BOSTON – the forthcoming availability of the protease inhibitors telaprevir and boceprevir for the treatment of chronic hepatitis C is likely to vastly improve virologic response rates and cut treatment times, but experts warn that such advancements need to be balanced against the "huge potential" for misuse of the agents and the need to manage side effects and monitor for antiviral resistance.
When used in combination with standard therapy of pegylated interferon plus ribavirin-based therapy, both of these investigational drugs improved sustained virologic response rates and reduced treatment duration, compared with standard therapy alone, in four pivotal, phase III trials reported at the annual meeting of the American Association for the Study of Liver Diseases.
Telaprevir Boosts Viral Cure Rates
In the ADVANCE trial, a three-arm, double-blind, placebo-controlled study, investigators compared two telaprevir-based regimens with standard therapy in 1,088 treatment-naive patients with chronic genotype 1 hepatitis C virus (HCV) infection, according to lead investigator Dr. Ira M. Jacobson of New York Weill Cornell Medical Center in New York City.
Patients in treatment arms 1 and 2 received 750 mg of telaprevir plus standard therapy for 8 and 12 weeks, respectively, whereas patients in the control group received standard therapy alone, which consisted of 180 mcg/week of pegylated interferon alfa-2a and 1,000-1,200 mg/day of ribavirin.
Patients who achieved extended, rapid virologic response (RVR) – defined as undetectable HCV RNA viral load at treatment weeks 4 and 12 – were treated with standard therapy for an additional 16 and 12 weeks in the 8- and 12-week telaprevir arms, respectively, for a total of 24 weeks, Dr. Jacobson explained. Patients in whom HCV RNA was detectable at either week 4 or 12 received an additional 40 and 36 weeks of therapy, respectively, for a total of 48 weeks, he said. The control group underwent standard therapy for 48 weeks.
Compared with 44% of patients in the control group who achieved sustained virologic responses (SVR) 24 weeks after the last treatment, significantly more patients in both telaprevir arms – 69% of the 8-week group and 75% of the 12-week group – met that end point, Dr. Jacobson reported.
The extended RVR rates in the 8- and 12-week groups were 57% and 58%, respectively, compared with 8% in the control arm, he said.
Significantly improved SVRs were also observed in difficult-to-treat subgroups, according to Dr. Jacobson.
"Among black patients, the [SVR] rates were 58% and 62% in the 8- and 12-week treatment arms, and 25% in the control arm, and in cirrhotic patients the respective rates were 53%, 62%, and 33%," he reported.
Rates of treatment discontinuation due to adverse events, such as rash and anemia, were 8% and 7% in the 8- and 12-week telaprevir groups and 4% in the control group, "which is an improvement, compared with the previously reported profile," he said.
The phase III, open-label ILLUMINATE trial was designed to determine whether extending the telaprevir and standard therapy regimen from 24 to 48 weeks would be beneficial in treatment-naive, genotype 1 HCV patients who achieved extended RVR. In all, 540 patients were initially treated with the 12-week telaprevir regimen described above. Of the 352 patients who achieved RVR, 322 remained on treatment and were randomized to either a 24-week or 48-week treatment arm.
"The [SVR] rates associated with the 24-week and the 48-week arms were statistically similar, at 92% and 87.5%, respectively," reported Dr. Kenneth E. Sherman of the University of Cincinnati. Analyses of the data based on race and extent of liver damage showed that 88% of black patients who experienced extended RVR achieved SVR in both the 24- and 48-week treatment arms, and 82% and 88% of patients with advanced fibrosis/cirrhosis achieved SVR in the 24-week and 48-week arms, respectively, he said.
There were more adverse event–related treatment discontinuations in the longer-treatment group (12.5% vs. 0.6%), suggesting a benefit to the shorter-duration therapy, Dr. Sherman stated. The high viral cure rate observed in the study – the overall SVR rate was 72% in an intent-to-treat analysis – "[supports] the role of response-guided therapy with telaprevir-based regimens" in treatment-naive patients," he said.
Previous Nonresponders Benefit From Boceprevir
Response-guided, fixed-duration therapy with boceprevir was safe and effective in a cohort of HCV genotype 1 patients who were enrolled in the RESPOND-2 study and who failed standard therapy, reported lead investigator Dr. Bruce R. Bacon of St. Louis University. The 403 patients included those in whom prior standard therapy induced no notable decrease in HCV viral load (null responders) or a "not undetectable" decrease in HCV viral load (nonresponders), as well as those in whom prior treatment initially resulted in undetectable HCV RNA, followed by a viral rebound (relapsers), he said.