FIP was historically 100% fatal. The discovery that GS-441524 (a nucleoside analog) inhibits feline coronavirus replication has revolutionized treatment—remission rates now approach 80-90% with early intervention. Use the Feline Medicine Specialist for case guidance.
FIP arises from mutation of feline enteric coronavirus (FECV) to a virulent form that replicates in macrophages. Young cats (under 2), multicat households, and stress increase risk. Effusive (wet) FIP: abdominal/thoracic effusion, pyogranulomatous inflammation. Non-effusive (dry) FIP: ocular, neurologic, or abdominal organ involvement.
Definitive diagnosis requires histopathology or immunohistochemistry. Antemortem diagnosis is presumptive: compatible signs + effusion analysis (high protein, low cellularity) + PCR (effusion or tissue) + ruling out other causes.
GS-441524 is the parent drug of remdesivir. It is not FDA-approved for veterinary use but is available through compounding pharmacies and FIP treatment networks. Injectable (subcutaneous) and oral formulations exist.
Typical protocol: 6 mg/kg SC daily for 84 days (effusive); 12 weeks minimum. Oral GS-441524 may be used for maintenance or in cats who cannot tolerate injections. Remdesivir (IV) can be used for initial stabilization in critical cats.
Warning: GS-441524 is not FDA-approved for cats. Treatment is off-label. Work with a veterinarian experienced in FIP treatment. Relapse can occur if treatment is stopped too early.
FIP Warriors and similar networks connect owners with treatment resources and veterinary support. Many cats achieve full remission and normal life expectancy with successful treatment.
- FIP was fatal; GS-441524 has transformed prognosis (80-90% remission).
- Effusive vs dry forms; diagnosis is often presumptive.
- 84-day treatment protocol; injectable or oral formulations.
- Off-label use; work with experienced veterinarian.
- Early treatment improves outcomes significantly.