Mead, Adam J.

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: 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 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.

Progression of myeloproliferative neoplasms to blast phase (BPMPN) is associated with lack of response to conventional therapies and dire clinical outcomes. Consequently, there is a major unmet need to develop new therapies for BPMPN. Chromothripsis, the process of catastrophic shattering and haphazard repair of chromosomes, is a key contributor to somatic variation in cancer, but this phenomenon has not yet been described in BPMPN. More broadly, whether chromothripsis might result in actionable molecular events that are amenable to targeting remains an open question. To characterise the contribution of structural variants to BPMPN, we first performed integrated copy number and mutation profiling in 64 BPMPN patients by SNP karyotyping and targeted next generation sequencing. We observed a recurrent pattern of chromothripsis that involved chromosome 21, which together with other structural variants led to amplification of a common region of chromosome 21 (‘chr21amp‘) in ~25% of patients (GISTIC q-val<0.01, Fig 1A). Chr21amp was associated with TP53 mutations and a higher number of copy number alterations. Patients with chr21amp had a particularly aggressive and treatment-resistant phenotype, with 0% surviving 12 months compared to 46% in the non-chr21amp pts ( p=0.0007), retaining significance in multivariate analysis including after correction for TP53 mutation status. Whole genome sequencing confirmed that the chromosomal rearrangements resulting in chr21amp occurred by different mechanisms, ranging from simple amplification to highly complex chromothriptic events involving multiple chromosomes. There were no recurrent translocation partners or mutations. The minimally amplified region (MAR) spanned 2.7Mb and contained 24 genes, with a median copy number of 3.5 (range 2.7-8.3) Single-cell transcriptomics combined with allelic resolution genotyping revealed that chr21amp was present in the dominant subclone and occurred subsequent to JAK2V617F and mut TP53 acquisition. Chr21amp was detectable in phenotypic HSCs and throughout early stages of hematopoiesis, but not in mature erythroid cells, consistent with a differentiation block. Of the 24 genes in the minimally amplified region, only one gene, DYRK1A, a serine threonine kinase linked to cell proliferation and survival, was both differentially expressed (single-cell and bulk RNAseq) and differentially accessible (ATACseq). To explore the functional role of DYRK1A in BPMPN we performed shRNA and CRISPR-mediated DYRK1A-knockdown and knockout (KO) in BPMPN cell lines (HEL and SET-2), which led to impaired cell proliferation. The DYRK1A inhibitors EHT1610 and GNF2133 also led to dose-dependent growth inhibition. DYRK1A-KO BPMPN HEL or SET2 cell clones showed a reduced ability to propagate leukemia in vivo with a significant survival advantage vs. wild type control mice. BPMPN chr21amp+ primary patient CD34+ cells were highly sensitive toDYRK1A inhibitors, while healthy control CD34+ cells were unaffected Prior studies have shown that DYRK1A activates the DREAM complex, a transcriptional repressor of DNA-repair pathways. In chr21amp patient cells, the DREAM DNA repair gene signature was significantly downregulated (NES -1.74, q-val <0.001), while conversely in CRISPR DYRK1A KO SET2 cells the transcriptional DNA repair signature was upregulated (NES 1.76, q-val <0.001). In functional assays, CRISPR DYRK1A KO was protective against DNA damage, with a reduction in γ-H2AX foci after etoposide treatment or irradiation ( p<0.01 for both). A second mechanism of leukemogenesis emerged from geneset enrichment analyses, which suggested enhanced JAK-STAT signaling in chr21amp BPMPN cells and downregulation in the CRISPR DYRK1A KO context. We validated this by showing that DYRK1A overexpression activates and potentiates STAT5B transcriptional activity in a luciferase reporter assay. Finally, we noted that the STAT target BCL2 was selectively upregulated in chr21amp cells. BCL2 inhibition showed strong synergy with DYRK1A inhibitors for induction of BPMPN cell apoptosis (Bliss synergy score 15). Collectively, these findings define the chr21amp event as a novel prognostic biomarker in BPMPN. We pinpoint DYRK1A amplification as a central driver of genomic instability and exacerbated JAK-STAT signalling, for the first time linking chromothripsis to a specific druggable target ( Fig 1B).

Myelofibrosis (MF) is a chronic myeloproliferative neoplasm that typically manifests with debilitating symptoms that progressively worsen, negatively impacting patients’ quality of life. Fatigue is a multifactorial and burdensome MF-related symptom due to its severity, persistence, and prevalence, with anemia a contributing factor and major unmet need. Clinical trials of the Janus kinase (JAK)1/JAK2/activin A receptor type 1 inhibitor momelotinib have shown consistent anemia benefits, in addition to improvements in MF-related symptoms. The phase 3 MOMENTUM trial in symptomatic and anemic patients met its primary end point, with a greater proportion having a Myelofibrosis Symptom Assessment Form (MFSAF) Total Symptom Score (TSS) reduction ≥50% at week 24 with momelotinib versus danazol. To support the positive primary end point result, we conducted longitudinal, responder, and time-to-event analyses of patient-reported outcomes from MOMENTUM, as measured by the MFSAF, European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30), and Patient-Reported Outcomes Measurement Information System (PROMIS) assessments. These analyses demonstrated rapid and durable response benefits with momelotinib, with achievement of first TSS response by day 29 and continued improvement over time. Improvements favored momelotinib versus danazol for each MFSAF individual item, and greater improvements were observed for disease- and cancer-related fatigue and physical functioning at week 24, with significant results for multiple items/domains across the 3 assessments. These findings are consistent in demonstrating that momelotinib provides substantial symptom benefit.

7019 Background: High-risk essential thrombocythemia (HR ET) is characterized by thrombocytosis, thrombohemorrhagic events and systemic symptoms. Pts can experience intolerance, inadequate response or loss of response to first-line cytoreductive therapies (hydroxyurea [HU] or interferon alfa-2a). BET protein inhibition is a novel therapeutic strategy that downregulates inflammatory cytokines and may inhibit differentiation and proliferation of abnormal megakaryocytes involved in ET pathogenesis. Results from the Phase 2 MANIFEST study (NCT02158858) suggested potentially encouraging clinical efficacy in pts with myelofibrosis treated with Pelabresib (PELA), an oral, small-molecule, investigational BET inhibitor. Here we present preliminary results from MANIFEST Arm 4 investigating PELA monotherapy in HR ET refractory or intolerant to HU. Methods: Eligible pts had platelets > 600 x 109/L and ≥ 2 symptoms (average score ≥3/ TSS≥15). Pts received PELA monotherapy 225 mg QD. The primary endpoint was complete hematologic response (CHR; normalization of platelet count (≤400 x 109/L), WBC count (≤10 x 109/L) confirmed after one cycle [after 3 weeks]) and normal spleen size. Secondary endpoints included partial HR (PHR; platelets 400–600 x 109/L and WBC ≤10 x 109/L), symptom improvement (≥50% TSS reduction) and safety. Results: As of July 2022, 20 pts with HR ET were treated: median age 64 yrs (42–83), median Hgb 13 (10–16) g/dL, median platelet count 772 (418–1255) x 109/L and median TSS 32.7 (6.9–123). The majority of pts had a hematologic response (90% [18/20] unconfirmed CHR or PHR); confirmed CHR was observed in 40% (8/20) (Table). Median platelet and WBC count at Wk 12 was 446 x109/L and 8.2 x 109/L, respectively. TSS reduction was reported in 86% (12/14 pts); median TSS reduction at Wk 12 was –31%. Hgb levels remained stable through Wk 24. The most common nonhematologic AEs were nausea (60%; 10% Gr 3), diarrhea (35%; 5% Gr 3) and dysgeusia (35%; no Gr 3). Hemorrhagic or thromboembolic events were reported in 30% pts (15% Gr 3). No events of thrombocytopenia and no Gr 4 events or higher were reported. Conclusions: Preliminary results from Arm 4 of the MANIFEST study suggest potential clinical benefit with PELA monotherapy in pts with HR ET refractory or intolerant to HU as supported by hematologic responses and symptom improvement. Safety results are consistent with the known safety profile of PELA and as expected in the underlying study population. Clinical trial information: NCT02158858 . [Table: see text]

7016 Background: Many patients (pts) with myelofibrosis (MF) experience anemia resulting from disease or JAK inhibitor therapy. The open-label, phase 2 ACE-536-MF-001 study (NCT03194542) evaluated the safety and efficacy of luspatercept (LUSPA) for the treatment of MF-related anemia. Methods: Eligible pts comprised 4 cohorts based on transfusion dependence (TD, defined as receiving 4–12 red blood cell [RBC] units/84 days [d] immediately up to cycle 1 d 1) and stable ruxolitinib (RUX) treatment; cohort 1: no TD, no RUX; cohort 2: TD, no RUX; cohort 3A: no TD, RUX; cohort 3B: TD, RUX. Pts received subcutaneous LUSPA 1.0 mg/kg (1.33 mg/kg for pts in cohort 3B expansion) with titration up to 1.75 mg/kg in 21-d cycles. Disease response was assessed at d 169 and treatment extended for pts showing clinical benefit; pts were followed for ≥ 3 years (y) post last dose. The primary endpoint was anemia response (defined as 84 consecutive d: ≥ 1.5 g/dL hemoglobin [Hgb] from baseline without transfusion [cohorts 1 and 3A] or RBC transfusion-free [cohorts 2 and 3B]); secondary endpoints included duration of response (DOR), transfusion frequency, change in Hgb level, and symptom response. Results: Of 95 pts in the ITT group, the most common reason for treatment discontinuation was lack of clinical benefit at d 169 (n = 28). Median (range) age was 71.0 (50–89) y. Most (54.7%) pts had primary MF, intermediate-risk 2 disease (75.8%), and > 2 y since initial diagnosis (74.7%). Median prior RUX therapy was 18.1 months (cohorts 3A/3B) and 84.7% of pts had baseline transfusion burden 6–12 units/84 d (cohorts 2/3B). Mean treatment duration was 42.8 weeks. Cohort 3B had the highest anemia response rate with 26.3% (95% CI, 13.4–43.1) of pts transfusion independent during the primary treatment period and 31.6% (95% CI, 17.5–48.7) transfusion independent during the entire treatment period; median (range) DOR was 448 d (85–1582). In cohort 3B: 19 (50.0%) pts had reduced transfusion burden by ≥ 50% during the primary treatment period; 8 (21.1%) pts achieved mean Hgb increase ≥ 1.5 g/dL from baseline throughout the entire treatment period and 6 (15.8%) achieved a mean ≥ 50% reduction in symptom score from baseline. Overall, 47.4% of pts had ≥ 1 treatment-related adverse event (TRAE), most frequently hypertension (17.9%, 5.3% grade ≥ 3); 3.2% of pts had a serious TRAE. One TRAE led to LUSPA discontinuation. Two (2.1%) pts had transformation to acute myeloid leukemia. Nine pts died on treatment from: post-procedural hemorrhage, pneumonia, intracranial hemorrhage, septic shock, ischemic stroke, multiple organ dysfunction syndrome, renal failure, pneumonitis, and myelofibrosis (n = 1 each); no deaths were considered related to the study drug. Conclusions: In pts with MF, the safety profile of LUSPA was consistent with previous studies and efficacy results showed promising improvements in anemia and transfusion burden in all cohorts. Clinical trial information: NCT03194542 .

PURPOSE Polycythemia vera (PV) is characterized by JAK/STAT activation, thrombotic/hemorrhagic events, systemic symptoms, and disease transformation. In high-risk PV, ruxolitinib controls blood counts and improves symptoms. PATIENTS AND METHODS MAJIC-PV is a randomized phase II trial of ruxolitinib versus best available therapy (BAT) in patients resistant/intolerant to hydroxycarbamide (HC-INT/RES). Primary outcome was complete response (CR) within 1 year. Secondary outcomes included duration of response, event-free survival (EFS), symptom, and molecular response. RESULTS One hundred eighty patients were randomly assigned. CR was achieved in 40 (43%) patients on ruxolitinib versus 23 (26%) on BAT (odds ratio, 2.12; 90% CI, 1.25 to 3.60; P = .02). Duration of CR was superior for ruxolitinib (hazard ratio [HR], 0.38; 95% CI, 0.24 to 0.61; P < .001). Symptom responses were better with ruxolitinib and durable. EFS (major thrombosis, hemorrhage, transformation, and death) was superior for patients attaining CR within 1 year (HR, 0.41; 95% CI, 0.21 to 0.78; P = .01); and those on ruxolitinib (HR, 0.58; 95% CI, 0.35 to 0.94; P = .03). Serial analysis of JAK2V617F variant allele fraction revealed molecular response was more frequent with ruxolitinib and was associated with improved outcomes (progression-free survival [PFS] P = .001, EFS P = .001, overall survival P = .01) and clearance of JAK2V617F stem/progenitor cells. ASXL1 mutations predicted for adverse EFS (HR, 3.02; 95% CI, 1.47 to 6.17; P = .003). The safety profile of ruxolitinib was as previously reported. CONCLUSION The MAJIC-PV study demonstrates ruxolitinib treatment benefits HC-INT/RES PV patients with superior CR, and EFS as well as molecular response; importantly also demonstrating for the first time, to our knowledge, that molecular response is linked to EFS, PFS, and OS.