HIV has taught the pharmaceutical industry that the best way to fight an infectious virus that resists a single drug is to make a cocktail that attacks the virus in more than one way. Vertex Pharmaceuticals and its competitors are now following a similar formula with new therapies for hepatitis C.
Vertex, the Cambridge, MA-based company with operations in San Diego, offered a glimpse last week into its strategy for a two-drug combo that could significantly change hepatitis C treatment. If the company has mapped this out correctly, it could rid people of the virus while letting them ditch the detested standard therapies that force them to endure months of flu-like symptoms. I followed up last Friday to learn more from a conversation with Vertex’s chief medical officer, Bob Kauffman.
The big story from the past couple years at Vertex (NASDAQ: VRTX) is the development of its first-in-class protease inhibitor drug called telaprevir. This oral pill, taken two or three times a day, must be combined with the pegylated interferon alpha and ribavirin. It has excited researchers because it has been able to double the cure rate while shortening the course of therapy by half. That means that many more of 170 million people worldwide with chronic hepatitis C liver infections will be likely to seek out treatment, and be able to stand up to the side effects of standard therapy over a shorter period of time. If the ongoing clinical trials to test this idea are successful this year, Vertex could bring telaprevir to the market in 2011. U.S. sales alone could amount to more than $2 billion after a couple years, researchers say.
That will be headline news if and when it happens. But researchers around the world, and Vertex’s competitors, see even bigger advantages if someone can get rid of pegylated interferon alpha and ribavirin altogether. The vision is to combine a protease inhibitor like telaprevir with one or more other antiviral drugs that work differently, essentially blocking some of the escape routes that enable the virus to develop resistance to a single drug.
There are three other main therapeutic classes being tested in clinical trials—nucleoside polymerase inhibitors, non-nucleoside polymerase inhibitors, and NS5a inhibitors, Kauffman says. Vertex paid $375 million last year to acquire a small Canadian company, ViroChem Pharma, mainly to obtain a non-nucleoside polymerase inhibitor that Vertex thought would complement its own telaprevir. That drug, called VX-222, has shown promising antiviral punch in some small studies on its own, and now it is entering its first serious test in tandem with telaprevir in a clinical trial.
“It really became clear early on that these hepatitis C agents couldn’t really be given [as single agents] because of the virus’s ability to develop resistance,” Kauffman says. Combinations have long been thought to be the best way forward, and to get rid of the standard treatments. “That was the goal from the beginning,” Kauffman says.
Vertex spent the last year figuring out the right doses, and balance between the two drugs, that it thought would be ideal for a teleprevir/VX-222 combination trial. Last week, it unveiled the clinical trial that will test this idea. It will enroll 100 patients mostly in the U.S. The telaprevir dose will stay the same for everybody. Some will just get a low or high dose of VX-222, taken as a twice-daily oral pill, in combination with telaprevir. Others who enroll will get Vertex’s two experimental antivirals in addition to the standard pegylated interferon alpha and ribavirin.
The study’s primary objective is to measure safety, but assuming that checks out, Vertex really wants to answer two big questions in this study, Kauffman says. Can the antiviral combo treatment cure a satisfactory number of patients without having to subject them to the standard treatments? And can people be clinically cured in half the time with the new combination of antivirals?
How good is good enough? Kauffman didn’t give an exact number, but he noted that a little more than 80 percent of people in one previous Vertex study with telaprevir and the standard drugs have had undetectable amounts of virus in their blood for a full 24 weeks after completing their course of therapy. That’s what is considered a clinical cure, what is known medically as a “sustained viral response” or SVR. This new combo trial will ask that same question, and when the data comes back on SVR scores, it “has to be right up there” with the results from previous studies, he says.
Of course, the drug has to be well-tolerated, too, especially since it could be taken by millions of people with a chronic condition that isn’t immediately life-threatening. Telaprevir is known to be associated with skin rash, and the standard therapies are also associated with anemia. Vertex will want to comb through this data carefully to see whether adding another antiviral into the mix will add any new side effects, Kauffman says.
But the number everyone wants to see is a high SVR score among the two antiviral drugs alone. Enrollment in the study should be done by the end of June, and interim results should be available by the end of 2010.
“No one has proven the point that you can get an SVR without pegylated interferon and ribavirin,” Kauffman says. “It’s a leap that has to be made, and we want to be the first to make it.”
There are plenty of tough competitors chasing the same goal, although they are all attacking the problem in slightly different ways, Kauffman says. Bristol-Myers Squibb is developing a protease inhibitor to be used in combination with an NS5a inhibitor; Roche and its partners Intermune and Pharmassat are developing a nucleoside polymerase inhibitor with a protease inhibitor; and Gilead Sciences is also testing drugs from those two classes. Vertex is the only one testing a tandem of a protease inhibitor and a non-nucleoside polymerase inhibitor, Kauffman says.
Will two antivirals be strong enough together, or will somebody have to craft a cocktail with three different kinds of drugs to be potent enough? That’s still one of the unanswered questions that Vertex wants to know, Kauffman says. Others are sure to question the data that comes from a regimen lacking in the standard therapy, wondering whether those two drugs can produce a long-lasting cure, or whether the virus will bounce back. Vertex says it is confident that if its combo drug can eradicate the virus for 24 weeks after therapy, then it will have achieved a long-lasting clinical cure.
This trial will give Vertex a lot to think about as it prepares for the next steps of development in its antiviral combo. And this is all going on in parallel with three pivotal trials of telaprevir in combination with the standard meds. Kauffman oversees two separate medical teams at Vertex that have their eyes on the ongoing pivotal trials of telaprevir (which represent the present) as well as the telaprevir/VX-222 studies (representing the future).
“Vertex wants to be the leader in hepatitis C, so that means you always have to look ahead,” Kauffman says. “But you don’t want to take your eye off the ball either.”
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