Acorda Therapeutics, a biotechnology company, has reported that the post-marketing commitment study exploring 5mg dose of dalfampridine-ER in multiple sclerosis (MS) patients failed to confirm efficacy of the 5mg dose.

The Ampyra (dalfampridine) 10mg extended release tablet is, at present, approved by the FDA as a treatment to improve walking ability in patients with MS.

A total of 430 participants were randomised across three treatment arms; placebo, 5mg or the currently marketed dose of 10mg of dalfampridine-ER, twice daily.

Acorda chief medical officer Dr Enrique Carrazana said the current study, together with the Ampyra registration studies, continues to show that 10mg twice daily is the appropriate, safe and effective dose.

"The 5mg twice daily dose of dalfampridine-ER failed to show efficacy over placebo on the primary or secondary measures," Carrazana said.

"The 10mg twice daily dose, which has consistently shown efficacy in our well-controlled clinical trials, did not meet the previously untested primary outcome measure selected for this study."

The primary outcome was the change in walking speed (feet/second) on the Timed 25-Foot Walk (T25FW) test at visit three, measured at the time of peak plasma drug concentration, versus baseline.

According to the study, improvements in the primary outcome for the 5mg dose (0.423 ft/sec, p=0.457) and the 10mg dose (0.478 ft/sec, p=0.107) at visit three were not statistically significant compared to placebo (0.363 ft/sec).

A planned secondary outcome measure of improvement in walking, the six-Minute Walk Test, was applied at visit two in a subset of the study participants (approximately 50 randomised per treatment arm).

The 10mg dose, but not the 5mg dose, showed a significant improvement compared to placebo, the study reported.

Changes in perceived effect of MS on walking-related activities, as measured by the self-reported 12-item MS walking scale, showed improvements for the 10mg and 5mg groups that were not significant compared to placebo.

The study did not reveal any new safety signals while the adverse events reported include urinary tract infection, nausea, dizziness, insomnia and upper respiratory tract infection.