K-115, a strong and selective inhibitor of Rho-associated coiled coil-forming protein kinase (ROCK), was developed as a therapeutic drug for glaucoma. In long-term phase 3 clinical studies, blepharitis and allergic conjunctivitis were observed. Nonclinical studies were conducted to determine if these adverse effects were caused by the sensitizing potential of K-115. In mouse local lymph node assays (LLNA), sensitizing reactions were not observed at 8.17% w/v of K-115, but weak positive skin sensitivity with a 2.0% K-115 ophthalmic solution was observed. K-115 ophthalmic solution was classified as having slight sensitizing potential. No photosensitization potential was observed with UV-LLNA studies and skin photosensitization studies. In a guinea pig conjunctivitis model study, K-115 had no immediate allergic effect on conjunctivitis, and did not function as an antigen. Furthermore, in ocular toxicity studies in rabbits (26 weeks) and monkeys (52 weeks), no abnormalities were observed in ophthalmic and pathological examinations. Considering the results of nonclinical sensitization and ocular toxicity studies, the clinical adverse effects were possibly not caused by K-115 sensitization potential.