Does the demyelination from multiple sclerosis affect your ability to walk?

If so, then Acorda Therapeutics, Inc. would like you to know that on January 30, 2009, they submitted a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for Fampridine-SR, a novel therapy developed to “improve walking ability” in people with multiple sclerosis.

Fampridine-SR is a sustained-release tablet formulation of the investigational drug fampridine (4-aminopyridine or 4-AP). In laboratory studies, fampridine has been found to improve impulse conduction in nerve fibers in which the insulating layer, called myelin, has been damaged.  Currently, 4-aminopyridine (4-AP) is only available through compounding pharmacies, while Fampridine’s patented release formulation has been developed to provide a more consistent level of medication.

For lists of published studies regarding 4-AP and Fampridine-SR, see What is 4-aminopyridine? and 4-AP, Fampridine-SR, and Multiple Sclerosis.  I had taken an interest in Acorda and Fampridine last summer, the result being a series of posts outlining the research involved in bringing this product to market.

The first clinical study of 4-aminopyridine in MS patients was published in 1983 and focused primarily on visual symptoms. The Phase 2 and two Phase 3 studies conducted by Acorda, total enrollment 660, focused on walking speed and lower leg strength.  Through extension trials, 463 patients (approx 70%) continue to take Fampridine-SR with treatment duration ranging from seven months to almost five years.

Quoted in the February 2nd press release, Dr. Ron Cohen, Acorda Therapeutics President and CEO, says that “walking impairment is one of the most pervasive and alarming aspects of MS for patients, their families and their health care providers. There are no medicines currently indicated to improve walking ability in people with MS, and Fampridine-SR therefore may represent an important new approach to MS therapy. We are excited to have taken this major step toward potentially making Fampridine-SR available to help people with MS.”

On a personal note, I can share with our readers that a number of fellow patients have expressed interest in knowing when Fampridine-SR may become FDA-approved.  The hope is that, as a potassium-channel blocker, Fampridine-SR might assist with functions beyond walking ability.  In fact, in an interview I conducted with Dr. Cohen last summer, he shared that the biggest challenge in designing the clinical trials came from trying to show how exactly patients were benefiting from the drug and then to determine a way to prove it.

“In order to identify the specific benefits [of 4-AP], Andrew Blight, now Acorda's Chief Scientific Officer, traveled to MS centers around the country and interviewed patients, patients' families, doctors, and nurses to help formulate the hypotheses related to the benefits of the drug. What Dr. Blight was told was that patients using 4-AP experienced improvements with stamina, fatigue, vision, bowels, and strength. The most frequent benefits were related to walking, strength, and stamina,” said Dr. Cohen.