Clinical Hold on RAPT Zelnecirnon Studies

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FDA has placed a clinical hold on a RAPT Therapeutics Phase 2b trial of zelnecirnon (RPT193) in atopic dermatitis and a Phase 2a trial in asthma. The action was based on a serious adverse event — liver failure — in one patient in the atopic dermatitis trial, according to the company. The adverse event cause is currently unknown but it has been characterized as potentially related to zelnecirnon, it says, adding that dosing and new patient enrollment has been halted in both trials. It notes that the clinical hold does not apply to RAPT’s ongoing trial of tivumecirnon (FLX475) in oncology.

“A total of approximately 350 patients have been enrolled across three trials evaluating zelnecirnon — the two Phase 2 trials and an earlier Phase 1a/1b study,” RAPT says. “No evidence of liver toxicity has been observed with any other trial participant.  Additionally, no evidence of liver toxicity was observed in nonclinical studies.”

Additionally, the company says it is undertaking a thorough investigation of the case, which involved a patient with a “complex medical history, including a history of drug allergy to dupilumab, autoimmune disease resulting in thyroid hormone replacement therapy and use of an herbal supplement known to be associated with liver failure, as well as a reported Covid-19 infection during the time of the event.”

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