A new clinical trial has led to a stunning breakthrough in the treatment of feline Infectious Peritonitis (FIP), a lethal feline viral disease that has historically been considered untreatable.

FIP is almost always fatal.

But researchers from Kansas State University and University of California, Davis, have discovered that treating FIP using a novel antiviral drug that could cure or greatly extend the lifespan of cats with FIP.

The team launched their clinical trials in March 2016, and published the results in the November 2017 issue of the Journal of Feline Medicine and Surgery.

Researchers conducted the trial with 20 cats that presented with various forms and stages of FIP. There are two forms of FIP: wet, or effusive; and dry, or noneffusive. In the wet form of FIP, fluids accumulate in body cavities like the abdomen and chest, causing abnormal swelling and/or difficulty breathing. In the dry form, lesions erupt throughout the cat’s body, including the eyes, kidneys, and nervous system.

The cats accepted into the trial ranged in age from 3.3 to 82 months, with a mean age of 10.4 months. The disease most frequently affects cats under two years of age, although cats of any age can get it. Fourteen of the cats presented with wet or dry-to-wet FIP and six with dry FIP. All were treated with an anti-viral drug called GC376. Originally developed in 2011 by scientists looking for a cure for the Norwalk virus, which causes gastrointestinal illnesses in humans, GC376 was found to be effective against a broad spectrum of viruses, including the coronavirus family, one of which causes FIP. All 20 cats in the trial were administered doses of GC376 subcutaneously every 12 hours.

The initial results were promising. Nineteen of the 20 cats regained outward health within two weeks of initial treatment. However, signs of the disease reappeared one to seven weeks after the primary treatment. Relapses were treated for a minimum of 12 weeks.

Relapses that no longer responded to treatment occurred in 13 of the 19 cats originally administered GC376. Severe neurologic disease occurred in 8 of the 13 cats that failed treatment. Five cats had recurrences of abdominal lesions.

At the time of publication, seven of the cats were still in remission from FIP.

Niels Pedersen, DVM, PhD, and a longtime FIP researcher who led the trial at the University of California, Davis, said, “This research is the first attempt to use modern antiviral strategies to cure a fatal, systemic viral disease of any veterinary species.”

Yunjeong Kim, DVM, PhD, and in charge of the trial at Kansas State University, said, "We found that most cats, except for those with neurological disease, can be put into clinical remission quickly with antiviral treatment, but achieving long-term remission is challenging with chronic cases. These findings give us more insight into FIP pathogenesis and also underscores the importance of early diagnosis and early treatment."

Although FIP affects only a small percentage of cats—fatal FIP occurs in one in 5,000 cats in households with one or two cats, and up to 5 percent of cats in multicat households and shelters die from FIP—the disease is devastating. GC376 presents the first real hope of an eventual cure that researchers have found.

And those seven cats still in remission represent a remarkable breakthrough.

Pedersen added, “Saving or improving the lives of even a few cats is a huge win for FIP research.”

Photo credit: (c) iStock/Bill Oxford