Discovery of a 2'-α-Fluoro-2'-β-C-(fluoromethyl) Purine Nucleotide Prodrug as a Potential Oral Anti-SARS-CoV-2 Agent

A novel 2'-α-fluoro-2'-β-C-(fluoromethyl) purine nucleoside phosphoramidate prodrug 15 has been designed and synthesized to treat SARS-CoV-2 infection. The SARS-CoV-2 central replication transcription complex (C-RTC, nsp12-nsp7-nsp8₂) catalyzed in vitro RNA synthesis was effectively inhibited by the corresponding bioactive nucleoside triphosphate (13-TP). The cryo-electron microscopy structure of the C-RTC:13-TP complex was also determined. Compound 15 exhibited potent in vitro antiviral activity against the SARS-CoV-2 20SF107 strain (EC₅₀ = 0.56 ± 0.06 μM) and the Omicron BA.5 variant (EC₅₀ = 0.96 ± 0.23 μM) with low cytotoxicity. Furthermore, it was well tolerated in rats at doses of up to 2000 mg/kg, and a single oral dose of this prodrug at 40 mg/kg led to high levels of 13-TP in the target organ lungs of rats with a long half-life. These findings support the further development of compound 15 as an orally available antiviral agent for the treatment of SARS-CoV-2 infection.