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May 22 (Reuters) - The U.S. Food and Drug Administration said on Friday it approved Gilead Sciences' GILD.O drug for a rare and deadly liver infection that previously had no approved treatment options.

The health regulator cleared Hepcludex to treat chronic hepatitis delta virus, or HDV, a liver disease that affects only people already infected with hepatitis B and can lead to scarring, cancer, organ failure and death.

"Today's approval fills a critical gap in care for patients with chronic HDV infection, who until now have had no FDA-approved therapies available," said Wendy Carter, acting director of the Office of Infectious Diseases in FDA's Center for Drug Evaluation and Research.