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Abstract SWOG 1318 evaluated the feasibility of combining the tyrosine kinase inhibitor (TKI) dasatinib with prednisone and blinatumomab in older patients (pts) with Philadelphia chromosome positive (Ph+) B-acute lymphoblastic leukemia (ALL). Here, we present longer follow up (median follow up 5.6 years) with outcomes, predictors of response, and translational medicine studies. Methods: This trial was activated through the NCTN in January 2014 and closed to accrual in April 2021. Pt eligibility included: age > 65 years, Ph+ ALL, no evidence of central nervous system (CNS) disease, and adequate organ function. Treatment has been previously described (Blood Adv 2023; 7(7): 1279-85). Statistics: Categorical and quantitative endpoints comparisons used Fisher's exact and Wilcoxon tests. Survival endpoints used the Kaplan-Meier method and Cox regression models and were landmarked for post-baseline events as needed (i.e., number of cycles). Translational medicine studies: Single cell ATAC seq (10x genomics) was performed on 9 archived cryopreserved diagnostic samples from patients with > 500,000 cells. All samples successfully completed library preparation, sequencing, and demonstrated adequate blast clusters for analysis. Briefly, cryopreserved cells were thawed, and transposases were introduced into nuclei in single cell suspension and used to generate GEM beads. ATAC seq libraries were prepared per manufacture instructions. Libraries were then sequenced on a 25B flow cell on Novaseq X plus (Illumina). The data were analyzed with cloupe (version 9.0.0). Results: Twenty-four eligible patients were enrolled. The median age was 73 years (range 65-87). All pts had newly diagnosed Ph+ ALL. Seventy-nine percent of pts had additional cytogenetic abnormalities. Twenty-two pts (92%) achieved a complete remission (CR) during dasatinib and prednisone induction therapy. Most sites also monitored patient's blood or bone marrow with real-time quantitative PCR to quantify the BCR-ABL1 transcript for molecular response. Of 19 patients analyzed 17 (89%) were in a major or complete molecular remission at some point after treatment, with at least 12 of these patients achieving complete molecular remission. Three patients remain on maintenance. The median follow up for patients who are alive is 5.6 years (range 4.4-8.3). Five- year OS and DFS estimates are 63% (95% CI: 40-78%) and 64% (95% CI: 40-80%). Two patients relapsed in the CNS. One pt proceeded to allogeneic hematopoietic stem cell transplant (HSCT) and 1 to autologous HSCT. Increased age was associated with a decreased chance of achieving CR as best response (median age in responder group 73.2 years [range 65-82.9]; median age in non-responder group 85.5 [range 83.8-87.3]; p=0.02). Patients with extramedullary disease had shorter DFS (HR 0.22, 95% CI 0.04-1.15, p=0.07). Increased number of cycles of blinatumomab received was associated with a trend towards improved OS (HR 0.66, 95% CI 0.41-1.08, p=0.10). Translational medicine studies for chromatin accessibility in the blast clusters demonstrated improved OS in patients with homogeneous blast clusters (HR 0.42, 95% CI 0.06-3.04, p=0.39), high DUX4 differential accessibility (HR 0.26, 95% CI 0.03-2.55, p=0.25), and ATAC seq data corresponding to decreased chromatin accessibility in HOXA2 (HR 0.09, 95% CI 0.01-1.05. p=0.06). Conclusions: Despite an elderly population, this trial demonstrated impressive outcomes with longer follow-up for patients with Ph+ ALL. The number of cycles of blinatumomab and the presence of extramedullary disease may be important factors in outcome. Translational studies suggest additional markers may be predictors of overall survival, and these will need to be studied on larger scale studies. Decreased chromatin accessibility to HOXA2 was associated with a trend towards improved OS. Additional translational medicine will also be presented at the meeting.

Background: PV is a myeloproliferative neoplasm that leads to excessive production of erythrocytes and increased platelet and leukocyte counts. The current standard of care is to use therapeutic phlebotomy (TP) with or without cytoreductive therapy (CRT) to treat PV. Over time, the CRT dose often needs to be increased to treat PV progression. Preliminary results from the phase 2 REVIVE study (NCT04057040) demonstrated that rusfertide was superior to placebo in achieving hematocrit (Hct) levels <45% and reducing or eliminating the need for TP in patients who were phlebotomy-dependent prior to study entry (Kremyanskaya et al. EHA2023. [Abstract LB2710]; Kremyanskaya et al. New Engl J Med 2024;390:723-35).Final data from REVIVE will be presented. Methods: In Part 1 (Weeks 1-29), subcutaneous rusfertide (starting dose: 20 mg q1w) was initiated and titrated to control Hct to <45%. In Part 2 (Weeks 29-41; blinded randomized withdrawal phase), patients were randomized to receive rusfertide or placebo. Randomized patients were eligible to participate in the open-label extension (OLE) portion of the study (Part 3), in which all patients could receive rusfertide and investigators could make CRT dose adjustments. Results: In Part 1, 70 patients were enrolled; 59 were randomized in Part 2. Fifty-eight patients continued to Part 3. As of 9 July 2024, 50 (71.4%), 37 (52.9%), and 17 (24.3%) patients received rusfertide for ≥2, ≥2.5, or ≥3 years, respectively.Overall, median (range) patient age was 57.5 years (27-77); the majority were male (70%) and had high-risk disease (55.7%). Overall, 52.9% and 47.1% of patients were treated with TP alone or TP plus CRT, respectively. Prior to enrollment, the estimated average (mean) phlebotomy rate (EAPR) in patients who enrolled on study was 8.5/year, which was reduced to <1.0/year in Part 1. In Part 2, the EAPR was <1.0/year and 6.6/year in the rusfertide and placebo groups, respectively. For patients who continued onto Part 3 and received rusfertide, the EAPR remained at <1.0/year. In Parts 1, 2, and 3, the mean (SD) weekly average rusfertide dose was 30.7 mg (12.2), 38.5 mg (21.3), and 44.9 mg (20.3), respectively. Rusfertide consistently maintained Hct <45%, including in patients receiving therapy for ≥3 years. Platelets increased following initiation of rusfertide therapy and stabilized over time; mean leukocyte counts remained stable. Prior to enrollment, iron-related parameters were consistent with systemic iron deficiency. Throughout the study, rusfertide resulted in the normalization of mean serum ferritin levels, increased mean transferrin saturation, and increased mean serum iron levels. Overall, mean corpuscular volume increased slightly over the duration of the study. Throughout the study, there was no evidence of increased markers of inflammation (eg, C-reactive protein or interleukin 6). The most common (≥20%) treatment-emergent adverse events (TEAEs) were injection site reactions (85.7%), fatigue (38.6%), COVID-19 (32.9%), pruritus (34.3%), arthralgia (30.0%), dizziness (30.0%), nausea (24.3%), headache (24.3%), and anemia (21.4%). Grade 3 TEAEs occurred in 25.7% of patients.There were no Grade 4 or 5 TEAEs. One patient developed acute myeloid leukemia after treatment discontinuation. After more than 150 patient-years of rusfertide exposure, malignancies (most of which were skin cancers) were reported in 11 patients (all had risk factors that may have contributed to the development of these malignancies). There was no obvious correlation between increasing exposure to rusfertide and malignancies reported. Six thrombotic events (5 arterial and 1 venous) occurred in 5 patients with high-risk PV. Conclusions: In REVIVE, rusfertide added to TP with or without CRT provided long-term durable control of Hct and decreased the need for TP. Patients are eligible to roll over to the phase 2 THRIVE OLE study (NCT06033586), which will continue to assess the long-term safety and efficacy of rusfertide for a total period of up to 5.8 years. The randomized phase 3 VERIFY study (NCT05210790) is ongoing and will evaluate rusfertide vs placebo in PV patients.

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

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.

Abstract Ruxolitinib reduces spleen volume, improves symptoms, and increases survival in patients with intermediate- or high-risk myelofibrosis. However, suboptimal response may occur, potentially because of signaling via the phosphoinositide 3-kinase (PI3K)/protein kinase B pathway. This phase 2 study evaluated dosing, efficacy, and safety of add-on PI3Kδ inhibitor parsaclisib for patients with primary or secondary myelofibrosis with suboptimal response to ruxolitinib. Eligible patients remained on a stable ruxolitinib dose and received add-on parsaclisib 10 or 20 mg, once daily for 8 weeks, and once weekly thereafter (daily-to-weekly dosing; n = 32); or parsaclisib 5 or 20 mg, once daily for 8 weeks, then 5 mg once daily thereafter (all-daily dosing; n = 42). Proportion of patients achieving a ≥10% decrease in spleen volume at 12 weeks was 28% for daily-to-weekly dosing and 59.5% for all-daily dosing. Proportions of patients achieving ≥50% decrease at week 12 in Myelofibrosis Symptom Assessment Form and Myeloproliferative Neoplasms Symptom Assessment Form symptom scores were 14% and 18% for daily-to-weekly dosing, and 28% and 32% for all-daily dosing, respectively. Most common nonhematologic treatment-emergent adverse events were nausea (23%), diarrhea (22%), abdominal pain and fatigue (each 19%), and cough and dyspnea (each 18%). New-onset grade 3 and 4 thrombocytopenia were observed in 19% of patients, each dosed daily-to-weekly, and in 26% and 7% of patients dosed all-daily, respectively, managed with dose interruptions. Hemoglobin levels remained steady. The addition of parsaclisib to stable-dose ruxolitinib can reduce splenomegaly and improve symptoms, with manageable toxicity in patients with myelofibrosis with suboptimal response to ruxolitinib. This trial was registered at www.clinicaltrials.gov as #NCT02718300.

Background: Pacritinib is a JAK1-sparing inhibitor of JAK2/IRAK1/ACVR1 that demonstrated symptom benefit measured by TSS (v2.0, excluding tiredness) vs best available therapy (BAT) in PERSIST-2, which enrolled cytopenic myelofibrosis patients with platelets ≤100×10 9/L. Recent datashowed that in patients with cytopenic MF, a ≥10% reduction in spleen volume at 12 weeks is associated with improved survival in patients treated with pacritinib ( Ajufo H, et al., J Clin Oncol;2023:14(16):Suppl). Surprisingly, this association was not confirmed in patients treated with BAT (82% of whom were on ruxolitinib). The association between other important measures of clinical benefit such as symptom burden reduction and anemia improvement on survival in patients treated with pacritinib has not previously been described. Methods: Patients randomized to pacritinib 200 mg BID and to BAT on PERSIST-2 were included if they were alive and on study at the start of the week 12 efficacy assessment period. Survival was assessed by Total Symptom Score (TSS; v2.0 excluding tiredness) reduction at various thresholds (≥50%, ≥20%, ≥10%, &gt;0%) and transfusion independence (TI) response. TI was assessed among patients who required red blood cell (RBC) transfusion at baseline (within 90 days) and was defined, for the purposes of a landmark survival analysis, as the absence of RBC transfusions over any 12-week period from first dose through week 14 (allowing for a ±2-week window around week 12). Overall survival (OS) was estimated via the K-M method following the landmark approach; survival in responders vs non-responders was compared using the log-rank test. Results: Of the 59 patients treated with pacritinib who had a reduction of TSS≥10%, the median age was 67 years, 25% had a baseline high-risk DIPSS, median platelet count was 61 x10 9/L, median hemoglobin was 9.7 g/dL, and baseline TSS was 19.1. Reduction of TSS≥10% was associated with improved OS, with 1 death among 59 responders vs 4 deaths among 30 non-responders (hazard ratio [HR]=0.12, 95% confidence interval [CI]: 0.01, 0.79] P=0.021, Fig 1a). Similar to spleen volume reduction, the association between TSS response and OS weakened at more stringent TSS response thresholds (Fig 1c, e), with the BAT arm not showing an association between TSS response and OS at any threshold. (Fig 1b, d, f). In order to assess the relationship of specific TSS domains and survival , a landmark OS analysis was performed based on ≥20% reduction in physical function scores (sum of ‘tiredness’ and 'inactivity'), spleen-related symptom scores (sum of 'abdominal discomfort', ‘early satiety’, and 'left rib pain'), and cytokine-related symptom scores (sum of 'itching', ‘night sweats’, and ‘bone pain‘). For cytokine-related symptoms, the number of deaths in PAC responders was significantly different compared to non-responders, with 0 deaths among 35 responders vs 2 among 15 non-responders ( P=0.0325). Conversely the deaths among responders (2/22) vs non-responders (2/20) were not significantly different in the BAT arm. For the physical function and spleen-related symptom subscales, no significant differences between PAC responders and non-responders was observed (HR=0.60; 95% CI [0.05, 6.74] P=0.679) and (HR=0.26; 95% CI 0.02, 2.93, P=0.2435) respectively. Among 36 patients on PAC who received RBC transfusions at baseline, 7 achieved TI over at least a 12-week period up to the time of the landmark analysis. There were no deaths among TI responders compared to 2 (6.9%) among TI non-responders. There were too few TI responders on BAT (only 2 out of 38) to assess the impact on survival. Conclusion: In cytopenic myelofibrosis patients enrolled in PERSIST-2, having a reduction of TSS≥10% on full-dose PAC was associated with OS benefit - a finding that has not been noted with other JAK inhibitors to date. By contrast, this association was not found with BAT, (82% of these patients received ruxolitinib). Thus, reductions in TSS in patients treated with PAC were associated with an OS benefit. It is possible that pacritinib, with its distinctive mechanism of action, may offer a unique survival advantage for MF patients with moderate or severe thrombocytopenia, and further studies are required to understand the potential mechanisms of these distinct clinical observations. Study funded by CTI BioPharma Corp., a Sobi company.

Introduction: Myelofibrosis (MF) is a clonal hematologic malignancy characterized by constitutive JAK-STAT activation and aberrant cytokine signaling. Allogeneic hematopoietic stem cell transplantation (allo-HCT) remains the only potentially curative therapy in MF. The contribution of disease-, patient- and donor-related factors to allo-HCT outcomes remains to be fully elucidated, as well as the presence of somatic mutations in genes such as ASXL1, EZH2, SRSF2, U2AF1 and IDH1/2 which are associated with worse prognosis in MF patients (pts). In this large multi- center retrospective analysis, we aimed to study the impact of clinical and molecular mutations on transplant outcomes. Methods: This analysis including 498 pts from 11 centers in North America and Canada. Univariate proportional-hazard Cox regression analysis stratified by center was used to assess the association of patient, transplant, and disease characteristics on overall survival (OS). Baseline patient demographic data and disease characteristics were selected as covariates in the multivariate analysis. Results: Pts transplanted between 2002-2021 were included in this analysis. Baseline and transplant characteristics are summarized in table 1. The 1- and 2-year OS was 77% (95% CI; 73-81) and 70% (95% CI; 66-74) and non-relapse mortality (NRM) 19% (95% CI: 17-21) and 23% (95% CI: 19-27), respectively. The cumulative incidence (CMI) of relapse at 1- and 2-years was 12% (95% CI; 10-14) and 16% (95% CI; 12-20). The CMI of acute graft versus host disease (aGVHD) grade II-IV was 31% (95% CI; 27-35) at 3 months and 42% (95% CI; 38-46) at 1-year post-transplant and grade was III-IV 13% (95% CI; 11-15) and 18% (95% CI; 14-22), respectively. The CMI of neutrophil engraftment at 1 and 3 months was 90% (95% CI: 87-93) and 97% (95% CI: 95-95) and for platelets 55% (95% CI: 50-59) and 80% (95% CI: 76-83). Univariate analysis included pts (age and gender), transplant (donor type and conditioning regimen intensity) and disease characteristics (DIPSS, mutations, cytogenetics (CG), blood counts, and spleen size). Hemoglobin &gt; 10 g/dL (HR .5, 95% CI .34 -.73 p=3 x 10 -4) and platelets &gt;50× 10 9/L (HR .59, 95% CI .42-.81, p=.0013) prior to transplant were associated with improved OS. High risk DIPSS was associated with decreased OS (p=0.0002). Mutations in ASXL1, EZH2, IDH1/2, U2AF1 and SRSF2 were not associated with decreased OS in this analysis (Figure 1). However, mutations in ZRSR2 were associated with inferior OS (HR 2.07, 95% CI 1.08-3.95, p=.0252). Lastly, JAK2 which had the most frequent mutations was not associated with OS (HR .0.93, 95% CI .65-1.31). There was no association between the CG risk groups and OS. Splenomegaly, measured radiographically, had no impact on OS but was strongly associated with engraftment (better engraftment defined as HR&gt;1). For platelets, spleen size of 15.6-18.9 cm HR of 0.69 (95% CI .47-1, p=.0489) and size &gt;18.9-22.5 cm HR of 0.48 ( 95% CI .33-.7, p=1x10^-4). For neutrophils, spleen size &gt;19.9-22.5 cm had a HR of 0.68, (95% CI .48-.96, p=.0268) and size&gt;22.5 cm had a HR of 0.65 (95% CI .46-.91, p=.0114). Mismatched unrelated (MMURD) and haplo identical donors had no impact on survival but were associated with delayed platelet engraftment; MMURD (HR .67, 95% CI .47-.96, p=.0298) and haploidentical donors (HR .56, 95% CI .39-.8, p=.0017). In a multivariate analysis adjusted for age, gender, highest DIPSS, donor type and conditioning regimen, platelets &gt; 50× 10 9/L (HR .61, 95% CI .44-.87, p=.0053) hemoglobin &gt;10 g/dL (HR .6, 95% CI .4-.9, p=.0244) and lower DIPSS at the time of transplant were associated with improved OS. Conclusions: In this large multicenter analysis only clinical variables; hemoglobin and platelets, were found to be associated with OS after allo-HCT in MF patients. Somatic mutations associated with poor prognosis were not associated with OS suggesting that transplant can overcome their negative impact. Splenomegaly was associated with delayed engraftment but not OS. Interestingly, using alternative donors (MMURD and haplo identical) didn't have a negative effect on OS, possibly reflecting the use of post-transplant cyclophosphamide for GVHD prophylaxis in recent years. These results highlight the importance of biologic factors in the prognostication of outcomes in MF pts undergoing allo-HCT independent of somatic mutations. Supported by the American Society of Hematology (ASH) and MPN Research Foundation