Monitoring of viral levels during therapy of hepatitis C

Abstract

Alpha interferon therapy of chronic hepatitis C is typically accompanied by a biphasic decrease in hepatitis C virus (HCV) RNA levels: an initial rapid decline during the first 24 to 48 hours, and a second more gradual decline during the following weeks. The rate of second-phase decline correlates with ultimate response to interferon treatment. Thus, assessment of early virological response (EVR) may predict outcome. Data from 2 large clinical trials of peginterferon and ribavirin were combined and analyzed to determine the optimal definition of an EVR which, if not achieved, was associated with a low likelihood of a sustained virological response (SVR he level of hepatitis C virus (HCV) RNA in the blood of patients with chronic hepatitis C T reflects a balance between virus production and clearance. Kinetic studies and mathematical modeling estimate that there is a constant high rate of production of virions in chronic hepatitis C, ranging from 10'' to 10l2 per day. In addition, the half-life of HCV is short, averaging only a few hours.2 This balance of production and clearance is altered with initiation of antiviral therapy. Treatment with alpha interferon results in a decline in HCV RNA levels that can be resolved mathematically into 2 phases. After a latent period of 8 to 10 hours following the injection of interferon, there is an initial rapid decline in HCV RNA levels, the magnitude of which correlates with dose of interferon and viral genotype. The first phase decline is usually measured at 24 or 48 hours and averages 0.9 loglo units (range, 0.3 to 3.0 loglo units).1-6 This first phase decline likely reflects direct inhibition of intracellular HCV production and r e l e a~e .~ The models estimate that interferon's efficacy in inhibiting HCV production in this first phase ranges from about 70% (approximately 0.7 loglo units) for standard interferon given thrice weekly to more than 90% (1 loglo unit) for high daily doses of standard interferon or once weekly peginterfer0n.~,~,7 The addition of ribavirin does not appear to alter first phase kinetics.8 The rate of the first phase decline is approximately 50% greater for genotypes 2 and 3 than for genotype 1 .*,5,7The second phase decline in HCV RNA levels during interferon therapy begins after 24 to 48 hours, and is slower and more variable than the first phase. The second phase decline is felt to reflect continued inhibition of replication and the gradual elimination of virusinfected cell^.'^^ The second phase decay correlates less with interferon dose than the first phase, but is more rapid with peginterferon as compared with standard interferon preparations,7,9 and is considerably more rapid in patients with genotypes 2 and 3 than in those with genotype 1 infection.4.5.7 As observed with the first phase, ribavirin does not appear to influence second phase kinetics. There is marked patient-to-patient variation in second phase decay rates.' S145

Extending combination therapy with peginterferon alfa-2b plus ribavirin for genotype 1 chronic hepatitis C late responders: A report of 9 cases

“…In patients who achieve an early virologic response, the probabilities of achieving an SVR were 80% for those who cleared HCV RNA at week 12 and sooner, and 40% for those who achieved a 2-log reduction in HCV-RNA concentrations but still remained HCV-RNA positive as a recent review of multicenter studies has shown. 5 All of our patients had a 2-log decline but remained HCV-RNA positive at week 12 and, taking into account the previous results, their probabilities of achieving an SVR are lower than those patients who were HCV-RNA negative at week 12. [5][6][7] In this subgroup of patients, with a slower decline in HCV-RNA levels, usually genotype 1 patients with high baseline viral levels, continuing therapy to 72 weeks could be the best way to ensure an SVR with acceptable tolerability and safety.…”

“…5 All of our patients had a 2-log decline but remained HCV-RNA positive at week 12 and, taking into account the previous results, their probabilities of achieving an SVR are lower than those patients who were HCV-RNA negative at week 12. [5][6][7] In this subgroup of patients, with a slower decline in HCV-RNA levels, usually genotype 1 patients with high baseline viral levels, continuing therapy to 72 weeks could be the best way to ensure an SVR with acceptable tolerability and safety.In summary, extending therapy with peginterferon alfa plus ribavirin to 72 weeks for late virologic responders may induce a higher SVR. These results merit further prospective, randomized, controlled studies, using the optimal doses of peginterferon and ribavirin for longer duration versus the current standard 48-week therapy in this subset of patients.…”

“…HCV-RNA determination has an important role not only in the decision to stop therapy but also in better adjusting therapy. 3,[5][6][7] Currently, nonresponders can be detected by a quantitative HCV-RNA test at week 12, showing a decline of less than 2 logs in HCV-RNA concentrations. 3,5 In these patients, combination therapy should be stopped because the probabilities of a sustained response are almost nil.…”

“…3,[5][6][7] Currently, nonresponders can be detected by a quantitative HCV-RNA test at week 12, showing a decline of less than 2 logs in HCV-RNA concentrations. 3,5 In these patients, combination therapy should be stopped because the probabilities of a sustained response are almost nil. In patients who achieve an early virologic response, the probabilities of achieving an SVR were 80% for those who cleared HCV RNA at week 12 and sooner, and 40% for those who achieved a 2-log reduction in HCV-RNA concentrations but still remained HCV-RNA positive as a recent review of multicenter studies has shown.…”

“…5 All of our patients had a 2-log decline but remained HCV-RNA positive at week 12 and, taking into account the previous results, their probabilities of achieving an SVR are lower than those patients who were HCV-RNA negative at week 12. [5][6][7] In this subgroup of patients, with a slower decline in HCV-RNA levels, usually genotype 1 patients with high baseline viral levels, continuing therapy to 72 weeks could be the best way to ensure an SVR with acceptable tolerability and safety.…”