Blood最新文献

Abstract: Drug development for chronic myelomonocytic leukemia (CMML) has failed to parallel the recent success observed in related myeloid neoplasms. To address these shortcomings, the US Food and Drug Administration (FDA) held a "Mini-symposium on CMML: Current State of the Art and Trial Design" in September 2023. This symposium brought together a panel of key FDA regulators and academic experts in CMML drug development to discuss challenges and provide perspectives on future drug development for this disease. The panel explored unique challenges that underlie the lack of therapeutic advances in CMML to date and discussed relevant topics such as clinical trial design, study end points, and key regulatory considerations. This article summarizes the key points of discussion from this symposium to facilitate advancements in the field.

Abstract: B-cell acute lymphoblastic leukemia (B-ALL) is the most common pediatric cancer, with long-term overall survival rates of ∼85%. However, B-ALL harboring rearrangements of the MLL gene (also known as KMT2A), referred to as MLLr B-ALL, is common in infants and is associated with poor 5-year survival, relapses, and refractoriness to glucocorticoids (GCs). GCs are an essential part of the treatment backbone for B-ALL, and GC resistance is a major clinical predictor of poor outcome. Elucidating the mechanisms of GC resistance in MLLr B-ALL is, therefore, critical to guide therapeutic strategies that deepen the response after induction therapy. Neuron-glial antigen-2 (NG2) expression is a hallmark of MLLr B-ALL and is minimally expressed in healthy hematopoietic cells. We recently reported that NG2 expression is associated with poor prognosis in MLLr B-ALL. Despite its contribution to MLLr B-ALL pathogenesis, the role of NG2 in MLLr-mediated leukemogenesis/chemoresistance remains elusive. Here, we show that NG2 is an epigenetically regulated direct target gene of the leukemic MLL-ALF transcription elongation factor 4 (AF4) fusion protein. NG2 negatively regulates the expression of the GC receptor nuclear receptor subfamily 3 group C member 1 (NR3C1) and confers GC resistance to MLLr B-ALL cells. Mechanistically, NG2 interacts with FLT3 to render ligand-independent activation of FLT3 signaling (a hallmark of MLLr B-ALL) and downregulation of NR3C1 via activating protein-1 (AP-1)-mediated transrepression. Collectively, our study elucidates the role of NG2 in GC resistance in MLLr B-ALL through FLT3/AP-1-mediated downregulation of NR3C1, providing novel therapeutic avenues for MLLr B-ALL.

Abstract: Asciminib is a myristoyl site BCR::ABL1 inhibitor approved for patients with chronic-phase chronic myeloid leukemia (CP-CML) failing ≥2 prior lines of therapy. The Australasian Leukaemia and Lymphoma Group conducted the Asciminib Evaluation in Newly Diagnosed CML study to assess efficacy of asciminib for newly diagnosed CP-CML. Patients commenced asciminib 40 mg twice daily. Patients with treatment failure, defined as BCR::ABL1 of >10% at 3 or 6 months, or >1% at 12 or 18 months, received either imatinib, nilotinib, or dasatinib in addition to asciminib. In patients with suboptimal response, defined as levels of 1% to 10% at 6 months, >0.1% to 1% at 12 months, or >0.01% to 1% at 18 months, the asciminib dose was increased to 80 mg twice daily. With a median follow-up of 21 months (range, 0-36), 82 of 101 patients continue asciminib. Most common reasons for treatment discontinuation were adverse events (6%), loss of response (4%), and withdrawn consent (5%). There were no deaths; 1 patient developed lymphoid blast crisis. The coprimary end points were early molecular response (BCR::ABL1 of ≤10% at 3 months), achieved in 93% (96% confidence interval [CI], 86-97%), and major molecular response by 12 months achieved in 79%; (95% CI, 70-87%), respectively. Cumulative incidence of molecular response 4.5 was 53% by 24 months. One patient had 2 cerebrovascular events; no other arterial occlusive events were reported. Asciminib as frontline CP-CML therapy leads to high rates of molecular response with excellent tolerance and a low rate of discontinuation for toxicity. This trial was registered at https://www.anzctr.org.au/ as #ACTRN12620000851965.

Abstract: Menin inhibitors that disrupt the menin-MLL interaction hold promise for treating specific acute myeloid leukemia (AML) subtypes, including those with KMT2A rearrangements (KMT2A-r), yet resistance remains a challenge. Here, through systematic chromatin-focused CRISPR screens, along with genetic, epigenetic, and pharmacologic studies in a variety of human and mouse KMT2A-r AML models, we uncovered a potential resistance mechanism independent of canonical menin-MLL targets. We show that a group of noncanonical menin targets, which are bivalently cooccupied by active menin and repressive H2AK119ub marks, are typically downregulated after menin inhibition. Loss of polycomb repressive complex 1.1 (PRC1.1) subunits, such as polycomb group ring finger 1 (PCGF1) or BCL6 corepressor (BCOR), leads to menin inhibitor resistance by epigenetic reactivation of these noncanonical targets, including MYC. Genetic and pharmacological inhibition of MYC can resensitize PRC1.1-deficient leukemia cells to menin inhibition. Moreover, we demonstrate that leukemia cells with the loss of PRC1.1 subunits exhibit reduced monocytic gene signatures and are susceptible to BCL2 inhibition, and that combinational treatment with venetoclax overcomes the resistance to menin inhibition in PRC1.1-deficient leukemia cells. These findings highlight the important roles of PRC1.1 and its regulated noncanonical menin targets in modulating the menin inhibitor response and provide potential strategies to treat leukemia with compromised PRC1.1 function.