While several papers have been published over the last two years about the studies with GC376, we are focusing on the latest one, dated Sept. 13, 2017, and called Efficacy of a 3C-like protease inhibitor in treating various forms of acquired feline infectious peritonitis.

Let's begin by clearly stating that none of the authors of the above-referenced article claim that the GC376 protease inhibitor is the cure for FIP or a drug. At least they don't in writing - not in any published papers and certainly not in such definitive terms. The conclusion of the researchers is clear:

‟Conclusions and relevance: GC376 showed promise in treating cats with certain presentations of FIP and has opened the door to targeted antiviral drug therapy."
The key operative words here are ‟promise" - expressing a potential without certainty of outcome - ‟certain presentations" - meaning restricted, as other presentations are excluded – and ‟open the door" - again, expressing a possibility to be explored. Nowhere is a cure mentioned.


The notion that GC376 is a drug or could be the cure for FIP for all cats is largely the result of misleading stories from various non-academic, FIP-related sources.

Let's take a closer look at the facts as we read the full article instead of attention-grabbing headlines that do not accurately reflect the scope of the study and lead to the general public misconception that a drug or a cure for FIP is right around the corner. It's not. We wish it were, but that is not the case - far from it, in fact. Anyone who tells you that it is, is either lying or doesn't know what he or she is talking about.


This was a non-blinded clinical trial, meaning that in this particular group of cats (20), none were bred for experiment or experimentally infected, unlike in the previous studies. The objective of the study was to ‟evaluate the safety and efficacy of the 3C-like protease inhibitor GC376."


The sample is described as a ‟cohort of client-owned cats with various forms of feline infectious peritonitis (FIP)." However, the selection is rather limited, with a predominance of young cats and cats presenting with the effusive (wet form), or dry to wet rather than dry FIP.

Age at admission:
-Age 3-5 months: 11 cats
-Age 6-12 months: 8 cats
-Age 6.5 years: 1 cat
95% of selected cats were one year old or younger.

FIP Forms:
Wet form: 8 cats
Dry form: 6 cats
Dry to wet: 6 (3 suspected)
70% of selected cats presented either wet or dry to wet forms of FIP.


Cats presenting neurological signs of FIP were excluded from the study. As a reminder, appeals on social media by FIP-related groups and organizations to find candidates for the study specifically asked for kittens under six months of age diagnosed with the acute form of wet FIP. Right from the start, there is a bias in the selection, and this bias is confirmed in the study:

‟This relatively small group of cats allowed...determining the clinical forms of FIP most amenable to treatment."
In plain English, this means tailoring the cats to the treatment instead of tailoring the treatment to the cats. If you have an experimental substance you already know works best in some instances, and you include a majority of cases that fit the parameters of this substance, you are skewing the results to achieve a success rate you would not get if the sample was a direct reflection of the reality of FIP.

In the real world, FIP does not discriminate. We see that every day in our support group. We see wet FIP cases, dry FIP cases, and cats with neurological signs. We see kittens, but we also see cats 2-3 years old and seniors. We don't get to pick and choose, unfortunately. And veterinarians can't treat some cats and ignore others.

Cherry-picking cats for the trial skewed the results and tipped the scales towards an artificially favorable outcome.