Discovery of a β-<scp>d</scp>-2′-Deoxy-2′-α-fluoro-2′-β-<i>C</i>-methyluridine Nucleotide Prodrug (PSI-7977) for the Treatment of Hepatitis C Virus

TLDR

Hepatitis C virus remains a global health burden, and its NS5B polymerase is a validated therapeutic target. The authors designed phosphoramidate prodrugs of a β‑d‑2′‑deoxy‑2′‑α‑fluoro‑2′‑β‑C‑methyluridine nucleoside that selectively inhibit the NS5B polymerase, with crystallographic analysis revealing an Sp stereochemistry that correlates with activity. These prodrugs exhibited sub‑micromolar potency in HCV subgenomic replicon assays, generated high intracellular triphosphate levels in primary hepatocytes and in vivo in rats, dogs, and monkeys, and the single diastereomer PSI‑7977 was chosen as a clinical development candidate.

Abstract

Hepatitis C virus (HCV) is a global health problem requiring novel approaches for effective treatment of this disease. The HCV NS5B polymerase has been demonstrated to be a viable target for the development of HCV therapies. β-d-2'-Deoxy-2'-α-fluoro-2'-β-C-methyl nucleosides are selective inhibitors of the HCV NS5B polymerase and have demonstrated potent activity in the clinic. Phosphoramidate prodrugs of the 5'-phosphate derivative of the β-d-2'-deoxy-2'-α-fluoro-2'-β-C-methyluridine nucleoside were prepared and showed significant potency in the HCV subgenomic replicon assay (<1 μM) and produced high levels of triphosphate 6 in primary hepatocytes and in the livers of rats, dogs, and monkeys when administered in vivo. The single diastereomer 51 of diastereomeric mixture 14 was crystallized, and an X-ray structure was determined establishing the phosphoramidate stereochemistry as Sp, thus correlating for the first time the stereochemistry of a phosphoramidate prodrug with biological activity. 51 (PSI-7977) was selected as a clinical development candidate.