This week the U.S. Food and Drug Administration (FDA) approved Johnson & Johnson’s new hepatitis C drug, which has been hailed as a cure for the infectious disease that’s believed to affect 3.2 million Americans.

The drug, Olysio (simeprevir), and others being used to treat the disease are giving patients—including many aging baby boomers—a new lease on life.

In phase II studies, Olysio was shown to clear 90 percent of the virus when paired with Sovaldi (sofosbuvir), a hepatitis drug from Gilead Sciences. The 197 patients in the study had not responded to interferon, the previous standard for treatment.

Earlier this month, the FDA’s Antiviral Drugs Advisory Committee recommended Sovaldi and Olysio for full approval.

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How Olysio Works and Its Side Effects

Olysio is a protease inhibitor. It targets a specific protein and blocks it so that the hepatitis C virus cannot replicate.

The FDA approved Olysio for adults with compensated liver disease (which means that the liver is diseased but still functioning)—both for patients who have not been treated for the disease and for those for whom other treatments have not worked.

While the drugs have proved to be effective during 12 weeks of treatment, about a quarter of patients who were given Olysio in trials developed a rash, and another five percent developed sunburn. Itching and nausea were also reported during treatment.

During five clinical trials involving 2,026 patients, many showed no detectable virus in the blood after 12 weeks of treatment, suggesting that the infection had subsided. 

In a phase III trial for a combination of long-acting interferon, ribavirin, and Olysio, 80 percent of the 393 patients with genotype 1 hepatitis C—which accounts for 70 percent of all hepatitis C cases in the U.S.—were cleared of the virus after 12 weeks of therapy.

Researchers note that Olysio wasn’t as effective against genotype 1a hepatitis C virus with an NS3 Q80K polymorphism, a common strain of the virus in the U.S. Patients with this type of infection should consider alternative therapy.

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Other Therapies Expected Soon

While Gilead’s Sovaldi received FDA advisory committee approval, it has yet to see full approval for market. The European Medicines Agency (EMA) has recommended it for approval for use in the European Union, with a final decision expected in the coming months. The FDA is expected to make its decision on Sovaldi by Dec. 8.

Bristol-Myers Squibb, meanwhile, is currently studying the potential for two other hepatitis C drugs. In one study, a combination of daclatasvir and asunaprevir cured 85 percent of the 220 genotype 1 patients participating in a 12-week phase II trial conducted at Hiroshima University in Japan.

The company says it plans to bring the drugs to the FDA for approval in 2014.