Discovery of 1‑((2<i>R</i>,4a<i>R</i>,6<i>R</i>,7<i>R</i>,7a<i>R</i>)‑2-Isopropoxy-2-oxidodihydro‑4<i>H</i>,6<i>H</i>‑spiro[furo[3,2‑<i>d</i>][1,3,2]dioxaphosphinine-7,2′-oxetan]-6-yl)pyrimidine-2,4(1<i>H</i>,3<i>H</i>)‑dione (JNJ-54257099), a 3′-5′-Cyclic Phosphate Ester Prodrug of 2′-Deoxy-2′-Spirooxetane Uridine Triphosphate Useful for HCV Inhibition

JNJ-54257099 (<b>9</b>) is a novel cyclic phosphate ester derivative that belongs to the class of 2′-deoxy-2′-spirooxetane uridine nucleotide prodrugs which are known as inhibitors of the HCV NS5B RNA-dependent RNA polymerase (RdRp). In the Huh-7 HCV genotype (GT) 1b replicon-containing cell line <b>9</b> is devoid of any anti-HCV activity, an observation attributable to inefficient prodrug metabolism which was found to be CYP3A4-dependent. In contrast, in vitro incubation of <b>9</b> in primary human hepatocytes as well as pharmacokinetic evaluation thereof in different preclinical species reveals the formation of substantial levels of 2′-deoxy-2′-spirooxetane uridine triphosphate (<b>8</b>), a potent inhibitor of the HCV NS5B polymerase. Overall, it was found that <b>9</b> displays a superior profile compared to its phosphoramidate prodrug analogues (e.g., <b>4</b>) described previously. Of particular interest is the in vivo dose dependent reduction of HCV RNA observed in HCV infected (GT1a and GT3a) human hepatocyte chimeric mice after 7 days of oral administration of <b>9</b>

Nucleotide Prodrugs of 2′-Deoxy-2′-spirooxetane Ribonucleosides as Novel Inhibitors of the HCV NS5B Polymerase

The limited efficacy, in particular against the genotype 1 virus, as well as the variety of side effects associated with the current therapy for hepatitis C virus (HCV) infection necessitates more efficacious drugs. We found that phosphoramidate prodrugs of 2′-deoxy-2′-spirooxetane ribonucleosides form a novel class of HCV NS5B RNA-dependent RNA polymerase inhibitors, displaying EC₅₀ values ranging from 0.2 to >98 μM, measured in the Huh7-replicon cell line, with no apparent cytotoxicity (CC₅₀ > 98.4 μM). Confirming recent findings, the 2′-spirooxetane moiety was identified as a novel structural motif in the field of anti-HCV nucleosides. A convenient synthesis was developed that enabled the synthesis of a broad set of nucleotide prodrugs with varying substitution patterns. Extensive formation of the triphosphate metabolite was observed in both rat and human hepatocyte cultures. In addition, after oral dosing of several phosphoramidate derivatives of compound <b>21</b> to rats, substantial hepatic levels of the active triphosphate metabolite were found