Protagonist Therapeutics (PTGX) said late on Wednesday it received a letter from the Food and Drug Administration indicating the regulator's intention to rescind Breakthrough Therapy Designation for its drug candidate rusfertide to treat polycythemia vera, a rare blood disorder.
Shares sank more than 21% in Thursday afternoon trade.
The clinical-stage biopharmaceutical company said it filed a meeting request with the FDA and a briefing document to explain why it "believes rusfertide continues to warrant Breakthrough Therapy Designation."
The FDA letter does not "relate to the rusfertide Fast Track Designation, which remains active," Protagonist said.
The company said initiation of the phase 3 trial of the drug for polycythemia vera is "underway and no changes to the development plan or timeline are anticipated at this stage."
Protagonist also said it expects to release top-line data from the phase 2 trial of drug candidate PN-943 for ulcerative colitis in the first half of Q2 of this year.
Price: 20.14, Change: -5.38, Percent Change: -21.08