RAPT Therapeutics Ends Zelnecirnon Trials After FDA Clinical Hold Over Safety Concerns

RAPT Therapeutics, Inc., a clinical-stage biopharma company specialising in oral minor molecule treatments for inflammatory diseases and cancer, has announced it will discontinue its zelnecirnon (RPT193) program. This decision follows an FDA clinical hold placed in February 2024 on two Phase 2 trials testing zelnecirnon for asthma and atopic dermatitis (AD). 

The trials were halted after a patient in the AD study experienced severe liver injury, ultimately requiring a transplant. No other trial participants reported liver toxicity or treatment-related severe side effects. After recent FDA guidance, RAPT closed both studies early and has chosen to end the zelnecirnon program entirely.

Brian Wong, M.D., Ph.D., President and CEO of RAPT, said in a statement, “In light of the agency’s feedback, we do not see a viable path forward for zelnecirnon, although we continue to believe that CCR4 remains an exciting target with the potential to provide a safe, oral therapeutic option across several inflammatory diseases.”

He also mentioned, “We plan to continue advancing our next-generation CCR4 compounds with improved safety margins for inflammatory disease. We expect to identify a new candidate in the first half of 2025. Additionally, we continue to pursue in-licensing opportunities for clinical-stage assets actively.”