T-705RTP sodium is a selective and GTP-competitive influenza virus RNA polymerase inhibitor with an IC50 of 0.14 μM and a Ki of 1.52 μM. T-705RTP sodium is the active triphosphate metabolite of T-705 and has potent anti-influenza virus activity. T-705RTP sodium and T-705RMP are detected in MDCK cells treated with T-705. T-705RTP sodium inhibits influenza virus RNA polymerase activity in a dose-dependent and a GTP-competitive manner. T-705RTP sodium inhibits the incorporation of ATP and GTP in a competitive manner with Ki values of 7.72 and 1.56 μM, respectively. T-705RTP sodium inhibits the incorporation of CTP in a mixed-type manner with a Ki value of 11.3 μM, and also inhibits the incorporation of UTP in a noncompetitive manner. The incorporation of a single molecule of T-705RTP sodium (10-1000 μM) inhibits influenza virus RNA strand extension.