FIP antiviral success brings a new stewardship challenge

Scott Weese is warning the profession not to squander the antivirals that have transformed feline infectious peritonitis, or FIP, from a near-certain fatal diagnosis into a frequently treatable disease. In a March 4, 2025 Worms & Germs post on antiviral resistance in cats, Weese argued that routine GS-441524 treatment for confirmed FIP likely carries a very low population-level resistance risk because the FIP-associated virus is thought to be only rarely transmissible between cats. His bigger concern is broader or poorly targeted use, especially giving GS-441524 to cats with enteric feline coronavirus, where resistant virus could be selected in the gut and then spread through feces across cat populations. That caution lands as updated ABCD FIP guidance continues to position GS-441524 as the typical first-line antiviral and notes that FIP is now often curable with prompt treatment. (wormsandgermsblog.com)

Why it matters: For veterinary professionals, this is a stewardship story as much as a treatment story. The same guidelines that describe GS-441524 as practice-changing also note the growing use of alternatives such as molnupiravir, while recommending GS-441524 preferentially in many cases and reserving some drugs for relapse or non-response scenarios. The practical takeaway is to tighten diagnosis, dose appropriately, avoid casual use against enteric feline coronavirus, and preserve efficacy of a drug class that has fundamentally changed outcomes for cats and pet parents facing FIP. (abcdcatsvets.org)

What to watch: Expect more discussion around antiviral stewardship, resistance monitoring, and when to reserve molnupiravir or other agents for rescue therapy as FIP treatment access expands. (abcdcatsvets.org)