Does Remdesivir work the same as GS-441524 on FIP?

Updated December 2020


1)  Does remdesivir work the same as GS-441524 on FIP?
Has it been tested on FIP cats yet? If so, can you comment if it is an alternative to GS-441524 or not?


Our original research in cats and studies done over the last year in mice, monkeys and humans indicate that Remdesivir is broken down within minutes to GS-441524 and that GS is ultimately the active ingredient. Some early work with cats suffering naturally occurring FIP conducted by others indicates that Remdesivir administered at the same dosage as GS-441524, demonstrates the same rapid improvement in health seen with GS-441524. However, none of these cats, to my knowledge, has successfully completed an 84-day treatment. The prediction is that Remdesivir will be equally effective at curing cats, but until enough cats are treated, it is only a scientific guess. There is also a question of toxicity for Remdesivir. We know that GS-441524 has some kidney toxicity, but it is minimal and has not been a problem. We have not seen liver or other toxicities with GS to date. However, both kidney and liver toxicity has been reported for Remdesivir in humans and there is a caution not to use it in Covid-19 patients that have preexisting renal or hepatic disease.  I suspect that Remdesivir will have an identical safety profile in cats than GS-441524, but this is also a scientific guess until proven otherwise.


2) Now that remdesivir is approved for hospital use, would veterinarians get access to the drug to distribute in their hospitals?  (assuming it is effective against FIP)  Would this access be any time soon?


Veterinarians have always had unofficial approval to prescribe and use human drugs for animals. The only problems come when certain drugs are priced much cheaper for animals than humans and veterinary versions are used in humans in lieu of  human branded equivalents.  This is illegal and may force veterinarians to use the more expensive human version.  However, cats are only a fraction of the size of a human and the usual five day supply of Remdesivir for a Covid-19 patient will suffice for an 84 day treatment in most cats.  This actually puts the cost of Remdesivir for a cat with FIP the same amount as unapproved GS-441524 is currently being priced. Whether sales of Remdesivir will be limited for human use only, at least until current shortages are overcome, is another question. But the presumption is that Remdesivir will be availabel sooner, rather than later, for veterinarians to prescribe to their patients.


3)  Is GC-376 also still considered a effective treatment for FIP, and when do you think it might be available.


GC376 is in the process of being licensed by the FDA but this approval, as I undestand it, may still be two years away. Interestingly, GC376 is now in early stages of testing in humans for Covid-19, and if it proves more effective than Remdesivir, it will be fast-tracked for human approval. GC376 appears to be as effective for younger cats with effusive forms of FIP than GS-441524.  However, it may not be as effective for some cases of dry FIP, and especially those suffering from neurological FIP. 


4) Where is UC Davis FIP research headed from here.  Are there other new or old drugs you’re working on that may show promise against corona virus?


Yes there are other new and old drugs that look promising. Interestingly, one of new ones has a similar mode of action as GS-441524. However, my attempts to study this drug in cats was met with the same type of resistance as Gilead had to granting animal rights for GS-441524. Human pharmaceutical companies, and even their veterinary divisions,  do not want anything  found in animals to interfere with their approval processes for human use. This is strange because FIP appears now to be a highly predictive model for human coronavirus infections.


5) What is your recommended course of treatment for FIP in cats. Is Prednisolone still recommended?  Can a cat take prednisolone and GS-441524 or GC-376 along side at the same time? Do we know if cats have been given the steroid dexamethesone or malaria drug hydroxychloroquine in tests for coronavirus/FIP?


The only drugs tested to date that have cured cats with FIP are GC376 and GS-441524.  Steroids, such as prednisolone or dexamethasone, are anti-inflammatory and provide symptomatic relief, but have no curative powers. They, and other common drugs, should be used to provide temporary support for severely ill cats that need a little time to allow the specific antivirals to work. They should be stopped as soon as a positive therapeutic effect to the specific antivirals is observed, usually within the first few days of treatment.  However, there are occasions during GS-441524 treatment when a low dosage of prednisolone may be needed for several weeks or more to treat complications such as systemic allergic reactions to GS-441524 or other disorders such as feline asthma, eosinophilic granulomas, etc. The quinine derivatives have some antiviral effect in the cell culture but have not been thoroughly tested in cats with FIP.  However, it is doubtful whether they will provide much, if any, benefit.


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