Updated ABCD guidelines reshape FIP treatment decisions
Bottom line
The European Advisory Board on Cat Diseases has published updated feline infectious peritonitis treatment guidelines in Viruses, reflecting just how quickly FIP care has changed. The update centers on antiviral use, especially oral GS-441524, and recognizes that for some cats, a 42-day oral course may be as effective as the long-used 84-day protocol. The guidelines also review how remdesivir fits into treatment plans, discuss molnupiravir more cautiously, and reinforce that FIP is now considered a treatable, often curable disease rather than an almost uniformly fatal one. (eprints.gla.ac.uk)
Why it matters: For veterinary professionals, the update gives more practical support for case selection, drug choice, and client communication at a time when legal access, compounded products, and treatment expectations vary widely by market. The shorter-course data could reduce cost, administration burden, and stress for cats and pet parents, but the guideline authors also note that more evidence is still needed in neurologic and ocular cases. The paper further highlights ongoing concerns around variable-quality unlicensed products and the need for careful antiviral stewardship, a point echoed by infectious disease experts warning that misuse could drive resistance and erode one of feline medicine’s most important recent advances. (abcdcatsvets.org)
What to watch: Expect continued debate over which cats are appropriate for 42-day protocols, how therapeutic drug monitoring may shape dosing, and whether more regulated access to GS-441524-class products expands in additional markets. (pmc.ncbi.nlm.nih.gov)
Key facts
- Guideline source
- European Advisory Board on Cat Diseases
- Journal
- Viruses
- Topic
- Updated feline infectious peritonitis treatment guidelines
- Main antiviral focus
- Oral GS-441524
- Short-course option
- 42-day oral course
- Previous default protocol
- 84-day course
- Trial size
- 40 cats with effusive FIP
- Trial result
- 19 of 20 cats survived in each arm
- Remdesivir role
- Injectable option, often used early or when oral absorption is a concern
- Molnupiravir stance
- Reviewed more cautiously, and not suggested as first-line by some authors
Feline infectious peritonitis treatment guidance has been updated again, and the message is clear: FIP care is no longer organized around inevitability, but around antiviral strategy. In a 2026 guideline update published in Viruses, the European Advisory Board on Cat Diseases said oral GS-441524 and related antivirals have fundamentally changed the prognosis for cats with FIP, with the most headline-making shift being support for a shorter 42-day oral treatment option in selected cases. (eprints.gla.ac.uk)
That marks a notable evolution from earlier consensus thinking, when 84 days of treatment was the default standard and euthanasia was still commonly discussed because of the disease’s historically grave prognosis. The new guideline builds on several years of clinical studies showing strong outcomes with GS-441524, remdesivir, and, in some settings, molnupiravir, alongside better diagnostic tools and longer-term follow-up of cats in remission. (abcdcatsvets.org)
The key new detail is the board’s inclusion of a prospective randomized controlled study in which 42 days of oral GS-441524 at 15 mg/kg once daily performed as well as an 84-day course in 40 cats with effusive FIP. In that trial, 19 of 20 cats in each arm survived, and both groups showed rapid clinical and laboratory improvement during follow-up through day 168. The guideline says that finding could ease cost and treatment burden, while also cautioning that more study is needed before assuming the same protocol is reliable across all FIP presentations, especially neurologic and ocular disease. (abcdcatsvets.org)
The document also gives clinicians a more nuanced framework for other antivirals. It describes remdesivir as a prodrug of GS-441524 and notes its role as an injectable option, often used early in treatment or when oral absorption is a concern, before transition to oral therapy. On molnupiravir, the tone is more guarded: the guideline reviews encouraging outcomes in some studies, but notes authors’ suggestions that molnupiravir should not be used as a first-line agent for FIP and points out legal restrictions in some jurisdictions. (abcdcatsvets.org)
Outside the guideline itself, the broader industry conversation is focused on access and stewardship. A dvm360 summary framed the update around the shorter-course option and the expanding antiviral toolkit. Meanwhile, University of Guelph infectious disease specialist Scott Weese has argued that GS-441524 and related drugs should be treated as “highest-tier” anti-infectives, warning that inappropriate use, including for poorly supported off-label indications, could select for resistance and jeopardize long-term success. He notes that cure rates for FIP treatment are now commonly reported above 90%, which raises the stakes for preserving efficacy. (dvm360.com)
Why it matters: For practicing veterinarians, this update is less about a single protocol change than about normalization of FIP treatment as part of everyday feline practice. It gives clinicians stronger footing to discuss prognosis, tailor treatment duration, and weigh oral versus injectable strategies. It also underscores a practical reality in the U.S. and elsewhere: access may still depend on compounded or market-specific pathways, and product consistency remains a live issue. Separate research cited in the guideline and related literature has shown substantial variability in the amount of GS-441524 contained in some unlicensed products, while newer pharmacokinetic work suggests therapeutic drug monitoring may help address inter-cat variability and dose optimization. (abcdcatsvets.org)
For pet parents, that could eventually mean shorter, less expensive treatment in the right cases. For veterinary teams, it means more pressure to identify which cases are truly “the right cases,” monitor response carefully, and avoid casual antiviral use that could create future problems. The guideline’s practical value is that it moves the field closer to evidence-based stratification instead of one-size-fits-all treatment. (abcdcatsvets.org)
What to watch: The next phase will likely center on validation of shorter protocols in non-effusive, neurologic, and ocular FIP, wider use of therapeutic drug monitoring, and continued movement toward more regulated, quality-assured access to GS-441524-class therapies, including compounded pathways such as the Stokes-Bova partnership referenced in the guideline. (pmc.ncbi.nlm.nih.gov)