By Mary Welch

Atrix Laboratories Inc. won FDA approval for Atridox, a site-selective antibiotic therapy for periodontal disease, triggering a $5 million milestone payment from marketing partner Block Drug Corp., which will pay another $5 million when the treatment becomes available to dentists, probably in the next 30 to 45 days.

"This is a home run," said Andrew Forman, an analyst with Dillon, Read & Co., in New York. He called the agency's clearance of Atridox "one of the biggest FDA approvals of the year. The question is not how much money will this make, but how long will it take."

Forman estimates Atridox will generate $50 million in sales in 1999, $100 million in 2000, and $200 million in 2001.

John Urheim, vice chairman and CEO of Fort Collins, Colo.-based Atrix, said it took 11 years to develop the treatment on which the company was founded.

"We had gone through a series of Phase III trials with a different active ingredient, and it was not successful," he said. "In 1992, we started over again with doxycycline hyclate as the active ingredient, and found that it was profoundly effective."

Periodontal disease, a progressive infection of the gums and surrounding tissue, affects an estimated 50 million Americans, yet only about 7.5 million receive treatment. More than $6.5 billion is spent annually on treating this condition in the U.S. The second most widespread infectious disease (after the common cold), periodontal disease starts as a painless infection of the gums caused by a buildup of bacteria known as dental plaque.

As the disease progresses, the gums separate from the teeth to form pockets, which helps the plaque spread below the gumline. Without treatment, the bacterial buildup destroys the soft tissue and bone that hold the teeth. Periodontal disease is the leading cause of tooth loss in adults.

Traditional Treatments Scare Away Patients

Scaling and root-planing are the traditional ways of removing bacterial buildup. While periodontal disease is a chronic disorder, it can usually be successfully controlled. The problem is that a large percentage of patients — 34 percent — don't show up at the dentist's office for maintenance therapy following their initial treatment.

Forman, whose father was a dentist, said he knows why.

"Let's face it, not much has changed in dentistry in the last 100 years," he said. "Nicer drills, fancier X-ray machines, a great sound system so you don't pay any attention to what's happening to you." Still, he said, scaling and planing is "like a jack hammer. It's bloody and painful. People don't want to deal with it."

Atridox combines doxycycline, an FDA-approved member of the tetracycline class of antibiotics, with a biodegradable polymer developed by Atrix. The gel is placed into an infected area around the teeth, where it conforms to the shape of the periodontal pocket, solidifies and then releases the antibiotic over a seven-day period to kill the bacteria. It is the first subgingival, antimicrobial treatment of its kind for peridontitis in this country. Patients do not require anesthesia.

Forman believes that at least half of the 7.5 million patients now undergoing treatment will switch to Atridox. "But the real question is, how many of the 42 million sufferers who don't go for treatment now will show up at the dentist?" he said.

Phase IIIs The Largest Ever For Periodontal Disease

Atrix's Phase III studies were the largest trials ever conducted for the treatment of periodontal disease. The FDA received data on 822 patients at 20 sites across the country, showing Atridox resulted in a better reduction rate in pocket depth and attachment — the two most commonly used criteria to judge clinical effectiveness — than traditional methods.

Block, of Jersey City, N.J., agreed to a $50 million deal to market three of Atrix's products for periodontal disease in the U.S. and Canada. The first, Atrisorb Barrier for Guided Tissue Regeneration (GTR), approved in March 1996, is a device used during gum surgery, in which the roots of the affected tooth are exposed. The product uses a barrier to selectively promote the growth of cells that will re-anchor teeth to the jawbone. (See BioWorld Today, Dec. 19, 1996, p. 1.)

Atridox is by far the most significant of the three products. Atrix has received $14 million from Block, and expects more payments based on sales, Urheim said. Atrix's third product is a second-generation Atrisorb Barrier that uses doxycycline to reduce infection and give better results following GTR surgery. The product is in Phase III trials.

Atrix retains manufacturing rights and is in negotiations with several multinational pharmaceutical companies as well as country-specific firms to commercialize Atridox outside the U.S. and Canada. The company received preliminary marketing approval in the U.K., with the final go-ahead expected by year's end. Approval in the rest of Europe is expected to follow next year, Urheim said.

Atrix's stock (NASDAQ:ATRX) closed Tuesday at $14, up $1. *