Development of novel agents for the treatment of chronic hepatitis C infection: Summary of the FDA Antiviral Products Advisory Committee recommendations

Direct-acting antiviral drug approvals for treatment of chronic hepatitis C virus infection: Scientific and regulatory approaches to clinical trial designs

Therapeutic options for treatment of chronic hepatitis C have improved substantially since the approval of direct-acting antiviral agents (DAAs). Several interferon (IFN)-free or IFN- and ribavirin (RBV)-free treatment regimens with shorter durations and improved efficacy and safety profiles are now available. The U.S. Food and Drug Administration (FDA) used several scientific approaches and regulatory mechanisms, such as (1) use of a "validated" surrogate (sustained virological response) for a primary endpoint, (2) shortening the time point for measuring the surrogate by 12 weeks, (3) use of historical controls when clinically appropriate, and (4) use of modeling when scientifically sound to extend treatment indications to subpopulations not fully evaluated in clinical trials, which had an impact on DAA development and subsequent approvals. This article intends to provide increased transparency about the FDA's scientific approaches and regulatory processes that supported drug development and marketing approval of DAAs for treatment of hepatitis C, a serious, life-threatening infection.

Challenges in the treatment of chronic hepatitis C in the HIV/HCV-coinfected patient

Hepatitis C virus (HCV) and HIV are common coinfections that convey a shortened lifespan, mostly related to liver disease. Treatment against HCV in the coinfected patient is notoriously more complex and challenging. There are no optimal treatment algorithms for HIV/HCV coinfected patients as efficacy of approved anti-HCV therapies is low with relevant side effects. The use of direct-acting antivirals for anti-HCV therapy has the potential to improve therapeutic efficacy, but also increase side effects and drug-drug interactions. In spite of all of this, the most important and significant fact is that chronic hepatitis C is potentially curable, and the eradication of the HCV infection is a crucial outcome in this population. The establishment of a productive collaboration among the regulatory agencies, the medical community and the pharmaceutical industry could lead to faster access to more effective HCV therapies for the coinfected patient and eventually stop the progression of liver disease in these patients.

Hepatitis C and HIV co-infection: new drugs in practice and in the pipeline

HCV/HIV coinfection continues to represent a serious health issue with risk of liver disease progression and development of hepatocellular carcinoma. Pegylated interferon with ribavirin is approved for treatment but results are suboptimal and tolerability poor. First-generation HCV protease inhibitors appear to significantly improve HCV treatment response in the setting of HIV infection. Interactions with HIV protease inhibitors have been documented, but the significance of this in terms of adverse reactions and HCV or HIV viral breakthrough remains uncertain. Next generation agents hold the promise of even better efficacy, with improved dosing schedules and perhaps decreased risk of drug:drug interactions.

Retreatment of patients with chronic hepatitis C relapsers to a previous antiviral treatment

BACKGROUND

The efficacy of retreatment with pegylated interferon (PEG-IFN) plus ribavirin for patients relapsing after a previous treatment remains to be fully elucidated, although extended treatment seems to be the best option in such cases.

AIM

To evaluate the efficacy of two extended protocols in patients with genotypes 1 or 4, or those with genotypes 2 or 3.

METHODS

A total of 181 patients who had relapsed after a previous antiviral treatment with PEG-IFNα2a plus weight-based ribavirin were offered retreatment with the same dose of both PEG-IFN plus ribavirin, to be continued for 48 weeks in those with genotypes 2 or 3 (group 1), and for 72 weeks in those with genotypes 1 or 4 (group 2).

RESULTS

A total of 59 patients (32.5%) refused the retreatment, while 122 (78 men, 44 women) patients were enrolled in the study: 41 were allocated in group 1 and 81 in group 2. Cirrhosis at baseline (staging 5/6 according to Ishak's score was recorded in 11 patients, six in group 1 and five in group 2). Nine patients (7.3%) in group 2 discontinued the treatment (due to lack of response). The remaining patients completed the treatment and were followed-up for at least 12 months after the treatment. Sustained virological response (SVR) rate was 82.9% in group 1 and 50.6% in group 2.

CONCLUSION

Patients with chronic hepatitis C with 'easy genotypes' relapsers to a previous antiviral treatment have more than 80% probability of achieving a SVR with a 48-week retreatment. Patients with 'difficult genotypes' have more than 50% chance of a SVR after a 72-week extended treatment.

Lessons from HIV therapy applied to viral hepatitis therapy: summary of a workshop

Therapies for hepatitis B virus (HBV) have continued to evolve, and new therapies for hepatitis C virus (HCV) will soon be available in clinical practice. These medications for hepatitis C will mark the first time that direct antivirals that target HCV functions have been used. When such drugs are used as single agents, previously existing mutants with reduced susceptibility to them are rapidly selected. The relationship between these drug-resistant mutants and "wild-type" virus is unclear, but resistant strains likely have the potential to maintain the progression of liver disease despite successful treatment of "wild-type" virus. Resistant HBV and now HCV are already a clinical problem. The same issue was recognized very early in the development of therapy against HIV, with azidothymidine-resistant mutants detected within the first weeks of therapy. Clinical investigation and a progressive understanding of the pathogenesis of the disease overcame this challenge and led to the substantial and durable benefits of antiretroviral therapy that are evident today. To bring experts from the fields of HIV and viral hepatitis virology and therapy together for interactive discussions about how to apply the lessons from HIV to the further development of viral hepatitis therapy, the American Association for the Study of Liver Diseases held a single-topic conference entitled "Viral Hepatitis Therapy: Lessons to be Learned From HIV" on 24-26 July 2008. This article summarizes that conference.

Management of nonresponsive hepatitis C

More than 50% of hepatitis C virus (HCV)-infected patients do not respond to the classical pegylated interferon (PEG-IFN)/ribavirin combination therapy. However, failing to respond to one course of treatment is not synonymous of therapy failure and retreatment is often beneficial. Alternative retreatment strategies include repeating the classical standard of care with an optimized drug regimen and adherence, including ribavirin serum concentration adjustment, correcting, if at all possible, comorbidities, and the addition of new specific anti-HCV molecules to the backbone of pegylated interferon/ribavirin. Options of retreatment should include consensus and natural interferons. For patients with advanced disease exposed to a high risk of lethal complications, customized maintenance therapy could be an effective option since it may slow down complications in some patients. Since low-dose interferon monotherapy is not sufficient, such a maintenance therapy remains to be verified via clinical trials. New possibilities of noninvasive assessment of fibrosis and the use of genetic tests to predict fibrosis progression and responsiveness to interferon are major emerging opportunities that run parallel to the revolution of the pharmacologic armentarium.

Management of chronic hepatitis C patients who have relapsed or not responded to pegylated interferon alfa plus ribavirin

Development of therapeutic strategies for patients with chronic hepatitis C who experience virological breakthrough, relapse or nonresponse lag behind those for treatment-naïve patients. The probability of a previously treated patient responding to re-treatment depends on the nature of the previous regimen, the magnitude of the response to previous treatment and the patient's characteristics. Relapsers have higher sustained virological response rates than nonresponders when re-treated with pegylated interferon plus ribavirin. Re-treatment of nonresponders to pegylated interferon plus ribavirin with the standard 48-week regimen resulted in an approximate 6% sustained response rate in the EPIC-3 program. In the REPEAT trial, the sustained response rate was significantly higher in nonresponders to pegylated interferon alfa-2b (12 kD) plus ribavirin randomized to 72 weeks of peginterferon alfa-2a (40 kD) plus ribavirin, compared with a 48-week regimen (16%vs 8%, P = 0.0006). Based on available data, extended treatment is the best option for these individuals. Undetectable viral RNA at week 12 is an important criterion for re-treatment in the REPEAT and EPIC studies. Maintenance therapy with pegylated interferon is generally ineffective in nonresponders and cannot be recommended. Directly acting antivirals may increase response rates and the burden of adverse events when combined with the standard of care, but will not be available for some years. In conclusion, after careful evaluation of an individual's benefit-risk ratio, a 72-week regimen is the preferred strategy for optimizing sustained response rates in patients who have not responded to the standard of care, provided that viral RNA is undetectable at week 12 of re-treatment.

A randomized controlled trial of thymalfasin plus transarterial chemoembolization for unresectable hepatocellular carcinoma

PURPOSE

Patients with advanced hepatocellular carcinoma (HCC) have few treatment options. Thymalfasin (thymosin α-1) is an immunomodulator that may increase response to ablative therapy through direct anti-tumor action or enhanced protection against infections. We compared transarterial chemoembolization (TACE) plus thymalfasin with TACE alone for unresectable HCC.

METHODS

In this phase II, randomized trial, 25 patients received either TACE plus thymalfasin (1.6 mg SC, 5 times weekly; n = 14) or TACE alone (n = 11) for 24 weeks. Response was defined as transition to transplant eligibility or lack of disease progression through week 72. Survival was assessed through 24 months post-treatment.

RESULTS

Eight of fourteen (57.1%) patients in the TACE + thymalfasin group versus 5 of 11 (45.5%) patients in the TACE-only group became responders (P = 1.0). Four of fourteen TACE + thymalfasin patients versus none of 11 TACE-only patients became eligible for transplant. Median overall survival time was 110.3 weeks for the TACE + thymalfasin group versus 57.0 weeks for the TACE-only group (P = 0.45). Seven patients in each group experienced serious adverse events; there were no bacterial infections in the TACE + thymalfasin group versus 4 in the TACE-only group. There were 3 deaths in the TACE + thymalfasin group and 5 in the TACE-only group.

CONCLUSIONS

In patients with unresectable HCC, TACE + thymalfasin resulted in numerically higher rates of survival and tumor response, including transplant candidacy, with fewer bacterial infections, than TACE alone. Treatment regimens for HCC including thymalfasin as an immunomodulator should be evaluated in larger trials.

Blunted cytopenias and weight loss: new correlates of virologic null response to re-treatment of chronic hepatitis C

BACKGROUND & AIMS

Peginterferon with ribavirin therapy for chronic hepatitis C leads to sustained loss of serum hepatitis C virus (HCV) RNA in half of treated patients. Although viral kinetic profiles in treatment responders shed light on the mechanism of action of interferon and ribavirin, minimal information is available to explain why some patients experience little or no virologic suppression.

METHODS

We evaluated factors that might be associated with the lack of a week-20 virologic response in previous nonresponder patients undergoing peginterferon and ribavirin retreatment. Among 1145 patients enrolled in the Hepatitis C Antiviral Long-term Treatment against Cirrhosis Trial's lead-in treatment phase, 588 who received more than 80% of prescribed therapy for 20 weeks were analyzed.

RESULTS

By week 20, 245 patients (41.7%) had undetectable HCV RNA (full response), 186 (31.6%) had a 1 log(10) or greater decrease in HCV RNA (partial response), and 157 (26.7%) had less than a 1 log(10) decrease (null response) in HCV RNA. Null response was associated independently with African American race, genotype-1 infection, and less reduction in body weight, platelets, and white blood cells during treatment.

CONCLUSIONS

On-treatment variables associated with null response suggest a blunted systemic response to interferon. These observations have important implications for the design and analysis of trial results in which novel agents are evaluated. Further studies are needed to discern whether host interferon resistance, viral drug resistance, or both are playing a role in patients who have no virologic response to interferon treatment.