FDA OKs First Treatment for Rare Autoimmune Disorder


Amifampridine (Firdapse) is a first-in-class therapy for Lambert-Eaton myasthenic syndrome, a rare autoimmune disorder.

Officials with the FDA have approved amifampridine (Firdapse, Catalyst Pharmaceuticals) tablets for the treatment of Lambert-Eaton myasthenic syndrome (LEMS), a rare autoimmune disorder, according to a press release.1

The application was previously granted Priority Review and Breakthrough Therapy designations, as well as Orphan Drug designation, by the FDA. This approval, which marks the first for LEMS, addresses an unmet clinical need for the treatment of the disorder.

Amifampridine 10-mg tablets is an oral, nonspecific, voltage-dependent, potassium channel blocker that causes depolarization of a presynaptic membrane and slows or inhibits repolarization, according to Catalyst.2

“This FDA approval marks the arrival of a first-in-class therapy for a rare and devastating condition with limited treatment options,” Gary Ingenito, MD, PhD, chief medical officer and head of regulatory affairs at Catalyst, said in a statement.2 “We extend our deepest gratitude to the patients who participated in the Firdapse clinical trials and their families and caregivers who supported them.”

LEMS affects approximately 1 in 100,000 individuals in the United States, causing symptoms such as muscle weakness and fatigue, Catalyst stated.2 The disorder causes the body’s own immune system to attack the neuromuscular junction, disrupting the ability of nerve cells to send signals to muscle cells. LEMS commonly occurs in patients with cancer such as small cell lung cancer, where its onset precedes or coincides with the diagnosis of cancer, but may also be associated with other autoimmune diseases.1

The approval is based on data from 2 phase 3 clinical trials that together included 64 adult patients who received either amifampridine or a placebo. The studies measured the Quantitative Myasthenia Gravis score (a 13-item physician-rated categorical scale assessing muscle weakness) and the Subject Global Impression (a 7-point scale on which patients rated their overall impression of the effects of the study treatment on their physical well-being).1 Overall, the studies showed that patients receiving amifampridine experienced rapid, significant, and sustained improvements in muscle function compared with those treated with a placebo. Amifampridine also reduced weakness and fatigability.2

“There has been a long-standing need for a treatment for this rare disorder,” Billy Dunn, MD, director of the Division of Neurology Products in the FDA’s Center for Drug Evaluation and Research, said in a statement.1 “Patients with LEMS have significant weakness and fatigue that can often cause great difficulties with daily activities.”

Catalyst expects amifampridine to launch early in the first quarter of 2019, according to the release.2


  • FDA approves first treatment for Lambert-Eaton myasthenic syndrome, a rare autoimmune disorder [news release]. FDA’s website. https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm627093.htm. Accessed November 29, 2018.

  • FDA Approves Firdapse® (amifampridine) for the Treatment of Lambert-Eaton Myasthenic Syndrome (LEMS) [news release]. Catalyst’s website. https://ir.catalystpharma.com/news-releases/news-release-details/fda-approves-firdapser-amifampridine-treatment-lambert-eaton. Accessed November 29, 2018.

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