The advent of direct-acting antiviral agents that target different steps of the hepatitis C virus (HCV) lifecycle is expected to revolutionize hepatitis C treatment. Current standard therapy -- pegylated interferon plus ribavirin -- works by stimulating the immune response rather than targeting the virus directly.

The approval of Merck's boceprevir comes just 2 weeks after its unanimous recommendation by the Food and Drug Administration's Antiviral Drugs Advisory Committee.

Boceprevir, in combination with pegylated interferon plus ribavirin, produced higher sustained virological response (SVR) rates than standard therapy alone in the pivotal SPRINT-2 and RESPOND-2 studies. The improvement was particularly notable for people with HCV genotype 1 and those who did not respond or relapsed with a prior course of standard treatment.

The likelihood of SVR for genotype 1 prior non-responders was around 60% with boceprevir plus pegylated interferon/ribavirin compared to about 20% with standard therapy alone. For treatment-naive patients, cure rates approached 70% with boceprevir combination therapy versus about 40% with standard treatment alone. People who achieve SVR -- generally considered a cure -- reduce their risk of developing liver cirrhosis and hepatocellular carcinoma.

Studies have shown that boceprevir is generally well-tolerated, but it increases the risk of developing anemia; some recipients also reported neutropenia (low neutrophil levels) and unusual taste sensations.

Boceprevir was approved for adults with HCV genotype 1 and compensated liver disease. It is indicated for both treatment-naive patients and prior non-responders or relapsers.

The standard dose of boceprevir is 800 mg 3-times-daily with food. Patients should take pegylated interferon/ribavirin for a 4-week lead-in period before starting boceprevir, then continue on all 3 drugs.

Most people can use response-guided therapy -- adjusting duration of therapy based on response at weeks 8, 12, and 24 -- but the maximum 48-week duration is recommended for some hard-to-treat patients. Discontinuation due to likely treatment futility is recommended for patients who still have HCV viral load of at least 100 IU/mL at week 12 or detectable HCV RNA at week 24.

"This is an exciting day for physicians and patients because Victrelis is the first major advancement for the treatment of chronic hepatitis C approved in a decade," said clinical investigator Bruce Bacon from Saint Louis University School of Medicine in a Merck press release. "Compared to current standard therapy, Victrelis can significantly increase a patient's chance of achieving undetectable levels of the virus, thereby obtaining an SVR. For many patients, Victrelis may allow for a shorter total duration of treatment."

Merck has said that it will begin shipping boceprevir to pharmacies within a week. The company also indicated that it is expanding its support of public awareness and patient education efforts, as well as a patient assistance program to help eligible patients obtain access to the new drug.

"Victrelis is an important new advance for patients with hepatitis C," said Edward Cox, director of the Office of Antimicrobial Products in FDA's Center for Drug Evaluation and Research. "This new medication provides an effective treatment for a serious disease, and offers a greater chance of cure for some patients' hepatitis C infection compared to currently available therapy."

The FDA is also expected to soon approve another HCV protease inhibitor, Vertex's telaprevir (Incivek), which also received unanimous approval from the Antiviral Drugs Advisory Committee the day after boceprevir in late April.

Merck's press release, including findings from the Phase 3 trials and important safety information, is available online at http://www.merck.com/newsroom/news-release-archive/prescription-medicine-news/2011_0513.html.

Full Victrelis Prescribing Information is available at http://www.merck.com/product/usa/pi_circulars/v/victrelis/victrelis_pi.pdf.

The Victrelis Medication Guide is available at http://www.merck.com/product/usa/pi_circulars/v/victrelis/victrelis_mg.pdf.

Victrelis label information is also available from the FDA at http://www.accessdata.fda.gov/drugsatfda_docs/label/2011/202258lbl.pdf.

5/17/11

Sources

U.S. Food and Drug Administration. FDA Approves Victrelis for Hepatitis C. Press release. May 13, 2011.

R Klein and K Struble (FDA). Approval of Victrelis (boceprevir) a direct acting antiviral drug to treat hepatitis C virus (HCV). FDA Hepatitis Update. May 13, 2011.

Merck. FDA Approves Merck's Victrelis (boceprevir), First-in-Class Oral Hepatitis C Virus (HCV) Protease Inhibitor. Press release. May 13, 2011.

Merck. Merck Announces Hope Against Hepatitis C Initiative to Support Public Awareness, Education and Research in the Fight Against Hepatitis C Virus. Press release. May 9, 2011.