Safety, Tolerability and PK Characteristics of RM301B Eye Drops: A Single-Centre, Randomized, Double-Blind, Dose-Escalation, Placebo-Controlled Phase I Clinical Trial.

INTRODUCTION

RM301B eye drops are a dexamethasone (DEX)-based formulation indicated for treating macular oedema associated with retinal vein occlusion (RVO). Non-clinical pharmacodynamic studies have demonstrated that RM301B eye drops have a certain inhibitory effect on retinal oedema. This study aimed to evaluate the safety, tolerability, and pharmacokinetic (PK) characteristics of RM301B eye drops following administration in healthy subjects.

METHODS

A single-centre, randomized, double-blind, placebo-controlled, dose-escalation Phase I clinical study. In the single-dose study, ten subjects received once-daily RM301B or placebo. In the multiple ascending dose study, 30 subjects received 3, 6, or 8 daily instillations for 7 days. Safety and tolerability were monitored throughout the study, with plasma samples collected for PK analysis.

RESULTS

No serious adverse events (SAEs) occurred in the study. All mild adverse events (AEs) were determined to be unrelated to RM301B. PK results indicated detectable plasma concentrations (0.10-0.40 ng/ml) only in individual subjects within 5 h post-single dose and at specific time points following multiple dosing. Mean area under the curve from time zero to t (AUC0-t) following single dosing was merely 0.48 h·ng/ml. Area under the curve at steady state (AUCss) after multiple dosing was 1.69 and 1.40 h·ng/ml for Cohorts 1 and 3, respectively. Minimal systemic exposure was observed across all cohorts post-administration.

CONCLUSIONS

RM301B eye drops demonstrated safety and good tolerability in subjects, characterized by minimal plasma exposure, a short half-life, and no significant accumulation. Subsequent trials will evaluate the safety and efficacy of RM301B in patients with macular oedema associated with RVO.

TRIAL REGISTRATION: ChiCTR2500111837 (retrospectively registered on November 6, 2025).