During CYTOPOINT’s conditional licensing period, Zoetis determined that some dogs responded incompletely to a single injection but demonstrated additional improvement after a second or third injection. A clinical study was conducted by Zoetis to assess the effect of additional CYTOPOINT injections in dogs with an initial incomplete response. The study investigators were veterinary dermatologists and the population included client-owned dogs that had confirmed AD and, at the time of entry into the study, had a PVAS score ≥50 mm and were free of ectoparasitic, bacterial, and fungal dermatitis. Candidates could also have diagnostically confirmed but actively managed flea allergic dermatitis in addition to AD.
Dogs in the study were prohibited from receiving potentially confounding medications (eg, glucocorticoids, antihistamines, cyclosporine, other antiinflammatory or immunosuppressant drugs). Limited exceptions were made for dogs receiving long-term therapy indicated to prevent allergic flares or for the treatment of unrelated conditions (eg, carprofen, omega-3 fatty acids, allergen-specific immunotherapy) if the patient had been stable on that medication for a number of months dictated by therapy category (eg, 3 months for incidental illness, 6 weeks for hypoallergenic diet, 8 months for desensitization immunotherapy).
Dogs that had a PVAS of ≥50 mm on the first day of the study (day 0) or ≥36 mm at any subsequent visit received a CYTOPOINT injection and were asked to return 30 days later (±3 days for owner convenience) for a total of up to 4 total visits (days 0, 30, 60, and 90). At each visit, a clinician performed a physical examination and collected the pet owner’s completed PVAS assessment. The PVAS assessment is a validated, easy, and repeatable method for owners to determine the severity of pruritus in their dog. A score is assigned on a sliding scale from 0 (normal dog) to 100 (extremely severe itch), with 20 mm representing very mild/occasional itching, 40 mm mild/frequent itching, and 60 mm moderate/regular episodes of itching.14
Of note, although patients with a 36-mm PVAS were given a CYTOPOINT injection and returned for a repeat visit, a 20-mm reduction in PVAS from the original starting point was considered a treatment success based on initial CYTOPOINT pivotal efficacy studies and subsequent assessment studies.11,13