matched related donor (MRD)/mismatched related donor (MMRD) (p=0.03). B-ALL: 1/3/5-year OS: 92%/76.4%/69.2% (95% CI 61–77). T-ALL (n=7): 1/3-year OS: 80%/50% (limited by small sample) SCD (n=8): 100% survival at all timepoints; no GVHD observed. GVHD: Any-grade GVHD: 68.5% (AML), 73.3% (B-ALL), 71.4% (T-ALL)—exceeding CIBMTR benchmarks (50–60%). Acute GVHD 35.2% (AML), 43.3% (B-ALL), 28.6% (T-ALL). Chronic GVHD 46.3% (AML), 40% (B-ALL), 57.1% (T-ALL). Conclusion: Despite high GVHD rates, survival outcomes support selective overseas referral for AML/B-ALL patients, particularly younger recipients. SCD results highlight the safety of HSCT in non-malignant disease. These findings underscore the need for local HSCT capacity to mitigate care fragmentation and establish a critical benchmark for UAE programs. Prospective studies should evaluate socioeconomic drivers of referral patterns and GVHD disparities.

Abstract INTRODUCTION Immune checkpoint inhibitors (ICIs) have emerged as a cornerstone of cancer therapy. However, despite their efficacy, ICIs can cause a unique spectrum of autoimmune toxicities known as immune-related adverse events (irAEs). In contrast to irAEs involving other organ systems, hematologic irAEs such as ICI-associated immune thrombocytopenia (ICI-ITP) are less common. As a result, existing data on ICI-ITP are largely confined to isolated case reports, single-center case series, and pharmacovigilance databases lacking granular clinical data. To address this key knowledge gap, we sought to comprehensively characterize the incidence, risk factors, clinical features, treatments, and outcomes associated with ICI-ITP. METHODS We performed a multicenter cohort study of adult patients who initiated ICI therapy at 29 hospitals across 7 major cancer centers in 11 geographically diverse states in the US between 2016-2023. ICI-ITP was defined as a decline in platelet count to <100 x109/L in the absence of an alternative more plausible etiology of thrombocytopenia. Patients with hematologic malignancies were excluded, as were those who received cytotoxic chemotherapy within 30 days prior to thrombocytopenia onset. For each patient identified as having ICI-ITP, we collected data on demographics, comorbidities, medications, laboratory values, treatments, and outcomes. All data were extracted by manual chart review. To identify risk factors for ICI-ITP and to examine its association with death, for each case of ICI-ITP we also collected data on two control patients who initiated ICI therapy at the same site and in the same year but without development of ICI-ITP. We used multivariable logistic regression to identify independent risk factors for ICI-ITP and its recovery (the latter defined according to criteria established by the ITP International Working Group). We used a multivariable Cox model to examine the association between ICI-ITP and its severity with all-cause mortality. RESULTS We identified a total of 214 patients who developed ICI-ITP among 86,648 examined (0.25%). The incidence was highly consistent across sites (range, 0.15–0.30%). Risk factors for ICI-ITP included simultaneous receipt of two different classes of ICIs, additional irAEs, and a lower baseline platelet count. ICI-ITP developed at a median of 8 weeks (IQR, 4–18) following ICI initiation. The median nadir platelet count was 41 x109/L (IQR, 17–64). Six out of 214 patients (2.8%) developed a major bleed, and 16 patients (7.5%) developed a clinically relevant non-major bleed. Cell-bound anti-platelet antibody testing was positive in 6 of 8 patients (75.0%) for whom it was assessed, and median circulating thrombopoietin levels (201 pg/mL [IQR, 178–295]) were similar to those seen in primary ITP. Treatments used included glucocorticoids (49.5%), immune globulin (18.2%), and thrombopoietin receptor agonists (13.6%). Overall, 161 patients (75.2%) recovered from ICI-ITP at a median of 2 weeks (IQR, 1–5) following ICI-ITP onset. Predictors of recovery included additional irAEs and a higher nadir platelet count. Treatment response was observed in 57.0%, 56.4%, and 58.3% of patients within 60 days following initiation of glucocorticoids, immune globulin, and thrombopoietin receptor agonists, respectively. Of 76 patients rechallenged with an ICI, 23 (30.3%) developed recurrent ICI-ITP at a median of 9 weeks (IQR, 2–15); 17 of these 23 patients (73.9%) recovered. Finally, ICI-ITP and its severity were monotonically associated with a higher risk of death (adjusted hazard ratio 2.96 [95% CI, 2.14–4.08] for those with severe ICI-ITP compared to those without ICI-ITP). CONCLUSION In this multicenter study involving patients treated with ICIs at 29 hospitals across the US, we identified 214 patients with ICI-ITP. For the first time, we characterize in detail the incidence, risk factors, clinical features, treatments, and outcomes of ICI-ITP, a relatively novel disease entity. We found that more than half of patients responded to conventional ITP-directed therapies, and that most patients rechallenged did not develop recurrent ICI-ITP. We also found that ICI-ITP was independently associated with an increased risk of death, including a nearly 3-fold increased risk in those with severe ICI-ITP. These findings highlight ICI-ITP as a rare but clinically significant complication of ICI therapy that hematologists must be equipped to recognize and manage.

Abstract Introduction The 2022 WHO/ICC classifications of myeloid neoplasms (MNs) incorporated genomics into the existing clinicopathologic framework, defining new (mono)genetic entities. However, this iterative approach resulted in a mix of pathologically and genomically-defined entities, reliant on arbitrary thresholds and historically-derived boundaries between entities. We hypothesised that integrating genomics with other features, de novo from first principles, might better incorporate modern molecular knowledge to define the biological continuum, evolutionary links and overlapping features across MN. Methods The discovery cohort comprised 6484 thoroughly annotated pts. Contemporary diagnoses included 1817 AML, 1695 MDS, 737 MPN, and 1101 MDS/MPN. Non-malignant pts (AA/CHIP/CCUS/ICUS) were included to explore beyond current neoplastic boundaries. 1407 pts had ≥1 follow-up sample/s. Validation was performed in an independent international cohort (n=2012). An unsupervised random forest algorithm was used to integrate status (and VAF) for 28 mutations, karyotypes, CBC features, sex and age (total parameters 144). Features were selected for potential to be independent of BM sampling. Proximity-based multidimensional scaling/PCA were used to visualize latent structure and identify variance-driving features. Results The model projected pts onto a continuous 3-dimensional space. We first applied clustering seeking 1st-order structure, revealing 4 major clusters (C1–C4). These were further subdivided into 58 distinct subclusters (SCs) by an unsupervised iterative clustering approach. All SCs were enriched for distinctive features, with diverse associations linking genomics to clinicopathological/outcome features. Notably, contemporary diagnoses were distributed widely throughout this landscape, with 9/58 SCs containing cases spanning multiple WHO/ICC MN categories. C1 displayed the most internal heterogeneity, with admixed AML, MDS and MDS/MPN pts. It naturally subdivided down to 4th-order subclustering. Ten SCs were dominated by splicing factor mutations. For example, SF3B1MT segregated into 3 SCs, alone or with high-VAF TET2/ASXL1 or DNMT3A mutations. A separate TET2/SRSF2 SC associated with elevated monocyte%, reflecting a discrete CMML-phenotype genomic entity. NPM1MT formed a distinct SC with FLT3-ITD, distinguished further by VAFs of FLT3, TET2, and NRAS. Current genomically-defined AML subtypes separated in the 4th subclustering. C2 encompassed classical MPN driver mutations across 6 SCs, including a distinct CALRMT group and others defined by variable JAK2 VAFs, co-mutation patterns and other CBC features: eg high-VAF SF3B1MT correlated with PB blast%, and concurrent TET2MT with higher Hb/monocyte counts. C3 was characterized by TP53 alterations, with 5 SCs differing by TP53MT burden, 17p lesions, karyotypic complexity and age. Two SCs, one marked by high TP53 VAF+complex karyotype, the other by ch17 lesions, were associated with the worst OS in the whole cohort. C4 contained most known non-malignant pts, dividing into 4 SCs: 2 largely comprising CCUS and AA, while 2 reflect overlaps/convergence between AA and MDS and MPN, respectively. Repurposing single-cell pseudotime analysis suggested multiple disease origins, with various progression trajectories converging on C3. Projecting them onto the model longitudinal samples moved along these derived paths, consistent with their known progression/remission changes, validating the model's biological relevance and predictive utility. Remarkably, the 58 SCs displayed distinct risks of clonal progression and survival. To maximize potential clinical utility we created a pan-MN prognostic score integrating these features. It performed robustly (c-index 0.84), matching/exceeding existing prognostic tools and validated in an independent dataset. Conclusion Integrating clinicopathologic and genomic data we developed ab initio a continuum model of MNs that transcends historical diagnostic boundaries, captures disease evolution and stratifies clinical outcomes. It may better reflect the core biology and natural histories of specific cases, placing more rational boundaries between discrete entities. Potential advantages extend to treatment selection/trial design (in the era of molecularly-targeted therapies) and personalised prognostication throughout each disease course. Expanded validation is needed to resolve complexity in some areas (notably in C2/C4) and validate/refine this prototype framework.