Adam J. Mead

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)

Novel therapies are needed for myelofibrosis (MF), particularly after Janus kinase (JAK) inhibitor failure. This open-label, phase 1/2 study evaluated bomedemstat, an irreversible inhibitor of lysine-specific demethylase 1, in participants with MF refractory or resistant to, inadequately controlled by, or intolerant of approved therapies. Eighty-nine participants initially received bomedemstat at doses 0.25, 0.5, or 0.6 mg/kg orally once per day, titrated to achieve a target platelet count of ≥50 × 109/L to ≤75 × 109/L. Primary end points were safety and change in spleen volume. Hematologic response and change in symptom burden, bone marrow fibrosis score, and variant allele frequency (VAF) were exploratory. Eighty-seven (97%) participants experienced ≥1 any-cause adverse event (AE), most commonly thrombocytopenia (48%) and dysgeusia (36%); 62 (69%) participants experienced ≥1 grade 3 to 5 AE. Three participants (3%) experienced AEs that led to death; none were related to treatment. Of 35 participants with spleen volume data at week 24, 23 (66%) had a reduction in spleen volume; 9 (26%) had a reduction of ≥20%. Mean platelet and white blood cell counts normalized over 24 weeks; hemoglobin levels remained stable. Participants reported improvement in most symptoms, including fatigue. Of 35 participants with baseline and week 24 data, 8 (23%) had improved bone marrow fibrosis by ≥1 grade per central review, and 21 (60%) were stable. Of 36 participants with CALR, JAK2, or MPL mutations and data at week 24, 56% had a reduction in VAF. Bomedemstat had manageable safety and clinical activity in participants with MF in need of an alternative therapy. This trial was registered at www.ClinicalTrials.gov as NCT03136185.

Targeted immunotherapies have revolutionized outcomes for lymphoid malignancies, but success in myeloid neoplasms is limited by the lack of amenable targets and immunologically hostile tumor microenvironment (TME). Myeloproliferative neoplasms (MPNs) are chronic myeloid blood cancers, a third of which are driven by mutations in calreticulin. Calreticulin mutant protein (mutCALR) binds and activates thrombopoietin receptor (TpoR) and results in the display of the mutCALR-TpoR complex on the extracellular membrane of disease-driving cells, thus exposing a therapeutic vulnerability. Here, we present a chimeric antigen receptor T cell (CAR T cell) therapy that specifically targets mutCALR+ cells, both in vitro and in vivo. The CAR T cell therapy selectively depleted mutCALR+ stem cells in samples from patients with myelofibrosis without affecting healthy stem cells and improved survival in mutCALR leukemia xenograft models. To mimic myelofibrotic marrow, we developed a human “chimeroid” model and showed no decrease in the potency of CAR T cell–mediated target cell killing even in a fibrotic TME. We also devised a method to boost the cell surface expression of mutCALR in CD34+ cells isolated from patients with accelerated/blast phase MPNs (defined as >10% blasts in the peripheral blood or bone marrow), enhancing CAR T cell targeting. This study presents a therapeutic strategy with potential to eradicate mutCALR-driven malignancies and highlights an innovative strategy to evaluate blood cancer–targeting immunotherapies in a relevant TME.

The Phase 3 TRANSFORM-1 study (NCT04472598) evaluated ruxolitinib (RUX) in combination with navitoclax (NAV) or placebo (PBO) in Janus-kinase-inhibitor-naïve adults with intermediate-2 or high-risk myelofibrosis and Eastern Cooperative Oncology Group performance status ≤2. Patients were randomized 1:1 to NAV (200 mg/day starting dose or 100 mg escalated to 200 mg/day) or PBO, with RUX dosed per label. The primary endpoint was ≥35% spleen volume reduction (SVR) at Week 24 (SVR35W24). Secondary endpoints included change from baseline in Total Symptom Score (TSS) at Week 24 and SVR35 at any time. A total of 252 patients (NAV+RUX, n=125; PBO+RUX, n=127; median follow-up 20.3 months) were randomized; >80% had intermediate-2 risk and nearly 50% were high-molecular risk (HMR). SVR35W24 was achieved by 63.2% with NAV+RUX versus 31.5% with PBO+RUX (P<0.0001). Mean change in TSS at Week 24 was not significantly different between NAV+RUX and PBO+RUX (−10.2 vs −11.6; P=0.2852). SVR35 at any time was achieved in 76.8% with NAV+RUX versus 44.1% with PBO+RUX (nominal P<0.0001). A ≥20% variant allele frequency reduction (exploratory endpoint) occurred in 58.5% (95% CI: 49.0-67.5) with NAV+RUX and 45.5% (95% CI: 36.4-54.8) with PBO+RUX. NAV+RUX showed higher hematologic toxicity versus PBO+RUX (Grade 3/4 thrombocytopenia: 54.0% vs 19.2%; Grade 3/4 neutropenia: 40.3% vs 8.8%); diarrhea (any grade: 41.9% vs 16.8%) was also more common. Cytopenias were generally manageable and reversible with dose adjustments.

Chronic myeloid leukemia (CML) and Philadelphia (Ph)-negative myeloproliferative neoplasms (MPN) are generally distinct clonal disorders, with the co-occurrence of BCR::ABL1 rearrangement with concomitant Ph-negative MPN rarely reported. Here we describe the largest known international cohort of Ph-negative MPN and coexisting CML providing important insights into this rare clinical scenario. We performed an international, multicenter, retrospective analysis of patients with concomitant BCR::ABL1 rearrangement and Ph-negative MPN, identifying 61 cases from 30 centers in 7 countries, over a 29-year period (1996–2025). Thirty-one patients (50.8%) had Ph-negative MPN preceding CML, 18 patients (29.5%) had CML preceding Ph-negative MPN, and 12 patients (19.7%) had Ph-negative MPN and CML diagnosed simultaneously. We observed increased TKI resistance and myelofibrotic transformation, especially in patients initially diagnosed with Ph-negative MPN. In this group, 35.4% ( n = 11) progressed to MF, 2 patients to blast-phase MPN, and 69.2% ( n = 18) failed to achieve a complete cytogenetic response. The rare e1a2 BCR::ABL1 transcript was notably prevalent which is associated with TKI resistance and a more aggressive disease course in CML. We described superior survival in those with Ph-negative MPN preceding CML, with median OS not reached, compared with 277 months for CML preceding Ph-negative MPN and 100 months for those diagnosed simultaneously ( p = 0.05).

The bone marrow (BM) is the main site of haematopoiesis in adult life. Our understanding of the pathogenesis of BM-derived blood cancers is limited by lack of spatial contextualisation. While emerging spatial transcriptomic (ST) platforms offer unprecedented opportunities for spatially-resolved cellular phenotyping, we recognise and incorporate the power of AI-based tissue feature detection to enhance ST workflows. We perform ST analysis to define the topology of the normal bone marrow (BM) and BM in myeloproliferative neoplasms (MPNs), profiling 5,104,452 cells across 30 human BM samples. Following rigorous histology-based QC, we identify spatially-restricted trajectories of haematopoiesis and extend our understanding of the haematopoietic stem cell (HSC) niche. We find that BM fibrosis in MPN is associated with expansion of distinct immune and stromal co-enriched cell neighbourhoods. We then present a machine learning (ML)-based model trained on ST data that quantifies BM microenvironmental deviation, identifying heretofore unrecognised inter- and intra-individual sample heterogeneity in MPN. Our study demonstrates the potential for AI-based augmented ST analysis, and redefines our understanding of human BM topology.

Platelets are anucleate blood cells vital for hemostasis and immunity. During cell death and aberrant mitosis, nucleated cells release DNA, resulting in “cell-free” DNA in plasma (cfDNA). An excess of cfDNA is deleterious. Given their ability to internalize pathogen-derived nucleic acids, we hypothesized that platelets may also clear endogenous cfDNA. We found that, despite lacking a nucleus, platelets contained a repertoire of DNA fragments mapping across the nuclear genome. We detected fetal DNA in maternal platelets and cancer-derived DNA in platelets from patients with premalignant and cancerous lesions. As current liquid biopsy approaches utilize platelet-depleted plasma, important genetic information contained within platelets is being missed. This study establishes a physiological role for platelets that has not previously been highlighted, with broad translational relevance.

Acute myeloid leukemia (AML) that evolves from myeloproliferative neoplasm (MPN) is known as post-MPN AML. Current treatments do not significantly extend survival beyond 12 months. B-cell lymphoma-extra large (BCL-xL) has been found to be overexpressed in leucocytes from patients with MPN, making it a potential therapeutic target. We investigated the role of BCL-xL in post-MPN AML and tested the efficacy of DT2216, a platelet-sparing BCL-xL proteolysis-targeting chimera, in preclinical models of post-MPN AML. We found that BCL2L1, the gene encoding BCL-xL, is expressed at higher levels in patients with post-MPN AML than in those with de novo AML. Single-cell multiomics analysis revealed that leukemia cells harboring both MPN-driver and TP53 mutations exhibited higher BCL2L1 expression and elevated scores for leukemia stem cell, megakaryocyte development, and erythroid progenitor than wild-type cells. BH3 profiling confirmed a strong dependence on BCL-xL in post-MPN AML cells. DT2216 alone, or in combination with standard AML/MPN therapies, effectively degraded BCL-xL, reduced the apoptotic threshold, and induced apoptosis in post-MPN AML cells. DT2216 effectively eliminated viable cells in JAK2-mutant AML cell lines, induced pluripotent stem cell–derived hematopoietic progenitor cells, primary samples, and reduced tumor burden in cell line–derived xenograft model in vivo by degrading BCL-xL. DT2216, either as a single agent or in combination with azacytidine, effectively inhibited the clonogenic potential of CD34+ leukemia cells from patients with post-MPN AML. In summary, our data indicate that the survival of post-MPN AML is BCL-xL dependent, and DT2216 may offer therapeutic advantage in this high-risk leukemia subset with limited treatment options.

Chromothripsis, the chaotic shattering and repair of chromosomes, is common in cancer. Whether chromothripsis generates actionable therapeutic targets remains an open question. In a cohort of 64 patients in blast phase of a myeloproliferative neoplasm (BP-MPN), we describe recurrent amplification of a region of chromosome 21q (‘chr. 21amp’) in 25%, driven by chromothripsis in a third of these cases. We report that chr. 21amp BP-MPN has a particularly aggressive and treatment-resistant phenotype. DYRK1A, a serine threonine kinase, is the only gene in the 2.7-megabase minimally amplified region that showed both increased expression and chromatin accessibility compared with non-chr. 21amp BP-MPN controls. DYRK1A is a central node at the nexus of multiple cellular functions critical for BP-MPN development and is essential for BP-MPN cell proliferation in vitro and in vivo, and represents a druggable axis. Collectively, these findings define chr. 21amp as a prognostic biomarker in BP-MPN, and link chromothripsis to a therapeutic target.