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Polyprenyl Immunostimulant is the first and only therapeutic for feline rhinotracheitis.

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Oak Ridge, TN

Polyprenyl Immunostimulant is the first and only product used as a therapeutic for symptoms associated with feline rhinotracheitis virus infection. The U.S. Department of Agriculture granted the conditional license for Polyprenyl Immunostimulant USDA “following acceptance of data supporting the product has demonstrated a reasonable expectation of efficacy, is safe under normal conditions of use in field safety trials, and has acceptable purity”. Sass & Sass, Inc. continues to perform additional studies on product efficacy and potency.

Sass & Sass, Inc. is working with university researchers on other applications of Polyprenyl Immunostimulant, including Feline Infectious Peritonitis (FIP) and skin conditions in dogs and cats.

Polyprenyl Immunostimulant is a 2 mg/ml solution of phosphorylated polyprenols.


Safety studies were conducted in 390 cats located in 10 states, from single- and multiple-cat environments. The cats belonged to private owners, rescuers, breeders, or resided in sanctuaries and shelters. The cats’ ages ranged from 2 days up to 17 years, and about half of all cats were pedigreed and belonged to 7 registered breeds. The study showed that oral application of 0.5 mg/kg Polyprenyl Immunostimulant twice daily for 15 days is safe for cats at or above 8 weeks of age. Fewer than 2% of cats may dislike the taste or develop diarrhea.

In a toxicity test with administration of 5 mg/kg (10x experimental) dose of Polyprenyl Immunostimulant to five cats no signs of systemic illness were noted. All cats tolerated the administration well, were normal on physical examination next day.

Sass & Sass, Inc. has been awarded a US patent 6,525,035 "Therapeutic composition and methods", and has another patent application pending.

Sass & Sass, Inc. believes in the ethical treatment of animals in research. No animal in clinical studies should be subject to cruel or painful treatment. All animals on the studies receive symptomatic therapy as needed. Sass & Sass, Inc. believes that study animals should not be euthanised but should be provided a chance through adoption and be treated like any owned pet. Sass & Sass, Inc. does not purposely infect animals with fatal diseases and does not support any research that does. For years, Sass & Sass, Inc. has worked with communities and individuals on adopting out research animals, and many pictures on his site feature ex-participants in clinical trials.