A drug being developed by a local biotechnology company offers the promise of greater mobility to the 320,000 Americans with multiple sclerosis who find walking difficult. Results from a Phase 3 trial of the drug, known as Fampridine-SR, showed that a greater proportion of people had consistently improved walking speed than participants who were given a placebo, or fake pill, Hawthorne-based Acorda Therapeutics Inc. announced yesterday. Patients taking Fampridine showed an average 25.2 percent increase in walking speed compared with the 4.7 percent increase of those on a placebo. Improvement was measured by the time it took a study participant to walk 25 feet, a standard neurological test. In addition, those on the drug reported significant increases in leg strength compared to placebo-takers. Multiple sclerosis is a chronic, usually progressive disease that destroys the central nervous system. The speed at which it progresses varies among individuals. Among its wide-ranging symptoms is reduced mobility, which can slow walking times. Of the 301 patients enrolled in the 14-week study, 229 received Acorda Therapeutics' drug. About 35 percent of those patients had consistent improvement in walking speed, compared with 8.3 percent of patients who were given a placebo, Acorda reported. The patients in the study were 18 to 70 years old with a definitive diagnosis for MS and difficulty walking. The results offer hope to the 80 percent of multiple sclerosis patients for whom walking can be burdensome. They include Carol Giordano of North Salem, who has had MS for 28 years. The disease leaves Giordano able to walk only about 20 yards before she begins feeling fatigued. In addition, the weakness in her right side caused by the disease requires her to use an orthotic device to lift her leg to prevent her foot from dragging. At times, Giordano requires the aid of a cane or a wheelchair to get around. "It sounds very promising," she said of the preliminary results that Acorda's study showed. "It would definitely improve my situation a great deal."