PSI-6130

PSI-6130 is a selective and effective inhibitor of hepatitis C virus (HCV) RNA replication with an EC50 of 0.46 μM. It is a potent nucleoside analog which incorporates into nascent RNA by the HCV NS5B polymerase and leads to chain termination. [1]
NS5B is a viral protein discovered in hepatitis c virus. It plays a significant role in the replication of HCV, which uses HCV’S viral positive RNA strand as the template and catalyzes the polymerization of rNTP during RNA replication. PSI-6130 is a nucleotide analog and it can be activated by converting into nucleotide triphosphate form, which can be an alternative substrate in the synthesis of viral RNA. As a result PSI-6130 reduces the efficacy of further elongation of HCV RNA by NS5B. [2]
Studies reported PSI-6130 HCV replication inhibition effects. PSI-6130 activity of HCV replication was determined in Huh7 cells with a subgenomic genotype 1b Con1 strain. And the mean IC50 was 0.6 μM. And another study showed that PSI-6130 inhibited HCV GT-1b (Con1 strain) and GT-1a (H77 strain) subgenomic RNA replication, with similar levels of potency, whose mean EC 50 values are 0.51 and 0.30 μM, respectively. [1, 2]
PSI-6130 could be transformed into two active metabolites, RO2433 and PSI-6026 respectively, in human primary hepatocytes by enzymes. Moreover, PSI-6130 showed little or no cytotoxicity  against different cells, including human peripheral blood mononuclear and human bone marrow progenitor cells. [1, 3]
Assessments of PSI-6130’s activity against other viruses in the Flaviviridae family were conducted, which illustrated that PSI-6130 was not active against viruses including BVDV, WNV, YFV, HBV, and HIV. The results also showed that PSI-6130 is a selective HCV inhibitor. [3]
References:
1.Ali S, Leveque V, Le Pogam S, et al. Selected replicon variants with low-level in vitro resistance to the hepatitis C virus NS5B polymerase inhibitor PSI-6130 lack cross-resistance with R1479. Antimicrobial agents and chemotherapy[J], 2008, 52(12): 4356-4369.
2.Ma H, Jiang W R, Robledo N, et al. Characterization of the metabolic activation of hepatitis C virus nucleoside inhibitor β-d-2′-deoxy-2′-fluoro-2′-C-methylcytidine (PSI-6130) and identification of a novel active 5′-triphosphate species[J]. Journal of Biological Chemistry, 2007, 282(41): 29812-29820.
3.Stuyver L J, McBrayer T R, Tharnish P M, et al. Inhibition of hepatitis C replicon RNA synthesis by beta-D-2'-deoxy-2'-fluoro-2'-C-methylcytidine: a specific inhibitor of hepatitis C virus replication[J]. Antiviral chemistry & chemotherapy, 2006, 17(2): 79-87.

Selected replicon variants with low-level in vitro resistance to the hepatitis C virus NS5B polymerase inhibitor PSI-6130 lack cross-resistance with R1479.[Pubmed:18838588]

Antimicrob Agents Chemother. 2008 Dec;52(12):4356-69.

PSI-6130 (beta-D-2'-deoxy-2'-fluoro-2'-C-methylcytidine) is a selective inhibitor of hepatitis C virus (HCV) replication that targets the NS5B polymerase. R7128, the prodrug of PSI-6130, has shown antiviral efficacy in patients chronically infected with HCV genotype 1a (GT-1a) and GT-1b. We observed that the compound exhibited potent in vitro activity against laboratory-optimized HCV replicons as well as against a panel of replicons containing NS5B HCV polymerases derived from GT-1a and GT-1b clinical isolates. We used the HCV replicon cell system to examine the emergence of variants with reduced sensitivity to PSI-6130. Short-term treatment of cells harboring the HCV subgenomic replicon with PSI-6130 cleared the replicon without generating resistant variants. Long-term culture of the cells under the compound selection generated the S282T substitution in a complex pattern with other amino acid substitutions in the NS5B polymerase. The presence of the coselected substitutions did not increase the moderate three- to sixfold loss of sensitivity to PSI-6130 mediated by the S282T substitution; however, their presence enhanced the replication capacity compared to the replication levels seen with the S282T substitution alone. We also observed a lack of cross-resistance between PSI-6130 and R1479 and demonstrated that long-term culture selection with PSI-6130 in replicon cells harboring preexisting mutations resistant to R1479 (S96T/N142T) results in the emergence of the S282T substitution and the reversion of S96T to wild-type serine. In conclusion, PSI-6130 presents a high barrier to resistance selection in vitro, selects for variants exhibiting only low-level resistance, and lacks cross-resistance with R1479, supporting the continued development of the prodrug R7128 as a therapeutic agent for the treatment of HCV infection.

An efficient and diastereoselective synthesis of PSI-6130: a clinically efficacious inhibitor of HCV NS5B polymerase.[Pubmed:19642660]

J Org Chem. 2009 Sep 4;74(17):6819-24.

R7128 is the prodrug of 2'-deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130), a potent and selective inhibitor of HCV NS5B polymerase. Currently, R7128 is in clinical trials for the treatment of HCV infection. To support clinical development efforts, we needed an efficient and scalable synthesis of PSI-6130. We describe an improved, diastereoselective synthetic route starting with protected d-glyceraldehyde. No chiral reagents or catalysts were used to produce the three new contiguous stereocenters. Introduction of fluorine at the C-2 tertiary carbon was accomplished in a highly regio- and stereoselective manner through nucleophilic substitution on a cyclic sulfate. Scale-limiting chromatographic purifications were eliminated through the use of crystalline intermediates.

Characterization of the metabolic activation of hepatitis C virus nucleoside inhibitor beta-D-2'-Deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130) and identification of a novel active 5'-triphosphate species.[Pubmed:17698842]

J Biol Chem. 2007 Oct 12;282(41):29812-20.

beta-D-2'-Deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130) is a potent inhibitor of hepatitis C virus (HCV) replication in the subgenomic HCV replicon system, and its corresponding 5'-triphosphate is a potent inhibitor of the HCV RNA polymerase in vitro. In this study the formation of PSI-6130-triphosphate was characterized in primary human hepatocytes. PSI-6130 and its 5'-phosphorylated derivatives were identified, and the intracellular concentrations were determined. In addition, the deaminated derivative of PSI-6130, beta-d-2'-deoxy-2'-fluoro-2'-C-methyluridine (RO2433, PSI-6026) and its corresponding phosphorylated metabolites were identified in human hepatocytes after incubation with PSI-6130. The formation of the 5'-triphosphate (TP) of PSI-6130 (PSI-6130-TP) and RO2433 (RO2433-TP) increased with time and reached steady state levels at 48 h. The formation of both PSI-6130-TP and RO2433-TP demonstrated a linear relationship with the extracellular concentrations of PSI-6130 up to 100 mum, suggesting a high capacity of human hepatocytes to generate the two triphosphates. The mean half-lives of PSI-6130-TP and RO2433-TP were 4.7 and 38 h, respectively. RO2433-TP also inhibited RNA synthesis by the native HCV replicase isolated from HCV replicon cells and the recombinant HCV polymerase NS5B with potencies comparable with those of PSI-6130-TP. Incorporation of RO2433-5'-monophosphate (MP) into nascent RNA by NS5B led to chain termination similar to that of PSI-6130-MP. These results demonstrate that PSI-6130 is metabolized to two pharmacologically active species in primary human hepatocytes.

A general and enantioselective approach to pentoses: a rapid synthesis of PSI-6130, the nucleoside core of sofosbuvir.[Pubmed:24670208]

J Am Chem Soc. 2014 Apr 23;136(16):5900-3.

An efficient route towards biologically relevant pentose derivatives is described. The de novo synthetic strategy features an enantioselective alpha-oxidation reaction enabled by a chiral amine in conjunction with copper(II) catalysis. A subsequent Mukaiyama aldol coupling allows for the incorporation of a wide array of modular two-carbon fragments. Lactone intermediates accessed via this route provide a useful platform for elaboration, as demonstrated by the preparation of a variety of C-nucleosides and fluorinated pentoses. Finally, this work has facilitated expedient syntheses of pharmaceutically active compounds currently in clinical use.