Is GS-441524 Safe and Effective for FIP in Cats?

GS-441524 is the antiviral at the core of modern Feline Infectious Peritonitis (FIP) treatment, and the evidence shows it is highly effective when given daily under veterinary supervision. A landmark UC Davis study reported a 92% success rate with GS-441524 in cats that completed treatment (Pedersen et al., 2019). It is generally well tolerated, and the standard course runs 84 days, with safety monitored through regular veterinary checks and bloodwork.

What is GS-441524 and how does it treat FIP?

GS-441524 is a nucleoside analogue antiviral that blocks the feline coronavirus responsible for FIP from replicating. By stopping the virus from copying itself, it gives the cat's body the chance to clear the infection and recover.

FIP was once considered almost universally fatal. GS-441524 changed that, and it is now the proven hero of FIP treatment worldwide.

Since 2019, the CureFIP network has supported more than 100,000 cats treated with GS-441524 based protocols. That scale, combined with published study data, is why GS-441524 is the standard against which all FIP antivirals are measured.

How effective is GS-441524 for FIP?

GS-441524 is highly effective for FIP, with a 92% success rate reported in the UC Davis monotherapy study (Pedersen et al., 2019). That figure applies to cats treated with GS-441524 injectables who completed the full protocol.

Effectiveness depends heavily on starting promptly and finishing the course. FIP can progress quickly, so recognising the early warning signs of FIP and beginning treatment without delay improves the odds.

We are clear about what the data shows and what it does not. The 92% figure reflects cats who completed monotherapy treatment, not every cat who started, and outcomes vary with the form of FIP, how advanced it is, and how consistently the protocol is followed.

A note on dual antiviral therapy

For some cases, particularly relapses or harder to treat presentations, a dual antiviral approach combining GS-441524 with EIDD-1931 is now used. A study by Li and Cheah (2025) reported 78.3% remission in cats that had already relapsed.

These two figures describe different protocols and different patient groups, so they should never be blended or averaged. You can read more about the rationale in our overview of dual antiviral therapy for FIP.

Is GS-441524 safe for cats?

GS-441524 is generally well tolerated in cats, and serious side effects are uncommon when dosing is correct and treatment is supervised by a veterinarian. The most frequently reported issue with the injectable form is discomfort or irritation at the injection site.

Safety is maintained through structured monitoring rather than guesswork. Your veterinarian will weigh your cat, confirm the correct dose for the FIP type, and track recovery with regular bloodwork.

Understanding those lab results helps you see progress and catch problems early. Our guide to cat bloodwork during FIP treatment explains what each value means across the 84-day course.

GS-441524 should always be used under veterinary supervision. Self-managing dosing without professional oversight raises the risk of underdosing, relapse, and avoidable complications.

How is GS-441524 dosed for FIP?

GS-441524 is dosed by body weight and by the form of FIP, given once daily for 84 days (12 weeks). FIP takes four forms, wet, dry, ocular, and neurological, and each shapes the dose your veterinarian will calculate.

The four forms map directly to four dosing levels. Below, each form is explained, followed by the dosing table that mirrors it.

Wet / Effusive FIP

Wet FIP causes fluid to build up in the abdomen or chest, often leading to a swollen belly or laboured breathing. It tends to progress quickly, which makes early treatment important. The CureFIP injectable dose for wet FIP is 6 mg/kg.

Dry / Non-effusive FIP

Dry FIP develops without significant fluid accumulation and can be harder to spot, with signs such as weight loss, fever, and lethargy. It often involves inflammation in internal organs. The injectable dose for dry FIP is 8 mg/kg.

Ocular FIP

Ocular FIP affects the eyes, causing changes such as colour shifts in the iris, cloudiness, or inflammation. Because it can signal involvement beyond the eye, it is dosed higher. The injectable dose for ocular FIP is 10 mg/kg.

Neurological FIP

Neurological FIP affects the brain and spinal cord, with signs such as wobbliness, seizures, or behavioural changes. The antiviral must reach the central nervous system, so it requires the highest dose. The injectable dose for neurological FIP is 10 mg/kg.

FIP form	Injectable dose	Schedule	Duration
Wet / Effusive	6 mg/kg	1 subcutaneous injection per day, 7 days/week	84 days (12 weeks)
Dry / Non-effusive	8 mg/kg	1 subcutaneous injection per day, 7 days/week	84 days (12 weeks)
Ocular	10 mg/kg	1 subcutaneous injection per day, 7 days/week	84 days (12 weeks)
Neurological	10 mg/kg	1 subcutaneous injection per day, 7 days/week	84 days (12 weeks)

Dosing reference: Pedersen et al., UC Davis (PMC6435921). Your veterinarian will confirm the exact dose based on your cat's current weight, which should be rechecked regularly as your cat recovers.

Which GS-441524 product strengths are available?

CureFIP offers GS-441524 injectables in three concentrations, plus oral options for suitable cases. The right choice depends on your cat's weight, the FIP form, and your veterinarian's guidance.

Product	Strength	Volume	Price
CureFIP™ GS-441524 Injectable 20mg/ml	20 mg/ml	8ml, 10ml	€79.00
CureFIP™ GS-441524 Injectable 30mg/ml	30 mg/ml	8ml, 10ml	€89.00
Cure FIP Antiviral 40mg/ml	40 mg/ml	8ml, 10ml	€119.00
CURE FIP™ Dual Antiviral Oral Capsules	GS-441524 + EIDD-1931 (dosed by weight)	n/a	€179.00

Higher concentrations mean a smaller injection volume, which can be more comfortable for larger cats. Prices are shown in EUR exactly as listed and are not converted.

The CURE FIP™ Dual Antiviral Oral Capsules are dosed by weight band: under 2.5 kg uses GS-441524 25 mg + EIDD-1931 5 mg; 2.5 to 5 kg uses GS-441524 35 mg + EIDD-1931 8 mg; and over 5 kg uses GS-441524 50 mg + EIDD-1931 12 mg. The oral dual route is positioned for wet and dry cases, and some regions note it is not recommended once ocular or neurological signs are present or if the cat cannot eat or defecate.

Injectable or oral: which route is better?

Both routes deliver GS-441524, and the best choice depends on the FIP form, the cat's condition, and veterinary advice. Injectables are the form behind the 92% UC Davis success figure and are widely used across all four FIP types.

Route	Best for	Notes
Injectable GS-441524	All four FIP forms, including ocular and neurological	Once daily subcutaneous injection; matched to the 92% UC Davis monotherapy data
CURE FIP™ Dual Antiviral Oral Capsules	Wet and dry cases; relapse scenarios	Not recommended once ocular/neurological signs are present or if the cat cannot eat or defecate

If you are weighing the two, our article on how dual antiviral combination therapy is developing can help you discuss options with your vet. The decision should always be made together with your veterinarian.

How long does GS-441524 treatment take?

A standard GS-441524 course runs 84 days (12 weeks) of daily treatment, followed by a monitoring period. Stopping early is one of the most common reasons for relapse, so completing the full protocol matters even when your cat looks well again.

Recovery usually follows recognisable stages, from early improvement to stabilisation and clearance. Our GS-441524 treatment timeline walks through what to expect week by week.

After the 84 days, many veterinarians recommend an observation window with follow-up bloodwork to confirm remission before treatment is considered complete.

What does GS-441524 treatment cost in the UK?

CureFIP prices are listed in EUR and are not converted, so UK caregivers should budget using the figures shown and discuss total cost with the team. Injectable pricing starts at €79.00 for the CureFIP™ GS-441524 Injectable 20mg/ml.

Total cost depends on your cat's weight, the FIP form, the concentration chosen, and the full 84-day course. Because dosing is weight based, larger cats and higher-dose forms such as ocular and neurological FIP will use more product over the protocol.

We are transparent about protocol length, dosing structure, and cost so you can plan with confidence. For region-specific guidance, our FIP treatment FAQ for Europe covers many of the practical questions caregivers ask.

FAQ

Is GS-441524 effective for all four forms of FIP?

GS-441524 is used to treat all four forms of FIP: wet, dry, ocular, and neurological. The dose increases for ocular and neurological cases, both set at 10 mg/kg for the injectable, so the antiviral can reach the affected tissues. Your veterinarian will confirm the right dose for your cat.

What is the success rate of GS-441524 for FIP?

The UC Davis study reported a 92% success rate with GS-441524 monotherapy in cats that completed treatment (Pedersen et al., 2019). For relapsed cases treated with dual antiviral therapy combining GS-441524 and EIDD-1931, Li and Cheah (2025) reported 78.3% remission. These figures describe different protocols and should not be combined.

Are there side effects with GS-441524?

GS-441524 is generally well tolerated, and the most common issue with the injectable is irritation at the injection site. Regular veterinary checks and bloodwork help catch any concerns early. Always use GS-441524 under veterinary supervision.

How long is the GS-441524 protocol?

The standard GS-441524 protocol is 84 days (12 weeks) of daily treatment, followed by a monitoring period with follow-up bloodwork. Completing the full course is important to reduce the risk of relapse, even if your cat appears recovered earlier.

Can I give GS-441524 without a vet?

No. GS-441524 should always be used under veterinary supervision, because correct dosing by weight and FIP form, plus regular bloodwork, is essential to safe and effective treatment. Your veterinarian also confirms the diagnosis and adjusts the plan as your cat recovers.

If your cat has been diagnosed with FIP, you do not have to navigate the decision alone. Learn more about the available GS-441524 treatment options at CureFIP and talk with our team or your own veterinarian to find the right path for your cat.