Feline Interferon Omega

Mechanism of action

An interferon used as an immune modulator; it is licensed for subcutaneous use in feline immunodeficiency virus therapy (2014 study).

Primary uses

• Dogs and cats (EU and UK veterinary authorisations)
• Studied in canine parvovirus infection and in cats with FIV

Typical dosing

Regulatory status

Approved only for animals. EU: Virbagen Omega (recombinant omega interferon of feline origin) is an authorised veterinary medicine (EMA medicines list, category veterinary). UK: Virbagen Omega 5 MU and 10 MU for dogs and cats are currently authorised (VMD). Drugs@FDA holds no record; not in the US Green Book's active-ingredient list.

Status as of this entry's last review, October 28, 2026. Approvals, compounding rules and sport rules change; the regulatory tracker is checked more often.

What we checked

Feline interferon omega is a veterinary immune-modulating protein; this section records what can be checked.

Identity, computed

A recombinant protein: no formula is given.

Regulatory status, read October 28, 2026

Drugs@FDA: 0 records for “interferon omega”. EMA medicines list: 1 record for “omega interferon”. Run for semaglutide, the same queries return 6 and 5 records (and the registry search 80 trials), so a zero here is an absence, not a broken search. Not named on the WADA 2026 and 2027 Prohibited Lists. As a substance with no current approval for human therapeutic use, it falls under section S0 (non-approved substances), which is prohibited at all times; the lists were read on October 28, 2026.

What the studies show

Beagles with experimental canine parvovirus infection given it intravenously for three days (Ishiwata et al., 1998).

Oral treatment of 11 cats with feline immunodeficiency virus, compared with the licensed subcutaneous protocol (Gil et al., 2014).

Limited efficacy of topical use in cats with acute upper respiratory viral disease (Ballin et al., 2014).

Adjuvant immunotherapy of feline fibrosarcoma (Hampel et al., 2007).

What we looked for and did not find

No human study.

References

1. [other] European Medicines Agency, medicines list (JSON report, downloaded October 28, 2026): Virbagen Omega (recombinant omega interferon of feline origin): category veterinary, authorised.
2. [other] UK Veterinary Medicines Directorate, Product Information Database, currently authorised products searched by active substance, read October 28, 2026: Virbagen Omega 5 MU and 10 MU lyophilisate and solvent for suspension for injection for dogs and cats, active substance interferon omega recombinant feline. https://www.vmd.defra.gov.uk/ProductInformationDatabase/
3. [pubmed] Ishiwata K, et al. "Clinical effects of the recombinant feline interferon-omega on experimental parvovirus infection in beagle dogs." J Vet Med Sci, 1998;60(8):911-7. PMID: 9764403.
4. [clinical-trial] Gil S, et al. "Oral Recombinant Feline Interferon-Omega as an alternative immune modulation therapy in FIV positive cats: clinical and laboratory evaluation." Res Vet Sci, 2014;96(1):79-85. PMID: 24332273.
5. [clinical-trial] Ballin AC, et al. "Limited efficacy of topical recombinant feline interferon-omega for treatment of cats with acute upper respiratory viral disease." Vet J, 2014;202(3):466-70. PMID: 25457261.
6. [clinical-trial] Hampel V, et al. "Adjuvant immunotherapy of feline fibrosarcoma with recombinant feline interferon-omega." J Vet Intern Med, 2007;21(6):1340-6. PMID: 18196745.
7. [other] US FDA, Drugs@FDA (openFDA): no application for interferon omega. Read October 28, 2026.

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