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 7 days

   - Use of rituximab within 12 months

   - History of drug allergy to any pyridine-containing substances or any amifampridine
   phosphate excipient(s).

   - Use of any other investigational productwithin 30 days

   - Treatment with a concomitant medication that prolongs the QT/QTc interval within 7
   days or 5 half-lives.

   - Treatment with sultopride
   (4-amino-N-[(1-ethylpyrrolidin-2-yl)methyl]-5-ethylsulfonyl-2-methoxybenzamide) within
   7 days.

   - An abnormal electrocardiogram (ECG).

   - Documented history of arrhythmias.

   - History of additional risk factors for torsade de pointes.

   - Breastfeeding or pregnant or planning to become pregnant (self or partner) at any time
   during the study.

   - Likely or expected to require treatment for cancer within 3 months (90 days) after
   entering.

   - History of severe renal impairment or evidence of severe renal impairment

   - Any condition that places the patient at high risk of poor treatment compliance or of
   not completing the study.

   - History of uncontrolled asthma.