Individualization of antiviral treatment regimens for chronic hepatitis C

Drug resistance of a viral population and its individual intrahost variants during the first 48 hours of therapy

Using HCV and IFN-resistance as a proof of concept, we have devised a new methodology for calculating the effect of a drug over a viral population and the resistance of its individual intra-host variants.

By means of next-generation sequencing, HCV variants were obtained from sera collected at 9 time-points from 16 patients during the first 48 hours after injection of IFN-α. IFN-resistance coefficients were calculated for individual variants using changes in their relative frequencies, and for the entire intra-host viral population using changes in viral titer during the initial 48 hours.

Population-wide resistance and presence of IFN-resistant variants were highly associated with pegIFN-α2a/RBV treatment outcome at week 12 (p = 3.78×10^-5 and 0.0114, respectively). This new method allows an accurate measurement of resistance based solely on changes in viral titer or the relative frequency of intra-host viral variants during a short observation time.

Clinical trial: individualized treatment duration for hepatitis C virus genotype 1 with peginterferon-alpha 2a plus ribavirin

BACKGROUND

Individualized treatment regimens, taking into account the heterogeneity of patients with chronic hepatitis C, are needed to improve treatment outcomes.

AIM

To investigate prospectively the period of undetectable viraemia required for a high rate of sustained virological response in patients with chronic hepatitis C genotype 1 and the relationship to early viral kinetics.

METHODS

Forty-five chronic hepatitis C genotype 1 patients were given peginterferon-alpha 2a plus ribavirin. Viraemia and hepatocyte HCV-RNA levels were quantified using a TaqMan assay. Beyond the first time point of undetectable viraemia (<20 IU/mL) between baseline and treatment week 12, 32 of 45 (71%) patients were randomized to additional 12 weeks (G12); 24 weeks (G24) or 36 weeks therapy (G36). The remaining 13 patients received 48 weeks' treatment (G48).

RESULTS

The sustained virological response rates were: G12--five of 11 (45%); G2 --eight of 10 (80%); G36--eight of 11 (73%); G48--four of 13 (31%). The anti-viral efficacy (epsilon) and treatment-induced loss of infected hepatocytes (Mdelta), were significantly higher in patients with early viral clearance. In G12, patients with sustained virological response had lower baseline viraemia than those who relapsed.

CONCLUSIONS

Early viraemia clearance is a better marker than baseline viral load and differentiates chronic hepatitis C genotype 1 with high or low probability of sustained virological response. In patients with viraemia clearance within 12 weeks of starting peg-interferon/ribavirin therapy, an additional period of undetectable viraemia of minimum 24 weeks is required for high sustained virological response.

Personalized therapy for chronic viral hepatitis C in the naive patient: How can we optimize treatment duration as a function of viral genotype?

Pegylated interferon plus ribavirin is the standard treatment for chronic hepatitis C (CHC). It yields sustained virological response (SVR) rates of 42-52% for genotype 1, 66-72% for genotype 4, and 76-80% for genotypes 2 and 3. Hence, the patient's genotype appears to be a determining predictive factor for the SVR. We have reviewed the literature in order to determine whether a genotype-specific treatment duration should be envisaged. The largest study to date of patients infected with HCV genotype 2 or 3 confirmed the value of the standard treatment duration of 24 weeks. Shorter treatments exposed the patients to a greater risk of relapse. For genotype 1, it was possible to offer a shorter, 24-week course of treatment to the 35% of patients with an initial viral load below 600,000 IU/mL and an early virological response (EVR) at week 4 (negative PCR), resulting in an SVR of 89%. For the remaining two-thirds of genotype 1 patients with a high viral load, the treatment duration should remain at 48 weeks. A subgroup of patients - the "slow virological responders" (positive PCR at week 12 but with less than 6000 IU/mL; negative PCR at week 24) - benefited from the extension of the treatment to 72 weeks, with an SVR of 88%. For patients infected with genotype 4 virus, combination therapy should feature a ribavirin dose of more than 1000 mg/day for an optimal duration of 48 weeks.