It's slimy, with a texture similar to motor oil. It's in clinical trials now around the country. And if the highly purified mixture of hyaluronic acid works as expected, the clear liquid could offer breakthrough relief in just a few years to millions of Americans who suffer from debilitating arthritis of the ankle.

If that happens, it'll also bring windfall profits to venture capital firms that have invested more than $23 million in Alpharetta-based Carticept Medical Inc. to develop the injectable product, which the company calls Agilus. Private investors would do well, too.

Bob Andres/AJC (ENLARGE)

Richard Hales, a senior engineering intern at Georgia Tech, checks on wear testing of cartilage replacement material for Carticept Medical of Alpharetta. Venture capital firms have invested more than $23 million in Carticept Medical.

Bob Andres/AJC (ENLARGE)

Carticept CEO Timothy J. Patrick: 'We think the market opportunity is about a billion dollars a year.'

Georgia Tech (ENLARGE)

Georgia Tech professor Barbara D. Boyan, Carticept's chief scientific officer, said 'it is scientifically known' that the project works in the knee and larger joints.

CARTICEPT MEDICAL INC. Location: Alpharetta Employees: 15 Products: Solutions and devices to ease pain of arthritis President and CEO: Timothy J. Patrick Chief scientific officer: Barbara D. Boyan, also chair in tissue engineering at Georgia Tech and one of 60 "eminent scholars" recruited by the Georgia Research Alliance, which promotes science-based economic development. Primary investors: Domain Associates, New Enterprise Associates BUSINESS Latest Headlines: UPS Foundation donates $1 million to environmental groups  Feds investigate failure of Washington Mutual  Fuel costs punish Delta earnings  Foreclosure notices in Gwinnett up 13% from 2007  Gas for 35 cents a gallon? Wisconsin drivers score cheap fuel  • More business news • Business photo galleries

At least 2 million Americans suffer from ankle arthritis. And with each new year, more of the nation's 78 million baby boomers are coming down with the chronic, progressive, irreversible disease that, unlike osteoarthritis in most other joints, is extremely hard to treat.

In fact, treatment now mainly amounts to a doctor's admonition to take two anti-inflammatories and call back in the morning.

And that's just not the kind of doctor's advice arthritis sufferers want to hear, said Timothy J. Patrick, president and chief executive of Carticept, a 15-employee firm and one of more than 150 in Atlanta's fast-growing biomedical sector.

Take Donna Reynolds, 52, of Rochester, N.Y., a patient of one of the doctors involved in Carticept's clinical trial, which started this month and involves 380 people.

She hopes Agilus works and cushions the many tiny bones in the ankle so that others won't have to go through what she has endured since she broke her ankle while skiing five years ago.

"I wouldn't be sitting here, wondering how I'm going to get my foot in a ski boot," said Reynolds, who has undergone four surgeries since. "I'm going to ski again, I promise, but I had to have the bones fused, making me less mobile, so I won't be able to do what I could before. The pain was terrible. The doctors tried everything, but nothing worked."

Most people who develop arthritis in the ankle do so from normal wear and tear. But injuries make development of the disease more probable.

The company hopes to determine that Agilus works better at reducing arthritic ankle pain than analgesics, steroids, saline injections, physical therapy or soft-support bracing.

It's a molecularly thick formulation of highly purified hyaluronan, and if it works, Patrick's hope is that by 2010, people like Reynolds with arthritic ankles might be able to find relief with simple injections.

Agilus represents an investigational application of a proven treatment called viscosupplementation, which has been used safely and effectively for many years for osteoarthritis of the knee.

Hyaluronan already is used in Europe to soothe arthritic ankles, but so far has been approved by the U.S. Food and Drug Administration only for use in larger joints, such as knees.

Patrick said the trial could be finished by late next year, and that Agilus could be approved by the FDA as soon as 2010.

"Osteoarthritis of the ankle is a significant and debilitating problem for millions of patients worldwide," said Dr. Judith Baumhauer, principal investigator of the study and a professor at the University of Rochester. "For many patients with ankle osteoarthritis, there is a significant void in the current treatment [arsenal] that Agilus could potentially address."

Barbara D. Boyan, professor of biomedical engineering at Georgia Tech and Carticept's chief scientific officer, said "it is scientifically known that it works" in the knee and larger joints, but there is no proof that it helps in the ankle.

"You want a formulation that can be injected," said Boyan, 59, who specializes in cell biology. "There are a lot of little joints, very small spaces, in the ankle. Think of it as honey. It acts as a lubricant. And there will be much more of a need for this as we baby boomers, those of us before Nike, grow older."

Dr. John Reach Jr., director of Yale's foot and ankle service, said ankle arthritis is increasing and that fusion surgery has become the "mainstay."

He believes Carticept's product "can help fill the void between pill and brace treatment and operative treatment."

Currently, he said, options for treating ankle arthritis are limited because "ankles and foot joints are extremely small and fussy."

Patrick said the company "is very hopeful" because hyaluronan "is a naturally occurring substance that is a major component of a lubricant that reduces the friction between bones and joints" and could act as "sort of a shock absorber, preventing pain and bone deterioration."

"There have been five or six small studies that have shown it works in the ankle, but they lacked the statistical power needed by the FDA. Our number gives us statistical power to show that this naturally occurring lubricant will work in small joints like we know it works in the knee," he said.

If he's right, then "there are 6 million grandmothers out there who have very painful arthritis pain in their thumbs who would be helped, too," he said.

Dr. Sam A. Labib, director of the foot and ankle service at Emory University and a professor of orthopedic surgery there, said a number of forms of hyaluronan already are on the market.

"We think it stimulates the body to form more of the good stuff, the hyaluronan, that's naturally there," Labib said.

Reynolds, like company officials, hopes so.

"I had a fracture, pins and plates in April 2003," she said. "I was living on pain medications and anti-inflammatories. I don't limp. But it's not going to be the same. I just wish there would have been another way."

Company executives and venture capitalists are mulling over whether to take the company public, a decision that will depend to some extent on the success of the Agilus trial.

Because so many people worldwide develop arthritis in the ankle, "demand for the product would be high, and we think the market opportunity is about a billion dollars a year," Patrick said. "That's pretty big."

Carticept's scientists also are working on other arthritis aids, including a synthetic cartilage.

"We hope in coming years to make millions and millions of baby boomers very happy," Patrick said.