Rapt Therapeutics, Inc. (RAPT) faced a significant setback on Monday, as its stock plummeted over 46% following the company’s decision to terminate its zelnecirnon (RPT193) program. This decision stemmed from a serious adverse event (SAE) involving liver injury, which forced the company to halt two ongoing Phase 2 clinical trials evaluating zelnecirnon for the treatment of asthma and atopic dermatitis (AD).
The trials were placed on FDA clinical hold in February 2024 after a patient in the AD trial experienced liver injury requiring a transplant. While no other trial participants reported liver toxicity or treatment-related SAEs, the company ultimately decided to close both studies before completing enrollment.
Following feedback from the FDA, Rapt Therapeutics made the difficult decision to discontinue the zelnecirnon program. CEO Brian Wong stated, “We plan to continue advancing our next-generation CCR4 compounds with improved safety margins for inflammatory disease and expect to identify a new candidate in the first half of 2025. Additionally, we continue to actively pursue in-licensing opportunities for clinical-stage assets.”
This announcement comes after a period of restructuring for Rapt Therapeutics. In July, the company laid off 47 employees, or approximately 40% of its workforce. The company anticipates completing the cash payments related to this restructuring by the end of the third quarter of 2024.
The sudden termination of the zelnecirnon program and subsequent stock decline underscores the inherent risks associated with drug development. While promising results were initially observed, safety concerns have unfortunately led to the program’s discontinuation. Rapt Therapeutics is now focused on developing safer alternatives, showcasing the company’s commitment to finding effective treatments while prioritizing patient safety.
