By Kim Campbell Thornton · Elanco Allergic skin disease is one of the most common reasons clients bring pets to veterinarians. The discomfort and distress caused by itchy skin affect not only the individual dog but also lead to stress for human family members, who are concerned about and disturbed by the constant itch-scratch cycle. Reducing pruritis is critical to enhancing quality of life for both patients and their people, hence the ongoing search for effective treatments. Ilunocitinib, a recently FDA-approved Janus kinase inhibitor, gave a powerful performance in a head-to-head match-up with Apoquel®. Efficacy and safety were measured in a randomized double-blind non-inferiority study published in January in the peer-reviewed journal Veterinary Dermatology. In four countries with diverse climates, 338 client-owned dogs diagnosed with atopic dermatitis at 25 veterinary clinics participated in the study. Owners assessed their dogs’ condition throughout the study using the pruritis visual analog scale of 0 (normal) to 10 (extreme itching) to measure improvements in severity of itching, scratching, biting, licking, chewing, nibbling and rubbing. Once-daily dosing of ilunocitinib rapidly controlled itch and avoided rebound itch, unlike the competing product, which was given twice daily for the first 14 days. With both treatments, PVAS scores dropped rapidly over the first seven days of treatment and continued to improve up to day 14. There was a slight rise in mean PVAS after Apoquel dosing was decreased from twice daily to once daily, whereas dogs receiving once-daily Zenrelia continued to demonstrate improvement in PVAS. Veterinarians who have recommended ilunocitinib for patients with skin allergies have been pleased with the results. Tom Lewis, DVM, DACVD, is founder of Dermatology for Animals, a group of clinics specializing in caring for pets with allergies. He has had patients respond well to ilunocitinib. "Seeing these dogs get back to normal levels of itch and seeing the bond restored between the dog and pet parents is incredibly rewarding,” he says. Dr. Lewis’s patients include Trooper, a four-year-old Yorkshire Terrier, and Scrappy, a 9-year-old Yorkshire Terrier-Chihuahua mix. Trooper participated in Zenrelia’s clinical trial and returned to a normal level of itch while on the medication. When the trial concluded, the itch returned, so now that the treatment is widely available, his owner, Robin, is excited to have him back on it. “Having a solution for his allergies is such a relief,” she says. “It makes my heart happy that I will be able to afford it and give him the relief he deserves.” Scrappy’s itch was so severe that he lost a significant amount of fur and no longer enjoyed playing or going for walks. At night, his constant scratching meant that no one got a good night’s rest. His owner, Lisa, tried numerous treatments, but they never completely controlled Scrappy’s itchiness. Zenrelia rapidly provided itch relief, and after eight weeks his coat was back to normal, he was taking long walks, and he was happy again. Buckaroo, an eight-year-old mixed breed from Texas, received steroids, immunotherapy and other treatments with no relief from his itchy skin. His veterinarian suggested ilunocitinib, and Buckaroo’s owner began to see improvement within three weeks. By eight weeks, he was again a happy, active dog, she reported. The response to ilunocitinib by Trooper, Scrappy and Buckaroo was comparable to that seen in the study. See the chart above for more details about efficacy. After a review of the head-to-head data, which results would you prefer to see in your patients? Buckaroo before Zenrelia (left); Buckaroo after Zenrelia treatment (middle and right) The outcomes demonstrated similar adverse event rates in a head-to-head clinical trial in client-owned dogs with atopic dermatitis. Zenrelia has a boxed warning related to vaccine-induced disease and inadequate immune response to vaccines. Read package insert before prescribing. Ilunocitinib benefits at a glance: Because dogs are individuals, not all of them respond the same way to medications. Ilunocitinib is a great choice to stock alongside current options to meet the needs of individual patients. It works rapidly to reduce pruritis, disrupting the itch-scratch cycle, reducing damage to the skin caused by scratching and allowing it to heal. Ilunocitinib is a non-selective JAK inhibitor that inhibits the function of a variety of pruritogenic, pro-inflammatory, and allergy-related cytokines that are dependent upon JAK enzymes. The single daily oral dose makes it both convenient and cost-effective1 for clients to give. The competitor product must be given twice daily for the first two weeks. In testimonials, owners express relief about their dogs’ reduced itchiness, improved skin condition, and greater comfort and activity level. Zenrelia, Elanco and the diagonal bar logo are trademarks of Elanco or its affiliates. ©2025 Elanco or its affiliates. PM-US-25-0484 References Forster S, Boegel A, Despa S, et al. Comparative efficacy and safety of ilunocitinib and oclacitinib for the control of pruritus and associated skin lesions in dogs with atopic dermatitis. Veterinary Dermatology. 2025; 1–10 Olivry T, et al. A randomized controlled trial testing the rebound-preventing benefit of four days of prednisolone during the induction of oclacitinib therapy in dogs with atopic dermatitis. Vet Dermatol, 2023; 34: 99-106.
