Study protocol for a multicentre, open-label, single-arm phase I/II trial to evaluate the safety and efficacy of ripasudil 0.4% eye drops for retinopathy of prematurity

Introduction: Retinopathy of prematurity (ROP) is a vascular proliferative disorder that occurs in preterm infants. Existing treatments are only indicated in severe ROP cases due to the high invasiveness and the potential risk of irreversible side effects. We previously elucidated that ripasudil, a selective inhibitor of the Rho-associated protein kinase, has the ability to inhibit abnormal retinal neovascularisation in animal models. In addition, ripasudil eye drops (Glanatec ophthalmic solution 0.4%) have been already used for the treatment of glaucoma. Since eye drop therapy is less invasive, early intervention for ROP is possible. The purpose of this phase I/II trial is to evaluate the safety and efficacy of ripasudil eye drops for preterm infants with ROP.

Methods and analysis: This is a multicentre, open-label, single-arm phase I/II trial. To evaluate the safety and efficacy of ripasudil as much as possible, ripasudil will be administered to all enrolled preterm infants with zone I/II, stage 1, or worse ROP. The safety and efficacy of ripasudil in treated patients will be assessed in comparison to a historical control group. Because this is the first trial of ripasudil in preterm infants, a dose-escalation study (once daily for 1 week, then two times per day for 2 weeks) will be conducted in phase I. After obtaining approval from the independent data and safety monitoring board to continue the trial after the completion of phase I, phase II will be conducted. In phase II, ripasudil eye drops will be administered two times per day for 12 weeks. The primary endpoint in phase II is also safety. Efficacy and pharmacokinetics will be evaluated as secondary endpoints.

Ethics and dissemination: This study protocol was approved by the institutional review board at each of the participating centres. Data will be presented at international conferences and published in peer-reviewed journals.

Trial registration numbers: NCT04621136 and jRCT2071200047.