How Potential Eye Treatments Like RGN-259 Work Detailed in Study

How Potential Eye Treatments Like RGN-259 Work Detailed in Study

Various mechanisms by which thymosin beta 4 (Tβ4) — a molecule currently being investigated to treat eye disorders that include dry eye syndrome and neurotrophic keratitis — promotes tissue healing and regeneration were detailed in a recent study.

These discoveries were made by investigators at GtreeBNT — a Korean company that, with its venture partner RegeneRx Biopharmaceuticals, is developing a Tβ4-based eye drop treatment called RGN-259 — and research colleagues. The two companies created a U.S. joint venture, ReGenTree, that is specializing in ophthalmology work.

RGN-259’s efficacy and safety is being tested in a Phase 3 clinical study (NCT02600429), called SEER-1, in NK patients at sites across the U.S. This trial is expected to conclude in September.

Findings were reported in the study, “Purinergic Signaling Involvement in Thymosin β4-mediated Corneal Epithelial Cell Migration,” published in the journal Current Eye Research.

Neurotrophic keratitis (NK) is a rare degenerative eye disease that affects the nerves serving the cornea, the transparent protective outer layer of the eye that works like a window to control and focus the entry of light. When these nerves malfunction, the cornea loses an ability to repair itself and gradually starts to breakdown.

Tβ4 is a small molecule that has been shown to possess strong regenerative and anti-inflammatory properties in different tissues and organs in the body, including the skin, lungs, and cornea.

Its potential to repair corneal tissue following damage led to the development of Tβ4-based therapies, including RGN-259, that are now being tested in clinical trials in various eye disorders.

“However, while a lot is known about the biological activities of Tβ4 in many different tissues, little is known about its receptor(s) or downstream signaling pathways,” the researchers wrote.

To explore the molecular mechanisms underlying the regenerative properties of Tβ4, investigators treated lab-cultured human corneal epithelial cells (HCECs) — cells making up the surface of the cornea — with different concentrations of Tβ4.

Following treatment, researchers assessed the cells’ ability to proliferate and migrate. They also used techniques to measure the levels of calcium found inside cells, as well as the amount of adenosine triphosphate (ATP) — the molecule that cells use as fuel — being produced.

Tβ4 was found to promote cell proliferation and migration in a dose- and time-dependent fashion.

In addition, treatment was seen to increase the levels of calcium found inside cells, as well as the amount of ATP they produced. It also promoted the activation of ERK1 and ERK2, two enzymes involved in cellular ERK signaling, which controls cell proliferation, maturation, and survival.

All these effects were blocked when researchers treated cells with an inhibitor of the P2X7 receptor, a protein receptor found on the surface of different cell types that was one of the candidates to mediate the effects of Tβ4 in HCECs.

“Our study suggests that Tβ4 application to the eye may promote corneal epithelial and stem cell proliferation and migration in patients with ophthalmic injury by increasing ATP levels. In turn, this increase in ATP levels may activate the P2X7 purinergic receptor to increase [calcium entry] that subsequently activates the [ERK pathway],” the researchers concluded.

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