William F. Balistreri, MD
Is it true that we are close to treatment of patients with chronic hepatitis C virus (HCV) infection with an interferon-free regimen?
Response from William F. Balistreri, MD
Professor of Medicine, University of Cincinnati College of Medicine; Staff Physician, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
A New Era of Therapy
Combination therapy with pegylated interferon (PEG-IFN) and ribavirin long stood as the standard of care for chronic hepatitis C virus (HCV) infection. Although effective in achieving high rates of sustained virologic response (SVR), this combination regimen was associated with troublesome side effects. Therefore, the development of 2 effective protease inhibitors -- telaprevir and boceprevir -- was hailed as a new era of therapy for patients with HCV genotype 1 infection. These direct-acting antiviral agents act at specific steps in the viral lifecycle and allow more effective treatment with a shorter duration.
Telaprevir and boceprevir, linear inhibitors of the HCV nonstructural protein 3/4A (NS3/4A) serine protease, were approved by the US Food and Drug Administration for HCV treatment in May 2011. However, the recent American Association for the Study of Liver Diseases (AASLD) recommendations indicate that these direct-acting antiviral agents must be used in combination with PEG-IFN and ribavirin. This is far from the ideal regimen; because of poor tolerability, many treatment candidates will decide not to pursue treatment or to defer treatment until an IFN-free regimen is available.
An Ideal Strategy for HCV
It is true that an IFN-free regimen is "no longer a dream." It is now viewed as part of a larger goal: the development and validation of an ideal strategy to treat HCV infection. The long sought-after therapeutic objective is to define a strategy that would be highly effective against allHCV genotypes, simple (oral drugs only, low pill burden, and short duration), and safe and tolerable, with low rates of resistance emergence. The recommended strategy would also assess each potential treatment candidate for interleukin 28B genotype, which is a robust pretreatment predictor of SVR to therapy in patients with genotype 1 chronic HCV infection.
How close are we? Various compounds, encompassing at least 5 distinct drug classes, are currently under development for the treatment of chronic HCV infection, and the results of trials of several investigational agents were recently published.[3-5] Many other drug trials were presented at The Liver Meeting 2011: The AASLD 62nd Annual Meeting. These drugs bring us one step closer to the long sought-after ideal: the ability to delete noisome IFN injections from treatment strategies.
Promising Preliminary Results
Let me illustrate by focusing on phase 2 studies presented by 2 groups who reported exciting preliminary results of an investigational agent (PSI-7977) even in the absence of IFN coadministration.[6,7] PSI-7977, a uridine nucleotide analog polymerase inhibitor, is administered orally once daily and has strong antiviral activity against HCV genotype 1 when used in combination with PEG-IFN and ribavirin. A double-blind placebo-controlled dose-ranging study of PSI-7977 in patients with HCV genotype 1 documented a rapid virologic response (RVR) in 98% of patients, with an end-of-treatment response at 24 weeks in 91%. The RVR in the placebo group was 19%, and the end-of-treatment response was 50%. Of specific note, all patients with the difficult-to-treat interleukin 28B single-nucleotide polymorphism T/T mutation had an RVR -- all became HCV-negative by week 3, and 100% went on to achieve an SVR.
In another phase 2 study, this investigational compound allowed all patients to achieve an RVR. More than 80% of the treatment group had nondetectable HCV RNA at 2 weeks, and all patients had undetectable levels at 3 weeks. All patients achieved normalization of serum alanine aminotransferase levels. No serious adverse events were attributable to PSI-7977, and as expected, safety and tolerability were greatest in the IFN-free treatment group.
Thus, PSI-7977 exhibits high-potency antiviral activity against a broad range of HCV genotypes, has a high barrier to resistance, and has a reassuring safety profile. This drug also allowed a shorter duration of therapy for viral clearance. These studies support the continued exploration of this drug and related compounds -- alone, with other direct-acting antiviral agents, or with shorter duration of IFN therapy in patients with all HCV genotypes. Further studies will hopefully confirm the initial excitement and optimism and, of note, will document the spectrum of potential adverse effects.
Getting to IFN-Free Regimens
Within the next 5 years, IFN-free regimens may be a reality and available in the clinic. As Sharma and Lok stated, "[I]t is possible that some of these regimens will also be ribavirin free. This will be good news for patients who wish to be treated but have to defer treatment because of contraindications to use of PEG-IFN or ribavirin, or out of concerns about their ability to tolerate these medications." The ideal strategy is on the horizon.
- Ghany MG, Nelson DR, Strader DB, Thomas DL, Seeff LB; American Association for the Study of Liver Diseases. An update on treatment of genotype 1 chronic hepatitis C virus infection: 2011 practice guideline by the American Association for the Study of Liver Diseases. Hepatology. 2011;54:1433-1444. Abstract
- Jensen DM. A new era of hepatitis C therapy begins. N Engl J Med. 2011;364:1272-1274. Abstract
- Sharma P, Lok AS. Interferon-free treatment regimens for hepatitis C: are we there yet? Gastroenterology. 2011;141:1963-1967.
- Gane EJ, Roberts SK, Stedman CA, et al. Oral combination therapy with a nucleoside polymerase inhibitor (RG7128) and danoprevir for chronic hepatitis C genotype 1 infection (INFORM-1): a randomised, double-blind, placebo-controlled, dose-escalation trial. Lancet. 2010;376:1467-1475. Abstract
- Zuezem S, Asselah T, Angus P, et al. Efficacy of the protease inhibitor BI 201335, polymerase inhibitor BI 207127, and ribavirin in patients with chronic HCV infection. Gastroenterology. 2011;141:2047-2055. Abstract
- Lawitz E, Lalezar JP, Hassanein T, et al. Once-daily PSI-7977 plus PEG/RBV in treatment-naive patients with HCV GT1: robust end of treatment response rates are sustained post-treatment. Program and abstracts of The Liver Meeting 2011: American Association for the Study of Liver Diseases (AASLD) 62nd Annual Meeting; November 9-13, 2011; Boston, Massachusetts. Abstract 225.
- Gane EJ, Stedman CA, Hyland RH, et al. Once daily PSI-7977 plus RBV: pegylated interferon-alfa not required for complete rapid viral response in treatment-naive patients with HCV GT2 or GT3. Program and abstracts of The Liver Meeting 2011: American Association for the Study of Liver Diseases (AASLD) 62nd Annual Meeting; November 9-13, 2011; Boston, Massachusetts. Abstract 34.