Biotechnology and Pharmaceuticals · global
FDA Clears RAG-1C Ophthalmology Trial: Small Activating RNA Targets Postoperative Retinal Scarring for the First Time
This intravitreal injection candidate aims to activate the body’s own p21 braking mechanism to prevent abnormal proliferation after retinal detachment surgery; its actual efficacy remains to be determined by the first-in-human study.
Even when retinal detachment surgery successfully reattaches the retina, some patients still experience abnormal proliferation and migration of cells within the eye, leading to tractional scarring and renewed risks of retinal detachment and vision damage. For this complication, known as proliferative vitreoretinopathy (PVR), there are currently no approved drugs in the United States, and treatment still relies primarily on repeat surgery.
Ractigen Therapeutics announced that the U.S. Food and Drug Administration (FDA) has cleared the investigational new drug application for RAG-1C. The company plans to launch a Phase 1 study in retinal detachment surgery patients at high risk of PVR to evaluate safety, tolerability, pharmacokinetics, and preliminary efficacy. This regulatory decision allows the candidate drug to enter clinical trials; it does not mean that the FDA has confirmed its efficacy or approved it for marketing.
RAG-1C uses small activating RNA (saRNA), an approach that differs from interference RNA used to suppress gene expression. It is designed to reactivate the CDKN1A gene and increase expression of the cell-cycle inhibitory protein p21, applying a brake to the proliferation of retinal pigment epithelial cells that become excessively active after surgery or injury. The drug is delivered into the vitreous through the company’s lipid-conjugated oligonucleotide LiCO system, with the goal of producing a more sustained local effect within the eye.
The concept is supported by cellular and animal data. A study published in *PLOS ONE* in 2023 showed that RAG1-40-53, a chemically modified saRNA associated with the RAG-1C program, increased p21 in cultured human retinal pigment epithelial cells and inhibited proliferation, cell-cycle progression, and TGF-β1-induced migration. Its cholesterol-conjugated version remained in the vitreous of rabbit eyes for at least eight days and inhibited the worsening of experimental PVR.
Patent application documents disclose additional formulation and dosing data: intravitreal doses in rabbit eyes ranged from 0.03 to 1 milligram, with ocular p21 expression showing a trend of increasing with the dose. However, patent data do not constitute independent clinical validation, and rabbit models cannot fully reproduce the complex inflammatory, fibrotic, and tractional processes that occur after retinal surgery in humans.
Background
RAG-1C had already received approval from China’s Center for Drug Evaluation in March 2025 to begin clinical trials. The Chinese study plan announced at the time was a multicenter, randomized, double-blind, dose-escalation trial, likewise involving patients undergoing vitrectomy who require PVR prevention. The latest U.S. IND clearance now enables the same candidate drug to advance into human studies in both China and the United States.
The largest gap remains human evidence. The company has not yet disclosed the actual start date of the U.S. trial, the number of participants, dose groups, or the method for assessing the primary efficacy endpoint; multiple authors of the existing paper also have ties to Ractigen. The initial study therefore must first determine not only whether a single intraoperative injection can safely remain in the eye, but also whether activating p21 is sufficient to reduce scar formation and the risk of repeat surgery without interfering with normal postoperative healing.