Study offers clearer guidance on treating ocular FIP

CURRENT BRIEF VERSION: Veterinarians are getting a clearer picture of how ocular feline infectious peritonitis responds to antiviral therapy. A newly published observational case series in the Journal of Veterinary Internal Medicine reviewed 61 cats with FIP seen at the Royal Veterinary College between October 2021 and December 2022 and found ocular involvement in 20 cats, or 33% of cases. Most affected cats were treated with remdesivir initially, often at 15 to 20 mg/kg/day, and all began an 84-day antiviral course. Among the 11 cats with long-term follow-up, 82% had resolution of uveitis, and overall survival in the ocular subgroup was 80%. The study adds needed data for a form of FIP that has historically raised concern because drug penetration into the eye is less certain than in systemic disease. (academic.oup.com)

Why it matters: For veterinary professionals, the report helps support a more confident treatment approach in cats with anterior, posterior, or panuveitis associated with FIP. The authors note that ocular disease was seen in both effusive and non-effusive cases, was bilateral in 70% of affected cats, and was tied to uveitis in all cases reviewed. Clinically, that matters because ocular signs can be the first clue to underlying FIP and may range from anterior chamber changes such as keratic precipitates, iris color change, dyscoria, hyphema, hypopyon, or fibrinous exudate to posterior segment lesions including retinal hemorrhage, vascular tortuosity, retinal detachment, and perivascular cuffing. Higher antiviral dosing has been recommended for ocular and neurologic involvement, and longer courses have traditionally been used because the eye and CNS are harder-to-penetrate sites. In the U.S., this conversation is also more practical than it was two years ago: while there is still no FDA-approved FIP drug, FDA said in May 2024 that it does not intend to enforce approval requirements for patient-specific compounded GS-441524 prescribed by veterinarians under the conditions in Guidance for Industry #256. Broader FIP experience has also pushed reported response rates into the 85% to 90% range in treated populations, even as diagnosis in practice often remains presumptive rather than definitive. (academic.oup.com)

What to watch: Expect more discussion around dosing, duration, and case selection for ocular and mixed ocular-neurologic FIP as additional case series and real-world prescribing experience accumulate. A related line of work is now looking at whether higher induction dosing and objective markers such as serum amyloid A, alpha-1 acid glycoprotein, and albumin:globulin ratio trends could help guide safer treatment duration decisions. (academic.oup.com)