A Low Concentration of Tacrolimus/Semifluorinated Alkane (SFA) Eyedrop Suppresses Intraocular Inflammation in Experimental Models of Uveitis

PURPOSE Corticosteroids remain the mainstay therapy for uveitis, a major cause of blindness in the working age population. However, a substantial number of patients cannot benefit from the therapy due to steroids resistance or intolerance. Tacrolimus has been used to treat refractory uveitis through systemic administration. The aim of this study was to evaluate the therapeutic potential of 0.03% tacrolimus eyedrop in mouse models of uveitis. METHODS 0.03% tacrolimus in perfluorobutylpentane (F4H5) (0.03% Tacrolimus/SFA) was formulated using a previously published protocol. Tacrolimus suspended in PBS (0.03% Tacrolimus/PBS) was used as a control. In addition, 0.1% dexamethasone (0.1% DXM) was used as a standard therapy control. Endotoxin-induced uveitis (EIU) and experimental autoimmune uveoretinitis (EAU) were induced in adult C57BL/6 mice using protocols described previously. Mice were treated with eyedrops three times/day immediately after EIU induction for 48 h or from day 14 to day 25 post-immunization (for EAU). Clinical and histological examinations were conducted at the end of the experiment. Pharmacokinetics study was conducted in mice with and without EIU. At different times after eyedrop treatment, ocular tissues were collected for tacrolimus measurement. RESULTS The 0.03% Tacrolimus/SFA eyedrop treatment reduced the clinical scores and histological scores of intraocular inflammation in both EIU and EAU to the levels similar to 0.1% DXM eyedrop treatment. The 0.03% Tacrolimus/PBS did not show any suppressive effect in EIU and EAU. Pharmacokinetic studies showed that 15 min after topical administration of 0.03% Tacrolimus/SFA, low levels of tacrolimus were detected in the retina (48 ng/g tissue) and vitreous (2.5 ng/ml) in normal mouse eyes, and the levels were significantly higher in EIU eyes (102 ng/g tissue in the retina and 24 ng/ml in the vitreous). Tacrolimus remained detectable in intraocular tissues of EIU eyes 6 h after topical administration (68 ng/g retinal tissue, 10 ng/ml vitreous). Only background levels of tacrolimus were detected in the retina (2-8 ng/g tissue) after 0.03% Tacrolimus/PBS eyedrop administration. CONCLUSION 0.03% Tacrolimus/SFA eyedrop can penetrate ocular barrier and reach intraocular tissue at therapeutic levels in mouse eyes, particularly under inflammatory conditions. 0.03% Tacrolimus/SFA eyedrop may have therapeutic potentials for inflammatory eye diseases including uveitis.