RAPT Therapeutics Shares Plunge Premarket on FDA Study Hold

By Colin Kellaher

Shares of RAPT Therapeutics plummeted more than 65% in premarket trading Tuesday after a serious adverse event prompted the U.S. Food and Drug Administration to place a clinical hold on a pair of the biopharmaceutical company's studies in inflammatory diseases.

RAPT said the hold involves a Phase 2b study of its zelnecirnon drug candidate in atopic dermatitis, where one patient suffered a serious adverse event of liver failure, as well as a Phase 2a study of zelnecirnon in asthma.

The South San Francisco, Calif., company said that while the cause of the adverse event isn't yet known, it has been characterized as potentially related to zelnecirnon.

Details of the serious adverse event weren't disclosed. According to the FDA's website, serious adverse events are those that can cause disability, are life-threatening, result in hospitalization or death, or are birth defects.

RAPT said it was verbally notified of the hold by the FDA, and that it expects to receive a formal clinical-hold letter from the agency.

RAPT said it is thoroughly investigating the case, adding that the patient involved has a complex medical history, including the use of an herbal supplement known to be associated with liver failure and a reported Covid-19 infection during the time of the event.

RAPT shares, which closed Friday at $25.97, were recently down more than 65% at $9 in premarket trading.

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

(END) Dow Jones Newswires

February 20, 2024 08:57 ET (13:57 GMT)

Copyright (c) 2024 Dow Jones & Company, Inc.