Pegylated interferon plus optimized weight-based ribavirin dosing negate the influence of weight and body mass index on early viral kinetics and sustained virological response in chronic hepatitis C

Hepatitis C virus resistance to interferon therapy: an alarming situation

Hepatitis C virus is presently a major public health problem across the globe. The main objective in treating hepatitis C virus (HCV) infection is to achieve a sustained virological response (SVR). Interferon-α (IFN-α) and pegylated interferon (PegIFN) in combination with Ribavirin (RBV) are the choice of treatment nowadays against chronic hepatitis C. There are several mechanisms evolved by the hepatitis C virus that facilitate the persistence of virus and further lead the patient’s status as non responder. Various factors involved in patient’s lack ofresponse to the therapy include: (1) viral factors, (2) host factors, (3) molecular mechanisms related to the lack of response and (4) social factors. Herein we have made an attempt to summarize all the related predictors of drug resistance in one article so that the future polices can be planned to overcome this obstacle and potential therapies can be designed by considering these factors.

Pegylated interferon fractal pharmacokinetics: individualized dosing for hepatitis C virus infection

Despite recent advances in hepatitis C virus (HCV) therapeutics, the combination of pegylated interferon and ribavirin (PEGIFN/RBV) remains the cornerstone of treatment. Optimization and individualization of PEGIFN dosing could improve outcomes. Week one PEGIFN serum concentrations in 42 HCV genotype 1-infected patients treated with conventional PEGIFN/RBV were analyzed using multicompartmental pharmacokinetic models. For each patient, pharmacokinetic parameter estimates, weight, age, interleukin-28B (IL-28B) single-nucleotide polymorphism, CD4 count, baseline HCV RNA, gender, race, and HIV status were examined using classification and regression tree analysis to identify factors predictive of sustained viral response (SVR). Survival analysis was performed to compare the time to undetectable viral load in patients with and without the highest scoring predictor. PEGIFN concentrations varied at least 87-fold. Pharmacokinetics were best described by a two-compartment model with an 8.4-h absorption lag. Patient weight correlated with PEGIFN systemic clearance based on fractal geometry relationships. SVR was achieved in 36% of patients; a PEGIFN cumulative 1-week area under the curve (AUC) of ≤0.79 mg · h/liter scored highest in predicting poor response, followed by a weight of ≥93.7 kg. Patients with a PEGIFN AUC of >0.79 mg · h/liter achieved undetectable viral load more rapidly than those with a lower AUC (hazard ratio, 1.63; 95% confidence interval, 1.21 to 2.04). PEGIFN exhibits wide pharmacokinetic variability, mainly driven by patient weight, so that the standard dose may not reach levels needed to achieve SVR. Optimizing dose to patient weight and PEGIFN AUC in the first week offers a solution to improve SVR and to potentially shorten duration of therapy.

Impact of obesity on the bioavailability of peginterferon-α2a and ribavirin and treatment outcome for chronic hepatitis C genotype 2 or 3

Background and Aims

Having a body mass index above or equal to 30 kg/m² in conjunction with chronic hepatitis C virus infection is associated with non-responsiveness to treatment with interferon and ribavirin, but details regarding the mechanisms whereby obesity reduces the efficacy of therapy remain unclear.

Methods

This study evaluated impact of obesity on outcome as well as interferon and ribavirin concentrations following standard-of-care fixed dosing with peginterferon-α2a 180 µg once weekly and ribavirin 800 mg daily among 303 HCV genotype 2/3-infected patients enrolled in the per-protocol analysis of a recently completed phase III trial (NORDynamIC).

Results

Patients with BMI ≥30 kg/m² showed poorer outcome following 24 weeks of therapy (SVR 62% vs. 89% for BMI ≥30 vs. <30; P = 0.006) along with significantly higher steatosis grade (P = 0.002), HOMA-IR (P<0.0001), triglyceride levels (P = 0.0002), and baseline viral load (P = 0.028). Obesity was also significantly associated with lower plasma interferon concentrations on days 3, 7, and 29 (P = 0.02, P = 0.0017, and P<0.0001, respectively) and lower plasma ribavirin concentrations day 29 (P = 0.025), and lower concentration of interferon in turn was associated with a poorer first phase reduction in HCV RNA (P<0.0001). In multivariate analysis, ribavirin concentrations week 12, interferon concentrations day 29, and baseline HCV RNA levels were independent predictors of achieving SVR among patients treated for 24 weeks (n = 140).

Conclusions

Reduced bioavailability of interferon and ribavirin along with higher baseline viral load are dominant risk factors for treatment failure in obese patients with chronic hepatitis C.

Prediction of sustained virological response to combination therapy with pegylated interferon alfa and ribavirin in patients with genotype 3 chronic hepatitis C

BACKGROUND

Sustained virological response (SVR) rates in patients with hepatitis C are heterogeneous and are influenced by a wide range of host and viral factors.

AIM

To evaluate the efficacy of combination therapy with pegylated interferon alfa (PEG-IFN-α) and ribavirin (RBV), and document the SVR rates taking into consideration various predictive factors in patients with chronic hepatitis C (CHC) genotype 3.

METHODS

Ninety-seven treatment-naive patients with CHC genotype 3 (mean age 41.46±11.51 years, M:F ratio 79:18), who received a combination of PEG-IFN (α-2a or α-2b) and RBV were retrospectively analyzed (2006-2008) for the early virological response (EVR) at 12 weeks, end of treatment response (ETR), and SVR at 6 months.

RESULTS

Eighty-four (86.6%) patients achieved EVR and 81 (83.5%) achieved ETR, while SVR was achieved in 65 (67.0%) patients. Of the 84 patients who achieved EVR, 77 (91.7%) achieved ETR and 61 (72.6%) achieved SVR at 6 months. Age and body mass index (BMI) were found to be important predictors (*P<0.05) of SVR. CHC patients with a history of alcohol intake showed decreased SVR (52%) (*P=0.035) as compared to nonalcoholics (80%). Cirrhotic versus noncirrhotic patients showed no difference in SVR (54.5% vs. 70.7%) (P=0.157). Serum alanine aminotransferase (ALT) (P=0.169) and hepatitis C virus (HCV) RNA levels (P=0.42) also did not have an influence on the SVR.

CONCLUSION

Combination therapy with PEG-IFN-α and RBV demonstrated good tolerability in CHC genotype 3 infection. Age, BMI, and alcohol consumption play an important role in determining treatment outcome.

Evolution of interferon-based therapy for chronic hepatitis C

Since 1986, interferon-alfa (IFN-α) monotherapy has been administered for patients with chronic hepatitis C (CHC). However, sustained response rate is only about 8% to 9%. Subsequent introduction of ribavirin in combination with IFN-α was a major breakthrough in the treatment of CHC. Sustained virological responses (SVRs) rate is about 30% in hepatitis C virus genotype 1 (HCV-1) patients, and is about 65% in HCV-2 or -3 patients. After 2000, pegylated interferon (PegIFN) much improved the rates of SVR. Presently, PegIFN-α-ribavirin combination therapy has been current standard of care for patients infected with HCV. In patients with HCV-1, treatment for 48 weeks is optimal, but 24 weeks of treatment is sufficient in HCV-2 or -3 infected patients. Clinical factors have been identified as predictors for the efficacy of the IFN-based therapy. The baseline factor most strongly predictive of an SVR is the presence of HCV-2 or -3 infections. Rapid virological response (RVR) is the single best predictor of an SVR to PegIFN-ribavirin therapy. If patients can't achieve a RVR but achieve a complete early virological response (cEVR), treatment with current standard of care can provide more than 90% SVR rate. HCV-1 patients who do not achieve an EVR should discontinue the therapy. Recent advances of protease inhibitor may contribute the development of a novel triple combination therapy.

Superior response to pegylated interferon and ribavirin in Asians with chronic hepatitis C

PURPOSE

Reported sustained virological response (SVR) rates in Asians with chronic hepatitis C (CHC) exceed those of other ethnic groups, but differences in body weight across races potentially confound this observed superior response. Our aim was to determine whether Asian race independently predicts SVR within a multicultural clinic setting.

METHODS

Patients with genotype 1, 2 and 3 CHC prescribed peginterferon and weight-based ribavirin were included in this retrospective study. Logistic regression was performed to identify factors associated with SVR.

RESULTS

Three-hundred ninety-two patients (BMI 26.9 ± 5.0 kg/m(2), genotype 1 66%, viral load 5.9 ± 0.66 log(10) IU/ml, advanced fibrosis 53%) were included in this study. Caucasians comprised 81%, South Asians 9% and Asians (Non-South) 10%. SVR was achieved by 54% overall, but was highest amongst Asians (Non-South) (79%) compared with South Asians (56%, P = 0.04) and Caucasians (50%, P < 0.001) despite a predominance of genotype 3 infection amongst the South Asians. Asians (Non-South) had the highest SVR rate even amongst those infected with genotype 1 (75%) and those with advanced fibrosis (77%). Independent of viral genotype, Asian (Non-South) race was a strong predictor of SVR (OR 5.10 vs. Caucasians, 95% CI 1.72-17.71, OR 7.84 vs. South Asians, 95% CI 1.62-37.84), as were treatment naïve status (OR 3.85, 95% CI 1.76-8.89), non-diabetic status (OR 3.70, 95% CI 1.30-11.11), non-obesity (OR 2.13, 95% CI 1.06-4.35), peginterferon α2a (2.08 vs. α2b, 95% CI 1.16-3.85), steatosis <10% (OR 2.0, 95% CI 1.05-3.85) and ribavirin exposure (mg/kg/day) (OR 1.13, 95% CI 1.01-1.28).

CONCLUSION

Asian (Non-South) race is a strong independent predictor of SVR.