Efficacy of a 3C-like protease inhibitor in treating various forms of acquired feline infectious peritonitis

Pedersen, Niels C; Kim, Yunjeong; Liu, Hongwei; Galasiti Kankanamalage, Anushka C; Eckstrand, Chrissy; Groutas, William C; Bannasch, Michael; Meadows, Juliana M; Chang, Kyeong-Ok

Determining a minimal period of treatment was based on progressively increasing treatment times based on favorable response to treatment. The expectation based on experimental studies was that 2 weeks of treatment might be sufficient; hence, that was used as a starting point. However, this study indicated that a minimum treatment period was closer to 12 weeks, which was surprisingly close to the usual 12 week period required to treat humans with HCV using protease inhibitors. 2 However, the treatment period for HCV can vary from 8-24 weeks in different people. Cat CT21 was outwardly healthy, active and growing after 12 weeks of treatment, but total proteins and white blood cell counts had still not returned to normal as they had in the other six cats. Nonetheless, a decision was made to stop treatment after 17 weeks because of the long period of outwardly normal health. Whether treating for a longer period of time would have prevented a disease relapse 13 weeks after stopping treatment is open to conjecture, but it does raise the point of how long treatment is required in some cats. It also raises the question of how long remission must be sustained to declare the disease cured rather than in a sustained remission. The longest disease-free period has been over 11 months at the time of writing, with five other cats free of infection signs for 5-9 months. Based on clinical and histologic evidence of neurologic disease at the time of fatal relapses, it would seem that the virus will eventually reach the brain and that this may be the most important limiting factor in antiviral drug treatment of FIP.