Phase 2 Trial of Amifampridine in SMA Type 3 Patients Fully Enrolled

Marisa Wexler MS avatar

by Marisa Wexler MS |

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amifampridine study

A clinical trial testing oral amifampridine phosphate in people with spinal muscular atrophy (SMA) type 3 who are able to walk is fully enrolled, Catalyst Pharmaceuticals announced in a press release.

Marketed under the brand name Firdapse, amifampridine phosphate is approved in the U.S. and the EU to treat Lambert-Eaton myasthenic syndrome (LEMS), a rare autoimmune disease in which the immune system attacks the nerve cells that control muscle movement.

The medication works by increasing the release of acetylcholine from nerve cells. Acetylcholine is a neurotransmitter — a signaling molecule that nerve cells use to communicate with each other and with muscle cells, controlling their movement. Multiple clinical trials have shown that amifampridine phosphate can improve muscle function in people with LEMS.

Amifampridine phosphate was originally developed by BioMarin Pharmaceuticals; Catalyst has owned licensing rights for its development and commercialization in North America since 2012.

Catalyst is now sponsoring a proof-of-concept Phase 2 trial (NCT03781479) evaluating the medication in ambulatory type 3 patients. It is believed that amifampridine phosphate may be beneficial for SMA because — in both animal models of the disease and in patients — there are abnormalities at the neuromuscular junction, the point where nerve cells communicate with muscle cells, which this medication may help to normalize.

The two-month trial is a placebo-controlled outpatient study of the oral medication’s safety, tolerability, and efficacy.

A total of 12 patients, ages 6 to 50, were enrolled at sites in Italy and Serbia. None have been treated with Spinraza (nusinersen, by Biogen), approved to treat all types of SMA.

Participants are randomly assigned to either amifampridine phosphate — taken as 10 mg tablets, with total doses ranging from 30 to 80 mg per day — or to placebo tablets for four weeks. The trial has a crossover design, meaning that patients initially given amifampridine phosphate will cross to placebo, and vice-versa, during the course of this study.

Treatment efficacy will be determined through the change, from the study’s start to the end of treatment periods, in scores on the Hammersmith Functional Motor Scale Expanded (HFMSE), a common evaluation of motor function.