Shares of Gilead Sciences (GILD) fell 14% Friday morning after the drug maker said a majority of patients enrolled in one of its studies experienced a viral relapse within four weeks of completing the 12-week experimental hepatitis C treatment.
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Six of the eight patients that previously had a “null” response but were taking GS-7977 plus the widely used antiviral ribavirin as part of Gilead’s Electron study had a relapse.
Gilead acquired the experimental hepatitis C drug as part of its $11 billion purchase of Pharmasset.
Dr. Norbert Bischofberger, Gilead chief scientific officer, said additional antivirals may be needed to effectively treat the disease.
“We will continue to explore a number of therapeutic approaches to address this significant unmet medical need, including combinations with other oral antivirals,” he said.