A novel oral prodrug (CK301) for effusive feline infectious peritonitis: An open-label study evaluating dose optimization and therapeutic efficacy.

Feline infectious peritonitis (FIP) is a fatal, immune-mediated disease caused by feline coronavirus (FCoV). Although several antiviral therapies have been validated for FIP treatment, safer and more cost-effective options are still needed. CK301, a novel nucleoside analog, may represent a practical alternative to current therapies. This study evaluated the efficacy and safety of CK301 in cats with effusive FIP. In this open-label trial, 150 cats with naturally occurring effusive FIP were randomly assigned to receive oral CK301 tablets (Patent WO2023197791) at low, medium, or high doses; placebo; or subcutaneous GS-441524. Treatment outcomes were assessed based on survival, clinical improvement, viral clearance, and adverse events. After 56 days of treatment, medium- and high-dose CK301 demonstrated clinical outcomes and survival comparable to those of GS-441524. However, high-dose CK301 was associated with an increased risk of drug-induced liver injury. Subcutaneous GS-441524 was associated with injection-site reactions, including ulceration, crusting, and subcutaneous masses, whereas oral CK301 avoided these complications. In conclusion, medium-dose oral CK301 (12.5 mg/kg) significantly prolonged survival, highlighting its potential as a therapeutic option for effusive FIP. It offers a convenient, non-invasive alternative to injectable treatments, provided liver function is closely monitored for potential transaminase elevations.