June 26 (Reuters) - The U.S. Food and Drug Administration has approved Viridian Therapeutics' drug to treat patients with thyroid eye disease, the ⁠company said on Friday.

The decision gives patients a new treatment option in a market where Amgen's ⁠Tepezza has been the only approved therapy.

The approval was based on two late-stage studies that showed the drug led ⁠to rapid and sustained improvements in ‌key symptoms, including eye bulging and double vision.

Thyroid eye disease is an autoimmune condition that causes inflammation, swelling and fat expansion behind the eyes, often leading to bulging, pain redness and double vision.

The active form of the disease is marked by acute inflammation and pain that can last for months to years, while ‌its chronic form is the stable phase in which symptoms persist without active swelling.

The ​approval for ‌the drug, Lumvoa, is supported by data to ‌treat both active and chronic forms of the disease.

Lumvoa - which works by blocking IGF-1R, a receptor involved in the disease process - ⁠is administered over 12 weeks as five intravenous infusions spaced ‌three weeks apart.

Amgen's Tepezza, approved ⁠in 2020, is the only other approved ​therapy for active thyroid eye disease in ‌the U.S.

In studies, Lumvoa was the first therapy that showed a statistically significant benefit in both reducing and fully resolving double vision across different stages of the disease, Viridian said.

"We were seeing positive response ​and resolution of diplopia in the chronic patient population, which had ‌never ‌been seen before," CEO Steve Mahoney told Reuters.

The company plans to launch the treatment immediately, marking its first ‌commercial product.

Viridian told Reuters ​that it expected to price Lumvoa at parity with the existing approved IGF-1R therapy on a course-of-therapy basis.

Viridian is also developing a subcutaneous treatment for the disease, which could expand the ⁠market by allowing patients to administer the drug at home. The company expects ‌to file for its U.S. approval in early 2027.

(Reporting by Siddhi Mahatole and Puyaan Singh in ​Bengaluru; Editing by Tasim Zahid and Vijay Kishore)