MedImmune Inc., a Gaithersburg biotechnology company, is jumping into the race to create an effective drug to treat lupus.

The company said yesterday that it filed a new drug application with the Food and Drug Administration and expects to begin human testing within the first half of 2006.

Lupus is a potentially fatal disease that affects the body's immune system and causes problems in a patient's heart, brain, kidneys, skin and lungs. More than 1.4 million people have the disease, which primarily strikes women.

Effective treatments for lupus have largely eluded the pharmaceutical industry. There has not been a new drug for the disease in 40 years.

The decision by MedImmune puts the company in competition with another local candidate, Human Genome Sciences Inc., which last week reported that its lupus treatment fell short of expectations during the latest round of human testing. The Rockville company's stock dropped 29 percent that day, though executives said results of the study warranted further tests and left them confident that a drug could be successfully developed.

MedImmune's lupus-treatment candidate stems from a collaboration with Medarex Inc., a Princeton, N.J., biotechnology firm. In November 2004, MedImmune announced an agreement to develop two antibodies that Medarex had in preclinical development.

"We believe that it will treat and prevent flares of [lupus] and over the years our clinical experiments will allow us to understand whether it will cure the disease," said Anthony J. Coyle, MedImmune's senior director for research.

He said the company thinks the lupus-drug candidate could also be effective in treating psoriasis and Type 1 diabetes and may begin testing it for those diseases in the years ahead.

MedImmune executives said it will probably take five to 10 years for its drug to move through the human-testing and regulatory-approval processes before reaching the market.

With about 2,000 employees and $1.1 billion in revenue for 2004, MedImmune is one of Maryland's most successful biotechnology firms. The company is best known for its production of FluMist, a flu vaccine that is inhaled.

Shares of MedImmune closed at $32.37 yesterday, up 23 cents.