FDA Hepatitis Update - Vicrelis (boceprevir) label changes

On February 27, 2013, FDA approved changes to the Victrelis (boceprevir) label to include results from a clinical trial entitled, “Bcoeprevir and Peginterferon/Ribavirin for the Treatment of Chronic Hepatitis C in Treatment-Naïve Subjects: A Comparison of Erythropoietin Use Versus Ribavirin Dose Reduction for the Management of Anemia.” In addition the Microbiology-Resistance section was updated with new information about the impact of specific amino acid substitutions on HCV replicon susceptibility to boceprevir. The changes are summarized below.
Section 5: Warnings and Precautions
5.2  Anemia (Use with Ribavirin and Peginterferon Alfa)
In clinical trials, the median time to onset of hemoglobin less than 10 g per dL from the initiation of therapy was similar among subjects treated with the combination of VICTRELIS and PegIntron/REBETOL (71 days with a range of 15-337 days), compared to those who received PegIntron/REBETOL (71 days with a range of 8-337 days).
A randomized, parallel-arm, open-label clinical trial was conducted in previously untreated CHC subjects with genotype 1 infection to compare use of an ESA versus ribavirin dose reduction for initial management of anemia during therapy with VICTRELIS in combination with peginterferon alfa-2b and ribavirin. Similar SVR rates were reported in subjects who were randomized to receive ribavirin dose reduction compared to subjects who were randomized to receive an ESA. In this trial, use of ESAs was associated with an increased risk of thromboembolic events including pulmonary embolism, acute myocardial infarction, cerebrovascular accident, and deep vein thrombosis compared to ribavirin dose reduction alone. The treatment discontinuation rate due to anemia was similar in subjects randomized to receive ribavirin dose reduction compared to subjects randomized to receive ESA (2% in each group). The transfusion rate was 4% in subjects randomized to receive ribavirin dose reduction and 2% in subjects randomized to receive ESA.
Ribavirin dose reduction is recommended for the initial management of anemia.
Section 14: Clinical Studies
Use of Ribavirin Dose Reduction versus Erythropoiesis Stimulating Agent (ESA) in the Management of Anemia in Previously Untreated Subjects
A randomized, parallel-arm, open-label study was conducted to compare two strategies for the management of anemia (use of ESA versus ribavirin dose reduction) in 687 subjects with previously untreated CHC genotype 1 infection who became anemic during therapy with VICTRELIS 800 mg orally three times daily plus peginterferon alfa-2b 1.5 micrograms per kg per week subcutaneously and weight-based ribavirin (600  1,400 mg per day orally divided twice daily). The study enrolled subjects with serum hemoglobin concentrations of less than 15 g per dL. Subjects were treated for 4 weeks with peginterferon alfa-2b and ribavirin followed by up to 44 weeks of VICTRELIS plus peginterferon alfa-2b and ribavirin. If a subject became anemic (serum hemoglobin of approximately less than or equal to 10 g per dL within the treatment period), the subject was randomized in a 1:1 ratio to either ribavirin dose reduction (N=249) or use of erythropoietin 40,000 units subcutaneously once weekly for the management of the anemia (N=251). If serum hemoglobin concentrations continued to decrease to less than or equal to 8.5 g per dL, subjects could be treated with additional anemia interventions, including the addition of erythropoietin (18% of those in the ribavirin dose reduction arm) or ribavirin dose reduction (37% of those in the ESA arm).
Mean age of subjects randomized was 49 years. The racial distribution of subjects was as follows: 77% White, 19% Black, and 4% other. The distribution of subjects by gender was 37% men and 63% women.
The overall intent-to-treat SVR rate for all enrolled subjects (including those subjects who were not randomized to RBV dose reduction or ESA for the management of anemia) was 63% (431/687). The SVR rate in subjects randomized who received ribavirin dose reduction was 71% (178/249), similar to the SVR rate of 71% (178/251) in subjects randomized to receive an ESA. The relapse rates in subjects randomized to receive ribavirin dose reduction or an ESA were 10% (19/196) and 10% (19/197), respectively.
Section 12.4 Microbiology
In HCV Replicon Cell Culture and Biochemical Studies
The activity of boceprevir against the HCV genotype 1a replicon was reduced (2- to 6-fold) by the following amino acid substitutions in the NS3 protease domain: V36A/L/M, Q41R, T54A/S, V55A, R155K and V158I. A greater than 10-fold reduction in boceprevir susceptibility was conferred by the amino acid substitutions TR155T and A156S. The V55I and D168N single substitutions did not reduce sensitivity to boceprevir. The following double amino acid substitutions conferred more than 10-fold reduced sensitivity to boceprevir: V55A+I170V, T54S+R155K, R155K+D168N, R155T+D168N and V36M+R155K.
The activity of boceprevir against the HCV genotype 1b replicon was reduced (2- to 8- fold) by the following amino acid substitutions in the NS3 protease domain: V36A/M, Q41R, F43S, T54A/G/S, V55A/I, R155K, V158I, V170M and M175L. A greater than 10-fold reduction in boceprevir susceptibility was conferred by the amino acid substitutions A156S/T/V, V170A and V36M+R155K. The D168V single substitution did not reduce sensitivity to boceprevir.
Additional NS3 protease domain substitutions that have not been evaluated in the HCV replicon but have been shown to reduce boceprevir activity against the HCV NS3/4A protease in a biochemical assay include F43C and R155G/I/M/Q
Resistance-associated amino acid substitutions for HCV genotype 1a and 1b observed in clinical trials are presented in Table 8.
You can view the entire revised label at Drugs@FDA.
Victrelis is a product of Merck & Co.
Richard Klein
Office of Special Health Issues
Food and Drug Administration
Kimberly Struble
Division of Antiviral Drug Products
Food and Drug Administration
Steve Morin
Office of Special Health Issues
Food and Drug Administration