Abbott Laboratories’ drug Humira, recently approved for a sixth condition based on juvenile arthritis, will offset a loss of revenues from the patent expiration of its neurological drug Depakote in the second half of 2008, Wall Street analysts said.

Though the potential market for Humira’s treatment of juvenile idiopathic arthritis (JIA) will be small. With around 50,000 children between the ages of four and 17 currently suffering that disease in the U.S., analysts expect it will help to bolster Humira’s already-whopping revenues significantly.

“Worldwide, we would peg the annual sales opportunity for Humira to treat JIA at approximately $200 million,” RBC Capital Markets Corp. analyst Phil Nalbone wrote in a Feb. 22 note.  On that day, he U.S. Food and Drug Administration (FDA) approved Humira for the treatment of juvenile rheumatoid arthritis.

“This is our first pediatric indication for patients under the age of 17, and we are excited about bringing this product to market for children,” Abbott’s spokeswoman Liz Shea said.

According to Abbott, JIA is the most common chronic rheumatic disease in children with onset before age 17. Typical symptoms include stiffness when awakening, limping, and joint swelling. Between 25 and 70 percent of children with JIA will still have active disease into adulthood.

“Humira is the gift that just keeps on giving. In 2007, with four approved indications, Humira generated worldwide sales of $3.1 billion. This year, with six approved uses, we are forecasting sales of $4.2 billion or a 37 percent increase,” Nalbone stated.

“Humira is a very important drug for Abbott, and its growth should help to offset the lost sales from blockbusters such as epilepsy drug Depakote due to the patent loss,” Chicago-based Morningstar Inc. analyst Damien Conover said.

Annual sales of Abbott’s Depakote rose 20 percent to $1.5 billion in 2007.

With its latest FDA approval, Humira can now treat adult rheumatoid arthritis, psoriatic arthritis , ankylosing spondylitis, Crohn's disease and psoriasis, in addition to JIA.

Abbott’s Shea said that even though the patient population with JIA is quite small, with about 50,000 patients, “Humira represents a significant step forward because it is the first biologic approved by the FDA in nearly a decade since the approval of Amgen’s Enbrel in 1999.”

According to Shea, Humira competes with Enbrel from California-based Amgen Inc. –with five conditions approved by the FDA.

“We're currently studying Humira in ulcerative colitis and pediatric Crohn's disease and plan to initiate studies in pediatric psoriasis, though none of these indications will be approved this year,” Shea said.

Autoimmune agent Humira –currently available in more than 72 countries around the world- was Abbott’s fastest growing drug in 2007 with $3.1 billion in worldwide sales, a 50 percent increase compared with 2006.

Analysts said that Humira continues to be the workhorse pharmaceutical boosting the company’s bottom line.

“Blockbuster Humira has exceeded market expectations,” Morningstar's Conover said. “With only 30 percengt market share, Humira should continue to drive growth for the entire company.”

The latest FDA action also represents Abbott's third important FDA approval this year, including Humira for psoriasis in January and blood-thinner Simcor on February 16.