The U.S. Food and Drug Administration has approved Johnson & Johnson's 'Olysio' for treating hepatitis C virus infection, the agency announced Friday.

About 2.7 million to 3.9 million Americans have chronic hepatitis C virus (HCV) infection and the number of infected people is increasing each year. Many people who receive a liver transplant or are on the waiting-list for the procedure have a chronic HCV infection. HCV is a major cause for liver cancer.

The infection often shows no symptoms, which makes it go undetected for many years.

"The FDA approval of OLYSIOTM is an important milestone for people living with chronic hepatitis C as it means that patients have a new treatment option with the potential to cure this challenging disease," said Douglas Dieterich, M.D., Professor of Medicine in the Division of Liver Diseases, Mount Sinai School of Medicine, and OLYSIOTM clinical trial investigator, according to a news release.

Companies that are currently developing new drugs to treat HCV infection include J&J, Medivir, Gilead Sciences Inc. (GILD) and Bristol-Myers Squibb Co. (BMY), Bloomberg reported.

Olysio belongs to a class of drugs called protease inhibitors. The drug, also called simeprevir, blocks a key protein that helps HCV replicate. Olysio will be used along with other antiviral drugs in people with chronic HCV infection and severe liver diseases.

"Olysio is the third FDA-approved protease inhibitor to treat chronic hepatitis C virus infection, and provides health professionals and patients with a new, effective treatment for this serious disease," said Edward Cox, M.D., director of the Office of Antimicrobial Products in the FDA's Center for Drug Evaluation and Research. Olysio is marketed by Janssen Pharmaceuticals, based in Raritan, N.J.

Olysio's safety and efficacy was tested during five clinical trials involving over 2,000 patients. The participants belonged to two groups; those who hadn't had a treatment for the infection before (treatment naïve) or had previous treatment, but relapsed.  Both the groups were randomly given Olysio plus peginterferon-alfa and ribavirin or placebo plus peginterferon-alfa and ribavirin.

Researchers found that 80 percent of treatment naïve participants, receiving a combination of Olysio-antiviral drugs had fewer viruses in the blood after 12 weeks. Meanwhile, only 50 percent of the patients, who were on standard treatment, showed that kind of improvement. The drug was also effective in treating patients whose infection had returned after the first round of antiviral treatment.

However, the drug had reduced fighting ability against 1a hepatitis C virus with an NS3 Q80K polymorphism, a strain commonly found in the United States.

Side effects of using the Olysio with peginterferon-alfa and ribavirin include rashes, itching and nausea. Some patients had to be hospitalized due to severe photosensitivity. FDA said that people should use Olysio in combination with other antiviral drugs and should minimize sun-exposure while using the drug.

The Centers for Disease Control and Prevention (CDC) recommends HCV screening for all baby boomers. According to the agency, a simple blood test called the antibody test can tell if a person has HCV infection.

European regulators on Friday recommended approval of Gilead's drug Sovaldi, according to NBC news.