Menin inhibition as a new therapeutic option for the myeloproliferative neoplasms Free

Menin inhibition has emerged as an exciting therapeutic strategy for acute myeloid leukemia associated with KMT2A-rearrangements and NPM1 mutations. While the FDA approved menin inhibitor revumenib is highly active and well tolerated, one potential side effect is thrombocytopenia. To study the mechanism of thrombocytopenia and determine whether this is an on-target effect of revumenib, we first cultured human CD34⁺ cells supplemented with thrombopoietin and treated with vehicle or revumenib under conditions to expand the megakaryocyte lineage. We observed a significant 5.7-fold decrease in the numbers of CD41⁺ megakaryocyte progenitor cells (MkP) as well as a decrease in the generation of mature, polyploid megakaryocytes with revumenib treatment. Single-cell RNA sequencing of these cultures demonstrated that revumenib selectively depleted megakaryocytes and megakaryocyte progenitor cells, while sparing other hematopoietic lineages, including megakaryocyte-erythroid progenitors, erythroid progenitors, common myeloid progenitors, and granulocyte-monocyte progenitors. To confirm on-target activity of revumenib, CRISPR-Cas9–mediated knockout of MEN1 in human CD34⁺ cells recapitulated the selective depletion of megakaryocytes, including a 2-fold decrease in MkPs. Mechanistically, we discovered that expression of the KMT2A-menin target gene MEIS1 is inhibited by revumenib, and that knockout of MEIS1 in human CD34⁺ cultures largely phenocopied the effects of revumenib. Our further observation that overexpression of MEIS1 could not rescue the effects of revumenib suggests that other target genes contribute to megakaryopoiesis. Of note, ziftomenib, a structurally distinct menin inhibitor currently in clinical trials, similarly affected megakaryopoiesis in vitro, indicating this is a class effect. Together, these findings provide strong genetic and pharmacologic evidence that menin plays a key role in megakaryopoiesis.

Next, given that megakaryocyte hyperproliferation is a hallmark of the myeloproliferative neoplasms (MPNs), we hypothesized that menin inhibition might be therapeutically leveraged in this disease. We evaluated the therapeutic potential of revumenib in primary human MPN samples with CALR and JAK2 mutations. In vitro treatment of these MPN specimens resulted in a significant reduction of CFU-Mk and selectively suppressed the expansion of megakaryocytes and megakaryocyte progenitors in culture with a 2.7-fold decrease in MkPs. To assay the activity of revumenib in MPN in vivo, we studied the effect of the drug on disease in the MPLW515L, MPLS504N, and JAK2V617F mouse models. Mice were treated with revumenib-formulated chow, administered either as a single agent or in combination with ruxolitinib. In the MPLW515L and MPLS504N models, revumenib monotherapy led to a significant reduction in leukocyte and platelet counts, a 5.7-fold decrease in megakaryocyte numbers in the bone marrow, and ablation of bone marrow fibrosis. In the JAK2V617F model, revumenib normalized hemoglobin and hematocrit, reduced spleen weight by 4.3-fold, and eliminated bone marrow fibrosis. Of note, combined treatment with revumenib and ruxolitinib further enhanced the suppression of leukocytosis, thrombocytosis, and erythrocytosis, normalized the spleen weight with a 5.8-fold decrease, and suppressed development of bone marrow fibrosis across these models. The reduction in fibrosis was accompanied by a robust downregulation of fibrogenic cytokines, most notably a 6.3-fold decrease in TGF-β. Importantly, revumenib as a single agent and in combination with ruxolitinib also resulted in marked, significant improvement in overall survival. Finally, revumenib was well tolerated in a 12-week study of healthy mice. Together these findings demonstrate that revumenib suppresses megakaryopoiesis both in vitro and in vivo in MPN models and highlight menin inhibition as a potential disease-modifying strategy capable of reversing key pathological features of MPNs.