Protagonist Shares Tumble After FDA Says It May Pull Rusfertide Breakthrough Designation

By Colin Kellaher

Shares of Protagonist Therapeutics Inc. slid nearly 30% in premarket trading Thursday after the biopharmaceutical company warned that it could lose a key U.S. Food and Drug Administration designation for its lead drug candidate.

The Newark, Calif., company said it received a letter from the FDA indicating the agency plans to rescind the breakthrough-therapy designation granted to rusfertide in the rare blood cancer polycythemia vera.

The FDA's breakthrough-therapy designation aims to expedite the development and review of a drug for serious conditions when preliminary clinical evidence shows the drug may show substantial improvement over available therapies.

Protagonist said it has requested a meeting with the FDA and said it believes rusfertide still warrants the designation.

The company said rusfertide's fast-track designation remains active, adding that initiation of a Phase 3 study in polycythemia vera is underway and that it doesn't expect any changes to its development plan or timeline.

Protagonist shares, which closed Wednesday at $25.52, were recently down 29% to $18.12 in premarket trading.

Write to Colin Kellaher at colin.kellaher@wsj.com

(END) Dow Jones Newswires

April 14, 2022 06:34 ET (10:34 GMT)

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