GS-441524 efficacy for cats with FIP

After the promising results of adenosine nucleoside monophosphate prodrug GS-5734 usage to prevent some RNA viruses, the efficacy of its parent nucleoside GS-441524 against FIP (feline infectious peritonitis) started to be evaluated. This small molecule interferes directly with replicative processes encoded by the virus.
This investigation included 31 cats diagnosed with FIP and without obvious ocular or neurological disease: 26 with effusive FIP and 5 with non-effusive FIP. The patients were taken off all non-essential treatments and the initial dosage regime consisted in a subcutaneous injection of GS-441524 was 2.0 mg/kg, every 24h. The minimum treatment period was twelve weeks, extended in animals that still had abnormal serum protein values. In the later stages of the trial the dosage was increased to 4.0 mg/kg when treatment had to be extended or when disease relapses occurred.
The outcomes of the 26 cats that completed the twelve weeks of treatment (five died or were euthanized in the meantime) was extraordinary. Some examples of clinical responses are the resolution of fever within 12-36 hours and jaundice over 2–4 weeks and the disappearance of abdominal effusions around 10-14 days post-treatment. Eight of the 26 cats suffered disease relapses within 3–84 days. Most of the relapses consisted of fever, anorexia and lack of activity.
At the time of this publication (February 2019), 24 of the studied patients remained healthy. Hence, we could conclude that GS-441524 appears to be an effective and safe option for FIP treatment. The optimum dosage was found to be 4.0 mg/kg SC q24h for at least 12 weeks.

Pedersen, N. C., Perron, M., Bannasch, M., Montgomery, E., Murakami, E., Liepnieks, M., & Liu, H. (2019). Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis. Journal of Feline Medicine and Surgery, 21(4), 271–281. https://doi.org/10.1177/1098612X19825701