By Dania Nadeem

(Reuters) – Horizon Therapeutics Plc on Tuesday priced its treatment for thyroid eye disease at $14,900 per vial following the U.S. FDA approval and said the drug would be available in the United States in the coming weeks.

Shares of the company rose 4.2% in extended trading after the drug regulator said Tepezza is the first approved treatment for the vision-threatening autoimmune disorder, in which the muscles and fatty tissue behind the eye become inflamed and expand.

The drug could spare patients from needing multiple invasive surgeries by providing an alternative, non-surgical treatment option, the FDA said.

Tepezza is expected to further benefit Horizon’s best-performing unit that focuses on rare conditions and made up for nearly three-quarters of its latest quarterly revenue.

Horizon said the drug will earn about $105 million in milestone payments in the first half of 2020. The company last week raised its expectations for peak U.S. annual net sales to more than $1 billion from the prior forecast of more than $750 million.

Thyroid eye disease usually occurs in people with Graves’ disease, an immune system disorder that results in overproduction of thyroid hormones.

It begins with an active phase that may last for up to three years, after which damage to the eyes can be irreversible.

As it progresses, the disease causes double vision, bulging of the eye and misalignment, severely affecting the quality of life of patients.

An estimated 15,000 to 20,000 patients in the United States suffer from moderate to severe forms of the disease in the active phase.

Tepezza targets the disease in the active phase, and significantly reduced bulging of the eye in patients who were part of the clinical trials.

In December, an FDA expert panel had unanimously voted in favor of the treatment.

Horizon said it was evaluating additional indications for Tepezza and plans to start an exploratory study on its application in treating diffuse cutaneous scleroderma, a rare skin disease with no treatment options.

(Reporting by Vishwadha Chander and Dania Nadeem; Editing by Arun Koyyur)