Merck recently reported that two pivotal Phase III registration studies for boceprevir, its investigational oral hepatitis C protease inhibitor, have been completed and met the primary endpoints: in both studies in patients with chronic hepatitis C virus (HCV) genotype 1 infection, the addition of boceprevir to treatment with PEGINTRON (peginterferon alfa-2b) and REBETOL (ribavirin, USP) (Peg/riba) significantly increased the number of patients who achieved sustained virologic response (SVR; defined as undetectable virus levels 24 weeks after the end of treatment), compared to control groups that received Peg/riba plus placebo.
Boceprevir, in combination with Peg/riba, is being studied for the treatment of patients with chronic hepatitis C genotype I who have previously been treated (treatment-failure; HCV RESPOND-2) and in patients who are new to treatment (treatment-naïve; HCV SPRINT-2). Abstracts for boceprevir studies have already been submitted for presentation at a medical meeting later this year, and additional abstracts are being submitted this week. Merck plans to submit a New Drug Application (NDA) for boceprevir to the U.S. Food and Drug Administration on a rolling basis, and expects to complete regulatory submissions in the U. S. and E.U. in 2010.
"There is a clear need for new treatment strategies for chronic hepatitis C," said Dr. Peter S. Kim, Ph.D., president, Merck Research Laboratories. "We look forward to seeking regulatory approvals to bring boceprevir forward to help treat people living with chronic hepatitis C."
The HCV RESPOND-2 and HCV SPRINT-2 studies each evaluated two treatment strategies with boceprevir: 48 weeks of treatment for all patients (4-week lead-in with 1.5 mcg/kg/week of PEGINTRON and an investigational dose of 600-1,400 mg/day of REBETOL, followed by the addition of boceprevir 800 mg three times a day for 44 weeks), and response-guided therapy, in which patients with undetectable virus at week 8 and again at certain points later in the studies were able to stop all treatment at 36 weeks in HCV RESPOND-2 and at 28 weeks in HCV SPRINT-2. Patients who did not meet these criteria continued treatment with Peg/riba alone for a total treatment duration of 48 weeks. Control groups in the studies received Peg/riba at the doses described above plus placebo for 48 weeks.
The HCV RESPOND-2 study was conducted in 403 patients who failed prior therapy at U.S. and international sites, and patients were randomized into the three groups (48 weeks control; 48 weeks control plus boceprevir; control plus boceprevir using response-guided therapy) at a 1:1:1 ratio. In the boceprevir 48-week treatment group, 66 percent of patients achieved SVR, and in the boceprevir response-guided therapy group, 59 percent of patients achieved SVR, compared to 21 percent of patients in the control group (p<0.0001 for="" both,="" intent-to-treat="" analysis).="">0.0001>
"These results are very exciting," said Bruce R. Bacon, M.D., professor of internal medicine, Saint Louis University School of Medicine, and co-principal investigator of the HCV RESPOND-2 study. "Patients who failed prior hepatitis C therapy are among the hardest to treat, and the use of boceprevir in this study helped significantly more of these patients achieve undetectable levels of the virus at 24 weeks after the end of therapy than treatment with Peg/riba alone."
In the HCV SPRINT-2 study, 1,097 treatment-naïve patients at U.S. and international sites were enrolled in two separate cohorts, one with 938 non-African-American/Black patients and the other with 159 African-American/Black patients. Patients were randomized into the three treatment groups (48 weeks control; 48 weeks control plus boceprevir; control plus boceprevir using response-guided therapy) at a ratio of 1:2:2. In the study overall, 66 percent of patients in the boceprevir 48-week treatment group achieved SVR, and 63 percent of patients in the response-guided therapy group achieved SVR, compared to 38 percent of patients in the control group (p<0.0001 for="" both,="" intent-to-treat="" analysis).="">0.0001>
As specified by the HCV SPRINT-2 study protocol, results for the non-African-American/Black and African-American/Black patient cohorts were analyzed separately. Several previous studies have shown that African-American/Black patients have a lower response to HCV treatment than non-African-American/Black patients.1-3 Among the non-African-American/Black patients in the boceprevir 48-week treatment group, 69 percent achieved SVR, and in the response-guided therapy group, 67 percent of patients achieved SVR, compared to 40 percent in the control group (p<0.0001 for="" both,="" intent-to-treat="" analysis).="" among="" the="" african-american/black="" patients,="" 53="" percent="" of="" patients="" in="" the="" 48-week="" treatment="" group="" and="" 42="" percent="" of="" patients="" in="" the="" response-guided="" therapy="" group="" achieved="" svr,="" compared="" to="" 23="" percent="" in="" the="" control="" group="" (p="0.004" and="" p="0.044," respectively,="" intent-to-treat="" analysis).="">0.0001>
"The response-guided therapy approach used in these studies enabled those patients – both treatment-failure patients and treatment-naïve patients – who had undetectable virus at certain points of the study to achieve SVR with a shorter total treatment duration than current standard therapy," said Fred Poordad, M.D., chief of hepatology in the division of gastroenterology at Cedars-Sinai Medical Center, associate professor of medicine at the David Geffen School of Medicine, University of California, Los Angeles (UCLA), and co-principal investigator of the HCV SPRINT-2 study.
In the HCV RESPOND-2 study, the five most common treatment-emergent adverse events reported for the boceprevir 48-week treatment group, boceprevir response-guided therapy group and control group, respectively, were: fatigue (57, 54, and 50 percent), headache (40, 43 and 49 percent), nausea (42, 44 and 38 percent), anemia (47, 43 and 20 percent) and dysgeusia (bad taste) (45, 43 and 11 percent). Treatment discontinuations due to anemia were 3 percent and 0 percent for the boceprevir groups, respectively, compared to 0 percent for the control group. Treatment discontinuations due to adverse events overall were 12 percent and 8 percent for the boceprevir groups, respectively, compared to 3 percent for the control group.
In the HCV SPRINT-2 study, the five most common treatment-emergent adverse events reported for the boceprevir 48-week treatment group, boceprevir response-guided therapy group and control group, respectively, were: fatigue (57, 53 and 60 percent), headache (46, 46 and 42 percent), nausea (43, 48 and 42 percent), anemia (49, 49 and 29 percent) and pyrexia (fever) (32, 33 and 33 percent). Treatment discontinuations due to anemia were 2 percent for each of the boceprevir groups compared to 1 percent for the control group. Treatment discontinuations due to adverse events overall were 16 percent and 12 percent for the boceprevir groups, respectively, compared to 16 percent for the control group.
About the studies
The HCV RESPOND-2 study was conducted in patients chronically infected with hepatitis C genotype 1 who failed prior therapy with peginterferon and ribavirin, including those who had experienced prior relapse or who were prior non-responders, and the HCV SPRINT-2 study was conducted in previously untreated (treatment-naïve) patients chronically infected with hepatitis C genotype 1. Approximately 25 percent of patients in each of the studies had less than a 1 log decrease in viral load after the 4-week Peg/riba lead-in period.
Sustained virologic response (SVR), the protocol-specified primary efficacy endpoint, is defined as achievement of undetectable HCV-RNA at 24 weeks after the end of treatment in all randomized patients treated with any study medication (Roche TaqMan LLD=9.3 IU/mL). Per protocol, if a patient did not have a 24-week post-treatment assessment, the patient's 12-week post-treatment assessment was utilized.
In the HCV RESPOND-2 study, patients in the response-guided therapy arm who had undetectable virus at treatment week 8 and week 12 received a total of 36 weeks of therapy (lead-in with Peg/riba followed by the addition of boceprevir for 32 weeks); patients with detectable virus at week 8, but undetectable virus at week 12, stopped boceprevir treatment at week 36 and continued on Peg/riba alone for an additional 12 weeks, for a total treatment duration of 48 weeks. Patients in any arm of the study who had detectable virus at week 12 were considered treatment failures and discontinued treatment.
In the HCV SPRINT-2 study, patients in the response-guided therapy group of the study who had undetectable virus at treatment week 8 through week 24 received a total of 28 weeks of therapy (lead-in with Peg/riba followed by the addition of boceprevir for 24 weeks); patients with detectable virus at week 8, but undetectable virus at week 24, stopped boceprevir treatment at week 28 and continued on Peg/riba alone for a total treatment duration of 48 weeks. Patients in any arm of the study who had detectable virus at week 24 were considered treatment failures and discontinued treatment.
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PEGINTRON is indicated for use in combination with REBETOL (ribavirin) for the treatment of chronic hepatitis C in patients three years of age and older with compensated liver disease.
The following points should be considered when initiating therapy with PEGINTRON in combination with REBETOL: (1) These indications are based on achieving undetectable HCV-RNA after treatment for 24 or 48 weeks and maintaining a Sustained Virologic Response (SVR) 24 weeks after the last dose. (2) Patients with the following characteristics are less likely to benefit from re-treatment after failing a course of therapy: previous nonresponse, previous pegylated interferon treatment, significant bridging fibrosis or cirrhosis, and genotype 1 infection. (3) No safety and efficacy data are available for treatment of longer than one year.
PEGINTRON is also indicated for use alone for the treatment of chronic hepatitis C in patients with compensated liver disease previously untreated with interferon alpha and who are at least 18 years of age.
The following points should be considered when initiating therapy with PEGINTRON alone: Combination therapy with REBETOL is preferred over PEGINTRON monotherapy unless there are contraindications to, or significant intolerance of, REBETOL. Combination therapy provides substantially better response rates than monotherapy.
Selected Safety Information on PEGINTRON
WARNING: RISK OF SERIOUS DISORDERS AND RIBAVIRIN-ASSOCIATED EFFECTS Alpha interferons, including PEGINTRON, may cause or aggravate fatal or life-threatening neuropsychiatric, autoimmune, ischemic, and infectious disorders. Patients should be monitored closely with periodic clinical and laboratory evaluations. Patients with persistently severe or worsening signs or symptoms of these conditions should be withdrawn from therapy. In many, but not all cases, these disorders resolve after stopping PEGINTRON therapy.
Use with Ribavirin: Ribavirin may cause birth defects and death of the unborn child. Extreme care must be taken to avoid pregnancy in female patients and in female partners of male patients. Ribavirin causes hemolytic anemia. The anemia associated with REBETOL therapy may result in a worsening of cardiac disease. Ribavirin is genotoxic and mutagenic and should be considered a potential carcinogen.
PEGINTRON is contraindicated in patients with known hypersensitivity reactions such as urticaria, angioedema, bronchoconstriction, anaphylaxis, Stevens-Johnson syndrome and toxic epidermal necrolysis to interferon alpha or any other component of the product, autoimmune hepatitis, and hepatic decompensation (Child-Pugh score greater than 6 [class B and C]) in cirrhotic CHC patients before or during treatment. PEGINTRON/REBETOL combination therapy is additionally contraindicated in women who are pregnant or may become pregnant, men whose female partners are pregnant, patients with hemoglobinopathies (e.g., thalassemia major, sickle-cell anemia), and patients with creatinine clearance less than 50 mL per min.
REBETOL therapy should not be started until a report of a negative pregnancy test has been obtained immediately prior to planned initiation of therapy. Patients should use at least two effective forms of contraception and have monthly pregnancy tests during therapy and for six months after completion of therapy. If this drug is used during pregnancy, or if a patient becomes pregnant, the patient should be apprised of the potential hazard to a fetus. A Ribavirin Pregnancy Registry has been established to monitor maternal-fetal outcomes of pregnancies in female patients and female partners of male patients exposed to ribavirin during treatment, and for six months following cessation of treatment. Physicians and patients are encouraged to report such cases by calling 1-800-593-2214.
Patients with the following conditions should be closely monitored and may require dose reduction or discontinuation of therapy:
Life-threatening or fatal neuropsychiatric events, including suicidal and homicidal ideation, depression, relapse of drug addiction/overdose, and aggressive behavior, sometimes directed towards others, have occurred in patients with and without a previous psychiatric disorder during PEGINTRON treatment and follow-up.
Serious adverse reactions have occurred in approximately 12 percent of subjects in clinical trials. The most common serious events occurring in subjects treated with PEGINTRON and REBETOL were depression and suicidal ideation, each occurring at a frequency of less than 1 percent. The most common fatal events occurring in subjects treated with PEGINTRON and REBETOL were cardiac arrest, suicidal ideation, and suicide attempt, all occurring in less than 1 percent of subjects.
The incidence of serious adverse reactions was comparable between PEGINTRON monotherapy (about 12 percent) and PEGINTRON/REBETOL combination therapy weight-based (12 percent) or flat-dose (17 percent). In many but not all cases, adverse reactions resolved after dose reduction or discontinuation of therapy. Some patients experienced ongoing or new serious adverse reactions during the 6-month follow-up period. In a study with PEGINTRON/REBETOL (weight-based) combination therapy in adult patients, anemia with weight-based dosing occurred at an increased rate (29 percent vs. 19 percent); however, the majority of these cases were mild and responded to dose reductions. The incidence of serious adverse reactions reported for the weight-based REBETOL group was 12 percent. There were 31 deaths in clinical trials which occurred during treatment or during follow-up. Of the deaths, 19 were patients on either PEGINTRON or PEGINTRON/REBETOL combination therapy and three occurred during the follow-up period but had been on PEGINTRON/REBETOL combination therapy.
Additional serious adverse reactions seen in clinical trials at a frequency of equal to or less than 1 percent included psychosis, aggressive reaction, relapse of drug addiction/overdose; nerve palsy (facial, oculomotor); cardiomyopathy, angina, pericardial effusion, retinal ischemia, retinal artery or vein thrombosis, blindness, decreased visual acuity, optic neuritis, transient ischemic attack, supraventricular arrhythmias, loss of consciousness; neutropenia, infection (sepsis, pneumonia, abscess, cellulitis); emphysema, bronchiolitis obliterans, pleural effusion, gastroenteritis, pancreatitis, gout, hyperglycemia, hyperthyroidism and hypothyroidism, autoimmune thrombocytopenia with or without purpura, rheumatoid arthritis, interstitial nephritis, lupus-like syndrome, sarcoidosis, aggravated psoriasis, urticaria, injection site necrosis, vasculitis, and phototoxicity.
Greater than 96 percent of all subjects in clinical trials experienced one or more adverse events. Most common adverse reactions (greater than 40 percent) in adult patients receiving either PEGINTRON or PEGINTRON/REBETOL are injection site inflammation/reaction, fatigue/asthenia, headache, rigors, fevers, nausea, myalgia, and anxiety/emotional lability/irritability.
The adverse reaction profile was similar between weight-based and flat-dose PEGINTRON/REBETOL therapies. Weight-based PEGINTRON/REBETOL dosing resulted in increased rates of anemia. Most common adverse reactions with PEGINTRON/REBETOL (weight-based) therapy were psychiatric, which occurred among 68-69 percent of patients and included depression, irritability, and insomnia, each reported by approximately 30-40 percent of subjects in all treatment groups. Suicidal behavior (ideation, attempts, and suicides) occurred in 2 percent of all patients during treatment or during follow-up after treatment cessation. Other common reactions included injection site reactions, fatigue/ asthenia, headache, rigors, fever, nausea, myalgia, anxiety/emotional lability/irritability. The severity of some of these systemic symptoms tends to decrease as treatment continues.
Subjects receiving PEGINTRON/REBETOL as re-treatment after failing a previous interferon combination regimen reported adverse reactions similar to previous treatment-naïve patients receiving this regimen.
In general, the adverse reaction profile in the pediatric population was similar to that observed in adults. Most common adverse reactions (greater than 25 percent) in pediatric patients receiving PEGINTRON/REBETOL are pyrexia, headache, neutropenia, fatigue, anorexia, injection site erythema, abdominal pain, and vomiting.
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