Acorda Therapeutics (NASDAQ:ACOR) has given astute biotech investors the ride of their lives over the last 12 months, with shares shooting up more than eight times their low of $2.22 following the release of positive phase 3 data for its lead drug. The story of that drug goes on, as Acorda yesterday gave an overview at the UBS Global Life Sciences Conference of its progress in getting Fampridine-SR approved for sale.

Acorda is testing its sustained-release version of fampridine as a treatment for improving walking ability in patients with multiple sclerosis. Fampridine-SR is currently in a second phase 3 trial enrolling 200 patients. The trial is a relatively simple eight-week efficacy study with timed 25-foot walk tests as the primary endpoint. Results are expected in mid-2008.

Acorda negotiated a special protocol assessment (SPA) with the FDA for the trial, clearly defining the endpoints that must be achieved, but that doesn't guarantee success with the FDA. Investors in Encysive Pharmaceuticals (NASDAQ:ENCY) or GPC Biotech (NASDAQ:GPCB) could tell you all about that.

In the previous phase 3 study, which ended in the third quarter of last year, patients were tested for improvements in their 25-foot walk speed over the study's 14-week treatment period. Four times as many patients taking Fampridine-SR saw improvements than those not taking the drug.

While Fampridine-SR may achieve positive efficacy results, investors should watch out for the side-effect profile, as there have been issues with seizures.

Fampridine-SR is interesting because it improves some of the symptoms related to multiple sclerosis, rather than attempting to arrest disease progression, as most drugs do. Also, no data to date suggests it couldn't be used along with existing MS therapies like BETASERON from Bayer (NYSE:BAY) or Rebif from EMD Serono and Pfizer (NYSE:PFE).

The complementary nature of Fampridine-SR means Acorda wouldn't have to compete against the marketing muscle of some of the big-name multiple sclerosis drug sellers. It's also why Acorda is going to try to market the drug itself in the U.S. if the data coming up next year leads to FDA approval in 2009.

Looking for more Foolish drug-stock coverage? Check out the Fool's market-beating Rule Breakers newsletter. You can take a look at all our recommendations with a 30-day free trial.

Fool contributor Brian Lawler does not own shares of any company mentioned in this article. Pfizer is a selection of the Inside Value newsletter. The Fool's disclosure policy has a special protocol assessment with the FDA.