By Colin Kellaher

 

Shares of Protagonist Therapeutics Inc. fell more than 60% on Friday after the U.S. Food and Drug Administration placed a clinical hold on studies of rusfertide, the biopharmaceutical company's lead investigational new drug candidate.

The Newark, Calif., company said the hold comes after benign and malignant subcutaneous skin tumors were observed in a transgenic mouse model study designed to detect signals related to tumorigenicity, or the tendency to produce tumors.

Protagonist has been conducting Phase 2 studies of rusfertide in the rare blood cancer polycythemia vera and in hereditary hemochromatosis, a genetic disorder that can cause severe liver disease and other health problems. The company last month had said it expected to advance rusfertide into Phase 3 clinical development in polycythemia vera early next year.

Protagonist on Friday said it was putting dosing of patients in all ongoing clinical trials with rusfertide on hold, and that it plans to work with the FDA in understanding and evaluating the potential clinical risks of rusfertide and determining the next steps for the development of the drug.

Protagonist shares were recently down 59.7%, to $18.57.

 

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

 

(END) Dow Jones Newswires

September 17, 2021 10:33 ET (14:33 GMT)

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