Hoffman, Ronald

Myeloproliferative neoplasm (MPN) patients are at risk of splanchnic vein thromboses (SVT). Prior studies have failed to demonstrate a benefit of hydroxyurea therapy in preventing recurrent thrombosis after SVT, but are limited by small sample sizes and inability to account for starting, stopping, or switching of cytoreductive therapies. To better assess the impact of cytoreductive therapy on thrombosis recurrence, we performed a retrospective cohort study of MPN-SVT patients from the international GASTRO-MPN Consortium, treating cytoreductive therapy as a time-dependent covariate. We identified 757 patients, of which 43% were treated with cytoreductive therapy. During a median follow-up of 7.4 years, 256 patients (34%) had thrombosis recurrence; 145 (19%) had SVT extension/recurrence/TIPS thrombosis, 138 (18%) an thrombosis recurrence outside the splanchnic bed (74% were venous). Additionally, 262 patients (35%) experienced clinically relevant bleeding and 170 (22%) died. After adjusting for age, sex, prior thrombosis, timing of MPN diagnosis relative to SVT, anticoagulation initiation within 30 days of SVT diagnosis, MPN type, JAK2 status, other cancers and cirrhosis, cytoreductive therapy was associated with a decreased risk of recurrent thrombosis (HR 0.67 95%CI 0.50-0.89, p=0.01). This was driven by a lower risk of SVT extension/recurrence (HR 0.62 95%CI 0.42-0.90, p=0.01) but not by extra-splanchnic thrombosis recurrence (HR 0.97 95%CI 0.72-1.30, p=0.82). In a subgroup of patients without erythrocytosis/thrombocytosis at initial SVT (n=275), cytoreductive therapy was associated with a HR 0.65 (95%CI 0.40-1.07, p=0.09) for recurrent thrombosis. These data support the use of cytoreductive therapy in MPN-SVT patients to prevent recurrent thrombosis, particularly SVT extension/recurrence.

Polycythemia vera is characterized by erythrocytosis and increased risk of thrombosis. Sapablursen is an antisense oligonucleotide that suppresses transmembrane serine protease 6 (TMPRSS6), increases hepcidin production, and reduces iron availability for erythropoiesis. IMPRSSION; an ongoing phase 2a, randomized, open-label study includes patients meeting 2016 WHO criteria for polycythemia vera, requiring ≥3 phlebotomies within 6 months of screening and ≥1 phlebotomy within the last 12 weeks. Cohort A (120 or 80 mg) and Cohort B (40 mg) received sapablursen subcutaneously once every 4 weeks (Q4W). The primary efficacy endpoint was the reduction in phlebotomy frequency from baseline to weeks 17-37 in patients who received ≥1 dose. Forty-nine patients received ≥1 sapablursen dose (median age 61 years; 82% male). The baseline mean±SD weekly phlebotomy rate was 0.15±0.07 in Cohort A; 0.17±0.07 in Cohort B and was reduced by -0.10 (95%CI, -0.13, -0.07; n=32;p<0.0001) in Cohort A; -0.10 (95%CI, -0.14, -0.06; n=17;p=0.0001) in Cohort B. Sapablursen reduced the median (IQR) number of phlebotomies from 5.0 (3.0-6.0,Cohort A; 3.5-6.5,Cohort B) at baseline (26-weeks) to 0 (0-1.0) in the efficacy evaluation window (20-weeks) in Cohort A and 1.5 (0-2.5) in Cohort B. Most adverse events were mild or moderate; anemia and fatigue were most common. The mean change in MPN-SAF-TSS at week 37 was -6.21 points (95%CI: -10.56, -1.85, p=0.0052) in Cohort A; -2.71 points in Cohort B (95% CI: -8.33, 2.91, p=0.34). Sapablursen reduced phlebotomy need, improved symptoms, and was safe and well-tolerated in patients with polycythemia vera. (Funded by Ionis Pharmaceuticals; ClinicalTrials.gov: NCT05143957)

Abstract Background Myeloproliferative neoplasms (MPNs) can progress from chronic phase to accelerated or blast phase (MPN-AP/BP), a transition with poor prognosis and limited treatment options. While some abnormalities have been described, the genomic and clonal drivers of transformation remain poorly defined. We characterized mutational and structural alterations in MPN-AP/BP, leveraging paired samples to trace clonal evolution. Methods We profiled 186 samples from 160 individuals, including 159 MPN-AP/BP and 27 chronic-phase MPN samples (26 MF, 1 PV), using targeted sequencing of a 588 gene panel (mean depth: 709x). Paired pre- and post-transformation samples were available for 26 patients (n= 52). A consensus pipeline was used to detect somatic mutations, copy number variations (CNVs), and copy-neutral loss of heterozygosity (cnLOH). Clinical cytogenetic data were integrated when available. Single-cell validation is ongoing. Results Genomic complexity was widespread: 99% of patients harbored ≥1 oncogenic mutation (median 4; range 1–10). In total, 859 mutations were identified, most commonly in JAK2 (68%), ASXL1 (28%), TET2 (26%), SRSF2 (24%), TP53 (22%), and RUNX1 (22%). 684 structural alterations were identified in 86% of patients (median 3; range 1-20), including arm-level (22.5%), segmental (>5 Mb; 60%), and focal (<2 Mb; 9%) alterations. Recurrent events included 9p cnLOH (16%), del(5q) (13%), del(17p) (10%), and focal deletion of 21q22.12 involving RUNX1 (10%). Complex karyotypes (≥3 abnormalities) were observed in 55% of patients. Biallelic mutations accounted for 21% (183/859) of mutations, affecting 58% of patients across 21 genes, most frequently JAK2 V617F (28%), TP53 (17%) and TET2 (14%). Patients with biallelic mutations in these genes had significantly higher blast percentages compared to those with monoallelic mutations (p<0.05), highlighting an association with aggressive disease. In 26 patients with longitudinal samples (chronic phase MPN and MPN-AP/BP), 87% (125/144) of mutations were already detectable during the chronic phase, on average more than 7 years prior to transformation. Only 11% (16/144) of mutations were newly acquired, including additional RUNX1 and TP53 hits, or structural changes that converted pre-existing JAK2 V617F and TP53 R248Q mutations from monoallelic to biallelic via 9p cnLOH or 17p loss, respectively. These findings suggest transformation is often driven by outgrowth of pre-existing high-risk clones, indicating that these clones likely have a competitive advantage and that the mutations within these clones have a cooperative biological interaction which underlies this competitive advantage. To investigate this hypothesis, we examined whether patterns of recurrent co-mutations were identifiable in this cohort. We identified recurrent co-occurring mutations in SRSF2-IDH2, ASXL1-SRSF2, and ASXL1-EZH2, which were enriched at transformation (p < 0.05; Fisher exact test). Importantly, presence of these co-mutations was consistently associated with a higher transformation risk in two independent cohorts of MF patients from Mayo Clinic (n= 405) and University of Florence (n= 518). Clonal architecture analysis revealed that these co-mutations frequently arose within the same malignant clone: 100% for SRSF2-IDH2, 80% for ASXL1-SRSF2, and 85% for ASXL1-EZH2, and are often within the dominant clone. Prior studies have demonstrated mechanistic interplay between SRSF2 and IDH2 (Yoshimi et al.), as well as ASXL1 and SRSF2 (Sui et al.) mutations in myeloid malignancies. We assessed functional synergy of ASXL1-EZH2 using a murine model and identified that dual deletion caused a rapidly fatal myeloid neoplasm with shorter survival than single-gene loss. These results reinforce that functional synergy emerges within a shared cellular context, supporting clonal co-dependence as a driver of progression. Single-cell RNA sequencing of ASXL1-EZH2 mutant cases is ongoing and will be presented. Conclusions Transformation to MPN-AP/BP is driven by gradual clonal remodeling and expansion of pre-existing high-risk abnormalities. Biallelic and multi-hit alterations in TP53, JAK2, TET2, and RUNX1 promote clonal dominance and blast progression. Recurrent co-mutations such as IDH2-SRSF2 and ASXL1-EZH2 arise within the same clone, exhibit functional synergy, and are linked to poor outcomes. These findings support the clinical utility of early clonal and co-mutational profiling to guide risk-adapted intervention.

Abstract Background: Polycythemia vera (PV) is characterized by excessive erythrocytosis and elevated hematocrit (Hct), which is associated with increased risk of thrombotic events. Controlling Hct levels (<45%) is a key therapeutic goal to reduce thrombotic events. Sapablursen (ISIS 702843) is a liver-directed, ligand-conjugated antisense oligonucleotide that suppresses transmembrane serine protease 6 (TMPRSS6) to enhance hepcidin production thereby restricting iron availability and reduced erythrocytosis. We are reporting the topline results of the IMPRSSION study (NCT05143957), an ongoing global, open-label phase 2 trial evaluating the safety and efficacy of sapablursen for Hct control and reducing phlebotomy rate in patients with PV. Methods: Eligible patients met 2016 WHO diagnostic criteria for PV, were required to have >3 phlebotomies within six months prior to screening, including >1 phlebotomy in the last 12 weeks. There were no exclusions for HCT prior to randomization. Patients received monthly subcutaneous doses of sapablursen in Cohort A (high dose) or Cohort B (low dose), during a 37-week treatment period. The primary efficacy endpoint was the reduction in the frequency of phlebotomy during the last 20 weeks of the treatment period (Week 17-37) compared to baseline (defined as the mean weekly phlebotomy rate during the six months prior to screening through the first dose of sapablursen). Phlebotomy was performed when Hct levels were ≥45% or at the investigator's discretion, confirmation of Hct was not required for phlebotomy. Serial assessments of serum hepcidin, TSAT and ferritin were conducted. The 10-item Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (MPN-SAF-TSS) assessed the change in symptoms from baseline to Week 37. Results: Forty-nine (49) patients received at least one dose of sapablursen (full analysis set) in either Cohort A (n=32) or Cohort B (n=17). The median age was 61 years, 40 (82%) were male, and 29 (59%) classified as high risk. The primary endpoint was met at both dose levels. The weekly phlebotomy rate (mean±SD) decreased from baseline of 0.15±0.07 (~7.8/yr) to 0.05±0.09 (~2.6/yr) during the primary endpoint window (Week 17-37) in Cohort A (n=32, p<0.0001; 95%CI, -0.13, -0.07), and from 0.17±0.07 (~8.9/yr) to 0.07±0.07 (~3.6/yr) in Cohort B (n=17, p=0.0001; 95%CI, -0.14, -0.06). The mean MPN-SAF-TSS was reduced at Week 37 by 32% in Cohort A (change from baseline LSM -6.2, p=0.005) and 11% in Cohort B (change from baseline LSM -2.7, p=0.344). The proportion of patients with Hct control (<45%) without phlebotomy from week 17 to 37 in Cohort A and B was 53% (17/32) and 35% (6/17), respectively. Serum hepcidin was increased from baseline values of 0.25±0.6 to 5.05±4.7 nM at Week 13 in Cohort A (p<0.0001) and from 0.68±1.7 to 2.06±3.6 nM in Cohort B (p=0.0142). A sustained low TSAT was observed between Weeks 17-37 (6.0±2.1% and 5.5±2.0% in Cohort A and 8.9±5.0% and 7.0±3.4% in Cohort B). Serum ferritin increased over time from 18±22 ng/mL and 28±58 ng/mL at baseline in Cohort A and B, respectively, to 44±47 ng/mL and 41±85 ng/mL at Week 37, respectively. Sapablursen was generally safe and well-tolerated. The incidence of injection site reactions was 12.2% (6/49). Injection site reactions did not recur following multiple injections, were not progressive and resolved spontaneously. There was one death on study due to transformation to AML which was deemed as not related to the study drug. Conclusions: Treatment of PV patients with sapablursen increased serum hepcidin, controlled Hct, reduced phlebotomy need and improved quality of life in a dose-dependent manner. These findings highlight the potential of sapablursen as a therapeutic approach in PV and support further development.

Abstract Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) have a propensity to transform to an accelerated or blast phase (MPN-AP/BP). The resulting disease has clinically similar manifestations to Acute Myeloid Leukemia (AML) but worse clinical outcomes. Here we present the first comprehensive description of the transcriptomic characteristics of MPN-AP/BP. Our analysis incorporates data from 261 patients of the BeatAML cohort and 56 MPN-AP/BP patients, 11 of whom had paired samples from before and after transformation. We establish that transformed MPN is a transcriptionally distinct entity from de novo AML and chronic phase MPNs. Genomic pathways traditionally associated with MPN pathogenesis, such as IL2/STAT5 signaling and IL6/JAK/STAT3 signaling were enriched in chronic-phase MPNs but are absent in transformed disease, suggesting JAK2 directed therapy may be less effective in this disease phase. We also discovered that gene expression signatures associated with doxorubicin resistance are highly enriched in transformed MPNs, which may explain the lack of efficacy of standard AML therapies. In addition, we identify that lineage composition at the time of transformation may define distinct subsets of MPN-AP/BP patients, which may assist in the future development of novel treatment strategies.

Introduction TP53 alterations (TP53+) are seen in <5% of patients (pts) with chronic myeloproliferative neoplasms (MPNs) but are more common in accelerated/blast phase (MPN-AP/BP) [Luque Paz D, et al 2020]. While pts with low-burden TP53+ (Variant allele frequency (VAF) <5%) may remain stable for years [Kubesova et al, 2018]; biallelic loss of TP53 is thought to confer higher risk for progression [Li et al, 2022] and worse overall survival (OS) than non-TP53+ pts [Rolles et al, 2023]. However, TP53 abnormalities have not been incorporated into currently utilized molecular based prediction models (MIPSS or MIPSS70) or compared with currently validated high molecular-risk (HMR) mutations (mut). We report the outcomes of the largest cohort of TP53+ MPN pts to date in comparison with HMR mut, and identify a VAF cut-off associated with highest risk of progression to MPN-AP/BP. Methods We retrospectively reviewed 2583 MPN pts from Mount Sinai Hospital (MSH) and Memorial Sloan Kettering Cancer Center (MSK) with at least one next generation sequencing (NGS) performed. Deidentified data from an additional cohort of 8 TP53+ MPN pts was received from University of Miami Sylvester Cancer Center (UMiami). Patient characteristics such as MPN subtype, gender, age at MPN diagnosis, driver mutation, thrombosis history were recorded. We also recorded date of transformation to MPN-AP/BP, dates of NGS testing, mutational and cytogenetic data, and survival status. We defined multi-hit TP53 as presence of =/>2 TP53mut, VAF > 50% or TP53 mutation + 17p deletion. Additional cohorts of pts with HMR mut (ASXL1, EZH2, IDH1/2, U2AF1, SRSF2 as per MIPSS70v.2) from MSH and non-TP53+ pts from the MPN-Research Consortium Tissue Bank were used as comparator arms. Patient characteristics were compared between TP53 single-hit and multi-hit using Chi-Sq test for categorical variables and Kruskal-Wallis test for continuous variables. Cumulative incidence function and Kaplan-Meier method were used to compare leukemic transformation and OS, respectively, between groups. Successive VAF levels with minimum groups of 25% of the total cohort were used to identify an optimal VAF cut-off. Results Of the 2583 MPN pts from MSH and MSK, 66 pts (2.6%) were found to have a TP53 mutation. Including 8 additional pts from UMiami, we analyzed a total of 74 TP53+ MPN pts; 40 single-hit and 34 multi-hit. Median age at MPN diagnosis was 61 years with a male predominance (60%). Distribution of driver mut was similar in single-hit vs multi-hit cohort with JAK2V617F being the most common (58%), whereas 11% of pts had triple negative disease . Thrombotic history was available for 45 TP53+ pts, with a high frequency of venous/arterial thrombosis (21/45 or 46.7%) in the TP53+ group as compared to 18.5% in the non-TP53+ MPN cohort (p= 0.0001). A significantly higher number of multi-hit TP53+ pts had a concurrent complex karyotype (79% vs 24% in single-hit; p<.001). MPN diagnosis at the time of detection of TP53+ was ET/PV (25.7%), MF (44.6%), MDS/MPN overlap syndrome (6.8%), MPN-U (2.7%) and MPN-AP/BP (20.3%), respectively. One or more genetic samples with TP53+ was available prior to transformation to MPN-AP/BP in 77% of pts (21/34 multi-hit; 36/40 single-hit) while a TP53+ was detected at the time of MPN-AP/BP diagnosis in the rest. Multi-hit TP53+ was associated with a significantly higher incidence of transformation to MPN-AP/BP as compared to single-hit; [65% vs 17.5%; HR=4.08 (1.71-9.71), p=0.0015]. Compared with HMR mut, multi-hit (HR=2.41; p=0.004) but not single-hit (HR=0.53; p=.277) TP53+ MPN pts were found to have a significantly increased risk of MPN-AP/BP transformation. One-year OS from the time of mutation detection was significantly inferior for both multi-hit (53.3%) and single-hit (75%) TP53+ pts as compared to HMR mut (98.8%, p=<.001). Cut-point analysis identified VAF >36% to be associated with the highest risk of transformation (HR=3.08) with lowest p-value (0.002). Conclusions Multi-hit TP53 alterations are associated with a significantly increased risk of leukemic evolution as compared to previously validated HMR mut, whereas both multi and single-hit TP53 mut are associated with worse OS highlighting the importance of TP53 in MPN disease progression.

Abstract Purpose: Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by systemic symptoms, cytopenias, organomegaly, and bone marrow fibrosis. JAK2 inhibitors afford symptom and spleen burden reduction but do not alter the disease course and frequently lead to thrombocytopenia. TGFβ, a pleiotropic cytokine elaborated by the MF clone, negatively regulates normal hematopoiesis, downregulates antitumor immunity, and promotes bone marrow fibrosis. Our group previously showed that AVID200, a potent and selective TGFβ 1/3 trap, reduced TGFβ1-induced proliferation of human mesenchymal stromal cells, phosphorylation of SMAD2, and collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PC) with wild-type JAK2 rather than JAK2V617F. Patients and Methods: We conducted an investigator-initiated, multicenter, phase Ib trial of AVID200 monotherapy in 21 patients with advanced MF. Results: No dose-limiting toxicity was identified at the three dose levels tested, and grade 3/4 anemia and thrombocytopenia occurred in 28.6% and 19.0% of treated patients, respectively. After six cycles of therapy, two patients attained a clinical benefit by IWG-MRT criteria. Spleen and symptom benefits were observed across treatment cycles. Unlike other MF-directed therapies, increases in platelet counts were noted in 81% of treated patients with three patients achieving normalization. Treatment with AVID200 resulted in potent suppression of plasma TGFβ1 levels and pSMAD2 in MF cells. Conclusions: AVID200 is a well-tolerated, rational, therapeutic agent for the treatment of patients with MF and should be evaluated further in patients with thrombocytopenic MF in combination with agents that target aberrant MF intracellular signaling pathways.