A Phase 3 Study of Amifampridine Phosphate in Patients With Lambert Eaton Myasthenic Syndrome (LEMS)

Inclusion Criteria: Individuals eligible to participate in this study must meet all of the following inclusion criteria: * ≥18 years of age * Confirmed diagnosis of LEMS * Normal respiratory function * Normal swallowing function * If receiving peripherally acting cholinesterase inhibitors a stable dose is required for at least 7 days prior to Screening. * If receiving oral immunosuppressants a stable dose is required for at least 90 days prior to Screening. * Negative pregnancy test for females of childbearing potential * If sexually active, willing to use 2 acceptable methods of contraception * Willing to perform all study procedures as physically possible. * Willing and able to provide written informed consent after the nature of the study has been explained and prior to the start of any research-related procedures. Exclusion Criteria: Individuals who meet any of the following exclusion criteria are not eligible to participate in the study: * History of epilepsy or seizure. * Known active brain metastasis. * Use of Fampridine (4-aminopyridine), and any form of 3,4-diaminopyridine other than the IP provided, such as amifampridine base or Firdapse, during the study. * Use of medications known to lower the epileptic threshold within 7 days or 5 half-lives. * Use of medications which inhibit neuromuscular junction function within 7 days or 5 half-lives. * Use of IVIG, plasmapheresis (plasma exchange), or immunoadsorption within 90 days * Use of guanidine hydrochloride within…