STK405759 targets microtubules, modulates STAT1, and enhances ruxolitinib efficacy in myeloproliferative neoplasms

Myeloproliferative neoplasms are clonal hematopoietic disorders characterized by excessive mature blood cells production, dysregulated JAK-STAT signaling, and increased angiogenesis. Current therapies, such as ruxolitinib, improve symptoms but lack disease-modifying effects. This study aimed to evaluate the cytotoxic and mechanistic effects of STK405759, a fully synthetic microtubule targeting agent in myeloproliferative neoplasms models. Three representative myeloproliferative neoplasms cell lines (HEL, SET-2, MEG-01) were treated with STK405759 as a single agent or in combination with ruxolitinib. Cytotoxicity was evaluated by XTT assays, apoptosis via Annexin V/propidium iodide staining, and cell cycle distribution by flow cytometry. Microtubule dynamics were examined by immunoblotting and immunofluorescence. Apoptosis-related proteins, cytokine secretion and JAK-STAT pathway activation were analyzed using antibody arrays. STK405759 showed potent cytotoxicity in JAK2 V617F-positive HEL and SET-2 cells and BCR-ABL1-positive MEG-01 cells. Combination with ruxolitinib yielded synergistic effects in HEL and SET-2 cells. Mechanistically, STK405759 disrupted microtubule organization, reduced α- and β-tubulin polymerization and acetylated α-tubulin, leading to G2/M arrest and apoptosis. In SET-2 cells, STK405759 significantly increased STAT1 phosphorylation while causing its retention in the cytoplasm. Treatment also decreased VEGF secretion in both monocultures and HS-5 stromal co-cultures and induced IL-1β in co-cultures. These findings demonstrate that STK405759 exerts potent cytotoxic activity, disrupts microtubules, modulates STAT1 signaling, reduces VEGF secretion, and induces a distinct cytokine profile, while synergizing with ruxolitinib, supporting its further preclinical development as a potential therapeutic strategy in myeloproliferative neoplasms.