GS-443902 sodium (GS-441524 triphosphate sodium) is a potent viral RNA-dependent RNA-polymerases (RdRp) inhibitor with IC50s of 1.1 µM, 5 µM for RSV RdRp and HCV RdRp, respectively. GS-443902 sodium is the active triphosphate metabolite of Remdesivir (GS-5734)[1][2]
Reference:
[1]. Siegel D, et al. Discovery and Synthesis of a Phosphoramidate Prodrug of a Pyrrolo[2,1-f][triazin-4-amino] Adenine C-Nucleoside (GS-5734) for the Treatment of Ebola and Emerging Viruses. Med Chem. 2017 Mar 9;60(5):1648-1661.
[2]. Cho A, et al. Synthesis and antiviral activity of a series of 1’-substituted 4-aza-7,9-dideazaadenosine C-nucleosides. Bioorg Med Chem Lett. 2012 Apr 15;22(8):2705-7.
[3]. Warren TK, et al. Therapeutic efficacy of the small molecule GS-5734 against Ebola virus in rhesus monkeys. Nature. 2016 Mar 17;531(7594):381-5.