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.
Potential for Misuse Is ‘Huge’
Before next year’s American Association for the Study of Liver Diseases meeting,
| |  Dr. Paul J. Pockros
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"we are going to see the approval of two direct-acting antiviral drugs – telaprevir and boceprevir. We anticipate the widespread use of these drugs in the United States and the European Union, as they’ve been shown to improve sustained virologic response rates by approximately 75% in treatment-naive patients," Dr. Paul Pockros said during the meeting. Unfortunately, there is also a "huge potential" for misuse of these drugs, owing to prescribing physicians’ poor understanding of the therapeutic populations, inadequate viral-assay testing, poor side-effect management, and lack of monitoring for antiviral resistance, he said.
The designs of the phase III trials on which the Food and Drug Administration approval will be based, as well as the resulting treatment regimens, are fairly complex, said Dr. Pockros, "so there will be lots of opportunities to screw things up." For example, he hypothesized, "I am sure that some patients are going to be put on telaprevir for 44 weeks with a 4-week pegylated interferon/ribavirin lead-in [even though the lead-in strategy was evaluated for boceprevir, not telaprevir], and other patients might be put on boceprevir for 12 weeks with no lead-in."
For optimal safety and efficacy, Dr. Pockros stressed, physicians must have a good understanding of the treatment regimens, particularly in special populations, and they must actively and frequently monitor for antiviral resistance. Additionally, physicians should anticipate problems with adherence, which is already an issue for some patients on standard therapy, he said, noting that – despite the shorter treatment duration – adding a third drug with its own set of side effects to the mix may not be realistic for patients with a history of poor compliance.
The objective for physicians should be "to keep our eyes on the ball," said Dr. Pockros. "Our primary goal moving forward with all of the new drugs is going to be eradicating the virus."
Paul J. Pockros, M.D., is head of the division of gastroenterology/hepatology and director of the Liver Research Consortium at the Scripps Clinic in La Jolla, Calif. He disclosed relationships with Vertex and Tibotec, which are involved in the development of telaprevir, and Merck, which manufactures boceprevir.
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