Oxervate (cenegermin) eyedrops improved corneal sensitivity in people with neurotrophic keratitis (NK), according to the results of two Phase 2 trials.

Those results had been expected to be presented at the 2020 ARVO Annual Meeting, as an abstract titled “Effect of topical recombinant human nerve growth factor (cenegermin) on corneal sensitivity in patients with neurotrophic keratitis.” Due to the meeting’s cancellation, the results were published online instead.

Approved as a prescription eye drop by the U.S. Food and Drug Administration, Oxervate was developed by Dompé for the treatment of NK, a rare disease affecting the cornea.

Cenegermin, Oxervate’s active ingredient, is a recombinant, or manufactured, human nerve growth factor (NGF). NGF is a protein that plays a key role in the survival and growth of nerve cells. In the cornea — the transparent protective outer layer of the eye — it is involved in wound healing and tear secretion, and helps maintain the health of corneal nerves.

The complete or partial loss of corneal sensation is a hallmark feature of NK. This happens because the cornea’s outermost layer, called the epithelium, breaks down due to damage to the corneal nerves.

Previous data from these two Phase 2 studies had shown that Oxervate was a safe and effective treatment for healing and reducing corneal lesions. But the researchers initially had deemed its effect on corneal sensitivity as insignificant.

Now, however, after pooling the data from both trials, the investigators observed a statistically significant improvement in the participants’ corneal sensitivity over a four-week treatment period, and a trend toward statistically significant improvement after eight weeks of therapy.

One trial took place in the U.S. (NGF0214, NCT02227147), enrolling 38 participants, and the other in Europe (REPARO, NCT01756456), involving 174 patients. All of the participants were age 18 and older, had NK classified as stage 2 (identified by persistent epithelial defects) or stage 3 (identified by corneal ulcers) and were resistant to one or more conventional treatments.

Corneal sensitivity was measured with a Cochet-Bonnet device, in which a small nylon filament is used to assess tactile sensation directly on the cornea. The filament is extended to its full length of six centimeters and retracted in half-centimeter increments until the patient feels its contact. Because the pressure on the eye increases as the filament is retracted, longer lengths indicate greater sensitivity.

Over the course of four weeks, the Cochet-Bonnet measurements of participants receiving Oxervate increased from an average of 0.98 cm to 1.14 cm. In comparison, control participants, who received eye drops with no medicine in them, decreased from 0.91 cm to 0.64 cm. This was deemed statistically significant.

The final measurements, taken at week eight, were 1.46 cm for the Oxervate group and 0.91 cm for the control group. These changes had a trend toward statistical significance, the researchers said.