New Treatments For FIP In Cats

Updated November 28, 2020

Feline infectious peritonitis or FIP is probably the number one fatal viral disease of young cats around the world. Up to now FIP has had no effective treatments and no vaccine.

Now there is real hope of a successful treatment. I’ll explain it below after dismissing a few false hopes.

First, if you suspect your cat has FIP, please read my page on the signs and diagnosis of FIP in cats. No cat owner should start a treatment without first confirming the diagnosis. Yes, this really happens!

Treatment Of FIP

Traditional treatment of FIP has been supportive, using good nutrition, anti-inflammatories and attention to secondary infections. However, the most important treatment has been timely euthanasia.

There is nothing worse than watching your young kitten die a slow and relentless death. Up to now, there’s been little we could do about it. This gap has created desperate cat owners, ready to try anything, sometimes at almost any price.

As you will see, some of these treatments are better than others.

Interferon For FIP

Interferon-omega is an injection marketed for cats with FIP. A small early study showed promising results and so for a brief period it became part of the standard treatment. However, that study was plagued by the faults of most early FIP papers.

A larger double-blinded placebo-controlled study found no benefit to interferon. That should have been the end of the matter, but the drug is still available, and people still push the earlier paper without reference to the later one. Like all these drugs, Interferon-omega is expensive.

Polyprenyl Immunostimulant

This is the one that frustrates me. If you read the reports, polyprenyl immunostimulant is a wonder drug. If you read the science with a vet’s eye, it all falls apart. These people almost certainly mean well, but they look a lot like people taking advantage of a bad situation.

The studies they quote lack control groups, have fatal flaws and make very unsound conclusions. It takes a whole webpage just to unpack the deficiencies of this product and its ‘evidence’. Is it any surprise that this is also an expensive drug?

GS-441524 GC-376 and Mutian

GS441524 and GC376 are the two new antiviral drugs responsible for all the recent excitement. And to be fair, they show the greatest promise. There is also an oral antiviral product called ‘Mutian’, whose exact nature is a ‘commercial secret’.

Most of the attention has focused on GS441 as it’s often called. A preliminary paper published last year showed encouraging results in a small study. Perhaps more important than the study itself was that it was in a prestigious journal by a respected author.

But there’s a problem: GS-441 is owned by a human pharmaceutical company whose main focus is developing an antiviral drug for Ebola and human coronavirus. They have allowed this pilot study, and then stopped access to the drug while they focus elsewhere. This has encouraged the production and sale of GS-441 from China.

GC-376, by contrast, is owned by a veterinary company, but still needs FDA approval to be released. This could be up to 5 years away.

Using GS 441 In Cats

NEWS FLASH: before reading on, I strongly urge you to read this update on the use of remdesivir to treat FIP in cats. Now that we have an easily-obtained and legal alternative, there is no longer any reason to continue the black market situation that is described here.

I now have seen many cats treated with GS 441 and heard of a lot more. As a vet, I am in an awkward position of wanting to help, but also being aware of the legal uncertainties.

GS 441 does appear to result in good improvement in most FIP infections, and I have to admit that I would use it if I had a cat with FIP. However, I am still reluctant to talk about it as a “cure”. That’s because, despite my anecdotal experiences, the only scientific evidence so far is one small study of 31 cats.

To anyone reading the compelling stories of improvement during the treatment phase, this must sound like wilful denialism. Maybe it is. I actually think that GS-441 is the best chance we’ve had so far, especially for the wet form. But if we don’t adhere to the scientific method we risk ending up with thalidomide again*.

What To Do If Your Cat Has FIP

If you want to use GS-441, the problem isn’t in getting it, it’s using it. There are Facebook pages and websites devoted to assisting you (‘FIP Warriors’ is mentioned below in the comments), and while they can help you source the medicine, they aren’t vets.

By all means read what they say, but ask your vet for advice on safe dosing. We can’t legally buy or give the drug, but that doesn’t stop us from advising you on how to use it.

Giving a needle is safe and easy once you know how, but I have seen owners get in a terrible mess. GS 441 appears to be hard to inject as well as irritant and painful so a good technique is essential. We’re happy to teach you how and even supply pain relief to give before the needle.

If injections are too difficult, there is a recent oral tablet form that appears to be effective, though at roughly twice the price. Cost is also a barrier to many owners. Recent reports of the cost for a course of GS441 are from $2000 up to $5000 depending on the supplier and the size of cat

In reading owner reports, drug safety doesn’t appear to be a major problem, other than reactions around the injection site. However, there’s no way of guaranteeing it will be as pure or as effective. Buying an unlicensed drug from such origins will always be riskier.

That’s just one of the prices we pay for caring so much. It’s a shame to be given a choice when it’s as imperfect as this one. We can only hope a registered drug fills the void soon, and with the evidence to match.

Further Reading

* I’ve been waiting years to ask you to read the story of Frances Oldham Kelsey. You won’t regret it. The world finds heroes in the most unlikely places.

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 surgery21(4), 271-281. Full text

Have something to add? Comments are welcome below and will appear within 24 hours.
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These help topics are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story! The information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.


15 Replies to “New Treatments For FIP In Cats”

  1. Hi I found 5 kittens in a scrap pile, one already dead others looking very weak starving, pot bellied, full of flea shit,4weeks old approx, so with 24/7over a week they are all OK, but now they are 4mths with intermittent diarrhea when worming and flea treatment, but weighing just 1kg.85 have been postponed desexing till 6mths so they will have a feline aids test, in case the missing feral mum cat died from it, now worried about FiP, as loose bowel movements are a symptom of it, is just a watch and wait situation, any suggestions would be greatly appreciated thanks Janet

    1. Hi Janet. FIP and FIV are the least of these kittens’ problems right now. FIP affects just 1-2% of cats, and mostly comes on much later. FIV is spread via bites from infected cats, so also generally much later. For multiple very young kittens with distended abdomens, think worms or gastrointestinal infections.

  2. Hi! I work at a cat shelter and we have seen more than our share of wet/dry FIP. Cost for GS441 and Remdesivir are not cost friendly, although their benefits seem to be greatly worth it. I have read about an alternative, Mutian. Any thoughts or information on this product? I apologize in advance if questions about this product are not allowed. Any information is greatly appreciated, because the cure for FIP is long overdue 🙂

    1. Hi Christine. Mutian is a unknown quantity, because the manufacturer does not disclose its ingredients. My impression from only a few instances is that it works well, but not quite as well as GS – 441.

  3. I read Dr. Pedersen’s paper. He stated he intended to continue to follow the cats in the study that passed the 84 day post-treatment marker that signaled successful treatment. Do you know if he reported what became of the test cats?

    1. Hi Stephen. It’s a good question. No, I don’t know, but he remains extremely positive about the treatment, so I expect things are well. I can also add that our experience following our own patients is that relapse is unlikely but possible.

  4. Hello , i live in israel how can i get this treatment for my can he has a wet FIP, lungs , he is 6 years old he is my best friend my baby i can lose him

  5. I appreciate your insight on this disease and cures. I am part of a group of pioneers and warriors that are fighting FIP with gs441.
    We are 5000 strong as of today and there are more cats surviving on this than passing. Yes there are some that pass due to how weak the cat was before getting the medication. There are three types available now. One is a pill form and it is doing great also. Good for those who are not comfortable with giving injections. The source of the medication is reliable and it seems to be a saving grace for many!! My cat included. She is on day 24 of injections and she has completely turned around from wasting away and feverish and hardly moving, now back to her playful energetic and bright eyed self. There are many many more as well in this group of 5000 plus. Many of them are post treatment as far as 87 days post and completely turned around with perfect blood work and living a happy cat life. Many people are thankful for the opportunity to save their cat’s life. I wouldn’t just get the medication from anyone or any other source. The group I am in is a reliable source with many Veterinarians on board to look at bloodwork and offer suggestions for support. The entire group is like a family and we support each other and answer questions. Everyone is in various stages of the medication protocol. Everyone shares their ups and downs. New people are finding the group and joining daily! This is the FB group . I only know of one. It is a legitimate source for help. Lots of love and support here. Thank you for your article. I just wanted you to know that we are pioneering our way through this so far the outcomes are positive. We need to educate more veterinarians about this. I changed vets because my former vet scolded me and made me feel bad for seeking out a source to Save my cat rather than watch her die. I read lots of the same stories on my group page. Too many vets are uneducated about the medication and treatment. They make comments like it’s a bad thing or idea. Well what’s worse than watching your beloved cat die!??!! Trying the treatment is the best thing ever!! Because they are dying anyhow!!!!
    Why not try something that just might give them a chance.
    This group is better than any clinical trial because we are living proof that this works and we can follow up and see how it goes through the years.
    Bless any and all that are going through the ravages of this horrible disease. So far I am happy and my cat is doing great and I do not regret my decision to go forward with the medication.
    My new vet is on board with me and they are documenting my progress through this with excitement about the medication and how it’s working.
    Go Warriors!!! And Pioneers!!!!!!

    1. Hi. This sounds encouraging. How can I find more information on tor group? My cat is 2 years old and seems to be in early stages of fip.

      1. The Facebook page referred to by Jaci is called FIP warriors. They will give you advice, but I’m sure they will also strongly recommend you do it with a vet who is comfortable working with the drugs.

  6. Thank you for your balanced and informed perspective on what is a scary and emotive subject for cat owners, especially those like myself with young cats who actively suffer from corona virus flare ups.

  7. Thank you for your article, which I read with considerable interest.
    I have an 8-mths-old foster kitten who’s been diagnosed with dry FIP, after several consultations with our vet and a blood test.
    There is clear evidence of both ocular and neurological damage from this evil disease and he runs a high fever frequently. His appetite has diminished lately as well. It’s a truly heartbreaking experience and unfortunately, this very sweet, loving little boy is not responding favourably to Interferon. He is still being treated with anti-inflammatories and now also eye drops in his right eye, which started to show signs of following the course of his now-blind left eye…the one bright light in all this is that so far, the visible damage to this eye appears static and he can still see me.
    For various logical reasons, other infections were discounted by our vet and from my own research on this subject, I’m inclined to agree with her diagnosis.
    Although I’m no scientist or medic of any kind, I don’t believe that FIP is as rare as you might think, (as I’ve seen quite a few more cases of it among various shelter cats, and of varying ages but more often among kittens), and I can only hope that a reliable treatment (cure!) can be found and offered to us ASAP!
    Kind regards..

    1. Hi Suzanne. I think you are right in saying that FIP can be more common. It seems to vary depending on the prevalence, use and possibly also type of shelters. Here in Adelaide, FIP is quite rare and in fact I’ve not seen it in a moggy (tabby cat) for over 20 years. On the other hand, it appears to be increasingly common in purebreds. I’ve added worldwide prevalence data above to support your comment.

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