Rapt Therapeutics said on Tuesday the U.S. FDA had placed on hold two mid-stage trials of the company's drug to treat eczema and asthma, after liver failure was observed in one of the patients. Shares of the San Francisco-based company plummeted 66% to $8.92 in premarket trading. Stifel analyst Alex Thompson said the clinical hold "represents a major setback" for the company and could result in "a meaningful delay in trial timelines". Rapt had enrolled about 350 patients across the two mid-stage trials and a previous early-stage study of the drug, zelnecirnon, but no evidence of liver toxicity was observed with any other patient. The company said in November it was expecting to report results of the trial in patients with atopic dermatitis, or eczema, in mid-2024, while it was making progress on enrollment in its asthma study. Following the hold, Rapt will halt dosing of existing patients and stop enrollment of new participants, while it conducts a thorough investigation of the case.
