How, Jonathan

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 Myelofibrosis is characterized by perturbation of the JAK/STAT pathway and upregulation of anti‐apoptotic factors leading to myeloproliferation, bone marrow fibrosis (BMF), extramedullary hematopoiesis, splenomegaly, and cytopenias. Navitoclax, a potent oral B‐cell lymphoma (BCL)‐X L /BCL‐2 inhibitor, promotes apoptosis of malignant myelofibrosis cells. Herein, we present results of Cohort 3 of the Phase 2 REFINE study (NCT03222609), which evaluated efficacy and safety of navitoclax plus ruxolitinib in JAKi‐naïve patients with myelofibrosis. JAKi‐naïve patients with primary or secondary myelofibrosis (≥ 18 years with splenomegaly, DIPSS intermediate‐2 and high‐risk myelofibrosis, and ECOG 0–2) and platelet count > 100 × 10 9 /L were enrolled and treated with navitoclax 100 mg once daily (QD) or 200 mg QD according to platelet count (≤ 150 × 10 9 /L or > 150 × 10 9 /L, respectively). Ruxolitinib was given twice daily (dose per label). Primary endpoint: spleen volume reduction of ≥ 35% (SVR 35 ) at week 24. Secondary endpoints: ≥ 50% reduction in total symptom score (TSS 50 ) at week 24, change in grade of BMF, anemia response, and safety. Thirty‐two patients received ≥ 1 dose of navitoclax plus ruxolitinib. Median (range) duration of follow‐up was 44 months (5–58). 63% (20/32) of patients achieved SVR 35 at week 24; median (range) time to first SVR 35 was 12 weeks (11─48). Of 24 evaluable patients, 21% achieved ≥ 50% reduction in driver gene variant allele frequency (VAF). Of 27 evaluable patients, 11 (41%) achieved TSS 50 at week 24; median (range) time to first TSS 50 of 3 weeks (0─16). BMF improved from baseline by ≥ 1 grade in 13/27 patients (48%) at any time on study. Anemia response rates were 38% (5/13) for transfusion‐independent and 100% (2/2) for transfusion‐dependent patients. No bleeding events or deaths were attributed to navitoclax. These findings suggest navitoclax plus ruxolitinib has a tolerable safety profile and provides clinically meaningful improvements for JAKi‐naïve patients with myelofibrosis. Trial Registration NCT03222609.

7015 Background: Ruxolitinib (RUX), a Janus kinase (JAK) 1/2 inhibitor, is the current standard of care for patients (pts) with myelofibrosis (MF) that improves splenomegaly and disease symptoms with limited impact on disease biology. Many pts lose response over time, highlighting an unmet need for novel therapies. Navitoclax (NAV) is an oral, small-molecule inhibitor of BCL-XL and BCL-2 that has a synergistic effect when used in combination with JAK inhibitors to enhance apoptosis. This ongoing, open-label, multicenter, phase 2 trial (NCT03222609) is evaluating the efficacy and safety of NAV with/without RUX in pts with MF. Here, we report results from JAK inhibitor-naïve pts treated with NAV+RUX. Methods: Enrolled pts had primary or secondary MF with splenomegaly (DIPSS ≥INT-1) and did not receive prior JAK-2 therapy or bromodomain and extraterminal motif (BET) inhibitors. Pts initiated NAV at 100 mg QD or 200 mg QD if baseline (BL) platelet count was ≤150 × 109/L or >150 × 109/L, respectively. RUX was given BID with starting dose based on BL platelet count per local label. The primary endpoint was spleen volume reduction of ≥35% (SVR35) from BL at wk 24. Key secondary endpoints were ≥50% reduction in total symptom score (TSS50), bone marrow (BM) fibrosis reduction, and anemia response. Adverse events (AEs) were monitored throughout the study. Results: As of Oct 04, 2021, 32 pts received NAV+RUX. Median duration of f/u was 6.1 (range, 1.9 ─ 18.6) mos. 28 (88%) pts received NAV 200 mg and 4 (13%) received 100 mg OD. Median age was 69 (44 ─ 83) yrs, and median spleen volume was 1889.08 cm3 (645.6 ─ 7339.6). Median NAV and RUX exposures were 24.1 (5.1 ─ 80.9) and 20.1 (0.1 ─ 80.1) wks, respectively. 31 (97%) pts reported ≥1 AE (Grade ≥3 AEs, 25 [78%]; serious AEs, 6 [19%]). Most common Grade ≥3 AEs were anemia (34%), thrombocytopenia (31%), and neutropenia (19%). 3 (9%) and 2 (6%) pts reported an AE leading to NAV and RUX discontinuation, respectively, and 2 (6%; 1 PD, 1 cardiac disorder unrelated to NAV) AEs led to death ≤30 days after last NAV dose. SVR35 was achieved by 52% of evaluable pts at wk 24 (SVR35 in INT-2, 50%; HR, 33%) and by 76% at any time on treatment (Table). Median time to first SVR35 was 12.1 (11 ─ 47) wks. Conclusions: The combination of NAV+RUX was well tolerated and demonstrated early and robust reductions in spleen volume, anemia, and BM fibrosis in pts without prior JAK-2 inhibitor exposure. SVR35, TSS50, and BM fibrosis improved over time. Clinical trial information: NCT03222609. [Table: see text]