(Reuters) - AbbVie Inc's all-oral hepatitis C therapy cured 96 percent of difficult-to-treat patients in a late-stage clinical trial after 12 weeks, keeping the company well placed in a highly competitive race to deliver new treatments for the serious liver disease.
The study of 394 patients with the most common Genotype 1 version of the virus tested the AbbVie regimen in people who had failed to be cured by the older standard treatments of pegylated interferon and ribavirin.
In results issued by AbbVie on Tuesday, nearly half of those in the Phase III trial dubbed Sapphire-II were prior null responders - a particularly difficult to treat group whose virus had no response to treatment with the older drugs.
The impressive cure rate after just 12 weeks of therapy mirrors the results seen last month in another late stage study that tested the all oral AbbVie regimen in potentially less challenging patients who had received no prior treatment for their hepatitis C.
Two percent of patients in the Sapphire-II trial experienced relapse or virologic breakthrough in which the virus rebounds after initially responding to treatment, while the discontinuation rate due to side effects was 1 percent.
Patients in whom there is no detectable levels of the virus in the blood 12 weeks after completing 12 weeks of therapy have achieved SVR, or sustained virologic response, which is considered cured.
Alex Arfaei, an analyst with BMO Capital Markets, said in a research note that AbbVie's regimen "remains underappreciated" and forecast sales reaching $1.6 billion in 2017.
Several companies are developing hepatitis C treatment regimens that do not require injectable interferon, which causes miserable flu like symptoms that lead many patients to discontinue or delay treatment.
Gilead Sciences is widely perceived by industry analysts to be the leader in the all-oral hepatitis C field that is expected to garner billions of dollars in annual sales. Gilead last week had one of its closely watched new drugs approved by the U.S. Food and Drug Administration.
AbbVie, Bristol-Myers Squibb Co and Merck & Co are all seen as potential rivals with oral regimens that have shown impressive cure rates and also cut the current treatment duration to 12 weeks or less from the current 24- or 48-week treatment regimens.
Some analysts have said AbbVie's ability to compete could be hampered by a larger number of pills that must be taken than some of the rival regimens.
The AbbVie regimen includes three experimental direct acting antiviral drugs that each attack a different target necessary for virus replication, plus the older drug ribavirin.
The drugs are the protease inhibitor ABT-450, whose effect is boosted by a widely used antiviral called ritonavir; the polymerase inhibitor ABT-333, and ABT-267 from a highly promising new class known as NS5A inhibitors.
The regimen currently involves four pills a day plus typically 2 ribavirin pills a day.
AbbVie, which has four more Phase III trials underway, is also testing its drugs without ribavirin - a medicine that can cause anemia and other side effects. But other companies are shooting for combination regimens that involve just one or two pills a day.
"Gilead will have a convenience advantage," Arfaei said. "However, we do not believe convenience is as important for an 8-12 week treatment regimen that produces a cure compared with for example chronic HIV treatment."
Shares of Enanta Pharmaceuticals Inc, which co-developed ABT-450 with AbbVie, were up 22.2 percent to $36.25 on Nasdaq. They are up more than 70 percent since AbbVie released data from the first Phase III trial last month.
AbbVie shares were up 2.1 percent at $52.30 in afternoon trading on the New York Stock Exchange.
Additional reporting by Esha Dey in Bangalore; Editing by Tim Dobbyn