RegeneRx Biopharmaceuticals has enrolled and started treatment of the first patient in the Phase III SEER-2 trial of RGN-259 for the treatment of neurotrophic keratitis (NK).

The product is under development by the US joint venture between RegeneRx and HLB Therapeutics, ReGenTree.

Results in NK patients, who received treatment with RGN-259 have earlier demonstrated efficacy in 18 patients in the first Phase III SEER-1 trial.

The company is conducting two phase III trials (SEER-2 and SEER-3) simultaneously in the US and Europe based on these data.

Around 70 NK patients will receive RGN-259 eye drops for four weeks in each trial against placebo.

Complete corneal healing is measured as primary endpoint for the double-masked, placebo-controlled trials.

The company said that as part of the US marketing approval, two independent clinical trials showing significant safety and efficacy are required.

Formulated as a sterile, preservative-free eyedrop, RGN-259 has an active ingredient thymosin beta 4 (Tβ4) which promotes cell migration, anti-inflammation, and wound healing in NK patients.

NK, a rare disease affecting around 20,000 patients a year in the US, is now treated with Oxervate, developed by Dompé farmaceutici in Italy.

Oxervate is said to be among the most expensive pharmacy drugs in the US market.

RegeneRx has also applied for Special Protocol Assessment (SPA) to the FDA in October last year for the development of RGN-259 for dry eye syndrome.