# Efficacy of GS-441524 for Feline Infectious Peritonitistis: A Systematic Review (2018-2024)
## 5 Conclusions  
FIP has historically been one of the most dreaded feline diseases, but the advent of antiviral therapy (in particular GS-441524 and its analogues) has dramatically improved the prognosis. This review confirms that GS-441524 is a highly effective treatment for FIP, inducing remission in the majority of cases, including both effusive and non-effusiveforms. The appropriate dosage typically lies in the 4-10 mg/kg range once daily for at least 12 weeks, with higher doses (or more frequent dosing) required for cases with CNS involvement. In our analysis, remission from uncomplicated FIP correlated with lower doses and straightforward protocols, whereas complicated cases (especially neurological FIP) benefit from more aggressive treatment strategies, with combination therapy a promising option. Treatment combinations (GS-441524 with interferon omega, Remdesivir, or GC376) appear safe and potentially helpful for difficult cases, though randomized studies are needed to determine if they provide a significant advantage. Cases that fail initial GS-441524 therapy can often be rescued with Molnupiravir as an alternative antiviral, highlighting the importance of having multiple treatment options available. All evidence indicates that GS-441524 is generally well tolerated by cats. The main side effects to watch for are injection site reactions (largely mitigated by using oral formulations) and, rarely, potential issues like drug-related uroliths. Practitioners should also be aware of the varying quality of black-market products and counsel pet owners on the risks. The global legalization and regulation of FIP antivirals would greatly enhance treatment safety and accessibility and eliminate the ethical quandaries some veterinarians face. In summary, based on the compiled literature, GS-441524 is an effective therapy for FIP, converting a once-hopeless disease into one with a good chance of cure. To fully realize the benefits for all cats, further research (especially controlled clinical trials) is necessary to refine treatment regimens and to validate long-term outcomes. The collective experience so far provides a strong foundation for developing evidence-based treatment guidelines for FIP in the near future. With continued advancements, the goal is to establish FIP as a fully manageable condition, tailoring therapy to each cat's disease presentation and ensuring that every cat with FIP has access to life-saving treatment. Another future consideration is antiviral resistance. Widespread use of a single antiviral could lead to resistant FCoV strains. Monitoring and rotating or combining therapies may become important. It may be prudent to treat the most severe cases with dual therapy from the start to prevent the emergence of resistant variants, analogous to how combination therapy is used in HIV and other viral infections to suppress resistance. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/pathogens14070717/s1](https://www.mdpi.com/article/10.3390/pathogens14070717/s1)]([https://www.mdpi.com/article/10.3390/pathogens14070717/s1](https://www.mdpi.com/article/10.3390/pathogens14070717/s1)), Table S1: Summary of selected published studies reporting treatment outcomes in cats diagnosed with feline infectious peritonitis (FIP). Table S2: Assessment of risk of bias in selected studies on feline infectious peritonitis (FIP) using the Joanna Briggs Institute (JBI) critical appraisal tool. Table S3: Summary of clinical outcomes in cats with feline infectious peritonitis (FIP) treated with GS-441524, remdesivir, and other antivirals, as reported in selected studies. Table S4: Summary of evidence and certainty levels (GRADE) regarding the efficacy of GS-441524-based treatments for feline infectious peritonitis (FIP). Conceptualization, S.A. and E.G. ; methodology, S.A., E.G. and J.F. ; formal analysis, E.G., J.F., M.S.G., H.V. and S.A.; data curation, E.G., J.F., M.S.G., H.V. and S.A.; writing--original draft preparation, E.G., J.F., M.S.G., H.V.