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

Abstract

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 21 to rats, substantial hepatic levels of the active triphosphate metabolite were found.

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

“…15,16 They were complemented with the spirocyclic 2'-deoxy-2'-spirocyclopropyl and the 2'-deoxy-2'-spirooxetane moeity. 17,18,19 Recently, the 2'-α-fluoro-2'-β-chloro derivative was also reported 20 ( Figure 1). These 2'-variants not only need to mimic the interaction between the polymerase and the 2'-α-OH group present in natural ribonucleotides, they also must conform to the steric limitations of the corresponding 2'-region of the polymerase to result in proper inhibition thereof.…”

“…22 A few examples of anti-HCV active phosphoramidates are depicted in Figure 2. 18,20,23,24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 The most successful example of this approach is 1, which is the R P diastereomer of a phosphoramidate prodrug of 2'-deoxy-2'α-fluoro-2'-β-C-methyl uridine. The use of 1 was first approved by the FDA for triple therapy in combination with interferon/ribavirin for treatment of HCV patients infected with genotypes 1 and 4, and in combination with ribavirin alone for patients infected with HCV genotypes 2 and 3 in 2013.…”

A Review on Anti-HCV Agents Targeting Active Site and Allosteric Sites of Non-Structural Protein 5b [Ns5b]

“…Jonckers et al identified a series of phosphoramidate prodrugs of 2'-deoxy-2'-spirooxetane ribonucleosides. These prodrugs showed antiviral activity in HCV replicon assay (Huh-7 cells) with an EC50 value ranging from 0.2 to>98 μM, but failed to show potency in cytotoxicity assay [41].…”

Nucleosides and Nucleotides for the Treatment of Viral Diseases

“…63 A unique series of 1 0 -substituted C-nucleosides possessing a 4-aza-7,9dideaza-adenosine base 56 were shown to have modest activity against HCV with improved potency upon preparation of their S-acyl-2-thioethyl prodrugs 57. [67][68][69][70] In the 2 0 -cyclopropyl series, TMC647078 (59) was active in the replicon assay (EC 50 ¼ 7.3 μM) across all GTs, but exhibited reduced activity against NS5B S282T. Preparation of the 2 0 -C-methyl-1 0 -cyano derivatives eliminated the cytotoxicity and subsequent development of the 5 0 -phosphoramidate prodrug of the 1 0 -cyano analog resulted in the clinical candidate GS-6620 58.…”

“…7-Heterocyclic substituted 7-deaza-adenine derivatives containing either the 2 0 -F-2 0 -C-methyl or 2 0 -OH-2 0 -C-methyl substitution (65,66) demonstrated modest HCV replicon potency and modest liver triphosphate levels when administered in vivo to rats. 71 In a similar fashion, an extensive series of 6-substituted-7-heteroaryl-7-deazapurine ribonucleosides (68)(69)(70) were studied, but replicon activity was generally correlated with cytotoxicity. 71 In a similar fashion, an extensive series of 6-substituted-7-heteroaryl-7-deazapurine ribonucleosides (68)(69)(70) were studied, but replicon activity was generally correlated with cytotoxicity.…”