ZIKV-IN-3 (compound 5a), an andrographolide derivatives, is a potent ZIKV NS5 methyl transferase (MTase) inhibitor with an IC 50 value of 18.34 μM. ZIKV-IN-3 inhibits ZIKV replication and infection. ZIKV-IN-3 can be used in research of Zika virus (ZIKV).