Safety and Efficacy of Sustained Release Dalfampridine in Transverse Myelitis (Re-Launch)

Fampridine (4-aminopyridine) is a potassium channel blocker that has been studied since the 1970s for its effect on amplifying conductivity in peripheral nerves, potentiating neurotransmitter release in muscles and increasing post-synaptic action potentials in the spinal cord. It was tested in other neurologic conditions over the next two decades and was found to have a limited therapeutic window due to the stimulation of seizures at high doses. The first randomized, placebo-controlled, double-blinded study of fampridine in 70 patients found significant improvements in a number of neurophysiological parameters while on fampridine compared to placebo. Since then, at least six additional studies on oral fampridine in Multiple Sclerosis (MS) were conducted and found to have some significant neurologic function. Although only a small incidence of seizure or altered mental status were reported in these studies, the concern about fampridine causing seizures remained a barrier in the acceptance of fampridine as an MS therapy in the general neurology community.

Recently, Biogen-Idec and Acorda have teamed up in the development of a sustained-release formulation of fampridine, dalfampridine, in which plasma concentrations of the drug and avoids toxic doses that lead to seizures. In two clinical trials, dalfampridine has been shown to be beneficial in two large cohorts of multiple sclerosis patients with noted improvements in gait and lower extremity muscle strength. Seizures were only seen in high doses of 20 mg or more whereas benefits were evident at the approved dose of 10 mg twice daily.

The Food and Drug Administration (FDA) approved dalfampridine for use in multiple sclerosis in 2009 based on the key study that evaluated gait by timed 25-foot walk. About 35-40% of study participants responded and this group improved their walking speed by about 20%.

The investigator's interest in dalfampridine is focused more narrowly on a subset of patients with a demyelinating disorder that is restricted to the spinal cord, transverse myelitis (TM), was not included in any previous human trials of dalfampridine. In contrast to MS, which affects the entire system, transverse myelitis affects the spinal cord and largely spares the brain. It is not associated with an increased risk of seizure.

Transverse myelitis is defined as an episode of inflammation in the spinal cord leading to disability at the level of the lesion and below. The majority of TM lesions strike the thoracic cord causing impairments in lower extremities. A single lesion is the cause of all of their symptoms. The goal of using dalfampridine in these patients is to amplify axonal conductance across the lesion. This would manifest as improved neurologic function involving the lower extremities including gait. This is a straightforward proof of concept model proving the mechanism of action of dalfampridine.