FDA WARNING_LETTER - Elanco US Inc. dba Elanco Animal Health - March 11, 2025

On January 28, 2025, the FDA issued a Warning Letter to Mr. Simmons regarding promotional communications for Zenrelia (ilunocitinib tablets), citing false or misleading claims about its safety and effectiveness. The FDA reviewed the veterinarian product website, consumer-directed website, Product Brochure and Itch Tracker, and a slide deck titled “Reach for Zen: New Relief for Dogs with Atopic Dermatitis.”

Zenrelia, a recently approved JAK inhibitor, is indicated for pruritus and atopic dermatitis in dogs. Its FDA-approved Prescribing Information (PI) includes a boxed warning about the risk of "fatal vaccine-induced disease from modified live virus vaccines and inadequate immune response to any vaccine," requiring discontinuation of Zenrelia for 28 days to 3 months prior to vaccination and 28 days after. The PI also warns of increased susceptibility to opportunistic infections, decreased hematocrit/hemoglobin, and new neoplastic conditions.

The promotional materials misbrand Zenrelia under FD&C Act sections 502(a) and 502(n) by omitting crucial safety information. Specifically, they omit "from modified live virus vaccines" from the boxed warning and replace specific withholding periods (28 days to 3 months prior, 28 days after) with "for a time period before and after vaccination." The veterinarian website's Safety section also lacks mention of fatal vaccine-induced disease, inadequate immune response,