Status of FIP treatment and prevention in 2022

Niels C. Pedersen, DVM PhD, November 28, 2022

Original article: Status of FIP treatment in 2022

I am pleased to announce that I have ended my advisory role at SOCKFIP and have officially become a member of the SOCKFIP Board of Directors. It reflects my transition from university to private life, but will not affect my commitment to FIP research. I hope that this more direct involvement will help SOCKFIP transition to a broader role in cat health issues beyond FIP. FIP research continues at the University of California, Davis, as well as at other institutions around the world. Research projects related to FIP at UC Davis are summarized in ” Best regards SOCK FIP” of 2022. SOCKFIP continues to provide financial assistance for such studies through public donations, and I will provide scientific knowledge whenever needed.      

I wish there was a licensed antiviral treatment for FIP in cats, but even the efforts of many individuals and groups have not been able to change the current reality. Therefore, it is questionable whether legal antivirals for FIP will reach the market in the next 2 to 5 years, even if the obstacles are removed immediately. Fortunately, restrictions on the general use of closely related human medicines for COVID-19 are being eased worldwide, allowing them to be prescribed by all doctors and used more widely in the field. Full human approval allows their use in animals, provided the drug needed is derived directly from the actual human product. This would allow drugs made for humans, such as remdesivir and molnupiravir (EIDD-2801), to be used legally in animals, albeit at the cost of human drugs. The goal should still be for drugs specifically licensed for animals and available at a veterinary rather than a medical price. 

More and more veterinarians are already helping owners with treatment. However, it still saddens me that some vets have not heard of effective treatments for FIP, believe that published treatment reports are bogus, or that obtaining drugs from unapproved markets is so scary that they can't even help with treatment once an owner buys it. I commend those veterinarians who accept the reality of treatment and work with owners and their cats with FIP.  

The most significant discovery after GS-441524 is the use of molnupiravir (EIDD-2801) (Merck) as a second effective treatment for FIP. Molnupiravir is also extremely effective in treating cats that have developed resistance to GS-441524, which are the most common cats that develop neurologic FIP during or after treatment with GS-441524. Reports of its use in cats are just beginning to emerge and are being posted on the SOCK FIP website. 

I believe that there are several areas of research that veterinary researchers should consider. One area concerns the safety and efficacy of EIDD-1931 (beta-d-N4-hydroxycytidine), which is the biologically active component of molnupiravir, just as GS-441524 is the active component of remdesivir. This orally administered drug has been the subject of research for almost half a century and should no longer be patent protected. Preliminary research at the University of California, Davis suggests that it may be even more effective and safer than molnupiravir. I also believe that the oral protease inhibitor (nirmatrelvir) component of Paxlovid (Pfizer) should be tested for non-ocular/non-neurological cases of FIP. Nirmatrelvir is broken down into a simple chemical modification of GC373, the active form of GC376. Paxlovid is widely available and can be easily prescribed by both pharmacists and doctors for general treatment of COVID-19. This should make it widely available for use by veterinarians. I also believe that further research should be pursued to find ways to limit FECV infection and to understand the factors that suppress the natural normal protective immunity against FECV mutants. At this point, it is clear that most healthy cats have strong natural and acquired immunity to FIP viruses. What is this immunity and how can this knowledge contribute to strengthening immunity against FIP?