• An orally bioavailable marine β-carboline alkaloid with broad bioactivity. Manzamine A hydrochloride specifically inhibits GSK-3β and CDK5 with IC₅₀ values of 10.2 μM and 1.5 μM, respectively. It targets vacuolar ATPases and disrupts autophagy in pancreatic cancer cells. Additionally, it displays potent antimalarial, anticancer, and antiviral (HSV-1) activities, making it a promising lead compound in multiple therapeutic areas.