Harringtonine is a cephalotaxine alkaloid originally found in Cephalotaxus hainanensis Li; it exhibits antiviral and anticancer activities. Harringtonine immobilizes initiated ribosomes, inhibiting protein translation by binding the A site of the 60 S ribosomal subunit and preventing aminoacyl-tRNA binding. Harringtonine inhibits chikungunya virus infection, suppressing replication, RNA production, and viral protein expression. Alone, harringtonine downregulates production of Mcl-1, increases cleavage of PARP, and inhibits cell growth in acute promyelocytic leukemia (APL) cells. Additionally, this compound improves the efficacy of co-administered chemotherapeutic compounds, further inhibiting proliferation and inducing apoptosis in leukemia cells.