Niels C. Pedersen, DVM PhD
Dear Professor Emeritus
School of Veterinary Medicine
University of California, Davis

6/18/2019, Translation 4/23/2021

Many entities, mainly in China, produce GS-441524 (GS) and GC374 (GC) intended mainly for desperate owners of cats with FIP. Some of these products come from non-veterinarians, while some are synthesized with the direct or indirect involvement of people with veterinary or human medical education. People in China have a big problem with FIP because of their growing ability to keep pets. There is a particularly high demand for expensive kittens with pedigrees, which are at increased risk of FIP. Therefore, the Chinese interest in drugs such as GS-441524 (GS) and G376 (GC) is not entirely financial and opportunistic. Although their first efforts were focused on GC, the emphasis of this black market quickly shifted to GS. Although this type of marketing and use of GS and GC is technically illegal, the companies holding the GC and GS patents have no effective means of stopping this black market. Reputable pharmaceutical companies offering GS and GC usually use a disclaimer limiting their use to research purposes only and not to human or veterinary treatment. This disclaimer, if issued, has no legal weight for law enforcement against the owners and is largely ignored. Medicines offered by individuals are often packaged and labeled as nutritional supplements, making it easier for customs to pass through customs in other countries. Fortunately, this mislabeled drug usually contains accurate information about the drug concentration, for example 15 or 16.5 mg / ml. The recommended GS dose for cats with non-neurological FIP is 4 mg / kg, SC once daily, for 12 weeks. Cats with neurological FIP may require a gradually higher dose of 5-10 mg / kg.

Veterinarians, who are more bound by legal and ethical restrictions, may look at the black market in a completely different way than owners of cats suffering from FIP. Some may refuse to participate beyond the initial diagnosis of FIP, others may assist in administering and monitoring treatment if cat owners provide medication, and some may require signing exemptions that relieve them of any legal or ethical obligations. I respect any procedure that veterinarians may use in interpreting their personal oaths to "use their scientific knowledge and skills for the benefit of society through the protection of animal health and welfare, the prevention and alleviation of animal suffering, the protection of animal resources, the promotion of public health and progress. in medicine. "

We already know about the problems of black market drugs in human medicine. Although suppliers declare high purity, biological activities (ie antiviral effect) are not tested. We already know that GC and GS produce more and more individuals and that quality in mg / kg or molar dosage may vary. We also know that the price of GC and GS can also vary widely and that owners can expect to pay thousands of dollars for enough medicine to complete treatment.

Buying enough medicine and fast enough to help you is just the first step. The drug can be purchased in powder form, which requires more than average knowledge for successful conversion to a stable and injectable form. In response to this problem, most suppliers offer GC or GS in pre-form. The oral form GS-441524 has recently started to be produced in China and is starting to appear on the market. Chemical modifications for oral absorption are well known in the development of drugs for HIV / AIDS and HCV. However, owners and veterinarians who buy GS or GC on the black market, usually at a very high price, would normally expect from the supplier some information on biological (antiviral) activity on a molar basis, diluent used and information on storage conditions and shelf life. If the antiviral activity is the same as for the drugs described in the research publications, the published information can be used directly. If this is not the case, the published information will not be applied. Remember to be very careful in such situations.

Information on where and how to get GC376 and GS-441524 can be easily found on social websites. This website was developed from groups of cat owners who have personal experience with the FIP and are familiar with the black market. Although Chinese retailers provide advice on the FIP and how these drugs are used, many claim to have veterinary contacts, and groups of cat owners are much more helpful. We now know that hundreds, if not thousands, of cats around the world are currently being successfully treated with FIP using drugs obtained on the black market. These favorable reactions appear to confirm our own published research on both GC376 and GS-441524. Owning groups have become very adept at identifying the most biologically active and economical GC and GS resources based on personal experience.

It is also very important that the diagnosis of FIP be as accurate as possible, as the disease is still often misdiagnosed. We therefore hope that owners have access to the veterinary expertise needed to properly diagnose FIP and monitor treatment with this level of emotional involvement, duration, cost, and monitoring. Information on how to administer these medicines has been provided in the form of published scientific publications listed in our supplement on "treatment of FIP". There is still a lack of knowledge on how to properly treat cats with neurological and ocular / neurological forms of FIP. GC and GS penetrate the brain with some difficulty, which is explained in the second appendix on neurological FIP. The only way to increase the level of the drug in the brain is to increase the level in the blood using higher and higher dosing regimens. It has been shown that higher doses, especially in GS, can lead to complete or almost complete remission of clinical symptoms. However, it is still uncertain whether every cat with neurological FIP can be cured. For this reason, cats with FIP with neurological disabilities should be treated much more cautiously than other forms of FIP. We are also aware of the potential problem of drug resistance, which is present either at the start of treatment or which develops during treatment. We observed primary drug resistance in 1 of 20 GC376-treated cats and 1 of 31 GS-441524-treated cats. Therefore, drug resistance should always be considered in any cat that does not respond rapidly to initial treatment or has relapsed after a period of positive response. Although this has not been adequately investigated, it is reasonable to assume that resistance to one drug will not apply to other drugs, as their mechanisms of virus inhibition are completely different.

I will continue to give the best possible advice to owners and veterinarians who use or are considering the use of GS and GC from the black market in the treatment of cats with FIP. Fortunately, extremely active and knowledgeable owner groups have emerged in several countries, serving as the main channel between GS and GC owners and suppliers. These groups are active in social media forums and desperate owners have relatively easy access to them and receive timely and critical assistance.

I must make it clear that I would have preferred these medicines to be approved and commercially available in the usual way. I am sure that will happen in the next few years, and if it does, black market demand for drugs like GS and GC will fall. In the meantime, UC Davis will continue to research new antiviral drugs for diseases such as FIP and share our findings in a conventional manner in peer-reviewed scientific publications. It is our sole responsibility to assure owners and veterinarians that our published findings are accurate, reproducible and applicable.