Elanco Announces FDA Approves Improved Zenrelia™ (ilunocitinib tablets) Label, Removing Vaccine-Induced Disease Language

Rhea-AI Summary

Elanco Animal Health (NYSE:ELAN) announced that the FDA has approved important updates to the U.S. Zenrelia label, removing language about vaccine-induced disease risk. Zenrelia, approved in September 2024, is a once-daily oral JAK inhibitor for controlling itching and inflammation in dogs with skin allergies.

The FDA's decision came after evaluating supplemental scientific data, concluding that "the totality of evidence supports removal of the risk of fatal vaccine-induced disease from modified live virus vaccines from the labeling." The medication has treated over half a million dogs globally, with availability in multiple markets including the EU, Great Britain, Brazil, Japan, and the United States.

The label's Boxed Warning still advises discontinuing Zenrelia for 28 days to 3 months before vaccination and withholding it for at least 28 days after vaccination due to inadequate immune response risks.

Positive

• None.

Negative

• Product still requires significant vaccination timing restrictions (28 days to 3 months)
• Cannot be used in dogs under 12 months old
• Risk of inadequate immune response to vaccines remains in boxed warning
• Not evaluated for use with other common treatments like glucocorticoids and cyclosporine

Insights

Veterinary Pharmaceutical Expert

FDA's removal of vaccine-induced disease risk language from Zenrelia's label significantly improves the product's safety profile and marketability.

The FDA's decision to remove the vaccine-induced disease risk warning from Elanco's Zenrelia (ilunocitinib) represents a significant regulatory milestone for this JAK inhibitor treatment for canine allergic dermatitis. This label improvement addresses a key concern that likely hindered initial market adoption following the product's September 2024 approval.

The original warning stemmed from a laboratory study where unvaccinated dogs received three times the recommended dosage during what appears to be a complicated disease outbreak that confounded result interpretation. The FDA's reconsideration based on supplemental data demonstrates the importance of post-approval studies in refining a product's safety profile.

While the Boxed Warning regarding the need to discontinue Zenrelia around vaccination periods (28 days to 3 months prior and at least 28 days after vaccination) remains, removing the more severe language about "fatal vaccine-induced disease" substantially improves the risk-benefit profile communicated to veterinarians and pet owners. This brings the US label closer to the less restrictive labeling in the EU, Great Britain, Brazil, and Japan markets.

The press release strategically highlights peer-reviewed scientific publications supporting Zenrelia's safety and efficacy while emphasizing real-world success with statements about growing adoption rates (80% clinic reorder rate) and treatment of over half a million dogs globally. The company has clearly invested in building scientific evidence to support regulatory improvements and market adoption, with studies specifically addressing the vaccine response concerns.

For Elanco, this label improvement should reduce prescriber hesitancy and improve competitive positioning against other JAK inhibitors in the veterinary dermatology space, particularly oclacitinib, which appears to have been directly compared in clinical studies.

• FDA now concludes "the totality of evidence supports removal of the risk of fatal vaccine-induced disease from modified live virus vaccines from the labeling"ⁱ
• Further evaluation of supplemental scientific data drove this FDA update; data now peer-reviewed and published
• Real-world success and experiences from dermatologists and general practice veterinarians around the U.S. and the world further demonstrate Zenrelia's efficacy

INDIANAPOLIS, Sept. 23, 2025 /PRNewswire/ -- Elanco Animal Health Incorporated (NYSE: ELAN) today announced important updates to the U.S. Zenrelia label, following the Food and Drug Administration (FDA) review of supplemental scientific data.   

Approved by the FDA in September 2024, Zenrelia is an effective, convenient, and safe once-daily oral JAK inhibitor for control of itching and inflammation associated with skin allergies in dogs at least 12 months of age. Over half a million dogs around the world have been treated with Zenrelia. Elanco is inspired by the positive and growing feedback from dermatologists, general practice veterinarians and pet owners.  

At launch, the U.S. Zenrelia label included language based on the outcome of a laboratory study of unvaccinated dogs dosed at three times the label dose of Zenrelia. During that study, an outbreak of concurrent diseases occurred, complicating interpretation of the results.ⁱⁱ

Upon evaluation of additionally submitted data, the FDA now concludes that "the totality of evidence supports removal of the risk of fatal vaccine-induced disease from modified live virus vaccines from the labeling,"ⁱ and this language has subsequently been removed from the Zenrelia label in the U.S. The label Boxed Warning continues to advise discontinuation of Zenrelia for at least 28 days to 3 months prior to vaccination and withholding Zenrelia for at least 28 days after vaccination due to the risk of inadequate immune response to vaccines.

"We appreciate the FDA's commitment to reviewing the latest submitted scientific data to ensure that the label is reflective of the totality of evidence," said Dr. Ellen DeBrabander, Executive Vice President, Research & Development at Elanco. "This now brings the U.S. label a step closer to the approved Zenrelia label in markets such as the European Union, Great Britain, Brazil and Japan. We are committed to generating additional data in our efforts to further strengthen the U.S. label."

Scientific Studies Support Safety and Efficacy of Zenrelia
The totality of the evidence around Zenrelia continues to support the safety and efficacy of the product when used according to label directions. Prior to using this drug, it is important to read the entire label, including the Boxed Warning related to concurrent vaccine administration. Veterinarians can review additional peer reviewed and published studies on Zenrelia.

• Response to primary canine core vaccination in 10-month-old seronegative dogs treated with three times the recommended therapeutic dose of ilunocitinib tablets (Zenrelia), published in BMC Veterinary Research
• Efficacy and field safety of ilunocitinib for the control of allergic dermatitis in client-owned dogs: a multicenter, double-masked, randomised, placebo-controlled clinical trial, published in Veterinary Dermatology
• Efficacy and field safety of ilunocitinib for the control of atopic dermatitis in client-owned dogs: A multicentre, double-masked, randomised, placebo-controlled clinical trial, published in Veterinary Dermatology
• Comparative efficacy and safety of ilunocitinib and oclacitinib for the control of pruritus and associated skin lesions in dogs with atopic dermatitis, published in Veterinary Dermatology

Real-World Success
Zenrelia has achieved remarkable performance across the globe in its first year, with product now available in the European Union, Great Britain, Brazil, Canada, Japan, and the United States. Dogs like Trooper, Scrappy, Remi, Missy, Hunter and River have seen real-world outcomes from Zenrelia. Learn more about their stories here.

"Zenrelia has gained momentum, with more veterinarians buying and prescribing Zenrelia to more dogs each month," said Bobby Modi, Executive Vice President, U.S. Pet Health and Global Digital Transformation at Elanco. "More than 90% of U.S. veterinarians are aware of Zenrelia and 80% of U.S. clinics re-ordered Zenrelia after they experience results first-hand."

Earlier this year, Elanco released the America's Itchy Dogs Report. The first-of-its-kind report includes results from multiple surveys revealing just how badly dogs around the country are itching for relief. Nearly 8 in 10 itchy dog owners who have switched veterinarians report they switched after 3 visits or less.ⁱⁱⁱ This puts more pressure on dermatologists and veterinarians to help dogs find itch relief quickly.

"I've been using Zenrelia in my practice for several months," said Dr. Tannetje Crocker, owner of Alta Vista Animal Hospital in Fort Worth, TX. "With fall allergies in full-swing, I'm using Zenrelia as a first-line treatment option, both in new, as well as seasonal cases. This updated label makes it easier for me to have conversations with pet owners about Zenrelia."

When initiating treatment with Zenrelia, refer to label directions. Zenrelia should only be used in dogs that are up to date on vaccinations, at least 12 months old and free from serious infection.

"As a dermatologist, I tend to see patients that need quick improvement—the owner is likely frustrated, the dog is itchy and inflamed, and I know that I need to help them find relief," Dr. Andrew Rosenberg, veterinarian and President of the American College of Veterinary Dermatology (AVCD). "Zenrelia has become an integral component of my first-line therapeutic approach."

Learn more about Zenrelia at Zenrelia.com.

INDICATIONS
Zenrelia is a prescription medication used to control itching and inflammation associated with skin allergies for dogs over 12 months of age.

IMPORTANT SAFETY INFORMATION
Read the package insert, including the Boxed Warning, before using this drug. For full prescribing information speak with your veterinarian, call 1 888 545 5973 or visit www.elancolabels.com/us/zenrelia.

WARNING: INADEQUATE IMMUNE RESPONSE TO VACCINES. Based on results of the vaccine response study, dogs receiving Zenrelia are at risk of an inadequate immune response to vaccines. Discontinue Zenrelia for at least 28 days to 3 months prior to vaccination and withhold Zenrelia for at least 28 days after vaccination. Dogs should be up to date on vaccinations prior to starting Zenrelia. Do not use in dogs less than 12 months old or dogs with a serious infection. Dogs should be monitored for infections because Zenrelia may increase the chances of developing an infection. Neoplastic conditions (benign and malignant) were observed during clinical studies. The most common side effects were vomiting, diarrhea and tiredness. Zenrelia has not been tested in dogs used for breeding, pregnant, or lactating dogs and has not been evaluated in combination with glucocorticoids, cyclosporine, or other immune suppressive drugs.

ABOUT ELANCO
Elanco Animal Health Incorporated (NYSE: ELAN) is a global leader in animal health dedicated to innovating and delivering products and services to prevent and treat disease in farm animals and pets, creating value for farmers, pet owners, veterinarians, stakeholders and society as a whole. With 70 years of animal health heritage, we are committed to breaking boundaries and going beyond to help our customers improve the health of animals in their care, while also making a meaningful impact on our local and global communities. At Elanco, we are driven by our vision of Food and Companionship Enriching Life and our purpose – all to Go Beyond for Animals, Customers, Society and Our People. Learn more at www.elanco.com.

Investor Contact: Tiffany Kanaga (765) 740-0314 tiffany.kanaga@elancoah.com
Media Contact: Season Solorio (765) 316-0233 season.solorio@elancoah.com 

ⁱ Supplemental FOI Summary
ⁱⁱ Fent, G.M., Despa, S., Gabor, L. et al. Response to primary canine core vaccination in 10-month-old seronegative dogs treated with three times the recommended therapeutic dose of Ilunocitinib tablets (Zenrelia™). BMC Vet Res 21, 461 (2025). https://doi.org/10.1186/s12917-025-04896-5
ⁱⁱⁱ Elanco Animal Health. Data on File.

 

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SOURCE Elanco Animal Health

FAQ

What changes did the FDA approve for Elanco's (NYSE:ELAN) Zenrelia label in September 2025?

The FDA approved the removal of language regarding the risk of fatal vaccine-induced disease from modified live virus vaccines from Zenrelia's label, based on supplemental scientific data evaluation.

How many dogs have been treated with Elanco's Zenrelia since its approval?

Over half a million dogs worldwide have been treated with Zenrelia since its initial approval in September 2024.

What are the vaccination timing requirements for dogs taking Zenrelia?

Dogs must discontinue Zenrelia for 28 days to 3 months before vaccination and withhold it for at least 28 days after vaccination due to the risk of inadequate immune response.

What is the adoption rate of Zenrelia among U.S. veterinarians?

90% of U.S. veterinarians are aware of Zenrelia, and 80% of U.S. clinics have re-ordered the medication after initial use.

What are the main restrictions for using Elanco's Zenrelia in dogs?

Zenrelia can only be used in dogs that are at least 12 months old, up to date on vaccinations, and free from serious infection. It hasn't been evaluated with glucocorticoids, cyclosporine, or other immune suppressive drugs.