Sofosbuvir - Novel antiviral for chronic hepatitis C backed for approval

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Infectious Diseases

Novel antiviral for chronic hepatitis C backed for approval
October 28 2013
By: ELIZABETH MECHCATIE, Family Practice News Digital Network

SILVER SPRING, MD. – A Food and Drug Administration advisory panel has unanimously recommended the approval of sofosbuvir, a new antiviral drug, for treating adults with chronic hepatitis C infection, with several panelists describing the votes to approve the drug as historic.

At a meeting on Oct. 25, the FDA’s Antiviral Drugs Advisory Committee voted 15-0 to recommend approval of sofosbuvir for the treatment of two different chronic hepatitis C indications: In combination with pegylated interferon and ribavirin for treatment-naive adults with genotype 1 and 4 infections; and in combination with ribavirin for adults with genotype 2 and 3 infections.

If approved – which is expected – the second indication will mark the first approval of a treatment for chronic hepatitis C with an interferon-free regimen, and it will be the first drug in its class to be approved. Sofosbuvir is a nucleotide analogue inhibitor of the hepatitis C virus (HCV) NS5B polymerase enzyme, which plays an important role in HCV replication and is active against HCV genotypes 1 (the most common genotype in the United States), 2, 3, 4, 5, and 6. It is taken orally once a day at a 400-mg dose.
 

Gilead is also conducting a phase II study of patients on a liver transplant list who have hepatocellular carcinoma and genotypes 1-6 and were treated with sofosbuvir plus ribavirin for a maximum of 24 weeks (which was extended to 48 weeks) or until transplant. HCV almost always recurs after liver transplantation, and there are no approved treatments to prevent recurrence of HCV after liver transplantation. In the study, 64% of the patients met the primary efficacy endpoint – HCV RNA below detectable levels 12 weeks after transplant.

 

Panelists said there is a need to treat this group of patients, who are increasing in numbers and are very challenging to treat, and they should be studied further.

 

Summarizing the FDA’s view of the sofosbuvir data, Dr. Poonan Mishra, a medical officer in the FDA’s division of antiviral products, said that, for patients with chronic hepatitis C infection, sofosbuvir, in combination with ribavirin, provides the first "all oral interferon-free regimen" for patients with genotype 2 or 3 infections. Combined with pegylated interferon and ribavirin, sofosbuvir "provides improved efficacy and shorter treatment duration for patients with genotype 1 or 4 HCV infection," she added. The results in the liver transplant population were "encouraging," and address an unmet need for these patients, she said.

 

The regimens of sofosbuvir combined with ribavirin or PR in the study were well tolerated in the different groups of patients, including those waiting for liver transplant, and there were no clusters or trends of any specific types of adverse events identified. An evaluation of cardiac disorders in treated patients found no obvious safety issues related to cardiac toxicity, according to the FDA. A drug in development in the same class was associated with cardiac toxicity.

 

The FDA is expected to make a decision by Dec. 8. Sofosbuvir also is under review in the European Union, Australia, Canada, New Zealand, Switzerland and Turkey, according to Gilead.
 

The FDA usually follows the recommendations of its advisory panels. Members of FDA panels have usually been cleared of conflicts related to the product under review; occasionally, a panelist is given a waiver, but not at this meeting.

This is "truly a historic moment," said panelist Dr. Demetre Daskalakis, medical director of the HIV program at Mt. Sinai School of Medicine, New York. "I can’t wait to get this drug into the clinic. We are all excited," he added. The consumer representative on the panel, Daniel Raymond, policy director at the Harm Reduction Coalition, New York City, said that the company had "pulled off the hat trick" of superior efficacy, safety, and convenience over current treatments.

"I voted yes because, quite simply, this is a game changer," said Dr. Marc Ghany, staff physician in the liver diseases branch at the National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, Md.

The manufacturer, Gilead Sciences, has proposed that sofosbuvir be approved for treating chronic hepatitis C infection in combination with other agents in adults with genotypes 1-6 and/or adults waiting for a liver transplant, with different regimens of ribavirin, with or without pegylated interferon. The data on patients with genotypes 5 and 6 and on pretransplant patients are limited, and the panel was not asked to vote on approval for patients with those genotypes, or on approval for the pretransplant population.

The company presented the results of four phase III trials in patients with genotypes 2 and 3, which included an open-label study and randomized double-blind studies. The primary endpoint in all studies was the sustained virologic response rate (undetectable HCV) 12 weeks after active treatment was stopped (SVR12). In the studies, more than 1,000 patients received sofosbuvir.

The SVR12 rates of genotype 2 patients treated with sofosbuvir plus ribavirin for 12 weeks ranged from 93% to 97% among those who were treatment naive, and from 82% to 90% among those who were treatment experienced. For those with genotype 3 treated with sofosbuvir plus ribavirin for 24 weeks, the SVR12 rates were 93% among those who were treatment naive and 77% for those who were treatment experienced.

In an open-label study of 327 treatment-naive patients with genotypes 1, 4, 5, and 6, patients were treated with sofosbuvir plus pegylated interferon and ribavirin (PR) for 12 weeks. Most (292) of the patients had genotype 1, followed by genotype 4 (28 patients). The SVR12 rates were 89% among those with genotype 1 and 96% among those with genotype 4. The one patient with genotype 5 and all 6 patients with genotype 6 achieved an SVR12.

 

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