Purpose <p>Cytomegalovirus (CMV) corneal endotheliitis often causes severe visual impairment owing to irreversible corneal endothelial dysfunction. Given the side effects of systemic antiviral therapy, development of an approved topical antiviral agent for CMV corneal endotheliitis is desirable. This study evaluated the efficacy and safety of topical 0.15% GCV gel, ROH-101, in the treatment of CMV corneal endotheliitis in Japanese patients.</p> Study design <p>Open-label, multicenter, uncontrolled, phase 3 study (jRCT2051210064).</p> Methods <p>The study was conducted from August 2021 to December 2022, with a 2-week run-in period with 0.1% fluorometholone eye drops alone, a 12-week treatment period with additional ROH-101, and a 24-week post-treatment observation period after discontinuation of ROH-101. The primary endpoint was the proportion of patients achieving a CMV DNA copy number in the aqueous humor of less than 10³ copies/mL at week 12. The clinical findings and safety were assessed over the treatment and post-treatment observation periods.</p> Results <p>Twelve eyes of 12 patients with PCR-proven CMV corneal endotheliitis were enrolled. Treatment was discontinued in 1 eye owing to an adverse event. The other 11 eyes completed 12 weeks of treatment with 63.6% achieving the primary endpoint. The clinical findings, such as corneal edema, coin-shaped lesions, and anterior chamber inflammation, improved in all 11 eyes and did not worsen in 8 eyes that completed the post-treatment observation period. Endothelial cell density was well maintained, and none of the 11 eyes showed corneal endothelial dysfunction. Mild adverse drug reactions were reported in 3 eyes (8.3%).</p> Conclusion <p>ROH-101 was a safe and efficacious treatment in Japanese patients diagnosed with CMV corneal endotheliitis.</p>