Hepatitis C genotype 1 virus with low viral load and rapid virologic response to peginterferon/ribavirin obviates a protease inhibitor

Authors

  • Brian L. Pearlman,

    Corresponding author
    1. Center for Hepatitis C, Atlanta Medical Center, Atlanta, GA
    2. Department of Graduate Medical Education, Atlanta Medical Center, Atlanta, GA
    3. Medical College of Georgia, Department of Medicine, Augusta, GA
    4. Emory University School of Medicine, Department of Medicine, Atlanta, GA
    • Address reprint requests to: Brian L. Pearlman, M.D., FACP, Center for Hepatitis C, Atlanta Medical Center, 285 Boulevard NE, Suite 525, Atlanta, GA 30312. E-mail: brianpearlman@hotmail.com; fax: 404-872-4061.

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  • Carole Ehleben

    1. Department of Graduate Medical Education, Atlanta Medical Center, Atlanta, GA
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  • Potential conflict of interest: Dr. Pearlman consults, advises, and is on the speakers' bureau for Merck; C.E. has no conflicts of interest.

Abstract

The new standard of care for treatment-naïve patients with hepatitis C virus (HCV) genotype 1 includes triple therapy with peginterferon, ribavirin, and a protease inhibitor. However, patients who achieve a rapid virologic response after 4 weeks of peginterferon and ribavirin therapy are likely to achieve a sustained virologic response (SVR), and we hypothesized that protease inhibitor therapy may be unnecessary in these patients. Treatment-naïve, noncirrhosis patients infected with genotype-1 HCV and a low viral load at baseline were considered for inclusion (n = 233). After 4 weeks of lead-in therapy with peginterferon α-2b and ribavirin, 101 patients (48%) had a rapid virologic response (defined as undetectable levels of hepatitis C virus RNA at 4 weeks) and were eligible to participate. Patients were randomized 1:1 to 20 weeks of additional therapy with peginterferon α-2b and ribavirin (double therapy) or to 24 weeks of peginterferon α-2b, ribavirin, and boceprevir (triple therapy). There was no significant difference in rates of SVR-12 in patients treated with double versus triple therapy. This similarity persisted regardless of viral subtype (genotype 1a or 1b), interleukin (IL)−28b genotype (CC or non-CC), or ethnicity (African American versus non-Hispanic white). Conclusion: Protease inhibitor therapy could be obviated in genotype 1-infected treatment-naïve patients with low viral load at baseline who achieve undetectable viremia after 4 weeks of peginterferon/ribavirin.(Hepatology 2014;58:71–77)

Abbreviations
EMA

European Medicines Agency

ETR

end of treatment response

HCV

hepatitis C virus

LVL

low viral load

PEG

pegylated-interferon

RBV

ribavirin

RVR

rapid virologic response

SVR

sustained virologic response.

Over 185 million people are chronically infected with the hepatitis C virus (HCV),[1] and more than 350,000 people die each year from hepatitis C-related liver diseases.[2] The therapy for chronic hepatitis C infection has historically been pegylated-interferon (PEG) plus ribavirin (RBV). This treatment can effect a sustained virologic response (SVR),[3, 4] which is associated with long-term clearance of HCV infection, a virologic cure.[5-8]

Viral load is a major determining factor in responsiveness to PEG/RBV, and a viral load of <800,000 IU/mL is considered low. More recent data suggest that the optimized threshold for serum HCV RNA to predict therapy outcome is 400,000 IU/mL.[9] Up to half of patients with genotype 1 HCV with low viral load (LVL) achieve a rapid virologic response (RVR),[10] defined as undetectable levels of HCV RNA after 4 weeks of treatment with PEG/RBV. RVR is used as a tool to predict outcomes and individualize therapy according to treatment-related viral kinetics,[11] and patients who achieve RVR are more likely to have an SVR.[12] Not only is LVL associated with achievement of RVR and better response to treatment, but in one study it was associated with better long-term outcomes.[13] Approximately 15%-20% of all genotype 1 HCV-infected patients have LVL.[14]

A multitude of studies have demonstrated that genotype 1-infected treatment-naïve patients with LVL at baseline who achieve RVR can be treated with 24 weeks of PEG/RBV therapy without compromising SVR rates.[10, 15-21] Based on one of these trials, the European Medicines Agency (EMA) has approved the use of 24 weeks of PEG/RBV in genotype 1-infected patients with low baseline viral loads (<600,000 IU/mL) who achieve RVR.[10]

However, a new era of hepatitis C therapy began in 2011, when protease inhibitors to the viral NS3-NS4a protease enzyme improved the SVR rate for genotype 1 HCV infection (specifically, boceprevir[22, 23] and telaprevir[24, 25]). The new standard of care for HCV genotype 1-infected patients is triple therapy: PEG/RBV plus a protease inhibitor.[26] Currently, treatment-naïve, noncirrhosis patients who, after a 4-week lead-in with PEG/RBV, achieve undetectable serum virus at 8 and 24 weeks with triple therapy that includes boceprevir, are treated for a total of 28 weeks.[27]

Yet these therapies come with a cost. Protease inhibitors for HCV infection have incremental side effects above those of PEG/RBV alone: high costs, substantial pill burden, the potential for resistance, and many drug-drug interactions.[27-29]

Given these drawbacks, should a protease inhibitor, such as boceprevir, be given to all patients with genotype 1 infection? We hypothesized that protease inhibitor therapy could be obviated in patients who responded well to PEG/RBV treatment. Specifically, we considered therapy-naïve patients with HCV genotype-1, LVL (<600,000 IU/mL), who achieved RVR.

Patients and Methods

Patients

Patients were considered for inclusion in the study if they were treatment-naïve, infected with genotype-1 HCV, and had LVL at baseline (<600,000 IU/mL). Patients were 18 years of age or older and had a liver biopsy in the past 2 years consistent with chronic hepatitis. Cirrhosis patients were excluded. Before randomization, patients had been rapid virologic responders to 4 weeks of peginterferon α-2b (1.5 μg/kg/wk; PegIntron; Merck Whitehouse Station, NJ) and ribavirin (1-1.2 g/day based on weight: 1,000 mg/day for <75 kg or 1,200 mg/day for ≥75 kg). A rapid virologic responder was defined as undetectable HCV RNA using polymerase chain reaction (Taqman, Roche; detection limit 10 IU/mL). All testing was performed at a single reference laboratory.

Pretreatment exclusion criteria included the following: HCV/human immunodeficiency virus coinfection; HCV genotype other than 1; biopsy-proven or strongly suspected clinical cirrhosis; other causes of liver disease, including coinfection with hepatitis B; creatinine clearance <50 mL/min (modification of diet in renal disease equation); platelet count <80 × 109/L; neutrophil count <1.5 × 109/L; hemoglobin concentration <13 g/dL and 12 g/dL in men and women, respectively; coexisting uncontrolled psychiatric or cardiopulmonary disorders; hemoglobinopathy; sarcoidosis; malignant neoplasm; receipt of immunosuppressive or immunomodulatory therapy in the previous 6 months; pregnancy; and men whose partners were pregnant or unwilling to use contraception during the study period. Female patients of childbearing age also agreed to avoid systemic contraception if ultimately randomized into the protease inhibitor-containing arm. Patients were also excluded if they imbibed significant amounts of alcohol (>30 g/day), or if they were active substance abusers in the past 6 months.

Patient characteristics recorded at baseline included age, sex, body mass index, fasting glucose, 25-hydroxy vitamin D levels, ethnicity, histological results of pretreatment liver biopsy (Metavir scoring: F0, no fibrosis; F1, portal fibrosis; F2, few septa; F3, many septa without cirrhosis; F4, cirrhosis which were excluded), and quantitative HCV viral load (recorded as IU/mL at baseline, week 4 [randomization], weeks 8, 12, 24, end-of-therapy and at 12 weeks posttreatment). Patients were stratified by genotype subtype (1a versus 1b) and by interleukin (IL)−28B genotype (rs12979860). Patients were genotyped using the Illumina Human610-quad BeadChip (San Diego, CA) as described.[30]

The study was investigator-initiated. The protocol was approved by Atlanta Medical Center's Institutional Review Board. The trial adhered to the ethical principles outlined in the World Medical Association Declaration of Helsinki. Patients were recruited from Atlanta Medical Center's Center for Hepatitis C and Sheffield Health Center, both ambulatory clinics, in downtown Atlanta, Georgia. Merck, the manufacturer of peginterferon-α2b, had no direct or indirect involvement in the study design, data collection, or preparation of the article.

Treatment and Monitoring

Rapid virologic responders to PEG/RBV were randomly assigned in open-label fashion to a 1:1 ratio to continue for an additional 24 weeks of PEG/RBV/BOC (boceprevir 800 mg tid) (Group A) or to continue with an additional 20 weeks of PEG/RBV only (Group B). Therapy dosing was not changed prerandomization and postrandomization; patients received full dose of medication unless the dose had been reduced for cytopenias during therapy. Boceprevir was never dose reduced, however. Growth factors of any variety were prohibited.

All patients who were randomized and those who received at least one dose of study medication were included in the intention-to-treat population. All patients who received at least one dose of study medication and had at least one postbaseline safety assessment were included in the safety analysis.

Patients were monitored at baseline and at monthly intervals by way of physical examination, patient weight, Beck's Depression Inventory, complete blood count and differential, hepatic profile, thyroid-stimulating hormone, electrolytes, serum creatinine, serum uric acid, and serum beta-human chorionic gonadotropin testing, if applicable.

Dose reductions for anemia were at investigators' discretion using 200-400 mg ribavirin decrements in dose. For interferon-related neutropenia, dose reductions and treatment discontinuations were made only for absolute neutrophil counts under 0.5 × 109 and 0.25 × 109, respectively, and only at the investigators' discretion. An end-of-treatment response was checked by way of serum RNA analysis at week 28 (Group A) and at week 24 (Group B), and again to assess SVR-12 after therapy cessation. SVR-12 was the primary endpoint; the relapse rate was the secondary endpoint.

Statistical Analysis

Only randomized patients were included in the treatment analysis. Physicians enrolled participants and obtained informed consent to participate. Randomizations were concealed until after patients consented to participate and interventions were assigned. Data were collected by a research nurse not involved in the patient's treatment. Patient baseline characteristics were compared using chi-squared tests and all outcome and subgroup analysis were performed using the same chi-squared tests and applying the Yates correction factor for cell size <10. Because population power estimates and expected frequencies were not specified beforehand, only nonparametric statistics were possible.

The study was designed to randomize 100 patients to triple or double therapy; thus, after 100 patients were assigned to treatment, enrollment ceased. Except for an abstract submission in July 2012, at which time data were analyzed from patients who had finished treatment to date, outcome data were reviewed after the entire group of randomized patients had completed therapy. We chose to enroll 100 patients, believing that this number would be an adequate and representative sample of differences in triple versus double therapy in patients with LVL who achieve RVR; the number was not generated from a formal sample size calculation.

Results

Patient Profiles

Patients were recruited between July 2011 and May 2012 from two separate ambulatory clinics at Atlanta Medical Center: the Center for Hepatitis C and the Sheffield Health Center.

The trial participant flow is shown in Fig. 1. Of the 233 patients treated with the 4-week lead-in therapy, 112 had RVR (48%). Eleven subjects were ineligible or declined to participate, leaving 101 patients who were randomized to either triple (n = 49) or to double therapy (n = 52).

Baseline characteristics were statistically similar in both treatment groups and are shown in Table 1. The mean age was 54 for the triple therapy group and 52 for the double therapy group. The baseline 25-hydroxy D levels were not statistically different between data arms (data not shown).

Figure 1.

Study Participant Flow. G-1, genotype 1; LVL, low viral load; RVR, rapid virologic response; SVR, sustained virologic response; PEG, pegylated-interferon; RBV, ribavirin; BOC, boceprevir.

Table 1. Baseline Characteristics
 Group A (Triple Therapy) n = 49Group B (Double Therapy) n = 52
  1. There were no significant differences between the groups.

Mean age (yrs)5452
Male subjects (%)6163
BMI (mean)2829
Impaired fasting glucose (%)1215
African American subjects (%)3737
F3 fibrosis (%)2018
Genotype 1a (%)3938
Genotype 1b (%)6162
IL-28 CC (%)6566
IL-28 non-CC (%)3434

Patients were then randomized 1:1 to 20 weeks of additional therapy with PEG/RBV or 24 weeks of PEG/RBV plus boceprevir (800 mg tid). All patients received follow-up at 12 weeks to determine SVR rates. In both groups, 46 patients completed follow-up.

Side Effects

Side effects were not statistically different between treatment arms. In addition, there were no significant differences between groups treated with triple or double therapy with respect to medication dose reductions (triple = 33%, double = 33%; P = ns). Nor were there differences between the groups with respect to medication discontinuations (triple = 6%, double = 8%; P = ns) (Fig. 1).

Viral Response

There were no significant differences in the primary endpoint, SVR-12 rates (44/49 [90%] patients in Group A versus 46/52 [88%] patients in Group B). Likewise, end-of-treatment response rates (46/49 [94%] patients versus 49/52 [94%] patients) and relapse rates (4% patients versus 6% of patients), were not statistically different between Groups A or B (Fig. 2). SVR-24 rates were identical with SVR-12 rates (90% for Group A and 88% for Group B).

Figure 2.

Overall virologic response rates. ETR, relapse, and SVR-12 rates in patients treated with triple (PEG/RBV/BOC, n = 49) or double (PEG/RBV, n = 52) therapy were not significantly different. ETR, end-of-treatment response rate; SVR, sustained virologic response; PEG, pegylated-interferon; RBV, ribavirin; BOC, boceprevir.

In subgroup analysis, the P value was not significantly different for SVR-12 rates between Groups A and B with respect to the following comparisons: IL-28 B subtype (CC versus non-CC) (Fig. 3), HCV subtype (genotype 1a versus 1b) (Fig. 4), and among African Americans (Fig. 5).

Figure 3.

IL-28B genotype analysis (rs12979860). SVR-12 rates were similar in patients treated with triple (PEG/RBV/BOC) or double (PEG/RBV) therapy regardless of IL-28B genotype status. SVR, sustained virologic response; PEG, pegylated-interferon; RBV, ribavirin; BOC, boceprevir.

Figure 4.

HCV genotype 1 subtype analysis. SVR-12 rates were similar between patients treated with triple (PEG/RBV/BOC) or double (PEG/RBV) therapy regardless of HCV subtype (genotype 1a versus 1b). SVR, sustained virologic response; PEG, pegylated-interferon; RBV, ribavirin; BOC, boceprevir; HCV, hepatitis C virus.

Figure 5.

SVR rates for African-Americans treated with triple or double therapy. Among African-Americans, SVR-12 rates were similar in patients treated with triple (PEG/RBV/BOC) or double (PEG/ RBV) therapy. SVR, sustained virologic response; PEG, pegylated-interferon; RBV, ribavirin; BOC, boceprevir.

Furthermore, there was no statistical difference among pretreatment HCV RNA values when analyzed for <400,000 IU/mL or <600,000 IU/mL, although the numbers in each subgroup were small, and there was no difference between F3 patients' SVR rates, regardless of assigned therapy arm (data not shown). Also not shown was that IL-28B CC was a predictor of patients achieving RVR in the original group (n = 233).

Discussion

In treatment-naïve patients with HCV genotype-1 infection with LVL at baseline who achieved RVR with 4 weeks of PEG/RBV therapy, there was no significant difference in rates of end-of-treatment response (ETR), relapse or in SVR in patients treated with double versus triple therapy (double included 24 weeks of therapy total PEG/RBV, and triple included the addition of boceprevir at week 5, for 28 weeks of therapy total). This similarity persisted regardless of viral subtype (genotype 1a or 1b), IL-28b genotype status (CC or non-CC), or ethnicity (African American versus non-Hispanic white). Safety and tolerability were similar in protease inhibitor-containing and protease inhibitor-sparing regimens.

We chose to compare 24 to 28 weeks of therapy, since the former is the EMA-approved duration for peginterferon α-2b/ribavirin treatment in genotype 1-infected patients with baseline LVL who achieve RVR, and the latter is the standard duration for boceprevir-containing regimens in treatment-naïve, noncirrhosis patients who are early virologic responders. We excluded patients with cirrhosis, since these patients cannot qualify for response-guided therapy because of increased rates of relapse with shorter therapy regimens.

Ninety percent of patients in the triple therapy arm (Group A) achieved SVR-12 (and SVR-24), which corresponds to the SVR-24 rates in boceprevir-treated patients who achieved undetectable viremia at week 8 in the SPRINT-2 trial.[23] Likewise, 88% of patients who received double therapy (Group B) achieved SVR-12 (and SVR-24), which is comparable to 81%-89% SVR-24 rates in genotype 1-infected patients who had achieved RVR with 24 weeks of PEG/RBV in previously published studies.[15, 17]

Because genotype 1b virus needs two nucleotide substitutions in its protease enzyme to confer resistance to a first-generation protease inhibitor like boceprevir (i.e., higher barrier to resistance than genotype 1a virus that needs merely one substitution), SVR rates are higher against the former viral subtype with triple therapy.[31, 32] Yet dual therapy (PEG/RBV) has been shown to be more effective against HCV subtype 1a than 1b.[33] Thus, HCV subtyping may play a role in selecting future treatment options and predicting the development of resistance.[26, 34] However, in our study in patients with LVL who achieved RVR, we found no difference in SVR rates between genotype 1a and 1b in groups treated with double or triple therapy.

Polymorphisms in the region of the IL-28B gene on chromosome 19 have been associated with SVR and viral clearance. Patients with the CC genotype (rs12979860) are more likely to achieve SVR than are patients with the non-CC (CT or TT) genotype.[30, 35] In fact, in interferon-based therapy without direct acting antiviral agents, the IL-28B polymorphism is the strongest pretreatment predictor of SVR in genotype 1 infection.[36] Even with triple therapy containing a protease inhibitor, IL-28B polymorphisms can affect SVR rates.[37] However, among our therapy-naïve HCV genotype 1-infected patients with LVL and RVR, we did not see a difference in SVR rates between CC and non-CC for patients treated with double or triple therapy.

African American patients have traditionally responded less well to PEG/RBV therapy, and this difference has been attributed, in part, to a decreased prevalence of the IL-28B gene in this population.[30] African Americans also respond less well to triple therapy relative to non-African Americans.[23] The SVR in African Americans in this trial (37% of total randomized subjects) were statistically equal regardless of the use of a protease inhibitor. The SVR rates (82%-84%) in this subgroup appear very high, but this can be attributed to the fact that all of these patients had a low baseline viral load and achieved RVR.

Baseline patient ethnicity, viral subtype, and IL-28B genotype did not seem to impact SVR rates ultimately, regardless of therapy used. This amplifies the point that on-treatment predictors of therapy success trump pretreatment predictors.

However, this analysis was limited to patients with baseline LVL. It is unclear if a protease inhibitor could be obviated in patients with high baseline viral load who likewise achieve RVR without a randomized trial; however, patients achieving RVR have similar rates of SVR in those treated with a regimen containing a protease inhibitor compared to dual therapy with PEG/RBV alone.[23, 24, 31]

This was a single-center, dual-clinic analysis with relatively small numbers. No formal statistical hypothesis testing was performed; thus, sample size per treatment group was not derived to control the probability of type 1 error or to provide sufficient statistical power. Treatment randomizations were revealed after patients consented to participate and interventions were assigned, so the study was not placebo-controlled. Finally, these results may not be generalizable to the other therapies commonly used to treat HCV. For example, we did not use peginterferon α-2a or the protease inhibitor telaprevir.

Protease inhibitors are costly,[29] and are not yet available in many countries that lack the monetary resources to cover them. If this protease inhibitor-sparing strategy were implemented in countries that can currently afford them, a significant cost-savings could potentially be achieved even if this strategy were limited to those genotype 1-infected patients with baseline LVL who achieve RVR. The issue of cost-effectiveness of individualizing therapy according to RVR has already been demonstrated. Compared to the universal treatment of all genotype 1-infected patients with a protease inhibitor, the protease inhibitor-sparing regimens in those patients achieving RVR were among the most cost-effective strategies studied.[38] The results of this current analysis confirm that there is no virologic advantage of adding a protease inhibitor to PEG/RBV therapy in patients with RVR, at least in those with LVL at baseline.

In conclusion, in treatment-naïve, noncirrhosis, chronically infected HCV genotype 1-infected patients who have low baseline viral load and achieve RVR, adding a protease inhibitor may offer no benefit in terms of therapy duration or efficacy. These results hold true irrespective of patient's viral subtype, IL-28B genotype, or ethnicity (African American versus non-Hispanic white).

Acknowledgment

We thank Nomi Traub, Louis Lovett, Daniel Frilingos, and Tanna Lim for their invaluable help with the trial. We also thank the residents and staff of Atlanta Medical Center's Center for Hepatitis C and those of Sheffield Health Center. We thank Karen Staman for assistance in drafting and editing the article.

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