The FDA had concerns about the preclinical toxicity profile of the drug candidate, BCX5191, the company said.

The drug belongs to a new class of hepatitis C treatments, known as nucs, that is widely expected to be a game-changer in hepatitis C management but has been plagued by safety concerns.

In the past few months, the FDA has placed multiple nucs on clinical holds, citing safety issues, including Bristol-Myers Squibb Co's BMS-986094 and Idenix Pharmaceuticals Inc's IDX19368 and IDX184.

BioCryst said it would conduct additional preclinical studies to determine if low doses of the drug that were not associated with toxicity in animals exhibit meaningful viral load reductions in animals infected with the hepatitis C virus.

The company said it would then determine whether to continue development of the drug, based on the results of the studies.

(Reporting by Esha Dey in Bangalore; Editing by Maju Samuel)

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