PAN endonuclease-IN-3 is a potent inhibitor of PAN endonuclease, with an IC50 of 17.4 nM against the influenza virus polymerase complex. It demonstrates strong antiviral activity against various strains of current influenza viruses while exhibiting very low cytotoxicity in MDCK cells. In mice models infected with A/WSN/33, PAN endonuclease-IN-3 significantly suppresses viral replication.

PAN endonuclease-IN-3 (Compound 39-(S)) exhibits IAV polymerase inhibitory activity in HEK-293T cells with an IC₅₀ value of 17.4 nM, comparable to Baloxavir (IC₅₀ = 17.8 nM). PAN endonuclease-IN-3 (1-103 nM) strongly inhibits PAN endonuclease with an IC₅₀ of 41.8 nM. Additionally, in the MDCK cell line, PAN endonuclease-IN-3 (46 μL/well, 72 h) demonstrates exceptional antiviral activity with an EC₅₀ of 0.21 nM.

PAN endonuclease-IN-3 (20 mg/kg, Intranasal administration, single dose) suppresses viral replication of the A/WSN/33 virus in the lungs of infected mice.