* First approved treatment for high-risk neuroblastoma

* Analyst expects drug to cost $150,000 per patient per year (Adds analyst comment, background)

By Amrutha Penumudi

March 10 (Reuters) - The U.S. Food and Drug Administration said it approved United Therapeutics Corp's drug to treat an aggressive form of neuroblastoma, a rare cancer that typically occurs in children below 5 years.

Unituxin is the first drug approved to treat high-risk neuroblastoma patients who have a greater chance of tumors recurring or progressing after chemotherapy, the FDA said.

Wedbush Securities analyst Liana Moussatos estimated there are about 425 high-risk patients in the United States and 1,275 worldwide.

"Drugs for rare diseases are allowed to be expensive so yes, I believe insurers will cover it," she said.

She expects the drug to be priced at $150,000 per patient per year in the United States and gross annual sales to peak at about $60 million around 2022.

There are an estimated 650 cases of neuroblastoma diagnosed in the United States each year. The disease, slightly more common in boys, forms from immature nerve cells.

Patients with high-risk neuroblastoma only have a 40 to 50 percent chance of long-term survival despite aggressive therapy.

The safety and effectiveness of Unituxin were tested in a clinical trial comprising 226 patients. After three years of treatment, 63 percent of those receiving the drug were alive and free of tumor growth. (http://1.usa.gov/1GntoU3)

Unituxin is approved for use along with surgery, chemotherapy and radiation.

The drug, a combination of mouse and human DNA, is an antibody that sticks to the surface of the cancer-affected cells and uses the body's immune system to destroy the cells.

Companies such as Bayer AG, Ignyta Inc and MabVax Therapeutics Holding Inc are conducting clinical trials for treatments for neuroblastoma. Ignyta's candidate recently won FDA's orphan-drug status.

The National Cancer Institute is conducting a number of trials on high-risk neuroblastoma treatments.

(Editing by Don Sebastian)