# Efficacy of GS-441524 for Feline Infectious Peritonitistis: A Systematic Review (2018-2024)
## 3 Results
### Safety and Adverse Effects  
While efficacy was the primary focus, the included studies also reported on safety. No life-threatening adverse effects of GS-441524 were noted in any study. The most common issue was discomfort at injection sites for subcutaneous administration, which was univer  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Comparison—** & & & & \\
**Efficacy of** & **OR [95\% CI]** & **RR [95\% CI]** & **RD [95\% CI]** & \(p\) Value** \\
**GS-441524** & & & & \\
**Combined with:** & & & & \\ \hline Interferon omega & Not estimable & 1.20 [1.16–1.25] & 0.17 [0.14–0.20] & n.a. a  \\ \hline Remdesivir & 3.55 [0.8–15.0] & 1.14 [1.04–1.23] & 0.11 [0.02–0.18] & 0.0664 \\ \hline GC376 & 3.05 [0.9–10.0] & 1.13 [1.03–1.22] & 0.11 [0.03–0.17] & 0.0542 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Odds ratio, relative risk, and risk difference for the efficacy of GS-441524 in combination therapy compared to GS-441524 monotherapy, with a 95% confidence interval.  
sally reported when injections were used (often manifesting as pain or localized swelling) [11]. Oral GS-441524 was generally well tolerated; mild elevations in liver enzymes and mild lymphocytosis were occasionally observed but did not usually necessitate stopping treatment [26]. One report documented two cats developing urolithts (bladder stones) composed of GS-441524 or its metabolites during treatment--an unusual side effect thought to result from high drug concentrations in urine [27]. Those cases underscore the importance of monitoring during treatment, especially if high doses are used or if the cat has urinary tract symptoms.  
Combination therapy did not appear to introduce significant new safety concerns in the limited cases reported. Remdesivir injections can cause transient renal enzyme elevations and injection-site phlebitis in some cases, but in the FIP studies reviewed, it was used for a relatively short duration and was well tolerated [28]. GC376 is known to cause reversible teeth discoloration in juvenile animals (a concern in lab studies) and occasional injection-site reactions; no severe issues were reported in the FIP cats on GC376, aside from one case of facial skin ulceration that may have been related to the drug or the disease itself [25]. Interferon omega can cause transient fever or malaise, but cats in those combination studies did not have significant adverse reactions reported [29].  
It should be noted that although compounded medication containing GS-441524 is available in some markets, GS-441524 is not legally available everywhere, leading many owners to procure it from unregulated sources. Recent analyses of such black-market products found that some contain incorrect concentrations of GS-441524 or even different antivirals like molnupiravir mislabeled as GS-441524 [30]. Some formulations had very low pH [31], causing severe injection site damage [29]. These findings highlight a broader safety issue: the need for globally available quality-controlled, approved formulations to ensure safe treatment. Globally legalizing and regulating GS-441524 (or its prodrug) for veterinary use would mitigate these risks.