Oral pharmacokinetics and efficacy of oral phospholipid remdesivir nucleoside prodrugs against SARS-CoV-2 in mice

Oral broad-spectrum antivirals are urgently needed for the treatment of many emerging and contemporary RNA viruses. We previously synthesized 1-<i>O</i>-octadecyl-2-<i>O</i>-benzyl-<i>sn</i>-glyceryl-P-RVn (ODBG-P-RVn, V2043), a phospholipid prodrug of GS-441524 (remdesivir nucleoside, RVn), and demonstrated its <i>in vivo</i> efficacy in a SARS-CoV-2 mouse model. Structure-activity relationship studies focusing on the prodrug scaffold identified two modifications, 3-fluoro-4-methoxy-benzyl (V2053) and 4-cyano-benzyl (V2067), that significantly enhanced the <i>in vitro</i> broad-spectrum antiviral activity against multiple RNA viruses when compared to V2043. Here, we demonstrate that V2043, V2053, and V2067 are all orally bioavailable, well-tolerated, and achieve high sustained plasma levels after single oral daily dosing. All three phospholipid prodrugs are significantly more active than RVn <i>in vitro</i> and significantly reduce SARS-CoV-2 lung titers in prophylaxis and treatment mouse models of SARS-CoV-2 B.1.351 infection. On a molar basis, V2043 and V2067 are substantially more active than obeldesivir/GS-5245 and molnupiravir <i>in vivo</i>. Together, these data support the continued development of phospholipid RVn prodrugs for the treatment of SARS-CoV-2 and other RNA viruses of clinical concern.