Expanded Access Study Amifampridine Phosphate in Lambert-Eaton Myasthenic Syndrome (LEMS),Congenital Myasthenic Syndrome

This multicenter, expanded access study was designed to allow EAP-001 Investigators, neuromuscular specialists, and neurologists access to amifampridine phosphate therapy for their patients with LEMS, CMS, or downbeat nystagmus until such time the product became commercially available for these specific indications or development of the product for the indication was terminated. Given that these are chronic conditions, this study obtained some long-term safety data by evaluating Adverse Events, physical exams, vital signs, standard safety laboratory tests (chemistry, hematology, and urinalysis), pregnancy testing (if applicable) and abnormal ECG findings, where each of these data/measures were performed as part of a routine standard of care treatment provided by the Principal Investigator or the patient's personal physician(s) (i.e., could be performed by a different physician not involved in the treatment of neuromuscular disease).

Planned -100 sites in US and up to 200 patients. Actual- 50 sites activated and 200 patients enrolled.

Patients were seen at screening/baseline, Day 1 and at least once per year at the PIs discretion. With the COVID-19 Pandemic, telehealth visits were allowed and assessments that could be completed via remote telehealth visits were performed via phone or videoconference. Follow-up visits included Physical exams, vital signs, standard safety laboratory tests (chemistry, hematology, and urinalysis), pregnancy testing (if applicable) and ECGs.

Patients were titrated to an optimal individualized dose of amifampridine phosphate based on Principal Investigator assessment of optimal neuromuscular benefit. In patients already taking amifampridine base, amifampridine phosphate was started at an equivalent or lower dose of amifampridine phosphate, at the Principal Investigator's discretion. Therapeutic doses were to range from 10 to 80 mg, divided into doses taken two (2) to four (4) times per day, with a maximum single dose of 20 mg. For upward titration, amifampridine phosphate could be increased by 10 mg increments every four (4) to five (5) days to a maximum of 80 mg per day (ages >16 years), and to a maximum of 60 mg (ages 2 to 16 years) based on optimal neuromuscular benefit and at the discretion of the Principal Investigator. If needed, titration could occur in 5 mg/dose and per day increments. Drug was shipped to the clinic for the first dose ( Day 1) and subsequent shipments were sent to the patients home by a specialty pharmacy.

In addition to amifampridine phosphate, patients received best supportive care (BSC) treatment as determined by the Principal Investigator using concomitant medications permitted by protocol, including selected oral immunosuppressant's (i.e., prednisone or other corticosteroids, azathioprine, mycophenolate) and peripherally acting cholinesterase inhibitors (e.g., pyridostigmine). Changes to BSC could be made at the Principal Investigator's discretion, as long as prohibited concomitant medications were not used.

Firdapse® was approved for adult patients with LEMS in November 2018 and approved for pediatric patients with LEMS ages 6 years and older in September 2022. The indications for CMS and DBN were not pursued.