Ocular FIP treatment moves from theory to practical care

CURRENT BRIEF VERSION: Ocular FIP is getting a more practical treatment framework as veterinary education outlets spotlight newer evidence on antiviral use, especially GS-441524 and remdesivir, for cats with eye involvement. The VetGirl podcast “Ocular FIP – A New Vision for Treatment” centers on how treatment expectations have changed as more data accumulate for antiviral therapy in feline infectious peritonitis, including the reality that ocular and neurologic cases often need higher dosing than uncomplicated disease because the eye and CNS are harder-to-penetrate sites. It also underscores that ocular disease may be the dominant presentation in some cats, with signs such as uveitis, keratic precipitates, iris color change, dyscoria or anisocoria, hyphema, hypopyon, fibrinous exudate, retinal lesions, hemorrhage, vascular tortuosity, retinal detachment, or perivascular cuffing. That discussion lands in a very different clinical environment than even two years ago: in the U.S., the FDA said in May 2024 that it does not intend to enforce approval requirements for compounded GS-441524 prescribed by veterinarians for individual cats with FIP under specific conditions, and compounded oral GS-441524 became available through U.S. pharmacy channels in June 2024. (fda.gov)

Why it matters: For veterinary professionals, ocular FIP is no longer a near-hopeless diagnosis managed mostly with supportive care and guarded conversations. Published evidence now supports antiviral treatment as a realistic option, but ocular disease remains a higher-complexity presentation because drug penetration into the eye is more limited, treatment protocols are still evolving, and relapse risk is a practical concern. A 2024 systematic review found the best outcomes with GS-441524 generally in the 5–10 mg/kg range, adjusted upward for severity and for neurologic or ocular signs, while a JVIM case series reported that cats with ocular or neurologic FIP were started at 15–20 mg/kg daily because of blood-eye and blood-brain barrier limitations; in that series, 4 of 6 cats with ocular involvement recovered fully. Recent feline guidance also supports using remdesivir up front in very sick cats, then transitioning to oral GS-441524 once they can be medicated reliably. VetGirl’s broader FIP coverage also highlights that response rates in practice are now often cited around 85% to 90%, and that clinicians are increasingly using more structured monitoring rather than relying only on how quickly cats seem to feel better in the first week of treatment. (pmc.ncbi.nlm.nih.gov)

What to watch: Expect continued refinement of dose, duration, and rescue protocols for ocular and neurologic FIP, along with more formal guidance as compounded antiviral access expands and more outcome data are published. One active area is whether higher-dose induction and objective stopping criteria — including trends in serum amyloid A, alpha-1 acid glycoprotein, and the albumin:globulin ratio — can help shorten treatment safely in some cats without undertreating harder-to-clear ocular or CNS disease. (catvets.com)