Helping the body fight disease®


Polyprenyl Immunostimulant™ (PI) is USDA licensed in the US for the treatment of Feline Viral Rhinotracheitis (FVR).
VetImmune PI™ is registered in the EU for the treatment of Feline Herpesvirus infection (FHV-1) and Feline Infectious Peritonitis (FIP).


We thank veterinarians and cat owners for sharing their experiences and recommendations so that we continue to improve the performance of Polyprenyl Immunostimulant™. Based on your feedback and data, we learned that the addition of antibiotics markedly increases the success of treatment, especially in chronic URI patients. Therefore, we added and the USDA approved the following recommendation on the label of Polyprenyl Immunostimulant™ to treat feline rhinotracheitis:

“Appropriate concurrent antibiotic use may be needed in the presence of secondary bacterial infections.”

The label change is an important step toward a more robust performance of Polyprenyl Immunostimulant, and we look forward to hearing about your experiences.


Polyprenyl Immunostimulant™ (PI) is  the only therapeutic licensed in the the US by the USDA for the treatment of Feline Viral Rhinotracheitis (FVR). VetImmune PI™ is registered in Czechia (EU) for the treatment of feline herpesvirus (FHV-1) and Feline Infectious Peritonitis (FIP).
Polyprenyl Immunostimulant™ is a safe and effective treatment option that works by upregulating innate immunity and directing cellular immune response. 

polyprenyl Immunostimulant bottles

Viral diseases and the immune system

Immunostimulating (immunomodulatory) medicines are a new, cutting edge development designed to rebuild the damaged immunity and direct it against the invading viruses. In some instances, an antiviral drug may be needed in addition to an immunostimulant drug, but won’t replace it, because suppressing the agent of the disease does not restore the immune system..

how immunity affects how your cat fights off viral diseases like FIP and FVR

Does your cat have FVR?

Feline viral rhinotracheitis (FVR, FRV, FHV-1) is  a common and ubiquitous upper respiratory infection (URI). Polyprenyl Immunostimulant™ is a proven product for the treatment of Feline Rhinotracheitis, designed with cats and their guardians in mind.

polyprenyl immunostimulant for URI FVR feline herpesvirus

FIP Research

Consulting with the USDA, Sass & Sass, Inc. has been designing and is getting ready to conduct a new FIP efficacy study in parallel with the study of Polyprenyl Immunostimulant™ for herpetic ocular disease.

Polyprenyl Immunostimulant for Feline Infectious Peritonitis FIP research


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We bring unique veterinary biologics to the market to improve the health of our companions. ​

FVR Research & TrialsFIP research and Trials


Here’s what people have to say about Polyprenyl Immunostimulant™ for the health of their cats

Our Buddy has WET FIP and your meds have given him a second chance! He’s thriving and if we can help even one other family with their kitty, we are so grateful! Cheers to good health and thriving
Monica M.
Buddy's Mom
Worked well on kitten fosters with URI symptoms. Improved the quality of life of our FIP kittens.
Irene L.
Foster Mom to many
We are so grateful that we've been granted so much extra time with Gidget when we were originally told he would likely die from this disease (as many other kitties have). Today, nearly 4.5 years later, he remains as healthy as can be expected, confirmed with biannual blood work."
dr. Brandy S.
Gidget's Mom
Do-Dam, who lives in South Korea, is a long-term survivor, is doing very well, and her mommy is happy.
Do-Dam's mom

Read more success stories and testimonials from happy cat owners and their cats on our Facebook page.

* Polyprenyl Immunostimulant™ is not or may not be available in a small number of countries due to country-specific regulations or contractual limitations.