Boceprevir Phase II Study Showed High Rate of Sustained Response With 28- and 48-Week Regimens in Genotype 1 Treatment-Naive Hepatitis C Patients
Saturday November 1, 11:00 am ET
Interim results of HCV SPRINT-1 study presented at AASLD annual meeting
Pivotal Phase III studies ongoing in treatment naive patients and those who failed prior treatment
SAN FRANCISCO, Nov. 1 /PRNewswire-FirstCall/ -- Schering-Plough Corporation (NYSE: SGP - News) today reported that a planned interim analysis of a Phase II study showed that boceprevir, its investigational oral hepatitis C protease inhibitor, in combination with peginterferon and ribavirin markedly increased sustained virologic response (SVR) rates with 28 weeks of therapy and nearly doubled SVR with 48 weeks of therapy compared to current standard of care, peginterferon and ribavirin (control group) for 48 weeks. These results from the HCV SPRINT-1 study in 595 treatment-naive patients with chronic hepatitis C virus (HCV) genotype 1 were presented at the 59th American Association for the Study of Liver Diseases (AASLD) Annual Meeting.(1)
In a 48-week boceprevir regimen, the SVR rate was 74 percent at 12 weeks after the end of treatment (SVR 12) in patients who received 4 weeks of PEGINTRON(TM) (peginterferon alfa-2b) and REBETOL® (ribavirin, USP) prior to the addition of boceprevir (800 mg TID) (P/R lead-in). In a 28-week boceprevir regimen, the SVR rate was 56 percent at 24 weeks after the end of treatment (SVR 24) in patients who received the P/R lead-in. These results compared to a 38 percent SVR rate (SVR 12) for patients in the control group receiving 48-weeks of PEGINTRON and REBETOL alone (ITT).(2-4)
Importantly, predictability of attaining SVR 12 or 24 based on rapid virologic response (RVR) was greater for boceprevir patients in the lead-in arms compared to the no lead-in arms. In addition, fewer patients in the lead-in arms discontinued treatment due to viral breakthrough. RVR is defined as undetectable virus (HCV-RNA) in plasma on or before week 4 of boceprevir treatment.
"The high response rates seen with boceprevir in this study are very exciting, especially given that genotype 1 is the most common and hardest to treat form of hepatitis C," said Paul Kwo, M.D., associate professor of medicine and medical director, liver transplantation, Department of Medicine, Division of Gastroenterology/Hepatology, Indiana University School of Medicine, Indianapolis, and lead investigator of the study. "Boceprevir was well tolerated by patients in this study, and the use of the 4-week lead-in prior to the addition of boceprevir appears to reduce the incidence of viral breakthrough regardless of treatment duration and may improve SVR over a 48-week treatment period."
The rationale for this novel lead-in treatment regimen is based on the fact that both PEGINTRON and REBETOL reach steady-state concentrations by week 4, so patients have the protease inhibitor added at a time when the backbone drug levels have been optimized. In addition, the patient's immune system will have been activated and primed by PEGINTRON at the time that boceprevir is added to the regimen. This approach may minimize the period of time when there is a "functional monotherapy" with a direct antiviral, potentially reducing the likelihood for the development of resistance.
Safety data from the study showed that the most common adverse events reported in the boceprevir arms were fatigue, anemia, nausea and headache. No increase in skin adverse events (rash or pruritus) was observed in the boceprevir arms beyond what was seen in the PEGINTRON and REBETOL control arm.
Treatment discontinuations due to adverse events were between 9 and 19 percent for patients in the boceprevir arms, compared to 8 percent for the control arm. Treatment discontinuations for boceprevir patients due to viral breakthrough were fewer in the 28- and 48-week lead-in arms (4 and 5 percent, respectively) compared to the no lead-in arms (7 and 11 percent, respectively).
About the HCV SPRINT-1 Study
In this Phase II study, known as HCV SPRINT-1 (HCV Serine Protease Inhibitor Therapy-1), boceprevir (800 mg TID) was evaluated in three treatment regimens: 4 weeks of PEGINTRON (1.5 mcg/kg once weekly) and REBETOL (800-1400 mg daily based on patient weight) therapy followed by the addition of boceprevir to the combination for 24 or 44 weeks (totaling 28 or 48 weeks of treatment), boceprevir in combination with PEGINTRON and REBETOL at the doses described above for 28 or 48 weeks, and, in Part II of the study, boceprevir in combination with PEGINTRON and low-dose REBETOL (400-1000 mg daily based on patient weight) for 48 weeks, compared to a control of PEGINTRON (1.5 mcg/kg once weekly) and REBETOL (800-1400 mg daily based on patient weight) alone for 48 weeks (an approved treatment regimen). The primary endpoint of the study is SVR after 24 weeks of follow up (SVR 24). This is an ongoing study and SVR 24 rates are not yet available for patients in the 48-week boceprevir arms or the 48-week control arm of the study. In addition, SVR rates are not yet available and consequently results are not being reported for the boceprevir arm with low-dose REBETOL (n=59) compared to contemporaneous control (n=16) as described above.
Sustained Virologic Response (ITT)*
Treatment Arm All patients
No P/R Lead-in 28 Weeks 55% (59/107)
P/R Lead-in 28 Weeks 56% (58/103)
No P/R Lead-in 48 Weeks 66% (68/103)
P/R Lead-in 48 Weeks 74% (76/103)
P/R Control 48 Weeks 38% (39/104)
P/R Lead-in = PEGINTRON and REBETOL for 4 weeks prior to the addition of boceprevir
P/R Control = PEGINTRON and REBETOL alone for 48 weeks
* SVR 12 for 48 week arms; SVR 24 for 28 week arms(2-4)
In the study, predictability of attaining SVR (12 or 24) based on rapid virologic response (RVR) following 28 or 48 weeks of the boceprevir regimen was greater for patients in the lead-in arms (82 and 92 percent respectively) compared to the no lead-in arms (74 and 82 percent, respectively).
The HCV SPRINT-1 study was conducted at sites across the United States, Canada and Europe. Overall, 77 percent of the 595 patients in the study were enrolled in the United States. African-Americans represent 16 percent of the patients enrolled and 7 percent of patients in the study are cirrhotic.
Update on Boceprevir Phase III Studies
Schering-Plough is conducting two large ongoing pivotal Phase III studies of boceprevir in patients chronically infected with HCV genotype 1. One study is in treatment-naive patients and the other in patients who failed prior treatment (relapsers and nonresponders). The two randomized, double-blind, placebo-controlled studies evaluate the efficacy of boceprevir in combination with PEGINTRON and REBETOL compared to standard of care with PEGINTRON and REBETOL alone.
The study in treatment-naive patients is known as HCV SPRINT-2 and the study in patients who failed prior treatment is known as HCV RESPOND-2. The two studies are expected to enroll a total of more than 1,400 patients at U.S. and international sites.
For more information about these ongoing Phase III studies, please visit www.clinicaltrials.gov, search term boceprevir.
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