Clinical
FDA approves removal of some vaccine-related warnings for Zenrelia label
The FDA recently approved the removal of a warning about potentially fatal vaccine-related disease from Zenrelia’s label.
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Recently, the U.S. Food and Drug Administration (FDA) approved a label change for Zenrelia (ilunocitinib tablets, Elanco) that removes a warning about the risk of potentially fatal vaccine-induced disease when modified live virus vaccines are administered to patients currently taking Zenrelia. However, other warnings about vaccinating pets who are taking the drug will remain on the label.
Zenrelia is an oral JAK inhibitor indicated for the control of itching and inflammation associated with skin allergies in dogs at least 12 months of age who are up to date on vaccines and free from “serious infection,” according to Elanco. The drug is always dosed once daily, and it was initially approved by the FDA in September of 2024. Elanco stated in their recent press release that over half a million dogs around the world have been treated with this drug since its approval.
From AAHA’s Guidelines
Read more about AAHA’s 2023 Management of Allergic Skin Diseases in Dogs and Cats Guidelines here. The guidelines include summaries of oral medications indicated for the treatment of allergic skin diseases in dogs and can help you choose an appropriate treatment option for your patient.
Zenrelia’s vaccine warning history
At the time of initial FDA approval, the Zenrelia label contained warnings about a risk of vaccine-induced disease based on the findings of a laboratory study in which 10-month-old unvaccinated and seronegative dogs were administered Zenrelia at three times the label dose of the drug. The dogs were given a modified live DAPPV vaccine on days 28 and 60 and a killed rabies vaccine on day 60.
On day 88, serology results indicated that 4 out of the 6 dogs treated with Zenrelia failed to mount an adequate immunologic response to the rabies vaccine they had received, although rabies titers improved for some of the dogs by day 116.
During the study period, some dogs were also diagnosed with Cystoisospora canis infection, which resulted in varying degrees of gastrointestinal disease. Two dogs needed to be euthanized due to the severity of their signs. The dogs with more severe signs were noted to have decreased body condition and reduced CD4 T helper cell counts. Additionally, Canine Adenovirus Type 1 was identified in samples from one dog via PCR at the conclusion of the study.
In their press release, Elanco said that the outbreak of “concurrent disease” complicated the interpretation of the study results, which appears to align with the study investigators’ conclusions that the C. canis infection may have interfered with the dogs’ ability to mount an adequate immune response to vaccination.
FDA’s response
Elanco has since submitted additional safety data to the FDA, who stated in response that “the totality of evidence supports removal of the risk of fatal vaccine-induced disease from modified live virus vaccines from the labeling.”
The boxed warning indicating that dogs receiving Zenrelia may be at risk of an “inadequate immune response to vaccines” will remain on the label. Veterinarians are recommended to discontinue the drug for at least 28 days (and up to 3 months) prior to vaccination and then wait another 28 days after vaccination before resuming administration of Zenrelia.
Zenrelia’s label is different in other countries, including countries in the European Union, Great Britain, Brazil, and Japan. No other countries included the warning about fatal vaccine-induced disease on the label, and warnings about concurrent vaccination and drug administration in some other countries defer to veterinarian discretion.
Ellen DeBrabander, PhD, Executive Vice President, Research & Development at Elanco, indicated that the company hopes additional research will yield a similar result in the United States in the future, saying, “We are committed to generating additional data in our efforts to further strengthen the U.S. label.”
Further reading:
New canine itch medication: Interpreting label claims and warnings
Photo credit: Arvydas Lakacauskas/iStock via Getty Images
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