Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial conducted using the controlled adverse environment (CAE™) model

Background: The purpose of this study was to evaluate the safety and efficacy of thymosin beta 4 ophthalmic solution (RGN-259; Tβ4) in subjects with moderate to severe dry eye using the CAE™ model.

Methods: This single-center, prospective, double-masked, placebo-controlled Phase II study randomized 72 qualifying subjects 1:1 to receive either 0.1% Tβ4 or placebo treatment for a total of 28 days. The study consisted of six visits over a 32-day period, including a screening visit (day –1), controlled adverse environment challenge (CAE) visits (day 1, day 28), and follow-up visits (days 14, 29, and 30). The primary efficacy endpoints were ocular discomfort scores and inferior corneal staining measured at visit 5 on day 29. Secondary endpoints included central and superior corneal staining, conjunctival staining, conjunctival redness, tear-film break-up time, and daily symptom scores recorded over the course of the study. Safety measures included visual acuity, slit-lamp evaluation, conjunctival redness, tear film break-up time, intraocular pressure, dilated funduscopy, and corneal sensitivity.

Results: Neither of the primary endpoints, ie, ocular discomfort or inferior corneal staining, showed a significant difference between treatment and control groups at visit 5. Despite this, significant differences between treatment groups were observed for a number of secondary endpoints. The discomfort scores in the CAE on day 28 were reduced by 27% in 0.1% Tβ4-treated subjects compared with the placebo group (P=0.0244). Subjects in the 0.1% Tβ4 treatment group also showed statistically significant improvements in central and superior corneal staining compared with staining scores in the control group (P=0.0075 and P=0.0210). No adverse events were observed. Conclusion: This study confirms the efficacy of 0.1% Tβ4 as a topical treatment for relief of signs and symptoms of dry eye. Significant improvements in both signs and symptoms of dry eye were observed, and the treatment exhibited a large safety window, with no adverse events reported by any subjects enrolled in the study.