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Background Blast or accelerated phase myeloproliferative neoplasm (MPN-BP/AP) carries a dismal prognosis, with 3-year survival estimates of <5% (BCJ 2023;108). Patients with MPN-BP/AP were excluded from venetoclax (Ven) plus hypomethylating agent (HMA) clinical trials for acute myeloid leukemia (NEJM 2020;383:617). In the current retrospective study, we examined response patterns and long-term survival of newly-diagnosed MPN-BP/AP patients who received treatment with Ven+HMA, outside of clinical trials. Methods Newly-diagnosed patients with MPN-BP/AP treated with Ven+HMA at the Mayo Clinic, between March 2019 and May 2024, were retrospectively reviewed. Diagnostic criteria were according to the International Consensus Classification (Blood 2022;140:1200). Cytogenetic and molecular studies were performed by conventional karyotype and next-generation sequencing, respectively. All patients received at least one cycle of Ven+HMA (azacitidine 75 mg/m2 days 1-7 or decitabine 20 mg/m2 days 1-5). Response was assessed according to the 2022 European Leukemia Net criteria (Blood 2022;140:1345). Standard statistical analyses were performed using JMP Pro (Version 17.1.0). Results Patient characteristics 70 patients (median age 73 years, 59% males, 48% splenomegaly >14 cm, 4% isolated myeloid sarcoma) with newly-diagnosed MPN-BP (n=58) or AP (n=12) received Ven+HMA with (n=13) or without (n=57) concomitant JAK2 inhibitor. Driver mutation distribution was 69% JAK2, 21% CALR, 6% MPL, and 4% triple negative. Mutations involved ASXL1 (31%), TP53 (28%), TET2 (28%), RUNX1 (25%), SRSF2 (18%), IDH2 (12%), U2AF1 (11%), DNMT3A (9%), IDH1 (7%), and K/NRAS (7%). Karyotype was abnormal in 50 (76%) of 66 informative cases, of which 28 (56%) were complex (CK). Median TP53 mutation variant allele frequency (VAF) was 30% (8-96%) and all evaluable cases displayed CK (n=18). Response and Survival Complete remission (CR; 21%) or CR with incomplete count recovery (CRi; 19%) was documented in 28 (40%) patients with residual MPN in 18 (64%) patients. Median response duration was 5.5 months (1-60 months). After a median follow up of 7 months (1-62 months), 48 (69%) deaths, 13 relapses (46%), and 15 (21%) allogeneic stem cell transplants (ASCT; 12 in CR/CRi) were recorded. Median overall survival (OS) was 9 months and was superior with ASCT (median 22 vs. 8 months; p=0.01). In univariate analysis, transplant-censored survival was superior with CR/CRi (12 vs. 5 months; p<0.01) and IDH1 mutation (33 vs. 8 months; p=0.04) and inferior with CK (7 vs. 10 months; p=0.05), TP53 mutation (5 vs. 10 months; p<0.01), post polycythemia vera myelofibrosis (post-PV MF) (3 vs. 9 months; p=0.01), and splenomegaly >14 cm (5 vs. 16 months; p<0.01). Multivariable analysis confirmed the negative survival impact of not achieving CR/CRi (HR 3.8; p<0.01) and presence of TP53 mutation (HR 4.0; p<0.01); median survival (1/3-year survival rate) was 3 months (10%/0%) in TP53 mutated patients not achieving CR/CRi (n=11) vs. 27 months (65%/28%) in TP53 unmutated cases achieving CR/CRi (n=19) (p < 0.01). Median survival in patients with TP53 mutations or CK who achieved CR/CRi (n=7; 7 months) was inferior to that in treatment responders without TP53 mutations or CK (n=18; 23 months; p=0.01). CR/CRi rates in the presence vs. absence of TP53 mutations were 42% vs. 39% (p=0.80) and of CK (25% vs. 50% (p=0.04). Importantly, responses in the presence of TP53 mutations or CK were too short-lived to allow successful bridging to ASCT (median 2 vs. 9 months; p<0.01). Additional predictors of inferior treatment response included splenomegaly >14 cm (24% vs. 53%; p=0.01), and post-PV MF (0% vs. 46%; p<0.01) while SRSF2 (67% vs. 34%; p=0.04) and IDH2 mutations (75% vs. 35%; p=0.03) were associated with favorable response. In multivariable analysis, CK (p=0.04) and splenomegaly >14 cm (p=0.01) remained independent predictors of inferior response. The use of concomitant JAK2 inhibitor therapy did not impact treatment response (CR/CRi 46% vs. 39%; p=0.62) or survival (median 9 vs. 8 months; p=0.71). Conclusions TP53 mutations and CK undermine the value of Ven+HMA, with or without concomitant JAK2 inhibitor, in enabling successful bridging of newly-diagnosed MPN-BP/AP to ASCT. An alternative treatment approach is advised, in the particular scenario, while the observed 3-year survival rate of 28%, in treatment responders without TP53 mutations, is encouraging.

ABSTRACTSpleen volume reduction (SVR) is a key endpoint in inhibitors of Janus kinase (JAK) inhibitor studies. Retrospective analyses have demonstrated an association between SVR and improved overall survival (OS) among patients treated with ruxolitinib with a platelet count > 100 × 109/L. Whether this association occurs in patients with thrombocytopenia is unclear. Pacritinib, a JAK2/IRAK1/ACVR1 inhibitor, demonstrated improved SVR versus best available therapy (BAT [best available therapy]; including ruxolitinib) in patients with myelofibrosis and platelet counts ≤ 100 × 109/L in the PERSIST‐2 study. Patients on study at the start of the 12‐week SVR window on pacritinib 200 mg twice daily or BAT were included. OS was evaluated among SVR responders versus non‐responders using different SVR thresholds (≥ 35%, ≥ 20%, ≥ 10%, and > 0%). Among patients on pacritinib (n = 89), SVR ≥ 10% demonstrated the greatest separation in OS curves between responders and non‐responders (HR, 0.00; 95% CI, 0.00–0.14; p < 0.01), though SVR ≥ 0% and SVR ≥ 20% were also associated with improved OS. No SVR threshold conferred OS benefit on BAT (n = 84), including ruxolitinib (n = 39). In patients with myelofibrosis and platelets ≤ 100 × 109/L, achieving SVR on pacritinib, but not BAT (including ruxolitinib), was associated with significant OS benefit, suggesting that pacritinib may offer a unique survival advantage in patients with myelofibrosis and thrombocytopenia who achieve any SVR. Trial Registration: ClinicalTrials.gov number: NCT02055781

Abstract The ZRSR2 gene is a member of the spliceosome gene family which are frequently mutated in myeloid neoplasms. ZRSR2 mutations (ZRSR2m) occur in less than 5% of MDS, CMML, and AML. Our study included 164 ZRSR2m patients (98.8% males) and 98 ZRSR2wt MDS control cohort. In the ZRSR2m group, there were 53 MDS (32%), 39 CCUS (24%), 33 MPN (20%), 23 MDS/MPN overlap (14%), 15 AML (9%), and 1 MPAL (0.6%). Most MDS patients were the low blast subtype (n=37, 70%). Twenty-seven MDS patients (51%), and 23 CCUS patients (59%) had absolute monocyte count ≥0.5 x109/L and 18 of 23 MDS/MPN overlap were CMML (78%). Mutations in ZRSR2 were spread across the entire gene. The median number of co-mutations was 2, with TET2 (51%) and ASXL1 (32%) being the most common. U2AF1 and SRSF2, previously described as mutually exclusive with ZRSR2, were found in 10.4% of patients. Median overall survival (OS) was 51 months, and significantly varied among MNs (p=0.004). ZRSR2m MDS patients had better mOS than the MDS control cohort with ZRSR2wt (35 vs 22 months, p=0.013). ZRSR2m patients with isolated TET2 co-mutation and higher hemoglobin showed improved survival, while patients with RUNX1m, higher WBC count showed worse OS.

6574 Background: Pts with MF experience debilitating symptoms that negatively impact health-related quality of life (HRQOL), a burden compounded in those with anemia. Prior analysis of the phase 3 SIMPLIFY-1 (S1) and SIMPLIFY-2 (S2) trials found that achieving transfusion independence at wk 24 was associated with improved PROs, but the association of anemia severity by Hb level with PROs was inconclusive (Mesa, ASCO 2023, Poster 7066). This new post hoc analysis explored the impact of Hb improvement on PROs in pts with MF and anemia. Methods: The pooled treatment-agnostic analysis set included pts with anemia (baseline [BL] Hb <10 g/dL) from 3 phase 3 trials: S1 (JAK inhibitor [JAKi] naive; MMB vs ruxolitinib), S2 (JAKi experienced; MMB vs best available therapy), and MOMENTUM (JAKi experienced; MMB vs danazol). The EQ-5D-5L was administered, and health state index (UK value set) and visual analog scale (VAS) scores derived, in all 3 trials. Patient Global Impression of Change (PGIC) was administered in S1/S2. Hb improvement was defined as an increase of ≥1, ≥1.5, or ≥2 g/dL from BL at wk 24. Multivariate (MV) analyses included change in EQ-5D-5L scores from BL as the dependent variable, with wk 24 Hb improvement and key BL characteristics as independent variables. Results: Mean age of the anemic subpopulation (N=480) was 68.8 y; 62% were male, 81% were White, and 64% had primary MF.436 pts were evaluable for Hb improvement at wk 24; 298 and 297 were evaluable for EQ-5D-5L index and VAS scores, respectively. Mean improvements from BL in index and VAS scores were greater in pts who achieved Hb improvement at any threshold than in those who did not (Table). 241 pts were evaluable for Hb improvement at wk 24 in S1/S2; 215 were evaluable for PGIC. Hb improvement was associated with a higher percentage of pts with any symptom improvement and lower percentage with symptom worsening based on PGIC (Table). In MV analyses, Hb improvement at any threshold was significantly associated with positive change in EQ-5D-5L VAS scores at wk 24 (mean change estimates of 5.5 to 7.3); similar trends were observed in MV analyses for EQ-5D-5L index scores. Conclusions: In these trial populations, Hb improvement at wk 24 was associated with improved HRQOL and symptoms in pts with MF and anemia. These results highlight the value of treatments with anemia-related benefits in improving the pt experience in MF. Clinical trial information: NCT04173494 ; NCT02101268 ; NCT01969838 . [Table: see text]

6582 Background: Although high symptom burden indicates poor survival and informs treatment decisions, little is known about the impact of demographic, clinical, and laboratory features on total symptom score (TSS) in patients with myeloproliferative neoplasms (MPN). Methods: Patients with MPN (polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF)) were identified from the retrospective chart review. TSS, individual symptom scores (fatigue, early satiety, abdominal discomfort, inactivity, concentration problems, fever, night sweats, itching, bone pain, weight loss), demographic characteristics (race, ethnicity, age, gender), clinical features (time since diagnosis, depression status, obesity status, spleen size), laboratory results and season at the time of visit were recorded from the clinical encounter when index assessment of TSS was performed for each patient. Normality was assessed using visual inspection of data distribution, whereas multicollinearity was assessed using various inflation factors. A univariable regression followed by a multivariable regression analysis was conducted using a backward selection approach. A p-value <0.05 indicated a statistically significant association of a given feature with TSS. Results: The chart review identified 252 patients (PV: 78; ET: 81; MF: 93). Mean age was 59 (SD: 17.7), 67 (SD: 13.0), and 68 (SD: 10.9) years for ET, PV, and MF respectively. Most patients were white (PV, MF: 92%; ET: 83%) and females (ET: 75%; PV: 60%; MF: 53%). The TSS of patients was highest with PV (mean: 18.5; SD: 16.9) followed by MF (mean: 18.1; SD: 15.4) and ET (mean: 14.3; SD: 15.9). Fatigue was the most reported symptom whereas the least reported symptoms were fever and weight loss. Univariable regression analyses showed depression (B: 17.7; p=0.02), female gender (B: 10.6; p=0.01), platelet count (B: 0.03; p=0.03), and hemoglobin (Hb) (B: -2.6; p=0.01) in PV patients, depression (B: 19.8, p=2x10-5) in ET patients and depression (B: 11.0, p=0.03), white blood cell (WBC) count (B: 0.2; p=0.01), neutrophil count (B: 0.3, p=0.01), and non-neutrophil WBC count (B: 0.6; p=0.02) in MF patients to have significant association with TSS. Multivariable regression analyses ( Table) showed Hb (B: -2.5; p=0.01) and platelet count (B: 0.02; p=0.03) in PV patients, depression (B: 19.7; p=2x10-5) in ET patients and depression (B: 12.3, p=0.01) and WBC count (B: 0.3; p=0.002) in MF patients to have a significant association with TSS. Conclusions: Depression in ET and MF and low Hb in PV were identified as significant drivers of symptom burden. Identifying and managing patients with these comorbidities could improve their quality of life with a potential survival benefit. [Table: see text]

Mastocytosis is a heterogeneous group of disorders comprising cutaneous mastocytosis, systemic mastocytosis, and mast cell sarcoma. It is associated with a variety of symptoms related to the release of mast cell mediators and mast cell tissue infiltration. Referral to specialized centers with expertise in the management of mastocytosis and multidisciplinary collaboration with subspecialists (eg, allergists for the management of anaphylaxis and drug hypersensitivities, anesthesiologists for invasive procedures or surgery, high-risk obstetrician for pregnancy) is recommended. The NCCN Guidelines for Systemic Mastocytosis provide evidence- and consensus-based recommendations for the diagnosis and comprehensive care of patients with systemic mastocytosis. The multidisciplinary panel of experts convenes at least once a year to review requested changes to the guidelines from both internal and external entities as well as to discuss data on existing and new therapies. These NCCN Guidelines Insights focus on some of the recent updates to the guidelines.

Abstract The ACE-536-MF-001 trial enrolled patients with myelofibrosis (n = 95) into 4 cohorts: patients in cohorts 1 and 3A were non–transfusion dependent (NTD) and had anemia; patients in cohorts 2 and 3B were transfusion dependent (TD); and patients in cohort 3A/3B had stable ruxolitinib treatment before and during the study. All patients received luspatercept (1.0-1.75 mg/kg, 21-day cycles). Treatment was extended if clinical benefit was observed at day 169. The primary end point was anemia response rate (NTD, ≥1.5 g/dL hemoglobin increase from baseline; TD, transfusion-independence) over any 12-week period during the primary treatment period (weeks 1-24). Overall, 14% of patients in cohorts 1 and 3A, 10% in cohort 2, and 26% in cohort 3B met the primary end point. In cohorts 1 and 3A (NTD), 27% and 50% of patients, respectively, had mean hemoglobin increase of ≥1.5 g/dL from baseline. Among TD patients, ∼50% had ≥50% reduction in transfusion burden. Reduction in total symptom score was observed in all cohorts, with the greatest response rate seen in cohort 3A. Overall, 94% of patients had ≥1 adverse event (AE); 47% had ≥1 treatment-related AE (TRAE; 11% grade ≥3), most frequently hypertension (18%), managed with medical intervention. One patient had a serious TRAE leading to luspatercept discontinuation. Nine patients died on treatment (unrelated to study drug). In most patients, ruxolitinib dose and spleen size remained stable. In patients with myelofibrosis, luspatercept improved anemia and transfusion burden across cohorts; the safety profile was consistent with previous studies. This trial was registered at www.ClinicalTrials.gov as #NCT03194542.

Interferons are cytokines with immunomodulatory properties and disease-modifying effects that have been used to treat myeloproliferative neoplasms (MPNs) for more than 35 years. The initial use of interferons was limited due to difficulties with administration and a significant toxicity profile. Many of these shortcomings were addressed by covalently binding polyethylene glycol to the interferon structure, which increases the stability, prolongs activity, and reduces immunogenicity of the molecule. In the current therapeutic landscape, pegylated interferons are recommended for use in the treatment of polycythemia vera, essential thrombocythemia, and primary myelofibrosis. We review recent efficacy, molecular response, and safety data for the two available pegylated interferons, peginterferon alfa-2a (Pegasys) and ropeginterferon alfa-2b-njft (BESREMi). The practical management of interferon-based therapies is discussed, along with our opinions on whether to and how to switch from hydroxyurea to one of these therapies. Key topics and questions related to use of interferons, such as their safety and tolerability, the significance of variant allele frequency, advantages of early treatment, and what the future of interferon therapy may look like, will be examined. Pegylated interferons represent an important therapeutic option for patients with MPNs; however, more research is still required to further refine interferon therapy.