Gilead Sciences, Foster City, CA, USA Sch Vet Med, Sch Vet Med, Department of Pathological Microbiology and Immunology, Davis, CA 95616, USA Sch Vet Med, Ctr Compan Anim Hall, 213 CCAH Bldg, 1 Shields Ave, Davis, CA 95616 United States
Purpose The purpose of this study was to determine the safety and efficacy of the nucleoside analog GS-441524 in cats with various forms of naturally acquired feline infectious peritonitis (FIP). Methods Cats ranged in age from 3.4-73 months (mean 13.6 months); 26 had exudative or dry to exudative FIP and 5 had non-exudative disease. Cats with severe neurological and ocular FIP were not recruited. This group started on GS-441524 at a dose of 2.0 mg/kg SC every 24 hours for at least 12 weeks, increasing the dose to 4.0 mg/kg SC every 24 hours when indicated. Results Four of 31 cats with severe disease died or were euthanized within 2–5 days, and the fifth cat died or was euthanized after 26 days. The remaining 26 cats completed the planned 12 weeks or more of treatment. As of press time (OnlineFirst, February 2019), 18 of the 26 cats remained healthy after one round of treatment, while the other eight cats had disease relapse within 3-84 days. Six of the relapses were nonneuropathic and two were neurological. Three of eight relapsed cats were treated again at the same dose, while five cats had their dose increased from 2.0 mg/kg to 4.0 mg/kg every 24 hours. The five cats received a second treatment at a higher dose, and one of the cats, who had a neurological disorder, responded well and remained healthy at the time of publication. However, one of the three cats re-treated at the initial lower dose had a recurrence of neurological disease and was euthanized, while the remaining two cats responded well but relapsed a second time. The two cats were successfully treated a third time at a higher dose, resulting in 25 long-term survivors. One of the 25 successfully treated cats was subsequently euthanized due to possibly unrelated heart disease, while 24 cats remain healthy. Conclusions and Relevance GS-441524 was shown to be a safe and effective treatment for FIP. The optimal dose is 4.0 mg/kg SC every 24 hours for at least 12 weeks.