Rebastinib inhibits cerebral cavernous malformation in a chronic mouse model

Cerebral cavernous malformations (CCMs) are vascular lesions caused by the loss-of-function mutations in one of three CCM genes, CCM1 (KRIT1), CCM2, and CCM3 (PDCD10), or gain-of-function mutation in MAP3K3, which encodes MEKK3. Loss of function in CCM genes leads to pathological activation of MEKK3 signaling. Genetic reduction of MAP3K3 gene dosage or pharmacological inhibition of MEKK3 suppresses CCM formation in mouse models, establishing MEKK3 as a promising therapeutic target for CCM.

In silico screening was performed to identify candidate MEKK3 inhibitors. Therapeutic efficacy was evaluated using a mouse CCM model with brain endothelial cell specific deletion of Ccm3 (Ccm3^BECKO). Drug effects were assessed by micro-computed tomography (micro-CT), magnetic resonance imaging (MRI), gene expression analysis, and survival studies.

We identified rebastinib as a potent inhibitor of MEKK3 kinase activity that suppresses upregulation of MEKK3 downstream target genes induced by CCM2 or CCM3 knockdown. Rebastinib exhibited lower cytotoxicity than ponatinib. Administration of rebastinib either at the stage of CCM lesion initiation or after lesion establishment significantly reduced lesion formation and growth in both the cerebrum and cerebellum of Ccm3^BECKO mice. Rebastinib treatment also decreased expression of the MEKK3 downstream transcription factors Klf2 in brain endothelial cells. Importantly, treatment initiated after lesion establishment significantly prolonged the lifespan of Ccm3^BECKO mice.

These findings demonstrate that oral administration of rebastinib effectively suppresses CCM lesion formation and progression and extends survival in a model mouse of CCM, supporting MEKK3 inhibition as a viable therapeutic strategy for CCM disease.