Editas Medicine (NASDAQ:EDIT) and Allergan (NYSE:AGN) announced on Wednesday morning that they had just treated the first patient with Editas' flagship drug candidate EDIT-101 as part of the Brilliance phase 1/2 clinical trial. The new experimental gene-editing drug targets a rare eye disorder known as Leber congenital amaurosis (LCA).

What makes this particular treatment noteworthy is that it's the first time a patient's genes are being modified within the body, also known as an in vivo treatmentIn comparison, most gene-editing drugs operate on an ex vivo basis, where targeted cells are removed from the patient first before they are modified and later returned. The trial will be testing 18 LCA patients to see how they respond to EDIT-101, which will be administered via a subretinal injection.

A person snipping out a piece of a DNA strand with scissors.

Image source: Getty Images.

"The first patient dosed in the BRILLIANCE clinical trial marks a significant milestone toward delivering on the promise and potential of CRISPR medicines to durably treat devastating diseases such as LCA10," said Cynthia Collins, CEO and president of Editas.

About the condition

Leber congenital amaurosis is a type of blindness that first occurs in infants. Patients with the condition have mutations of specific genes responsible for the proper development of the retina, the part of the eye that detects light.

There's only one LCA treatment available right now, a pricey drug called Luxturna, which was developed by a now-bought-out biotech company called Spark Therapeutics. However, the drug treats only a specific type of LCA, and it isn't available for most patients with the eye disorder.