Horizon Pharma has enrolled the first patient in a Phase III clinical trial assessing its experimental medicine teprotumumab for moderate-to-severe active thyroid eye disease (TED).

TED, also referred to as Graves’ eye disease or Graves’ orbitopathy, is an eye condition in which the eye muscles and fatty tissue behind the eye become inflamed, which can cause proptosis, where the eyes are pushed forward causing “staring” or “bulging” eyes and the eyes and eyelids become swollen and red.

In some cases there is swelling and stiffness of the muscles that move the eyes so that they are no longer in line with each other, or the eyelids are unable to close.

Timothy Walbert, chairman, president and chief executive officer of the Dublin, Ireland-based group, highlighted “a clinically significant unmet” need among people with TED, for which there are no approved treatment options.

“The initiation of our confirmatory Phase III clinical trial evaluating teprotumumab is a significant step as we rapidly expand our strategy to pursue development-stage medicines for people living with rare and devastating diseases,” he said.

The clinical trial, Treatment of Graves’ Orbitopathy (Thyroid Eye Disease) to Reduce Proptosis with Teprotumumab Infusions in a Randomized, Placebo-Controlled, Clinical Study (OPTIC), will enroll 76 patients across 11 centers in the US, Germany and Italy.

It follows “clinically meaningful and highly statistically significant” results from a Phase II study, published in The New England Journal of Medicine earlier this year, which showed that the monoclonal antibody met its primary endpoint of response in the study eye as well as its secondary endpoints, and was generally well tolerated.