Pharmacological blockade of rho kinase enhances venetoclax responses in translational models of acute myeloid leukemia.

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy requiring concomitant targeting of critical cellular survival pathways due to resistance and frequent relapse with monotherapies. Venetoclax (VEN), a BCL-2 inhibitor, is one such promising clinical agent best utilized in combination therapies due to transient responses and acquired resistance. Given the involvement of the Rho/ROCK pathway in VEN activity, we combined Rho-associated coiled-coil-containing protein kinase inhibitors (ROCKi) with VEN to achieve superior antileukemic activity. The ROCKi (Fasudil, DJ4, GSK269962A) synergized with VEN to enhance cytotoxicity in both VEN-sensitive and VEN-resistant cell lines in vitro. Among the three ROCKi, GSK269962A (GSK) was best-tolerated in combination with VEN and effectively inhibited leukemia growth across multiple AML cell line-derived xenograft models in vivo. The GSK+VEN combination exhibited additive to synergistic cytotoxicity in primary AML patient cells ex vivo and enhanced antileukemic activity in a patient-derived xenograft model. Additionally, the GSK+VEN combination significantly decreased the clonogenicity of primary AML cells, relatively sparing normal cells. Functional assays demonstrated enhanced apoptosis (Annexin V, caspase-3/7), elevated reactive oxygen species, and mitochondrial depolarization in both VEN-sensitive and VEN-resistant AML cells following combination treatment. Mechanistically, GSK augmented venetoclax responses by down-regulating anti-apoptotic proteins (BCL2, MCL1) and inducing pro-apoptotic mediators (NOXA, MCL1 short isoforms), including in VEN-resistant AML cells. Together, these findings across multiple preclinical AML models demonstrate synergistic antileukemic activity and support combining VEN with ROCKi as a promising therapeutic strategy for AML.