Our own field evaluation demonstrates that dual antiviral oral therapy works, even in cats that had previously relapsed on single-drug Feline Infectious Peritonitis (FIP) treatment.
Our Study, Our Cats, Our Results
At BasmiFIP, we do not just provide Feline Infectious Peritonitis (FIP) treatment. We study it. We track outcomes. We follow up. And we publish what we find, because cat owners and veterinarians deserve to see real data from real cases.
In 2024, researchers Li and Cheah conducted a field evaluation under the BasmiFIP initiative to answer a critical question: can combining GS-441524 and EIDD-1931 in a single oral capsule improve outcomes for cats with Feline Infectious Peritonitis (FIP), particularly those that had already failed previous single-drug treatment?
The answer, supported by data from 46 cats tracked over 180 days, is yes.
What We Did
Between June and September 2024, 46 domestic cats diagnosed with Feline Infectious Peritonitis (FIP) were enrolled in the study. The cohort was deliberately diverse, including all Feline Infectious Peritonitis (FIP) types: wet (effusive), dry (non-effusive), neurological, and ocular. Various breeds and ages were represented. Approximately 90% were indoor-only cats.
Each cat received a standardized oral capsule containing both GS-441524 (at 10-15 mg/kg once daily) and EIDD-1931 (5 mg for cats under 4.5 kg, or 10 mg/kg for cats 4.5 kg and above). The treatment protocol lasted 60 days, with one capsule per 2.5 kg of body weight administered every 24 hours.
This was not a study of easy first-time cases. A significant subset of the enrolled cats had previously relapsed after completing a full course of GS-441524 monotherapy. These are among the most challenging cases in Feline Infectious Peritonitis (FIP) treatment, because the virus has already demonstrated the ability to survive a complete treatment cycle.
Owners tracked daily weight, appetite, clinical signs, and side effects. Veterinary validation was obtained where possible. All cats were followed for 180 days after treatment ended to monitor for relapse.
What We Found
78.3% clinical remission. 36 of the 46 cats achieved full clinical remission after the 60-day dual antiviral protocol. Complete absence of Feline Infectious Peritonitis (FIP) symptoms following treatment.
6.5% relapse rate. Only 3 cats experienced a return of symptoms during the 180-day follow-up. This is notably lower than the approximately 10-11% relapse rate reported in published GS-441524 monotherapy studies, which typically evaluate first-time treatment populations. Achieving a lower relapse rate in a harder population is significant.
10.9% mortality. 5 cats did not survive, primarily those presenting with advanced disease or secondary complications at the time of enrollment. This underscores the importance of starting treatment early, before the disease progresses to a point where even combination therapy may not be enough.
42 of 46 cats showed weight gain and improved appetite. By mid-treatment, 91% of cats had documented weight gain and appetite improvement, verified through individual daily logs maintained by owners. Consistent weight recovery is one of the strongest real-world indicators that antiviral treatment is working.
A:G ratio improved from approximately 0.35 to 0.62. The albumin-to-globulin ratio, a key blood marker used to track Feline Infectious Peritonitis (FIP) disease activity and treatment response, improved steadily throughout the 60-day course. By Day 30, the mean A:G ratio had already risen to approximately 0.45, and by Day 60 it reached 0.62. This progressive normalization demonstrates that the inflammatory response driven by the Feline Infectious Peritonitis (FIP) virus was actively resolving.
Only 2 minor side effects. Two cats experienced minor gastrointestinal issues and brief lethargy during early dosing. Both resolved without intervention. No severe toxicity was observed. No cat had to discontinue treatment due to side effects.
Why These Results Matter for Malaysian Cat Owners
This study proves three important things:
First, dual antiviral therapy works in the real world. This was not a controlled laboratory trial with carefully selected patients. These were real cats, treated by their owners at home, tracked with daily logs, and followed for six months. The 78.3% remission rate and 6.5% relapse rate were achieved in authentic real-world conditions.
Second, the dual protocol can help cats that GS-441524 alone could not. Many cats in this study had already relapsed after monotherapy. The virus in these cats had already shown the ability to survive a full course of GS-441524. The combination of GS-441524's chain termination mechanism with EIDD-1931's lethal mutagenesis provided the additional antiviral pressure needed to overcome resistance that single-drug therapy could not address.
Third, it is safe and practical. A single daily oral capsule with only 2 minor adverse events across 46 cats makes treatment manageable even for first-time cat owners navigating a Feline Infectious Peritonitis (FIP) diagnosis. No injections required. No complex multi-drug dosing schedules. One capsule per day.
Putting the Numbers in Context
The 78.3% remission rate may look lower than the approximately 92% typically reported for first-time GS-441524 monotherapy. But this comparison is misleading because the patient populations are fundamentally different.
The 92% figure comes from studies where cats are receiving antiviral treatment for the first time. The BasmiFIP study deliberately included cats that had already failed previous treatment. Treating drug-resistant Feline Infectious Peritonitis (FIP) is inherently more difficult than treating naive cases, and achieving 78.3% remission in this context is a strong result.
The 6.5% relapse rate is perhaps the most compelling finding. If the dual protocol can keep relapse rates below those seen in first-time monotherapy studies, even in a harder population, it suggests that the two-mechanism approach provides genuinely superior long-term viral suppression.
How the Two Antivirals Work Together
GS-441524 and EIDD-1931 attack the Feline Infectious Peritonitis (FIP) virus through completely different mechanisms.
GS-441524 stops the virus from copying itself by terminating the RNA chain during replication. EIDD-1931 introduces fatal errors into whatever copies the virus does manage to produce, causing the virus to destroy itself through its own defective copies.
When both mechanisms operate at the same time, the virus faces a dual evolutionary challenge. Developing resistance to both chain termination and lethal mutagenesis simultaneously is statistically far less likely than developing resistance to either one alone. This is why the dual protocol showed particular strength in cases where single-drug resistance had already occurred.
Study Limitations
The authors acknowledge that this was an observational field study, not a randomized controlled trial. There was no control group, and outcome data was partly based on owner reports. Pharmacokinetic studies and randomized comparative trials are warranted to further validate these results. However, the real-world setting, diverse patient population, and inclusion of previously relapsed cats make this a valuable and practical contribution to the evidence base.
Read the Full Study
Want to dive deeper into the methodology, data, and clinical analysis? Download or read the complete research paper.
Download Full Study (PDF) | Read Full Study Online
"Enhancing FIP Therapeutic Outcomes: A Field-Based Evaluation of Combined Oral GS-441524 and EIDD-1931 Protocols" by Li, Y. & Cheah, B. (2024). BasmiFIP Initiative.
To learn more about dual antiviral treatment or to consult about your cat's treatment plan, visit basmifip.com or reach the BasmiFIP Malaysia team on WhatsApp.
Free consultations available. Because when every day matters, having the right support makes all the difference.
Reference: Li, Y. & Cheah, B. (2024). Enhancing FIP Therapeutic Outcomes: A Field-Based Evaluation of Combined Oral GS-441524 and EIDD-1931 Protocols. BasmiFIP Initiative.
