Tolerability of Topical Tocilizumab Eyedrops in Dogs: A Pilot Study

The aim of this study was to examine the tolerability of topical tocilizumab eyedrops in normal dogs and to assess whether this preparation alters tear film cytokine levels or conjunctival cytokine mRNA expression.

Two percent tocilizumab eyedrops were administered to the right eyes and artificial tears to the left eyes of 10 dogs with no anterior segment pathology 3 times daily for 4 weeks. Portable slit-lamp examinations and Schirmer tear testing were performed at baseline and day 1 week 4, as well as 2 weeks after treatment (week 6). Schirmer strips were also used to collect tears for analyses of cytokine levels using multiplex bead array. Median levels of 8 cytokines in the tear film [interferon gamma (IFN-γ), tumor necrosis factor (TNF)-α, interleukin (IL)-1α, IL-1β, IL-2, IL-6, IL-8, and IL-10] were compared among tocilizumab-treated and control eyes. Conjunctival biopsies from both eyes were collected at week 4, and mRNA levels of cytokines were also evaluated. Blood samples were collected at baseline and at the end of treatment to monitor for changes in complete blood count, basic metabolic panel, or liver function tests.

At week 4, conjunctival biopsies and tear samples showed no significant differences in either tear cytokine or mRNA levels for IFN-γ, TNF-α, IL-2, IL-6, IL-8, and IL-10. There was no evidence of local irritation or changes in bloodwork results from the topical tocilizumab formulation.

Topical application of tocilizumab eyedrops was well tolerated when used on healthy dog eyes in this pilot study.