In early 2020, as the world struggled to control the COVID-19 pandemic and Dr. Anthony Fauci mentioned remdesivir as a hopeful treatment, an article in The Atlantic described an interesting veterinary connection to that antiviral drug.
It told the story of Davis Niels Pederson, DVM, PhD, professor emeritus of medicine and epidemiology at the University of California-Davis, who had spent decades trying to find a cure for feline infectious peritonitis (FIP). Around 2015, Dr. Pederson had asked a long-time friend, the chief medical officer at the global pharmaceutical company Gilead Sciences, to share some of the company’s antiviral drugs with him as possible treatments for FIP.
Two of the 25 drugs from Gilead Sciences, GS-5734 (remdesivir) and GS-441524 (a metabolite of remdesivir), showed very promising results, with cure rates in both artificially and naturally infected cats between 80% and 100%.
Unfortunately, neither of the two drugs has been approved for use in cats. While remdesivir was pursued as a treatment for severely ill COVID-19 patients, the company did not seek approval for the other molecule as a veterinary drug, fearing that any undesirable effects discovered for that molecule could hinder approval of remdesivir for human use.
With remdesivir conditionally approved for emergency use in humans for the treatment of COVID-19 patients, and no full FDA approval, it cannot be used off-label by veterinarians. As GS-441524 is not approved at all, it cannot be legally used either.
UC-Davis is conducting clinical trials to evaluate GS-441524 and remdesivir in oral formulations to treat FIP. (Previous studies used the injectable versions of the drugs.) While these studies do not guarantee that a drug will be approved for veterinary use, the hope is that one or both will become licensed and FDA-approved for use in cats. Full approval for use in humans would also allow veterinary medicine to utilize the drugs legally in an extra-label fashion.
With no legal means of acquiring these drugs, many veterinarians and cat owners have turned to a Facebook page to purchase the medication from overseas manufacturers. It must be noted that the use of drugs in unmarked vials is not considered safe for many reasons. There is no way to confirm that the vials contain remdesivir. Even if they do contain remdesivir, there is no way to know if the vials also contain other drugs or substances.
By Alex Gochenauer, PharmD, DICVP, FSVHP, FACA