Wed Aug 4, 2010 12:51pm EDT
* 66 pct cure rate seen with Merck's boceprevir
* Merck to seek boceprevir approval by year's end
* Side effects raise questions in one of two trials
* Merck shares slightly higher
* Shares of rival drugmaker Vertex up 3.5 pct (Adds analyst comments, details on Merck and Vertex drugs; changes byline)
By Ransdell Pierson and Bill Berkrot
NEW YORK, Aug 4 (Reuters) - Merck & Co (MRK.N) said its experimental hepatitis C treatment met the main effectiveness goals of two late-stage studies and it expects to seek approval for the high-profile medicine by the end of the year.
But a much higher percentage of patients taking the Merck drug, compared with those taking standard treatments, dropped out of one of the trials due to adverse events, including anemia.
The drug, boceprevir, was one of the most important experimental products gained by Merck through its acquisition of Schering-Plough Corp last year.
In the two trials, 66 percent of patients who took boceprevir plus standard drugs for a full 48 weeks were cured of the serious liver disease, a significantly higher cure rate than for standard treatment alone. But that compares with a 75 percent cure rate seen in a separate trial of a rival drug being developed by Vertex Pharmaceuticals Inc (VRTX.O).
Boceprevir and Vertex's telaprevir are considered possible blockbuster products because of their potential to cure far more patients and in as little as half the time of standard drugs that require almost a year of treatment and often cause flu-like symptoms that are tough to tolerate.
Vertex shares rose 3.5 percent to $36.47 as investors compared the Merck data with recently released data on the Vertex drug. Merck said it would provide more detailed clinical trial data at a meeting of the American Association for the Study of Liver Diseases that begins Oct. 29 in Boston.
Merck shares rose 19 cents, or 0.5 percent, to $35.01.
The new class of drugs, which are combined with standard treatments, work against the liver-damaging hepatitis C virus by blocking a protein called protease that the virus requires to replicate. The current standard treatments involve a combination of the injectable drug interferon and an anti-viral pill called ribavirin.
"Based on today's top line data, we are maintaining our view that, while telaprevir will likely take a majority of the initial hepatitis C protease inhibitor market, boceprevir will play a role in the category," J.P. Morgan analyst Chris Schott said in a research note.
Schott said investors will get a better picture of the respective strengths and shortcomings of the two drugs when full late-stage trial data on telaprevir and boceprevir are unveiled at the upcoming Boston meeting.
Merck said boceprevir, taken in combination with the company's Pegintron brand of interferon and ribavirin, significantly increased the number of patients who achieved a sustained virologic response, or SVR -- meaning no detectable virus levels 24 weeks after the end of treatment -- compared with those who received the standard drugs plus a placebo.
Achieving SVR, in layman's terms, is considered being cured of the disease.
One of the trials, called HCV RESPOND-2, involved 403 patients with genotype 1, the most common form of hepatitis C, who had failed prior therapy with interferon and ribavirin. The other trial, called HCV SPRINT-2, enrolled 1,097 patients with genotype 1 who had not previously been treated for the virus.
In both trials, a significant number of patients received 48 full weeks of treatment. But 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 the smaller trial, and at 28 weeks in the larger study.
In the HCV RESPOND-2 study, 66 percent of those receiving boceprevir for 48 weeks were cured, while cures were seen in 59 percent of those receiving shorter treatment regimens of the medicine. That compared with a 21 percent cure rate for those receiving standard treatments.
In the HCV SPRINT-2 study of previously untreated patients, 66 percent of those receiving boceprevir for 48 weeks were cured, along with 63 percent of those on shorter regimens. Cures were seen in 38 percent of those receiving standard therapy.
Telaprevir's 75 percent cure rate in its own Phase III trial tested the drug in previously untreated patients.
Vertex is expected next month to unveil data from another late-stage trial of telaprevir in tougher-to-treat patients who had failed prior treatment with standard drugs.
Sanford Bernstein analyst Tim Anderson said available data from separate trials of boceprevir and telaprevir suggest the Merck drug is less effective.
Moreover, he said boceprevir seems more likely to cause anemia -- a side effect that could require patients to take intravenous anemia medicines that boost red blood cells. The question is whether the need for an additional anemia drug on top of the three-drug regimen will greatly discourage use of boceprevir, should it be approved.
Anderson forecast boceprevir would garner sales of $330 million in 2015, far below his forecast of $4.3 billion for the Vertex drug. (Reporting by Ransdell Pierson, Lewis Krauskopf and Bill Berkrot, editing by Maureen Bavdek, Dave Zimmerman and John Wallace)