Selected replicon variants with low-level in vitro resistance to the hepatitis C virus NS5B polymerase inhibitor PSI-6130 lack cross-resistance with R1479.
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.
Roche Palo Alto LLC, 3431 Hillview Ave., Palo Alto, CA 94304, USA.
Samir
S
Ali
Vincent
V
Leveque
Sophie
S
Le Pogam
Han
H
Ma
Friederike
F
Philipp
Nicole
N
Inocencio
Mark
M
Smith
Andre
A
Alker
Hyunsoon
H
Kang
Isabel
I
Najera
Klaus
K
Klumpp
Julian
J
Symons
Nick
N
Cammack
Wen-Rong
WR
Jiang
D000998:Antiviral Agents / Q000494:pharmacology; D002460:Cell Line; D003562:Cytidine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D024882:Drug Resistance, Viral / Q000235:genetics*; D014644:Genetic Variation; D016174:Hepacivirus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D012324:RNA-Dependent RNA Polymerase / Q000037:antagonists & inhibitors*; D012093:Replicon / Q000187:drug effects / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017361:Viral Nonstructural Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics
D000998:Antiviral Agents; D017361:Viral Nonstructural Proteins; C504520:2'-deoxy-2'-fluoro-2'-C-methylcytidine; D003841:Deoxycytidine; D003562:Cytidine; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase; C508950:4'-azidocytidine