ABCD updates FIP treatment guidance as shorter GS courses gain support
Bottom line
The European Advisory Board on Cat Diseases has updated its feline infectious peritonitis treatment guidance, reflecting how quickly FIP care is changing in practice. The revised recommendations emphasize oral GS-441524 as the most studied antiviral, note success rates that often exceed 90%, and say emerging evidence supports shorter 42-day treatment courses in some cats instead of the long-standing 84-day standard. The update also places remdesivir mainly in a bridge role for severely affected cats that can’t initially take oral medication, and reviews other options, including molnupiravir and nirmatrelvir, where evidence is still more limited. (mdpi.com)
Why it matters: For veterinary professionals, the practical shift is twofold: treatment may be shorter for selected cases, and monitoring is becoming more structured and important. The guidelines recommend reassessing response early, including whether effusions are shrinking after two weeks, and repeating hematology and serum biochemistry during treatment when feasible. They also underscore that access, legality, formulation quality, and cost still vary by country, which means clinicians need to balance evidence-based antiviral use with stewardship and careful case follow-up. (mdpi.com)
What to watch: Expect more discussion around which cats can safely stop at 42 days, how compounded or unregulated products perform, and whether antiviral stewardship concerns begin shaping prescribing norms more explicitly. (mdpi.com)
Key facts
- Guideline group
- European Advisory Board on Cat Diseases (ABCD)
- Topic
- Updated feline infectious peritonitis treatment guidance
- Most studied antiviral
- Oral GS-441524
- Reported success rates
- Often above 90%
- Treatment duration
- 42 days in some cats, instead of 84 days
- Study cited
- Prospective randomized controlled study
- Study finding
- 42 days of oral GS-441524 was as effective as 84 days in some cats
- Best-supported use of remdesivir
- Bridge option for severely affected cats that cannot initially take oral medication
- Monitoring recommendation
- Reassess after two weeks, and repeat hematology and serum biochemistry during treatment when feasible
Feline infectious peritonitis treatment guidance has been updated again, and the headline change is a meaningful one for practice: the European Advisory Board on Cat Diseases now says emerging evidence supports shorter 42-day oral GS-441524 protocols in some cats, rather than defaulting to the historic 84-day course. The update, published in Viruses and mirrored on the ABCD website, also reinforces oral GS-441524 as the most extensively studied antiviral, with treatment success rates often above 90%. (mdpi.com)
That’s a notable evolution for a disease that, until recently, was still widely regarded as fatal. ABCD first published FIP guidance in 2009, then issued a comprehensive revision in 2023. This latest 2026 treatment-focused update reflects how quickly the evidence base is moving as antivirals become more available, more studied, and more integrated into everyday feline practice, even though legal access still differs by market. (abcdcatsvets.org)
The key clinical change comes from newer data on treatment duration. The guideline cites a prospective randomized controlled study showing that 42 days of oral GS-441524 was as effective as 84 days, particularly in cats with effusive FIP, with rapid clinical improvement and 95% survival in that study population. ABCD still frames case selection and monitoring as essential: if effusions haven’t substantially decreased after two weeks, clinicians should consider increasing dosage, revisiting the diagnosis or differentials, and confirming the formulation being used. (mdpi.com)
The document also clarifies how other antivirals fit into the picture. Remdesivir is positioned mainly as an injectable option for cats that are too sick to tolerate oral medication at the outset, with transition to oral therapy as soon as possible. Molnupiravir is discussed as a possible alternative, but ABCD notes its less favorable adverse-effect profile and says GS-441524 should be preferred when available. Nirmatrelvir is mentioned as an emerging option, but the guideline says in vivo and controlled field studies in cats are still needed before recommendations can be made. (mdpi.com)
Outside the guideline itself, one of the clearest themes in expert commentary is stewardship. University of Guelph internist and infectious disease specialist Scott Weese has called GS-441524 a “game changer” for FIP, while also warning that resistance risk shouldn’t be ignored, especially if antivirals are used loosely or for broader feline coronavirus control rather than confirmed FIP cases. That concern doesn’t undercut treatment of true FIP cases, but it does support tighter diagnostic discipline and more thoughtful prescribing. (wormsandgermsblog.com)
Why it matters: For veterinarians, this update is less about a single new drug than about maturation of FIP care into a more standardized, monitor-driven protocol. Shorter treatment could reduce cost, improve adherence for pet parents, and lower the burden of prolonged therapy, especially where access is difficult. But the guidance also makes clear that success depends on product quality, follow-up testing, and early assessment of response. ABCD recommends repeating hematology and serum biochemistry after two weeks and then monthly if possible, while allowing lower-cost monitoring strategies when budgets are tight. (mdpi.com)
The update also lands at a time when formulation quality is getting more scrutiny. The broader guideline notes that antiviral treatment can still be expensive, and some cats have historically been treated with unregulated products. That matters because if clinicians are going to shorten courses safely, confidence in what’s actually being administered becomes even more important. (abcdcatsvets.org)
What to watch: The next phase is likely to focus on refining which FIP presentations are the best candidates for 42-day treatment, expanding data for neurologic and ocular disease, and clarifying the role of alternatives such as molnupiravir when GS-441524 isn’t available. Expect continued attention to stewardship, legal access, and drug-quality questions as FIP treatment moves from breakthrough territory into routine clinical decision-making. (mdpi.com)