CDC42BPB (also known as MRCKβ) is a serine/threonine protein kinase that functions as a critical downstream effector of the small GTPase CDC42, primarily regulating cytoskeleton dynamics and cell migration 1. The kinase phosphorylates key actin regulators including PPP1R12C, MYL9, and PPP1R12A to reorganize the actin cytoskeleton 23. CDC42BPB coordinates with accessory proteins (MYO18A, LURAP1, and FAM89B) to modulate lamellar actomyosin retrograde flow essential for cell protrusion and lamellipodial F-actin dynamics 4. In disease contexts, heterozygous CDC42BPB variants cause Chilton-Okur-Chung neurodevelopmental syndrome; de novo missense, frameshift, and nonsense mutations lead to developmental delay, intellectual disability, autism, hypotonia, and structural brain abnormalities including cerebellar and corpus callosum abnormalities 5. Beyond neurodevelopmental disorders, CDC42BPB shows emerging therapeutic relevance: genome-wide association studies identified CDC42BPB as a potential target for myasthenia gravis 67, and tumor-intrinsic CDC42BPB expression confers resistance to anti-PD-1 immunotherapy in breast cancer, with pharmacological inhibition synergizing with checkpoint blockade 8. CDC42BPB has also been identified in novel oncogenic fusions with ALK in gastrointestinal stromal tumors 9.