The U.S. Food and Drug Administration on Thursday approved the first drug to treat a rare, progressive lung disease that mainly affects women of childbearing age. 

The drug, Rapamune, known chemically as sirolimus, is made by Pfizer Inc and is designed to treat lymphangioleiomyomatosis (LAM), a disease that causes lung damage and affects only two to five women per million worldwide.

Symptoms of the disease are similar to those of other lung conditions such as asthma, emphysema and bronchitis, according to the LAM Foundation.

The drug was originally approved in 1999 to help prevent organ rejection in patients receiving kidney transplants. It was reviewed under the FDA's "breakthrough therapy" program, which helps speed products for unmet needs through the development and regulatory process.

In patients with LAM, abnormal growth of smooth muscle cells invade lung tissues, making it hard to breathe and limiting the supply of oxygen to the body. The cells are not cancerous but do grow uncontrollably in the lungs causing the airways, blood and lymph vessels to become obstructed.

A clinical trial of 89 patients over 12 months showed patients taking Rapamune had a slower decline in lung function than those taking a placebo. After the drug was stopped, the decline in lung function resumed at the same rate as the placebo group, the FDA said.