Treatment for Feline Infectious Peritonitis on the Horizon?

A clinical trial of an antiviral drug aimed at naturally occurring feline infectious peritonitis (FIP) in cats is showing promising results, according to a preliminary report. The drug’s effectiveness against experimentally induced FIP was reported earlier this year in an article published in PLoS Pathogens.

In cats with experimentally induced FIP, the drug reversed clinical signs of FIP when given at stages of disease that would have been fatal if left untreated. Eight cats (4 in each of 2 groups) were injected with a cat-passaged serotype of FIP virus. All 8 cats developed lymphopenia, icterus, and ascites. In the second group, antiviral treatment was begun at a more advanced stage of disease than in the first group. Two cats were euthanized because of the severity of their clinical signs. In the other 6 cats, lymphopenia, ascites, fever, and weight loss resolved after 1 week of treatment. The 6 cats were treated for 14 to 20 days and showed no signs of relapse during an 8-month observation period.

The ongoing clinical trial in cats with naturally occurring FIP includes cats with effusive and noneffusive forms of the disease. Final results will not be available until the full report has been published, but the preliminary report indicates that 9 of 13 cats remain in the study (2 cats died before treatment could be started, and 2 cats developed neurologic disease and were euthanized). The drug is not effective in cats with neurologic disease because it does not cross the blood-brain barrier, wrote Niels Pedersen, DVM, PhD, of the University of California-Davis School of Veterinary Medicine, in an email. The study, which is now closed, continues to follow treated cats to monitor for disease recurrence. According to Dr. Pedersen, treatment has resulted in clinical improvement in most cats, although the disease has relapsed in some.

FIP is caused by mutation of the (usually) clinically insignificant feline enteric coronavirus to a more virulent form, the FIP virus. The FIP coronavirus shares features with the coronaviruses that cause severe acute respiratory syndrome and Middle East respiratory syndrome in humans. The drug under investigation targets coronavirus 3C-like protease, a viral protease that is important for virus replication. The authors of the study of experimentally infected cats suggest that the preliminary success of this protease inhibitor in cats with FIP could provide insights into treatment of other coronavirus infections.

Dr. Pedersen notes that the drug is not available outside the clinical trial and is not guaranteed to be commercially marketed. In an email, he writes that his research group has received many requests for treatment that unfortunately must be declined because of the limitations of the trial and the small amount of drug available.