Shares of Gilead Sciences Inc. sank Friday morning after the drugmaker said a promising hepatitis C treatment it recently acquired might need help from other drugs to effectively treat patients with a difficult version of the disease.
The Foster City, Calif., company said some patients in a small portion of a mid-stage study relapsed within a month after completing a treatment that combined the potential drug, labeled GS-7977, and ribavirin, an older drug. Gilead said additional antiviral drugs may have to be added to that combination.
Gilead is studying GS-7977 in hepatitis C patients with genotype 1, the most prevalent subset of the disease in the Western world and the hardest to treat. The patients in this study had already been treated unsuccessfully with the injectable drug interferon.
Hepatitis C is a virus that can lead to life-threatening liver damage and is the main cause of liver transplants in the United States. Analysts expect it to become a bigger health problem as baby boomers age. They say a successful treatment that does not involve interferon, which has tough side effects, could prove lucrative for drugmakers.
Gilead acquired GS-7977 and some other potential treatments in an $11 billion deal for Pharmasset Inc. that closed earlier this year.
Shares of Gilead dropped nearly 14 percent, or $7.65, to $47.16 in Friday morning trading while the Nasdaq exchange fell slightly.
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