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Abstract Background: Prognostication for patients with non-transformed relapsed/refractory (R/R) follicular lymphoma (FL) is not well defined. Progression of disease within 24 months (POD24) and number of lines of prior therapy are commonly used to benchmark outcomes and for trial eligibility in this space. However, a comprehensive model for risk prediction in R/R FL is lacking. Here we utilize patients from the LEO Consortium for Real World Evidence (CReWE) and Iowa/Mayo Clinic Lymphoma SPORE MER to develop a clinical prediction model for R/R FL. Methods: Patients with grade 1-3A FL were prospectively enrolled at diagnosis in the MER and/or initiated second line or later therapy (2L+) for non-transformed FL at one of the 8 LEO Centers from a previous LEO CReWE study (Casulo et al, Lancet Haem 2022). All available lines of therapy were abstracted; lines of therapy after histologic transformation were not used in the analyses. A management plan of observation was considered as a type of therapy in the 1L setting but not in the 2L+ setting. Clinical variables and outcomes were abstracted at each line of therapy. Variables considered for modeling included demographics, clinical labs, treatment history, and pertinent clinical variables (including FLIPI and FLIPI24 components). Multiple imputation was used to address missing data in modeling; beta-2 microglobulin (B2M) was unable to be imputed due to the amount of missing data. Index therapy was defined as the date of initiation of a line of therapy (2L, 3L or 4L) for non-transformed FL. The primary endpoint for model development was the time from index therapy until the histologic transformation or lymphoma-related death (HT/LD). Cox proportional hazards models were used for model development. Modeling was first performed separately for each line of therapy and then evaluated across lines. Bootstrapping on imputed datasets was used to assess optimism in model performance. Results: N=1001 patients initiated 2L+ therapy and were utilized for modeling. Of these patients, N=654 initiated 3L and N=344 initiated 4L therapy. Median age at index therapy was (60, 61, and 62) for lines 2-4, respectively. Median follow-up by line of therapy was 8.2, 6.1, and 6,1 years and number of HT/LD events for modeling was 272, 154, and 88, respectively. Observed outcomes decreased modestly as the line therapy increased: median event-free (1.6, 1.5, and 1.2 years) and overall survival (17.6 years, 14.5 years, and 12.3 years), for lines 2-4, respectively. 5-year estimates of HT/LD by line of therapy were 21.6% (95% CI: 18.9-24.3), 23.7% (95% CI: 19.9-27.4) and 29.3% (95% CI: 23.3-34.7), respectively. A clinical prediction model was independently developed for each line of therapy; the final model for each line consisted of the same variables: increasing age, male sex, higher LDH, lower hemoglobin, higher white blood cell count, prior immunochemotherapy exposure, and shorter time since initial diagnosis. The parameter estimates for these variables were broadly similar across the different lines of therapy. The model output is an individual patient's risk of HT/LD. Patients with high-risk FLP-R, as defined using the upper quartile of FLP-R risk scores for each line, had observed 5 year HT/LD rates of 43%, 44% and 51% in lines 2-4, respectively. In contrast, patients with the lower quartile of FLP-R risk scores had observed 5 year HT/LD rates of 10%, 6% and 8% in lines 2-4, respectively. The optimism-corrected c-statistic for the FLP-R model across all lines of therapy was 0.685. This added significant information beyond FLIPI diagnosis (c=0.533) FLIPI at index line (c=0.563), the line of therapy (c=0.525), POD24 status (c=0.578), or all 4 variables combined (c=0.614). Conclusions: The FLP-R model identifies a group of patients with non-transformed FL in the R/R setting who are at very high risk of transformation and/or lymphoma-related death across lines of therapy. FLP-R features 4 of the 5 components of the 1L FLIPI24 prediction model (B2M was unavailable for modeling) with the addition of sex, treatment history and time since initial diagnosis. The number of prior therapies is not sufficient to identify high-risk populations for clinical trial enrichment in the R/R FL setting and model discrimination for FLP-R was greatly improved over FLIPI and/or POD24 across lines of therapy. A Shiny app will be provided for model implementation; external validation is planned.

Abstract Introduction: Axi-cel, an autologous anti-CD19 CAR T-cell therapy has shown high and durable response rates and a manageable safety profile among R/R FL pts in the ZUMA-5 trial (Jacobson et al. 2022; Neelapu et al. 2024). Evidence from real-world data showed favorable early outcomes in a broader population using CIBMTR data, with comparable outcomes by ZUMA-5 eligibility, age, lines of therapy (LOT), and prior bendamustine (benda) use (Jacobson et al. 2023). This study investigated long-term outcomes and the association between age, performance status, comorbidities, and therapies given prior to infusion among R/R FL pts treated with axi-cel. Methods: Pts with R/R FL who received commercial axi-cel between 03/2021–10/2023 in the US were identified from the CIBMTR® registry; pts without consent, with prior non-transplant cellular therapy, and FL grade 3B or 3A/3B unspecified or unknown were excluded. Descriptive analyses were done among all pts and by age at infusion (<65 vs ≥65 y), Karnofsky performance score (KPS), presence of hepatic, cardiovascular (CV), or moderate to severe pulmonary comorbidities, prior treatments (benda pre-leukapheresis, autologous hematopoietic stem cell transplant [autoHSCT]), and lymphodepletion (LD) therapy. Multivariable (MV) Cox and logistic regression were used to adjust for confounders. Results: In total, 238 pts from 68 centers were included (data cut-off October 2024). Median age at infusion was 61 yr (range, 29-83; ≥65 yr, 38%), and 79% were non-Hispanic White. KPS of pts was ≤70% (11%), 80% (35%), or 90-100% (54%); 2% had ECOG ≥2. Most (75%) had ≥1 clinically significant comorbidity (hepatic, 6%; CV, 15%; pulmonary, 18%). Median (min, max) prior LOT was 4 (1,13); 74% received benda pre-leukapheresis, and 6% had benda LD therapy. At a median follow-up of 24.1 months, objective response rate (ORR) was 96% (complete response [CR] rate, 91%). The 2-yr (95% CI) DOR, PFS, and OS were 70% (63-77), 64% (57-71), and 84% (78-89) respectively. Grade ≥3 cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) occurred in 4% and 18% of pts (any grade, 74% and 42%), respectively. Prolonged cytopenias by day 30 occurred in 14% of pts (neutropenia [10%] and thrombocytopenia [8%]) while 29% had clinically significant infections at 6 months. Second primary malignancies occurred in 16 pts (7%), with 7 (2%) being therapy-related myeloid neoplasm. The leading primary causes of death (n=34) were relapse/progression (10; 29%), organ failure (7; 21%), and infection 5 (15%). Cumulative incidence of non-relapse mortality at 2-yr was 9%. Outcomes were generally comparable among age, autoHSCT, and comorbidity subgroups. However, effectiveness outcomes differed by prior benda use (Yes vs No): ORR (95% vs 98%); CR (88% vs 98%); DOR (65% vs 89%), PFS (58% vs 84%), and OS (82% vs 91%) at 2 years. By LD therapy (single agent benda vs cyclophosphamide + fludarabine [Cy + Flu]): the ORR was 93% vs 96%; CR rate was 57% vs 93%. On MV analysis, prior benda use was associated with (OR/HR [95% CI]): worse CR (0.02 [<0.01-0.43]), DOR (3.69 [1.51-9.02], and PFS (2.21 [1.12-4.38]). Pts given benda LD therapy had (OR/HR [95% CI]): worse CR rate (0.02 [<0.01-0.16]), DOR (7.59 [2.33-24.72]), and PFS (4.89 [1.79-13.39]) compared to those who received Cy + Flu. CRS and ICANS were lower among those with prior benda use (Yes vs No): any-grade CRS (70% vs 87%); Grade ≥3 CRS (3% vs 8%); any-grade ICANS (36% vs 61%); and grade ≥3 ICANS (17% vs 25%). By LD therapy (single agent benda vs Cy + Flu): the Grade ≥3 CRS and ≥3 ICANS were 0% vs 5% and 7% vs 19% respectively. Any-grade ICANS was higher among those aged ≥ 65 yr vs <65 yr (53% vs 35%). On MV analysis, pts who had prior benda use were less likely to have any-grade CRS (0.30 [0.12-0.75]), and any-grade ICANS (0.23 [0.11-0.50]. Pts ≥ 65 yr had higher any-grade ICANS (2.31 [1.18 – 4.50]). Summary/Conclusion: This long-term follow up of axi-cel in R/R FL shows durable responses and manageable safety similar to ZUMA-5. Outcomes among the elderly and those with comorbidities were generally comparable to the overall R/R FL population. Although benda use pre-leukapheresis was associated with less durable responses, we were unable to determine whether this association is limited to use close to axi-cel infusion, as data on timing of use was unavailable. The associations for benda LD should be interpreted with caution given the small sample size.

Abstract Introduction Cila-cel is associated with a 10-15% risk of delayed neurotoxicity (DNT) with rates of cranial nerve palsies (IEC-NP) and parkinsonism (IEC-PKS) seen at a rate of 10% and 1-4% respectively and can occur as early as 3-4 weeks after infusion. We and others have shown that high post-infusion peak absolute lymphocyte count (ALCpeak) of >3x10^9/L is associated with an increased risk of delayed neurotoxicity (Lim et al., ASCO 2025) whilst the risk was negligible (~1%) when ALCpeak fell below that threshold. Since December 2024, we implemented prophylactic administration of dexamethasone (PPX DEX) when ALC was >3x10^9/L (defined as high ALCpeak). Outcome of these patients are described here. Methods Analysis of clinical outcome included 230 pts treated between Feb 2022 and Nov 2024 as a historical cohort and 102 patients treated between Dec 2024 and May 2025 after the introduction of dexamethasone prophylaxis using an oral dose of 10mg twice a day for at least three days in the high ALCpeak cohort. Results No significant differences were seen between the new and historical cohort in pre-lymphodepletion disease burden (bone marrow plasma cell %, involved light chain or M-spike level), and rates of all/high-grade CRS or ICANS, IEC-HS and rates of tocilizumub use. Median follow-up in the new cohort of 102 pts was 3.6 months (95% CI 3.3-4.2). Eleven (10.8%) developed DNT [3 (2.9%) with IEC-PKS, 8 (7.8%) with IEC-NP]. High ALCpeak of >3x10^9/L was observed in 51 (50%) pts. Among pts with high ALCpeak, DNT was observed in 10 (20%) pts [3 (5.9%) with IEC-PKS, 7 (13.7%) with IEC-NP] whereas among 51 pts with ALCpeak <3x10^9/L, DNT was observed in 1 (2%) pt [1 (2%) with IEC-NP]. In the high ALCpeak cohort, 38 (75%) received DEX [6 (12%) for toxicity management, 32 (63%) PPX DEX]. Of the 38 pts treated with DEX, DNT was observed in 6 (16%) pts (2 (5.3%) IEC-PKS, 4 (10.5%) IEC-CNP). We next compared DNT rates between this new cohort of high ALCpeak pts receiving DEX (n=38) against the historical cohort with high ALCpeak (n=98). Estimated 90-day DNT by Kaplan-Meier method was (19.2% vs 20.5%; p=0.53): IEC-PKS (5.8% vs 7.2%; p=0.60) and IEC-NP (11.7% vs 13.3%; p=0.58). In patients with high ALCpeak, the use of DEX did not appear to significantly reduce the risk of DNT compared to historical controls (HR 0.76, 0.33-1.78), IEC-PKS (HR 0.67, 0.14-3.10) or IEC-NP (0.73, 0.24-2.23). We next compared ALC expansion over the first month post CAR-T infusion (area under the curve, AUC). Among the new cohort of 102 patients, no difference was seen in the AUC of pts who received DEX but did not develop DNT vs those who developed DNT (31.0 vs 57.9, p=0.28); No difference in AUC was seen in the new high ALCpeak cohort receiving DEX vs the historical cohort with high ALCpeak (36.0 vs 43.8, p=0.15) Of the eight cases of IEC-NP, 4 received PPX DEX. No noticeable differences were observed in the severity of presentation, laterality of cranial nerve involvement and rates of multiple cranial nerve involvement between these 4 cases who received PPX DEX and the 16 cases from the historical cohort. At the time of database freeze, 3 of the 4 cases had resolved and 1 was improving. Median time to complete symptom resolution was 38 days vs 69 days in the historical cohort. Of the three cases of IEC-PKS, 2 received PPX DEX. Median time to symptom onset for IEC-PKS was 46 days (vs. 24 days in historical cohort). Both cases had severe symptoms non-responsive to first line high-dose methylprednisolone, second line intrathecal chemotherapy and third line high-dose cyclophosphamide. Both pts subsequently died from sepsis 28 and 67 days post-cyclophosphamide. Conclusion While ALCpeak >3x10^9/L predicts risk of DNT in pts treated with cilta-cel, the use of PPX DEX does not appear to significantly reduce ALC expansion and does not appear to significantly reduce the risk of DNT, IEC-PKS or IEC-NP. Other strategies to reduce ALC or alter T cell functions may need to be considered.

Abstract Background: Allogeneic hematopoietic cell transplantation (allo-HCT) is the only curative option for myelofibrosis (MF) but carries significant non-relapse mortality (NRM). Splenomegaly in MF patients undergoing allo-HCT is linked to delayed engraftment, poor graft function, and worse overall survival (OS). Strategies to reduce spleen size pre-HCT have been explored. Splenic irradiation (SI) offers a non-invasive approach for rapid spleen size reduction, though data on transplant outcomes are limited. Retrospective studies suggest SI just before HCT may reduce relapse and effectively shrink spleens with acceptable toxicity. Methods: We conducted a single-center observational study on MF patients with splenomegaly undergoing allo-HCT between 2022–2024. SI (100 cGy in 5 fractions) was delivered within 6 weeks pre-HCT. Primary endpoints: engraftment kinetics (including primary engraftment failure), time to neutrophil/platelet engraftment, and transfusion independence. Secondary endpoints: OS, progression-free survival (PFS), relapse, NRM, and rates of acute/chronic GVHD. Kaplan–Meier methods were used for OS/PFS; cumulative incidence functions with competing risks were used for relapse/NRM. Results: Thirteen patients were analyzed. Median age was 63 (range 40–74) years, and 54% were male. Eight (62%) patients had primary MF, 3 (23%) post-essential thrombocytosis, and 2 (17%) post-polycythemia vera. Eleven (94.6%) patients had prior Ruxolitinib therapy, and 10 (76.9%) harbored a JAK2 mutation with a median variant allele frequency of 51% (range 34%–94%). DIPSS risk at transplant was low in 1 (7.7%), intermediate-1 in 8 (61.5%), and intermediate-2 in 4 (30.8%) patients. Median pretransplant spleen size was 22.4 (range 14.5–28) cm. Two patients had a history of thrombosis, including 1 with portal vein thrombosis. The median interval between SI and stem cell infusion was 14 (range 10–43) days. The median HCT-CI score was 2 (range 0–6), and the median KPS was 80% (range 80–100%). Most patients (76.9%) received a HLA-matched unrelated donor transplantation, while 3 (23.1%) received haploidentical donor grafts. All grafts used peripheral blood stem cells. Reduced-intensity conditioning (RIC) was used in 11 (84.6%) patients, while 2 (15.4%) received myeloablative conditioning (MAC). Five (38.5%) patients received total body irradiation (TBI) as part of conditioning, with all receiving a TBI dose of 200 cGy. All patients received post-transplant cyclophosphamide (PTCy)-based GVHD prophylaxis. With a median follow-up of 17.1 months, median neutrophil engraftment occurred at 18 (range 14–45) days, platelet engraftment at 30 (range 15–434) days, red blood cell transfusion independence at 35 (range 11–341) days, and platelet transfusion independence at 24 (range 10–312) days. Median hospital stay was 26 (range 14–86) days. Primary engraftment failure occurred in 1 (8.3%) patient. One (7.7%) patient developed veno-occlusive disease. Four (33.3%) patients experienced CMV reactivation, and 3 developed CMV disease requiring systemic therapy. Median post-transplant spleen size was 16.6 (range 12.2–25.2) cm, and 30% of patients achieved >50% spleen size reduction, with a median time of 114 (range 45–212) days, with none having a normal spleen at day 30 post-transplant but 2 (15%) patients having a normal spleen at day 100 post-transplant. At 1 year, OS was 73.3% (95%CI, 51.5–100%), and PFS was 66% (95%CI, 44%–100%). The 1-year cumulative incidence of relapse was 7.6%, while 1-year NRM was 25.7%. Seven (53%) patients developed acute GVHD, with 1 patient experiencing grade III acute GVHD that progressed to sepsis and death at day 248 post-transplant. Two additional deaths occurred (graft failure=1, multiorgan failure=1). Two (15%) patients developed moderate chronic GVHD Conclusion: In this single-center cohort, SI pre-allo-HCT was feasible, tolerated, and associated with promising OS and PFS. Engraftment occurred in >90%, with one case of primary engraftment failure and most achieving transfusion independence within reasonable time frames. SI reduced spleen size in >30%, though acute GVHD was frequent. It remains uncertain whether the incidence and severity of GVHD may be influenced using TBI as part of the conditioning regimen (albeit reduced in intensity) in addition to splenic irradiation. Larger prospective studies are needed to clarify SI's impact on engraftment, transfusion dependence, GVHD, and outcomes in MF patients.

Abstract Background Adult xanthogranuloma (AXG) is a rare clonal histiocytic neoplasm (HN) with a poorly defined mutational landscape. Clinically and immunophenotypically, AXG can resemble other HNs such as Erdheim-Chester Disease (ECD) which frequently harbor MAPK pathway alterations and carry BRAF V600E mutations in close to 50% of cases. However, due to the rarity of AXG, the prevalence of the BRAF V600E mutation and the broader mutational landscape is not well known. In this study, we characterize the mutational profile of AXG. Methods We conducted a retrospective analysis of patients diagnosed with AXG at our institution between January 1, 2016, and July 15, 2025. The study was approved by the institutional review board. To ensure inclusion of true AXG cases, only patients with a confirmed histopathologic diagnosis and without multisystemic involvement or characteristic imaging findings of ECD, such as symmetric long bone osteosclerosis, were included. BRAF alterations were identified by immunohistochemistry (IHC) and/or next-generation sequencing (NGS). We also performed an extensive literature review of mutational studies in AXG and included cases that underwent comprehensive NGS. Results Seventeen patients with AXG were identified. The median age at diagnosis was 40 years (range: 18–75 years). Out of the 17 patients, 11 (65%) reported the face as the primary site of disease, and 11 (65%) had solitary lesions. Of the 17 patients, 13 (76%) underwent BRAF V600E IHC staining, and none tested positive. Twelve (71%) patients had tissue samples analyzed via NGS, and none exhibited the BRAF V600E mutation. Eight of the 12 (67%) patients with NGS testing harbored other alterations involving the MAPK pathway. These included BRAF fusions (n=3), KRAS mutations (n=2), and individual cases with TRAF7 mutation, ALK1 fusion and FGFR1 fusion. One patient was found to have a mutation in WRN, which is not previously reported in AXG. Three patients had no identifiable pathogenic alterations on NGS. Ten patients were monitored without treatment, 2 underwent surgical resections and 3 received chemotherapy (1 had a complete response [CR], 2 achieved a partial response). One patient with FGFR1 fusion was treated with pemigatinib and achieved a CR for over 3 years. One patient with TRAF mutation obtained a CR after treatment with rituximab. We also identified 51 cases of AXG with adequate mutational testing reported in the literature, which reported findings similar to ours. In a retrospective study from France involving 29 patients, MAPK alterations were observed in 55% of cases: however, only 10% harbored BRAF V600E mutations (1). Another analysis of 270 patients with various HN subtypes included 13 individuals with AXG, none had BRAF mutations. MAP2K1 mutations were seen in 31% of patients (2). Taken together, across a combined cohort of 68 AXG patients, the most common alterations were: KRAS mutations (16%), fusions (14%), MAP2K1 mutations (7%) and BRAF V600E (6%). Among fusions, the most involved gene was BRAF (50%), and GAB2 was the most common fusion partner (n=2). In total, 59% of patients had MAPK alterations. These findings collectively underscore the diverse mutational landscape of AXG and highlight the rarity of BRAF V600E mutations relative to closely related HNs. Conclusion We present a series of AXG cases with mutational profiling, from our institution and the published literature. We demonstrate that MAPK alterations are frequently observed in AXG and are driven by heterogeneous mutations. In contrast to other HNs where BRAF V600E mutations are common, we identified no such mutations in our cohort and found only rare cases in the literature. Our institutional data, along with findings from the existing literature, suggest that AXG may have a distinct molecular profile compared to other HNs. A deeper understanding of its mutational landscape may offer insights into disease biology and identify therapeutic targets. ReferencesAnnabi E, Mahévas T, Chasset et al. Clinical, Histopathologic, and Molecular Features and Treatment of Multiple Xanthogranuloma in Adults. JAMA Dermatol. 2025;161(7):765-768. doi:10.1001/jamadermatol.2025.0886.Durham BH, Lopez Rodrigo E, Picarsic J, et al. Activating mutations in CSF1R and additional receptor tyrosine kinases in histiocytic neoplasms. Nat Med. 2019;25(12):1839-1842. doi:10.1038/s41591-019-0653-6

Abstract Background: Patients with myelodysplastic syndromes (MDS) are highly susceptible to infections, with sepsis being a major cause of hospitalization and death. While gender differences in sepsis outcomes have been described in broader populations, their impact among patients with MDS remains poorly defined. Methods: We performed a retrospective cohort study using the National Inpatient Sample (NIS) from 2016 to 2022 to identify adult hospitalizations with co-diagnoses of MDS and sepsis. Patients were stratified by sex: male (n = 47,170) and female (n = 31,365). Multivariable logistic regression was used to evaluate the association between female sex and key outcomes: respiratory failure, encephalopathy, disseminated intravascular coagulation (DIC), Clostridioides difficile infection (CDI), fungal sepsis, and in-hospital mortality. Models were adjusted for demographics, comorbidities, and hospital characteristics. Results: Female sex was independently associated with increased odds of respiratory failure (OR 1.05, 95% CI 1.01–1.08, p = 0.011) and encephalopathy (OR 1.07, 95% CI 1.02–1.12, p = 0.010). There was a nonsignificant trend toward higher odds of CDI (OR 1.14, p = 0.086). No significant sex-based differences were observed for DIC (OR 0.84, p = 0.103), fungal sepsis (OR 0.89, p = 0.598), or in-hospital mortality (OR 0.98, p = 0.653). Conclusion: In this large national analysis of MDS patients hospitalized with sepsis, female patients were more likely to experience respiratory failure and encephalopathy, but sex was not significantly associated with mortality, DIC, or fungal infections. These findings suggest that while certain complications may differ by sex, overall in-hospital survival remains comparable between male and female patients with MDS and sepsis.Keywords: Myelodysplastic syndromes, sepsis, gender disparities, mortality, respiratory failure, encephalopathy, NIS

Abstract Introduction: Although current clinical treatment approaches targeting Bruton Tyrosine Kinase (BTK) and BCL2, either as monotherapy or in combination are highly effective in chronic lymphocytic leukemia (CLL), CLL remains incurable. Identifying novel drugs that are potent and effective in the relapsed/refractory (RR) setting remains an unmet need. Methods: Utilizing the CellTiter-Glo 2.0 Cell Viability Assay, we have developed a preclinical drug screening platform which allows conducting drug sensitivity profiling of primary peripheral blood mononuclear cells (PBMCs) collected from CLL patients to a panel of drugs, in the presence and/or absence of bone marrow stromal cells (BMSCs). This unique system mimics the in vivo stromal microenvironment in CLL and enables testing of multiple drug responses in primary patient samples, particularly when leukemic cell numbers are low. In this study, we employed this high throughput drug screening platform to profile drug sensitivity in CLL B cells after disease progression on a BTK inhibitor (BTKi) to a panel of 12 drugs, including inhibitors of BCL2 (venetoclax and LP-118 [Newave]), AXL (TP-0903), histone deacetylase (panobinostat and belinostat), p53 (eprenetapopt and idasanutlin), proteasome (carfizomib) and Type III Receptor Tyrosine Kinase (crenolanib), next generation BTKi (LP-168 [Newave]), as well as a novel anti-cancer drug transcriptional chemical inducer of proximity (TCIP1) and the natural green tea extract (GTE) product Sunphenon 90D (Taiyo International). After 24-hour drug exposure, leukemic cell viability was measured, killing curves and IC50 levels generated and calculated by nonlinear curve regression in GraphPad Prism. Results: Using the Mayo Clinic CLL Database and the Mayo Clinic CLL Tissue Bank, we identified 47 patients with RR CLL, all of whom experienced disease progressionon a BTKi (35 ibrutinib +/- CD20 antibody, 10 acalabrutinib +/- CD20 antibody, 2 other). Median age at BTKi initiation was 64 years (range, 41-82), and 36 (77%) were male. IGHV status was unmutated in 44 (94%) patients, FISH at diagnosis showed del17p in 11 (27%), del11q in 6 (15%), +12 in 5 (12%), del13q in 12 (30%), and not detected in 6 (15%) patients. TP53 mutation was seen in 13 (32%) patients at the start of BTKi therapy. Median number of lines of CLL therapy prior to start of BTKi was 2 (range, 0–8); 13 patients received BTKi as their first-line therapy. Our drug screening results showed definite responses to all tested drugs based on dose range generated killing curves and IC50 levels for 30 RR CLL patient samples, though results varied. Among 12 drugs tested, LP-118 (0.1nM), venetoclax (2.6nM), carfizomib (2.2nM), TP-0903 (116.2nM), crenolanib (1769nM), and TCIP1 (1805nM) demonstrated the highest killing effects, while the remaining generated killing but at higher doses: belinostat (6800nM), eprenetapopt (4500nM), idasanutlin (4900nM), LP-168 (7500nM) and GTE (55.6uM). We also observed that RR CLL cohort exhibited significantly increased drug resistance to most of the tested drugs in the presence of BMSCs with corresponding increases in IC50s (with vs. without BMSCs, fold-change respectively): LP-118 3.92-fold, venetoclax 1.98-fold, carfilzomib 2.58-fold, TP-0903 1.65-fold, panobinostat 204.23-fold, TCIP1 1.91-fold, crenolanib 1.31-fold, idasanutlin 1.69-fold, belinostat 6.14-fold, LP-168 1.29-fold, eprenetapopt 3.44-fold and GTE 1.08-fold (11 out of 12 with p-values <0.05 except for GTE which was not significant, Mann-Whitney U test). We found that even for three drugs with the strongest killing effect based on IC50 levels (LP-118, venetoclax, carfilzomib), their killing effects were significantly reduced in the presence of BMSC (p=0.0002, 0.0002, and <0.0001, respectively). Conclusions: Our results highlight the spectrum of currently available drugs that show promise for therapeutic use in patients with RR CLL who experience disease progression on BTKi. The killing impact was still seen, albeit diminished, even in the presence of BMSC. Our ongoing work will be to associate the drug profiles with each patient's clinical history, as well as to the comprehensive genetic and epigenetic features of the CLL B cell clone.

Abstract Introduction: Antisense oligonucleotides (ASOs) technology has emerged as a transformative approach in molecular therapeutics, offering precise regulation of gene expression. ASOs are short, synthetic single-stranded nucleic acids that bind to target RNA sequences via Watson–Crick base pairing. Depending on their chemical modifications (e.g., phosphorothioate linkages) and sequence design (e.g., aptamer, gapmer), ASOs can mediate RNA degradation via RNase H, modulate pre-mRNA splicing, or inhibit translation. This targeted mechanism of action positions ASOs as promising treatments for a variety of genetic, inflammatory, and neoplastic diseases. More than 10 ASOs have received regulatory approval. However, safety concerns like injection site reactions, thrombocytopenia, renal toxicity, and liver enzyme elevations have somewhat limited their broader clinical application. Notably, Inotersen and Volanesorsen were associated with severe thrombocytopenic events, including fatalities in phase 3 trials of Volanesorsen. This clinical profile of ASO-associated thrombocytopenia mirrors some aspects of heparin-induced thrombocytopenia (HIT), an immune-mediated condition triggered by anti-platelet factor 4 (PF4) antibodies recognizing PF4–heparin complexes. Hypothesis & Methods: This study investigated the hypothesis that PF4, a positively charged protein, interacts with negatively charged ASOs to form immunogenic complexes that expose neoepitopes, triggering recognition by pathogenic antibodies from HIT patients. Twelve ASOs, Inotersen, Eplontersen, Olezarsen, Fomivirsen, Mipomersen, Tofersen, Nusinersen, Eteplirsen, Golodirsen, Viltolarsen, Casimersen (all FDA approved) and Volanesorsen (EMA approved) were evaluated in this study. All twelve ASOs had lengths ranging from 18 to 30 nucleotides. The association of HIT patient antibodies with ASO-PF4 complexes was evaluated by ELISA and analytical ultracentrifugation. Functional testing was performed with donor platelets treated with ASOs. Results: HIT antibodies recognized PF4–ASO complexes in 7 out of 12 ASOs in a stoichiometry-dependent manner, similar to PF4-heparin complexes, with maximal binding at specific molar ratios. HIT antibodies activated platelets incubated with Inotersen and Volanesorsen, analogous to HIT antibody-mediated activation of heparin-treated platelets in assays such as the serotonin release assay. Interestingly, the addition of Fomivirsen and Eteplirsen induced platelet activation independent of HIT antibodies. Many ASOs have phosphorothioate [PS] linkages, a modification that enhances stability to nuclease digestion and confers additional pharmacokinetic advantages. All ASO-PF4 complexes recognized by HIT antibodies in ELISA and those that supported HIT antibody-mediated platelet activation contained PS linkages. Removal of PS linkages from a PS-containing ASO, Inotersen, abolished antibody binding to PF4-Inotersen complexes, and HIT antibody-mediated platelet activation of Inotersen-treated platelets. Conversely, introducing PS linkages into a non-PS containing ASO, Viltolarsen conferred immunogenic properties to the modified ASO, supporting both recognition by HIT antibodies in ELISA and activation of platelets by HIT antibodies. A platelet binding assay revealed nearly five-fold greater HIT antibody binding to human platelets pretreated with PS-modified ASOs compared to their PS-free counterparts. Analytical ultracentrifugation confirmed that PF4 formed large aggregates immediately upon interaction with PS-containing ASOs. Additionally, we isolated and recombinantly expressed a human monoclonal HIT-like antibody that recognizes PF4–ASO complexes in ELISA and activates ASO-treated platelets in functional assays which could serve as a valuable reagent to investigate ASO-mediated thrombocytopenia.Conclusion: With two ASOs, Fomivirsen and Eteplirsen, direct activation of platelets was noted. Studies with additional ASOs revealed a novel immune mechanism involving ASO-PF4 complex formation and anti-PF4 antibody recognition that can plausibly mediate ASO-induced thrombocytopenia. These findings highlight the key role PS linkages may play in ASO immunogenicity and provide a mechanistic framework for risk mitigation in ASO drug design, supporting the safer development and broader application of ASO therapeutics.

Abstract Introduction: MyeloMATCH (mM), is an National Cancer Institute (NCI)-sponsored precision medicine initiative for newly diagnosed AML/MDS. It consists of an initial screening study (Master Screening and Reassessment Protocol, or MSRP) that involves centralized testing of bone marrow/whole blood, leading to assignment into several genetically driven treatment subprotocols within the mM portfolio. MSRP employs karyotype, 8-15 probe fluorescence in situ hybridization (FISH) and NCI-myeloid (NMAv2) assays to determine ploidy, translocations and mutational status needed for accurate disease subclassification, risk stratification as well as for theragnostic determination. NMAv2, a rapid next generation sequencing assay (TAT<48 hrs), interrogates 45 DNA and 35 RNA fusion driver genes to report 1661 hotspot DNA mutations and 779 targeted RNA fusions, including all relevant fusions in AML except Inv3/t(3;3)/MECOM rearrangement (Yeung et al, 2025). The initial mM MSRP workflow relied on karyotype and FISH assay results to identify fusion positive AML/MDS as per the current testing guidelines/ recommendations as well as to abide by the FDA's requirements under the investigational device exemption (IDE). Here we present concordance analysis between karyotype, FISH and NMAv2 assay to identify relevant fusions in AML/MDS. Methods: First 400 participants enrolled in the mM MSRP were included in this analysis. We examined the results from karyotype analysis analyzing 20 metaphase cells, 8-15 probe FISH analyzing 500 nuclei per probe, and NMAv2 curating fusion read counts greater than 100, performed at the mM labs to determine the prevalence of fusions in this cohort. Concordance analysis was performed to determine clinical utility of the NMAv2 assay to report relevant fusions at the time of initial diagnosis. The concordance analysis excluded biomarkers including Inv3/t(3;3)/MECOM rearrangement, KMT2A-PTD and other rare fusions that are beyond the scope of detection by NMAv2 and/or FISH assay. Results: Of the 400 patients analyzed in this cohort (median age 64, [range 20-95]; 43% female; 15.5% non-white; 9.5% Hispanic), translocations/fusions were reported in 67, 73 and 95 patients by karyotype, 8-15 probe FISH and NMAv2, respectively. The karyotypic analysis reported inv(16)/t(16;16) [15], t(11q23) [13], t(9;22) [10], inv3/t(3;3) [9], t(8;21) [6], t(15;17) [5], t(6;9) [4], t(21q22) [3], t(9q34) [1] and t(10;11) [1]. The FISH reported inv(16)/t(16;16) CBFB::MYH11 [15], t(11q23) KMT2A rearrangement [14], t(9;22) BCR::ABL1[10], inv3/t(3;3) MECOM rearrangement [10], t(8;21) RUNX1::RUNX1T1 [7], t(15;17) PML::RARA [5], t(6;9) DEK::NUP214 [5], t(21q22) RUNX1 rearrangement [3], t(11p15.4) NUP98 rearrangement [3], and t(9q34) ABL1 rearrangement [1]. The NMAv2 reported KMT2A-PTD [26], CBFB::MYH11 [15], KMT2A fusion [14], BCR::ABL1[12], RUNX1::RUNX1T1 [8], PML::RARA [5], DEK::NUP214 [5], RUNX1 fusion [4], NUP98 fusion[3], t(9q34) ABL1 fusion [1], PICALM::MLLT10 [1] and ETV6::MECOM [1]. The concordance analysis between NMAv2 and karyotype assay demonstrated positive percent agreement(PPA) of 100%, negative percent agreement(NPA) of 96.81% and overall agreement (OA) of 97.25% when using karyotype as reference. The concordance analysis between NMAv2 and FISH assay demonstrated PPA of 100%, NPA of 98.81% and OA of 99% when using FISH as reference. Of the 12 cases with discrepant results, 7 were due to presence of cryptic translocations missed by karyotype assay, 3 had suboptimal specimen submitted for karyotype/FISH analysis, 1 had false positive BCR::ABL1 fusion reported by NMAv2 due to low level contamination and 1 had minor subclonal population of leukemic blast with BCR::ABL1 fusion detected only by NMAv2. Conclusion: NMAv2 shows high concordance with karyotype and FISH assays which are the most commonly utilized assays to identify fusions/translocations in AML/MDS. NMAv2 is a faster, relatively cheaper and sample conserving method to identify fusions and is less prone to false negative results than karyotype/FISH assay from suboptimal specimen acquisition and testing. Based on the results above, mM MSRP workflow has been amended with FDA concurrence such that a combination of NMAv2, karyotype and MECOM breakapart FISH assay will be used to identify relevant fusion variants in all patients enrolled in mM, whereas additional specific FISH assay will be limited to cases where discrepant results between karyotype and NMAv2 are reported.

Abstract Background: Systemic AL amyloidosis is an incurable disorder caused by misfolded light chain fibrils. Survival is determined by the extent of cardiac involvement and response to therapy. Mayo 2012 (stage I-IV) and European modified Mayo 2004 (stage I-IIIB) prognostic scores were developed in a historic treatment era, prior to widespread bortezomib and daratumumab use. These no longer discriminate those with the poorest outcomes. We presented a new model sub-stratifying IIIB into a high risk, ‘IIIC’ group, incorporating longitudinal strain (LS) to the European modified score (IIIC: LS >-9% + NT-proBNP >8500ng/L + high-sensitivity troponin T [hs-TnT] >50ng/L) in the bortezomib-era (2015-2019) last year (Khwaja et al, ASH 2024). Here, we present an independent external validation of the IIIC model in the modern treatment era. Methods: The ‘IIIC model’ was derived from a large real-world cohort of adults from the UK National Amyloidosis Centre (2015-2019). Performance was externally validated across Europe (Greece, Italy, Netherlands, Switzerland), USA (2015-2024) and UK (2020-2024). Survival estimates were generated from diagnosis to death or last follow-up using the Kaplan-Meier method and groups compared using Cox regression (using Stata v18). Stage IIIB and IIIC were defined as follows IIIB: LS <-9%, NT-proBNP >8500ng/L, hs-TnT >50ng/L and IIIC: LS >-9%, NT-proBNP >8500ng/L, hs-TnT >50ng/L, respectively. Stage I, II and IIIa were defined as previously described in the European modification of Mayo 2004 staging system. Results: 2493 patients were analysed from 2015-2024 (derivation, n=573; validation: Europe, n=374, USA n=458, UK, n=1088). In the derivation cohort, LS ≥-9% and standard cardiac biomarkers (NT-proBNP 332ng/L and 8500ng/L and hs-TnT>50ng/L) were selected as independent prognostic factors in a multivariable model. In the European and UK validation cohort (n=1462), median age at diagnosis was 67 years (range 35-95) with 1014 (69%) cardiac and 869 (60%) renal involvement. Median difference in involved and uninvolved free light chain (dFLC) was 181 mg/L (range 0-24933), NT-proBNP 1911ng/L (range 42-70000), hs-TnT 45ng/L (range 3-1221) and LS -14.7% (range -3- -28). In the US cohort median NT-proBNP was 1764 (range 13-71000) and hs-TnT 44 (6-687). Applying the new model staging, the patient stages were across Europe and UK were stage I: 224 (15%), II: 627 (43%), IIIA: 396 (27%), IIIB: 139 (10%) and IIIC: 76 (5%), respectively. 592 (41%) were treated with first-line daratumumab-based regimens. In the US dataset stage I: 103 (22%), II: 176 (38%), IIIA: 131 (29%), IIIB: 48 (10%) and IIIC: 16 (3%), respectively. 234 (51%) were treated with first-line daratumumab-based regimens. At a median follow-up of 30 months (95% CI 28-32) in the European and UK validation cohort, estimated median overall survival (OS) was not reached and 2-year OS was 74% (95% CI 72-77). Median survival for stages I-II, IIIA, IIIB and IIIC were not reached (NR), 67, 31 and 10 months, respectively (p<0.001). Hazard ratios for stage II, IIIA, IIIB, IIIC were 2.01 (95% CI 1.32-3.07), 3.51 (95% CI 2.31-5.35), 5.67 (95% CI 3.60-8.91) and 11.12 (95% CI 6.93-17.87), respectively (p<0.001). This was confirmed in the US cohort with a median survival for respective stages were NR, NR, NR, 8 and 2 months (p<0.001). External validation in the European and UK cohorts exhibited good predictive performance: 12-month calibration slope was 1.00 (95% CI 0.81-1.20, p=0.98), Harrel's C was 0.90 (95% CI 0.76-1.00), Royston's D 1.07, R2D 0.21 (95% CI 0.15-0.28). In 1462 patients with dataset available, stage IIIC discriminated the poorest outcome despite a greater proportion treated with first-line daratumumab v IIIB in the validation cohort (59% v 40%, p=0.008). 12-month OS for IIIC v IIIB was 44% (95% CI 32-55) v 69% (95% CI 60-76), specificity for 12-month OS 97% v 92% and diagnostic odds ratio 6.62 v 2.36. Conclusions: This study validates the new staging system from stage I-IIIC with robust identification of an ultra-poor prognostic group (Stage IIIC) in a contemporarily treated patient cohort. Despite novel therapies, the OS remains <12 month in the IIIC group and also poor in stage IIIB with median OS 31 months compared to a median of >5 years for all other stages. This staging system can be considered as a new standard of care for risk stratification of AL amyloidosis. Novel approaches are required for patients with advanced risk.